Extended-spectrum β-lactamases (ESBLs) constitute one of the principal mechanisms underlying multidrug resistance (MDR) in avian pathogenic Escherichia coli (APEC). The coexistence of ESBL-encoding genes, particularly blaCTX-M, together with the plasmid-mediated colistin resistance gene mcr-1 in APEC raises serious concern, as it undermines the effectiveness of third-generation cephalosporins and colistin. To clarify the current epidemiological status and potential transmission risks associated with the co-occurrence of ESBL and mcr-1 genes in southern Xinjiang, 133 liver samples from chickens that had died after exhibiting clinical signs consistent with colibacillosis were collected, from which 100 of these isolates (75.2%, 100/133) were confirmed as APEC. The double-disk diffusion test revealed that 65 strains (65.0%, 65/100) were ESBL-producing. Among these ESBL-producing APEC isolates, resistance rates to ampicillin, cefazolin, ceftiofur, and cefoxitin were 100% (65/65), 100% (65/65), 92.3% (60/65), and 4.6% (3/65, intermediate/susceptible), respectively. PCR detection revealed that 95.4% (62/65) carried blaCTX-M and 93.8% (61/65) carried blaTEM and five isolates (7.7%, 5/65) were resistant to colistin and carried the mcr-1 gene. Integron analysis revealed that int1 was detected in 98.5% (64/65) of the ESBL-APEC isolates. Notably, all five mcr-1-positive strains co-harbored int1. These five isolates exhibited MDR phenotypes and were assigned to phylogenetic groups A (n = 1), B1 (n = 3), and D (n = 1). Whole-genome sequencing (WGS) revealed that the five mcr-1-positive APEC strains belonged to four sequence types (STs): ST6792 (n = 1), ST1196 (n = 2), ST155 (n = 1), and ST162 (n = 1), and harbored three blaCTX-M subtypes (blaCTX-M-55 [n = 3], blaCTX-M-64 [n = 1], and blaCTX-M-65[n = 1]). Furthermore, these strains carried IncI2 or IncFIB plasmid replicons alongside the int1 integrase gene, highlighting the co-occurrence of critical resistance determinants with mobile genetic elements known to facilitate horizontal dissemination. The coexistence of blaCTX-M and mcr-1 in high-risk clones such as ST155 and ST162, which are associated with human infections worldwide, indicates that the region faces a threat from multidrug-resistant strains and a potential risk of cross-species transmission. Given the limited geographic scope and sample size, our findings should be considered a preliminary warning. Future studies with expanded sampling and experimental validation of horizontal transfer are needed to fully assess the transmission risks.

Osteomyelitis remains a persistent healthcare concern due to bacterial invasion and difficulty in inhibiting and eradicating biofilm-forming bacteria from infected bone tissue. Conventional therapies, including systemic antibiotics and surgically implanted beads made of calcium sulfate or polymethyl methacrylate, are hindered by complications like cytotoxicity, uneven drug distribution, and thermal denaturation of antibiotics during polymerization. Here, a solvent-free droplet approach is introduced for producing ready-to-use antibiotic-loaded beads through controlled aggregation of pre-formed polymer latex nanoparticles composed of poly (methyl methacrylate-co-butyl acrylate) [P(MMA-BA)]. Calcium chloride, a benign coagulant, triggers the controlled aggregation of latex nanoparticles and enables bead formation without the need for hand-mixing, chemical initiators, and solvents used in the existing PMMA bead fabrication method. Ampicillin was incorporated as a model antibiotic to evaluate antimicrobial and biocompatibility performance. The resulting beads demonstrated prolonged antibacterial activity and strong inhibition of Staphylococcus aureus biofilms. In co-culture systems with osteoblast Saos-2 cells, the beads selectively inhibited bacterial growth while maintaining cell viability, confirming their dual antibacterial and cytocompatibility functions. In vivo evaluations further supported their effectiveness in infection control and tissue integration. Overall, these results highlight the potential of latex particle-assembled polymeric beads as a scalable, solvent-free, and efficient platform for targeted bone infection treatment.

