Municipal wastewater monitoring revealed the predominance of bla GES genes with diverse variants among carbapenemase-producing organisms: high occurrence and persistence of Aeromonas caviae harboring the new bla GES variant bla GES-48

An evaluation of the modified carbapenem inactivation method (mCIM) in conjunction with EDTA or sodium mercaptoacetate, for detecting metallo β-lactamase production for Aeromonas species harboring blaCphA

Several Aeromonas species, including Aeromonas hydrophila, have been known to produce CphA, a chromosomal metallo β-lactamase (MBL). We aimed to evaluate the clinical usefulness of modified carbapenem inactivation method (mCIM) in conjunction with EDTA (eCIM) or sodium mercaptoacetate (SMA-mCIM) for MBL-producing Aeromonas species. Fifty-six clinical isolates of Aeromonas species stored at the University of the Ryukyus Hospital were used in this study. The antimicrobial susceptibility testing was performed using a VITEK®2 AST-N404 card (bioMerieux, Marcy-l'Etoile, France) and the results were interpreted according to the CLSI guideline M45 3rd edition. The carbapenemase genes, namely blaGES, blaIMP, blaKPC, blaNDM, blaOXA-48-like, blaVIM, and blaCphA, were detected by PCR. The production of carbapenemase was evaluated using the mCIM and the differentiation of MBL was eCIM and SMA-mCIM. The resistance rates to imipenem and meropenem were 21.4 % (12/56) and 32.1 % (18/56), respectively. The mCIM showed a sensitivity of 100 % (33/33 blaCphA positive isolates) and a specificity of 95.7 % (22/23 blaCphA negative isolates) for the tested isolates. Among the 33 mCIM-positive isolates, 29 (87.9 %) for eCIM, and 6 (18.2 %) for SMA-mCIM were judged as MBL positive, respectively. It is suggested that the mCIM in conjunction with EDTA is useful for detecting MBL production in Aeromonas species harboring blaCphA.

Aeromonas, an opportunistic pathogen present in wastewater in Tulancingo, Mexico

Wastewater is free in the environment and is an important source of contamination. One of the microorganisms that is present in aquatic environments is Aeromonas, so the objective of this study was to identify the presence of Aeromonas in the Tulancingo River. A total of 55 presumptive isolates of Aeromonas spp. were obtained by means of phenotypic characteristics; of these, 80% (44/55) were positive for the gcat gene, and 100% (44/44) of those were confirmed to be Aeromonas spp. by means of the rpoD gene, where Aeromonas caviae was identified in 43.2%, Aeromonas media in 29.5%, Aeromonas hydrophila in 11.3%, Aeromonas salmonicida in 9.1%, and Aeromonas allosaccharophila, Aeromonas lusitana, and Aeromonas veronii in 2.3% each. The genus Aeromonas is capable of causing infections in humans. Aeromonad wastewater can resist treatment processes if not done correctly, which represents a potential route of contamination. Therefore, its presence should not be underestimated, and it should be considered to be a true gastrointestinal pathogen. In addition, specific actions must be taken, mainly with the use of wastewater treatment plants. All of this will ensure the quality of treated water and its reuse for the irrigation of agricultural growing areas, thus mitigating potential health threats.

Temporal dynamics of extended-spectrum β-lactamase-producing Escherichia coli and carbapenemase-producing Gram-negative bacteria in hospital wastewater

