Search

Salmonella and Vibrio species were isolated and identified from Litopenaeus vannamei cultured in shrimp farms. Shrimp samples showed occurrence of 3.3% of Salmonella and 48.3% of Vibrio. The isolates were also screened for antibiotic resistance to oxolinic acid, sulphonamides, tetracycline, sulfamethoxazole/trimethoprim, norfloxacin, ampicillin, doxycycline hydrochloride, erythromycin, chloramphenicol, and nitrofurantoin. Salmonella enterica serovar Corvallis isolated from shrimp showed individual and multiple antibiotic resistance patterns. Five Vibrio species having individual and multiple antibiotic resistance were also identified. They were Vibrio cholerae (18.3%), V. mimicus (16.7%), V. parahaemolyticus (10%), V. vulnificus (6.7%), and V. alginolyticus (1.7%). Farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of shrimp.

Gram negative bacteria, including species of Salmonella, Escherichia, Pseudomonas and Klebsiella, isolated from poultry, were screened for their resistance to the commonly used antibiotics: ampicillin, chloramphenicol, gentamycin, kanamycin, neomycin, polymyxin B, streptomycin and tetracycline. Of the 500 bacteria screened, 351 were found to be resistant to one or more antibiotics at the level of 50 micrograms/ml. Various patterns of antibiotic resistance observed during these studies have been reported.

An R plasmid of Salmonella, RM98, which determines sensitivity ot the phage IKe (IKeS) and confers resistance to ampicillin (Ap), streptomycin (Sm) and tetracycline (Tc) was studied for its genetic properties in Salmonella typhimurium and Escherichia coli, Transduction of RM98 by P22 in Salmonella yielded transductants of which some had acquired all the recognizable markers (Ap, Sm, Tc, IKeS and resistance transfer factor or RTF) associated with RM98. This transduction pattern resembles the P22 transduction pattern of IKe-specific R plasmids: R45, R46, R48, R205 and N3. Preliminary genetic analysis of RM98 has indicated that the determinants of IKeS and RTF are closely linked and the determinants of Ap and Sm are closer to RTF-IKeS than they are to Tc.