A 1-year-old female-intact arctic fox (Vulpes lagopus) presented for diarrhea, lethargy, severe thrombocytopenia, and hyperbilirubinemia. Blood film evaluation revealed intracytoplasmic coccoid bacteria within moderate numbers of leukocytes consistent with infection by a rickettsial organism. Similar organisms were observed within many leukocytes from fine-needle aspirates of an enlarged peripheral lymph node. The lymph node also contained moderate necrosis and an expansion of granular lymphocytes. Parasitic ovum consistent with the trematode Nanophyetus salmincola was found on fecal floatation. The patient responded to treatment with doxycycline, enrofloxacin, ampicillin/sulbactam, and other supportive therapies. Polymerase chain reaction testing confirmed the presence of Neorickettsia sp., and DNA sequencing identified the organism as Stellantchasmus falcatus agent. To the authors' knowledge, this is the first report describing this organism microscopically in peripheral blood, the first reported case of infection in this species of canid, and describes the various clinicopathologic changes with this infection.

This study investigated the indigenous bacterial diversity of 'El Kaddid', a traditional Algerian dried-salted meat, using a culture-independent approach. In parallel, culture-dependent methods were applied specifically to isolate and identify the lactic acid bacteria (LAB) population. Microbial fingerprinting of ten 'El Kaddid' samples using 16S rRNA gene (V3-V4 region) sequencing and subsequent sequence analysis revealed complex bacterial communities dominated by species of Staphylococcus. LAB were isolated on selective agar plates from 32 'El Kaddid' samples, followed by basic phenotypic characterization and identification through 16S rRNA gene sequencing. Among the 179 LAB isolates recovered, a majority belonged to the genus Enterococcus, predominantly to Enterococcus faecium and Enterococcus hirae. Further differentiation of closely related species of Enterococcus, including members of the Enterococcus faecium clades A and B, was achieved using sequential PCR assays targeting gluP and sodA genes and the internal transcribed spacer (ITS) amplification patterns. Many isolates exhibited antimicrobial activity against the indicator strain Latilactobacillus sakei CECT 906T, with 11 isolates showing a strong inhibitory activity. Antibiotic susceptibility testing of 77 representative isolates revealed that all LAB isolates were susceptible to vancomycin, and chloramphenicol. However, they all showed resistance to ampicillin and penicillin, and most also to rifampicin. This study contributes to the microbial characterization of 'El Kaddid', and provides baseline information on its LAB community and safety-related traits.

Bacterial persisters show tolerance to bactericidal antibiotics and play essential roles in chronic infections; however, the general mechanisms underlying persister formation and antibiotic tolerance remain insufficiently characterized. In this study, the Escherichia coli Keio library was used to identify genes involved in ciprofloxacin tolerance by culturing each mutant to the late stationary phase (to induce persistence via starvation), followed by dilution into fresh medium for antibiotic exposure. This two-step, genome-wide screening approach enabled the identification of 37 ciprofloxacin-sensitive mutants with diverse biological functions and 11 ciprofloxacin-tolerant mutants related to amino acid and β-nicotinamide adenine dinucleotide (NAD[+]) biosynthesis, with 25 genes being identified as persister-related genes for the first time. Notably, sensitive mutants (ΔatpC, ΔatpF, ΔruvC, and Δrnr) were specifically sensitive to quinolone antibiotics, whereas tolerant mutants (ΔmetR, ΔleuB, and ΔnadB) showed tolerance to ampicillin and gentamicin. Importantly, adenosine triphosphate (ATP) levels were downregulated in ciprofloxacin-tolerant mutants and upregulated in ciprofloxacin-sensitive mutants, implying a negative correlation between ATP levels and ciprofloxacin tolerance among these genetically distinct persisters. This negative correlation was further observed when ATP levels in different mutants were chemically modulated using specific metabolites, nutrients, and respiration inhibitors. In addition, ciprofloxacin persistence across different mutants was found to correlate closely with antibiotic uptake and reactive oxygen species (ROS) levels. Collectively, these findings establish a universal role for ATP in the ciprofloxacin tolerance of genetically diverse persisters under varying resuscitation conditions, conceivably through the modulation of antibiotic uptake and ROS accumulation, and it is implied that the provision of abundant nutrients is potentially beneficial for anti-persister chemotherapy in clinic settings.

The cell wall of the Gram-positive bacterium Enterococcus faecalis is decorated with the enterococcal polysaccharide antigen (EPA), consisting of a core rhamnan backbone linked covalently with a strain-variable teichoic acid-like (TA) polymer. Current models propose that the TA decoration is a repeating polymer composed of two alternating subunits, designated TAI and TAII, which are attached to the rhamnan core via a mild-acid labile phosphodiester bond from the initiating TAI subunit. In this study, we characterize the EpaU autolysin encoded within the EPA biosynthetic gene cluster. We demonstrate that the cell wall-binding domain of EpaU associates with the intact TA domains of EPA synthesized with the aid of the glycosyltransferases EpaR and EpaX. We further show that EpaU is a potent autolysin that binds generally over the E. faecalis cell surface, suggesting that it functions as a remodeling peptidoglycan hydrolase. The absence of EpaU leads to increased ampicillin resistance and elevated intracellular levels of the second messenger c-di-AMP. These data suggest that E. faecalis possesses a mechanism that senses the integrity of the peptidoglycan meshwork and employs c-di-AMP to regulate cell turgor, potentially altering the antibiotic resistance.

