Necrotic Enteritis and Antimicrobial Resistance: Implications for Poultry and Food Safety

When a broiler flock develops necrotic enteritis (NE), antimicrobial treatment may appear to be the quickest route to disease control. But repeated or extensive antimicrobial exposure can leave another problem behind: Clostridium perfringens populations with resistance to commonly used drugs. 

For the poultry veterinarian, this makes antimicrobial resistance more than a laboratory finding. It can influence treatment choices, disease control and the wider food-safety consequences of C. perfringens in poultry production. 

Resistance can complicate NE management 

Clostridium perfringens normally inhabits the gastrointestinal tract, but antimicrobial exposure can select for resistant populations and contribute to the accumulation of resistance genes^[1],[2]. 

The resistance pattern can involve drugs used against C. perfringens. Bacitracin resistance was reported in 47.3% of isolates, while 41.8% were resistant to tetracycline. Another group of isolates showed resistance to gentamicin in 44%, bacitracin in 40% and tetracycline in 40%, with many isolates showing multidrug resistance^[2],[3]. 

These numbers should not be treated as a resistance rate for every poultry flock. They demonstrate why susceptibility cannot simply be assumed from previous treatment experience. 

Resistance is not always limited to one drug^[2] 

The problem becomes more important when resistance determinants can move between bacteria. Resistance plasmids in C. perfringens can be transferred by conjugation, creating opportunities for resistance traits to spread within bacterial populations^[4]. 

Tetracycline resistance is linked to plasmids such as pCW3, while pIP401 carries resistance to chloramphenicol and tetracycline. Bacitracin resistance in C. perfringens has been linked to the conjugative plasmid pJIR4150, with resistance mediated through active efflux. Lincomycin resistance can involve the lnu gene family. 

For the veterinarian, the practical concern is straightforward: Exposure to one antimicrobial does not necessarily produce resistance to only that antimicrobial. Multidrug resistance can narrow the options available when NE requires treatment. 

Do not assume susceptibility 

Several antimicrobials, including penicillin, metronidazole, meropenem, cefoxitin and piperacillin-tazobactam, have shown activity against C. perfringens^[2]. However, susceptibility can vary between bacterial populations. 

That makes antimicrobial selection a clinical decision rather than a routine choice based solely on what has worked previously. Where laboratory susceptibility information is available, it can provide useful support for selecting an appropriate antimicrobial. 

The emergence of optrA in chicken-derived C. perfringens isolates also illustrates how resistance mechanisms can continue to emerge. The presence of toxin genes such as netB, cpb2 and tpeL has additionally been linked with antimicrobial resistance profiles^[5]. 

The concern extends beyond the flock^[2] 

Antimicrobial resistance is also relevant because C. perfringens has food-safety significance. Type A and type C strains can cause disease in humans, and some type A strains produce C. perfringens enterotoxin during sporulation. 

The organism has been recovered from more than 81% of chilled carcasses. This does not mean that every contaminated carcass will cause human disease, but it highlights why control of C. perfringens remains relevant beyond the poultry house. 

Food handling can provide another opportunity for multiplication. C. perfringens spores can survive cooking and subsequently germinate during cooling and storage of cooked food. With a doubling time of less than 10 minutes under favourable conditions, bacterial numbers can increase rapidly. 

What does this mean for the poultry veterinarian?^[1] 

When NE is suspected, antimicrobial use should sit within a broader control plan: 

• Confirm that the clinical and intestinal picture is consistent with NE. 
• Consider antimicrobial susceptibility information where available. 
• Avoid assuming that previous treatment success guarantees current susceptibility. 
• Recognise that resistant C. perfringens can carry multiple resistance determinants. 
• Address the flock-level factors that predispose to NE rather than relying solely on antimicrobial treatment. 
• Keep the food-chain implications of C. perfringens in view. 

Clinical Bottom Line 

Antimicrobial resistance changes the way NE should be managed. Resistance to bacitracin, tetracycline and other antimicrobials, together with transferable resistance determinants, can complicate treatment and contribute to a broader resistance reservoir. 

For poultry veterinarians, the priority is therefore accurate diagnosis, rational antimicrobial selection and stronger prevention of the conditions that allow NE to develop. This approach supports disease control at flock level while also limiting unnecessary antimicrobial pressure and its potential consequences for food safety.

References:

1. Mwangi S, Timmons J, Fitz-Coy S, Parveen S. Characterization of Clostridium perfringens recovered from broiler chicken affected by necrotic enteritis. Poultry Science. 2019 Jan 1;98(1):128-35. https://www.sciencedirect.com/science/article/pii/S0032579119302949
2. Fathima S, Hakeem WG, Shanmugasundaram R, Selvaraj RK. Necrotic enteritis in broiler chickens: a review on the pathogen, pathogenesis, and prevention. Microorganisms. 2022 Sep 30;10(10):1958. https://www.mdpi.com/2076-2607/10/10/1958
3. Anju K, Karthik K, Divya V, Priyadharshini ML, Sharma RK, Manoharan S. Toxinotyping and molecular characterization of antimicrobial resistance in Clostridium perfringens isolated from different sources of livestock and poultry. Anaerobe. 2021 Feb 1;67:102298. https://www.academia.edu/download/95065427/j.anaerobe.2020.10229820221130-1-1e36ztp.pdf
4. Lyras D, Adams V, Ballard SA, Teng WL, Howarth PM, Crellin PK, Bannam TL, Songer JG, Rood JI. tIS Cpe8, an IS 1595-family lincomycin resistance element located on a conjugative plasmid in Clostridium perfringens. Journal of bacteriology. 2009 Oct 15;191(20):6345-51. https://journals.asm.org/doi/pdf/10.1128/jb.00668-09
5. Wei B, Cha SY, Zhang JF, Shang K, Park HC, Kang J, Lee KJ, Kang M, Jang HK. Antimicrobial susceptibility and association with toxin determinants in Clostridium perfringens isolates from chickens. Microorganisms. 2020 Nov 19;8(11):1825. https://www.mdpi.com/2076-2607/8/11/1825