Blood Culture Isolates Research Articles

Exploring Antibacterial Usage and Pathogen Surveillance over Five Years in a Tertiary Referral Teaching Hospital Adult General Intensive Care Unit (ICU)

Antimicrobial resistance is a globally recognised health emergency. Intensive care is an area with significant antimicrobial consumption, particularly increased utilisation of broad-spectrum antibacterials, making stewardship programmes essential. We aimed to explore antibacterial consumption, partnered with pathogen surveillance, over a five-year period (2018 to 2023) in a tertiary referral adult general intensive care unit (ICU). The mean number of admissions was 1645 per annum. A comparison between the ICU populations admitted before and after the COVID-19 pandemic peak (2020/21) identified several notable differences with increased average daily unit bed occupancy (21.6 vs. 25.2, respectively) and a higher proportion of admissions with sepsis (28.4% vs. 32.5%, respectively) in the post-pandemic period. Over the entire five years, the overall proportion of antibacterial use by the WHO AWaRe classification was 42.6% access, 54.7% watch and 2.6% reserve. One hundred and forty-seven positive blood culture isolates were reported, with the most concerning antibacterial resistance identified in 7.5% (9 Escherichia coli and 2 Klebsiella pneumoniae isolates). The COVID-19 pandemic peak year was associated with increased ICU bed occupancy, as well as a greater number of positive blood cultures but lower antibacterial consumption. Despite an increasingly complex workload, a large proportion of overall antibacterial consumption remained within the access category. However, the mortality rate and the incidence of most concerning antimicrobial resistance with respect to pathogens remained satisfyingly consistent, suggesting the positive consequences of real-world antibiotic stewardship in an intensive care setting.

Bacteriological profile and antibiotic sensitivity pattern of bloodstream infections from a teaching institution in Eastern Uttar Pradesh, North India.

Bloodstream infections (BSIs), encompassing both self-limiting bacteremia and potentially fatal septicaemia, make up the majority of healthcare-associated ailments worldwide. The organisms encountered are mostly multidrug-resistant (MDROs), leading to increased hospital stays. Our study aims to collect data about blood culture isolates from a medical college in eastern Uttar Pradesh, India. A retrospective analysis of blood culture isolates obtained at our laboratory for ten months from patients with clinical suspicion of sepsis or infection with the possibility of haematogenous spread was done. We only considered consecutive and patient-specific, non-duplicate isolates. Blood samples were initially incubated in BacT/ALERT® and then manually processed once they flagged positive. A total of 1,033 blood samples were received, of which 217 (21%) showed the growth of a pathogenic organism. The positivity rate varied significantly across different age groups, locations, and departments (P value < 0.001). It was higher among in-patients, those with central venous access, and patients with diabetes mellitus (DM). Staphylococcus aureus [n = 105, 48.38%] was isolated most commonly, with a high prevalence of methicillin resistance (83%). Enterococcus demonstrated a high degree of resistance. MDROs accounted for 68% of the detected Gram-negatives. This study comprehensively analyses blood culture results from a diverse group of patients and emphasizes the association between risk factors and positive blood cultures. Gram-positive and Gram-negative isolates demonstrated low sensitivity to common antibiotics, urging vigilant monitoring and specific therapy. Our study reveals important insights guiding clinical practices, antimicrobial stewardship, and infection control strategies.

Blood Culture Isolates and Antibiogram for Salmonella at Tertiary Care Hospital

Objective: To determine the pattern of blood culture isolates and antibiogram for salmonella at tertiary care hospital and identify frequency of multi-drug resistance and XDR. Methodology: This descriptive, cross-sectional analysis was carried out on enteric fever/salmonella infected patients from 1-02-2020 to 31-10-2020 at Pediatrics Unit – II (Liaquat University Hospital). Children of either gender, aged 1 to 15 years, who presented with fever lasting more than 3 days, abdominal pain, headache, diarrhea, vomiting, or constipation, and who had a positive blood culture for Salmonella, were included. Data was collected into a structured questionnaire, containing enquiries pertaining to basic biodata, sociodemographic details, clinical presentation, and culture sensitivity (type of microbe and its drug sensitivity). The data obtained was analyzed using SPSS v. 21.0. Results: Mean age of the children was 9.12 years, with males comprising 63.4%. Fever and abdominal pain were the most common clinical symptoms. In terms of antibiotic sensitivity, Cefixime and Ceftriaxone were effective in 83.9% and 85.7% of cases, respectively, while Ciprofloxacin showed 81.3% sensitivity. Both Meropenem and Azithromycin were 100% effective. Among the 14 multidrug-resistant cases, Ciprofloxacin had the highest resistance rate (11 cases), while Cefixime and Ceftriaxone were resistant in 9 and 8 cases, respectively. Meropenem and Azithromycin showed no resistance in any case. Conclusion: Enteric fever remains a serious threat to child health, with rising multidrug resistance. While some drugs like Meropenem and Azithromycin are still 100% effective, they must be used carefully to prevent further resistance development.

