Antimicrobial susceptibility and plasmid-mediated streptomycin resistance of Plesiomonas shigelloides isolated from blue crab

Pathogenomics of Virulence Traits of Plesiomonas shigelloides That Were Deemed Inconclusive by Traditional Experimental Approaches

One of the major challenges of modern medicine includes the failure of conventional protocols to characterize the pathogenicity of emerging pathogens. This is particularly apparent in the case of Plesiomonas shigelloides. Although a number of infections have been linked to this microorganism, experimental evidence of its virulence factors (VFs), obtained by traditional approaches, is somewhat inconclusive. Hence, it remains unclear whether P. shigelloides is a true or opportunistic one. In the current study, four publicly available whole-genome sequences of P. shigelloides (GN7, NCTC10360, 302-73, and LS1) were profiled using bioinformatics platforms to determine the putative candidate VFs to characterize the bacterial pathogenicity. Overall, 134 unique open reading frames (ORFs) were identified that were homologous or orthologous to virulence genes identified in other pathogens. Of these, 52.24% (70/134) were jointly shared by the strains. The numbers of strain-specific virulence traits were 4 in LS1; 7 in NCTC10360; 10 in 302-73; and 15 in GN7. The pathogenicity islands (PAIs) common to all the strains accounted for 24.07% ORFs. The numbers of PAIs exclusive to each strain were 8 in 302-73; 11 in NCTC10360; 14 in GN7; and 18 in LS1. A PAI encoding Vibrio cholerae ToxR-activated gene d protein was specific to 302-73, GN7, and NCTC10360 strains. Out of 33 antibiotic multi-resistance genes identified, 16 (48.48%) genes were intrinsic to all strains. Further, 17 (22.08%) of 77 antibiotic resistance islands were found in all the strains. Out of 23 identified distinct insertion sequences, 13 were only harbored by strain LS1. The number of intact prophages identified in the strains was 1 in GN7; 2 in 302-73; and 2 in NCTC10360. Further, 1 CRISPR element was identified in LS1; 2 in NCTC10360; and 8 in 302-73. Fifteen (78.95%) of 19 secretion systems and secretion effector variants were identified in all the strains. In conclusion, certain P. shigelloides strains might possess VFs associated with gastroenteritis and extraintestinal infections. However, the role of host factors in the onset of infections should not be undermined.

Antibiotic use in animal feed and its impact on human healt

Antibiotic resistance in bacteria that cause disease in man is an issue of major concern. Although misuse of antibiotics in human medicine is the principal cause of the problem, antibiotic-resistant bacteria originating in animals are contributory factors, with some types of resistance in some species of bacteria. Antibiotics are added to animal feeds to treat and prevent infections and to improve growth and production. Until recently, the major concerns about incorporation of antibiotics in animal feeds related to antibiotic residues in products from treated animals. Although, in 1969, the Swann (1969) report drew attention to the potential for antibiotic-resistant bacteria to spread from treated animals via the food chain, there was little response until the detection of vancomycin-resistant enterococci in animals fed a related glycopeptide, avoparcin. Subsequently, attention started to focus on the issue and other examples of transfer of resistant bacteria through the food chain, such as enterococci resistant to quinupristin-dalfopristin or to everninomicin, fluoroquinolone-resistant campylobacters and multiresistant Escherichia coli, and salmonella such as Salmonella typhimurium DT104. Reviews and committees in many countries have highlighted the need for better control of licensing of antibiotics, and codes for prudent use of antibiotics by veterinary practitioners and farmers. The continued use of antibiotic growth promoters has been questioned and there is a need to ensure that antibiotics important in human medicine are not used therapeutically or prophylactically in animals.

Occurrence of Plesiomonas shigelloides in displayed portions of saltwater fish determined by a PCR assay based on the hugA gene

PCR primers were designed and used to amplify a 435-bp fragment from the Plesiomonas shigelloides hugA gene. The PCR assay combined with a non-selective enrichment step proved to be a reliable procedure for P. shigelloides detection in fish meat. The incidence of this bacterium was investigated in 52 lots of pre-packed saltwater fish portions (conger, swordfish, sole, grouper, whiting and halibut) displayed at two hypermarkets by a conventional two-step procedure and the PCR assay. Using the former, P. shigelloides was isolated from three lots of grouper fillets and one lot of halibut fillets. When PCR was performed with non-selective enriched cultures of fish portions, amplification products were obtained from samples that were positive by the culturing method and from eight additional lots of grouper fillets that gave negative results with the conventional procedure. After a secondary enrichment in tetrathionate broth without iodine, all PCR-positive non-selective enrichments yielded P. shigelloides colonies. Overall, P. shigelloides was found in 23% of the examined lots of marine fish (11 of grouper and one of halibut).