Common Cause Of Bloodstream Infections Research Articles

Strain Differences in Bloodstream and Skin Infection MRSA isolated between 2019-2021 in a Single Health System

Abstract S. aureus is a common cause of skin and soft tissue infections (SSTIs) and has recently become the most common cause of bloodstream infections (BSIs), but whether the strains causing these two clinical syndromes overlap has not been studied adequately. USA300/500 (clonal complex [CC] 8-ST8) and USA100 (CC5-ST5) have dominated among methicillin-resistant S. aureus (MRSA) strains in the U.S. since the early 2000s. We compared the genomes of unselected MRSA isolates from 131 SSTIs with those from 145 BSIs at a single U.S. center in overlapping periods in 2018-2021. CC8 MRSA was more common among SSTIs and CC5 was more common among BSIs, consistent with prior literature. Based on clustering genomes with a threshold of 15 single nucleotide polymorphisms (SNPs), we identified clusters limited to SSTI patients and separate clusters exclusively comprising BSI patients. However, we additionally identified eight clusters that included at least one SSTI and one BSI isolate. This suggests that virulent MRSA strains are transmitted from person-to-person locally in the healthcare setting or the community and that single lineages are often capable of causing both SSTIs and BSIs.

Bloodstream Infections in Pediatric Oncology Patients: Bacterial Pathogen Distribution and Antimicrobial Susceptibility at the University Hospital Centre Zagreb, Croatia-A 5-Year Analysis.

The epidemiology of bacterial pathogens causing bloodstream infections (BSIs) in pediatric hematology/oncology patients is changing and resistance to antimicrobial agents is globally spread. We retrospectively assessed demographic, clinical, and microbiologic data of BSIs during a 5-year period at a pediatric hematology/oncology unit from January 1, 2017, to December 31, 2021, at the University Hospital Centre Zagreb, Zagreb, Croatia. In 66 pediatric patients with malignancies, 93 BSI episodes were registered and 97 bacterial isolates were cultured. The Gram-positive versus Gram-negative ratio was 67 (69.1%) versus 30 (30.9%). Coagulase-negative staphylococci (48; 49.6%) were the most frequent isolates, followed by Enterobacterales (17; 17.5%) and Staphylococcus aureus (6; 6.2%). Multidrug resistance isolates included extended spectrum β-lactamase producers (n=3). Resistance rates to piperacillin/tazobactam, cefepime, and meropenem in Gram-negative isolates were 15.4%, 14.3%, and 0.0%, respectively. Gram-positive bacteria are the most common cause of BSI in our patients. Resistance rates to piperacillin/tazobactam and cefepime in Gram-negative isolates make meropenem a better choice for empirical antimicrobial treatment. As national and hospital data may differ, the surveillance of pathogen distribution and antimicrobial susceptibility in pediatric hematology/oncology wards is necessary to adjust empirical treatment accordingly.

620. Development and Validation of a Novel qPCR Assay for Differentiation of Common Candida Pathogens including C. auris

Abstract Background Candida is a common asymptomatic fungal colonizer of humans. Of the 200+ total species in the genus Candida, only a few are known to cause infection. The most common are C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. krusei, and C. auris. In the USA, candidemia is the fourth most common cause of bloodstream infections in hospitalized patients. Although antifungal medication can treat candidemia, mortality rates remain between 30 and 60%. Eurofins Viracor has developed a qPCR assay that will qualitatively detect and differentiate any of the 6 previously listed Candida species in whole blood. Speciation is critical for treatment due to variable drug susceptibility among different species, particularly C. auris due to its multi-drug resistance. Methods Multiple primer/probe mixes were designed around and within the ITS1, 5.8s, ITS2, and 28s ribosomal subunit regions in each of the six Candida target species. The 5.8s and 28s regions are heavily conserved, while the ITS regions are highly divergent and used to differentiate species. After optimization, the six primer/probe mixes were partially multiplexed resulting in four mixes covering all species. DNA was extracted from human blood spiked with viable Candida using the MagMAX™ DNA Multi-Sample Ultra 2.0 Kit, and eluates were amplified using the Applied Biosystems™ 7500 Fast platform. Results Each assay met all validation acceptance criteria and demonstrated excellent accuracy, precision, linearity and dynamic range, and sensitivity. 32 non-Candida fungal and bacterial pathogens that commonly cause bloodstream infections were used to assess specificity. All specificity samples were negative for all Candida targets. To assess accuracy, 75 of 75 Candida samples representing all six species across a range of concentrations were tested and correctly identified. 24 of 25 known-negative samples were negative, with one positive C. glabrata CT result observed just below the cutoff. Conclusion Traditional blood culture methods for Candida species identification can be too time consuming for a quickly progressing infection. The Candida qPCR assay described here not only detects an infection faster but provides accurate speciation allowing for rapid and targeted antifungal treatment options for the patient. Disclosures Clayton Thomas, BS in Biology, Eurofins Viracor: Employee James Grantham, n/a, Eurofins Viracor: Employee Emily Lute, n/a, Eurofins Viracor: Employee Jerod Davidson, n/a, Eurofins Viracor: Employee Scott Cowden, MS, MB ASCP(CM), Eurofins Viracor: Employee Jamie Nutt, n/a, Eurofins Viracor: Employee

Risk Factors and Outcome of Gram-Negative Bloodstream Infection in Living-Donor Renal Transplant Recipients: A Case-Control Study From Pakistan.