Ceftriaxone-resistant viridans streptococci bacteraemia among patients treated at a large comprehensive cancer care centre: a retrospective eighteen-year study.

Viridans streptococci (VS) are opportunistic oral commensals and a common cause of bacteraemia in neutropenic patients. In this retrospective single centre cohort study, we investigated the prevalence of ceftriaxone resistance in VS (CRO-R VS) blood isolates between January 2005 and December 2022 from patients treated at a tertiary care hospital. Blood culture isolates were identified using biochemicals and mass spectrometry. Susceptibility testing was performed by Kirby-Bauer and Epsilometer tests. Demographic data, clinical outcomes and antimicrobial use were assessed through electronic medical record review. Among 791 patients with VS bacteraemia, 31 (4%) had confirmed CRO-R VS bacteraemia over the 18-year period; 20/31 (65%) were patients also treated at the Fred Hutchinson Cancer Center and were the focus of this study. Of these 20 patients, 18 (90%) had a known haematologic malignancy; 14 (70%) had undergone haematopoietic cell transplant (HCT); 18 (90%) were neutropenic at the time of culture. Two (10%) patients died within 30 days of CRO-R VS bacteraemia. All the CRO-R isolates (20/20) were members of the Streptococcus mitis group, 12 were multi-drug resistant; all were susceptible to vancomycin. Most patients received vancomycin once blood cultures were positive for a Gram-positive organism. During the study period, the frequency of VS isolate susceptibility testing increased; however, there was no concomitant increase in the percentage of CRO-R isolates at our facility. These data are important in an era where cefepime monotherapy is often used and reinforces the importance of routine resistance testing among VS bacteraemia.

Use of Whole Genome Sequencing for Investigation of Potential Hospital-Acquired Vancomycin Resistant Enterococcus

Background: Whole genome sequencing (WGS) is a relatively new method for analyzing outbreaks and modes of transmission, particularly for multidrug resistant bacteria. This study sought to investigate clusters of patients with genetically related Vancomycin-Resistant Enterococcus spp. (VRE) bacteremia for shared hospital environmental exposures. Methods: All VRE blood culture isolates from patients from July 1, 2021 to June 30, 2022 underwent Illumina WGS. Core single nucleotide polymorphisms (SNPs) were identified, and multi-locus sequence typing (MLST) was performed across the VRE isolates. Clusters were defined as isolates with 15 or fewer core genome SNPs and were investigated for potential transmission routes. For each cluster, patients were evaluated in the 12 weeks before and after the first VRE isolate for shared hospital environmental exposures (hospital unit, patient rooms, procedural rooms, and radiology suites). Hospital units were comprised of patient rooms located geographically together on the same floor of the hospital. Results: A total of 82 VRE isolates underwent WGS. Thirty-eight (46%) clustered genetically with at least one other isolate. Clusters included 2 to 15 patients per group and represented 10 distinct MLST subgroups (Figure 1). Nine hundred and thirty-nine hospital environmental exposures were identified across the 38 patients. For each cluster, there was a total of 341 (36.3%) shared exposures. Shared environmental exposures occurred in radiology suites (35, 38.5%), patient rooms (32, 35.6%) and procedural rooms (23, 25.6%). Of the patients who shared the same hospital unit, 10 (31.3%) had the same patient room with 7 (70%) of them being in the emergency department (ED). Overall, the ED represented 7 (21.9%) of the shared hospital units. Each cluster had at least one shared hospital environmental exposure found. Conclusions: Use of WGS can help investigate outbreak clusters of resistant organisms such as VRE. In this study, nearly half of all VRE blood isolates were able to be segregated into clusters with at least one other isolate. Although VRE colonization of hospital rooms is well described, patient rooms represented the smallest proportion of shared hospital environmental exposures. This study thus suggests other environmental transmission routes such as radiology suites and procedural rooms warrant closer investigation.

