Evaluation of disk diffusion method for testing the rifampicin, erythromycin, and tetracycline susceptibility of Clostridioides (prev. Clostridium) difficile.

INTRODUCTION: Antimicrobial resistance (AMR) is one of the greatest threats to animal and public health. Clostridioides (prev. Clostridium) difficile is a major burden to healthcare and a relevant AMR gene reservoir. Despite the known importance of AMR in C. difficile epidemiology and treatment, antimicrobial susceptibility testing for this pathogen is still based on the determination of the minimal inhibitory concentration (MIC) by the agar dilution method, which is technically demanding and labor-intensive. In this study, the disk diffusion method was used to evaluate the susceptibility of C. difficile to erythromycin, rifampicin, and tetracycline. MATERIAL AND METHODS: A total of 155 isolates isolated between 2011 and 2022 from humans and animals in Brazil were simultaneously tested using the disk diffusion method and the epsilometer test (Etest) for these three antimicrobials on Brucella blood agar supplemented with vitamin K and hemin. RESULTS: The results suggest that disk diffusion can be an interesting routine tool to identify erythromycin- and rifampicin-resistant C. difficile isolates (≥20 mm cut-off) and wild type (WT) strains (≥28 mm). However, the disk diffusion protocol tested in this study does not seem suitable for tetracycline because of the common misclassification of resistant strains.

Lethal acute diarrhea associated with Clostridioides difficile toxin A and B in a buffy-tufted-ear marmoset (Callithrix aurita).

This is a case of lethal acute diarrhea associated with a mild neutrophilic enteritis in a buffy-tufted-ear marmoset (Callithrix aurita) with detection of A/B toxins and isolation of a toxigenic clade 3 Clostridioides difficile strain (A+ B+ CDT+ , ST5), which should be considered as a potential cause of enteritis in this species.

Characterization of Escherichia coli in Dogs with Pyometra and the Influence of Diet on the Intestinal Colonization of Extraintestinal Pathogenic E. coli (ExPEC).

Despite its high frequency and clinical relevance, the pathogenesis of canine pyometra remains poorly understood. The most accepted hypothesis is that bacteria involved ascend from the intestinal tract, causing the uterine infection. Extraintestinal pathogenic Escherichia coli (ExPEC) is the most frequent pathogen in canine pyometra, accounting for 57-100% of cases. The aim of the present study was to determine the frequency of phylogenetic groups and virulence factors in E. coli strains isolated from the uterine and rectal swabs of bitches with pyometra (n = 72) and from rectal swabs from healthy bitches fed commercial dry feed (n = 53) or a raw meat-based diet (RMBD; n = 38). A total of 512 strains of E. coli were isolated and divided into five categories according to the origin of the sample: 120 isolates from the uterine content of dogs with E. coli pyometra, 102 from the feces of bitches with E. coli pyometra, 75 from the feces of bitches without E. coli pyometra, 130 feces samples from healthy dogs fed commercial feed, and 85 feces samples from healthy dogs fed a raw meat-based diet. E. coli strains belonging to the B2 phylogroup and positive for virulence factor genes associated with adhesion (fimbriae type P [papC]) and production of toxins (α-hemolysin [hlyA] and uropathogenic specific protein [usp]) predominated in the uterine content and rectal swabs of bitches with E. coli pyometra. Interestingly, a lower growth rate of E. coli from the B2 phylogroup was observed in dogs fed a RMBD than in those fed commercial dry feed. The present study suggests that intestinal colonization by certain types of E. coli could be a risk factor for the occurrence of E. coli pyometra in bitches and that diet can influence intestinal colonization by such strains.

Laboratory diagnosis of Clostridioides (Clostridium) difficile infection in domestic animals: A short review.

Despite the known importance of Clostridioides (Clostridium) difficile infection (CDI) in animals, there are no published guidelines for the diagnosis of CDI. The performance of the available commercial methods, all standardized for human stool samples, can vary according to the animal species. Thus, the aim of the present study was to review the literature on the detection of C. difficile in pigs, horses, and dogs. The detection of toxins A and B using enzyme immunoassays seems to have low performance in piglet and dog samples, while it shows high sensitivity for the diagnosis of CDI in foals. On the other hand, tests for the detection of glutamate dehydrogenase (GDH) have a high sensitivity towards detection of C. difficile in animal samples, suggesting that it can be an adequate screening method. A few studies have evaluated real-time PCR or nucleic acid amplification tests in animal samples and, so far, these methods have also shown a low performance for the detection of C. difficile in animals. Although the intestinal lesions caused by CDI can vary among animal species, histopathology can be a useful auxiliary tool for postmortem diagnosis in animals.