Additional Blood Cultures Research Articles

Tailored Approach to Evaluation and Management of Early Onset Neonatal Sepsis in a Safety-Net Teaching Hospital in Northeast Florida.

Objective Early onset neonatal sepsis (EONS) remains a significant cause of morbidity and mortality in newborns in the immediate postnatal period. High empiric antibiotic use in well-appearing infants with known risk factors for sepsis led the American Academy of Pediatrics (AAP) to revise its 2010 guidelines for the evaluation and management of EONS to avoid overuse of antibiotics. In this recent clinical report, the AAP provided a framework that outlined several evidence-based approaches for sepsis risk assessment in newborns that can be adopted by institutions based on local resources and structure. One of these approaches, the sepsis risk calculator (SRC) developed by Kaiser Permanente, has been widelyvalidated for reducing unnecessary antibiotic exposure and blood work in infants suspected of having EONS. In order to determine the utility and safety of modifying our institution's protocol to the SRC, we implemented a two-phased approach to evaluate the use of SRC in our newborn nursery. Phase 1 utilized a retrospective review of cases with SRC superimposition. If results from Phase 1 were found to be favorable, Phase 2 initiated a trial of the SRC for a six-month period prior to complete implementation. Methods Phase 1 consisted of retrospectively applying the SRCto electronic medical records (EMR) of infants ≥ 35 weeks' gestational age admitted to the newborn nursery with risk factors for EONS between June 2016 and May 2017. We compared actual antibiotic use as determined by the unit's EONS protocol for evaluation and management based on 2010 Centers for Disease Control and Prevention (CDC) and AAP guidelines to SRC-recommended antibiotic use. We used EMR to determine maternal and infant data, blood work results, and antibiotic usage as well asused daily progress notes by the clinical team to determine the clinical status of the infants retrospectively. Based on the projected reduction in blood work and antibiotics use with the retrospective superimposition of SRC on this cohort of infants and identification of our high-risk patient subset, we developed a novel, hybrid EONS protocol that we implemented and assessed throughout Phase 2, a six-month period from August 2018 to January 2019, as a prospective observational study. Results Phase 1 (SRC superimposition) demonstrated that the use of the SRC would have reduced empiric antibiotic use from 56% to 13% in the study cohort when compared with 2010 CDC/AAP guidelines. However, these same findings revealed use of the SRC would have resulted in delayed evaluation and initiation of antibioticsin 2 of 4 chorioamnionitis-exposed infants with positive blood cultures. During Phase 2 (n=302), with the implementation of our tailored approach (SRC implementation with additional blood culture in chorioamnionitis-exposed infants), 12 (4%) neonates received empiric antibiotic treatment compared to nine (3%) neonates who would have been treated per strict adherence to SRC recommendations. No neonate had culture-positive EONS. Continued use of 2010 CDC/AAP guidelines would have led to empiric antibiotic use in 38 (12.6%) infants in this cohort. Conclusion We developed a novel hybrid approach to the evaluation and management of neonates at increased risk of EONS by tailoring SRC recommendations to our safety-net population. Our stewardship effort achieved a safe and significant reduction in antibiotic usage compared to prior usage determined using CDC/AAP guidelines.

QSOFA does not predict bacteremia in patients with severe manifestations of sepsis.

Bloodstream infections in septic patients may be missed due to preceding antibiotic therapy prior to obtaining blood cultures. We leveraged the FABLED cohort study to determine if the quick Sequential Organ Failure Assessment (qSOFA) score could reliably identify patients at higher risk of bacteremia in patients who may have false negative blood cultures due to previously administered antibiotic therapy. We conducted a multi-centre diagnostic study among adult patients with severe manifestations of sepsis. Patients were enrolled in one of seven participating centres between November 2013 and September 2018. All patients from the FABLED cohort had two sets of blood cultures drawn prior to the administration of antimicrobial therapy, as well as additional blood cultures within 4 hours of treatment initiation. Participants were categorized according to qSOFA score, with a score ≥2 being considered positive. Among 325 patients with severe manifestations of sepsis, a positive qSOFA score (defined as a score ≥2) on admission was 58% sensitive (95% CI 48% to 67%) and 41% specific (95% CI 34% to 48%) for predicting bacteremia. Among patients with negative post-antimicrobial blood cultures, a positive qSOFA score was 57% sensitive (95% CI 42% to 70%) and 42% specific (95% CI 35% to 49%) to detect patients who were originally bacteremic prior to the initiation of therapy. Our results suggest that the qSOFA score cannot be used to identify patients at risk for occult bacteremia due to the administration of antibiotics pre-blood culture.