Gram-negative rods are the most common cause of bloodstream infection in renal transplant recipients. Acute rejection, urologic abnormalities, and ureteral stents are risk factors. Graft dysfunction is independently associated with gram-negative rod bloodstream infection. Our aim is to investigate the incidence, risk factors, and outcome among living donor renal transplant recipients from Pakistan. In this case-control study, we reviewed the medical records until June 2021 of renal transplant recipients seen from 2015 to 2019 for gram negative bacteremia. For every case, controls were matched by age, date of transplant, and sex. Demographics, risk factors, graft function, and mortality were compared. Clinical features, immunosuppression, source of blood stream infection, and microbiology were noted in cases. Of 1677 renal transplant recipients, 44 developed gram negative bacteremia. The incidence was 5.9 per 1000 person-years. Median time since transplant was 5 months. The most common source was urinary tract infection. On univariate analysis, antithymocyte globulin, urinary tract infection, and recurrent urinary tract infections were associated with gram negative bacteremia. On multivariate analysis, urinary tract infection (adjusted odds ratio = 3.46; 95% CI, 1.27-9.37) and recurrent urinary tract infections (adjusted odds ratio = 4.03; 95% CI, 1.15-14.15) were significant risk factors. We found no difference in 30-day mortality and estimated glomerular filtration rate on last follow-up between cases and controls. Kaplan-Meier survival curves showed significant differences in graft survival in patients with gram negative bacteremia. Escherichia coli was the most common organism, with 75% ceftriaxone and 13% imipenem resistance. The most significant risk factor for gram negative rod bloodstream infection was recurrent urinary tract infections. Timely treatment and prevention of recurrent urinary tract infections areimperative for prevention of gram negative bacteremia.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections.

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Staphylococcus aureus bloodstream infection in a Chinese tertiary-care hospital: A single-center retrospective study.

