Food-borne pathogens are a serious human health concern worldwide, and the emergence of antibiotic-resistant food pathogens has further confounded this problem. Once-highly-efficacious antibiotics are gradually becoming ineffective against many important pathogens, resulting in severe treatment crises. Among several reasons for the development and spread of antimicrobial resistance, their overuse in animal food production systems for purposes other than treatment of infections is prominent. Many pathogens of animals are zoonotic, and therefore any development of resistance in pathogens associated with food animals can spread to humans through the food chain. Human infections by antibiotic-resistant pathogens such as Campylobacter spp., Salmonella spp., Escherichia coli and Staphylococcus aureus are increasing. Considering the human health risk due to emerging antibiotic resistance in food animal–associated bacteria, many countries have banned the use of antibiotic growth promoters and the application in animals of antibiotics critically important in human medicine. Concerted global efforts are necessary to minimize the use of antimicrobials in food animals in order to control the development of antibiotic resistance in these systems and their spread to humans via food and water.

Bacterial pathogens as causative agents of infection constitute an alarming concern in the public health sector. In particular, bacteria with resistance to multiple antimicrobial agents can confound chemotherapeutic efficacy towards infectious diseases. Multidrug-resistant bacteria harbor various molecular and cellular mechanisms for antimicrobial resistance. These antimicrobial resistance mechanisms include active antimicrobial efflux, reduced drug entry into cells of pathogens, enzymatic metabolism of antimicrobial agents to inactive products, biofilm formation, altered drug targets, and protection of antimicrobial targets. These microbial systems represent suitable focuses for investigation to establish the means for their circumvention and to reestablish therapeutic effectiveness. This review briefly summarizes the various antimicrobial resistance mechanisms that are harbored within infectious bacteria.

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This study was conducted to understand the seasonal distribution of Vibrio vulnificus in oysters from two estuaries and the effect of environmental factors on the abundance of V. vulnificus in tropical waters. V. vulnificus was detected in 56.6% of the samples tested by colony hybridization with an alkaline phosphatase-labeled oligonucleotide probe (VV-AP), and the counts ranged from <10/g during the summer months to 10 3 /g in the monsoon season at both sites. The density of V. vulnificus appeared to be controlled more by salinity than by temperature. A nested PCR used in this study detected V. vulnificus in 85% of the samples following 18 h of enrichment in alkaline peptone water.Vibrio vulnificus is widely distributed in coastal and estuarine waters throughout the world (3,18). This opportunistic pathogen has been identified as being capable of causing life-threatening septicemia and wound infections in individuals with underlying debilitations such as chronic liver disease and in immunocompromised individuals, being responsible for more than 95% of seafood-associated deaths. Infection with V. vulnificus occurs by the ingestion of raw or undercooked shellfish, particularly oysters, or by direct entry through wounds (13,19).The ecology of V. vulnificus in temperate waters has been well studied. The salinity and temperature of water strongly influence the density of V. vulnificus (12,17,24). Low salinities (5 to 25 ppt) and warm temperatures (20 to 35°C) have been reported to be favorable for this organism. The optimum salinity range is 5 to 25 ppt (17), although it has been isolated from waters with salinities ranging from 1 to 34 ppt. Several studies have linked the abundance of V. vulnificus in oysters to warmer temperatures (20 to 35°C) and low-to-moderate salinity (7 to 16 ppt) (11,12,20,24).Very few studies on the prevalence of V. vulnificus in tropical waters such as those of India have been carried out (8,9,25), and these were based on conventional isolation and identification methods. There is very little information on the abundance and ecology of this organism in tropical waters. Direct enumeration of V. vulnificus in seafoods is greatly facilitated by the use of oligonucleotide probes. Wright et al. (26,27) described a colony hybridization assay for the enumeration of V. vulnificus with an alkaline phosphatase-labeled oligonucleotide probe (VV-AP). The objectives of the present study were to determine the densities of V. vulnificus in freshly harvested oysters on the southwest coast of India by colony hybridization with the VV-AP probe and to detect its presence by conventional isolation and direct PCR on enrichment broths. The Food and Drug Administration (5) recommends enrichment in alkaline peptone water (APW), followed by isolation on selective agars, thiosulfate citrate bile salt sucrose (TCBS) agar, and modified cellobiose-polymyxin-colistin (mCPC) agar for detection of V. vulnificus. However, Hoi et al. (7) at two sites (site 1, Sasthan, Udupi District; site 2, Mulki, Mangalore District) tha...

Pathogenic microorganisms that are multidrug-resistant can pose severe clinical and public health concerns. In particular, bacterial multidrug efflux transporters of the major facilitator superfamily constitute a notable group of drug resistance mechanisms primarily because multidrug-resistant pathogens can become refractory to antimicrobial agents, thus resulting in potentially untreatable bacterial infections. The major facilitator superfamily is composed of thousands of solute transporters that are related in terms of their phylogenetic relationships, primary amino acid sequences, two- and three-dimensional structures, modes of energization (passive and secondary active), and in their mechanisms of solute and ion translocation across the membrane. The major facilitator superfamily is also composed of numerous families and sub-families of homologous transporters that are conserved across all living taxa, from bacteria to humans. Members of this superfamily share several classes of highly conserved amino acid sequence motifs that play essential mechanistic roles during transport. The structural and functional importance of multidrug efflux pumps that belong to the major facilitator family and that are harbored by Gram-negative and -positive bacterial pathogens are considered here.