9. The Skip Phenomenon in Staphylococcus aureus Bacteremia: Clinical Associations

BackgroundSerial blood cultures are integral in managing Staphylococcus aureus bacteremia (SAB) as clinicians rely on the results to determine infectious complication risks and antibiotic duration. Current IDSA guidelines suggest a single set of negative blood cultures is adequate evidence of SAB clearance. Several studies, however, have identified the skip phenomenon (SP), which is the occurrence of intermittent negative blood cultures, and have recommended obtaining additional blood cultures to document bacterial clearance (Table 1). We therefore examined patients who manifested the SP to determine its clinical significance and to study this, associations were tested for SP in relation to various baseline factors as well as clinical outcomes. MethodsWe performed a retrospective, multicenter study of all patients with a positive blood culture for S. aureus from January 2019 to December 2019 using data collected from electronic health records and the clinical microbiology laboratory. ResultsA total of 602 patients with SAB were identified and 495 patients were included in the investigation (Figure 1). Overall, 25 (5.1%) patients had the SP. Significant differences between those who did and did not manifest the SP included higher rates of injection drug use, automatic implantable cardioverter defibrillator, and community onset of infection in the SP cohort (Table 2). Moreover, the median duration of SAB was longer (3.2 [2.3-5.4] vs 1.90 [1.2-2.9] days, p=0.002), and high-grade SAB, (88.0% vs 58.7%, p=0.004), complicated bacteremia (92.0% vs 67.9%, p=0.011) and IE diagnosis (28.0% vs 11.3%, p=0.013) were all more common in the SP group. In unadjusted outcome analyses, association of SP with hospital length of stay was not significant, although a higher risk of in-hospital mortality among SP patients approached statistical significance (p=0.055). Analysis of 435 hospital survivors revealed no significant differences in rates of 1-year mortality or 90-day relapse between the two groups (Table 3). ConclusionFindings of the current investigation demonstrates an increased risk of SAB complications in patients with the SP and support the notion that serial negative blood cultures are needed to document clearance of SAB. Disclosures Larry M. Baddour, MD, Boston Scientific (Individual(s) Involved: Self): Consultant; Botanix Pharmaceuticals (Individual(s) Involved: Self): Consultant; Roivant Sciences (Individual(s) Involved: Self): Consultant Muhammad R. Sohail, MD, Medtronic (Consultant)Philips (Consultant)

Follow-up Blood Cultures in Children With Staphylococcus aureus Bacteremia.

Staphylococcus aureus is a common pathogen seen in pediatric bloodstream infections. Currently, no evidence-based recommendations are used to guide decisions on the number of follow-up blood cultures (FUBCs) needed to demonstrate infection clearance. Unnecessary cultures increase the risk of false-positives, add to health care costs, and create additional trauma to children and their families. In this study, we examined risk factors for persistent S aureus bacteremia (SAB) and intermittent positive blood cultures (positive cultures obtained after a documented negative FUBC result) to determine the number of FUBCs needed to demonstrate infection clearance in children. Patients ≤18 years who were hospitalized with SAB at Texas Children's Hospital in 2018 were reviewed. We assessed the impact of an infectious disease diagnosis (central line-associated bloodstream infection, osteomyelitis, soft tissue infection, endocarditis, etc) and medical comorbidities on bacteremia duration. Patients with intermittent positive blood cultures were studied to determine the characteristics of this group and overall frequency of reversion to positive cultures. A total of 122 subjects met the inclusion criteria. The median duration of bacteremia was 1 day (interquartile range: 1-2 days). Only 19 patients (16%) had bacteremia lasting ≥3 days, all of whom had a diagnosis of central line-associated bloodstream infection, osteomyelitis, or endocarditis. Intermittent positive cultures occurred in 5% of patients, with positive cultures after 2 negative FUBC results seen in <1% of patients. Intermittent positive cultures were strongly associated with osteomyelitis and endocarditis. On the basis of our sample of children with SAB, additional blood cultures to document sterility are not necessary after 2 FUBC results are negative in well-appearing patients.