Antimicrobial resistance surveillance of Bacteroides fragilis isolated from blood cultures, Europe, 2022 (ReSuBacfrag)

ObjectivesBacteroides fragilis is the most frequent cause of anaerobic bacteraemia. Although recent data suggest a rise in antimicrobial resistance (AMR) of this and other anaerobic bacteria, surveillance remains limited due to a lack of both data availability and comparability. However, a newly introduced standardised method for antimicrobial susceptibility testing (AST) of anaerobic bacteria has made larger scale surveillance possible for the first time. The aim of this study was to investigate phenotypic AMR of Bacteroides fragilis isolates from bacteraemia across Europe in 2022. MethodsIn a multicentre approach, clinical microbiology laboratories in Europe were invited to contribute results of AST for Bacteroides fragilis blood culture isolates (including only the first isolate per patient and year). AST of a selection of four antibiotics was performed locally by participating laboratories in a prospective or retrospective manner, using the new EUCAST disc diffusion method on fastidious anaerobe agar (FAA-HB). ResultsA total of 16 European countries reported antimicrobial susceptibilities in 449 unique isolates of Bacteroides fragilis from blood cultures in 2022. Clindamycin demonstrated the highest resistance rates (20.9%, range 0 - 63.6%), followed by piperacillin-tazobactam (11.1%, 0–54.5%), meropenem (13.4%, 0–45.5%), and metronidazole (1.8%, 0–20.0%), all with wide variation between countries. ConclusionConsidering that the mean resistance rates across Europe were higher than expected for three of the four anti-anaerobic antibiotics under surveillance, both local AST of clinically relevant isolates of Bacteroides fragilis and continued surveillance on an international level is warranted.

Different sampling strategies for optimal detection of the overall genetic diversity of methicillin-resistant Staphylococcus aureus.

Surveillance schemes for methicillin-resistant Staphylococcus aureus (MRSA) are widely established at the national and international levels. Due to the simple standardization of the protocol, mainly isolates from bloodstream infections are used. However, the limitations of this simple surveillance system are well described. We conducted a comprehensive analysis of MRSA isolates in a large Slovenian region over 5 years to identify the optimal sample group for assessing the overall MRSA diversity. At the same time, this study provides to date non-available molecular characterization of Slovenian MRSA isolates. A total of 306 MRSA isolates from various sources were sequenced and phenotypically tested for resistance. The isolates exhibited significant molecular diversity, encompassing 30 multi locus sequence type (MLST) sequence types (STs), 39 ST-SCCmec genetic lineages, 49 spa types, and 29 antibiotic resistance profiles. Furthermore, the isolate pool comprised 57 resistance genes, representing 22 resistance mechanisms, and 96 virulence genes. While bloodstream isolates, commonly used in surveillance, provided insights into frequently detected clones, they overlooked majority of clones and important virulence and resistance genes. Blood culture isolates detected 21.3% spa types, 24.1% resistance phenotypes, and 28.2% MLST-SCCmec profiles. In contrast, strains from soft tissues demonstrated superior genomic diversity capture, with 65.3% spa types, 58.6% resistance phenotypes, and 71.8% MLST-SCCmec profiles. These strains also encompassed 100.0% of virulence and 82.5% of resistance genes, making them better candidates for inclusion in surveillance programs. This study highlights the limitations of relying solely on bloodstream isolates in MRSA surveillance and suggests incorporating strains from soft tissues to obtain a more comprehensive understanding of the epidemiology of MRSA.IMPORTANCEIn this study, we investigated the diversity of methicillin-resistant Staphylococcus aureus (MRSA), a bacterium that can cause infections that are difficult to treat due to its resistance to antimicrobial agents. Currently, surveillance programs for MRSA mainly rely on isolates from bloodstream infections, employing a standardized protocol. However, this study highlights the limitations of this approach and introduces a more comprehensive method. The main goal was to determine which group of samples is best suited to understand the overall diversity of MRSA and to provide, for the first time, molecular characterization of Slovenian MRSA isolates. Our results suggest that including MRSA strains from soft tissue infections rather than just blood infections provides a more accurate and comprehensive view of bacterial diversity and characteristics. This insight is valuable for improving the effectiveness of surveillance programs and for developing strategies to better manage MRSA infections.

Evaluation of the QMAC-dRAST System Version 2.5 for Rapid Antimicrobial Susceptibility Testing of Gram-Negative Bacteria From Positive Blood Culture Broth and Subcultured Colony Isolates.

