A Novel Single-Tube Eicosaplex/Octaplex PCR System for the Detection of Extended-Spectrum β-Lactamases, Plasmid-Mediated AmpC β-Lactamases, and Integrons in Gram-Negative Bacteria

Emergence of colistin-resistant Enterobacter cloacae and Raoultella ornithinolytica carrying the phosphoethanolamine transferase gene, mcr-9, derived from vegetables in Japan

IMPORTANCE

Plasmid-mediated mobile colistin-resistance genes have been recognized as a global threat because they jeopardize the efficacy of colistin in therapeutic practice. Here, we described the genetic features of two mcr-9.1-carrying Gram-negative bacteria with a colistin-resistant phenotype derived from vegetables in Japan. The colistin-resistant mcr-9.1, which has never been detected in vegetables, was located on a large plasmid in Enterobacter cloacae CST17-2 and Raoultella ornithinolytica CST129-1, suggesting a high chance of horizontal gene transfer. To the best of our knowledge, this is the first report of mcr-9 in R. ornithinolytica. This study indicates that fresh vegetables might be a potential source for the transmission of mcr-9 genes encoding resistance to frontline (colistin) and clinically relevant antimicrobials. The study also provides additional consideration for colistin use and the relevance of routine surveillance in epidemiological perspective to curb the continuous spread of mcr alleles.

Predominance of Multidrug-Resistant Gram-Negative Bacteria Isolated from Supermarket Retail Seafood in Japan

Reports have documented antimicrobial usage in aquaculture, and the aquatic ecosystem can be considered a genetic storage site for antibiotic-resistant bacteria. This study assessed the prevalence of antimicrobial resistance (AMR) among Gram-negative bacteria recovered from retail seafood in Hiroshima, Japan. A total of 412 bacteria were isolated and screened for the presence of β-lactamases, acquired carbapenemases, and mobile colistin-resistance (mcr) genes. Forty-five (10.9%) isolates were dominated by Morganella (28%), Proteus (22%), Aeromonas (14%), Citrobacter (8%), and Escherichia (8%) and carried AMR genes. The identified AMR genes included those encoded in integrons (19), aac(6՛)-Ib (11), blaTEM-1 (7), blaCTX-M-like (12), blaCTX-M-65 (2), blaSHV-12 (1), blaSHV-27 (1), blaOXA-10 (1), blaOXA-2 (1), and mcr (2). The most common clinical resistances were against ampicillin, colistin, sulfamethoxazole/trimethoprim, tetracycline, and ciprofloxacin. Multidrug resistance (MDR) occurred in 27 (60%) AMR isolates, and multiple antibiotic resistance indices ranged from 0.2 to 0.8. A conjugation experiment showed that 10 of the 11 selected MDR strains harbored conjugable plasmids, although PCR-based replicon typing described seven strains as untypable. IncF replicon was identified in MDR extended-spectrum β-lactamase-producing Escherichia coli of the pathogenic B2 phylogroup. Our findings suggest that retail seafood harbors MDR bacteria of human interest that require strict resistance surveillance in the seafood production continuum.

Regulation Transcriptional of Antibiotic Resistance Genes (ARGs) in Bacteria Isolated from WWTP

The incidence of antibiotics and transcriptional regulation of ARGs in isolated bacteria from wastewater needs to be explored. By HPLC, in samples of untreated wastewater, ampicillin (49.74 ± 5.70 µg/mL), chloramphenicol (0.60 ± 0.03 µg/mL), tylosin (72.95 ± 2.03 µg/mL), and oxytetracycline (0.22 ± 0.01 µg/mL) was determined. Through metagenomic analysis identified 58 bacterial species belonging to 9 phyla and at least 14 species have shown resistance to a variety of antibiotics. Twenty-two bacterial isolates were proved to be resistant to fifteen antibiotics of new generation and used in medical research to combat infectious diseases. Fourteen strains were shown to harbor plasmids in size ranges of 2-5 Kb, 6-10 Kb and plasmids with size greater than 10 Kb. By quantitative PCR it was possible to identify genes sul, qnr, cat1, aadA1, and sat-1 gene were shown to be present in gDNA samples from treated and untreated samples of wastewater and by relative expression analysis, differential expression of cat1, ermB, act, and tetA genes was demonstrated in strains that showed identity with Escherichia coli, Bacteroides fragilis, and Salmonella thyphi, and that were stressed with different concentrations of antibiotics. The presence of ARGs in untreated water samples, as well as in bacterial isolates, was indicative that in these habitats there are microorganisms that can resist β-lactams, aminoglycosides, tetracyclines, sulfonamides, and quinolones.