To the Editor: Despite major advances in medical care, the incidence and mortality of bloodstream infection (BSI) remain high, which is still a global public health challenge. BSI can be caused by various microorganisms, and the most common organisms are Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus (S. aureus), according to the China Antimicrobial Surveillance Network (CHINET).[1]S. aureus is the third most common cause of BSI, which is associated with short-term mortality rates of 15–30%, long-term excess mortality, and increased healthcare costs. At present, there are many studies on Gram-negative bacteremia but relatively few on S. aureus bloodstream infection (SA-BSI), especially in China. With the occurrence of new treatments and clinical conditions, such as aging and extensive antibiotic resistance, it is necessary to reanalyze the clinical characteristics and prognosis of SA-BSI. This single-center retrospective cohort study was conducted in the Second Affiliated Hospital, Zhejiang University School of Medicine. The Ethics Committee of our hospital granted ethics approval (No. 2019-194) for the present study. The requirement for signed informed consent was exempted because of the retrospective nature of the study. Furthermore, a statement of permission from patients for submission was not needed, as no personal information was included. During the six-year study period (2013–2018), a total of 1174 blood culture specimens positive for S. aureus were initially included. Four patients aged <18 years, 54 patients with nonpathogenic bacteria, 45 patients with incomplete or missing data, and nine patients lost to follow-up were excluded. Finally, 349 patients were included. The patients were followed for at least 28 days after the onset of BSI. According to 28-day mortality, the patients were divided into nonsurvival (61 cases) and survival groups (288 cases) [Figure 1A].Figure 1: (A) Flowchart of study participant enrollment with blood culture specimens positive for Staphylococcus aureus. (B) Age and sex distributions of patients with SA-BSI. (C) Distribution proportions of MRSA and MSSA from 2013 to 2018. (D) Forest plot of the results of the univariate and multivariate logistic regression analyses for prognostic factors for death in patients with SA-BSI. APACHE: Acute Physiology and Chronic Health Evaluation; COPD: Chronic obstructive pulmonary disorder; CVC: Central venous catheter; ICU: Intensive care unit; MRSA: Methicillin-resistant Staphylococcus aureus; MSSA: Methicillin-sensitive Staphylococcus aureus; SA-BSI: Staphylococcus aureus bloodstream infections; SOFA: Sequential Organ Failure Assessment.Using a self-created Excel sheet, the clinical data of cases were collected through the hospital identification of blood culture-positive specimens for S. aureus provided by the microbiology laboratory. We recorded demographic and microbiological data, sensitivity to antibiotics, and clinical treatment and evaluation data (the Sequential Organ Failure Assessment [SOFA] score, the Acute Physiology and Chronic Health Evaluation [APACHE] II score in the first 24 h following the onset of BSI) by reviewing electronic medical records. To ensure data quality, a homogeneous data collection form was carefully prepared before data collection. Additionally, two days of training were provided to data collectors and supervisors. Furthermore, the supervisor and principal investigators supervised the data collectors throughout the entire data collection period. After data collection was completed, the supervisor organized and carefully cleaned the data and then entered the data into Statistical Package for Social Sciences (SPSS, 26.0, IBM Corp., Armonk, NY, USA) for statistical analysis. Variables with P <0.05 in the univariate analysis were entered into the multivariable model. Continuous variables were treated as dichotomous variables based on Youden index. Multivariate analysis was performed with logistic regression to identify independent prognostic factors for death in patients with SA-BSI. A two-tailed P <0.05 was considered statistically significant. The demographics showed that the median age was 59.0 (45.5–68.0) years, and 69.6% (243/349) were male [Supplementary Table 1, https://links.lww.com/CM9/B557]. The age distribution was left-skewed, with a peak incidence in the group of 60–69 years. In addition, the proportion of men was significantly higher than that of women in all age groups except for those >90 years old [Figure 1B]. Patients in the nonsurvivor group were significantly older than survivor group (median, 65.0 vs. 58.0 years, P = 0.005). In terms of comorbidities, significantly higher percentages of chronic obstructive pulmonary disease (COPD) and severe asthma were observed in the nonsurvivor group than in the survivor group (6.6% [4/61] vs. 1.0% [3/288], P = 0.005). In comparison with survivors, nonsurvivors had a more severe condition, evidenced by a higher APACHE II score (median, 24 vs. 11, P <0.001), a higher SOFA score (median, 12 vs. 3, P <0.001), and had a higher rate of intensive care unit (ICU) admission (85.2% [52/61] vs. 27.4% [79/288], P <0.001), indwelling central venous catheter placement (73.8% [45/61] vs. 42.4% [122/288], P <0.001), and invasive mechanical ventilation (82.0% [50/61] vs. 34.4% [99/288], P <0.001). Compared with those in survivors, the proportions of polymicrobial SA-BSI (26.2% [16/61] vs. 13.2% [38/288], P = 0.011), methicillin-resistant S. aureus (MRSA) (82.0% [50/61] vs. 57.3% [165/288], P <0.001), and septic shock (50.8% [31/61] vs. 1.4% [4/288], P <0.001) in nonsurvivors were higher. In comparison with survivors, nonsurvivors had a lower hematocrit (median [%], 26.8 vs. 29.1, P = 0.009), a lower platelet count (median [109/L], 85 vs. 187, P <0.001), a lower albumin level (mean [g/L], 27.73 vs. 29.95, P =0.005), and worse liver and kidney function. In addition, the absolute neutrophil count (ANC) and procalcitonin (PCT) level were significantly higher in nonsurvivors than in survivors [Supplementary Table 2, https://links.lww.com/CM9/B557]. In comparison with those in survivors, the ratios of resistance of S. aureus to ciprofloxacin, levofloxacin, and moxifloxacin were significantly higher in nonsurvivors [Supplementary Table 3, https://links.lww.com/CM9/B557]. Of note, MRSA occurred significantly more frequently in nonsurvivors than in survivors (82% [50/61] vs. 57.3% [165/288], P <0.001). The proportion of MRSA had a significant downwards trend from 70.8% (46/65) in 2014 to 43.6% (24/55) in 2018 [Figure 1C]. The main source of SA-BSI was pneumonia (26.6%, 93/349), followed by skin/soft tissue infection (24.4%, 85/349). Compared with survivors, nonsurvivors had higher rates of pneumonia (37.7% [23/61] vs. 24.3% [70/288], P =0.032) and intra-abdominal infection (27.9% [17/61] vs. 8.7% [25/288], P <0.001) [Supplementary Table 4, https://links.lww.com/CM9/B557]. In terms of infection control, there was no significant difference in the rates of drainage of the infection source and removal of contaminated sutures between the two groups. We also did not observe any differences in mortality between the survivors and nonsurvivors based on antibiotic exposure (P >0.05). For targeted treatment, 189 (54.2%) patients received glycopeptides (vancomycin or teicoplanin), 25 (7.2%) patients received piperacillin/tazobactam, 58 (16.6%) patients received linezolid, 26 (7.4%) patients received tigecycline, and 43 (12.3%) patients received fluoroquinolone (levofloxacin or moxifloxacin), but there was no statistical significance between the two groups. In addition, a total of 8.3% (29/349) of patients did not receive appropriate therapy within 24 h after the release of antibiotic susceptibility results, but there was no difference between the two groups (6.6% [4/61] vs. 8.7% [25/288], P =0.585) [Supplementary Table 4, https://links.lww.com/CM9/B557]. The multivariate logistic regression model showed that the independent prognostic factors for 28-day mortality were age >67 years (adjusted odds ratio [aOR], 4.46; 95% confidence interval [CI], 1.18–16.88), an APACHE II score >17 (aOR, 42.47; 95% CI, 8.11–222.48), a SOFA score >7 (aOR, 8.01; 95% CI, 2.06–31.12), septic shock (aOR, 9.86; 95% CI, 1.18–82.37), and albumin <30 g/L (aOR, 5.14; 95% CI, 1.34–19.71) [Figure 1D]. There is still some controversy about the relationship between polymicrobial BSI and mortality in ICU patients. A study by Park et al[2] showed that polymicrobial SA-BSI was an independent prognostic factor for bacteremia-related mortality, which is not consistent with our current study. In their study, patients with polymicrobial SA-BSI were significantly less likely to receive appropriate empirical antibiotics than those with monomicrobial SA-BSI; 25% were infected with S. aureus plus a Gram-positive pathogen; and evidence did not shown that coinfection with Gram-positive pathogens resulted in death faster than coinfection with Gram-negative organisms. In our study, appropriate antibiotic therapy did not differ between the two groups, and the proportion of Gram-positive coinfections (36.1% [22/61]) with S. aureus was significantly higher than that in the study by Park et al[2] (25%). Therefore, we speculate that fatal polymicrobial SA-BSI is associated with a more severe condition and is not a direct independent prognostic factor of death for patients with SA-BSI. The incidence of SA-BSI has generally been reported to be higher in males than in females, while some studies have reported increased mortality in females.[3] We found that most of the proportions of infections in males in the different age groups were generally higher than those in females [Figure 1B], and the mortality rates of SA-BSI in men and women were 19.3% [47/243] and 13.2% [14/106], respectively. We did not detect any sex difference in outcomes. We found that the age distribution was left-skewed, with a peak incidence in the 60–69 years group [Figure 1B], and age >67 years was an independent prognostic factor for death in patients with SA-BSI. This might be related to more comorbidities in older patients. As described in many studies,[3] age was the strongest independent predictor of mortality, and the mortality rate increased from 6% in young individuals (<15 years old) to 57% in adults >85 years of age according to Lamagni et al.[4] Therefore, clinicians should pay more attention to the age of patients with SA-BSI than to their sex. In our current study, the proportion of MRSA had a significant downwards trend from 70.8% (46/65) in 2014 to 43.6% (24/55) in 2018, which is in line with the MRSA trend reported by CHINET,[3] probably as a result of a greater understanding of SA-BSI management. Although MRSA was associated with mortality, it was not an independent prognostic factor for death in patients with SA-BSI. This might be related to a decrease in the pathogenicity of MRSA in recent years, which is indirectly refected by the decrease in the detection rate of MRSA in our hospital in recent years. In addition, we found that septic shock was an independent prognostic factor for death in patients with SA-BSI. In conclusion, SA-BSI was characterized by a peak incidence in 60–69 years old, and pneumonia and skin/soft tissue infection as the main infection sources. There were several independent prognostic factors for 28-day mortality of SA-BSI patients, including age >67 years, an APACHE II score >17, a SOFA score >7, septic shock, and albumin <30 g/L. By contrast, MRSA and polymicrobial BSI were associated with 28-day mortality, but not independent prognostic factors. To properly manage SA-BSI, clinicians should be aware of patients with one or more of the abovementioned independent prognostic factors. Funding This work was supported in part by grants from the National Natural Science Foundation of China (No. 81901941), Natural Science Foundation of Zhejiang Province (No. LY19H150007; No. LY20H150008), Medical and Health Research Program of Zhejiang Province (No. 2019RC038; No. 2018KY427; No. 2022KY1396, No. 2022KY1398). Conflicts of interest None.

