Antibiotic Resistance in Poultry Industry: Poultry Microbes and AMR - Glamac

Antibiotic Resistance in Poultry Industry: Poultry Microbes and AMR

connection between poultry and antibiotic resistance


Antibiotics and Poultry industry

The use of antibiotics in the poultry industry began in the mid-20th century, around the 1940s and 1950s. Initially, antibiotics were primarily used to treat specific bacterial infections in poultry birds. Increased demand for poultry meat and eggs lead to the antimicrobial use in poultry feed as AGPs and became vital in large scale poultry production for disease prevention and growth promoting effect. Also, in many countries’ antimicrobials are seen as the substitutes for the biosecurity and hygiene at the farms.

In our previous blog series we have talked about the history and background of antibiotic resistance in the poultry industry and antibiotic resistance mechanism in the poultry industry. In this blog we will deep dive in poultry microbes and AMR.

As per GCRF study, the globe produces more than 100 million tonnes of chicken meat and more than 1.3 trillion hen eggs every year. Between 2017 and 2050, it is predicted that chicken production would increase by 48% worldwide, with more than 70% of that expansion projected to come from Asian nations. Consumption of animal protein is skyrocketing in the region due to factors such as urbanisation, population expansion, and rising income. High-intensity farming is a great fit for hens. On the other hand, there are significant threats to public health on a local, regional, and worldwide scale when chicken production increases quickly. One of the most important of these is the emergence of antimicrobial resistance (AMR) brought on by the frequently unregulated use of antibiotics in farming.

Regulations regarding usage of antimicrobial drugs are vary from country to country i.e. EU banned use of antibiotics in animal feed on other hand AGPs remained authorised in countries like Japan. Also, AGPs are widely being used in leading poultry producing countries like China, India, Brazil, Indonesia etc.

Micro-organisms and resistance

Escherichia coli

Escherichia coli, often shortened to E. coli, are a type of bacteria that belongs to the Gram-negative group. It is considered a facultative anaerobe, meaning it can survive with or without oxygen. This bacterium is a member of the Enterobacteriaceae family.

E. coli is commonly found in the gastrointestinal tract of warm-blooded animals, including humans and animals like poultry. Because of its widespread presence, it is often used as an indicator to monitor antibiotic resistance in food animals, such as poultry.

Additionally, some strains of E. coli found in poultry can carry genes that make them resistant to antibiotics. These antibiotic resistance genes have the potential to transfer from bacteria in poultry to bacteria that can cause infections in humans. This transmission of antibiotic resistance genes from animals to humans is a concern because it can lead to difficulties in treating bacterial infections in humans with antibiotics.

Antibiotic Resistance Genes

E.coli is reported to have antibiotic resistance genes, such as genes encoding resistance to beta-lactams (blaTEM, blaCTX-M-1, blaCTX-M-2, blaCTX-M-9, blaOXA-1, blaOXA-47, blaSHV, and CITM), tetracyclines (tetA, tetB,and tetC), sulfonamides (sulI and sulII), fluoroquinolones (qnrB and qnrS), colistin (mcr1 and mcr3), aminoglycosides (rmtB), streptomycin (aadA1), gentamicin (aac-3-IV), erythromycin (ereA), trimethoprim (dfrA1), and chloramphenicol (catA1 and cmlA)

Certain strains of Escherichia coli, known as “avian pathogenic E. coli” or APEC, are responsible for causing a disease called colibacillosis in poultry. Colibacillosis is a significant health issue for poultry farms globally, as it leads to illness and death among the birds.

APEC strains of E. coli have specific characteristics that allow them to cause disease in poultry. They can infect various parts of the bird’s body, including the respiratory system, urinary tract, and internal organs, leading to a range of symptoms such as respiratory distress, swollen joints, and decreased egg production.

Colibacillosis poses a considerable economic burden to poultry farmers due to losses from decreased productivity, increased mortality rates, and the costs associated with treatment and prevention measures. Therefore, controlling and preventing colibacillosis in poultry is essential for maintaining the health and welfare of poultry flocks and ensuring the sustainability of poultry production systems.

Phenotypic resistance

AMP (82.0% R; 18.0% I), AMX (86.0% R; 14.0% I), AMC (28.0% R; 14.0% I), CLX (72.0% R; 28.0% I), CN (24.0% R; 12.0% I), KA (28.0% R; 10.0% I), NEO (62.0% R; 28.0% I), ERY (80.0%; 20.0%), LCM (94.0% R; 6.0% I), LIP (30.0% R; 42.0% I), TIA (100% R), TIM (100% R), TYL (100% R), TE (32.0% R; 26.0% I), OTC (50.0% R; 8.0% I), DOX (30.0% R; 18.0% I), SXT (34.0% R; 6.0% I), ENR (24.0% R; 6.0% I), NOR (20.0% R; 10.0% I), COL (24.0% R; 10.0% I), FOM (8.0% R; 8.0% I)(Nhung et. al., 2017).

