Andrei Alexandru Ivan

Antimicrobial resistance (AMR) is an important One Health challenge, yet evidence on resistant Escherichia coli and Salmonella spp. in Romania is dispersed across animal species, food matrices, environmental compartments, and surveillance systems. This comprehensive narrative review synthesizes and critically evaluates evidence across animal–food–environment interfaces and places it in the context of broader European AMR patterns. Particular attention is given to isolate origin, resistance phenotypes, multidrug resistance, major resistance determinants, molecular epidemiology, and the strength of evidence supporting cross-sector connections. Studies most frequently addressed poultry and swine, where resistance to ampicillin, fluoroquinolones, sulfonamides, and tetracyclines was repeatedly reported, together with extended-spectrum cephalosporin resistance, particularly in E. coli. Evidence from cattle, foods of animal origin, companion animals, wildlife, wastewater, and aquatic environments shows that resistant bacteria and antimicrobial resistance genes occur across multiple compartments. Substantial heterogeneity in sampling design, susceptibility testing, and molecular characterization limits direct comparison between studies, while epidemiologically linked investigations and whole-genome sequencing across connected reservoirs remain uncommon. Priorities include more standardized cross-sector surveillance, stronger environmental monitoring, expanded genomic epidemiology, improved data interoperability, and continued antimicrobial stewardship. By integrating fragmented national evidence, this review identifies both well-characterized sectors and interfaces where important evidence gaps remain.

Antimicrobial resistance represents a major One Health challenge affecting human, animal, and environmental health, and responsible antimicrobial use in companion animal medicine has become increasingly important. This narrative review synthesizes current evidence on antimicrobial stewardship interventions aimed at improving antibiotic prescribing in small animal veterinary practice. The review discusses the clinical, behavioral, owner-related, organizational, and regulatory factors that influence prescribing decisions, with emphasis on diagnostic uncertainty, access to microbiological testing, communication with pet owners, and practice-level prescribing culture. Key stewardship strategies include evidence-based clinical guidelines, diagnostic stewardship, education and training, audit and feedback, electronic clinical decision-support systems, antimicrobial resistance surveillance, infection prevention, and multifaceted implementation programs. Evidence from predominantly observational and before-and-after studies suggests that these interventions may be associated with reductions in unnecessary antimicrobial prescribing and improvements in prescribing appropriateness, although the strength of causal evidence remains limited. However, further research is needed because current studies differ in methodology, often have short follow-up periods, include limited data from routine primary veterinary practices, and rarely demonstrate a direct reduction in antimicrobial resistance. Future progress will depend on standardized outcome measures, integration of digital health technologies, rapid diagnostics, artificial intelligence, antimicrobial resistance surveillance, and stronger One Health collaboration. Overall, antimicrobial stewardship in companion animal medicine should be regarded as a continuous quality-improvement process designed to preserve antimicrobial efficacy while maintaining optimal patient care.

Antimicrobial resistance (AMR) has emerged as one of the most significant global health challenges affecting both human and veterinary medicine. The growing prevalence of resistant bacterial strains in livestock and companion animals not only compromises treatment efficacy but also poses serious public health risks through potential zoonotic transmission. Recent molecular and genomic studies have shown the widespread dissemination of resistance genes across different ecological compartments, emphasizing the need for integrated monitoring systems. Antimicrobial stewardship programs and evidence-based interventions are therefore essential in veterinary medicine to mitigate these trends. This is particularly important because the emergence of multidrug-resistant (MDR) pathogens is increasingly associated with mobile genetic elements, such as plasmids, transposons, and integrons, which facilitate horizontal gene transfer within and across bacterial species.