Rapid antimicrobial susceptibility testing (AST) for bloodstream infections (BSIs) facilitates the optimization of antimicrobial therapy, preventing antimicrobial resistance and improving patient outcomes. QMAC-dRAST (QuantaMatrix Inc., Korea) is a rapid AST platform based on microfluidic chip technology that performs AST directly using positive blood culture broth (PBCB). This study evaluated the performance of QMAC-dRAST for Gram-negative bacteria using PBCB and subcultured colony isolates, comparing it with that of VITEK 2 (bioMérieux, France) using broth microdilution (BMD) as the reference method. We included 141 Gram-negative blood culture isolates from patients with BSI and 12 carbapenemase-producing clinical isolates of Enterobacterales spiked into blood culture bottles. QMAC-dRAST performance was evaluated using PBCB and colony isolates, whereas VITEK 2 and BMD were tested only on colony isolates. For PBCB, QMAC-dRAST achieved 92.1% categorical agreement (CA), 95.3% essential agreement (EA), with 1.8% very major errors (VMEs), 3.5% major errors (MEs), and 5.2% minor errors (mEs). With colony isolates, it exhibited 92.5% CA and 95.1% EA, with 2.0% VMEs, 3.2% MEs, and 4.8% mEs. VITEK 2 showed 94.1% CA and 96.0% EA, with 4.3% VMEs, 0.4% MEs, and 4.3% mEs. QMAC-dRAST yielded elevated error rates for specific antimicrobial agents, with high VMEs for carbapenems and aminoglycosides. The median time to result for QMAC-dRAST was 5.9 h for PBCB samples and 6.1 h for subcultured colony isolates. The QMAC-dRAST system demonstrated considerable strengths and comparable performance to the VITEK 2 system; however, challenges were discerned with specific antimicrobial agents, underlining a necessity for improvement.

A five-year retrospective antibiogram review in the paediatric burns unit at a tertiary South African Hospital

BackgroundThere is a global concern regarding increasing colonization and/or infection of paediatric burns patients with multi-drug-resistant organisms, especially in Africa. Surveillance of antimicrobial resistant patterns enables clinicians to opt for the most appropriate empiric antimicrobial agent according to the unit’s susceptibility profile. ObjectiveThis study sought to compile unit-specific antibiograms comparing the organism prevalence and their antimicrobial resistance trends in the paediatric burns unit, Chris Hani Baragwanath Academic Hospital (CHBAH) from January 2015 to December 2019. MethodsA retrospective, laboratory-based review was conducted of bacterial and fungal isolates including antimicrobial susceptibility testing (AST) data from blood cultures and tissue samples. Enterobacterales, non-fermenters, gram-positive organisms, and yeasts were analysed as a percentage of total positive blood cultures comparing 2015–2017 to 2018–2019 data. Analysis of antimicrobial resistance trends was performed for extended-spectrum beta-lactamases (ESBLs), carbapenem-resistant Enterobacterales (CRE), extensively-drug-resistant (XDR) Acinetobacter baumannii, and meticillin-resistant Staphylococcus aureus (MRSA) for the years 2015, 2017, and 2019. ResultsA total of 1243 blood culture isolates were studied with A.baumannii (208/1243;17 %), coagulase negative staphylococci (141/1243; 11 %) and Candida auris (53/1243; 4 %) representing the predominant gram-negative bacteria, gram-positive bacteria, and yeast, respectively. A significant decrease in ESBLs (p = 0.00) was noted with a rise in CREs (p = 0.00) during the study period. Majority of the A. baumannii were XDR (≥77 %) despite an appreciable decrease. A notable decrease in MRSA (p = 0.00) isolates was observed. Pseudomonas aeruginosa (72/275; 26 %) was the leading organism recovered from a total of 275 tissue isolates. ConclusionThe results of this study encourage review of the current antimicrobial choices in the unit for empiric antibacterial cover. Due to the low numbers of yeasts, we cannot comment on the institution of early antifungal strategies. We support reinforced infection prevention and control practices as well as antimicrobial stewardship initiatives.

Apramycin efficacy against carbapenem- and aminoglycoside-resistant Escherichia coli and Klebsiella pneumoniae in murine bloodstream infection models

