In response to the growing threat posed by increasing microbial resistance to antimicrobial agents, the World Health Organization has developed the “One Health” concept, which recognizes the interconnectedness of human, animal, and environmental health. The BALTIC-AMR project aims to develop a rational, transnational strategy for countries surrounding the Baltic Sea, enabling a comprehensive analysis of and response to the growing phenomenon of resistance to antibacterial compounds.

The present study focuses on the isolation of bacterial strains that are resistant to β-lactam antibiotics and carbapenems from sewage samples (raw and treated) as well as from seawater collected in coastal areas of the Baltic Sea in Poland. Sampling was conducted every two weeks during 2024 and 2025. Strains were isolated using the membrane filtration method and cultured on CHROMagar™ ESBL and mSuperCARBA™ media. Biochemical identification of the isolates was performed using the VITEK 2 automated system (bioMérieux).

In total, 98 strains were analyzed, including 53 that were resistant to cefotaxime and 45 that were resistant to meropenem. The majority of isolates belonged to the genus Pseudomonas (23%), Escherichia coli (20%), and the Enterobacter cloacae complex (18%). The remaining isolates were identified as Klebsiella pneumoniae subsp. pneumoniae, Citrobacter freundii, Citrobacter braakii, Stenotrophomonas maltophilia, and several other species, including Serratia fonticola, Hafnia alvei, and Aeromonas sobria. In the next stage of the study, whole-genome sequencing of the bacterial isolates will be performed to further characterize their antimicrobial resistance profiles. Overall, these findings highlight the environmental dissemination of antimicrobial-resistant bacteria and underscore the importance of integrated surveillance within the One Health framework.

Project No. 2023/05/Y/NZ9/00169 funded by the National Science Centre in cooperation with the JPIAMR network - Joint Programming Initiative on Antimicrobial Resistance.

Introduction:

Salmonella enterica serovar Typhimurium remains one of the most important zoonotic pathogens associated with pig production. Its ability to persist and disseminate multidrug resistance (MDR) poses a significant challenge within the One Health framework. This study aimed to characterize phenotypic and genotypic antimicrobial resistance among S. Typhimurium isolates obtained from pigs and their environment in Poland between 2014 and 2019.

Materials and Methods:

From a collection of approximately 580 Salmonella isolates of different serovars collected from pigs and related environments in Poland between 2014 and 2019, 36 Salmonella Typhimurium (including monophasic and atypical variants) isolates were selected for whole-genome sequencing and further analysis. Isolates originated from feces/manure, boot swabs, environmental dust, rectal swabs, and pork. Antimicrobial susceptibility was determined using the broth microdilution method with EUVSEC plates (TREK Diagnostic Systems), covering 14 antimicrobial agents. Minimum inhibitory concentration (MIC) values were interpreted according to EUCAST epidemiological cut-off values (ECOFFs). Whole-genome sequencing (WGS) was performed on the MiSeq platform (2×300 bp; Illumina). Sequence data were analyzed using Staramr tools implemented in Galaxy ARIES.

Results:

MIC above ECOFF values were observed for ampicillin (≥32 mg/L), sulfamethoxazole (≥512 mg/L), tetracycline (≥32 mg/L), trimethoprim (≥16 mg/L), and nalidixic acid (≥128 mg/L). Reduced susceptibility to ciprofloxacin correlated with mutations in gyrA. All isolates were susceptible to medically important meropenem and colistin. Two major clonal lineages predominated: ST19 (n = 12) and ST34 (n = 24). ST19 isolates most frequently harbored bla_CARB-2, floR, tet(G), sul1, and aadA2, together with the gyrA (D87N) mutation. ST34 isolates showed more diverse MDR profiles, including bla_TEM-1B, sul2, tet(A/B), aadA1, aph, and sporadically qnrS1.

Conclusions:

The study demonstrates the circulation of MDR Salmonella enterica serovar Typhimurium ST19 and ST34 clones in Polish pig production between 2014 and 2019, highlighting the value of integrated AMR surveillance within the One Health approach.