Quality Improvement Project Demonstrate that Prolonged Pre-Analytical Time Does Not Lead to False Negative Blood Cultures

Abstract Introduction/Objective Bacterial infection is a significant cause of morbidity and mortality. Prompt identification of microorganisms and their susceptibilities to antimicrobial therapies is critical in the management of patients with bloodstream infections. Blood cultures are collected in paired aerobic and anaerobic bottles. However, transport delays might allow some organisms to grow extensively prior to incubation in the blood culture instruments, leading to false-negative culture results. The Detroit Medical Center utilizes the BD Bactec™ instruments for blood culture incubation and the Verigene DNA-based molecular assay for the identification of bacteria and major resistance genes. It has a core microbiology lab that serves 6 hospitals, however, 2 of the hospitals are remotely located. The aim of this project was to determine if transportation delays led to significant false-negative culture results. If significant false negativity occurred, additional Bactec™ instruments would need to be purchased. Methods For one month, we tracked the collection of blood cultures to incubation time at one of the remote hospitals. All blood cultures that remain negative after 164 hours of incubation are routinely discarded. However, in this case, they were subcultured to a Petri plate containing chocolate agar for 30 days. Any organisms that grew were identified by standard lab techniques. Results Of the 547 negative culture bottles that were subcultured for possible false-negative results, only 3 (0.5%) bottles grew bacteria. All three were isolated from different patients. The mean time from blood collection to incubation in the instrument was 4-8 hours. The isolates either met criteria for contaminated cultures, or they grew the same pathogen that had previously been identified in the paired bottle from the same culture. The organisms isolated include coagulase negative Staphylococcus species, Staphylococcus pettenkoferi, and Pseudomonas aeruginosa. No unexpected pathogenic organisms were detected. Conclusion Our results demonstrate that prolonged pre-analytical time does not lead to false-negative blood culture results. The patients’ diagnoses were not changed, therefore, the purchase of additional blood culture instruments was not necessary. However, transportation time from the patient floors to the main microbiology lab needs to be improved to meet the recommended 2 hours pre-analytical time.

2092. How Long Should You Delay Insertion of a Long-Term Central Venous Catheter (LTCVC) in Patients with Candida Bloodstream Infection (CBSI)?

BackgroundGuidelines suggest that among patients with candidemia, placement of an LTCVC, often needed for treatment, can proceed when “additional blood cultures show no growth” but the timeframe is not well defined. There is theoretical risk of relapsed CBSI after therapy if yeast are still circulating in the blood and adhere to the LTCVC. We sought to determine the blood culture time to detection (TTD) for candida to identify a timeframe for LTCVC insertion that would mitigate risk for relapsed CBSI.MethodsWe conducted a retrospective cohort study of all positive (+) blood cultures for Candida species (albicans, glabrata, tropicalis, parapsilosis, dubliniensis, krusei, and lusitaniae) isolated from August 1, 2013–December 31, 2017. Data were retrieved from the microbiology laboratory and the BD BACTEC™ blood culture system was used. TTD was recorded for each (+) blood culture in hours and the mean TTD was calculated by species.ResultsOne hundred and twenty-eight blood cultures were (+) for Candida species. C. glabrata was the most common species isolated, followed by C. albicans and C. parapsilosis. Overall, the mean TTD was 43 hours (range 7.1–117.7 hours); 19.5% were positive within 24 hours, 67.2% within 48 hours, and 86.7% within 72 hours, and none required more than 120 hours (table).ConclusionAmong patients with candidemia, the majority of blood cultures were positive within 72 hours after inoculation and all were positive within 120 hours; however, among the three most common species, 16.3% required more than 72 hours. Waiting 120 hours before insertion of a LTVC should mitigate risk for relapsed CBSITable.TTD for Candida Species Isolated from Blood Culture# (%)TTD (Hours)# (+) Within 24 Hours (%)# (+) Within 48 Hours (%)# (+) Within 72 Hours (%)# (+) Between>72–120 Hours (%)MeanMedian C. glabrata 52 (40.6)44338 (15.4)27 (51.9)8 (15.4)9 (17.3) C. albicans 27 (21.1)48493 (11.1)10 (37)10 (37)4 (14.8) C. parapsilosis 25 (19.5)45385 (20)12 (48)4 (16)4 (16) C. tropicalis 14 (10.9)34345 (35.7)6 (42.8)3 (21.4)0 C. krusei 6 (4.7)31292 (33.3)4 (66.7)00 C. dubliniensis 3 (2.3)23192 (66.7)1 (33.3)00 C. lusitaniae 1 (0.8)303001(100)00 Total 128433725 (19.5)61 (47.7)25 (19.5)17 (13.3)Disclosures All authors: No reported disclosures.

