Prevalence of Listeria spp and Listeria monocytogenes in meat and fermented fish in Malaysia.

Fermented fish and meat samples were purchased from supermarket and wet market for microbiological analysis of Listeria species and Listeria monocytogenes contamination. Listeria species were isolated from 17 (73.9%) of 23 samples of imported frozen beef, 10 (43.5%) of the 23 samples of local beef and 14 (56%) of the 25 samples of fermented fish from wet market. Listeria monocytogenes occurred in 15 (75%) of the frozen beef samples, 6 (30.4%) of the 23 samples of local meat and 3 (12%) of the 25 samples from fermented fish. Listeria species was not isolated from any of the 23 samples of imported frozen beef from supermarket and from the 5 samples of buffalo meat examined. This highlights the possibility of Listeria spp or L. monocytogenes to persist in meat and fermented fish in wet market and raises the problem of illness due to the handling and consumption of Listeria-contaminated meat or fermented fish are likely as evidence by the high contamination rates of samples sold at the wet market.

Plasmid-mediated streptomycin resistance of listeria monocytogenes.

A strain of streptomycin-resistant Listeria monocytogenes LM35 isolated from imported frozen beef was examined in this study. In conjugation studies, the L. monocytogenes LM35 strain harbouring two plasmids of 54, 3.0, 2.8 and 2.7 kilobase was used as the donor and streptomycin-sensitive and plasmidless L. monocytogenes LM65 and LM100 strains as the recipients. Streptomycin resistance was transferred to L. monocytogenes LM65 and LM100 strains at frequencies of 3.3 × 10(-8) and 1.2 × 10(-9) per input donor cells, respectively. In both occasions, we also observed the concomitant transfer of the donor's 54 kilobase plasmid. These results suggest that streptomycin resistance in L. monocytogenes LM35 was mediated by the 54 kilobase plasmid.

Rapid isolation and detection of Escherichia coli O157:H7 by use of rainbow agar O157 and PCR assay.

This study has evaluated the use of a commercially available Rainbow agar O157 and polymerase chain reaction (PCR) assays for the detection of Shiga-like toxin producing Escherichia coli and to serotype E. coli O157:H7 from raw meat. The Rainbow agar O157 was found to be selective and sensitive for the screening of the E. coli O157 from artificially and naturally contaminated meat samples. Shiga-like toxin producing E. coli were identified with two primer pairs that amplified fragments of the SLT-I (384 bp) and SLT-II (584 bp). E. coli O157:H7 was serotyped with a primer pair specified for the H7 flagellar gene, which amplify specific DNA fragments (625 bp) from all E. coli O157:H7 strains. The use of Rainbow agar O157 described allows for the presumptive isolation of E. coli O157 in 24 hours. Identification and confirmation of the presumptive isolates as E. coli O157:H7 by PCR assays require additional 6-8 hours. The above-mentioned screening and identification procedures should prove to be a very useful method since it allows for the specific detection of E. coli O157:H7.

Characterization of Vibrio vulnificus isolated from cockles (Anadara granosa): antimicrobial resistance, plasmid profiles and random amplification of polymorphic DNA analysis.

Antibiotic susceptibility, plasmid profiles and random amplification of polymorphic DNA (RAPD) were used to study strains of Vibrio vulnificus isolated from cockles (Anadara granosa). Thirty-six isolates were analyzed. The prevalent biotypes were 1 (72.2% of the isolates) and 2 (27.8%). Among these, 21 strains of biotype 1 and two strains of biotype 2 contained plasmid DNA bands ranging in size from 1.4 to 9.7 MDa. Thirty-one (83.3%) were found to be resistant to one or more of the antimicrobial agents tested, however no specific correlation between antimicrobial resistance patterns and a single biotype was found. In addition, no particular plasmid profile was predictive of a particular pattern of antibiotic susceptibility. Two primers produced polymorphisms in all strains tested, producing bands ranging from 0.25 to 2.7 kb, indicating a high variability among both biotype 1 and biotype 2 of the V. vulnificus strains investigated. RAPD identity across biotypes was also observed among Vibrio vulnificus strains.