Isolation, identification, and antimicrobial susceptibility of Clostridium perfringens isolates from acute necrotic enteritis of broiler chickens

The aim of this study was to isolate, identify and determine the antimicrobial susceptibility of Clostridium perfringens [CP] isolates from acute necrotic enteritis of broiler chickens. All broiler carcasses diagnosed as necrotic enteritis [NE] were sampled, subjected to microbial tests and 40 isolates were identified according to standard procedures. The antimicrobial susceptibility of CP isolates to 20 antibacterial agents was then determined. The results show widespread resistance among CP isolates. The most frequent resistance was observed to neomycin sulfate [87.5%], and then to lincomycin and tetracycline [both 80%]. No isolate was resistant to chloramphenicol and the least frequency of resistance was observed to vancomycin [10%], sulfamethoxazole+trimethoprim [17.5%], and penicillin [20%]. All isolates were multiple drug resistant types. There were 39 resistant patterns among the CP isolates, 95% of which were distributed in 38 resistant patterns. These multiple and variable resistance patterns observed among the CP isolates, even among different isolates from one farm, demonstrate a challenge for veterinarians in the field to choose the correct compound to combat the occurrence of NE

Experimental induction of necrotic enteritis in broiler chickens by clostridium perfringens isolates from the outbreaks in Iran

To establish an stable challenge system for induction of necrotic enteritis [NE] in broiler chickens, different potential factors and predisposing conditions were imposed in 6 separate different experiments using 525 day-old chicks in total. Despite the presence of some predisposing factors and using 4 isolates of Clostridium perfringens [CP] from acute and severe NE outbreaks as challenge bacteria, the disease was not successfully reproduced in the first 4 experiments. In the 5th and 6th experiments, the predisposing conditions were changed and each bird was challenged with 3 ml [3_10[8] CFU/ml] of CP live culture via oral route and also the feed mixed with CP suspension 2 times per day and for 5 consecutive days. Clinical signs and mortalities, and lesions associated with NE were observed in the later two experiments. This study showed that by stressful nutritional and management procedures such as increased stocking density and high levels of wheat and fish meal; induction of relative immunosuppression; using sufficient CP concentration and appropriate ways of its multiplication; and applying challenge bacteria isolated from acute outbreaks, NE may be experimentally induced in broiler chickens