HIV-Associated Mycobacterium tuberculosis Bloodstream Infection Is Underdiagnosed by Single Blood Culture.

ABSTRACTWe assessed the additional diagnostic yield for Mycobacterium tuberculosis bloodstream infection (BSI) by doing more than one tuberculosis (TB) blood culture from HIV-infected inpatients. In a retrospective analysis of two cohorts based in Cape Town, South Africa, 72/99 (73%) patients with M. tuberculosis BSI were identified by the first of two blood cultures during the same admission, with 27/99 (27%; 95% confidence interval [CI], 18 to 36%) testing negative on the first culture but positive on the second. In a prospective evaluation of up to 6 blood cultures over 24 h, 9 of 14 (65%) patients with M. tuberculosis BSI had M. tuberculosis grow on their first blood culture; 3 more patients (21%) were identified by a second independent blood culture at the same time point, and the remaining 2 were diagnosed only on the 4th and 6th blood cultures. Additional blood cultures increase the yield for M. tuberculosis BSI, similar to what is reported for nonmycobacterial BSI.

The influence of different fever definitions on diagnostics and treatment after diagnosis of fever in chemotherapy-induced neutropenia in children with cancer.

BackgroundThere is no evidence-based definition of the temperature limit defining fever (TLDF) in children with neutropenia. Lowering the TLDF is known to increase the number of episodes of fever in neutropenia (FN). This study aimed to investigate the influence of a lower versus standard TLDF on diagnostics and therapy.MethodsIn a single pediatric cancer center using a high standard TLDF (39°C tympanic-temperature) patients were observed prospectively (NCT01683370). The effect of applying lower TLDFs (range 37.5°C to 38.9°C) versus 39.0°C on these measures was simulated in silicon.ResultsIn reality, 45 FN episodes were diagnosed. Of 3391 temperatures measured, 193 were ≥39.0°C, and 937 ≥38.0°C. For persisting fever ≥24 hours, additional blood cultures were taken in 31 (69%) episodes in reality. This number decreased to 22 (49%) when applying 39.0°C, and increased to 33 for 38.0°C (73%; plus 11 episodes; plus 24%). For persisting fever ≥48 hours, i.v.-antibiotics were escalated in 25 (56%) episodes. This number decreased to 15 (33%) when applying 39.0°C, and increased to 26 for 38.0°C (58%; plus 11 episodes; plus 24%). For persisting fever ≥120 hours, i.v.-antifungals were added in 4 (9%) episodes. This number increased to 6 (13%) by virtually applying 39.0°C, and to 11 for 38.0°C (24%; plus 5 episodes; plus 11%). The median length of stay was 5.7 days (range, 0.8 to 43.4). In 43 episodes with hospital discharge beyond 24 hours, applying 38.0°C led to discharge delay by ≥12 hours in 24 episodes (56%; 95% CI, 40 to 71), with a median delay of 13 hours, and a cumulative delay of 68 days.ConclusionApplying a low versus standard TLDF led to relevant increases of diagnostics, antimicrobial therapy, and length of stay. The differences between management in reality versus simply applying 39.0° as TLDF reflect the important impact of clinical assessment.

Integration of DPC and clinical microbiological data in Japan reveals importance of confirming a negative follow-up blood culture in patients with MRSA bacteremia.

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is one of the commonest and most life-threatening of all infectious diseases. The morbidity and mortality rates associated with MRSA bacteremia are higher than those associated with bacteremia caused by other pathogens. A common guideline in MRSA bacteremia treatment is to confirm bacteremia clearance through additional blood cultures 2-4 days after initial positive cultures and as needed thereafter. However, no study has presented statistical evidence of how and to what extent confirming a negative follow-up blood culture impacts clinical outcome. We present this evidence for the first time, by combining clinical microbiological data of blood cultures and the DPC administrative claims database; both had been systematically accumulated through routine medical care in hospitals. We used electronic medical records to investigate the clinical background and infection source in detail. By analyzing data from a university hospital, we revealed how survival curves change when a negative follow-up blood culture is confirmed. We also demonstrated confirmation of a negative culture is significantly associated with clinical outcomes: there was a more than three-fold increase in mortality risk (after adjusting for clinical background) if a negative blood culture was not confirmed within 14 days of the initial positive blood culture. Although we used data from only one university hospital, our novel approach and results will be a basis for future studies in several hospitals in Japan to provide statistical evidence of the clinical importance of confirming a negative follow-up blood culture in bacteremia patients, including those with MRSA infections.