Appropriate antibiotic dosage is crucial for improving outcomes in critically ill patients facing pneumonia. Our research aimed to evaluate the development of the steady-state concentration (Css) of clarithromycin (CLAR) in this specific patient population with different routes of administration, to identify the influencing factors, and to examine the relationship between clinical outcomes and Css. This study was conducted as a single-center prospective observational study in the ICU of a pulmonology department between February 2025 and December 2025. The study target group included all adult patients (n=72) treated primarily with empirical CLAR (2x500mg/day) due to pneumonia. Blood sample collection was performed on day 3 of the CLAR administration, when five samples were taken as follows: at steady-state before drug administration and 1, 2, and 3 hours after intravenous (IV), oral (PO), and nasogastric (NG) administration, and one sample for albumin level. Determination of CLAR serum concentrations was determined by LC-MS/MS using a CLAR European Pharmacopeia Reference Standard by Merck. CLAR serum levels followed the expected pharmacokinetics for all three routes of administration. The CLAR Css was 3-fold higher for PO (n=30) than for IV (n=27) administration and 2.7-fold higher for NG (n=15) administration. Severe reduction in CrCl (˂ 59ml/min) increased serum levels for all administration routes. CLAR serum levels increased proportionally with increasing albumin serum levels and with the increasing CCI (Charles Comorbidity Index). No difference in length of stay (LOS) and survival was found between IV and PO administration (81 and 83%); however, the probability of survival was significantly lower (40%) in the case of NG administration. PO administration presented the highest CLAR Css levels. CrCl, albumin levels, and CCI were found to be influencing factors of CLAR Css. Although PO and IV administration resulted in similar clinical outcomes, the lower survival rate associated with higher Css ​​in the case of NG administration requires further investigation.

Background:
Mammaliicoccus sciuri, previously known as Staphylococcus sciuri, is a commensal bacterium widely distributed in animals and an opportunistic pathogen associated with infections in animals and humans. M. sciuri may act as a reservoir of antimicrobial resistance determinants, including the staphylococcal cassette chromosome mec (SCCmec) element, which confers methicillin resistance in methicillin-resistant Staphyloccoccus aureus (MRSA) via the mecA or mecC gene. In this study, we characterized methicillin-resistant M. sciuri (MRMS) isolated from Australian wildlife.
Method:
Skin and nasal swabs were collected from 180 wild animals upon admission to a wildlife hospital in Western Australia, and from 97 animals after seven days of hospitalization. ChromID MRSA selective agar was used for the isolation of MRMS. Whole genome sequencing was performed using the Illumina NovaSeq 6000 platform and the Oxford Nanopore MinION. The PubMLST website was used to determine the sequence type (ST). SCCmec elements were annotated and analyzed using the Geneious Prime software.
Results:
Thirty-one MRMSs were isolated from 4.4% (8/180) of the animals upon admission and 23.7% of animals (23/97) after hospitalization. Three STs were identified—ST81 (n=2), ST321 (n=16) and ST337 (n=13). All MRMS isolates harboured an SCCmec element. The ST81 and ST337 MRMSs harboured an mecA-positive SCCmec III(3A); an SCCmec was reported in hospital-associated MRSA clones. In contrast, the ST321 MRMS harboured an SCCmec-mecC hybrid element which contained the mecA, mecC and blaZ resistance genes. The SCCmec-mecC hybrid consisted of the SCCmec III(3A) element fused to a partial SCCmec XI element.
Conclusion:
Methicillin-resistant M. sciuri isolated from Australian wildlife carries mecA or mecC on an SCCmec element. This study provides the first evidence of an SCCmec-mecC hybrid in M. sciuri in Australia.

