Escherichia coli strains as Major secondary bacterial pathogen isolated from an outbreak of swollen head syndrome in layers, in Al-Diwaniyah, Iraq

A cross-sectional study was conducted to identify the involvement of E. coli as secondary pathogen in cases of Swollen Head infection and to detect drug susceptibility pattern of these isolates. This study was carried out on 20 chickens that were purchased from Al-Safaa Company from an outbreak of a sudden increase in mortality in layers farm and experienced clinical signs included difficult breath, coughing, rales, swollen of infraorbital and supraorbital sinuses, and conjunctivitis, as well as severe depression. The main gross lesions demonstrated among the infected chicken including gaseous exudate in trachea, nasal passages and sinuses. There was yellowish gaseous exudate on the air sacs, ovaries and the peritoneum. The samples were inoculated on different bacteriological culture media, the isolates were identified by morphological, and biochemical tests, in which the result revealed that the major pathogens associated with swollen head syndrome in layers was E.coli. The majority of isolates were resistant to ciprofloxacin (94.4%), Ampicillin (100%), Erythromycin (100%), azithromycin (100%), trimethoprim (88.9%), and levofloxacin (94.4%). Nonetheless, however majority of APEC isolates were susceptible to nitrofurantoin (72.3%). Moreover, all E.coli strains recovered in the current study showed multidrug resistant to three or more different antibacterial classes. In conclusion, the present findings showed that MDR E. coli is prevalent SHS. The MDR E. coli is alarming signal because these bacteria can transfer their MDR trait to potential human and animal pathogens. Therefore, the introduction of surveillance programs to monitor antimicrobial resistance strains is strongly recommended to protect human and animal health.