Clonal, Plasmidic and Genetic Diversity of Multi-Drug-Resistant Enterobacterales from Hospitalized Patients in Tripoli, Libya

Resistance to extended-spectrum cephalosporins (ESC) and carbapenems in Enterobacterales is a major issue in public health. Carbapenem resistance in particular is associated with increased morbidity and mortality. Moreover, such resistance is often co-harbored with resistance to non-beta-lactam antibiotics, and pathogens quickly become multi-drug-resistant (MDR). Only a few studies have been published on AMR in Libyan hospitals, but all reported worrisome results. Here, we studied 54 MDR isolates that were collected from 49 patients at the Tripoli University Hospital between 2019 and 2021. They were characterized using phenotypic methods, PCR and PFGE, and a sub-set of isolates were short- and long-read whole-genome sequenced. The results showed the frequent occurrence of Klebsiella pneumoniae (49/54), among which several high-risk clones were responsible for the spread of resistance, namely, ST11, ST17, ST101 and ST147. ESC and carbapenem resistance was due to a wide variety of enzymes (CTX-M, OXA-48, NDM, KPC), with their corresponding genes carried by different plasmids, including IncF-IncHI2 and IncF-IncR hybrids. This study highlights that implementation of infection prevention, control and surveillance measures are needed in Libya to fight against AMR.

Selection of ESBL-producing Escherichia coli in the gut of calves experimentally fed with milk containing antibiotic residues

In the bovine sector, the spread of Enterobacterales producing extended-spectrum and AmpC β-lactamases (ESBL/AmpC) mostly concerns veal calves, and the use of waste milk containing antibiotic residues has been recurrently incriminated. In this study, calves were experimentally fed with milk containing either 2,000 μg/L or 20,000 μg/L of the critically important antibiotic cefquinome. The total counts of enterobacterales and ESBL-producing E. coli were monitored using non-selective and selective media. Our data highlighted the important combination of two main factors (cefquinome exposure and initial ESBL colonization level) in the ESBL selection and amplification process in the gut of calves. Results also proved the dose-independent effect of cefquinome administration on the selection and amplification of ESBL-producing E. coli. Finally, the bla_CTX-M-1/IncI1 ST3 plasmid was systematically recovered after cefquinome exposure, highlighting its epidemic success. Altogether, this work is one of the rare experimental studies providing quantitative information on the impact of waste milk containing antimicrobials on the ESBL load in calves' microbiota, and the first one using cefquinome. These data emphasise the need for global guidelines on the use of waste milk on dairy farms in order to decrease the antimicrobial resistance burden in this sector.

Characterization of cultivable airborne bacteria and their antimicrobial resistance pattern in French milking parlour

The main goal of this preliminary study was to quantify airborne particles and characterize the dominant cultivable bacterial species as well as some Gram-positive species, and their antibiotic resistance pattern, from environmental samples taken inside and outside of a dairy milking parlour. Sampling was performed over 2 days, in different seasons. The small viable particulate matter < 10 μm (bioaerosols) and cultivable bacteria reached their highest concentrations in the milking parlour. The majority of airborne bacteria in the milking parlour belonged to the genera Staphylococcus (41.9%) and Bacillus (20.9%). A total of 32 different bacterial species of Staphylococcus, Aerococcus, Bacillus, Pseudomonas, Serratia and Acinetobacter were identified. Many of these bacteria may be opportunistic pathogens, causing disease in humans or animals. We found low levels of acquired resistance to the antibiotics commonly used in human or animal infections caused by these opportunistic bacteria. More specifically, resistance to tetracyclines (13.4%), penicillin G (13.4%) and macrolides (7.5%) was identified in Staphylococcus sp. as was a methicillin-resistant S. hominis and resistance to spiramycin (n = 1), lincomycin (n = 1) and streptomycin (n = 2) in Aerococcus sp. An assessment of the occupational risk run by dairy farmers for contracting infections after long- or short-term exposure to micro-organisms requires further studies on the concentration of opportunistic pathogenic bacteria in dairy farm environments.

