Pyometra, characterized by the accumulation of purulent exudate in the uterus, is the most prevalent reproductive disease in canines. While the disease often begins with mild local symptoms, it can escalate into peritonitis, sepsis, and multi-organ dysfunction, thereby posing a significant threat to life. Despite the high incidence and recognized significance of canine pyometra, gaps persist in our understanding of its epidemiology, etiology, and pathogenesis. Recent studies have, however, broadened our comprehension of this disease, shedding light on potential new infection sources, etiologies, and the application of clinical predictive biomarkers and new therapeutic protocols. This study aimed to review the current understanding of canine pyometra, with particular emphasis on the latest research concerning its etiology and epidemiology. Furthermore, it addressed key research questions and proposed directions for future investigations into various facets of canine pyometra.

Methicillin-resistant Staphylococci (MRS) cause infections at various sites and exhibit multidrug resistance. Despite their importance in veterinary medicine, only little is known about Staphylococcus spp. colonizing and infecting cats. Therefore, in this study, we aimed to isolate and identify Staphylococcus spp. colonizing hospitalized and non-hospitalized domestic cats and analyze their antimicrobial resistance profiles, genetic diversity, and risk factors associated with MRS colonization. A total of 218 oral and axillary swabs were obtained from 109 cats, including 77 non-hospitalized and 32 hospitalized cats. After plating on selective media, the isolates were identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and rpoB and 16S rRNA gene sequencing. Subsequently, antimicrobial sensitivity of the strains was assessed, and they were screened for mecA gene. Methicillin-resistant S. haemolyticus (MRSH) isolates were subjected to multilocus sequence typing, whereas methicillin-resistant S. pseudintermedius (MRSP) and S. felis isolates were subjected to whole genome sequencing. S. felis was most commonly isolated from non-hospitalized cats (28.1%), whereas S. pseudintermedius and MRS were commonly isolated from hospitalized cats (25%). MRSH isolates from hospitalized animals were classified as ST3. The identified MRSP strains belonged to two well-known sequence types, ST551 and ST71. Moreover, antimicrobial use (p = 0.0001), hospitalization (p = 0.0141), and comorbidities (p = 0.002) were associated with increased MRS prevalence in cats.

Background/Objectives: Antimicrobial resistance is a major global health threat. Among the most problematic pathogens are carbapenem-resistant Acinetobacter baumannii and Klebsiella pneumoniae, which are significant causes of mortality in humans, particularly in the context of nosocomial infections. In companion animals, these bacteria have been reported mainly as colonizers of healthy animals or, less frequently, in community-acquired infections. However, no confirmed cases of healthcare-associated infections caused by these species have been documented in this population. This study reports the first confirmed fatal cases of infection with carbapenem-resistant A. baumannii and KPC-producing K. pneumoniae in dogs. Methods: Three hospitalized dogs developed infections associated with distinct anatomical devices, including a venous catheter, an endotracheal tube, and a Penrose drain. Bacterial isolation followed by antimicrobial susceptibility testing identified carbapenem-resistant A. baumannii and K. pneumoniae. The isolates were subsequently subjected to additional antimicrobial resistance tests and whole-genome sequencing (WGS). Results: WGS confirmed the presence of the OXA-23 carbapenemase gene in both A. baumannii isolates and the KPC-2 carbapenemase gene was detected in the K. pneumoniae strain. All three strains exhibited resistance to multiple antimicrobial classes, including β-lactams (amoxicillin-clavulanic acid, ampicillin, cephalotin, piperacillin-tazobactam, cefoxitin, ceftiofur, cefotaxime, ertapenem, imipenem and meropenem), aminoglycosides (gentamicin, neomycin), tetracyclines (doxycycline, tetracycline and oxytetracycline), fluoroquinolones (ciprofloxacin, enrofloxacin), and folate pathway antagonists (trimethoprim-sulfamethoxazole). Multilocus sequence typing identified two high-risk clones: K. pneumoniae ST340 (CC258) and A. baumannii ST15 (CC15). Single nucleotide polymorphism analysis confirmed a high degree of genetic similarity between these isolates and strains previously associated with human infections in Brazil. Conclusions: These findings provide the first evidence of fatal, healthcare-associated infections caused by these multidrug-resistant pathogens in dogs and underscore the need to strengthen surveillance and infection control practices in veterinary hospitals. Furthermore, the results raise concerns about the potential of companion animals to act as reservoirs for multidrug-resistant organisms of public health relevance.

