Understanding and Application of Daptomycin-Susceptible Dose-Dependent Category for Enterococcus: A Mixed-Methods Study

Background In 2018, the Clinical Microbiology Laboratory at our institution adopted updated daptomycin Enterococcus–susceptible dose-dependent breakpoints. While the introduction of susceptible dose-dependent (SDD) was intended to guide practice toward optimal dosing, the understanding and application of daptomycin SDD breakpoints for enterococci were unknown. Methods This mixed-methods study combined a clinician survey with a retrospective pre–post prescribing analysis. An 8-question survey was distributed to infectious diseases (ID) and internal medicine (IM) clinicians. A retrospective chart review of hospitalized adults with infections due to Enterococcus spp. was conducted before (pre-SDD) and after (post-SDD) adoption of SDD reporting for enterococci. Results Survey response rates were 40 of 98 (41%) for IM and 22 of 34 (65%) for ID clinicians. ID clinicians scored significantly higher than IM clinicians in knowledge of SDD. Chart review of 474 patients (225 pre- vs 249 post-SDD) showed that daptomycin dosage following susceptibility testing was significantly higher post-SDD compared with pre-SDD (8.5 mg/kg vs 6.4 mg/kg; P < .001) with no difference in empiric dosing (6.3 mg/kg vs 6.2 mg/kg; P = .67). Definitive daptomycin use varied between the pre- and post-SDD periods (35.1% vs 16.9%; P < .001). Conclusions The survey revealed that ID clinicians placed more importance on and had more confidence in the SDD category over IM clinicians. SDD reporting was associated with a change in definitive daptomycin dosing. ID specialist involvement is recommended in the care of infections due to enterococci for which daptomycin is reported as SDD given their expertise.

Antimicrobial Resistance Profile of MDR & Non-MDR Meropenem-Resistant Pseudomonas aeruginosa Isolates of Patients in Intensive Care Unit of Tertiary Hospital

Pseudomonas aeruginosa is one of the gram-negative bacteria that causes infection in the Intensive Care Unit (ICU) which is easily resistant. Patients infected with carbapenem-resistant P. aeruginosa are predicted to have a poor prognosis. This study aims to know the resistance profile of meropenem-resistant P. aeruginosa in the ICU. The results of this study can be used as a measure on the success of antimicrobial resistance control, infection control programs and become a reference for empirical therapy in the ICU. This study used a cross-sectional retrospective descriptive research method and was carried out at the Clinical Microbiology Laboratory of Sanglah Hospital Denpasar for three years, from 2018 to 2020. The results showed 38 of the 93 isolates of P. aeruginosa in the ICU were resistant to meropenem and were derived from sputum and urine. The percentage of meropenem-resistant P. aeruginosa isolates was higher in the multi-drug-resistant group and mostly came from sputum specimens. In 2018, Non-MDR meropenem-resistant P. aeruginosa isolates was that 100% sensitive to all other antibiotics used to treat P. aeruginosa infections, including; ceftazidime, cefepime, ciprofloxacin, gentamicin, amikacin, and piperacillin-tazobactam. In 2019 no meropenem-resistant P. aeruginosa isolates were found. In 2020, its sensitivity to antibiotics ceftazidime and piperacillin-tazobactam was 20.0%, ciprofloxacin 60.0% and to antibiotics gentamicin and amikacin 100%. MDR meropenem-resistant P. aeruginosa isolates in 2018 were still sensitive to ceftazidime (15.4%) and amikacin (69.2%) antibiotics, while in 2019 they were only sensitive to amikacin (37.5%). In 2020, P. aeruginosa isolates were sensitive to the antibiotics ceftazidime and cefepime (11.1%), piperacillin-tazobactam (22.2%), and amikacin (88.9%). Amikacin may be the choice of treatment for MDR meropenem-resistant P. aeruginosa.

A Bacterial Profile of Nosocomial Infections in a Tertiary Care Hospital

Background: Nosocomial infections, may appear either during the hospital stay of the patient or after discharge. Objective: To find out the bacterial profile of nosocomial infections in a tertiary care hospital. Methodology: This cross-sectional study was based on the records of the patients admitted in Ghurki Trust Teaching hospital during the period of January 2016 to December 2017, who developed infections after their hospital admission, and their record was available in the Microbiology section of the Department of Pathology. A total of 1000 complete records of the patients were retrieved. Bacterial culture tests from clinical samples of these patients were performed in the clinical microbiology Laboratory of Lahore Medical and Dental College. Specimens included in this study were urine samples, pus samples from wound discharge, infected implants, and dead necrotic tissue. Data were analyzed using SPSS version 26. Results: Out of 1000 samples, 150 (15%) samples showed positive growth, and among 150 83 (55%) were from females patients. The bacterial profile of these 150 positive samples showed that the most frequently isolated bacteria were Staphylococcus Aureus 45 (30%), MRSA 45 (30%) followed by Klebsiella, 21 (14%), Pseudomonas 15 (10%), E. Coli 12 (8%), Acinetobacter 9 (6%), and Proteus 3 (2%). Conclusion: Staph. Aureus, MRSA, Pseudomonas, Acinetobacter, Klebsiella, E.Coli and Proteus are frequently isolated bacteria from nosocomial infections in our study. Such studies should be done frequently to keep track of bacteria that are prevalent in hospital-acquired infections.