Antibiotic resistance is an urgent global public health threat, with livestock recognized as a potential reservoir for antibiotic resistance genes (ARGs). Despite the extensive antibiotic use in dairy farms, little is known about ARG dynamics in these environments. This study was conducted on five intensive dairy farms in Greece to explore the presence of ARGs across the production cycle and potential exposure sources. Feces from lactating cows, pre-weaned and weaned calves, bulk-tank milk and colostrum, and environmental samples, including dust from feeding alleys and beams and air samples taken during routine farm activities, were collected. Stored solid and liquid manure and material from corresponding biogas treatment plants were also sampled. Shotgun metagenomic short-read sequencing was conducted on extracted DNAs to identify the antibiotic resistomes (ARG loads) and characterize microbiomes. Sequencing reads were aligned to reference ARGs (CARD, MEGARes, and ResFinder) and microbiome (Kraken) databases. ARGs to aminoglycosides, macrolide–lincosamide–streptogramin, tetracycline, sulfonamide–trimethoprim and β-lactams were abundant across samples. Pre-weaned calves carried high ARG loads, contrary to colostrum, reflecting increased antibiotic selective pressure in this age. Intriguingly, beam-dust samples harbored high load and diverse ARGs, including aac(6), aadA, aph(6), ant(6), aac(3), erm(A/B/F/X/C/35), mef(A), lnu(C/G), tet(A/H/K/L/M/Q/X), dfrA/D, sul1/2, and mcr and the ESBLs bla_TEM, bla_OXA, and bla_CTX-M. Unexpectedly, bla_IMP conferring resistance to carbapenems was detected in both animal and environmental samples, despite these antibiotics are not authorized for use in livestock. ARG maintenance in dust, along with lower but similar loads in air, poses a potential exposure risk for humans. Finally, biogas treatment samples, regardless of their differing microbiomes, were not free of ARGs and thereby could create, as fertilizers, an important channel for ARG transmission to humans and animals. In conclusion, avoidance of antibiotic misuse, application of strict biosafety measures and establishment of systematic surveillance are imperative for intensive dairy farming.

Aim: Companion animals such as dogs and cats are increasingly recognized as potential reservoirs of antimicrobial resistance (AMR) determinants with relevance to both veterinary and human medicine. This study aimed to characterize antimicrobial resistance profiles of Escherichia coli isolated from dogs and cats in 2024 using a combined phenotypic and genomic approach.

Materials and methods: A total of 115 fecal samples collected from 63 dogs and 52 cats from animal shelters were screened for the presence of cephalosporin-resistant Escherichia coli. A total of 65 isolates were obtained and tested for antimicrobial resistance using the broth microdilution method with EUVSEC3 and EUVSEC2 plates (TREK Diagnostic Systems). Results were interpreted according to the EUCAST (European Committee on Antimicrobial Susceptibility Testing) ECOFFs. Whole-genome sequencing (WGS, 2×300 bp, NextSeq platform, Illumina) was performed for selected isolates to identify AMR genes and plasmid replicons.

Results: Phenotypic testing revealed a high level of resistance to critically important antimicrobials. Resistance to third-generation cephalosporins was observed in nearly all isolates (100% for cefotaxime and 98.5% for ceftazidime), while resistance to ampicillin reached 100%. Similar to ampicillin, ciprofloxacin resistance was observed in all isolates. High levels of resistance were also detected for nalidixic acid (92.3%), tetracycline (98.5%), chloramphenicol (95.4%), and gentamicin (90.8%). In contrast, all isolates remained fully susceptible to critically important last-resort antimicrobials, including meropenem, imipenem, colistin, and amikacin. Resistance to tigecycline, trimethoprim and sulfamethoxazole was detected at lower frequencies.

WGS revealed a predominance of E. coli ST457, suggesting clonal dissemination among companion animals. Most isolates carried ESBL genes, primarily bla_CTX-M-32, with single isolates harbouring bla_CTX-M-15 or bla_CTX-M-55. The IncF replicons (IncFIA/IncFIB) were common.

