Cost-Effective Application of Pulsed-Field Gel Electrophoresis to Typing of Salmonella enterica Serovar Typhimurium

Salmonella enterica serovar Typhimurium is frequently isolated from humans and animals. Phage typing is historically the first-line reference typing technique in Europe. It is rapid and convenient for laboratories with appropriate training and experience, and costs of consumables are low. Phage typing and pulsed-field gel electrophoresis (PFGE) were performed on 503 isolates of serovar Typhimurium. Twenty-nine phage types and 53 PFGE patterns were observed. Most isolates of phage types DT104, DT104b, and U310 are not distinguishable from other members of their phage type by PFGE. By contrast, PFGE of isolates of phage types DT193 and U302 shows great heterogeneity. Analysis of experience with PFGE and phage typing can facilitate the selective application of PFGE to maximize the yield of epidemiologically relevant additional information while controlling costs

Extended-Spectrum β-Lactamases in Ireland, Including a Novel Enzyme, TEM-102

Organisms producing extended-spectrum β-lactamases (ESBLs) have been reported in many countries, but there is no information on the prevalence of ESBL-producing members of the family Enterobacteriaceae in Ireland. A total of 925 isolates of ampicillin-resistant members of the Enterobacteriaceae were received from six hospitals in Ireland over a 3-year period from September 1996 to September 1999. Isolates were screened for ESBL production by the double-disk diffusion (DDD) method. DDD-positive isolates that were (i) confirmed as ESBL producers by National Committee for Clinical Laboratory Standards (NCCLS) confirmatory testing and (ii) susceptible to cefoxitin by disk diffusion were considered ESBL producers. By these criteria, 27 (3%) of the ampicillin-resistant members of the Enterobacteriaceae studied were categorized as ESBL producers. Molecular typing suggested that some intra- and interhospital spread of ESBL-producing isolates had occurred. DNA sequencing of amplified bla(TEM) and bla(SHV) genes resulted in the detection of a novel bla(TEM) ESBL gene, bla(TEM-102) in two isolates (Klebsiella pneumoniae and Enterobacter cloacae) received from the same hospital but isolated from different patients. The study suggests dissemination of ESBL-producing bacteria within the health care system in Ireland and emphasizes the need for measures to control such spread