Reservoir Of Resistance Determinants Research Articles

Genomic Characterization of Carbapenemase-Producing Enterobacter hormaechei, Serratia marcescens, Citrobacter freundii, Providencia stuartii, and Morganella morganii Clinical Isolates from Bulgaria.

Carbapenemase-producing Enterobacter spp. Serratia marcescens, Citrobacter freundii, Providencia spp., and Morganella morganii (CP-ESCPM) are increasingly identified as causative agents of nosocomial infections but are still not under systematic genomic surveillance. In this study, using a combination of whole-genome sequencing and conjugation experiments, we sought to elucidate the genomic characteristics and transferability of resistance genes in clinical CP-ESCPM isolates from Bulgaria. Among the 36 sequenced isolates, NDM-1 (12/36), VIM-4 (11/36), VIM-86 (8/36), and OXA-48 (7/36) carbapenemases were identified; two isolates carried both NDM-1 and VIM-86. The majority of carbapenemase genes were found on self-conjugative plasmids. IncL plasmids were responsible for the spread of OXA-48 among E. hormaechei, C. freundii, and S. marcescens. IncM2 plasmids were generally associated with the spread of NDM-1 in C. freundii and S. marcescens, and also of VIM-4 in C. freundii. IncC plasmids were involved in the spread of the recently described VIM-86 in P. stuartii isolates. IncC plasmids carrying blaNDM-1 and blaVIM-86 were observed too. blaNDM-1 was also detected on IncX3 in S. marcescens and on IncT plasmid in M. morganii. The significant resistance transfer rates we observed highlight the role of the ESCPM group as a reservoir of resistance determinants and stress the need for strengthening infection control measures.

Comparison of Phenotypic and Genotypic Patterns of Antimicrobial-Resistant Bacteroides fragilis Group Isolated from Healthy Individuals in Vietnam and Japan.

PurposeNormal non-pathogenic flora can harm the host by acting as a reservoir of resistance determinants that are potentially transferable to human pathogens. This study aimed to assess the phenotypic and genotypic antimicrobial susceptibility patterns of the Bacteroides fragilis group (BFG) isolated from healthy individuals in Vietnam and Japan in order to elucidate the prevalence of antimicrobial resistance in human flora in the two economically and geographically different countries.Materials and MethodsBFG was isolated from fecal samples of 80 healthy individuals in Vietnam (n=51) and Japan (n=29). Isolated strains were identified using MALDI-TOF MS, and the minimum inhibitory concentration (MIC) of 18 antibiotics was determined using the agar dilution method. Additionally, 20 antimicrobial resistance genes were detected using standard PCR.ResultsA total of 139 BFG strains belonging to 11 BFG species were isolated from the two countries, with diversity in the prevalence of each species. B. fragilis was not the predominant species. Isolations from Vietnam and Japan showed some similarities in terms of MIC50 values, MIC90 values, and the percentage of resistant strains. However, isolations from Vietnam showed significantly higher resistance to piperacillin, cefmetazole, clindamycin, tetracycline, and minocycline. ErmB, tet36, tetM, nim, catA, and qnrA were not found in either country. CepA was more common in B. fragilis than in non-fragilis Bacteroides. In contrast, cfiA, ermG, mefA, msrSA, tetX, tetX1, bexA, qnrB, and qnrS were found only in non-fragilis Bacteroides. There were differences in the prevalence of ermG, linA, mefA, msrSA, and qnrS between isolates from Vietnam and Japan.ConclusionThis study is the first report on the antimicrobial susceptibility patterns in the BFG isolated from healthy individuals in Vietnam and Japan. Compared to isolations from Japan, isolations from Vietnam showed significantly higher resistance to antimicrobial agents. The distribution of various antibiotic resistance genes also differed between the two countries.