Conclusions: Dogs and cats may serve as an important reservoir of multidrug-resistant and ESBL-producing E. coli, highlighting the need for AMR surveillance in companion animals within a One Health framework.

Pseudomonas aeruginosa is an opportunistic Gram-negative bacteria identified as the main cause of serious nosocomial infections in Peru, especially in vulnerable patients, such as those hospitalized in critical care units (CCUs). Often, these infections are difficult to treat due to high antimicrobial resistance, enhanced virulence causing greater damage to the host, a tendency towards chronicity, and increases the risk of mortality. Thus, surveillance of this species in the aforementioned wards is encouraged.

Between July and September 2025, we collected the following medical devices, vascular catheters (VCs), urinary catheters (UCs), and endotracheal tubes (ETTs), from adult patients hospitalized in the CCU of a level-III reference hospital. Forty-two Pseudomonas aeruginosa isolates from different devices were recovered from MacConkey Agar and confirmed by PCR. Antimicrobial susceptibility was performed by disk diffusion using CLSI 2025 guidelines. Type 3 Secretion system virulence factor genes (T3SS) were detected by PCR, as well as carbapenemase genes bla_VIM, bla_IMP, bla_NDM and bla_KPC.

Out of 42 strains of P. aeruginosa from medical devices, 76% (32/42) were carbapenem-resistant; bla_IMP was identified in 12/32 isolates and bla_VIM in 5/32, the latter being VIM/IMP co-producers. The bla_KPC gene was found in 6/32 isolates and none carried bla_NDM. Regarding T3SS, we found the presence of exoU (15/42) and exoS (30/42), with three isolates being exoU+/exoS+. Most isolates also carried exoY (42/42) and exoT (39/42).

These results showed high carbapenem resistance in P. aeruginosa isolated from medical devices at a III-level Peruvian hospital and shed light on its T3SS virulence factors.Similar molecular epidemiology studies should be replicated.

Salmonella enterica is a major cause of foodborne illness, resulting in over 90 million cases and 150,000 deaths annually worldwide. Found in water and foods like meat and milk, it generally causes gastroenteritis, requiring antibiotic treatment only in severe cases. However, increasing antibiotic resistance in this species presents a significant public health challenge globally. Objective: To genetically characterize Salmonella strains isolated from raw retail chicken in the Ñuble and Maule regions of Chile. Methodology: A total of 225 raw chicken meat samples (175 from Maule and 50 from Ñuble) were analyzed under the Salmonella surveillance program using sampling criteria n=5, c=0. Isolates were identified by the VIDAS system, confirmed by MALDI‑TOF, and sequenced on the MiSeq. Classic MLST, core genome MLST, and Salmonella In Silico Typing Resource (SISTR v1.1.3) were performed. Antibiotic resistance genes (ARG) were detected using AMRFinderPlus and virulence genes (VG) by AMRfinderPlus templates (MBioSEQ Rido Typer v11.1). Nine Salmonella strains were isolated from independent samples, of which eight were S. Infantis ST32 (CC31; 6,7,14: r:1,5) and one was S. Bredeney ST897 (CC33; 1,4,12,27: l, v:1,7). Three clusters of closely related strains were observed with 0-2 allele differences, and three unrelated strains were identified. IncFIB plasmids were common in S. Infantis and Col_rep_cluster in S. Bredeney. S. Infantis strains presented the ARGs aac(3)-IVa, aph(3')-Ia, aph(4)-Ia, aadA1, mdsA/mdsB, fosA3, floR, qacEdelta1, gyrA_D87Y, sul1, tet(A) and dfrA14. bla_CTX-M-65 (ESBL) was detected only in IncFIB plasmids . In S. Bredeney, the ARGs detected were aac(3)-IId, aph(3')-Ia, aadA2/aph(3'')-Ib/aph(6)-Id, blaTEM-1, mdsA/mdsB, lnu(G), floR, qnrB19, sul2, tet(A)/tet(B), and dfrA12. A total 147 VG were detected, highlighting exotoxin, adherence, and effector delivery systems. Conclusion: The analyzed Salmonella strains exhibited various ARG and VG, underscoring the need for continuous genomic surveillance to mitigate public health risks in Chile.

