Evaluation and use of a rapid Staphylococcus aureus assay by an antimicrobial stewardship program.

PURPOSE: The performance of a rapid test for methicillin-resistant Staphylococcus aureus (MRSA) in a large community hospital was investigated. METHODS: A prospective observational study was conducted to evaluate an immunochromatographic assay (Alere PBP2a Culture Colony Test, Alere Scarborough, Inc.) for rapid differentiation of MRSA and methicillin-susceptible S. aureus (MSSA) strains using isolates cultured overnight on common laboratory media. S. aureus isolates cultured for 12-24 hours were tested with the assay, which detects penicillin-binding protein 2a (PBP2a) and provides results in six minutes. The test results were compared with data from standard overnight antimicrobial susceptibility testing to determine the assay's sensitivity and specificity. Changes in therapy associated with use of the rapid assay were evaluated. RESULTS: Over an 11-month period, 661 inpatient isolates from mostly nonhematologic sites were tested. There were six false-negative results, indicating assay sensitivity of 98.4%, with no false positives (specificity of 100%). Eight invalid test results were documented. During designated evaluation periods, a total of 169 patient cases involving PBP2a testing were reviewed by the hospital's antimicrobial stewardship pharmacist. In 63 of those cases (37%), changes in therapy were implemented on the day of test result posting. Interventions often involved switching patients from inappropriate to appropriate MRSA therapy or optimizing MRSA- or MSSA-targeted therapy. CONCLUSION: An assay for quickly differentiating between MRSA and MSSA was highly sensitive, highly specific, and inexpensive in actual hospital use and led to rapid prescription of appropriate antistaphylococcal therapy 24-48 hours after culture specimens were collected.

Evaluation of the BinaxNOW Staphylococcus aureus test for rapid identification of Gram-positive cocci from VersaTREK blood culture bottles.

The ability of the rapid BinaxNOW Staphylococcus aureus (BNSA) immunochromatographic test (Alere Scarborough, Inc., ME) to accurately differentiate S. aureus from coagulase-negative staphylococci (CoNS) and other Gram-positive cocci (GPC) directly from VersaTREK blood culture bottles was evaluated. A total of 319 positive patient blood culture bottles with GPC seen in clusters with Gram staining were tested using the BNSA test and a direct tube coagulase test (DTCT). The BNSA test was accurate for the detection and differentiation of S. aureus from CoNS and other GPC within 30 min from the time of blood culture positivity and demonstrated a test sensitivity and specificity of 95.8% and 99.6%, respectively. BNSA test results were faxed to the antimicrobial stewardship pharmacist by noon each day in order to evaluate empirical antimicrobial therapy and facilitate more rapid changes or modifications if necessary. Same-day reporting of BNSA test results in conjunction with an antimicrobial stewardship program was more impactful in improving treatment for inpatients with documented S. aureus bacteremia than in reducing empirical vancomycin use in inpatients with CoNS during the first 24 h following reporting.

Identification and characterization of plasmid-borne erm(T) macrolide resistance in group B and group A Streptococcus.

One hundred and seven group B Streptococcus (GBS) isolates and 344 group A Streptococcus (GAS) isolates were collected between 2005 and 2009 from 2 area hospitals and studied for resistance to erythromycin (ERY) and clindamycin (CLI) and the presence of the erm(T) macrolide resistance gene. The erm(T) gene was found in 5 (8%) of 61 erythromycin nonsusceptible GBS isolates and in 22 (55%) of 40 erythromycin nonsusceptible GAS isolates. The erm(T) gene in all 27 GBS/GAS erm(T) gene-positive isolates was located on a plasmid. Three erm(T) gene-positive plasmids were DNA sequenced. Two plasmids (1 each from GBS and GAS isolates) were both 4967 bp in size, contained the erm(T) gene, and differed by only 2 base pairs, suggesting interspecies horizontal transfer of the erm(T) gene containing plasmid. The third (GBS) plasmid was 6825 bp in size and contained GBSi1, a group II bacterial intron, as well as the erm(T) gene. Pulsed-field gel electrophoresis of all 27 erm(T) gene containing isolates and a selection of erm(T) gene-negative isolates indicated possible clonal expansion among erm(T) gene containing GAS isolates, but not among the 5 erm(T) gene-positive GBS isolates.

Alternative use for spectra MRSA chromogenic agar in detection of methicillin-resistant Staphylococcus aureus from positive blood cultures.

Spectra MRSA agar (Remel, Lenexa, KS), a novel chromogenic medium originally developed to detect methicillin-resistant Staphylococcus aureus (MRSA) from nasal swabs, was evaluated in this multicenter study for the detection of MRSA from positive blood cultures exhibiting Gram-positive cocci upon initial Gram staining.