Antibiotic Resistome Associated with Small-Scale Poultry Production in Rural Ecuador

Small-scale poultry farming is common in rural communities across the developing world. To examine the extent to which small-scale poultry farming serves as a reservoir for resistance determinants, the resistome of fecal samples was compared between production chickens that received antibiotics and free-ranging household chickens that received no antibiotics from a rural village in northern Ecuador. A qPCR array was used to quantify antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) using 248 primer pairs; and the microbiome structure was analyzed via 16S rRNA gene sequencing. A large number of ARGs (148) and MGEs (29) were detected. The ARG richness in production chickens was significantly higher than that of household chickens with an average of 15 more genes detected ( p < 0.01). Moreover, ARGs and MGEs were much more abundant in production chickens than in household chickens (up to a 157-fold difference). Production chicken samples had significantly lower taxonomic diversity and were more abundant in Gammaproteobacteria, Betaproteobacteria, and Flavobacteria. The high abundance and diversity of ARGs and MGEs found in small-scale poultry farming was comparable to the levels previously found in large scale animal production, suggesting that these chickens could act as a local reservoir for spreading ARGs into rural communities.

Aeromonas spp. simultaneously harbouring blaCTX-M-15, blaSHV-12, blaPER-1 and blaFOX-2, in wild-growing Mediterranean mussel (Mytilus galloprovincialis) from Adriatic Sea, Croatia

Aeromonas species are becoming renowned as emerging pathogens by increasingly giving rise to a wide spectrum of food and waterborne infections in humans. Another worrisome feature of aeromonads is the growing frequency of antibiotic resistance as a consequence of their prominent diversity in terms of resistance determinants. This study aimed at determining the antimicrobial resistance pattern, prevalence and characterization of acquired β-lactamases, including extended-spectrum-β-lactamases (ESBLs) and AmpC cephalosporinases, as well as the presence of class 1 and 2 integrons, in Aeromonas isolates from wild-growing Mediterranean mussel (Mytilus galloprovincialis) of the eastern coast of Adriatic Sea, Croatia. Isolates were tested for susceptibility to 16 antibiotics and β-lactam/β-lactamase inhibitor combinations. Cephalosporin-resistant isolates were further screened by PCR for genes encoding AmpC (blaFOX, blaCMY, blaMOX, blaLAT, blaBIL, blaDHA, blaACC, blaMIR, blaACT), ESBLs (blaTEM, blaSHV, blaCTX-M, blaPER, blaVEB, blaGES/IBC, blaOXA) and integrases (intI1, intI2, intI3). Location of bla genes was characterized by plasmid DNA fingerprinting and Southern blot hybridization. Plasmids carrying ESBL genes were investigated for transferability by conjugation and PCR-based replicon typed. Out of 147 Aeromonas isolates recovered, 30 (20%) demonstrated multiple resistance profile, with co-resistance most frequently detected against penicillins, piperacillin/sulbactam and tetracycline. ESBL-encoding genes were detected in 21 (13 Aeromonas caviae and 8 Aeromonas hydrophila) isolates, with blaCTX-M-15 gene identified in 19 and blaSHV-12 in 12 isolates. Among them, 10 isolates simultaneously harboured blaCTX-M-15 and blaSHV-12, while 3 isolates additionally carried an AmpC β-lactamase blaFOX-2 gene. blaPER-1 gene was identified in a single isolate also harbouring the blaCTX-M-15 gene. While blaSHV-12 was chromosomally encoded, blaCTX-M-15 was located on conjugative IncFIB-type plasmids of ~40kb in A. caviae isolates. IntI1 and intI2 genes were detected in 57.1% and 33.3% of ESBL-producing isolates.To the best our knowledge, this is the first report of environmental A. caviae isolates producing CTX-M-15, and isolation of SHV-12-producing A. hydrophila and A. caviae strains worldwide. This is also believed to be the first report of the FOX-2, CTX-M-15 and SHV-12 simultaneous production in aeromonads, highlighting both the potential risk for human health, and a role of these foodborne pathogens as reservoirs of resistance determinants in coastal marine environment.