Lactococcus Septicemia With Perihepatic Fluid Collection in End-Stage Renal Disease Patient

A 38 year old African American male presented to the emergency room with complaints of having chills, fever, and shortness of breath. His past medical history was significant for sickle cell disease SS-type, end-stage renal disease dialysis dependent, diastolic congestive heart failure, and hemochromatosis. The patient stated that while receiving dialysis he started having the above symptoms. Blood cultures were taken at the dialysis center, and he was administered vancomycin and gentamicin. His temperature was recorded as 101.1, and he was hypotensive. The patient also admitted to gradual onset of abdominal pain, primarily on the right side and dull in nature;also, he had productive cough and rhinorrhea that started 3 to 4 days prior to admission. Of significance, this patient was in a hospital 2 weeks prior for symptomatic anemia and shortness of breath. He was admitted for severe sepsis perhaps secondary to healthcare-associated pneumonia and transaminitis possibly secondary to hemochromatosis vs hypoperfusion due to sepsis. He received hemodialysis, additional blood cultures were drawn, and placed on broad spectrum antibiotics, which included vancomycin, zosyn, and levofloxacin. Chest x-ray showed cardiomegaly and increased interstitial markings likely related to cardiac decompensation. CT abdomen and pelvis without contrast showed airspace opacity in the right lung base, enlarged liver with nodular contour compatible with cirrhosis, moderate amount of loculated perihepatic collection, and a calcified failed right sided kidney transplant. Laboratory data included a white blood cell count of 62,700, neutrophil percentage of 90.1%, and 14% bands on manual differential. Lactic acid 4.3 mm/l, procalcitonin 91.46 ng/ml, ammonia 64 μM/l. The patient's hepatic panel showed an albumin of 2.7 gm/dl, alkaline phosphatase 193 mu/ml, alanine transaminase 98 mu/ml, aspartate transaminase 242 mu/ml, direct bilirubin 5.9 mg/dl, and total bilirubin 10.9 mg/dl. The patient had a CT-guided drainage of the inferior perihepatic fluid collection. Approximately 200cc of amber colored fluid was removed and a drainage bag was placed. Fluid analysis and chemistries were consistent with exudative process. Infectious diseases was consulted for documented blood culture positivity for Lactococcus and Escherichia coli, with recommendation to continue vancomycin and zosyn, discontinue levofloxacin, and send perihepatic fluid for gram stain, culture, and cytology. The patient's fevers resolved and his white blood cell count continued to trend downwards from a peak of 62, 700. He was transferred from the medical intensive care unit to the medical floor for further management.

Microbiological diagnosis of periprosthetic joint infections

Prosthetic joint infection is a rare but serious complication after arthroplasty, leading to prolonged hospitalization and repeated surgical intervention. In this article, successful strategies for the rapid and accurate microbiological diagnosis of infection are reviewed. In the case of clinical suspicion of a prosthetic joint infection, at least a comprehensive clinical review of the patient's postoperative history, a physical examination, routine blood tests including white cell count, erythrocyte sedimentation rate, and C-reactive protein, and further investigation of the synovial-fluid leukocyte count and microbial culture are needed. Depending of the clinical signs of infection additional blood culture samples should be taken. The gold standard to confirm infection is a surgical procedure with at least 5-6 biopsies from suspected areas for both microbial culture and histopathological examination. Culture results may be negative because of previous antimicrobial therapy, a low number of culturable organisms in biofilm formations, inappropriate culture medium, and prolonged transport time. In any of these conditions, diagnosis with highly sensitive diagnostic techniques such as polymerase chain reaction should be considered for the identification of the causative agent in order to establish the most appropriate antimicrobial treatment options.

