Evaluation of the BD GeneOhm StaphSR Assay for Detection of Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Isolates from Spiked Positive Blood Culture Bottles

Abstract Background Empiric antibiotics for foot infections often include coverage of Pseudomonas aeruginosa (PA) and Methicillin-resistant Staphylococcus aureus (MRSA) due to their presumed frequency and ability to cause severe infection. The purpose of this study was to: 1) determine the incidence of PA and MRSA in foot infections; 2) identify variables associated with the presence of PA or MRSA; and 3) examine empiric antibiotic trends for foot infections to determine if empiric coverage of PA and MRSA is warranted. Methods Retrospective study of foot infections at five large urban hospitals in San Diego during 2018. Data were collected from the medical records including demographics, host factors, laboratory data, pathology and imaging data, culture results, and empiric antibiotics. Patients with a foot infection treated as an inpatient in our healthcare system who had a culture collected were included. Results 310 patients with foot infections were included. Mean age was 61.6 years; 220 (71%) were male; 248 (80%) had diabetes; 40 (13%) had end-stage renal disease (ESRD), and 122 (39%) had peripheral arterial disease (PAD). PA was present in 28 (9%) cases. No patient had a positive blood culture for PA. MRSA was present in 55 (18%) cases. Only one patient had a positive blood culture for MRSA. On univariate analysis, wound location not in the forefoot (p=0.047) and presence of PAD (p=0.048) were associated with PA. These failed to remain significant in multivariate analysis (OR=0.42, p=0.074 and OR=2.54, p=0.0504, respectively). Factors associated with MRSA included shallower depth of wound (OR=0.36; p=0.043). 199/310 patients (64%) received empiric antibiotic coverage for PA while 262/310 patients (85%) received empiric MRSA coverage. Of those who received empiric anti-PA coverage, 174 were overtreated (87%). Of those who received empiric anti-MRSA coverage, 218 (83%) were overtreated. Conclusion The incidence of PA in foot infections was overall low, and none had positive blood cultures. MRSA was more often present, however, most patients did not have bacteremia or severe infections. In our study, the majority of empiric anti-PA, as well as anti-MRSA, antibiotic coverage for foot infections was unnecessary questioning the need for upfront, empiric coverage for these pathogens in foot infections. Disclosures All Authors: No reported disclosures

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Use of real-time polymerase chain reaction for identification of methicillin-resistant Staphylococcus aureus directly from positive blood culture bottles

Diagnostic Microbiology and Infectious Disease ◽

10.1016/j.diagmicrobio.2006.12.017 ◽

2007 ◽

Vol 58 (2) ◽

pp. 199-202 ◽

Cited By ~ 11

Author(s):

John Stratidis ◽

Frank J. Bia ◽

Stephen C. Edberg

Keyword(s):

Staphylococcus Aureus ◽

Polymerase Chain Reaction ◽

Blood Culture ◽

Real Time ◽

Positive Blood Culture ◽

Methicillin Resistant Staphylococcus Aureus ◽

Chain Reaction ◽

Methicillin Resistant ◽

Polymerase Chain

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282. Epidemiological Evaluation of Methicillin-Resistant Staphylococcus aureus (MRSA) and Methicillin-Susceptible Staphylococcus aureus (MSSA) Bacteremia: A Comprehensive Cancer Center’s 10-Year Experience

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa439.326 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. S141-S142

Author(s):

Charles R Ford ◽

Ju Hee Katzman ◽

John Greene

Keyword(s):