Hospital wastewater is a reservoir for the environmental spread of clinically relevant antimicrobial-resistant bacteria and resistance genes. The aim of this study was to quantify total Escherichia coli, extended-spectrum β-lactamase (ESBL)-producing E. coli, and carbapenemase-producing organisms (CPOs) and perform whole-genome sequencing-based characterization of these bacterial isolates in hospital wastewater samples collected bimonthly in Japan from January to November 2021. Total E. coli counts were 8.1 × 103-8.8 × 104 colony-forming units (CFU)/mL. ESBL-producing E. coli were detected in the sampling months of January, March, May, and July, with the ratio of ESBL-producing E. coli to total E. coli being remarkably highest (95 %) in July. In contrast, DHA-1 Ambler class C β-lactamase (AmpC)-producing E. coli was detected in September and November, accounting for 28 % and 3 % of total E. coli counts, respectively. All 140 ESBL-producing E. coli isolates harbored the blaCTX-M genes, with blaCTX-M-14 being the most common genotype (94.3 %), the vast majority of which were associated with the human virulent B2-O25b: H4-ST131-fimH30R/non-Rx. In September, E. coli clade I-O8:H33-ST3910-fimH1074 was primarily associated with blaDHA-1. Among 26 representative CPO isolates, Aeromonas caviae (34.6 %) and A. hydrophila subsp. hydrophila (30.8 %) were dominant. The most frequently detected carbapenemase gene was blaIMP-1 (57.7 %), followed by blaGES-24 (34.6 %) and blaGES-4 (7.7 %). Estimated bacterial counts of CPOs ranged from 4.0 × 10-1 to 4.7 × 103 CFU/mL over the six sampling months. blaIMP-1-positive A. hydrophila subsp. hydrophila ST860, which was repeatedly detected over the five sampling months, accounted for the highest total number of this bacterial clone (79 %). Overall, this study provides insights into the overwhelming presence and persistence of E. coli B2-O25b:H4-ST131-H30R/non-Rx with blaCTX-M-14 and Aeromonas spp. with blaIMP-1 in hospital wastewater, and the change in the dynamics of resistance gene prevalence from blaCTX-M-positive E. coli to blaDHA-1-positive E. coli.

Genetic and biochemical characterization of OXA-1186, a novel OXA-198-type carbapenemase hydrolysing cephalosporins in Citrobacter freundii

OBJECTIVES

This study described OXA-1186, a novel carbapenemase related to OXA-198 carbapenemase and produced by a clinical isolate of Citrobacter freundii.

METHODS

WGS was used to characterize the resistome, virulome and plasmid types of the C. freundii 315C8 isolate and to reconstruct the blaOXA-1186-carrying plasmid. Disc diffusion and broth microdilution assays were used to determine MICs. The blaOXA-1186 gene was cloned into plasmid pTOPO and then transformed into Escherichia coli TOP10 or HB4. It was also cloned in pET41b and transformed into E. coli BL21 DE3 for protein purification. Steady-state kinetic parameters were determined on purified OXA-1186.

RESULTS

C. freundii 315C8, belonging to ST8, was resistant to penicillins including temocillin and broad-spectrum cephalosporins and displayed reduced susceptibility to carbapenems. It was negative for one of the five main carbapenemases. WGS revealed that the blaOXA-1186 gene encoded a novel carbapenemase that shared 83% amino acid identity with OXA-198. The blaOXA-1186 gene was carried on an IncP6-type plasmid and was embedded within a class 1 integron. Cloning and expression in E. coli revealed that expression of the blaOXA-1186 gene conferred resistance to penicillins, cephalosporins and carbapenems, where it was associated with impaired outer membrane permeability. Kinetic parameters confirmed the hydrolysis of ceftazidime, cefepime and aztreonam, in addition to imipenem and meropenem.

CONCLUSIONS

Here, we described a novel carbapenemase, OXA-1186, identified in C. freundii. Unlike OXA-198, OXA-1186 is able to hydrolyse broad-spectrum cephalosporins. This carbapenemase was carried on a broad-spectrum IncP6 plasmid identified in other Citrobacter species and non-fermenters.

Multidrug-resistant ESBL-producing Klebsiella pneumoniae complex in Czech hospitals, wastewaters and surface waters

BACKGROUND

Multidrug-resistant (MDR) bacteria pose a significant challenge to the treatment of infectious diseases. Of particular concern are members of the Klebsiella pneumoniae species complex (KpSC), which are frequently associated with hospital-acquired infections and have the potential to spread outside hospitals via wastewaters. In this study, we aimed to investigate the occurrence and phylogenetic relatedness of MDR KpSC from patients with urinary tract infections (UTIs), hospital sewage, municipal wastewater treatment plants (mWWTPs) and surface waters and to evaluate the clinical relevance of the KpSC subspecies.