Comparison of Oral and Intravenous Definitive Antibiotic Therapy for Beta-Hemolytic Streptococcus Species Bloodstream Infections from Soft Tissue Sources: a Propensity Score-Matched Analysis.

Beta-hemolytic streptococci are common causes of bloodstream infection (BSI). There is emerging data regarding oral antibiotics for BSI but limited for beta-hemolytic streptococcal BSI. We conducted a retrospective study of adults with beta-hemolytic streptococcal BSI from a primary skin/soft tissue source from 2015 to 2020. Patients transitioned to oral antibiotics within 7 days of treatment initiation were compared to those who continued intravenous therapy, after propensity score matching. The primary outcome was 30-day treatment failure (composite of mortality, infection relapse, and hospital readmission). A prespecified 10% noninferiority margin was used for the primary outcome. We identified 66 matched pairs of patients treated with oral and intravenous antibiotics as definitive therapy. Based on an absolute difference in 30-day treatment failure of 13.6% (95% confidence interval 2.4 to 24.8%), the noninferiority of oral therapy was not confirmed (P = 0.741); on the contrary, the superiority of intravenous antibiotics is suggested by this difference. Acute kidney injury occurred in two patients who received intravenous treatment and zero who received oral therapy. No patients experienced deep vein thrombosis or other vascular complications related to treatment. In patients treated for beta-hemolytic streptococcal BSI, those who transitioned to oral antibiotics by day 7 showed higher rates of 30-day treatment failure than propensity-matched patients. This difference may have been driven by underdosing of oral therapy. Further investigation into optimal antibiotic choice, route, and dosing for definitive therapy of BSI is needed.

Streptococcus dysgalactiae Bloodstream Infections, Norway, 1999-2021.

Streptococcus dysgalactiae increasingly is recognized as a pathogen of concern for human health. However, longitudinal surveillance data describing temporal trends of S. dysgalactiae are scarce. We retrospectively identified all β-hemolytic streptococcal bloodstream infections reported in Bergen, in western Norway, during 1999-2021. To explore S. dysgalactiae disease burden in a broader context, we mapped the incidence of all microbial species causing bloodstream infections during 2012-2021. We found S. dysgalactiae incidence rates substantially increased during the study period; by 2021, S. dysgalactiae was the fifth most common pathogen causing bloodstream infections in our region. We noted genotypic shifts and found that the rising trend was related in part to the introduction and expansion of the stG62647 emm-type. S. dysgalactiae is among the most common causes of bloodstream infections in western Norway, and increased surveillance and unambiguous species identification are needed to monitor the disease burden attributable to this pathogen.