BackgroundThe aminoglycoside apramycin has been proposed as a drug candidate for the treatment of critical Gram-negative systemic infections. However, the potential of apramycin in the treatment of drug-resistant bloodstream infections (BSIs) has not yet been assessed. MethodsThe resistance gene annotations of 40 888 blood-culture isolates were analysed. In vitro profiling of apramycin comprised cell-free translation assays, broth microdilution, and frequency of resistance determination. The efficacy of apramycin was studied in a mouse peritonitis model for a total of nine Escherichia coli and Klebsiella pneumoniae isolates. ResultsGenotypic aminoglycoside resistance was identified in 87.8% of all 6973 carbapenem-resistant Enterobacterales blood-culture isolates, colistin resistance was shown in 46.4% and apramycin in 2.1%. Apramycin activity against methylated ribosomes was > 100-fold higher than that for other aminoglycosides. Frequencies of resistance were < 10-9 at 8 × minimum inhibitory concentration (MIC). Tentative epidemiological cut-offs (TECOFFs) were determined as 8 µg/mL for E. coli and 4 µg/mL for K. pneumoniae. A single dose of 5 to 13 mg/kg resulted in a 1-log colony-forming unit (CFU) reduction in the blood and peritoneum. Two doses of 80 mg/kg resulted in an exposure that resembles the AUC observed for a single 30 mg/kg dose in humans and led to complete eradication of carbapenem- and aminoglycoside-resistant bacteraemia. ConclusionEncouraging coverage and potent in vivo efficacy against a selection of highly drug-resistant Enterobacterales isolates in the mouse peritonitis model warrants the conduct of clinical studies to validate apramycin as a drug candidate for the prophylaxis and treatment of BSI.

Cephalotin Versus Dicloxacillin for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteraemia: A Retrospective Cohort Study.

First-line treatments for methicillin-susceptible S. aureus (MSSA) bacteraemia are nafcillin, oxacillin, or cefazolin. Regional shortages of these antibiotics force clinicians to use other options like dicloxacillin and cephalotin. This study aims to describe and compare the safety and efficacy of cephalotin and dicloxacillin for the treatment of MSSA bacteraemia. This retrospective study was conducted in a referral centre in Mexico City. We identified MSSA isolates in blood cultures from 1 January 2012 to 31 December 2022. Patients ≥ 18 years of age, with a first episode of MSSA bacteraemia, who received cephalotin or dicloxacillin as the definitive antibiotic treatment, were included. The primary outcome was in-hospital all-cause mortality. We included 202 patients, of which 48% (97/202) received cephalotin as the definitive therapy and 52% (105/202) received dicloxacillin. In-hospital all-cause mortality was 20.7% (42/202). There were no differences in all-cause in-hospital mortality between patients receiving cephalotin or dicloxacillin (20% vs. 21%, p = 0.43), nor in 30-day all-cause mortality (14% vs. 18%, p = 0.57) or 90-day all-cause mortality (24% vs. 22%, p = 0.82). No severe adverse reactions were associated with either antibiotic. Cephalotin and dicloxacillin were equally effective for treating MSSA bacteraemia, and both showed an adequate safety profile.

The first tigecycline resistant Enterococcus faecium in Norway was related to tigecycline exposure

We describe the first tigecycline resistant enterococcal isolate in Norway and the mechanisms involved. The Norwegian National Advisory Unit on Detection of Antimicrobial Resistance (K-res). received in 2022 an Enterococcus faecium blood culture isolate with decreased susceptibility to tigecycline from a hospitalized patient in the South-Eastern Norway Health region for confirmatory testing. K-res verified a tigecycline-resistant E. faecium (TigR) with broth microdilution MIC of 0.5 mg/L. The patient had received treatment with tigecycline because of an infection with a linezolid- and vancomycin-resistant but tigecycline susceptible E. faecium (TigS) 47 days prior to the detection of the corresponding tigecycline-resistant isolate. Whole-genome comparisons, cgMLST and SNP analyses revealed that the two ST117 strains were closely related. The TigR isolate showed a novel deletion of 2 amino acids (K57Y58) in a polymorphic region of ribosomal protein S10 previously associated with tigecycline resistance and a deletion of the tet(M) leader peptide previously related to increased expression of tet(M) and tigecycline resistance in enterococci. Genomic and epidemiological analyses confirm that the two E. faecium (TigR and TigS) are closely related isolates of the same strain and that the two deletions (in rpsJ and of tet(M) leader peptide) account for the tigecycline resistance in TigR.

Clinical characteristics and antimicrobial susceptibility of Fusobacterium species isolated over 10years at a Japanese university hospital.

