Avian colibacillosis caused by avian pathogenic Escherichia coli (APEC) strains is a bacterial disease responsible for enormous economic losses in the poultry industry, due to high mortality rates in farms, antibiotic therapy costs, and seizures at slaughterhouses. The aim of this study was to characterize the serogroups and molecular features of extended spectrum β-lactamase (ESBL)-producing APEC isolates recovered from 248 liver samples of 215 broilers and 33 turkeys with colibacillosis lesions in northeast Algeria. For this, microbiological tests were carried out, according to the recommended standards: E. coli isolates were recovered using standard microbiological protocols, and identification was carried out by MALDI-TOF MS. Serogrouping was performed using a rapid agglutination slide and the antisera of three O somatic groups (O1, O2, O78). Antimicrobial susceptibility was determined by the disk diffusion method. PCR assays and sequencing were used to detect antimicrobial resistance genes, integrons, phylogrouping, and MLST. Conjugation experiments were also conducted to determine the transferability of the retrieved ESBL-encoding genes. Overall, 211 (85.1%) APEC isolates were collected (one per positive sample), and 164 (77.7%) of them were typable. The O2 and O1 serogroups were the most detected (46.1% in broiler typable isolates and 61.5% in turkey typable isolates). Seventeen APEC isolates were ESBL-producers and harbored the following genes (number of isolates): bla_CTX-M-1 (14), bla_CTX-M-15 (2), and bla_SHV-12 (1). They belonged to phylogroups D (10 isolates), B1 (6 isolates), and B2 (1 isolate). The MLST of 13 ESBL producers revealed seven STs: ST23, ST38, ST48, ST117, ST131, ST1146, and ST5087. The ESBL-encoding genes were transferred by conjugation among 15 ESBL-producing isolates, and transconjugants acquired either the IncK or IncI1 plasmids. Concerted efforts from all poultry actors are needed to establish surveillance monitoring strategies to mitigate the spread of ESBL-producing isolates implicated in avian colibacillosis.

Background: European wild rabbits (Oryctolagus cuniculus) are closely connected to the natural environment and might be a potential source of pathogenic bacteria and/or antimicrobial-resistant bacteria. The objective was to identify the bacterial community (species and genera) that colonizes the nasal cavities of European wild rabbits as well as to study the antimicrobial resistance (AMR) phenotypes of bacteria of public health interest. Methods: A total of 147 nasal swabs individually collected from wild rabbits in Spain and Portugal (between 2022 and 2024) were studied. Samples were inoculated in different culture media, and isolates were identified by MALDI-TOF. The AMR phenotypes of staphylococci, mammaliicocci, enterococci and Enterobacterales were evaluated by the disk-diffusion method. Results: Overall, 557 non-repetitive isolates were obtained (1 isolate per species and AMR phenotype of each animal). A wide diversity of genera (n = 40) and species (n = 90) was found. Staphylococcus (21.2%), Mammaliicoccus (11.7%), Enterococcus (23.3%), Enterobacter (9.2%), Citrobacter (4.5%) and Escherichia (5.9%) were the most detected genera. Most animals presented more than one genera (78.9%), and in 15.7% of them, at least five genera were identified. Susceptibility to all antimicrobials tested was found in 37.2%, 38.5% and 51.6% of staphylococci/mammaliicocci, enterococci and Escherichia coli isolates; moreover, multidrug resistance was detected in 10.4%, 14.6% and 9.6% of these groups of bacteria. Moreover, important species of pathogenic bacteria were found, such as Yersinia enterolocolitica (0.5%) and Bordetella bronchiseptica (0.2%), among others. Conclusions: A high bacterial diversity was detected in the nasal cavities of European wild rabbits from the Iberian Peninsula, including pathogenic species and/or resistant strains of public health interest.

Wastewater treatment plants (WWTPs) are recognized hotspots for the convergence and dissemination of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) into the environment. Among ARB, carbapenem-resistant Enterobacterales (CR-E) and extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae (ESBL-Ec/Kp) are of particular concern due to their clinical relevance. We characterized 30 CR-E and 176 ESBL-Ec/Kp isolates (two of them were both ESBL-producing and carbapenem-resistant) recovered from influent, intermediate, effluent, sludge, and downstream river samples collected from two WWTPs in northern Spain. Isolates were evaluated for resistance phenotypes against 12 antimicrobials, and β-lactamase-encoding genes were assessed by PCR and sequencing. Notably, among CR-E isolates, bla_KPC-2 was the most prevalent (93%), followed by bla_OXA-48-like, detected in two isolates from non-treated and pasteurized sludge; both isolates also carried bla_CTX-M-15, a finding not previously reported specifically in sludge samples. Among ESBL-Ec/Kp, a broad diversity of ESBL genes was identified, including bla_{CTX-M group 1} (variants 1, 3, 15, 32, 55), bla_{CTX-M group 9} (variants 14, 27, 65, 97), bla_SHV-12 and bla_TEM-169. The most prevalent ESBL gene was bla_CTX-M-15 (48.3%), followed by bla_CTX-M-14, bla_CTX-M-32, and bla_SHV-12, detected in 10.8%, 8.5%, and 6.8% of isolates, respectively. CR-E and ESBL-Ec/Kp were found in all sample types and were still detectable at terminal stages, indicating persistence throughout treatment. These findings support the need to improve and optimize current wastewater treatment methods and underscore the importance of integrating culture-based and molecular methods into routine WWTP monitoring for early detection of microbiological hazards, although further research is still needed.

Coagulase-negative staphylococci (CoNS) and mammaliicocci (MA) are common in food-derived samples and may act as antimicrobial resistance (AMR) reservoirs. A previous study reported a high S. aureus prevalence in poultry meat. The objective of this study was to characterize the species diversity, antimicrobial resistance, and biofilm-forming capacity of CoNS/MA from the same food samples. Species identification, antimicrobial susceptibility testing, resistance gene detection, molecular typing, and biofilm formation assays were performed. One hundred and forty-eight non-repetitive CoNS/MA isolates were detected in 85% of samples, and 14 species were identified. The most prevalent species were S. epidermidis (18.2%), S. simulans (12.8%), S. saprophyticus (12.2%), S. warneri (11.5%), and M. lentus (10.1%). Most samples harbored one or two different species, although some showed higher diversity. Although 27.0% of isolates were pan-susceptible, 22.3% were multidrug-resistant (MDR), significantly associated with M. lentus and S. epidermidis. Methicillin resistance was found in 10 isolates, mainly in S. epidermidis (lineages ST9, ST59, ST88 and ST640). Biofilm formation was observed in 24.3% of isolates (some of them MDR) and was significantly associated with S. pasteuri and S. xylosus and with samples from supermarkets. No methicillin-resistant isolates were biofilm producers. These findings highlight the diversity of CoNS/MA in poultry meat and their role as AMR reservoirs and persistence factors, emphasizing their relevance in food safety.