First descriptions of blaKPC in Raoultella spp. (R. planticola and R. ornithinolytica): report from the SENTRY Antimicrobial Surveillance Program.

Two strains of Raoultella planticola and one of Raoultella ornithinolytica showing carbapenem resistance were recovered from patients hospitalized in New Jersey and Ohio. All patients had received previous antimicrobial treatment, including carbapenems. These strains harbored bla(KPC-2) and bla(KPC-3). Carbapenemase genes were embedded in isoforms of Tn4401 and were plasmidic and chromosomal in location.

Prevalence of the erm(T) gene in clinical isolates of erythromycin-resistant group D Streptococcus and Enterococcus.

Among 48 erythromycin-resistant group D streptococci (GDS), 36 had the erm(T) resistance gene. erm(T) was also found in 4 of 31 erythromycin-resistant Enterococcus faecium isolates. This is the first report of the erm(T) gene in U.S. GDS isolates and the first report of the erm(T) gene in enterococci.

Emergence of resistant Acinetobacter baumannii in critically ill patients within an acute care teaching hospital and a long-term acute care hospital.

BACKGROUND: Acinetobacter baumannii is a gram-negative, coccobacillus found in water and is a significant nosocomial pathogen in hospitals. This report chronicles the appearance in June 2003 of a multidrug-resistant A baumannii (MDR-AB) strain, its dissemination, and interventions used to control it in an acute care hospital (ACH) and long-term acute care facility (LTAC). METHODS: Molecular typing using pulsed-field gel electrophoresis (PFGE) showed that 88 of 99 strains (89%) gave an identical banding designated as clone A. Eight additional isolates were variants of clone A, and 3 isolates were unrelated. RESULTS: A baumannii was isolated from 229 patients between January 2003 and December 2004. Of these patients, 151 (66%) were colonized/infected with MDR-AB. Most isolates were resistant to antibiotics except for imipenem and ampicillin/sulbactam. Isolates included 108 (72%) in the respiratory tract, 32 (21%) in wounds, 6 (4%) in blood, and 5 (3%) in urine. Most isolates were found in the LTAC (70 isolates), ICU step-down (27 isolates), and ICU (26 isolates). CONCLUSION: This epidemiologic history illustrates (1) epidemic clonal spread, (2) target populations, (3) variable monthly prevalence, and (4) intervention outcomes. With intervention, the number of new isolates in the ACH decreased by dedicating an infection control professional to critical care, daily surveillance, isolation of positive MDR-AB patients, universal gloving, and routinely reporting results.

Regional variations in multidrug resistance among Enterobacteriaceae in the USA and comparative activity of tigecycline, a new glycylcycline antimicrobial.

We report here on the activity of tigecycline and comparators against multidrug-resistant (resistant to >or=3 antimicrobial classes; MDR) Enterobacteriaceae from the USA collected between January 2004 and January 2006 as part of the Tigecycline Evaluation and Surveillance Trial (TEST). Nationally, 131 (5.9%) Escherichia coli, 174 (10.1%) Klebsiella pneumoniae, 4 (1.2%) Klebsiella oxytoca, 24 (4.9%) Enterobacter aerogenes, 126 (9.5%) Enterobacter cloacae and 20 (2.6%) Serratia marcescens isolates were MDR. Four isolates (two K. pneumoniae and two E. cloacae) were resistant to nine antimicrobials. Tigecycline performed well against MDR E. coli (MIC(90) 0.5 microg/mL, 0% resistant) and K. pneumoniae (MIC(90) 4 microg/mL, 9.2% resistant). A MIC(90) of 8 microg/mL was reported for tigecycline against the other MDR organisms studied here, notably lower than those of most comparators.

Identification of an erm(T) gene in strains of inducibly clindamycin-resistant group B Streptococcus.

Five inducibly clindamycin (CLI)-resistant group B Streptococcus (GBS) isolates, all negative for erm(A) and erm(B) genes, were found to contain erm(T), a gene previously reported in erythromycin-resistant animal isolates of Lactobacillus spp. and human isolates of Streptococcus bovis. One additional GBS isolate, constitutively resistant to CLI, was also positive for the erm(T) gene in addition to erm(B). To our knowledge, this is the 1st report of erm(T) in GBS, the 2nd bacterial species from humans in which the erm(T) gene has been identified, and the 3rd erm gene to be found in GBS.

Rise of Streptococcus pneumoniae isolates containing both erm(B) and mef(E) genes from an adult tertiary care community hospital system.

