Detection of mcr-1 Gene in Undefined Vibrio Species Isolated from Clams

Colistin antibacterial activity, clinical effectiveness, and mechanisms of intrinsic and acquired resistance

Following a period of disuse owing to the emergence of multidrug-resistant Gram-negative bacteria, colistin has regained global attention as an antibiotic of last resort. The resurgence in its utilization has led to a concurrent increase in acquired resistance, presenting a significant challenge in clinical treatment. Predominantly, resistance mechanisms involve alterations in the lipid A component of the lipopolysaccharide (LPS) structure. These alterations are facilitated by the addition of cationic phosphoethanolamine (pEtN) or 4-amino-L-arabinose, often driven by the upregulation of two-component regulatory systems such as PmrAB and PhoPQ. Structural components of bacteria, such as capsules and efflux pumps, can also play an important role in the resistance mechanism. In addition to these biochemical modifications, structural components of bacteria like capsules and efflux pumps also play crucial roles in mediating resistance. Another significant mechanism is the acquisition of the plasmid-mediated mobilized colistin resistance (mcr) gene, which poses a global health threat due to its ability to transfer between different bacterial genera. Contemporary strategies to combat colistin resistance include the development and use of novel drugs and inhibitors. To devise effective interventions, it is imperative to first elucidate the precise mechanisms of colistin resistance and determine the roles of various contributing factors.

From tide to table: A whole-year, coastal-wide surveillance of antimicrobial resistance in Escherichia coli from marine bivalves

This work is the first of its kind to report a whole-year and coastal-wide surveillance of antimicrobial resistance (AMR) of Escherichia coli with samples from the EU imposed Norwegian surveillance programme for marine bivalves. In total, 390 bivalve samples collected from January to December in 2016 at 59 different harvest locations, were examined. The occurrence of resistant E. coli in relation to the concentration of E. coli was also analysed. From each sample with E. coli (n = 261), one isolate was susceptibility tested against a panel of 14 antimicrobials from ten classes. The occurrence of resistance to at least one antimicrobial was 8.4 %. Resistance to tetracycline was most commonly detected (5.7 %), followed by resistance to ampicillin (4.6 %) and sulfamethoxazole (3.1 %). The occurrence of extended spectrum cephalosporin (ESC)-resistant E. coli, quinolone-resistant E. coli (QREC) and carbapenem-resistant Enterobacteriaceae (CRE) were detected through selective screening in 3.3 %, 12.8 % and none of the samples, respectively. Among the ESC-resistant E. coli, the blaCTX-M-15 gene was detected in nine isolates, where two isolates also carried the blaCMY-42 gene, followed by blaCTX-M-3 in two and blaCTX-M-1 in one. One isolate was resistant to ESC due to the n.-42C>T mutation in the AmpC gene. Only the presence of QREC clustered significantly (p < 0.013) in space including nine harvest locations. An increased risk (OR 9.4) of detecting ESC-resistant E. coli or QREC was found for samples with E. coli concentrations above the threshold of Class A for direct distribution to the market (i.e. 230 E. coli/100 g). However, five of the ESC-resistant E. coli and 26 of the QREC positive samples, had levels of E. coli below the threshold, thus from areas cleared for sale. Among the 17 ESC-resistant E. coli subjected to whole genome sequencing, two originated from two samples of great scallops and two samples of flat oysters, which are often consumed raw or lightly processed. One of these isolates belonged to the high-risk clone sequence type 131 and carried a plasmid born senB gene encoding the Shigella enterotoxin 2 (ShET2) attributed to cause watery diarrhoea in infections caused by Enteroinvasive E. coli (EIEC). Thus, our study shows that there is a potential risk for transmission of resistant and pathogenic E. coli to the consumers from these products.

Antibiotic resistance and virulence genes profiling of Vibrio cholerae and Vibrio mimicus isolates from some seafood collected at the aquatic environment and wet markets in Eastern Cape Province, South Africa

The current study determines the density of Vibrio spp. and isolates V. cholerae and Vibrio mimicus from fish-anatomical-sites, prawn, crab and mussel samples recovered from fish markets, freshwater and brackish water. Virulence and antibiotic resistance profiling of isolates were carried out using standard molecular and microbiology techniques. Vibrio spp. was detected in more than 90% of samples [134/144] and its density was significantly more in fish than in other samples. Vibrio. cholerae and V. mimicus were isolated in at least one sample of each sample type with higher isolation frequency in fish samples. All the V. cholerae isolates belong to non-O1/non-O139 serogroup. One or more V. cholerae isolates exhibited intermediate or resistance against each of the eighteen panels of antibiotics used but 100% of the V. mimicus were susceptible to amikacin, gentamycin and chloramphenicol. Vibrio cholerae exhibited relatively high resistance against polymyxin, ampicillin and amoxicillin/clavulanate while V. mimicus isolates exhibited relatively high resistance against nitrofurantoin, ampicillin and polymixin. The multiple-antibiotic-resistance-index [MARI] for isolates ranges between 0 and 0.67 and 48% of the isolates have MARI that is >0.2 while 55% of the isolates exhibit MultiDrug Resistance Phenotypes. The percentage detection of acc, ant, drf18, sul1, mcr-1, blasvh, blaoxa, blatem, blaoxa48, gyrA, gyrB and parC resistance-associated genes were 2%, 9%, 14%, 7%, 2%, 25%, 7%, 2%, 2%, 32%, 25% and 27% respectively while that for virulence-associated genes in increasing other was ace [2%], tcp [11%], vpi [16%], ompU [34%], toxR [43%], rtxC [70%], rtxA [73%] and hyla [77%]. The study confirmed the potential of environmental non-O1/non-O139 V. cholerae and V. mimicus to cause cholera-like infection and other vibriosis which could be difficult to manage with commonly recommended antibiotics. Thus, regular monitoring of the environment to create necessary awareness for this kind of pathogens is important in the interest of public health.

Molluscs-A ticking microbial bomb

Bivalve shellfish consumption (ark shells, clams, cockles, and oysters) has increased over the last decades. Following this trend, infectious disease outbreaks associated with their consumption have been reported more frequently. Molluscs are a diverse group of organisms found wild and farmed. They are common on our tables, but unfortunately, despite their great taste, they can also pose a threat as a potential vector for numerous species of pathogenic microorganisms. Clams, in particular, might be filled with pathogens because of their filter-feeding diet. This specific way of feeding favors the accumulation of excessive amounts of pathogenic microorganisms like Vibrio spp., including Vibrio cholerae and V. parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Arcobacter spp., and fecal coliforms, and intestinal enterococci. The problems of pathogen dissemination and disease outbreaks caused by exogenous bacteria in many geographical regions quickly became an unwanted effect of globalized food supply chains, global climate change, and natural pathogen transmission dynamics. Moreover, some pathogens like Shewanella spp., with high zoonotic potential, are spreading worldwide along with food transport. These bacteria, contained in food, are also responsible for the potential transmission of antibiotic-resistance genes to species belonging to the human microbiota. Finally, they end up in wastewater, thus colonizing new areas, which enables them to introduce new antibiotic-resistance genes (ARG) into the environment and extend the existing spectrum of ARGs already present in local biomes. Foodborne pathogens require modern methods of detection. Similarly, detecting ARGs is necessary to prevent resistance dissemination in new environments, thus preventing future outbreaks, which could threaten associated consumers and workers in the food processing industry.