Bloodstream infection and ventilator-associated pneumonia in patients with coronavirus disease 2019 (COVID-19) supported by extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) has been widely used in the care of patients with respiratory failure from coronavirus disease 2019 (COVID-19). We characterized bloodstream infections (BSIs) and ventilator-associated pneumonias (VAPs) in COVID-19 patients supported with ECMO, and we investigated their impact on patient outcomes. Retrospective cohort study from March 1, 2020, to June 30, 2021. Academic tertiary-care referral center. Consecutive adult patients admitted for COVID-19 who received ECMO. We identified BSIs and VAPs and described their epidemiology and microbiology. Cumulative antimicrobial use and the specific management of BSIs were determined. Multivariate time-dependent Cox proportional hazards models were constructed to evaluate the impact of BSIs and VAPs on mortality, controlling for age, receipt of COVID-19-specific therapeutics, and new renal replacement therapy. We identified 136 patients who received ECMO for COVID-19 pneumonia during the study period. BSIs and VAPs occurred in 81 patients (59.6%) and 93 patients (68.4%), respectively. The incidence of BSIs was 29.5 per 1,000 ECMO days and increased with duration of ECMO cannulation. Enterococci, Enterobacterales, and Staphylococcus aureus were the most common causes of BSIs, whereas S. aureus, Klebsiella species, and Pseudomonas aeruginosa comprised the majority of VAPs. Mean antibiotic use comprised 1,031 days of therapy per 1,000 ECMO days (SD, 496). We did not detect an association between BSIs or VAPs and mortality. BSIs and VAPs are common in COVID-19 ECMO-supported patients. Efforts to optimize their diagnosis, prevention, and management should be prioritized.

181. Impact of Rapid Diagnostic Technology on Patients with Candidemia

Abstract Background Candida spp. are the fourth most common cause of bloodstream infections (BSI) in the United States and have an associated mortality rate of 19-40.5%. Mortality rates are further impacted by delay in time to adequate antifungal therapy, historically due to delayed time to identification on culture. The utilization of rapid diagnostic technology (RDT) has been effective in timely identification of bacterial pathogens causing BSI, but RDT for fungal organisms has demonstrated mixed results. At AdventHealth Central Florida Division South (CFD-S), pharmacists provide 24-hour coverage for real-time notification of all positive blood culture results. The objective of this study was to evaluate the clinical impact of the GenMark ePlex Blood Culture Identification Panels (BCID) fungal pathogen (FP) panel paired with 24/7, pharmacist-driven response in patients with candidemia.  Methods This multi-site, pre/post, retrospective chart review included adult patients admitted to CFD-S with at least one positive blood culture with Candida spp. from June 2019 through May 2020 (pre-RDT), and August 2020 through July 2021 (post-RDT). Patients receiving systemic antifungal prophylaxis, with known candidiasis at time of index RDT result, or who discharged prior to culture positivity were excluded. The primary outcome was time to effective antifungal therapy in patients with candidemia. Results A total of 200 patients were included in the study (100 pre-RDT and 100 post-RDT). Overall, patients had a median age of 61 years and 50% were male. Patient characteristics are summarized in Table 1; median APACHEII score differed by three points (13.5 vs. 16.5). Time to effective therapy was similar between groups (39.8 vs. 38.5 hours, p=0.217). There was no difference in secondary outcomes (Table 2) other than ICU length of stay (2.5 vs. 6.0 days, p=0.033) and all-cause in-hospital mortality (15% vs. 30%, p=0.011). Conclusion Pharmacist-driven, real-time response to RDT did not significantly impact time to effective antifungal therapy in patients with candidemia. Higher rate of in-hospital mortality was likely a reflection of increased severity of illness in the post-RDT group. Disclosures Amy L. Carr, PharmD, BCIDP, Shionogi: Advisory Board.

Clinical and genomic analysis of virulence-related genes in bloodstream infections caused by Acinetobacter baumannii

ABSTRACT Acinetobacter baumannii has emerged as a common cause of bloodstream infections, which is associated with high mortality and long periods of hospitalization. To advance the medical care of our patients, the study was designed to identify microbial characteristics associated with poor clinical outcomes. A collection of 32 A. baumannii bloodstream isolates with diverse genetic backgrounds (as determined by multilocus sequence typing) was studied. These isolates were recovered by unique patients (18 males, 14 females; age range: 17 days to 87 years) between 2011 and 2018. A sequential screening approach (cross-referencing analyses using different endpoints) was used to identify isolates with the best correlation between bacterial virulence and clinical prognosis. Isolates associated with more rapid in vitro growth rate, shorter median survival time in pre-clinical infection models, and hospital mortality were selected as candidates for high virulence, while those with opposite characteristics were selected as controls with low virulence. Whole genome sequencing was undertaken in the most promising clinical isolates. We found five virulence genes (beta-hemolysin/cytolysin, Cpi-1a + Cpi-1 (SPI-1 like), enhanced entry proteins, FbpABC, Paa) and 1 secretory system (T6SS) only present in a highly virulent isolate (AB23), compared to a low virulence control isolate (AB6). These genetic elements could be associated with the poor prognosis of A. baumannii bacteraemia and further investigations are warranted.