Anaerobic bacteria, existing on human skin and mucous membranes, can cause severe infections with complications or mortality. We examined the clinical characteristics of patients infected with Fusobacterium spp. and assessed their antibiotic susceptibility. Clinical data were collated from patients diagnosed with Fusobacterium infections in a Japanese university hospital between 2014 and 2023. Antibiotic susceptibility tests were conducted following the Clinical and Laboratory Standards Institute guidelines. We identified 299 Fusobacterium isolates. The median age was 61years (range, 14-95years), with females constituting 43.1% of the patients. Most infections were community-acquired (84.6%, 253/299). Multiple bacterial strains were isolated simultaneously in 74.6% of cases. One-fourth of the patients had solid organ malignancies (25.4%, 76/299), and 14.5% (11/76) of those had colorectal cancer. The 30-day mortality rate was 1.3%. Fusobacterium species were isolated from blood cultures in 6% (18/299) of the patients. Patients, aged 75years or older, with cerebrovascular disease or hematologic malignancy exhibited significantly higher prevalence of blood culture isolates in univariate analysis. Each Fusobacterium species had its characteristic infection site. Approximately 5% F. nucleatum and F. necrophorum isolates showed penicillin G resistance. Moxifloxacin resistance was observed in varying degrees across strains, ranging from 4.6 to 100% of isolates. All isolates were sensitive to β-lactam/β-lactamase inhibitors, carbapenems, and metronidazole. We show a link between Fusobacterium species and solid organ malignancies. We observed resistance to penicillin, cefmetazole, clindamycin, and moxifloxacin, warranting caution in their clinical use. This study offers valuable insights for managing Fusobacterium infections and guiding empirical treatments.

2241. Antibiotic Use Before and After Hospital Admission Among Hospitalized Patients with Acute Febrile Illness in Bangladesh

Abstract Background The inappropriate use of antibiotics is common in Bangladesh, contributing to the significant burden of antimicrobial resistance. The WHO has categorized Access, Watch, and Reserve groups of antibiotics (AWaRe classification) to promote optimal use. We explored antibiotic use among hospitalized patients with acute febrile illness (AFI) at five tertiary-level hospitals in Bangladesh. Methods From September 2021 to February 2023, 1544 patients were randomly selected among all hospitalized patients with measured fever (≥100.4°F) or a history of fever in the past 14 days. Blood and urine culture isolates were analyzed for antibiotic sensitivity using the VITEK-2 system. Results Of enrolled AFI patients, 835 (54%) reported the use of antibiotics prior to hospitalization, with 79% of reported antibiotics from the Watch group, 16% from the Access group, and none from the Reserve group. Five percent of the antibiotics prescribed were not recommended by WHO for clinical practice. The top five frequently reported antibiotics before hospitalization were cefixime (24%), azithromycin (19%), ceftriaxone (16%), amoxicillin (6%), and cefuroxime (5%). Bacterial infection was diagnosed among 205 patients (13% of all enrollees) through Rapid diagnostic tests, culture and Rt-PCR. In-hospital, 1385 (90%) patients received at least one antibiotic. The most frequently prescribed antibiotics were from the Watch group (84%), followed by the Access group (15%) and none from the Reserve group. The top five antibiotics prescribed in-hospital were ceftriaxone (64%), amoxiclav (7%), ceftazidime (3.4%), clarithromycin (2.8%), and moxifloxacin (2.6%). Antibiotic susceptibility testing (AST) results from blood and urine culture isolates showed high resistance pattern to ceftriaxone (45% and 56%) and ceftazidime (63% and 50%). Of blood culture isolates 80% were sensitive to amoxiclav, while 46% of urine culture isolates were resistant to amoxiclav. At least one bacterial organism was identified in only 13% of enrolled patients. List of antibiotics that were reported to be received by the enrolled AFI patients before Hospitalization Before hospitalization, 132 patients reported receiving antibiotics from Access group, while 662 patients received antibiotics from WATCH group List of antibiotics received by the enrolled AFI patients during hospitalization During hospitalization, 211 patients received antibiotics from Access group and 1169 patients received antibiotics from Watch Group List of 235 bactrial organisms which were identified from clinical samples of 205 AFI patients (some patient had co-infection) Conclusion In conclusion, antibiotics were used in nine of ten patients. The frequent and inappropriate use of Watch group antibiotics in outpatient settings likely contributes to decreased effectiveness and demonstrates the need for improved antimicrobial stewardship. Disclosures All Authors: No reported disclosures

565. Antimicrobial susceptibility profiles of Acinetobacter species in blood: 10-year experience from a major United States reference laboratory

