STUDY OF BACTERIAL CARRIAGE IN DARKLING BEETLES (ALPHITOBIUS DIAPERINUS) COLLECTED FROM INDUSTRIAL BROILER FLOCKS IN NORTH-EST OF TUNISIA

Alphitobius diaperinus is regarded as a highly resilient pest in poultry production systems that use litter-based rearing . It is also known as a potential reservoir of several avian pathogens. The present study aimed to determine darkling beetle carriage of bacterial pathogens in Tunisian poultry houses. A total of 25 industrial broiler flocks naturally infested by darkling beetles and located in the North-East of Tunisia were sampled. A pooled sample of adult beetles (5 g) was collected from five distinct locations within each broiler house. Insects were placed in sterile containers and transported to the laboratory under cooled conditions. All samples were examined for entomological identification. Bacteriological analysis was performed to detect external and internal bacterial carriage, according to the standard protocols. Antimicrobial susceptibility for all Escherichia coli isolates was tested by the disk diffusion method on Mueller–Hinton agar using commercial disks. Antimicrobial susceptibility testing was not performed for the remaining bacterial isolates. Entomological identification showed that all sampled beetles belong to Alphitobius diaperinus species. A total of 108 isolates were detected from the surface (57 isolates) and the interior (51 isolates) of adult insects. Gram-negative (63.89%) (Escherichia coli, Enterobacter spp., Klebsiella pneumoniae, Proteus vulgarus, Citrobacter spp., Pseudomonas spp., Pseudomonas aeruginosa) and coagulase-negative staphylococci (36.11%) (Gram-positive) bacteria were isolated, with the global predominance of coagulase-negative staphylococci, followed by E. coli (23.15%), Pseudomonas spp. (13.89%) and Pseudomonas aeruginosa (10.19%). No Salmonella spp. was detected. Antibiotic resistance profile showed that all Escherichia coli isolates were multi-resistant. High resistance was observed to doxycycline (25/25; 100%), amoxicillin (24/25; 96%), cephalothin (23/25; 92%), streptomycin (22/25; 88%), tetracycline (22/25; 88%), enrofloxacin (22/25; 88%). A high level of resistance was observed to trimethoprim-sulfamethoxazole (13 out of 25 isolates; 52%) and gentamicin (9/25; 36%). However, a low level of resistance was observed to florfenicol (7/25; 28%) and colistin (3/25; 12%). Our results confirm the potential vector role of beetles in the spread of bacteria pathogens and antibiotic resistance.