EPIDEMIOLOGY, PREDISPOSING FACTORS AND OUTCOME OF STAPHYLOCOCCUS AUREUS BACTEREMIA IN NEUTROPENIC PATIENTS

Staphylococcus aureus is a common cause of bloodstream infection in neutropenic patients. We analyzed trends in incidence, epidemiology, predisposing factors and outcome of S. aureus bacteremia (SAB) in febrile neutropenic patients. We reviewed a database of febrile neutropenia at a single institution in Brazil in a 30-year period (January 1991 to December 2020). We divided in 3 periods: 1991-1994 (period 1), 2001-2010 (period 2) and 2011-2020 (period 3), and looked at incidence rates, risk factors and mortality. Risk factors and prognostic factors were evaluated by univariate (Fisher or Chi-square for categorical variables and Wilcoxon test for continuous variables) and multivariate (logistic regression) analysis. We diagnosed 62 (3%) episodes of SAB in 2,243 episodes of febrile neutropenia, 23 (38%) of which were caused by methicillin-resistant S. aureus (MRSA). The incidence of SAB per 1,000 days of neutropenia was 1.57, 2.53 and 1.50 in periods 1, 2 and 3, respectively (p > 0.05), and of MRSA was 0.49, 0.84 and 1.07, respectively (p > 0.05). Most infections (70%) were diagnosed in the first day of fever and the clinical presentation were skin infection (19%), catheter-related infection (14%) and pneumonia (3%). Complications like endocarditis or osteomyelitis were not observed. The only factor associated with S. aureus bacteremia by multivariate analysis was cellulitis at site of catheter exit site or tunnel on day 1 of fever (odds ratio [OR] 4.34, 95% confidence interval [CI] 2.05 – 9.16), whereas quinolone prophylaxis was protective (OR 0.37, 95% CI 0.18 - 0.74). The crude mortality of SAB was 30.6%, compared 13.8% in patients without this infection (p < 0.001). However, early mortality (within 3 days of start of empiric antibiotic therapy) was not significantly different (4.8% vs. 1.9%, p = 0.08). The mortality with MRSA was higher than with methicillin-susceptible S. aureus (47.8% vs. 13.9%, p < 0.001), but no difference was found regarding early mortality (5.0 vs 1.7%, p = 0.27). Among various predictors of death during febrile neutropenia MRSA bacteremia (but not methicillin-sensitive) was associated with an increased risk of death by multivariate analysis. The median time from febrile neutropenia to death in MRSA episodes was 19 days. The incidence of SAB over the period remained stable. Complication of SAB were not common. Although the crude mortality was higher with SAB (including MRSA), it was not associated with early deaths, thus not demanding anti-staphylococcal coverage in the first day of febrile neutropenia. MRSA bacteremia was associated with increased risk of death, with most deaths occurring after 2 weeks of febrile neutropenia.

Assessment of the antifungal susceptibility profile and virulence factors of non-albicans candida species obtained from the infection of the bloodstream

Background: Earlier the fungal infection spectrum was considered to be only restricted to mucocutaneous and cutaneous tissues. However, this consideration has now changed. The threatening rise in the incidence of invasive mycosis is seen recently. Despite advancements in diagnostic and therapeutic modalities, high mortality rates are linked to invasive mycosis. The most common cause of bloodstream infections is Candida spp. Among candida genus, the most pathogenic species is C. Albicans, recent literature data has shown the emergence of treatment-resistant, relatively uncommon, and unusual nonalbicans Candida (NAC) spp. Aim: The present study was conducted to assess the antifungal susceptibility profile and virulence factors of non-Albicans candida species obtained from the infection of the bloodstream.  Material and methods: The present study included blood culture isolates of nonalbicans Candida (NAC) spp. which were identified to species level using the standard mycological protocol. This NAC spp. were screened for virulence factors production including biofilm formation, hemolysin, and extracellular hydrolytic enzymes. Ezy MIC strip was used for assessing the antifungal susceptibility profile of these isolates.  Results: 100% (n=1) C. rugosa NAC spp. showed hemolysin production. In C. gulliermondii, 50% (n=1) subject showed phospholipase production and biofilm formation each. 

P8.016: Gram Negative Blood Stream Infection in Renal Transplant Recipients: Risk Factors and Outcome From a Transplant Center in Pakistan