METHODS

A total of 372 KpSC isolates resistant to third-generation cephalosporins and/or meropenem were collected from patients (n = 130), hospital sewage (n = 95), inflow (n = 54) and outflow from the mWWTPs (n = 63), river upstream (n = 13) and downstream mWWTPs (n = 17) from three cities in the Czech Republic. The isolates were characterized by antimicrobial susceptibility testing and whole-genome sequencing (Illumina). The presence of antibiotic resistance genes, plasmid replicons and virulence-associated factors was determined. A phylogenetic tree and single nucleotide polymorphism matrix were created to reveal the relatedness between isolates.

RESULTS

The presence of MDR KpSC isolates (95%) was identified in all water sources and locations. Most isolates (99.7%) produced extended-spectrum beta-lactamases encoded by blaCTX-M-15. Resistance to carbapenems (5%) was observed mostly in wastewaters, but carbapenemase genes, such as blaGES-51 (n = 10), blaOXA-48 (n = 4), blaNDM-1 (n = 4) and blaKPC-3 (n = 1), were found in isolates from all tested locations and different sources except rivers. Among the 73 different sequence types (STs), phylogenetically related isolates were observed only among the ST307 lineage. Phylogenetic analysis revealed the transmission of this lineage from patients to the mWWTP and from the mWWTP to the adjacent river and the presence of the ST307 clone in the mWWTP over eight months. We confirmed the frequent abundance of K. pneumoniae (K. pneumoniae sensu stricto and K. pneumoniae subsp. ozaenae) in patients suffering from UTIs. K. variicola isolates formed only a minor proportion of UTIs, and K. quasipneumoniae was not found among UTIs isolates; however, these subspecies were frequently observed in hospital sewage communities during the first sampling period.

CONCLUSION

This study provides evidence of the transmission and persistence of the ST307 lineage from UTIs isolates via mWWTPs to surface waters. Isolates from UTIs consisted mostly of K. pneumoniae. Other isolates of KpSC were observed in hospital wastewaters, which implies the impact of sources other than UTIs. This study highlights the influence of urban wastewaters on the spread of MDR KpSC to receiving environments.

Comparative genomics of IncQ1 plasmids carrying blaGES variants from clinical and environmental sources in Brazil

IncQ-type plasmids have become important vectors in the dissemination of blaGES among different bacterial genera and species from different environments around the world, and studies estimating the occurrence of Guiana extended-spectrum (GES)-type β-lactamases are gaining prominence. We analyzed the genetic aspects of two IncQ1 plasmids harboring different blaGES variants from human and environmental sources. The blaGES variants were identified using polymerase chain reaction (PCR) in Aeromonas veronii isolated from hospital effluent and Klebsiella variicola isolated from a rectal swab of a patient admitted to the cardiovascular intensive care unit in a different hospital. Antimicrobial-susceptibility testing and transformation experiments were performed for phenotypic analysis. Whole-genome sequencing was performed using Illumina and Oxford Nanopore platforms. The comparative analysis of plasmids was performed using BLASTn, and the IncQ1 plasmids showed a high identity and similar size. A. veronii harbored blaGES-7 in a class 1 integron (In2061), recently described by our group, and K. variicola carried blaGES-5 in the known class 1 integron. Both integrons showed a fused gene cassette that encodes resistance to aminoglycosides and fluoroquinolones, with an IS6100 truncating the 3'-conserved segment. The fused genes are transcribed together, although the attC site is disrupted. These gene cassettes can no longer be mobilized. This study revealed a mobilome that may contribute to the dissemination of GES-type β-lactamases in Brazil. Class 1 integrons are hot spots for bacterial evolution, and their insertion into small IncQ-like plasmids displayed successful recombination, allowing the spread of blaGES variants in various environments. Therefore, they can become prevalent across clinically relevant pathogens.