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We evaluated the performance and cost-effectiveness of a matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based Biotyper system for the routine identification of common enteric bacterial pathogens seen in middle Tennessee from suspicious colonies grown on selective stool culture media. A total of 304 suspicious colonies were selected and further identified from 605 stool specimens. The suspicious colonies were analyzed by the Biotyper system, and the results were compared to those from routine phenotypic methods, which identified 22 Salmonella species, 39 Shigella species, 3 enterohemorrhagic Escherichia coli (EHEC) isolates, 2 Yersinia enterocolitica isolates, 2 Campylobacter species, and 236 gastrointestinal normal flora isolates. The Biotyper system correctly identified the Salmonella species, Yersinia enterocolitica, and Campylobacter species but failed to distinguish the Shigella species and EHEC isolates from E. coli. Among the 236 normal flora isolates, 233 (98.7%) and 228 (96.6%) agreed at the genus and species levels, respectively, between the phenotypic and Biotyper methods. Organism identification scores were insignificantly different between colonies directly from selective media and subsequently from pure subculture. The entire Biotyper identification procedure, from smear preparation to final result reporting, can be completed within 30 min. The Biotyper system provides a rapid and simple screening tool for identifying many, but not all, suspicious colonies grown on selective media within 24 h after inoculation, which shortens test turnaround time by 2 to 3 days.

Antimicrobial susceptibility patterns, Panton-Valentine leukocidin (PVL) occurrence, and staphylococcal cassette chromosome mec (SCCmec) types in methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from children and adults at Vanderbilt University Medical Center during a 12-month period were evaluated. A total of 1,315 MRSA isolates were collected, of which 748 (36.7%) were recovered from children. Among all isolates, 448 (34.1%) were SCCmec-II, and 847 (64.4%) were SCCmec-IV. More SCCmec-IV isolates were recovered from children than SCCmec-II isolates (424 [50.1%] versus 50 [11.2%]; odds ration [OR]=7.98; P<0.000001). The PVL gene was detected in 93.6% of SCCmec-IV isolates, in contrast to 0.2% in SCCmec-II isolates. Within SCCmec-IV isolates, a statistically higher PVL occurrence was noticed in children (98.1%) than in adults (89.1%) (OR=6.34; P<0.000001). Overall, SCCmec-II strains showed greater resistance than SCCmec-IV strains to clindamycin, erythromycin, levofloxacin, gentamicin, rifampin, minocycline, and trimethoprim-sulfamethoxazole. Both SCCmec-II and SCCmec-IV strains recovered from adults were more resistant to these antibiotics than those recovered from children. SCCmec-II strains were predominantly recovered from the respiratory tract, whereas SCCmec-IV strains were predominantly recovered from skin, soft tissue, abscesses, and surgical wounds. These data indicate that SCCmec-IV MRSA isolates frequently infect children in middle Tennessee and are likely to harbor the PVL gene.

Background: Reports from various geographic regions indicate that the prevalence of community-acquired methicillin-resistant (MRSA) infection is increasing. The primary reservoir is the anterior nares; nasal carriage is a risk factor for infection in a variety of populations. Little is known about MRSA nasal carriage rates among children in Nashville, TN and the associated likelihood of community MRSA transmission., Methods: Nasal swabs were collected from 500 children at well-child visits at either a university hospital pediatric clinic or a private pediatric office. Cultures were plated onto selective staphylococcal media, with or without oxacillin. isolates were confirmed by coagulase tube testing. Antibiotic susceptibilities were determined for suspected methicillin-resistant isolates by standard broth microdilution methods (National Committee for Clinical Laboratory Standards). Pulsed field gel electrophoresis was used to evaluate epidemiologic relatedness. PCR testing was done to assess for the gene. A parent questionnaire was administered regarding MRSA risk factors., Results: Four patients had oxacillin-resistant isolates (MIC >or= 4 microg/ml), and two had borderline resistant isolates (MICs = 1 and 2 microg/ml). One of the borderline-resistant isolates and one of the MRSA isolates had pulsed field gel electrophoresis typing results indicating close relatedness. The gene was present in all resistant isolates and one of the borderline-resistant isolates. Only having a household member employed in a hospital was associated with a greater risk of MRSA nasal carriage (odds ratio, 9.6; P= 0.008)., Conclusions: MRSA nasal colonization is present within Nashville's healthy pediatric population. Children with household contacts employed in a hospital are significantly more likely to be colonized.

The clinical and molecular epidemiology of penicillin-resistant Streptococcus pneumoniae and the diagnostic accuracy of a six-primer PCR assay in identifying penicillin resistance were analyzed by using clinical isolates recovered over a 10-year period in middle Tennessee. The prevalence of non-penicillin-susceptible S. pneumoniae isolates (MIC, > or =0.1 microg/ml) increased from 10% in 1990 to 70% in 1999 (P < 0.001). Among S. pneumoniae isolates for which the penicillin MIC was > or =2 microg/ml (highly penicillin-resistant S. pneumoniae [PRSP]), 23 and 5% were resistant to at least three and at least five other antimicrobial classes, respectively. Pulsed-field gel electrophoresis identified 13 unique strain types, with type B accounting for 33% of PRSP isolates. The sensitivity, specificity, and negative and positive predictive values of the PCR assay in detecting PRSP were 99, 100, 99, and 100%, respectively. Penicillin resistance is rapidly increasing among S. pneumoniae isolates in Tennessee. The simultaneous detection of S. pneumoniae and high-level penicillin resistance can be accurately performed with the six-primer PCR assay.