Background/Objectives: Antimicrobial resistance (AMR) in companion animals is an emerging public health threat due to zoonotic potential and limited therapeutic options. Dogs with otitis externa may harbor multidrug-resistant (MDR) bacteria, including Escherichia coli (E. coli), Proteus mirabilis (P. mirabilis), and Enterobacter cloacae complex (E. cloacae complex), some producing extended-spectrum beta-lactamase (ESBL) or AmpC β-lactamases. This study aimed to assess the prevalence, AMR patterns, MDR occurrence, β-lactamase production, and co-infection profiles of these pathogens in canine otitis externa. Methods: Ear canal samples were collected from 592 dogs presenting clinical signs of otitis externa, with one sample per dog included in the analysis. Samples were collected from veterinary clinics in Timiș County, Romania, from 2022 to 2025. Samples were cultured on blood agar and MacConkey agar, followed by biochemical testing and MALDI-TOF mass spectrometry for bacterial identification. Antimicrobial susceptibility testing against 15 agents across six classes was performed using the VITEK^® 2 system. MDR and β-lactamase production (ESBL, AmpC) were determined according to CLSI 2018 veterinary guidelines. Co-isolation with bacterial and fungal species were recorded. Results: E. coli, P. mirabilis, and E. cloacae complex were isolated in 9.12%, 6.25%, and 1.2% of cases, respectively. E. coli exhibited the highest resistance to aminoglycosides (tobramycin 72.2%, gentamicin 61.1%) and full susceptibility to carbapenems. P. mirabilis showed the highest resistance to ampicillin (54%) and trimethoprim + sulfamethoxazole (46%), with complete susceptibility to carbapenems and fluoroquinolones. E. cloacae complex displayed universal resistance to cephalosporins but remained susceptible to non-cephalosporin β-lactams (piperacillin–tazobactam), carbapenems and aminoglycosides. MDR prevalence was 35.2% for E. coli, 18.9% for P. mirabilis, and 14.3% for the E. cloacae complex. ESBL production was detected in 13% of E. coli and 8.1% of P. mirabilis isolates, while all E. cloacae complex isolates were AmpC-positive. Co-isolations were common, primarily involving Staphylococcus pseudintermedius (S. pseudintermedius) and Malassezia pachydermatis (M. pachydermatis). Conclusions: MDR and β-lactamase-producing bacteria were identified in dogs with otitis externa, emphasizing the importance of routine antimicrobial susceptibility testing, targeted therapy based on local resistance profiles, and continuous AMR surveillance to prevent treatment failure and mitigate zoonotic risk.

Background/Objectives: Recent investigations point to red foxes (Vulpes vulpes) as a very potent sentinel species for monitoring the dissemination of antimicrobial bacteria in wildlife habitats. Methods: This study investigated antimicrobial resistance in red foxes from 16 hunting grounds (peri-urban and peri-rural) in western Romania, between 2022 and 2024, in order to evaluate the species as “One Health” sentinels at the wildlife–human–animal interface. During this period, 137 bacterial strains previously identified from 216 samples were phenotypically tested using both the Kirby–Bauer disk diffusion method and the Vitek 2 Compact system. Results: Among the Gram-negative isolates, particularly Escherichia coli and Salmonella enterica, notable antimicrobial resistance and multidrug-resistant (MDR) phenotypes were observed, including resistance to third-generation cephalosporins (ceftazidime) and reduced susceptibility to carbapenems. Resistance patterns observed in Proteus spp. largely reflected intrinsic resistance traits. Methicillin-resistant and MDR staphylococci (Staphylococcus aureus, S. pseudintermedius and S. sciuri) were detected in both peri-urban and peri-rural hunting grounds, with higher frequencies observed in peri-rural areas. Although MDR prevalence was slightly higher in peri-urban compared to peri-rural sites, no statistically significant association was identified between area of isolation and antimicrobial resistance or MDR status. Antimicrobial susceptibility results obtained by disk diffusion and the Vitek 2 Compact system showed a high level of concordance for antibiotics tested in common. Conclusions: Overall, these findings support the use of red foxes as effective One Health sentinels for monitoring environmental antimicrobial resistance occurrence across wildlife, domestic animals, and human-impacted habitats.