Staphylococcus Aureus ◽

Blood Culture ◽

Cancer Patients ◽

Positive Blood Culture ◽

Survival Curve ◽

Categorical Variables ◽

Methicillin Resistant ◽

Kaplan Meier ◽

The Mean ◽

Meier Survival Curve

Abstract Background Coagulase-positive Staphylococcus aureus bacteremia among cancer patients carries significant morbidity and mortality. This study aims to compare the risk factors and clinical outcomes among cancer patients diagnosed with bloodstream infection (BSI) with methicillin-sensitive S. aureus (MSSA) or methicillin-resistant S. aureus (MRSA). Methods We performed a retrospective cohort study on all patients diagnosed with an active solid tumor or hematologic cancer with positive blood culture for S. aureus from January 2009 to May 2019. We collected data on demographics, comorbidities, malignancy type, venous access, neutropenia status, echocardiogram results, treatment (tx) duration, antibiotics usage pre/post culture, hospital LOS, infection severity, and 7-day and 30-day mortality. We used the Chi-square test to analyze categorical variables, t-test to analyze continuous variables, and the Kaplan-Meier survival curve and multivariate regression to analyze mortality. Results Two hundred eighty-three cases with malignancies and S. aureus BSIs were reviewed, and 168 were identified with BSIs for MRSA or MSSA during the ten years. The mean age for MRSA cases was 73.1 (±13.7) and 70.1 (± 14.6) for MSSA; male patients were most of the sex (P < 0.01). MRSA and MSSA bacteremia presented equally in hematologic malignancies, while MSSA was observed more in skin cancer than MRSA. Cancers that obstruct GU tracts may be associated with MRSA and MSSA from urine source as both were overrepresented in patients with bladder and rectal cancer. In most patients, the CVC was promptly removed and appropriate antibiotics were given promptly within 1 hour of the positive blood culture. For patients who underwent echocardiogram, most had a negative result in both groups. There was no significant difference for seven and 30-day mortality between the two groups. The mean hospital LOS was longer for MRSA cases (10.5 ± 13.5) versus MSSA cases (4.88 ± 9.1), (P < 0.01). Figures 1 & 2. Kaplan-Meier Survival Curve Comparing 7 and 30-day Mortality of Cancer Patients with MRSA vs MSSA BSI Figure 3 & 4. Distribution of Cancer Types for MRSA (n=84) and MSSA (n=84) BSI Conclusion Endocarditis with either MRSA or MSSA BSI is not a prominent finding among cancer patients at our institution. Given the extensive usage of CVCs and devices in patients with malignancies, prompt removal and antibiotic administration are essential to reduce morbidity; even then, the LOS for MRSA BSI remains longer than MSSA BSI. Disclosures All Authors: No reported disclosures

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301. Penicillin Versus Cefazolin or Anti-staphylococcal Penicillins for Penicillin-Susceptible Staphylococcus aureus Bacteremia

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa439.344 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. S149-S149

Author(s):

Mohammed Aldhaeefi ◽

Jeffrey Pearson ◽

Sanjat Kanjilal ◽

Brandon Dionne

Keyword(s):

Staphylococcus Aureus ◽

Blood Culture ◽

Positive Blood Culture ◽

Medical Center ◽

Academic Medical Center ◽

Similar Distribution ◽

Clinical Failure ◽

Staphylococcus Aureus Bacteremia ◽

Definitive Therapy ◽

Significant Difference

Abstract Background Staphylococcus aureus bacteremia is a significant cause of mortality. Penicillin (PCN) may have a role in the treatment of penicillin-susceptible Staphylococcus aureus (PSSA) bacteremia as it has a narrower spectrum of activity than cefazolin and is better tolerated than antistaphylococcal penicillins (ASPs). The aim of this study is to evaluate the safety and effectiveness of PCN versus cefazolin or ASPs in the treatment of PSSA bacteremia. Methods This is a single-center, retrospective study at a tertiary academic medical center. All patients with a PSSA blood culture from January 1, 2012 to September 1, 2019 were screened. Patients were excluded if they were treated with a definitive antibiotic (defined as antimicrobial therapy received 72 hours after positive blood culture) other than the study comparators, or if they received combination antibiotic therapy >72 hours from the initial positive blood culture result. The primary outcome was 60-day clinical failure, which was a composite endpoint of change in antibiotic after 72 hours of definitive therapy, recurrence of PSSA bacteremia, infection-related readmission, or all-cause mortality. Results Of 277 patients with PSSA bacteremia, 101 patients were included in the study; 62 (61%) were male and 11 (11%) had a β-lactam allergy. At baseline, 40 patients (40%) had hardware, 25 (25%) had an intravenous line, 6 (6%) were on dialysis, and 4 (4%) had active IV drug use, with similar distribution across antibiotic groups. Penicillin was the most common antibiotic used (Table 1). There was a significant difference among groups with respect to the 60-day clinical failure (log-rank p=0.019). In terms of unadjusted 60-day clinical failure, penicillin had similar outcomes to cefazolin (95% CI -0.29 to 0.104, p=0.376), however, it had statistically significant better outcomes in comparison to the ASPs, nafcillin or oxacillin (95% CI 0.023 to 0.482, p=0.031) (Table 1). Table 1. 60-day outcomes of PSSA bacteremia Conclusion Penicillin is effective and safe in the treatment of PSSA bacteremia and may be preferable to antistaphylococcal penicillins Disclosures All Authors: No reported disclosures

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Evaluation of performance of the GENECUBE assay for rapid molecular identification of Staphylococcus aureus and methicillin resistance in positive blood culture medium

PLoS ONE ◽

10.1371/journal.pone.0219819 ◽

2019 ◽

Vol 14 (7) ◽

pp. e0219819 ◽

Cited By ~ 1

Author(s):

Yukio Hida ◽

Keiichi Uemura ◽

Hiroyasu Sugimoto ◽

Yosuke Kawashima ◽

Norito Koyanagi ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Blood Culture ◽

Molecular Identification ◽

Positive Blood Culture ◽

Culture Medium ◽

Methicillin Resistance ◽

Evaluation Of Performance

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Updating Molecular Diagnostics for Detecting Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus Isolates in Blood Culture Bottles