Enterococcus spp are present in the gastrointestinal tract of animals, humans and in the environment. The most important are E. faecalis and E. faecium, but other enterococci can produce nosocomial infections. Enterococci have intrinsic and acquire mechanisms of antimicrobial resistance easily. Vancomycin is the last line of defense against these infections. The resistance acquired through the VanA and VanB2 genes is easily transmitted

The aim of this study is to determine if enterococci isolated from wild mammals of the Aragón Community (Spain), exhibit resistance to important antibiotics and carry genes of vancomycin resistance.

Between 2022 and 2024, 99 rectal samples were collected from recently dead mammals at the Wildlife Recovery Center-La Alfranca. After isolation on Slanetz-Barley agar, they were identified in MALDI-TOF-MS. The Kirby-Bauer test was applied to detect susceptibility to antimicrobials. The vanA and vanB genes were searched by PCR, with specific primers.

The mammal species were 33 badger, 23 beech marten, 11 American mink, 9 hedgehog, 6 common otter, 4 wild cat, 4 red fox, 3 common genet, 3 bat, 1 wolf, 1 guinea pig and 1 ferret.

It was isolated 126 enterococci: 63 E. faecalis, 31 E. faecium, 14 E. hirae, 11 E. mundtii, 2 E. avium, 2 E. gllinarum, 1 E. durans, 1 E. villorum 1 E. casseliflavus

The intermediate halo for the erythromycin, ciprofloxacin, and vancomycin was observed in 82, 56, and 29 enterococci, respectively. Thirty-three enterococci were resistant to tetracycline. None enterococci was resistant to clhoramphenicol, linezolid and teicoplanin. One E. faecalis was vancomicyn resistant. Ninenty strains were selecte to search for VanA and VanB2 genes, and were negative.

Conclusion: Enterococci isolated from 99 wild mammals in Aragón (Spain) showed high susceptibility to the antibiotics tested and did not carry vanA or vanB2 genes.

Introduction: Carbapenem-resistant Escherichia coli (CREC) poses a critical public health threat globally. High-risk clones ST131 and ST69 drive the pandemic, yet their epidemiology in sub-Saharan Africa remains poorly characterized. We investigated the genomic features and epidemiological patterns of E. coli from human, animal, and environmental sources in Zambia using a comprehensive One Health approach.

Methods: Whole-genome sequencing was performed on 97 E. coli isolates (57 clinical, 40 environmental) collected from Lusaka, Zambia. Antimicrobial susceptibility testing, MLST typing, phylogroup assignment, and identification of AMR genes, plasmid replicons, and virulence factors were conducted. Statistical analyses included chi-square tests, Fisher's exact test, and principal component analysis to identify significant associations.

Results: Overall, 82.5% of isolates were multidrug-resistant. Carbapenem resistance was detected in 16.5% of isolates, significantly higher in environmental (25.0%) than clinical (10.5%) sources. The carbapenemase blaNDM-5 was exclusively found in environmental isolates (7.2%). ST131 dominated clinical isolates (41.2%), while ST69 was predominant environmentally (45.0%). Phylogroup B2 was most common clinically (50.9%), whereas phylogroup D was more prevalent environmentally (32.5%). Significant associations existed between specific STs and AMR genes (blaTEM-1, blaOXA-1 with ST131; p<0.01).

Conclusions: Environmental reservoirs in Zambia harbor a significant and concerning CREC burden, particularly ST69 and blaNDM-5-producing isolates. The distinct distribution of ST131 and ST69 between clinical and environmental settings suggests separate epidemiological pathways and transmission routes. These findings highlight the environment as a critical hub for CREC evolution and transmission, emphasizing the urgent need for integrated One Health surveillance and infection control strategies in the region.