Pyometra is the most common reproductive disease in female dogs, characterized by the accumulation of purulent content in the uterus. Its etiology is multifactorial, primarily involving hormonal and bacterial factors, with Escherichia coli being the most frequently isolated pathogen. International guidelines recommend bacterial culture and antimicrobial susceptibility testing of uterine content before or, if not feasible, after ovariohysterectomy. However, due to the time required to perform these tests, empirical antibiotic therapy is commonly prescribed, potentially contributing to antimicrobial resistance and treatment failure. Given that E. coli causing pyometra often originates from the intestinal microbiota, we hypothesized that isolates from rectal swabs could serve as predictors of the antimicrobial resistance profile of the E. coli causing pyometra. To evaluate this possibility, this study assessed the antimicrobial susceptibility of E. coli isolates from the uterine content and rectal swabs of bitches with pyometra and evaluated whether there is an association between the resistance profiles at these two sites. Samples from 72 dogs diagnosed with pyometra were collected for bacterial culture and antimicrobial susceptibility testing. E. coli was identified in 40 uterine content samples (55.6%) and 59 rectal swabs (81.9%) using species-specific PCR. E. coli isolates from rectal swabs exhibited higher resistance rates to commonly used antibiotics for pyometra treatment, including amoxicillin/clavulanic acid, ampicillin, enrofloxacin, and doxycycline (P < 0.05). The presence of susceptible isolates in rectal swabs is strongly associated with susceptibility in uterine isolates, yielding a positive predictive value up to 100%. These findings suggested that rectal swab isolates could serve as a reliable predictor of uterine E. coli susceptibility, providing a rapid and non-invasive tool to guide antimicrobial selection for pyometra treatment.

Clostridioides difficile is an anaerobic bacterium that causes disease in both animals and humans. Despite the known significance of this agent, there are no commercial vaccines available for humans, and only one immunogen is marketed for swine. However, no studies have evaluated this vaccine. Background/Objectives: Therefore, the aim of this study was to assess the potency of the first commercial vaccine for C. difficile infection in piglets and to compare the humoral response in rabbits and sows. Methods: Pregnant sows were divided into two groups: a vaccinated group (n = 12), receiving two doses before farrowing, according to the manufacturer’s recommendation, and an unvaccinated control group (n = 6). Blood samples were taken from sows and also from piglets up to two days after birth. In addition, two groups of New Zealand rabbits (Oryctolagus cuniculus) received either a half-dose (G1) or a full-dose (G2) of the vaccine, with a control group receiving sterile saline (0.85%). Rabbits were vaccinated twice, 21 days apart, with blood samples collected before each dose and 14 days after the final dose. A serum neutralization assay in Vero cells was performed to evaluate the titers of neutralizing antibodies. Results: The vaccine demonstrated immunogenicity by stimulating the production of neutralizing antibodies in both rabbits and sows. Additionally, these antibodies were passively transferred to piglets through colostrum, reaching levels comparable to those found in sows. Furthermore, vaccinated rabbits developed antibody titers that do not significantly differ from those obtained in sows and piglets. Conclusions: The tested vaccine can induce a humoral immune response against C. difficile A/B toxins in sows and these antibodies are passively transferred to neonatal piglets through colostrum. Also, the vaccination of rabbits might be a useful alternative for evaluating the potency of vaccines against C. difficile.