Prevalence of antibiotic-resistant Gram-negative bacteria having extended-spectrum β-lactamase phenotypes in polluted irrigation-purpose wastewaters from Indian agro-ecosystems

Antibiotic resistance in bacteria has emerged as a serious public health threat worldwide. Aquatic environments including irrigation-purpose wastewaters facilitate the emergence and transmission of antibiotic-resistant bacteria and antibiotic resistance genes leading to detrimental effects on human health and environment sustainability. Considering the paramount threat of ever-increasing antibiotic resistance to human health, there is an urgent need for continuous environmental monitoring of antibiotic-resistant bacteria and antibiotic resistance genes in wastewater being used for irrigation in Indian agro-ecosystems. In this study, the prevalence of antibiotic resistance in Gram-negative bacteria isolated from irrigation-purpose wastewater samples from Sirmaur and Solan districts of Himachal Pradesh was determined. Bacterial isolates of genera Escherichia, Enterobacter, Hafnia, Shigella, Citrobacter, and Klebsiella obtained from 11 different geographical locations were found to exhibit resistance against ampicillin, amoxyclav, cefotaxime, co-trimoxazole, tobramycin, cefpodoxime and ceftazidime. However, all the isolates were sensitive to aminoglycoside antibiotic gentamicin. Enterobacter spp. and Escherichia coli showed predominance among all the isolates. Multidrug-resistance phenotype was observed with isolate AUK-06 (Enterobacter sp.) which exhibited resistant to five antibiotics. Isolate AUK-02 and AUK-09, both E. coli strains showed resistant phenotypes to four antibiotics each. Phenotypic detection revealed that six isolates were positive for extended-spectrum β-lactamases which includes two isolates from Enterobacter spp. and E. coli each and one each from Shigella sp. and Citrobacter sp. Overall, the findings revealed the occurrence of antibiotic resistant and ESBL-positive bacterial isolates in wastewaters utilized for irrigation purpose in the study area and necessitate continuous monitoring and precautionary interventions. The outcomes of the study would be of significant clinical, epidemiological, and agro-environmental importance in designing effective wastewater management and environmental pollution control strategies.

Comparative molecular profiling of antimicrobial resistance and phylogenetic characterization of multidrug-resistant Escherichia coli isolated from meat sources in 2009 and 2021 in Japan

The global spread of antimicrobial resistance (AMR) is alarming. Escherichia coli is a Gram-negative bacterium that causes healthcare-associated infections and is a major threat to public health. Currently, no comprehensive antimicrobial surveillance of multidrug-resistant E. coli of diverse phylogroups along the meat value chain has been implemented in Higashihiroshima, Japan. Therefore, by employing the One Health approach, 1183 bacterial isolates, including 303 recovered from meat samples in 2009, were screened for the presence of antimicrobial resistance determinants using multiplex PCR and DNA sequencing techniques. Seventy-seven non-duplicate E. coli isolates that harbored AMR genes were subjected to antimicrobial susceptibility testing and the detection of integrons. Phylogenetic characterization, which has not been previously investigated, was used to assign E. coli to one of the eight phylogroups. Twenty-six out of 33 (78.8%) and 34 out of 44 (77.3%) E. coli isolates from 2009 and 2021 exhibited multidrug resistance (MDR) phenotypes, respectively. The most common clinical resistance was observed against ampicillin, tetracycline, kanamycin, sulfamethoxazole/trimethoprim, cefotaxime, and chloramphenicol. Overall, 22.1% (17/77) of the E. coli isolates carried extended-spectrum β-lactamase (ESBL)-encoding genes and showed the ESBL-resistant phenotypes. For the two isolation years, AmpC/ESBL prevalence decreased from 42.4% in 2009 to 20.5% in 2021. The identified AMR genes included bla_CTX-M-1, bla_CTX-M-2, bla_CTX-M-14, bla_CTX-M-15, and bla_SHV-12 (ESBL-types); bla_SHV-1, bla_TEM-1, bla_TEM-135, and bla_TEM-176 (narrow-spectrum types); bla_CMY-4, bla_ADC-32, bla_ADC-216, bla_ACT-48, and bla_ACT-51 (AmpC types); and integrons. All E. coli isolates were negative for carbapenemase-encoding genes, whereas one isolate from 2009 carried mcr-5.1 allele. Approximately 52% of E. coli isolates identified in 2009 were assigned to phylogroup A compared to the 20.5% in 2021. Notably, the highest proportions of E. coli phylogroups exhibiting MDR were groups A, B1, and F, suggesting that members of these groups are mostly associated with drug resistance. This study highlights the role of meat as a significant reservoir of MDR E. coli and potential source for transmission of AMR genes. Our findings emphasize the importance of continuous monitoring to track the changes in the spread of antimicrobial resistance in the food chain.