Background: Gram-negative bacteremia (GNB) is a common cause of bloodstream infection in renal transplant recipients (RTR). The risk factors are cytomegalovirus infection (CMV), pre-transplant dialysis, acute rejection, urological abnormalities, and ureteral stent. The mortality rate is 2.5 to 11%. Considering the huge impact on morbidity and mortality, our aim is to analyze the characteristics and outcomes of GNB in RTRs. Methods: A case-control study at Sindh Institute of Urology and Transplantation (SIUT), Karachi, Pakistan. The files of all renal transplant recipients who had documented GNB from January 2015 to December 2017 were reviewed till December 2020. The controls were matched with age, sex, and date of transplant. The first episode of GNB was taken. Clinical features, received anti-thymocyte globulin (ATG) or solumederol and cytomegalovirus infection (CMV) 90 days pre or post bacteremia, recurrent urinary tract infections (UTI), source of bacteremia and microbiology, all-cause mortality at day 28 and graft function at the last follow up were noted. Results: Out of 1009 RTR, 33 (3.3%) episodes of GNB occurred. The mean age was 30±11.85years, 61% males. Around 48% developed bacteremia within 6 months post-transplant. The most common source was UTI (75.8%). Fever in 48% and only 39% had leukocytosis. Around 9% were admitted in the intensive care unit. E-coli was the most common organism (70%) (Table 1). Stone disease at the time of transplant was significantly associated with bacteremia (p=0.029). There was no difference in receiving ATG or solumeredol and CMV before bacteremia. A significant number of patients received solumeredol for rejection (p=0.035) and had CMV (p=0.044) within 90 days after bacteremia. Recurrent UTI is significantly associated with bacteremia (p<0.001). The graft function at the last follow-up (2 years) was significantly deranged in patients with bacteremia (p=0.0001). Conclusion: Gram-negative bacteremia was found in 3% of RTR and half of them developed within 6 months post-transplant. UTI was the most common source and recurrent UTI was significantly associated with bacteremia. The stone disease was the most significant risk factor. Patients develop rejection and CMV infection within 3 months post bacteremia. There was a significant graft dysfunction among patients with bacteremia at a mean follow-up of 2 years. We need to focus on the management of recurrent UTIs to prevent bacteremia and graft dysfunction in renal transplant recipients.

Molecular epidemiology and antimicrobial resistance phenotype of paediatric bloodstream infections caused by Gram-negative bacteria

BackgroundGram-negative organisms are common causes of bloodstream infection (BSI) during the neonatal period and early childhood. Whilst several large studies have characterised these isolates in adults, equivalent data (particularly incorporating whole genome sequencing) is lacking in the paediatric population.MethodsWe perform an epidemiological and sequencing based analysis of Gram-negative bloodstream infections (327 isolates (296 successfully sequenced) from 287 patients) in children <18 years old between 2008 and 2018 in Oxfordshire, UK.ResultsHere we show that the burden of infection lies predominantly in neonates and that most infections are caused by Escherichia coli, Klebsiella spp. and Enterobacter hormaechei. There is no evidence in our setting that the proportion of antimicrobial resistant isolates is increasing in the paediatric population although we identify some evidence of sub-breakpoint increases in gentamicin resistance. The population structure of E. coli BSI isolates in neonates and children mirrors that in adults with a predominance of STs 131/95/73/69 and the same proportions of O-antigen serotypes. In most cases in our setting there is no evidence of transmission/point-source acquisition and we demonstrate the utility of whole genome sequencing to refute a previously suspected outbreak.ConclusionsOur findings support continued use of current empirical treatment guidelines and suggest that O-antigen targeted vaccines may have a role in reducing the incidence of neonatal sepsis.

Molecular Determination of Virulence Factor Genes of Acinetobacter baumannii Isolates from Clinical Specimens

Acinetobacter baumannii is a gram negative coccobacilli present abundantly in nature, in soil and water. Acinetobacter baumannii is considered as a major cause of nosocomial infections affecting mainly ICU patients and other hospitalised patients. Both intrinsic and acquired antibiotic resistance of A. baumannii account for a significant cause of outbreaks. Significant levels of morbidity and mortality have been reported with outbreaks and common infections include ventilator associated pneumonia and bacteraemia. A.baumannii is also a common cause of bloodstream infections in the intensive care setting. Multiple virulence factors are required for the pathogenesis of infections by Gram negative bacteria including A. baumannii. Possession of specialized virulence genes enables pathogens to infect hosts efficiently. Virulence factors of A. baumannii were less identified compared to other Gram negative bacteria. Hence this study was done to identify the major virulence factor genes from the clinical isolates of multidrug resistant A. baumannii from a tertiary care hospital. A preliminary study was done to determine the prevalence of Acinetobacter infections in the region and then the isolates were subjected to determine the antibiotic sensitivity and to various molecular typing. Various clinical specimens like blood, urine, abscess, vaginal swab were analyzed and 15% of the isolates was confirmed and identified as to be resistant to carbapenems. A molecular typing was done to identify the genes conferring virulence factors. Presence of different genes like Bap, Omp A, EpsA, ptk, AdeG were screened from the isolates. :  , , , ,

The Relationship Between Antibiotic Agent and Mortality in Patients With Febrile Neutropenia due to Staphylococcal Bloodstream Infection: A Multicenter Cohort Study.