Abstract Background Antimicrobial resistance (AMR) is a threat to healthcare, and infections with antimicrobial resistant organisms carry significant morbidity and mortality. Owing to high rates of AMR, the Centers for Disease Control and Prevention listed Acinetobacter baumannii as a top priority pathogen for research and development of new antimicrobial agents. Antimicrobial susceptibility testing is challenging for this organism, and susceptibility profiles are variable, leading to need of a potential guidance document with assistance in selecting effective empiric therapeutic regimens. Methods We retrospectively reviewed the microbiology and antimicrobial susceptibility testing (AST) results for Acinetobacter spp. from blood culture isolates submitted to Mayo Clinic Laboratories from December 2012 to 2022. AST was performed using agar dilution and interpretations following Clinical &amp; Laboratory Standards Institute (CLSI) guidelines. Isolates were identified by MALDI mass spectrometry and/or 16S sequencing, as available (Figure 1).Figure 1:Isolate identification Isolate identification description. Isolates were analyzed based on this classification used in out laboratory. Results 804 blood culture isolates were included. A. baumannii/calcoaceticus complex (27%) was most frequently isolated, followed by A. lwoffii (22%), and showed the highest resistance across all antimicrobials (73% susceptible or below) (Figure 2). A. baumannii/calcoaceticus complex showed rising resistance rates over time from 2012 to 2022 for meropenem, minocycline and ampicillin-sulbactam (Figure 3). Cefiderocol non-susceptible rate was 35% for A. baumannii/calcoaceticus complex.Figure 2:Antimicrobial susceptibility profiles for Acinetobacter spp. Description of susceptibility profiles for Acinetobacter spp. isolates, based on the classification used by our laboratory. Antimicrobials are presented at the top and isolates on the left. Number of isolates analyzed are presented in the table with the percentage of the isolates susceptible to each antibiotic class in parenthesis.Figure 3:Acinetobacter baumannii/calcoaceticus complex isolates and resistance, trend Trend of isolates per year and resistance percentage to meropenem, colistin, minocycline and amp-sulb. Number of isolates per year at the base of each bar; percentage of resistance for antimicrobials expressed on lines. Amp-sulb = ampicillin-sulbactam. Conclusion A. baumannii/calcoaceticus complex showed high levels of resistance ( &amp;gt;75%) across multiple antimicrobials and increasing rates of resistance over time from 2012 to 2022. A high number of cefiderocol non-susceptible organisms is also concerning (Figure 2). Disclosures Audrey N. Schuetz, MD, Merck: Advisor/Consultant

2809. In Vitro Synergy of Antibiotic Combinations Against Enterococcus gallinarum

Abstract Background Enterococci are an important cause of endocarditis, particularly involving prosthetic valves. The prevalence of E. gallinarum has been increasing in recent years. Unlike E. faecalis, no information is available regarding the bactericidal activity of ampicillin alone or combined with gentamicin or ceftriaxone against E. gallinarum. Methods Ten blood culture isolates of E. gallinarum were studied. The isolates came from unique patients at a single hospital. MICs of ampicillin, ceftriaxone and gentamicin were done by the CLSI microdilution method. ATCC strains E. faecalis 29212 and P. aeruginosa 27853 were used as controls. Time-kill studies were performed in CA-MHB for ampicillin 10 mg/L, ceftriaxone 10 mg/L, gentamicin at 0.25 x MIC up to a maximum of 4 mg/L, ampicillin + ceftriaxone, and ampicillin + gentamicin. Bactericidal activity was defined as a 1,000-fold decrease in the log10 cfu/mL at 24 h. Synergy was defined as a 100-fold decrease in the log10 cfu/ml at 24 h in a combination compared to each single agent. Results The MICs of ampicillin ranged from 1 to 8 mg/L, gentamicin from 2 to 16 mg/L, and ceftriaxone were all ≥ 32 mg/L. Results of the time-kill studies are summarized in the Table. Ampicillin alone was bactericidal against a single isolate. For that isolate, testing of ampicillin at 0.25 x MIC with gentamicin demonstrated synergy. The combination of ampicillin + ceftriaxone was synergistic against a single isolate, but was otherwise similar to ampicillin alone. Ampicillin + gentamicin was bactericidal against all isolates and was synergistic against all but one isolate. Conclusion Ampicillin alone was generally not bactericidal against E. gallinarum but had synergistic bactericidal activity when combined with gentamicin, similar to the findings with E. faecalis. However, unlike E. faecalis, ampicillin + ceftriaxone was not bactericidal against most isolates of E. gallinarum. These findings support the suggestion that ampicillin + gentamicin might be the optimal treatment for endovascular infections caused by E. gallinarum. Disclosures All Authors: No reported disclosures

Invasive non-typhoidal Salmonella from stool samples of healthy human carriers are genetically similar to blood culture isolates: a report from the Democratic Republic of the Congo

Invasive non-typhoidal Salmonella from stool samples of healthy human carriers are genetically similar to blood culture isolates: a report from the Democratic Republic of the Congo

Strain-resolved metagenomic analysis of the gut as a reservoir for bloodstream infection pathogens among premature infants in Singapore

