Biomedical subjects

P Kohner

Publications and source records attributed to P Kohner.

6 recordsLinked to original sources

PubMed2002

Frequency of isolation of Staphylococcus lugdunensis in consecutive urine cultures and relationship to urinary tract infection.

Recent reports associate Staphylococcus lugdunensis with severe infection in humans. The frequency of this microorganism in urine cultures is unknown. Five hundred isolates of coagulase-negative staphylococci (CoNS) were recovered from 4,652 consecutive urine specimens submitted for culture to the Mayo Clinic Microbiology Laboratory. Thirty-one (6%) of 500 isolates of CoNS were identified as S. lugdunensis. In no case was S. lugdunensis isolated in pure culture; 29 (94%) of 31 S. lugdunensis isolates were part of mixed nonpathogenic flora. Medical records were reviewed for 30 of the 31 patients from whom these 31 isolates were isolated. Twenty-one (70%) of the 30 evaluable patients were not treated with antibiotics; the remaining 9 (30%) of 30 patients were treated with antibiotics that may be effective against S. lugdunensis. S. lugdunensis may be an unrecognized yet infrequent cause of urinary tract infection.

Aged↗

PubMed1999

Comparison of susceptibility testing methods with mecA gene analysis for determining oxacillin (methicillin) resistance in clinical isolates of Staphylococcus aureus and coagulase-negative Staphylococcus spp.

Ninety-nine clinical staphylococcal isolates (58 coagulase-negative Staphylococcus spp. [CoNS] and 41 Staphylococcus aureus isolates) were evaluated for susceptibility to oxacillin. The following susceptibility testing methods, media, and incubation conditions were studied: agar dilution by using Mueller-Hinton (MH) medium (Difco) supplemented with either 0, 2, or 4% NaCl and incubation at 30 or 35 degrees C in ambient air for 24 or 48 h; disk diffusion by using commercially prepared MH medium (Difco) and MH II agar (BBL) and incubation at 35 degrees C in ambient air for 24 or 48 h; and agar screen (spot or swab inoculation) by using commercially prepared agar (Remel) or MH agar (Difco) prepared in-house, each containing 4% NaCl and 6 microg of oxacillin/ml (0.6-microg/ml oxacillin was also studied with MH agar prepared in-house for the agar swab method and CoNS isolates) and incubation at 35 degrees C in ambient air for 24 or 48 h for swab inoculation and at 30 or 35 degrees C in ambient air for 24 or 48 h for spot inoculation. The results for these methods were compared to the results for mecA gene detection by a PCR method. Given the ability to support growth and the results for susceptibility testing (the breakpoint for susceptible isolates was </=2 microg/ml), the best methods for CoNS isolates were (i) agar dilution by using MH medium supplemented with 4% NaCl and incubation at 35 degrees C for 48 h (no growth failures were noted, and sensitivity was 97.6%) and (ii) agar screen (swab inoculation) by using MH medium prepared in-house supplemented with 4% NaCl and containing 0.6 microg oxacillin/ml and incubation at 35 degrees C for 48 h (one isolate that did not carry the mecA gene did not grow, and the sensitivity was 100%). All but one (agar dilution without added NaCl and incubation at 30 degrees C for 48 h) of the methods tested revealed all oxacillin-resistant S. aureus isolates, and no growth failures occurred with any method. If the breakpoint for susceptibility was lowered to </=1 microg/ml for agar dilution methods, more CoNS isolates with oxacillin resistance related to the mecA gene were detected when 0 or 2% NaCl agar supplementation was used. Only one CoNS isolate with mecA gene-associated resistance was not detected by using agar dilution and MH medium supplemented with 4% NaCl with incubation for 48 h. When the breakpoint for susceptibility was decreased 10-fold (from 6.0 to 0.6 microg of oxacillin per ml) for the agar swab screen method, fully 100% of the CoNS isolates that carried the mecA gene were identified.

Bacterial Proteins↗

PubMed1998

DNA sequence variation within vanA, vanB, vanC-1, and vanC-2/3 genes of clinical Enterococcus isolates.

We studied the DNA sequence variation of van genes of 34 isolates of Enterococcus spp. The isolates containing the vanB gene exhibited between 0 and 41 base pair changes per 801 bp studied when the vanB sequences were compared to that of the reference strain Enterococcus faecalis V583. The isolates carrying the vanC-2 gene exhibited between 0 and 23 base pair changes per 346 bp studied when the vanC-2 sequences were compared to that of the reference strain E. casseliflavus ATCC 25788. Little variation was noted in the vanA and vanC-1 genes.

