Characterization of E. coli and Salmonella spp. isolates associated with omphalitis in baby chicks

Omphalitis is a major cause of increased first week-chick mortality. Omphalitis, navel-yolk sac infection, is a hatchery-born disease, and also known as ‘mushy chick disease’ or ‘navel ill’. It is a common disease of chicks and poults, often artificially hatched chicks, causing high losses in the brooding period, as a bacterium penetrates the porous egg shell. As incubation conditions are suitable for bacterial growth and incubating eggs as well, various bacteria, such as E. coli, staphylococci, Proteus, Clostridium fecali and Pseudomonas may be involved in the yolk sac infection. The present study aimed to determine bacterial causes of omphalitis through isolation and identification of such pathogens. Therefore, samples from 216 yolk sacs were collected from chicks with unabsorbed yolk materials that could even smell putrid. Among those, 196 (90.7%) were positive; 135 (62.5%) harboured single bacterial strains and 61 (28.2%) had mixed infections. The most prevalent single bacterial isolates were E. coli (110 isolates) and P. aeruginosa (11 isolates). Meanwhile, the most predominant mixed bacterial strains were E. coli with Salmonella spp. (16 isolates; 7.4%) and E. coli with P. aeruginosa (13 isolates; 6%). Other mixed infections were found in low percentages. Most E. coli strains were Congo red-positive and non-haemolytic. Different E. coli serogroups were serologically identified including O27 (4 isolates; 20%), O157 (3isolates; 15%), O26 (3 isolates; 15%) and one isolate of each of the following; O78, O6, O125, O44, O15, O115, O25, O168, O112 and O63 (each of 5%). Different Salmonella serogroups were identified including S. cremieu (2 isolates) and one isolate of each of the following S.enteritidis, S. blegdam, S. senftenberg, S. kingston and S. emek.