Daptomycin in treatment of Methicillin-resistant Staphylococcus aureus diskitis

Sir, Daptomycin is a new lipopeptide antibiotic with potent activity against Methicillin-resistant Staphylococcus aureus. It is a bactericidal agent that has the potential to treat infections caused by multi-drug-resistant gram-positive organisms. Although the mainstay of treatment is based on glycopeptides, treatment with vancomycin is frequently reported as often unsuccessful [1–3]. We describe a case of Methicillin-resistant Staphylococcus aureus (MRSA) diskitis successfully treated with intravenous daptomycin. A 38-year-old man was admitted to our department for lumbar pain and fever. Other surgeons have submitted the patient to surgery for L5-S1 discectomy and they discharged him with empirical treatment of ceftriaxone (2 g/day). At admission to our department, he had no notable examination findings, except for fever of 39.2°C. CT revealed typical findings of diskitis (Fig. 1a) and MRSA was isolated from blood cultures. We did not perform surgical operation and preferred conservative treatment. Because of the patient’s history of vancomycin allergy, daptomycin treatment was initiated (6 mg/kg every 24 h i.v.) and treatment with other antibiotics was discontinued. Erythrocyte sedimentation rates and serum C-reactive protein levels returned to the preoperative levels, within 15 days after the initiation of the treatment. Additional blood cultures showed no growth after antibiotic therapy was initiated, and daptomycin was tolerated by patient without treatment-related adverse events. Results of follow-up cultures showed bacterial eradication, nevertheless, we decided to stop the therapy, when MR and scintigraphy with labeled leucocytes were normal to avoid the return of the infection and we needed to continue the daptomycin therapy for 92 days; he returned to his work, without any residual neurologic deficits (Fig. 1b, c). The usual therapeutic choice in cases of MRSA infections is a glycopeptide with or without rifampin, but increasing evidence indicates decreasing effectiveness of vancomycin for Staphylococcus aureus infection. [1–3]. For patients who develop a reaction to vancomycin, treatment of MRSA infections remains clinically challenging. Daptomycin has potent bactericidal activity against gram-positive bacteria, i.e., concentration-dependent. Unlike agents that are active against the cell wall, daptomycin causes rapid bactericidal activity without cell lysis, which could reduce the release of bacterial molecules and lessen the inflammatory response [1–3]. The US Food and Drug Administration has approved daptomycin for the treatment of complicated skin and skin structure infections caused by susceptible pathogens as well as for bacteremia, including right-sided endocarditis, caused by MRSA [1–4]. Other authors have reported cases of severe myopathy and acute renal failure related to daptomycin [4, 5]. Our case suggests that daptomycin is a safe and effective option for the treatment of MRSA diskitis, without treatment-related adverse events. Fig. 1 a CT showing typical findings of discitis after left interlaminar approach for L5-S1 discectomy. b MR showing no inflammatory findings, after daptomycin therapy. c Scintigraphy with labeled leucocytes showing normal findings, on this data we decided to ...

Bacteraemia and candidaemia: A considerable and underestimated complication of severe rotavirus gastroenteritis

Despite the high incidence of rotavirus gastroenteritis, secondary bacteraemia later in the course of the disease has rarely been reported. To date, the exact incidence of this complication has not been determined. A prospective study was conducted between January 2007 and December 2008 to determine the incidence of bacteraemia by organisms of the normal intestinal flora during severe rotavirus gastroenteritis. Rotavirus gastroenteritis was diagnosed by antigen detection in stool. A previously described 20-point numerical score system was used to determine the severity of disease. There were 289 cases (30%) of rotavirus gastroenteritis during the study period, 106 (36.7%) of which were accepted to be severe rotavirus gastroenteritis and hospitalized. On admission stool and blood cultures tested negative. In cases of persistent or recurrent fever, additional blood cultures were obtained. Among cases with severe rotavirus gastroenteritis, 4 (3.8%) had positive blood cultures (Klebsiella pneumoniae in 1 patient, Escherichia coli in 1 patient, Pseudomonas aeruginosa and Candida albicans in 1 patient, and Candida albicans in 1 patient). All patients were successfully treated with fluid replacement and antimicrobial therapy. Bacteraemia and candidaemia appear to be a considerable and underestimated complication of severe rotavirus gastroenteritis.