Wildlife can serve as a potential reservoir and spreader of resistant and pathogenic bacteria. Raptors, occupying the ecological position of apex or mesopredators, integrate exposure across different habitats and therefore serve as bioindicators of environmental dissemination of pathogens. In this study, we isolated 54 Escherichia coli (E. coli) strains from feces sampled from 64 raptors admitted to a wildlife rescue center in Central Italy. Phenotypic antimicrobial susceptibility testing was conducted, followed by molecular screening for resistance genes. Additionally, the presence of intestinal E. coli pathotypes, including STEC, EHEC, EPEC, ETEC, EAEC, EIEC, and NTEC, was evaluated through virulence gene analysis. Results indicated notable resistance to commonly used antimicrobials, with the highest percentages observed for ampicillin (40.74%), fluoroquinolones (31.48%), and tetracycline (25.93%). Molecular analysis of phenotypically resistant isolates identified the presence of several resistance genes, including blaTEM (13 isolates), blaCTX-M (4 isolates), blaCMY-2 (3 isolates), blaSHV (1 isolate), tet(A) (9 isolates), tet(B) (4 isolates), cat1 (1 isolate), and cmlA (2 isolates). Furthermore, 29.63% of isolates were classified as multidrug-resistant (MDR) and 7.41% as extensively drug-resistant (XDR). Regarding virulence profiles, one isolate harboring eaeA, escV, and astA genes was classified as atypical EPEC, while 27.78% isolates had only the astA gene, preventing precise pathotype assignment. These findings highlight the circulation of antimicrobial-resistant and potentially pathogenic E. coli strains within raptor populations in Central Italy, emphasizing the zoonotic potential and reaffirming the role of raptors as bioindicators within a One Health approach.

Clostridium tertium is an emerging opportunistic pathogen typically associated with immunocompromised hosts, yet it can also cause serious infections in non-neutropenic individuals. We present a case of postoperative peritonitis and bacteremia caused by C. tertium in a non-neutropenic 75-year-old woman following emergency obturator hernia repair. Diagnosis was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and successful treatment was achieved with piperacillin-tazobactam combined with levornidazole alongside surgical source control. A review of 128 cumulative cases (including ours) revealed two distinct patterns: bacteremia in severely neutropenic patients versus a broader spectrum of localized and bloodstream infections in non-neutropenic hosts, often linked to intestinal barrier disruption. Mortality was largely driven by underlying comorbidities and polymicrobial sepsis. These findings indicate that C. tertium infection should be considered in non-neutropenic patients with postoperative or gastrointestinal barrier-disruptive infections, especially when there is a poor response to initial empiric therapy. Consequently, in such clinical scenarios, empirical therapy should be guided by its unique resistance pattern, favoring carbapenems, vancomycin, or piperacillin-tazobactam, often combined with a nitroimidazole, alongside urgent source control.

Non-typhoidal Salmonella (NTS) is an important poultry-associated pathogen with major One Health and economic impacts, but data on its epidemiology and antimicrobial resistance in Nigeria remain limited. This study investigated the prevalence, serovar distribution, clonal relatedness, and antimicrobial resistance of NTS along the poultry production chain in Enugu State, southeastern Nigeria. A total of 2400 samples were collected, comprising feces (cecal content)/cloacal swabs from chickens (n = 1100), eggs (n = 400), chicken meat (n = 600), and stool samples from poultry workers (n = 300). Isolation and identification were performed using standard bacteriological methods, with confirmation by serotyping and polymerase chain reaction (PCR) targeting the invA gene. Genetic relatedness was assessed using enterobacterial repetitive intergenic consensus (ERIC)-PCR, and antimicrobial susceptibility was determined by the disk diffusion method. Overall, 47 (2.0%) Salmonella enterica isolates were recovered from 2400 samples, with the highest prevalence observed in eggs (3.5%), followed by human stool (3.3%), chicken meat (1.8%), and chicken feces (1.1%). Only 35 (11.8%) of the 297 sampled farms were positive for Salmonella, and recovery rates differed significantly (p = 0.0065) among sample sources. Five serotypes were identified, dominated by S. Typhimurium (57.4%), followed by S. Enteritidis (14.9%), S. Anatum (12.8%), S. Stanley (8.5%), and S. Agona (6.3%). ERIC-PCR revealed multiple clonal clusters, many containing isolates from mixed sources, indicating circulation of related strains between poultry and humans. All isolates were resistant to ampicillin, with high resistance to tetracycline (76.6%), sulphamethoxazole-trimethoprim (51.1%), and fluoroquinolones. Overall, 80.9% of isolates were multidrug-resistant, with a mean Multiple Antibiotic Resistance Index of 0.29, highest among isolates from chicken feces. Although the prevalence of NTS was low, the presence of genetically related multidrug-resistant strains across the production chain underscores the role of poultry as a reservoir for zoonotic transmission and highlights the need for coordinated One Health surveillance and antimicrobial stewardship strategies in Nigeria.