Methicillin-resistant staphylococcal colonization in clinically normal dogs and horses in the community

To evaluate the prevalence of methicillin-resistant staphylococcal (MRS) colonization in clinically normal dogs and horses in the community. Three hundred clinically normal horses and 200 clinically normal dogs were enrolled. One nasal swab was collected from each horse. Two swabs were taken from each dog: (i) from an anterior nare, and (ii) a combination of the perineal area and 0.5 cm into the anus. Enrichment cultures were performed. Methicillin-resistant Staphylococcus aureus (MRSA) was not identified. Methicillin-resistant Staphylococcus intermedius (MRSI) was isolated from the nasal swab from three dogs. Methicillin-resistant coagulase negative staphylococci (MRCoNS) were isolated from 126/300 (42%) horses and 26/200 (13%) dogs. At present MRSI is not considered to be a significant zoonotic concern; however, it may become an important pathogen in dogs. MRCoNS mostly cause disease in compromised human or animal hosts. However, these bacteria can serve as reservoirs of resistance determinants in the community, which could lead to the emergence of novel MRSA strains. This is the first report of the prevalence of MRS colonization in clinically normal dogs in a community setting. Continued surveillance is indicated to determine whether MRSA will emerge in the animal population and become a concern for animal disease and zoonotic infection.

Sampling the Antibiotic Resistome

Microbial resistance to antibiotics currently spans all known classes of natural and synthetic compounds. It has not only hindered our treatment of infections but also dramatically reshaped drug discovery, yet its origins have not been systematically studied. Soil-dwelling bacteria produce and encounter a myriad of antibiotics, evolving corresponding sensing and evading strategies. They are a reservoir of resistance determinants that can be mobilized into the microbial community. Study of this reservoir could provide an early warning system for future clinically relevant antibiotic resistance mechanisms.

Vancomycin-resistant enterococci (VRE) in meat and environmental samples

We investigated the spread of vancomycin-resistant enterococci (VRE) in strains from meat and environmental samples and the location of glycopeptide-resistance determinants in VanA isolates. VRE and VSE (vancomycin-sensitive enterococci) resistance patterns to six antimicrobials were also evaluated. A total of 59 meat isolates (35%) and 119 environmental isolates (26.5%) were glycopeptide resistant enterococci. In particular, 10.7% meat isolates belonged to the VanA, 8.3% to VanB and 16% to VanC phenotypes. Environmental samples presented 0.7% VanA, 14.5% VanB, and 11.4% VanC strains. Evident differences were not observed among the resistance patterns of VRE and VSE isolates. Neither an important difference was observed comparing the resistance patterns in enterococci from meat and environment. In particular a low incidence of β-lactamic resistant strains was found, whereas high rates of resistance were observed for streptomycin (85.7% and 92.8%), kanamycin (79.7% and 96%) and gentamycin (85.1% and 91.7%). An intermediate rate of resistant bacteria emerged for erythromycin (35.1% and 10.5%). All VanA isolates independent of origin had more plasmids with different molecular weights. PCR amplification of the 732 bp fragment in plasmids from the VanA strains confirmed affiliation to the vanA gene cluster and the extrachromosomal location of the glycopeptide-resistance determinants. Our study suggests that food and environment play a potential role as reservoirs of resistance determinants, prompting the need to undertake epidemiological and molecular studies to evaluate the mobility of these genes.

Tetracyclines in veterinary medicine and bacterial resistance to them

Since their discovery in 1945, tetracyclines have been used extensively in the therapy and prophylaxis of infectious diseases and as growth promoters. These wide applications have led to the equally fast spread of tetracycline resistant strains of gram-positive and gram-negative bacterial genera, including strains belonging to pathogenic as well as nonpathogenic species. Nonpathogenic bacteria could act as a reservoir of resistance determinants, which can be disseminated by horizontal transfer into pathogens. More than thirty different tetracycline resistance genes have been characterized. They encode two major mechanisms of resistance: 1 &amp;ndash; active efflux of the antibiotic, and 2 &amp;ndash; protection of ribosomes. Further mechanisms of tetracycline resistance include enzymatic inactivation of antibiotic, permeability barriers, mutations or multidrug transporter systems. Effective horizontal spread is favoured by the location of tetracycline resistance genes on mobile genetic elements such as plasmids and transposons. Their exchange, enhanced by the use of tetracyclines, is observed between bacteria of the same or different species and genera as well. Thus, questions of reevaluating and global reducing of tetracyclines in human and animal healthcare and food production are extensively discussed.