BackgroundGut dysbiosis contributes to the high risk of bloodstream infection (BSI) among premature infants. Most prior studies of the premature infant gut microbiota were conducted in Western countries and prior to development of current tools for strain-resolved analysis.MethodsWe performed metagenomic sequencing of weekly fecal samples from 75 premature infants at a single hospital in Singapore. We evaluated associations between clinical factors and gut microbiota composition using PERMANOVA and mixed effects linear regression. We used inStrain to perform strain-level analyses evaluating for gut colonization by BSI-causing strains.ResultsMedian (interquartile range) gestation was 27 (25, 29) weeks, and 63% of infants were born via Cesarean section. Antibiotic exposures (PERMANOVA; R2 = 0.017, p = 0.001) and postnatal age (R2 = 0.015, p = 0.001) accounted for the largest amount of variability in gut microbiota composition. Increasing postnatal age was associated with higher relative abundances of several common pathogens (Enterococcus faecalis: p < 0.0001; Escherichia coli: p < 0.0001; Klebsiella aerogenes: p < 0.0001; Klebsiella pneumoniae: p < 0.0001). Antibiotic exposures were generally associated with lower relative abundances of both frequently beneficial bacteria (e.g., Bifidobacterium species) and common enteric pathogens (e.g., Enterobacter, Klebsiella species). We identified strains identical to the blood culture isolate in fecal samples from 12 of 16 (75%) infants who developed BSI, including all infections caused by typical enteric bacteria.ConclusionsAntibiotic exposures were the dominant modifiable factor affecting gut microbiota composition in a large cohort of premature infants from South-East Asia. Strain-resolved analyses indicate that the gut is an important reservoir for organisms causing BSI among premature infants.

Fusariosis in Mexico: A 10-year retrospective series.

Fusarium species represent an opportunistic fungal pathogen. The data in Mexico about Fusarium infections in humans are scarce. Here, we present a retrospective series of patients with a confirmed diagnosis of fusariosis in eight different hospitals in Mexico from January 2010 to December 2019. The diagnosis of proven fusariosis was made according to the European Organization for Research and Treatment of Cancer and the Mycoses Study Group Education and Research Consortium (EORT/MSG) criteria. A total of 49 cases were identified in our series. Most patients had burn injuries (49%), and 37% had hematological malignancies. Most patients had fire injuries (40%), followed by electric injuries (8%), febrile neutropenia (10%), and pancytopenia (6%). Patients had skin and soft tissue involvement in 49%, followed by blood culture isolation and biopsies from different sites of the body (lung, sinuses, bone tissue, and eyes). Febrile neutropenia (10%) and fungemia (8%) were the most common clinical syndromes in immunosuppressed patients. Most patients received monotherapy (67%), where voriconazole was used in 30% of the cases, followed by conventional amphotericin B (16%), and lipidic formulations of amphotericin B in 10% (either liposomal amphotericin B or amphotericin B lipid complex). Combination therapy was used in 20% of the cases, and the most common combination therapy was triazole plus any lipidic formulation of amphotericin B (10%). Mortality related to Fusarium infection occurred in 22% of patients. Fusariosis is a serious threat. Burn injuries and hematologic malignancies represent the most common causes of infection in this small series from Mexico.

The relevance of coagulase-negative Staphylococcus isolates in blood culture in the context of a tertiary neonatal unit from East India

Background: Coagulase-negative Staphylococcus (CoNS) are known commensals and often contaminate neonatal blood cultures. Their unique ability to form biofilms, however, helps them evade immune mechanisms and antibiotics and cause neonatal sepsis (NS) in hospitalized neonates. True or probable Coagulase-negative Staphylococcus blood stream infection (CoNS BSI) must be differentiated from contaminants so that antibiotics are used judiciously and hospital stay is minimized. Aims and Objectives: The primary objective of the study was to estimate the proportion of NS and contaminants among CoNS-positive blood cultures in the index neonatal unit and the host and health-care variables associated with CoNS BSI. The secondary objective was to estimate the susceptibility of CoNS isolates to antibiotics used. Materials and Methods: This was a retrospective study from digital records, from January 2018 to December 2022. Results: 25% of CoNS isolates were associated with NS (health-care infections) and 75% were contaminants. Over 90% of CoNS BSI was associated with central lines (CLs) and prolonged hospital stay. All isolates were resistant to oxacillin while resistance to gentamicin rose annually to over 68%. Susceptibility to linezolid and vancomycin was present, but a few strains were resistant to them. Conclusion: CoNS were an important cause of NS in the index hospital. Prolonged hospital stays and CLs were associated with increased incidence of CoNS sepsis and must be minimized where possible. Antibiotic resistance was high, and reserve drugs could also become ineffective.