Wide Spread of bla CTX-M-9/mcr-9 IncHI2/ST1 Plasmids and CTX-M-9-Producing Escherichia coli and Enterobacter cloacae in Rescued Wild Animals

Wildlife has recently been pinpointed as one of the drivers of dissemination of genes conferring resistances to clinically important antimicrobials. The presence of both extended-spectrum beta-lactamase- (ESBL) and carbapenemase-encoding genes has notably been reported in wild birds, that can act as sentinels of antimicrobial resistance (AMR) contamination but also as long-distance spreaders in case of migratory birds. Here, 424 wild birds brought to a rescue center in France were sampled over a 6-month period. These birds encompassed 62 different sedentary or migratory species. A further 16 wild mammals present in the center were also investigated. No carbapenemase-producer was found, but we identified a surprisingly high proportion (24.1%) of ESBL-positive isolates. A total of 144 non-duplicate isolates were collected, including Escherichia coli (n = 88), Enterobacter cloacae (n = 51), and Citrobacter freundii (n = 5), of which 123 carried the bla_CTX–M–9 gene. PFGE, phylogroup, and MLST revealed the presence of a limited number of ESBL-positive clones circulating in these animals, all presenting multiple associated resistances. Next-generation sequencing on a subset of isolates, followed by Southern blot hybridization, showed the wide dissemination of an IncHI2/ST1 plasmid carrying the bla_CTX–M–9, bla_SHV–12 and mcr-9 genes. In all, our results undoubtedly reflect cross transmissions of ESC-resistance (ESC-R) Enterobacteriaceae within the rescue center – similarly to nosocomial spreads observed at hospital, rather than the true bacterial flora of birds. We also showed that the spread of ESC-R in this rescue center did not only rely on clonal but also on a highly successful plasmidic transmission. Since most animals are intended to get back to nature after a few days or weeks, this is obviously an issue with regard to ESBL dissemination in natural environments.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Horses, Cats, and Dogs Over a 5-Year Period in France

Methicillin-resistant Staphylococcus aureus (MRSA) has been reported as a worldwide pathogen in humans and animals including companion animals, i.e., cats, dogs, and horses. France lacked a comprehensive nationwide study describing the molecular features of MRSA circulating among companion animals over a large period of time. Here is reported the characterization of 130 non-duplicate clinical MRSA isolates collected from those three animal species from 2010 to 2015 through the French national Resapath network. Characterization of isolates was performed using phenotypic (antimicrobial susceptibility tests) and molecular (DNA arrays, spa-typing) methods. A horse-specific epidemiology was observed in France with the large dissemination of a unique clone, the CC398 clone harboring a Staphylococcal chromosomal cassette mec (SCCmec) type IV and spa-type t011. It was even the unique clone collected in 2015 whereas the clone CC8 USA500 (SCCmec type IV), classically described in horses, was present until 2014. Contrarily, cats and dogs were mainly infected by human-related MRSA isolates, i.e., clones usually reported in human infections, thus mirroring the human epidemiology in hospitals in France. Isolates belonging to the CC398 clone (SCCmec type IV or V) were also identified in 21.4% of dogs' and 26.5% of cats' MRSA isolates. In order to differentiate human-related from CC398 MRSA, tetracycline-resistance [or tet(M) detection] could be useful since this resistance is scarce in human-related strains but constant in CC398 MRSA isolates. In all, our data give a nationwide epidemiological picture of MRSA in companion animals over a 5-year period in France, adding further epidemiological information on the contribution of those animal species to a major public health issue. Considering the wide dissemination of CC398 MRSA isolates and the fact that 11/64 (17.2%) of them presented the Immune Evasion Cluster which enhances CC398 capacities to colonize humans, a specific attention should be paid in the coming years to determine the risk associated to the transmission in people in frequent contacts with companion animals. Our data also show that the prevalence of MRSA has likely decreased in cats, dogs, and horses between 2012 and 2015 in France. This trend should be monitored in the years to come.

Comparative prevalence and characterization of ESBL-producing Enterobacteriaceae in dominant versus subdominant enteric flora in veal calves at slaughterhouse, France

Food-producing animals have become a growing reservoir of Extended-Spectrum Beta-Lactamase (ESBL)-producing bacteria. In cattle, veal calves are exposed to high amounts of antibiotics but ESBL prevalence data are still limited compared to other food sectors such as poultry production. Based on the investigation of 491 veal calves from different slaughtering batches at 12 abattoirs, this study shows a prevalence of 29.4% of ESBL producers in the faecal flora of veal calves in France in 2012. A variety of blaCTX-M genes was found, reflecting possible diverse pathways of dissemination in cattle. Another major conclusion is the comparison of the ESBL prevalence in the dominant versus sub-dominant Escherichia coli population of the same calves (1% and 29.4%, respectively). Also, the ESBL E. coli clones in the sub-dominant flora mostly differed from the non-ESBL dominant E. coli clones of the same calves. Of note, the distribution of blaCTX-M genes and E. coli phylogroups were similar to the ones previously found in ESBL E. coli clones from diseased calves. The hypothesis that ESBL genes may distribute more abundantly in certain backgrounds of E. coli was also discussed. In all, as recently reported in the Netherlands, these results strongly suggest a recent increase in the prevalence of ESBL carriage in French veal calves, which should be considered one of the major ESBL reservoirs in food animals.