Total Laboratory Automation and Three Shifts Reduce Turnaround Time of Cerebrospinal Fluid Culture Results in the Chinese Clinical Microbiology Laboratory

BackgroundTotal laboratory automation (TLA) has the potential to reduce specimen processing time, optimize workflow, and decrease turnaround time (TAT). The purpose of this research is to investigate whether the TAT of our laboratory has changed since the adoption of TLA, as well as to optimize laboratory workflow, improve laboratory testing efficiency, and provide better services of clinical diagnosis and treatment.Materials and MethodsLaboratory data was extracted from our laboratory information system in two 6-month periods: pre-TLA (July to December 2019) and post-TLA (July to December 2020), respectively.ResultsThe median TAT for positive cultures decreased significantly from pre-TLA to post-TLA (65.93 vs 63.53, P<0.001). For different types of cultures, The TAT of CSF changed the most (86.76 vs 64.30, P=0.007), followed by sputum (64.38 vs 61.41, P<0.001), urine (52.10 vs 49,57, P<0.001), blood (68.49 vs 66.60, P<0.001). For Ascites and Pleural fluid, there was no significant difference (P>0.05). Further analysis found that the incidence of broth growth only for pre-TLA was 12.4% (14/133), while for post-TLA, it was 3.4% (4/119). The difference was statistically significant (P=0.01). The common isolates from CSF samples were Cryptococcus neoformans, coagulase-negative Staphylococcus, Acinetobacter baumannii, and Klebsiella pneumonia.ConclusionUsing TLA and setting up three shifts shortened the TAT of our clinical microbiology laboratory, especially for CSF samples.

377. SARS-CoV-2 Genomic Surveillance Reveals Little Spread Between a Large University Campus and the Surrounding Community

Background Understanding SARS-CoV-2 transmission dynamics is critical for controlling and preventing outbreaks. The genomic epidemiology of SARS-CoV-2 on college campuses has not been comprehensively studied, and the extent to which campus-associated outbreaks lead to transmission in nearby communities is unclear. We used high-density genomic surveillance to track SARS-CoV-2 transmission across the University of Michigan-Ann Arbor campus and Washtenaw County during the Fall 2020 semester. Methods We retrieved all available residual diagnostic specimens from the Michigan Medicine Clinical Microbiology Laboratory and University Health Service that were positive for SARS-CoV-2 from August 16th – November 25th, 2020 (n = 2245). We extracted viral RNA, amplified the SARS-CoV-2 genome by multiplex RT-PCR, and sequenced these amplicons on an Illumina MiSeq. We applied maximum likelihood phylogenetic analysis to whole genome sequences to define and characterize transmission lineages. Results We assembled complete viral genomes from 1659 individual infections, representing roughly 25% of confirmed cases in Washtenaw County across the fall semester. Of these cases, 468 were University of Michigan students. Phylogenetic analysis revealed 203 genetically distinct introductions of SARS-CoV-2 into the student population, most of which were singletons (n = 171) or small clusters of 2 – 8 students. We identified two large SARS-CoV-2 transmission lineages (115 and 73 students, respectively), including individuals from multiple on-campus residences. Viral descendants of these student outbreaks were rare, constituting less than 4% of cases in the community. Conclusion We identified many SARS-CoV-2 transmission introductions into the University of Michigan campus in Fall 2020. While there was widespread transmission among students, there is little evidence that these outbreaks significantly contributed to the rise in COVID-19 cases that Washtenaw County experienced in November 2020. Disclosures Adam Lauring, MD, PhD, Roche (Advisor or Review Panel member) Sanofi (Consultant)

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

Background Serial 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. Methods We 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. Results A 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). Conclusion Findings 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)

6. Staphylococcus aureus in a Single Blood Culture Bottle: Should We be Concerned?

Background Staphylococcus aureus bacteremia (SAB) is common and is characterized by high rates of morbidity and mortality. The clinical importance of a single positive blood culture bottle (SPBCB), however, is poorly defined despite it being a frequent laboratory finding. We therefore examined patients with SPBCB to determine its clinical significance and to understand the rationale of current practice. Methods We performed a retrospective, multicenter study of patients with a SPBCB for S. aureus in initial cultures from January 2019 to December 2019 using data collected from both electronic health records and the clinical microbiology laboratory. Results Overall, 534 patients with SAB were identified, and 118 (22.1%) had a SPBCB. Among SPBCB cases, 106 (89.3%) were classified as clinically significant while 12 were considered contaminated or of unclear clinical significance. Baseline characteristics were similar between the groups (Table 1). A majority (92.4%) received antibiotic therapy, but patients with clinically significant bacteremia were treated with a longer antibiotic course (25.9 vs 5.7 days, p< 0.001). Outcomes between those with SPBCB (contaminant vs clinically significant) were similar (Table 2). Of note, while there was no difference in use of echocardiography based on PREDICT criteria between the clinically significant SPBCB vs. the multiple positive blood culture bottles (MPBC) cohorts (Table 3), significant differences were seen in both frequency of echocardiography (65.1% vs. 84.6%, P< 0.001) and IE diagnosis (3.8% vs. 14.2%, P=0.002) for patients in the SPBCB vs. MPBC groups, respectively. In addition, those with MPBC had higher 90-day, 6-month and 1-year mortality rates. Conclusion SPBCB was documented in almost one-quarter of SAB cases and should trigger a thorough investigation as its associated mortality was high and complications, including IE, occurred. Although some SPBCB cases may represent contamination, antibiotic treatment of SPBCB was commonplace. Patients with clinically significant SPBCB were less likely to undergo echocardiography and had a reduced prevalence of an IE diagnosis as compared to those with MPBC. Patients with SPBCB may have a more favorable long-term prognosis as compared to that in patients with MPBC. Disclosures Muhammad R. Sohail, MD, Medtronic (Consultant)Philips (Consultant) 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