Phenotypic, Molecular Detection, and Antibiogram Patterns of E. coli isolates from Respiratory Infections of Commercial Layers in and around Tirupati

Author: Nagendra Reddy Thopireddy and Surendranath Reddy Somanagari

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Abstract

A total of 78 pooled oral swabs, 82 pooled tracheal swabs, 86 pooled nasal swabs, and 25 pooled infraorbital sinus exudates were collected from the ailing birds, which were showing respiratory signs and were labeled farm-wise and specimen-wise. The PCR test was standardized to target the 16s rRNA gene, and the study found that 8 of 12 farms tested positive for E. coli infection. Among the 8 positive farms, 59 out of 78 (75.64% oral swabs), 72 out of 82 (87.80% tracheal swabs), 70 out of 86 (81.39% nasal swabs), and 18 out of 25 (72% infraorbital sinus exudates) were confirmed positive by PCR, with a predicted size of 585 bp for all positives. From the pooled samples, 32 samples (1 from oral swabs, 1 from tracheal swabs, 1 from nasal swabs, and 1 from infraorbital sinus exudate from each of the 8 positive farms) had been evaluated for antimicrobial susceptibility patterns using the Kirby-Bauer disc diffusion method. These 32 clinical E. coli isolates were isolated on selective EMB agar and MacConkey agar, which produced greenish metallic sheen and pink colonies, respectively. Gram staining confirmed these colonies, which had an IMViC pattern of ++--. The Kirby-Bauer disc diffusion method was used to test the antimicrobial patterns of pure clinical respiratory isolates of E. coli. All isolates were resistant to Ceftriaxone (CTR) and Cephalexin (CN), but sensitive to Enrofloxacin (EX), Tetracycline (TE), Ciprofloxacin (CIP), Co-trimaxazole (COT), and Colistin (CL). The gold standard test for confirmation of E. coli is isolation and identification of E. coli on EMB agar, which appear as greenish metallic sheen colonies, but the process is laborious and time-consuming. Similar results were obtained with molecular techniques like PCR, a confirmatory test with accurate results but less time-consuming. This study concluded that the prompt detection of respiratory diseases in poultry is accurate using molecular approaches, which will aid in the isolation of E. coli, antibiogram patterns, and the implementation of control measures that will guide the selection of suitable drugs for treatment

Keywords

layers, E. coli, EMB agar, PCR, antibiogram

Conclusion

E. coli is the most frequent bacterial infection in poultry, causing significant economic losses globally. Controlling E. coli improves both animal and human health. Present study found that E. coli isolates from layers in and around Tirupati are resistant to at least one of the antimicrobial agents tested. Given the serious antimicrobial resistance (AMR) conditions, there's a pressing need to curtail antibiotic use, especially in layer farms. The emergence of significant antibiotic resistance and the high risk of transmitting resistant bacteria and genes to humans necessitate the development of new antibacterials for exclusive use in animals, without cross-resistance to existing antibiotics. This could be a viable solution for the future. It's crucial to enhance awareness and conduct scientific research through monitoring and surveillance programs on AMR to mitigate the adverse impacts of antimicrobial-resistant E. coli in the poultry industry

References

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How to cite this article

Nagendra Reddy Thopireddy and Surendranath Reddy Somanagari (2024). Phenotypic, Molecular Detection, and Antibiogram Patterns of E. coli isolates from Respiratory Infections of Commercial Layers in and around Tirupati. Biological Forum – An International Journal, 16(10): 48-54