A total of 26 strains of Vibrio cholerae , including members of the O1, O139, and non-O1, non-O139 serogroups from both clinical and environmental sources, were examined for the presence of genes encoding cholera toxin ( ctx A), zonula occludens toxin ( zot ), accessory cholera enterotoxin ( ace ), hemolysin ( hly A), NAG-specific heat-stable toxin ( st ), toxin-coregulated pilus ( tcp A), and outer membrane protein ( omp U), for genomic organization, and for the presence of the regulatory protein genes tcp I and tox R in order to determine relationships between epidemic serotypes and sources of isolation. While 22 of the 26 strains were hemolytic on 5% sheep blood nutrient agar, all strains were PCR positive for hly A, the hemolysin gene. When multiplex PCR was used, all serogroup O1 and O139 strains were positive for tcp A, omp U, and tcp I. All O1 and O139 strains except one O1 strain and one O139 strain were positive for the ctx A, zot , and ace genes. Also, O1 strain VO3 was negative for the zot gene. All of the non-O1, non-O139 strains were negative for the ctx A, zot , ace , tcpA , and tcp I genes, and all of the non-O1, non-O139 strains except strain VO26 were negative for omp U. All of the strains except non-O1, non-O139 strain VO22 were PCR positive for the gene encoding the central regulatory protein, tox R. All V. cholerae strains were negative for the NAG-specific st gene. Of the nine non- ctx -producing strains of V. cholerae , only one, non-O1, non-O139 strain VO24, caused fluid accumulation in the rabbit ileal loop assay. The other eight strains, including an O1 strain, an O139 strain, and six non-O1, non-O139 strains, regardless of the source of isolation, caused fluid accumulation after two to five serial passages through the rabbit gut. Culture filtrates of all non-cholera-toxigenic strains grown in AKI media also caused fluid accumulation, suggesting that a new toxin was produced in AKI medium by these strains. Studies of clonality performed by using enterobacterial repetitive intergenic consensus sequence PCR, Box element PCR, amplified fragment length polymorphism (AFLP), and pulsed-field gel electrophoresis (PFGE) collectively indicated that the V. cholerae O1 and O139 strains had a clonal origin, whereas the non-O1, non-O139 strains belonged to different clones. The clinical isolates closely resembled environmental isolates in their genomic patterns. Overall, there was an excellent correlation among the results of the PCR, AFLP, and PFGE analyses, and individual strains derived from clinical and environmental sources produced similar fingerprint patterns. From the results of this study, we concluded that the non-cholera-toxin-producing strains of V. cholerae , whether of clinical or environmental origin, possess the ability to produce a new secretogenic toxin that is entirely different from the toxin produced by toxigenic V. cholerae O1 and O139 strains. We also concluded that the aquatic environment is a reservoir for V. cholerae O1, O139, non-O1, and non-O139 serogroup strains.

Extracellular vesicles (EV), also known as membrane vesicles, are produced as an end product of secretion by both pathogenic and non-pathogenic bacteria. Several reports suggest that archaea, gram-negative bacteria, and eukaryotic cells secrete membrane vesicles as a means for cell-free intercellular communication. EVs influence intercellular communication by transferring a myriad of biomolecules including genetic information. Also, EVs have been implicated in many phenomena such as stress response, intercellular competition, lateral gene transfer, and pathogenicity. However, the cellular process of secreting EVs in gram-positive bacteria is less studied. A notion with the thick cell-walled microbes such as gram-positive bacteria is that the EV release is impossible among them. The role of gram-positive EVs in health and diseases is being studied gradually. Being nano-sized, the EVs from gram-positive bacteria carry a diversity of cargo compounds that have a role in bacterial competition, survival, invasion, host immune evasion, and infection. In this review, we summarise the current understanding of the EVs produced by gram-positive bacteria. Also, we discuss the functional aspects of these components while comparing them with gram-negative bacteria.

We have developed a hexaplex PCR assay for rapid detection of the virulence and regulatory genes for cholera toxin enzymatic subunit A ( ctxA ), zonula occludens toxin ( zot ), accessory cholera enterotoxin ( ace ), toxin-coregulated pilus ( tcpA ), outer membrane protein ( ompU ), and central regulatory protein ToxR ( toxR ) in Vibrio cholerae and Vibrio mimicus . This hexaplex PCR proved successful in screening pathogenic-toxigenic and nonpathogenic-nontoxigenic V. cholerae and V. mimicus strains from both clinical and environmental sources.

Listeria monocytogenes, a foodborne pathogen is ubiquitous to different environments including the agroecosystem. The organism poses serious public health problem. Therefore, an attempt has been made to gain further insight to their antibiotic susceptibility, serotypes and the virulence genes. Out of the 10 vegetables selected, 6 (brinjal, cauliflower, dolichos-bean, tomato, chappan-kaddu and chilli), 20 isolates (10%) tested positive for L. monocytogenes. The prevalence of the pathogen in the respective rhizosphere soil samples was 5%. Noticeably, L. monocytogenes was absent from only cabbage, broccoli, palak and cowpea, and also the respective rhizospheric soils. The 30 isolates + ve for pathogenicity, belonged to serogroup 4b, 4d or 4e, and all were positive for inlA, inlC, inlJ, plcA, prfA, actA, hlyA and iap gene except one (VC3) among the vegetable isolates that lacked the plcA gene. ERIC- and REP-PCR collectively revealed that isolates from vegetables and their respective rhizospheric soils had distinct PCR fingerprints. The study demonstrates the prevalence of pathogenic L. monocytogenes in the selected agricultural farm samples. The increase in the number of strains resistant to ciprofloxacin and/or cefoxitin seems to pose serious public health consequences.

Staphylococcus aureus, a versatile human pathogen, poses a significant challenge in healthcare settings due to its ability to develop antibiotic resistance and form robust biofilms. Understanding the intricate mechanisms underlying the antibiotic resistance is crucial for effective infection treatment and control. This comprehensive review delves into the multifaceted roles of efflux pumps in S. aureus, with a focus on their contribution to antibiotic resistance and biofilm formation. Efflux pumps, integral components of the bacterial cell membrane, are responsible for expelling a wide range of toxic substances, including antibiotics, from bacterial cells. By actively extruding antibiotics, these pumps reduce intracellular drug concentrations, rendering antibiotics less effective. Moreover, efflux pumps have emerged as significant contributors to both antibiotic resistance and biofilm formation in S. aureus. Biofilms, structured communities of bacterial cells embedded in a protective matrix, enable S. aureus to adhere to surfaces, evade host immune responses, and resist antibiotic therapy. Efflux pumps play a pivotal role in the development and maintenance of S. aureus biofilms. However, the interplay between efflux pumps, antibiotic resistance and biofilm formation remains unexplored in S. aureus. This review aims to elucidate the complex relationship between efflux pumps, antibiotic resistance and biofilm formation in S. aureus with the aim to aid in the development of potential therapeutic targets for combating S. aureus infections, especially those associated with biofilms. The insights provided herein may contribute to the advancement of novel strategies to overcome antibiotic resistance and disrupt biofilm formation in this clinically significant pathogen.