No abstract

PFGE is a useful method for the epidemiological evaluation of staphylococci-associated CAPD infections and should replace older and less accurate methods, such as antibiotic sensitivity patterns. We recommend that CNS isolates from patients with CAPD-associated peritonitis should be saved for future investigations and typing, which would aid in the management of this patient category.

The aim of this study was to develop a simple, reliable, and inexpensive in-house system for routine species identification of staphylococci in clinical practice. The system combines 15 key tests (including carbohydrate fermentation) performed in micro-well strips and antimicrobial disk diffusion susceptibility tests performed on standardised paper disk method antibiotic sensitivity medium agar. Twenty-eight staphylococcal reference strains belonging to 18 different species were correctly identified using this in-house system. A total of 291 clinical staphylococci isolates were evaluated with the in-house system and a conventional identification scheme. The in-house system identified 281 (96.6%) of these 291 isolates. Eleven different species were recognised. The five species most frequently identified were Staphylococcus epidermidis (48.6%), Staphylococcus aureus (27.8%), Staphylococcus haemolyticus (8.2%), Staphylococcus hominis (5.7%), and Staphylococcus warneri (5.3%). There was an agreement of 86.3% between the species identification obtained with the in-house system and the conventional identification scheme. All coagulase-negative isolates initially identified as species other than Staphylococcus epidermidis as well as indistinctly identified isolates were also evaluated with a commercial identification system. The agreement between species identification obtained with the in-house system and the commercial system for 101 identified isolates was 73%. Several isolates that were difficult to distinguish with the conventional scheme and/or the commercial system were identified with the aid of the antimicrobial susceptibility test included in the in-house system. The described test scheme should be of value for identification of clinically significant staphylococci species.

OBJECTIVE: To report an unexpectedly high number of cases of septicemia with Stomatococcus mucilaginosus, and try to identify predisposing factors. METHODS: All blood cultures obtained during 1991--93 from patients treated at the hematologic ward were bacteriologically identified. The medical records of patients with S. mucilaginosus-positive blood cultures were retrospectively reviewed and evaluated. The antibiotic susceptibility pattern and restriction fragment length polymorphism (RFLP) of S. mucilaginosus were tested. RESULTS: S. mucilaginosus blood isolates from patients with hematologic malignancies were found to be as common as isolates of Staphylococcus aureus. Eleven patients with myelogenous leukemia and isolation of S. mucilaginosus from the blood are reported on. One patient had concomitant meningitis. All patients were neutropenic and most had oral mucositis and had been given ciprofloxacin prophylaxis. S. mucilaginosus isolates from these patients were resistant to ciprofloxacin in contrast to isolates from patients who had received other prophylactic regimens and seven isolates found in healthy individuals not recently treated with antibiotics. The resistant S. mucilaginosus were found to be of diverse genetic origin as determined by RFLP. CONCLUSIONS: The appearance of resistant strains during ciprofloxacin prophylaxis may be a predisposing factor for S. mucilaginosus septicemia. There was no evidence of a nosocomial spread of S. mucilaginosus strains.

Forty group B Streptococcus (GBS) isolates obtained from Europe and the United States previously reported to be nontypeable (NT) by capsule serotype determination were subjected to buoyant density gradient centrifugation. From nearly half of the isolates capsule-expressing variants could be selected. For characterization of the remaining NT-GBS isolates, the capsule operon (cps) was amplified by the long-fragment PCR technique and compared by restriction fragment length polymorphism (RFLP) analysis. The patterns from serotype reference isolates (n ‫؍‬ 32) were first determined and used as a comparison matrix for the NT-GBS isolates. Using two restriction enzymes, SduI and AvaII, cluster analysis revealed a high degree of similarity within serotypes but less than 88% similarity between serotypes. However, serotypes III and VII were each split in two distant RFLP clusters, which were designated III 1 and III 2 and VII 1 and VII 2 , respectively. Among the isolates that remained NT after repeated Percoll gradient selections, two insertional mutants were revealed. Both were found in blood isolates and harbored insertion sequence (IS) elements within cpsD: one harbored IS1548, and the other harbored IS861. All other NT-GBS isolates could, by cluster analysis, be referred to different serotypes by comparison to the RFLP reference matrix. In pulsed-field gel electrophoresis of SmaI-restricted chromosomal DNA, patterns from allelic type 1 and 2 isolates were essentially distributed in separate clusters in serotypes III and VII. A covariation with insertion sequence IS1548 in the hylB gene was suggested for serotype III, since allelic type III 1 harboring IS1548 in hylB, clustered separately. The variation in serotype VII was not dependent on the presence of IS1548, which was not detected at any position in the type VII chromosome.