S. Pullorum/Gallinarum

Salmonella Pullorum and Salmonella Gallinarum are Gram Negative types of bacteria belonging to the genus S. enterica subspecies enterica, in the Enterobacteriaceae family. They cause two diseases in poultry: pullorum disease and fowl typhoid. These diseases are widespread in many parts of the world but have been eliminated from commercial poultry farms in many developed countries.

Through billions of years of evolution, Salmonella has accumulated many metabolic and protective mechanisms that can be mobilized in response to different external aggressions, including antibiotics.

Antibiotic Resistance Genes

tetA and tetB genes are predominantly found in the DNA of most isolates indicating its resistance to tetracyclines.

Phenotypic resistance

AMP (8.3% R; 33.4% I), AMC (0% R; 8.3% I), CLX (0% R; 41.7% I), CN (0% R; 8.3% I), KA (0% R; 66.7% I), NEO (0% R; 58.3% I), TE (16.7% R; 83.3% I), ERY (100% R), C (0% R; 33.4% I), SXT (0% R; 33.4% I), NA (75.2% R; 33.4% I), ENR (0% R; 25.0% I), CIP (0% R; 16.7% I), OFL (0% R; 25.0% I), COL (0% R; 16.7% I).

Pasteurella multocida

Pasteurella multocida is a Gram-negative bacterium of the Pasteurellaceae family, causing fowl cholera in birds. It leads to acute fatal septicemia in adult birds, but chronic and asymptomatic infections can also occur.

Phenotypic resistance

PEN (49.6% R; 43.9% I), AMP (23.6% R; 22.8% I), CAB (59.3% R; 26.0% I), CN (23.6% R; 20.3% I), S (32.5% R; 44.7% I), AK (55.5% R; 19.5% I), C (6.5% R; 19.5% I), ERY (50.4% R; 49.6% I), LCM (2.4% R; 35.8% I), TE (24.4% R; 43.1% I), OTC (8.1% R; 30.1% I), DOX (25.2% R; 17.9% I), SDZ (100% R), TMP (39.0% R; 9.8% I), SXT (31.7% R; 13.8% I), CIP (8.9% R, 40.6% I), ENR (8.1% R; 20.3% I), NOR (8.1% R; 30.1% I), RIF (44.5% R; 25.2%), NIT (34.1% R; 26.0% I) (Nhung et. al., 2017).

Avibacterium paragallinarum

Avibacterium paragallinarum (formerly known as Haemophilus paragallinarum) is a capsulated, rod-shaped bacterium belonging to the Pasteurellaceae family. It is Gram-negative and can survive with or without oxygen, making it a facultative anaerobe. Avibacterium paragallinarum is responsible for causing infectious coryza, an acute disease affecting the upper respiratory tract of chickens worldwide.

Phenotypic resistance

AMP (100% R), AMC (0%), NEO (100% I), S (100% I), C (0%), TE (100% R), OTC (100% R), DOX (100% R), SXT (0%), FUR (100% I), ENR (0%), CIP (0%), PEF (0%)

Clostridium perfringens

Clostridium perfringens is a Gram-positive bacterium that takes on a rod-like shape and thrives in anaerobic conditions, capable of forming spores. It’s commonly present in the intestinal tract of poultry, other animals, and the environment. When conditions are favorable, this bacterium can rapidly multiply, leading to necrotic enteritis and cholangiohepatitis. These diseases result in significant losses in the broiler and turkey industry globally.

tetP(B), tet(M), tetA(P), and tetB(P) genes among tetracycline resistant isolates.

Phenotypic resistance

PEN (0% R), LCM (3.6% R; 7.3% I), TE (41.8% R; 18.2% I), BAC (49.1% R; 43.6% I), NAR (0% R), MON (0%), AVI (0% R).

Mycoplasma spp.

Mycoplasma species are a type of bacteria known as Mollicutes, characterized by their lack of a cell wall around their membrane. Among these, M. gallisepticum (MG) is especially notable for causing respiratory disease and reducing meat and egg production in chickens and turkeys worldwide. Additionally, other species like M. synoviae (MS), M. meleagridis, and M. iowae can also induce disease in poultry.

Antimicrobials commonly used to treat Mycoplasma spp. infections include tetracyclines, macrolides (tylosin, tilmicosin), and more recently, fluoroquinolones (enrofloxacin, difloxacin), and pleuromutilins (tiamulin).


The emergence of resistant strains of bacteria such as Escherichia coli, Salmonella spp., Pasteurella multocida, Avibacterium paragallinarum, Cl\ostridium perfringens, and Mycoplasma spp. has led to the need for stricter regulation and oversight of antimicrobial use in poultry farming. This is a wake-up call for all the countries dependent upon usage of antimicrobials in poultry farming. It is important to adopt and enforce policies that restrict the use of critical antimicrobials and promote alternative strategies for disease prevention and control. A multidisciplinary One Health approach involving veterinarians, farmers, regulatory bodies, and public health officials is essential for managing and mitigating the risks associated with AMR.