Molecular biology of extended-spectrum beta-lactamase-producing Enterobacteriaceae responsible for digestive tract colonization.

Twenty-nine extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae strains (14 Klebsiella pneumoniae, 10 Escherichia coli and five Citrobacter diversus) isolated from April to July 1996 from faecal carriers in a surgical intensive care unit at the university hospital of Casablanca (Morocco) were studied. Plasmid content and DNA macrorestriction polymorphism determined by pulsed-field gel electrophoresis (PFGE) were used to compare the strains. Restriction profiles of total genomic DNAs cleaved by XbaI and compared by PFGE revealed nine, four and two clones in K. pneumoniae, E. coli and C. diversus, respectively. Plasmid profile analysis of ESBL-producing strains of K. pneumoniae showed that only seven of 14 isolates had a plasmid; four different plasmid profiles were observed. Three different plasmid profiles were observed in E. coli and two in C. diversus. Plasmids responsible for ESBL production could be transferred by conjugation to E. coli K(12) J53-2 from all E. coli isolates and from four of seven K. pneumoniae. No plasmid transfer could be obtained from C. diversus strains. Restriction enzyme digests of plasmids from transconjugants (four transconjugants of K. pneumoniae and five transconjugants of E. coli) showed different patterns. In the surgical intensive care unit where the survey was conducted, the dissemination of ESBLs was due to a mix of strain spread and strain diversity rather than to plasmid dissemination.

Serotypes and antimicrobial susceptibility of group B streptococcus isolated from neonates in Casablanca.

The serotypes and the levels of antibiotic resistance of 59 Streptococcus agalactiae isolates from neonates in Casablanca, from February 1992 to July 1997, were studied. Most of the isolates (86.4%) were recovered from early-onset disease. The serotype distribution was as follows: serotype III 39%; serotype Ia 32.2%; and serotype V 10.2%. All strains were susceptible to penicillin G, cefotaxime and ampicillin, whereas 1 strain was resistant to erythromycin. No high level of resistance to gentamicin was detected. A vaccine should comprise the most prevalent serotypes and also provide protection against serotype V disease. The antibiotic susceptibility patterns reported here support the recommended treatment and prophylaxis of invasive group B Streptococcal disease.

Characterization of extended-spectrum beta-lactamase-producing Salmonella typhimurium by phenotypic and genotypic typing methods.

During 1994, 10 isolates of extended-spectrum beta-lactamase-producing Salmonella typhimurium were recovered from children transferred to our hospital from two different centers. Two additional isolates were recovered from two nurses from one of these centers. The aim of this study was to determine if there is any relationship between these isolates. The characterization was done by phenotypic and genotypic methods: biotyping, phage typing, antibiotic susceptibility pattern determination, plasmid analysis, ribotyping (by the four endonucleases EcoRI, SmaI, BglII, and PvuII), pulsed-field gel electrophoresis (PFGE) of genome macrorestriction patterns with XbaI, and randomly amplified polymorphic DNA (RAPD) pattern determination (with the three primers 217 d2, B1, and A3). The same biotype, the same serotype, and an identical antibiotype were found. All isolates were resistant to oxyimino-beta-lactams, gentamicin, tobramycin, and sulfamethoxazole-trimethoprim. All isolates showed an indistinguishable pattern by ribotyping and very similar patterns by PFGE and RAPD. The overall results indicated the spread of a closely related strain of S. typhimurium in children and nurses.