The emergence of macrolide- and lincosamide-resistant Streptococcus pneumoniae is a worldwide concern. Of particular interest is the increasing prevalence of erythromycin and clindamycin-resistant isolates containing both erm(B) and mef genes. This study determined the prevalence of erythromycin and clindamycin resistance in 596 clinical S. pneumoniae isolates from 2 adult tertiary care hospitals over a 4-year period (2001-2004). Erythromycin resistance increased from 24% to 34%, but S. pneumoniae isolates resistant to clindamycin as well as to erythromycin increased from 3% in 2001 to 15.5% in 2004 (5-fold increase). Among erythromycin-resistant isolates, those also resistant to clindamycin (MLS(B) phenotype) increased 3-fold (12.8-45%). Of forty-one erythromycin/clindamycin-resistant S. pneumoniae isolates tested, 29 (71%) contained both erm(B) and mef(E) genes. Pulsed-field gel electrophoresis performed on 28 erm(B) + mef(E) positive isolates identified 2 predominant and possibly related clones, which made up 64% of the isolates.

High rates of erythromycin and clindamycin resistance among OBGYN isolates of group B Streptococcus.

In vitro susceptibility testing on 200 Streptococcus agalactiae strains isolated during a 4-year period from vaginal/rectal specimens demonstrated a very high resistance rate for both erythromycin (54%) and clindamycin (33%). Methylase genes erm(B) and erm(TR) and efflux genes mef(E) and mef(A) were detected. Pulsed-field gel electrophoresis showed evidence of both clonal spread and multiclonal dissemination of resistant strains. All but 3 of 200 isolates were susceptible to telithromycin.

Evolution and dissemination of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae: epidemiology and molecular report from the SENTRY Antimicrobial Surveillance Program (1997-2003).

During 2001, occurrences of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates were detected in a single medical center (Hospital A) from the SENTRY Antimicrobial Surveillance Program that became endemic in long-term acute care areas and in the intensive care unit in 2002-2003. Between 2001 and 2003, 123 patients were infected or colonized with ESBL-positive K. pneumoniae. Resistance profiles were determined by reference broth microdilution methods, and automated ribotyping and pulsed-field gel electrophoresis (PFGE) were performed. The ESBL-positive K. pneumoniae isolates were resistant to aztreonam, ceftazidime, aminoglycosides, and trimethoprim/sulfamethoxazole and susceptible to ciprofloxacin and tetracycline. In 1997, 1998, and 2000, 9 ESBL-producing K. pneumoniae strains from 2 New York City hospitals shared the same antibiograms and ribotype (204.2) as the strains from Hospital A. PFGE patterns divided Hospital A isolates into 2 subtypes (A and A1) and 3 New York City strains were similar to the Hospital A isolates (A2, A3, and A4). Isoelectric focusing studies of 1 New York City isolate (A4) revealed pIs at 5.4, 7.7, and 8.2. PCR and sequencing results from 1 strain of each Hospital A and 1 New York PFGE pattern determined that TEM-1 and SHV-5 (ESBL) were present in all strains. In addition, 2 New York isolates from 1998 (A3 and A4) also had an OXA-2 enzyme. ESBL-producing K. pneumoniae isolates with ribotype 204.2 from SENTRY Program sites have been recognized in New York only since 1997 and in Hospital A beginning in 2001. The similarities of the antibiogram and epidemiological patterns suggest that these isolates have persisted over time and may have evolved into different but genetically related endemic ESBL-positive K. pneumoniae clones that have the ability to cause sustained epidemic outbreaks in US medical centers.

Emergence of levofloxacin-resistant pneumococci in immunocompromised adults after therapy for community-acquired pneumonia.

We describe 4 patients infected with levofloxacin-resistant pneumococci after therapy for community-acquired pneumonia (CAP). The 4 patients had 15 episodes of CAP; Streptococcus pneumoniae was isolated from blood or sputum samples obtained during 14 of the episodes. The underlying medical condition was Bruton agammaglobulinemia in 3 patients and chronic lymphoid leukemia in the other. The initial episode of CAP in each patient was due to a levofloxacin-susceptible strain. One of 4 reinfections and 5 of 6 relapses were due to levofloxacin-resistant strains. All of these strains had amino acid substitutions in the quinolone-resistance-determining region of the genes parC and gyrA. The time between episodes of pneumonia varied from 1 to 4 months. In immunocompromised patients with suspected or proven pneumococcal infection, it may be prudent not to use fluoroquinolone monotherapy empirically when the patient has a history of fluoroquinolone therapy in at least the past 4 months.