Background/Objectives: Canine otitis externa (OE) is frequently complicated by Pseudomonas aeruginosa (P. aeruginosa) infections, which are often associated with treatment failure due to intrinsic and acquired antimicrobial resistance. This study aimed to assess the prevalence and antimicrobial susceptibility of P. aeruginosa isolates from dogs with OE in Timiș County, Romania, with a focus on aminoglycosides and fluoroquinolones, to provide region-specific, clinically relevant data and address potential public health implications. Methods: Exudate samples were collected from 435 dogs diagnosed with OE across multiple veterinary clinics between 2022 and 2025. P. aeruginosa isolates were identified using standard culture methods, and antimicrobial susceptibility was determined using the VITEK^® 2 Compact system according to CLSI VET01, Fifth Edition (2018) guidelines. Tested antibiotics included amikacin, gentamicin, enrofloxacin, marbofloxacin, and pradofloxacin. Resistance profiles were analyzed at both the individual antibiotic and class levels. Results:P. aeruginosa was isolated in 14.0% (61/435) of dogs. All isolates were susceptible to amikacin and gentamicin, whereas resistance to enrofloxacin and marbofloxacin was 27.9%, and pradofloxacin resistance reached 63.9%. A total of 24.6% of isolates were susceptible to all tested antibiotics. The most frequent multidrug-resistant combination among fluoroquinolones was ENR (R) + MAR (R) + PRA (R), observed in 23.0% of isolates. Conclusions: This study provides recent, region-specific data on P. aeruginosa prevalence and antimicrobial susceptibility in canine OE, offering clinically relevant insights into aminoglycoside and fluoroquinolone resistance. The findings highlight the potential public health significance of resistant P. aeruginosa strains at the human–animal interface and underscore the importance of antimicrobial stewardship in veterinary practice.

Background/Objectives: Multidrug-resistant (MDR) Escherichia coli is a critical One Health challenge, with rising resistance in both humans and animals. The present study aimed to compare antimicrobial resistance (AMR) profiles of E. coli isolates from hospitalized patients and food-producing animals in Satu Mare, a county located in northwestern Romania. Methods: Between 2022–2023, 701 samples were collected, leading to 571 non-duplicate E. coli isolates (420 human, 151 animal). Human strains were recovered from 21 hospital departments and originated from feces, urine, blood, sputum, ear secretions, cerebrospinal fluid, purulent wound secretions, and puncture fluids. Animal isolates were obtained from ceca collected at local slaughterhouses serving farms in north-west Romania, including samples from turkeys, broilers, and pigs. Antimicrobial susceptibility testing was performed against eight antimicrobials (amikacin, ampicillin, cefotaxime, ceftazidime, cefepime, ciprofloxacin, gentamicin, sulfamethoxazole/trimethoprim) using standardized methods. Resistance classification followed international definitions of MDR. Statistical associations between host species and resistance were assessed with chi-square tests. Results: Resistance levels were consistently higher in E. coli strains isolated from animals compared with those from humans (p < 0.05). Among human isolates, resistance to ampicillin (41.9%), ciprofloxacin (41.4%), and sulfamethoxazole/trimethoprim (45.7%) approached, but did not exceed 50%. In contrast, E. coli strains recovered from animals showed markedly higher resistance, exceeding 50% for ampicillin (78.8%), ciprofloxacin (65.6%), and cefotaxime (55.0%). Amikacin retained full activity against all animal isolates, whereas 2.8% of human strains were resistant. Overall, multidrug resistance (MDR) was observed in 70.0% of E. coli isolates from humans and 79.7% from animals, with the highest resistance burden in pig-derived isolates. Conclusions: The study underscores the veterinary sector as a key contributor to the maintenance and spread of MDR E. coli. Even in clinically healthy animals, resistance levels exceeded those observed in human isolates. These findings emphasize the need for coordinated One Health monitoring and stricter antimicrobial use policies in livestock to reduce transmission risks across human and animal populations.

Background/Objectives: The widespread use of antibiotics in animal husbandry has led to an increase in antimicrobial-resistant Escherichia coli, particularly strains producing extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases. This study aimed to isolate and characterize such strains from fecal samples of broiler chickens (n = 71) and slaughtered turkeys (n = 31) in northwestern Romania. Methods: Antimicrobial susceptibility testing and PCR were used to evaluate phenotypic resistance patterns and detect the presence of resistance genes (AmpC, blaZ, and blaTEM). Results: The results showed that 55% of turkey and 61% of broiler isolates were presumptive ESBL/AmpC producers. Among all isolates, 50% were classified as extensively drug-resistant (XDR), 44% as multidrug-resistant (MDR), and only 6% were fully susceptible. Gene detection revealed an overall prevalence of 44.2% for AmpC, 72.7% for blaZ, and 58.1% for blaTEM, yielding a total penetrance of 51.09%. The diagnostic odds ratio (DOR) values, ranging from 0.67 to 81, suggest the efficacy of the antibiotic susceptibility testing method used in detecting the presence of these resistance genes. Conclusion: Overall, these findings highlight a significant burden of antimicrobial-resistant, poultry-associated E. coli strains, warranting stricter antimicrobial stewardship.