BackgroundMethicillin-susceptible Staphylococcus aureus (MSSA) is a common cause of bloodstream infection (BSI) in patients with febrile neutropenia, but treatment practices vary, and guidelines are not clear on the optimal regimen.MethodsWe conducted a multicenter retrospective cohort study of MSSA BSI in febrile neutropenia. We divided patients into 3 treatment groups: (1) broad-spectrum beta-lactams (ie, piperacillin-tazobactam, cefepime, meropenem); (2) narrow-spectrum beta-lactams (ie, cefazolin, oxacillin, nafcillin); and (3) combination beta-lactams (ie, both narrow- and broad-spectrum). We used multivariable logistic regression to compare 60-day mortality and bacteremia recurrence while adjusting for potential confounders.ResultsWe identified 889 patients with MSSA BSI, 128 of whom had neutropenia at the time of the index culture: median age 56 (interquartile range, 43–65) years and 76 (59%) male. Of those, 56 (44%) received broad-spectrum beta-lactams, 30 (23%) received narrow-spectrum beta-lactams, and 42 (33%) received combination therapy. After adjusting for covariates, including disease severity, combination therapy was associated with a significantly higher odds for 60-day all-cause mortality compared with broad spectrum beta-lactams (adjusted odds ratio [aOR], 3.39; 95% confidence interval [CI], 1.29–8.89; P = .013) and compared with narrow spectrum beta-lactams, although the latter was not statistically significant (aOR, 3.30; 95% CI, .80–13.61; P = .071).ConclusionsUse of combination beta-lactam therapy in patients with MSSA BSI and febrile neutropenia is associated with a higher mortality compared with treatment with broad-spectrum beta-lactam after adjusting for potential confounders. Patients in this study who transitioned to narrow-spectrum beta-lactam antibiotics did not have worse clinical outcomes compared with those who continued broad-spectrum beta-lactam therapy.

Medical microbiology

Candida species are the fourth most common cause of bloodstream infections and are the leading cause of invasive fungal infections among hospitalized patients [1]. Candidemia is a life-threatening fungal infection associated with a mortality rate of 38%; [2].The spectrum of candidemia has changed with the emergence of non- albicans Candida (NCAC) species, a strain with the threat of increased mortality especially in immunocompromised and severely ill patients [4]. It is very important to identify Candida to the species level to optimize the selection of the antifungal agent. More importantly, intrinsic and emerging resistance represents a major challenge for empirical, therapeutic and prophylactic strategies. Candida species have also been isolated from the respiratory tract, mouth, skin, ear and eye.  Candida is a true opportunistic pathogen that under certain circumstances is able to invade tissues normally resistant to infection.

Vaccination to Prevent Pseudomonas aeruginosa Bloodstream Infections.

The bacterium Pseudomonas aeruginosa (Pa) is ubiquitous in the environment and causes opportunistic infections in humans. Pa is increasingly becoming one of the most difficult to treat microorganisms due to its intrinsic and acquired resistance to multiple antibiotics. The World Health Organization estimates that at least 700,000 people die each year from drug resistant microbial infections and have listed Pa as one of three bacterial species for which there is the most critical need for the development of novel therapeutics. Pa is a common cause of bloodstream infections (BSI) and bacterial sepsis. With nearly 49 million sepsis cases and 11 million deaths worldwide, an effective vaccine against Pa could prevent the morbidity and mortality resulting from Pa BSI and lessen our dependence on antibiotics. We reviewed the current landscape of Pa vaccines in pre-clinical and clinical stages over the last two decades. It is readily apparent that Pa vaccine development efforts have been largely directed at the prevention of pulmonary infections, likely due to Pa’s devastating impact on individuals with cystic fibrosis. However, the increase in nosocomial infections, BSI-related sepsis, and the emergence of widespread antibiotic resistance have converged as a major threat to global public health. In this perspective, we draw attention to potential Pa vaccine candidates and encourage a renewed effort for prophylactic vaccine development to prevent drug-resistant Pa BSI.

Protein-conjugated microbubbles for the selective targeting of S. aureus biofilms

Staphylococcus aureus (S. aureus) is an important human pathogen and a common cause of bloodstream infection. The ability of S. aureus to form biofilms, particularly on medical devices, makes treatment difficult, as does its tendency to spread within the body and cause secondary foci of infection. Prolonged courses of intravenous antimicrobial treatment are usually required for serious S. aureus infections. This work investigates the in vitro attachment of microbubbles to S. aureus biofilms via a novel Affimer protein, AClfA1, which targets the clumping factor A (ClfA) virulence factor – a cell-wall anchored protein associated with surface attachment. Microbubbles (MBs) are micron-sized gas-filled bubbles encapsulated by a lipid, polymer, or protein monolayer or other surfactant-based material. Affimers are small (∼12 kDa) heat-stable binding proteins developed as replacements for antibodies. The binding kinetics of AClfA1 against S. aureus ClfA showed strong binding affinity (KD = 62 ± 3 nM). AClfA1 was then shown to bind S. aureus biofilms under flow conditions both as a free ligand and when bound to microparticles (polymer beads or microbubbles). Microbubbles functionalized with AClfA1 demonstrated an 8-fold increase in binding compared to microbubbles functionalized with an identical Affimer scaffold but lacking the recognition groups. Bound MBs were able to withstand flow rates of 250 μL/min. Finally, ultrasound was applied to burst the biofilm bound MBs to determine whether this would lead to biofilm biomass loss or cell death. Application of a 2.25 MHz ultrasound profile (with a peak negative pressure of 0.8 MPa and consisting of a 22-cycle sine wave, at a pulse repetition rate of 10 kHz) for 2 s to a biofilm decorated with targeted MBs, led to a 25% increase in biomass loss and a concomitant 8% increase in dead cell count. The results of this work show that Affimers can be developed to target S. aureus biofilms and that such Affimers can be attached to contrast agents such as microbubbles or polymer beads and offer potential, with some optimization, for drug-free biofilm treatment.