Amino Acid Sequence↗

PubMed1998

Determination of 16S rRNA sequences of enterococci and application to species identification of nonmotile Enterococcus gallinarum isolates.

The 16S rRNA sequences of enterococcal species E. faecium, E. faecalis, E. gallinarum, E. casseliflavus/flavescens, E. dispar, E. pseudoavium, E. sulfureus, E. malodoratus, E. raffinosus, E. cecorum, E. hirae, E. saccharolyticus, E. seriolicida, E. mundtii, E. avium, E. durans, E. columbae, and E. solitarius are presented herein. These data were utilized to confirm the species identification of two nonmotile E. gallinarum isolates which had been previously phenotypically identified as E. faecium. The implications of this finding are discussed.

Anti-Bacterial Agents↗

PubMed1997

Comparison of agar dilution, broth dilution, disk diffusion, and the E-test for susceptibility testing of penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae.

An evaluation to determine the optimal methods for the in vitro susceptibility testing of 41 clinical isolates and the ATCC 49619 strain of Streptococcus pneumoniae to penicillin was undertaken. No very major or major interpretive errors were observed with the following test methods and media: agar dilution using either Mueller-Hinton medium with lysed horse blood or Haemophilus test medium; broth dilution using cation-adjusted Mueller-Hinton medium with lysed horse blood, Haemophilus test medium, or Todd-Hewitt medium; and the epsilo-meter test (E-test) using agar containing Mueller-Hinton medium and 5% sheep blood. The disk diffusion method using agar containing Mueller-Hinton medium and 5% sheep blood agar was an effective screening method, requiring confirmation by a dilution susceptibility test method.

Bacteriological Techniques↗

PubMed1997

Multiplex PCR detection of vanA, vanB, vanC-1, and vanC-2/3 genes in enterococci.

Vancomycin-resistant enterococci (VRE) are increasingly isolated from clinical specimens. One hundred clinical isolates of enterococci (E. casseliflavus/E. flavescens [n = 10], E. faecalis [n = 34], E. faecium [n = 43], E. avium [n = 1], E. gallinarum [n = 11], and E. raffinosus [n = 1]) were examined for the presence of vanA, vanB, vanC-1, and vanC-2/3 genes by a single multiplex PCR performed directly with colonies from blood agar plates. Six previously characterized VRE strains which carry either vanA, vanB, vanC-1, or vanC-2 genes were used as controls. To discriminate among van genes, the PCR amplicons were digested with MspI and were electrophoresed on agarose gels. Because of significant sequence homology between vanC-2 and vanC-3 genes, this assay is unable to discriminate these genes from each other; therefore, these are referred to as vanC-2/3 genes. PCR products were detected in 63 of the 100 clinical isolates. The restriction fragment length patterns were consistent with vanA for 10 strains, vanB for 30 strains, vanC-1 for 12 strains, vanC-2 for 6 strains, and vanA and vanC-1 for 1 strain. The vancomycin MICs for the isolates with restriction fragment length patterns consistent with vanA and vanB were all > and = 64 micrograms/ml. The vancomycin MICs for the isolates with restriction fragment length patterns consistent with vanC-1 or vanC-2 were 4 to 8 micrograms/ml. The vancomycin MICs for the isolates from which no PCR amplicons were produced were 2 to 4 micrograms/ml. A PCR product was produced in four isolates (vancomycin MICs, 4 to > 256 micrograms/ml) with restriction fragment length patterns differing from those for the control vanA, vanB, vanC-1, and vanC-2 isolates. DNA sequencing of these amplicons revealed that two of the four isolates had nucleic acid sequences which were closely related to the published sequence for the vanB gene and two had nucleic acid sequences which were closely related to the published sequence for the vanC-2 and vanC-3 genes. Multiplex PCR-restriction fragment length polymorphism appears to be a useful and convenient method for rapidly detecting and discriminating genotypes for vancomycin-resistant Enterococcus spp. in the clinical laboratory. In instances in which unusual restriction fragment patterns of PCR amplicons occur, DNA sequencing can be performed to discriminate van genotypes.

Amino Acid Sequence↗