Journal of Clinical Microbiology ◽

10.1128/jcm.01195-19 ◽

2019 ◽

Vol 57 (11) ◽

Cited By ~ 5

Author(s):

Fred C. Tenover ◽

Isabella A. Tickler ◽

Victoria M. Le ◽

Scott Dewell ◽

Rodrigo E. Mendes ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Blood Culture ◽

False Negative ◽

The United States ◽

Molecular Diagnostic ◽

Methicillin Resistant ◽

Content Type ◽

Target Nucleic Acid ◽

Antimicrobial Resistance Genes

ABSTRACT Molecular diagnostic tests can be used to provide rapid identification of staphylococcal species in blood culture bottles to help improve antimicrobial stewardship. However, alterations in the target nucleic acid sequences of the microorganisms or their antimicrobial resistance genes can lead to false-negative results. We determined the whole-genome sequences of 4 blood culture isolates of Staphylococcus aureus and 2 control organisms to understand the genetic basis of genotype-phenotype discrepancies when using the Xpert MRSA/SA BC test (in vitro diagnostic medical device [IVD]). Three methicillin-resistant S. aureus (MRSA) isolates each had a different insertion of a genetic element in the staphylococcal cassette chromosome (SCCmec)-orfX junction region that led to a misclassification as methicillin-susceptible S. aureus (MSSA). One strain contained a deletion in spa, which produced a false S. aureus-negative result. A control strain of S. aureus that harbored an SCCmec element but no mecA (an empty cassette) was correctly called MSSA by the Xpert test. The second control contained an SCCM1 insertion. The updated Xpert MRSA/SA BC test successfully detected both spa and SCCmec variants of MRSA and correctly identified empty-cassette strains of S. aureus as MSSA. Among a sample of 252 MSSA isolates from the United States and Europe, 3.9% contained empty SCCmec cassettes, 1.6% carried SCCM1, <1% had spa deletions, and <1% contained SCCmec variants other than those with SCCM1. These data suggest that genetic variations that may interfere with Xpert MRSA/SA BC test results remain rare. Results for all the isolates were correct when tested with the updated assay.

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2559. Incidence and Clinical Impact of Discordant Genotypic and Phenotypic Categorization of Methicillin Susceptibility in Staphylococcus aureus Bacteremia

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy209.167 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S70-S70

Author(s):

Jessica Gulliver ◽

Brittney Jung-Hynes ◽

Derrick Chen

Keyword(s):

Staphylococcus Aureus ◽

Blood Culture ◽

Positive Blood Culture ◽

Clinical Laboratory ◽

Laboratory Data ◽

Rapid Identification ◽

Clinical Impact ◽

Staphylococcus Aureus Bacteremia ◽

Oxacillin Resistance ◽

Initial Hospitalization

Abstract Background Methicillin-susceptible/methicillin-resistant Staphylococcus aureus (MSSA/MRSA) can be directly identified from positive blood culture bottles using molecular methods. This provides faster results than traditional phenotypic testing, but discrepancies between the two are occasionally found. We sought to determine the incidence and clinical impact of such discrepancies. Methods Positive blood culture bottles are routinely tested in the hospital clinical laboratory for mecA via Xpert MRSA/SA BC (PCR), and antimicrobial susceptibility testing (AST) via MicroScan PC33 is performed on recovered S. aureus isolates; discrepancies between PCR and AST are resolved by repeat and supplemental (Kirby-Bauer) testing. A retrospective review of medical and laboratory data from January 2015 to December 2017 was performed on all patients that had discordant PCR and AST results. Results Approximately 1,200 PCR assays were performed from January 2015 to December 2017, and there were 5 (0.4%) cases with discordant AST Results. Four cases were classified as MSSA by PCR but MRSA by AST, and 1 case was classified as MRSA by PCR but MSSA by AST. For the former group, antimicrobial therapy was changed in 2 patients to cover MRSA and 1 patient was readmitted, while the remaining 2 patients were already being treated for MRSA; for the latter case, this patient was treated for MRSA during the initial hospitalization, but was readmitted with disseminated MSSA and subsequently deceased. Based on genetic targets identified by PCR and cefoxitin and oxacillin AST, discrepancies were likely due to borderline oxacillin resistance (BORSA) (n = 1), presence of an SCCmec variant not detected by PCR (n = 1), or undetermined (n = 3). Conclusion Rapid identification of MRSA bacteremia via PCR provides actionable information to direct empiric treatment. While highly accurate, PCR results are infrequently not corroborated by AST. This rare possibility should be considered when modifying therapy based on initial PCR results, and there should be close communication between the clinical team and laboratory for these challenging cases. Disclosures All authors: No reported disclosures.

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