Over the past few decades, antimicrobial resistance (AMR) has emerged as a global health challenge in human and veterinary medicine. Research on AMR genes in captive wild animals has increased. However, the presence and molecular characteristics of tet(X)-carrying bacteria in these animals remain unknown.
Eighty-four samples were collected from captive wild animals. tet(X) variants were detected using polymerase chain reaction and the isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. All isolated strains were subjected to antimicrobial susceptibility testing and whole-genome sequencing. The virulence of an Escherichia coli strain carrying enterotoxin genes was assessed using a Galleria mellonella larval model.
We isolated two tet(X4)-positive E. coli strains and one tet(X4)-positive Raoultella ornithinolytica strain. Antimicrobial susceptibility tests revealed that all three tet(X4)-carrying bacteria were sensitive to the 13 tested antimicrobial agents, but exhibited resistance to tigecycline. Notably, one tet(X4)-carrying E. coli strain producing an enterotoxin had a toxic effect on G. mellonella larvae. Whole-genome sequencing analysis showed that the two tet(X4)-carrying E. coli strains had more than 95% similarity to tet(X4)-containing E. coli strains isolated from pigs and humans in China.
The genetic environment of tet(X4) closely resembled that of the plasmid described in previous studies. Our study identified tet(X4)-positive strains in wildlife and provided valuable epidemiological data for monitoring drug resistance. The identification of enterotoxin-producing E. coli strains also highlights the potential risks posed by virulence genes.
Camels, known as the enduring “ships of the desert,” host a complex gut microbiota that plays a crucial role in their survival in extreme environments. However, amidst the fascinating discoveries about the camel gut microbiota, concerns about antibiotic resistance have emerged as a significant global challenge affecting both human and animal populations. Indeed, the continued use of antibiotics in veterinary medicine has led to the widespread emergence of antibiotic-resistant bacteria, which has worsened through gene transfer.
This study offers a deeper examination of this pressing issue by harnessing the potent tools of metagenomics to explore the intricate interplay between the camel (Camelus ferus) gut microbiota and antibiotic resistance.
Samples from wild camels yielded varying amounts of raw and clean data, generating scaftigs and open reading frames. The camel fecal microbiome was dominated by bacteria (mainly Bacillota and Bacteriodota), followed by viruses, archaea, and eukaryota. The most abundant genera were the Bacteroides, Ruminococcus, and Clostridium. Functional annotation revealed enriched pathways in metabolism, genetic information processing, and cellular processes, with key pathways involving carbohydrate transport and metabolism, replication, and amino acid transport. CAZy database analysis showed high abundances of glycoside hydrolases and glycosyl transferases. Antibiotic resistance gene (ARG) analysis identified Bacillota and Bacteroidota as the main reservoirs, with vancomycin resistance genes being the most prevalent. This study identified three major resistance mechanisms: antibiotic target alteration, antibiotic target protection, and antibiotic efflux.
These findings contribute to a broader understanding of antibiotic resistance within animal microbiomes and provide a foundation for further investigations of strategies to manage and mitigate antibiotic resistance.
In sub-Saharan Africa, limited studies have investigated zoonotic pathogens that may be harboured by ticks infesting reptiles such as tortoises. Here, we report the presence of pathogenic Rickettsia in ticks (Amblyomma marmoreum) collected from the leopard tortoise (Geochelone pardalis) in rural Zambia. Using polymerase chain reaction, 56% (49/87) of ticks were positive for the Rickettsia outer membrane protein (ompB) gene. Multi-locus sequence and phylogenetic analysis based on the ompB, ompA, and citrate synthase (gltA) genes showed that the ticks carried R. africae, and other Rickettsia spp. closely related to R. raoultii, R. massiliae, R. tamurae and R. monacensis. Given the proximity between humans, livestock, and wildlife in these habitats, there exists a considerable risk of transmission of zoonotic Rickettsia to human populations in this rural setting. These results call for heightened awareness and further research into the dynamics of tick-borne diseases in regions where humans and animals coexist, particularly in the context of tortoise-associated ticks as vectors. Understanding and addressing these potential disease vectors is crucial for effective public health measures and the prevention of Rickettsia zoonoses.