Healthy Livestock as Silent Reservoirs of Enterococci with Vancomycin Resistance Determinants in Sabah, Malaysian Borneo

Introduction: Antimicrobial resistance in food-producing animals is a growing One Health concern because clinically healthy livestock may harbour resistant bacteria without obvious signs of disease. In Sabah, Malaysian Borneo, information on enterococcal reservoirs and vancomycin resistance determinants in livestock remains scarce. This study investigated the carriage of Enterococcus species and vancomycin resistance genes in healthy cattle and poultry, with the aim of identifying potential silent reservoirs of resistance within local food-animal systems. Methods: A total of 256 faecal samples were collected from cattle and poultry farms in Kota Kinabalu, Sabah, between October 2019 and February 2020. Enterococcus isolates were recovered using selective culture and identified by standard bacteriological methods. Polymerase chain reaction assays targeting vanA, vanB and vanC1/2/3 were performed to detect acquired and intrinsic vancomycin resistance determinants. Results and Discussions: Enterococcus was recovered from 85.5% of samples, confirming widespread carriage among healthy livestock. E. faecalis was the dominant species, followed by E. faecium and other Enterococcus species. The acquired vancomycin resistance genes vanA and vanB were not detected in any isolate, suggesting that high-level transferable vancomycin resistance was not evident in the sampled farms. However, three E. casseliflavus isolates from poultry carried the intrinsic vanC2/3 gene, demonstrating that vancomycin resistance determinants are present within the gut microbiota of apparently healthy poultry. Conclusions: This study provides evidence that healthy livestock in Sabah can carry enterococci with vancomycin resistance determinants, even in the absence of acquired vanA and vanB genes. The detection of vanC-positive E. casseliflavus in poultry highlights a low-level but biologically relevant reservoir of glycopeptide resistance within the food-animal microbiota. Rather than representing routine surveillance alone, these findings establish an important early-warning baseline for One Health antimicrobial resistance monitoring in Malaysian Borneo and support more targeted molecular tracking of enterococci across livestock, food, environmental and human interfaces.