Molecular Diagnosis of Infective Endocarditis: A Helpful Addition to the Duke Criteria

Molecular Diagnosis of Infective Endocarditis: A Helpful Addition to the Duke Criteria

Minimizing the Workup of Blood Culture Contaminants: Implementation and Evaluation of a Laboratory-Based Algorithm

An algorithm was implemented in the clinical microbiology laboratory to assess the clinical significance of organisms that are often considered contaminants (coagulase-negative staphylococci, aerobic and anaerobic diphtheroids, Micrococcus spp., Bacillus spp., and viridans group streptococci) when isolated from blood cultures. From 25 August 1999 through 30 April 2000, 12,374 blood cultures were submitted to the University of Iowa Clinical Microbiology Laboratory. Potential contaminants were recovered from 495 of 1,040 positive blood cultures. If one or more additional blood cultures were obtained within +/-48 h and all were negative, the isolate was considered a contaminant. Antimicrobial susceptibility testing (AST) of these probable contaminants was not performed unless requested. If no additional blood cultures were submitted or there were additional positive blood cultures (within +/-48 h), a pathology resident gathered patient clinical information and made a judgment regarding the isolate's significance. To evaluate the accuracy of these algorithm-based assignments, a nurse epidemiologist in approximately 60% of the cases performed a retrospective chart review. Agreement between the findings of the retrospective chart review and the automatic classification of the isolates with additional negative blood cultures as probable contaminants occurred among 85.8% of 225 isolates. In response to physician requests, AST had been performed on 15 of the 32 isolates with additional negative cultures considered significant by retrospective chart review. Agreement of pathology resident assignment with the retrospective chart review occurred among 74.6% of 71 isolates. The laboratory-based algorithm provided an acceptably accurate means for assessing the clinical significance of potential contaminants recovered from blood cultures.

Coagulase-negative staphylococci in multiple blood cultures: strain relatedness and determinants of same-strain bacteremia

The frequency of strain relatedness was determined among randomly selected patients with coagulase-negative staphylococcal infections as determined in multiple blood cultures by plasmid typing, determination of species, and antibiotyping. Strain relatedness was demonstrated in 21 of 47 episodes of bacteremia (44.7%) among 34 patients, with a similar percentage among patients with two or one positive blood culture in 24 h (14 of 30 [46.7%] versus 7 of 17 [41.2%], respectively). Same-strain bacteremia was more frequent in cases of infection among patients with a corresponding fever (15 of 21 [71.4%]), among patients infected with organisms from an identifiable source (7 of 9 [77.8%]) and with non-Staphylococcus epidermidis species (9 of 11 [81.8%]), and among patients with nosocomially acquired infections (18 of 36 [50%]). Comparing episodes with or without strain relatedness, no difference was noted in the time to growth (2.1 +/- 1.4 versus 1.9 +/- 0.9 days, respectively), in bacterial growth in two culture bottles (5 of 14 [35.7%] versus 8 of 24 [33.3%], respectively), and in the presence of additional negative blood cultures (9 of 21 [42.9%] versus 11 of 26 [42.3%], respectively). The antibiotypes of all related strains and 7 of 44 (15.9%) unrelated pairs were identical. These findings demonstrate that coagulase-negative staphylococci from multiple blood cultures are frequently unrelated, suggesting a high prevalence of contamination. In the absence of precise measures for demonstrating strain relatedness, the combination of a clinical assessment with antibiotype determination appears to be a suitable alternative.

Incidence of bacteremia in transesophageal echocardiography: A prospective study of 140 consecutive patients

The incidence of bacteremia related to transesophageal echocardiography was studied in 140 consecutive patients (71 women and 69 men with a mean age of 53.7 ± 15 years). Thirty-four patients had one or more prosthetic heart valves. Blood cultures were obtained from each patient through separate venipuncture sites immediately before and after transesophageal echocardiography. An additional late blood culture was obtained in 114 patients 1 h later. The skin was cleaned with povidone-iodine and venipunctures were performed with separate butterfly needles with use of sterile gloves and drapes. Blood samples were drawn into separate syringes, transferred to aerobic and anaerobic culture bottles and processed with use of a semiautomated system.The overall incidence of blood cultures positive for bacteremia was 2% (8 of 394 bottles) and all positive cultures grew in a single blood culture bottle. Positive cultures occurred in 4 (1.4%) of 280 bottles before the procedure, in 2 (0.7%) of 280 bottles immediately after the procedure and in 2 (0.9%) of 228 late (1-h) blood culture bottles. Bacterial isolates were coagulase-negative staphylococci (n = 5), Propionibacterium(n = 2) and Moraxella(n = 1). All were considered contaminants. Mean endoscopic time in these patients was not significantly different from that in the other patients. Follow-up of patients with a blood culture positive for bacteremia revealed no clinical evidence of systemic infection.It is concluded that 1) the incidence of bacteremia related to transesophageal echocardiography is very low, and 2) the incidence of blood cultures positive for bacteremia after transesophageal echocardiography is indistinguishable from the anticipated contamination rate.

