Involvement of curli fimbriae in the biofilm formation of Enterobacter cloacae.

In this study, we examined the biofilm forming ability, the mRNA expression of curli genes and the morphologies of curli fimbriae and biofilms in clinical isolates of Enterobacter cloacae. The csgBA operon was found in 11 (78.6%) of the 14 isolates. The ability of E. cloacae isolates to form biofilms was significantly correlated with the mRNA expression level of the csgA and csgD genes. The curli protein fimbriae appeared as tangled fibers and the curli-proficient strain formed mature biofilms. Our data suggest that the expression of the curli fimbriae play an important role in biofilm formation in E. cloacae.

Antimicrobial susceptibilities and epidemiological analysis of Salmonella enteritidis isolates in Korea by phage typing and pulsed-field gel electrophoresis.

A total of 81 isolates of Salmonella Enteritidis were analyzed by antibiotic susceptibility, phage typing, and pulsed-field gel electrophoresis (PFGE). Thirty-two isolates came from broiler carcasses and pig feces, and 49 isolates were from humans in Seoul and suburbs of Seoul, Korea. Antibiotic resistance was most prevalent among human isolates. Of human isolates, 89.8% were resistant to more than two antibiotics, while 64.7% of poultry isolates and 13.3% of pig isolates showed multiple resistance to more than two antibiotics. The most common phage type (PT) was PT1, followed by PT30 or 33, PT21 and PT20a. The isolates showed six PFGE patterns with XbaI or SpeI digestion, and five PFGE patterns with NotI digestion. But a single pattern, PFGE X1, S1, or N1, was predominant and the rest of the PFGE patterns differed by only one or two bands. Results indicated the spread of a genetically related clone of Salmonella Enteritidis in foods and humans in Korea and that phage typing as well as PFGE may offer an improved level of discrimination for the epidemiological investigation of Salmonella Enteritidis.

Antimicrobial resistance in Salmonella enterica serovars Enteritidis and Typhimurium isolated from animals in Korea: comparison of phenotypic and genotypic resistance characterization.

Fourteen and 22 each of Salmonella Enteritidis and Salmonella Typhimurium (S. Typhimurium) were isolated from animals from 1983 to 1999 in Korea and tested for their antibiotic resistance patterns, phage types and resistance gene patterns. S. Typhimurium isolates were highly resistant to streptomycin, sulfisoxazole and tetracycline, 95, 95 and 86%, respectively. The incidence of multiple antibiotic resistance (resistant to more than two drugs tested) of S. Typhimurium isolates was extremely high (100%) comparing to S. Enteritidis isolates (21%). Two of the five ACSSuT (ampicillin, chloramphenicol, streptomycin, sulfisoxazole and tetracycline) resistant type S. Typhimurium isolates were phage type definitive type 104 (DT104). For the detection of resistance related genes in S. Enteritidis and S. Typhimurium isolates, particularly ACSSuT type S. Typhimurium, antibiotic resistance genes, cmlA/tetR, bla(PSE-1) and bla(TEM), and genus Salmonella specific gene, sipB/C, were amplified using four pairs of primers in a hot-start multiplex polymerase chain reaction (PCR). Two Korean isolates of S. Typhimurium DT104 showed bla(TEM) amplicons instead of bla(PSE-1) for the ampicillin resistance and they were susceptible to florfenicol. The multiplex PCR used in this study was useful in characterization of multiple drug resistant Salmonella isolates, especially ACSSuT type S. Typhimurium, and identification of beta-lactamase gene distribution among Salmonella isolates.