Emergence and dissemination of epidemic-causing OXA-244 carbapenemase-producing Escherichia coli ST38 through hospital sewage in Norway, 2020-2022.

BACKGROUND: Population-based sewage surveillance has emerged as a promising approach for studying the prevalence of antibiotic resistance in pathogens. AIM: To determine the temporal prevalence of cefotaxime-resistant Escherichia coli in sewage from five sewage treatment plants located in Bergen city, to determine whether ESBL- and carbapenemase-producing E. coli are consistently disseminated in the receiving environment through sewage. METHOD: A total of 569 cefotaxime-resistant E. coli were isolated over a period of 19 months (August 2020 to February 2022) using ECC CHROMagar™ plates from 82 samples, antibiotic sensitivity profiles were determined, using Sensititre™ plates. The draft genome sequences were determined, using Illumina MiSeq-based sequencing. Complete genome sequences were determined, using Oxford Nanopore-based sequencing. FINDINGS: All 569 strains obtained from influent (N=461) and effluent (N=108) were multi-drug resistant. Most of the sequenced strains (52 of 61) carried blaCTX-M-15 (38.5%) and blaCTX-M-27 (34.6%). The most prevalent sequence types (STs) for ESBL-carrying strains were ST131 (32.8%) and ST38 (21.3%). All CTX-M-27-carrying ST131 strains belonged to clade A or C1, while CTX-M-15-harbouring strains were present in all the clades. Five OXA-244-producing ST38 strains, genetically similar to epidemic-causing strains from Western Norway, France and the Netherlands, were isolated only from raw and treated sewage of the treatment plant receiving hospital sewage. CONCLUSION: This is the first study showing persistent dissemination of OXA-244-producing ST38 clones through sewage in Norway, demonstrating that hospital sewage is the likely source of OXA-244-producing ST38 clones reaching the receiving environment.

Antibiotics and common antibacterial biocides stimulate horizontal transfer of resistance at low concentrations.

There is a rising concern that antibiotics, and possibly other antimicrobial agents, can promote horizontal transfer of antibiotic resistance genes. For most types of antimicrobials their ability to induce conjugation below minimal inhibitory concentrations (MICs) is still unknown. Our aim was therefore to explore the potential of commonly used antibiotics and antibacterial biocides to induce horizontal transfer of antibiotic resistance. Effects of a wide range of sub-MIC concentrations of the antibiotics cefotaxime, ciprofloxacin, gentamicin, erythromycin, sulfamethoxazole, trimethoprim and the antibacterial biocides chlorhexidine digluconate, hexadecyltrimethylammoniumchloride and triclosan were investigated using a previously optimized culture-based assay with a complex bacterial community as a donor of mobile resistance elements and a traceable Escherichia coli strain as a recipient. Chlorhexidine (24.4µg/L), triclosan (0.1mg/L), gentamicin (0.1mg/L) and sulfamethoxazole (1mg/L) significantly increased the frequencies of transfer of antibiotic resistance whereas similar effects were not observed for any other tested antimicrobial compounds. This corresponds to 200 times below the MIC of the recipient for chlorhexidine, 1/20 of the MIC for triclosan, 1/16 of the MIC for sulfamethoxazole and right below the MIC for gentamicin. To our best knowledge, this is the first study showing that triclosan and chlorhexidine could stimulate the horizontal transfer of antibiotic resistance. Together with recent research showing that tetracycline is a potent inducer of conjugation, our results indicate that several antimicrobials including both common antibiotics and antibacterial biocides at low concentrations could contribute to antibiotic resistance development by facilitating the spread of antibiotic resistance between bacteria.

High prevalence of class 1 integrons in clinical isolates of methicillin-resistant Staphylococcus aureus from India.

INTRODUCTION: Class1 integrons are one of the prevalent mechanisms of antibiotic resistance gene transfer in Gram-negative organisms, but their prevalence and role in the spread of antibiotic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA) is unexplored. The purpose of this study was to investigate the prevalence of class 1 integrons in clinical isolates of MRSA. MATERIALS AND METHODS: Total 143 MRSA isolates obtained from two different cities in India (Pune and Mumbai) were characterized by biochemical tests, and the antibiotic sensitivity was performed using the Clinical and Laboratory Standards Institute (CLSI) guidelines. The presence of class 1 integrons, sul1/qacE0Δ1 region of class 1 integron and mecA gene among these isolates was determined by polymerase chain reaction (PCR). RESULTS: All 143 isolates were mecA positive and coagulase-positive. Overall, 71% of the MRSA isolates carried class 1 integrons; 58% (45/77) of the isolates obtained from Mumbai and 85% (56/66) of the isolates from Pune carried class 1 integrons. In all, 39% of these isolates carried sul1/qacEΔ1 region, thus confirming the association of class 1 integrons with antibiotic resistance genes. Along with ß-lactam antibiotics the MRSA isolates were resistant to several other antibiotics, with resistance to erythromycin, ciprofloxacin and trimethoprim-sulfamethoxazole being observed in 75%, 66% and 60% of the isolates, respectively. CONCLUSION: To the best of our knowledge, this is the first report of class 1 integrons in MRSA isolates from India. The study provides insights into the prevalence of a novel mechanism adapted by MRSA for the propagation of antibiotic resistance genes.

Megasphaera indica sp. nov., an obligate anaerobic bacteria isolated from human faeces.

Two coccoid, non-motile, obligately anaerobic, Gram-stain-negative bacteria, occurring singly or in pairs, or as short chains, with a mean size of 1.4-2.5 µm were isolated from the faeces of two healthy human volunteers, aged 26 and 56 years, and were designated NMBHI-10(T) and BLPYG-7, respectively. Both the strains were affiliated to the sub-branch Sporomusa of the class Clostridia as revealed by 16S rRNA gene sequence analysis. The isolates NMBHI-10(T) and BLPYG-7 showed 99.1 and 99.2% 16S rRNA gene sequence similarity, respectively, with Megasphaera elsdenii JCM 1772(T). DNA-DNA hybridization and phenotypic analysis showed that both the strains were distinct from their closest relative, M. elsdenii JCM 1772(T) (42 and 53% DNA-DNA relatedness with NMBHI-10(T) and BLPYG-7, respectively), but belong to the same species (DNA-DNA relatedness of 80.9 % between the isolates). According to DNA-DNA hybridization results, the coccoid strains belong to the same genospecies, and neither is related to any of the recognized species of the genus Megasphaera. Strains NMBHI-10(T) and BLPYG-7 grew in PYG broth at temperatures of between 15 and 40 °C (optimum 37 °C), but not at 45 °C. The strains utilized a range of carbohydrates as sources of carbon and energy including glucose, lactose, cellobiose, rhamnose, galactose and sucrose. Glucose fermentation resulted in the formation of volatile fatty acids, mainly caproic acid and organic acids such as succinic acid. Phylogenetic analysis, specific phenotypic characteristics and/or DNA G+C content also differentiated the strains from each other and from their closest relatives. The DNA G+C contents of strains NMBHI-10(T) and BLPYG-7 are 57.7 and 54.9 mol%, respectively. The major fatty acids were 12 : 0 FAME and 17 : 0 CYC FAME. On the basis of these data, we conclude that strains NMBHI-10(T) and BLPYG-7 should be classified as representing a novel species of the genus Megasphaera, for which the name Megsphaera indica sp. nov. is proposed. The type strain is NMBHI-10(T) ( = DSM 25563(T) = MCC 2481(T)).