Blood culture technique: current controversies

Currently controversial questions include: what is the optimal volume of blood for culture and which blood culture system is most suitable for the rapid and reliable detection of important pathogens? The author has discussed these topics and recommends the following: (1) At least 10 ml blood should be cultured for each set from an adult but the maximum possible volume, up to 30 ml, should be cultured. This is especially advisable when febrile immunocompromised patients and patients with infective endocarditis are investigated. (2) The best routine system for obtaining rapid and reliable blood culture results involves the use of two aerobic diphasic media and one anaerobic broth for the culture of 20 ml blood per set. Two blind subcultures are recommended during the first 24 h incubation. This conventional system is impracticable for some laboratories that process enormous numbers of blood cultures and for these laboratories the infrared Bactec system is recommended. (3) An additional blood culture method, such as the lysis-centrifugation system, should be used together with the routine system when clinical circumstances suggest the need to isolate particular 'difficult organisms' and to facilitate the culture of the maximum volume of blood. (4) It is preferable that the routine system includes one bottle without Liquoid as Liquoid-sensitive organisms may otherwise be inhibited even when gelatin is included in the medium.

Occult polymicrobial endocarditis with haemophilus parainfluenzae in intravenous drug abusers

purpose and patients and methods: Fewer than 8 percent of intravenous drug abusers are found to have polymicrobial endocarditis. We report on cases of occult polymicrobial infective endocarditis with Haemophilus parainfluenzae in 10 intravenous drug abusers. Clinical and laboratory data on all 10 patients were obtained from hospital charts, and information on illicit drug use methods was given by five patients. Blood cultures were performed, as wlel as susceptibility testing to antibiotics. Subsequent molecular epidemiologic studies were performed on selected Staphylococcus aureus and H. parainfluenzae strains. Phage typing of S. aureus and biotyping of H. parainfluenzae strains were also done. results: Results of the initial blood cultures were positive on the second to fifth days (mean, 2.6 days), demonstrating a gram-positive pathogen in nine patients and Bacteroides asaccharolyticus in one. Significantly, in each case, H. parainfluenzae alone was subsequently identified from additional blood cultures, with a mean delay of 20.4 days (range, five to 57 days) to the isolation of this organism. Epidemiologic data indicated that our cases did not represent a point-source outbreak. Antibiotic therapy uniformly failed until an agent active against H. parainfluenzae was added. The constellation of clinical, microbiologic, and epidemiologic findings was similar, and permitted prospective diagnosis and therapy in three patients. Despite the absence of S. aureus bacteremia in four, all 10 patients had right-sided endocarditis with septic pulmonary emboli. Five patients had initial blood cultures that were positive for two fucultative gram-positive cocci ( S. aureus and commensal oral streptococcal species). conclusion: Our findings suggest that polymicrobial endocarditis with H. parainfluenzae in intravenous drug abusers is a distinct clinical syndrome, and should be considered in all patients if the response to appropriate antibiotics is atypical or if pulmonary emboli continue with therapy.

Breast milk lymphocyte response to K1 antigen of Escherichia coli.

Comparison milk and blood lymphocyte blastogenic responses to the K1 antigen of Escherichia coli and lipopolysaccharide (LPS) from E. coli O127,B8 were examined in 16 postpartum women by [3H]thymidine uptake. Rabbit hemolysincoated sheep erythrocyte monolayers were used to deplete macrophages from milk lymphocyte preparations and to enrich for T lymphocytes in order to make milk preparations more comparable to blood preparations. Response was defined as a stimulation index of greater than or equal to 2.0. There was no evidence of selective response to K1 antigen by milk lymphocytes, since both blood and milk lymphocytes responded in four women and neither blood nor milk lymphocytes responded in nine. Milk lymphocytes alone responded to K1 in one woman, whereas blood lymphocytes alone responded in two women. Additional nonpaired milk or blood cultures were available from three women. None of these responded to K1 antigen. Corresponding lymphocyte cultures were stimulated with LPS. A positive K1 response was always accompanied by an LPS response, and the LPS response correlated with the K1 response in 17 of 19 women. Stool cultures examined with an antiserum agar showed no correlation between the presence of K1 E. coli in the stool and milk or blood lymphocyte response to K1 antigen. In the system used here, no selectivity of response of breast milk lymphocytes to K1 antigen was noted.