Salmonella is a major cause of foodborne illness worldwide, posing significant risks to public health and food safety. This study investigated the prevalence, serovar distribution, genotypic characteristics, and antimicrobial resistance (AMR) profiles of Salmonella. A total of 2515 food samples were collected from retail markets, supermarkets, and food processing facilities, and 13,670 stool samples were obtained from sentinel hospitals across 14 cities in Liaoning. The Kruskal-Wallis test was used to compare genetic features among serovars, followed by Dunn's post hoc test for pairwise comparisons. A total of 314 Salmonella strains were identified, with raw poultry showing the highest detection rate (28.88%) among food sources and children aged 0-6 years (3.47%) the highest among the clinical age groups. Among food samples, S. Enteritidis was the most prevalent serovar (42.6%), and it was also the most common in clinical samples (35.8%); in contrast, S. 4,[5],12:i:- was dominant in pediatric clinical cases. According to AMR analysis, 90.13% of strains were resistant to at least one antibiotic and 67.83% were multidrug-resistant (MDR), with the highest resistance to ampicillin (68.47%). Analysis revealed that S. 4,[5],12:i:- harbored the ASSuT resistance module (blaTEM-1B, aph(3″)-Ib/aph(6)-Id, sul2, tet(B)). Extensive MDR phenotypes were observed in S. Indiana and S. Kentucky, associated with abundant insertion sequences (IS) and resistance genes (ARGs), including clinically critical determinants (blaNDM-9, mcr-1.1, rmtB). The highest mean virulence factor (VF) count (111.17) was observed in S. Enteritidis, contributing to its epidemiological success. Conversely, S. Indiana and S. Kentucky, predominantly food-associated serovars, exhibited reduced virulence but served as critical AMR reservoirs. These findings highlight the epidemiological characteristics and AMR risks of Salmonella in food and clinical settings, providing critical data for food safety and clinical antimicrobial stewardship.

Non-O1/non-O139 Vibrio cholerae strains are widely distributed in aquatic environments worldwide and are increasingly recognized as potential reservoirs of antimicrobial resistance and virulence-associated determinants. In this study, we performed an integrated phenotypic and genomic analysis of 116 V. cholerae isolates collected in 2024 from environmental and clinical sources in Jiaxing, China, including 106 non-O1/non-O139 isolates, 9 O1 isolates, and 1 O139 isolate. Antimicrobial susceptibility testing showed that most isolates remained susceptible to β-lactam/β-lactamase inhibitor combinations, third-generation cephalosporins, carbapenems, and tigecycline, whereas resistance was more frequently observed for ampicillin, streptomycin, nalidixic acid, and ciprofloxacin. Based on the non-susceptibility criteria of Maitrakas et al., 19 of 116 isolates (16.4%) were classified as multidrug-resistant, whereas none met the definition of extensively drug-resistant. Genomic analysis identified diverse resistance determinants, including plasmid-mediated quinolone resistance genes (qnrVC variants) and quinolone resistance-determining region mutations in gyrA and parC. Virulence-associated genes showed heterogeneous distributions: core regulatory and hemolysis-related genes were highly prevalent, whereas classical cholera toxin genes were largely absent. Several accessory virulence factors, including the RTX toxin operon, chxA, ninth, and makA, were detected in subsets of isolates. Core genome multilocus sequence typing revealed substantial genetic diversity, with environmental and clinical isolates distributed across multiple lineages and showing no clear clustering by isolation source. Overall, these data demonstrate the diverse antimicrobial resistance, virulence-associated gene repertoires, and population structure of the Jiaxing V. cholerae collection, with particular relevance to the predominant non-O1/non-O139 population.