Occurrence of Antimicrobial Resistance Genes in the Oral Cavity of Cats with Chronic Gingivostomatitis

Simple Summary Oral disease in cats is a significant concern in the small animal practice setting. The specific cause of this disease is inadequately understood; however, antibiotics are commonly used for the management, although many cats respond poorly to these treatments. Antibiotics have been overused and misused in the context of both human and veterinary medicine. Consequently, many antimicrobial drugs are becoming less effective in treating infections. This study aimed to evaluate the presence of antimicrobial resistance genes in swabs obtained from the mouth of cats. Moreover, the study looked at simultaneous occurrence between these genes and one type of oral fungi. We found that antimicrobial resistance genes are extremely common in both clinically healthy and sick cats. Furthermore, we established that Malassezia (a type of fungi) co-occurs with some resistance genes. The findings are important because antimicrobial resistance genes present in the mouth of cats have the potential to transfer to humans and thereby make certain antibiotics less effective. Feline chronic gingivostomatitis (FCGS) is a severe immune-mediated inflammatory disease with concurrent oral dysbiosis (bacterial and fungal). Broad-spectrum antibiotics are used empirically in FCGS. Still, neither the occurrence of antimicrobial-resistant (AMR) bacteria nor potential patterns of co-occurrence between AMR genes and fungi have been documented in FCGS. This study explored the differential occurrence of AMR genes and the co-occurrence of AMR genes with oral fungal species. Briefly, 14 clinically healthy (CH) cats and 14 cats with FCGS were included. Using a sterile swab, oral tissue surfaces were sampled and submitted for 16S rRNA and ITS-2 next-generation DNA sequencing. Microbial DNA was analyzed using a proprietary curated database targeting AMR genes found in bacterial pathogens. The co-occurrence of AMR genes and fungi was tested using point biserial correlation. A total of 21 and 23 different AMR genes were detected in CH and FCGS cats, respectively. A comparison of AMR-gene frequencies between groups revealed statistically significant differences in the occurrence of genes conferring resistance to aminoglycosides (ant4Ib), beta-lactam (mecA), and macrolides (mphD and mphC). Two AMR genes (mecA and mphD) showed statistically significant co-occurrence with Malassezia restricta. In conclusion, resistance to clinically relevant antibiotics, such as beta-lactams and macrolides, is a significant cause for concern in the context of both feline and human medicine.