Prevalence, antimicrobial resistance, and virulence factors of Enterococcus spp. infecting broiler chickens in Egypt

Abstract

Enterococcus spp. are potential pathogens in broiler chickens, causing economic losses in addition to their extensive capacity to acquire and disseminate antimicrobial resistance genes among various bacterial species. This study was conducted to investigate the occurrence of enterococcal infections among broiler chickens in Qena and Sohag Governorates, Egypt, to determine antimicrobial resistance and virulence factors of enterococci isolates, and to screen them for the presence of class 1 and 2 integrons by PCR. Therefore, 120 samples were collected from the diseased broiler chickens aged 1 to 35 days from 30 different commercial farms. The birds were clinically and bacteriologically examined for enterococci, and then antimicrobial susceptibility and virulence factors of enterococci isolates were determined, in addition to their investigation for the presence of some genes by PCR. Enterococci were isolated from 22.5% of the examined birds and were identified as E. faecalis, E. faecium, and E. gallinarum with prevalence of 11.7%, 7.5%, and 3.3%, respectively. The infected birds showed lameness, body weight loss, arthritis, omphalitis, and yolk sac infection in chicks, as well as septicemia and endocarditis in some birds. All enterococci isolates were gelatinase producers, while 18.5% and 81.5% of them were β-haemolytic and biofilm formers with varying grades, respectively. Respective to isolates' antimicrobial susceptibility, 63% of them were multidrug-resistant enterococci with higher occurrence (70.6%) among the class 1 integrons-positive isolates. PCR revealed that 100%, 81.5%, 74.1%, 74.1%, 48.1%, 37.0%, 7.4%, and 3.7% of the isolates carried gelE, aac(6')/aph(2''), ermB, tetM, int1, cylA, vanA, and int2 genes, respectively. This study demonstrated a high prevalence of pathogenic MDR-enterococci among broiler chickens, posing a hazard for poultry health and a potential public health concern. Furthermore, it reported for the first time, to the best of our knowledge, the presence of a high prevalence of class 1 integrons among enterococci in Egypt. Therefore, strict biosecurity protocols and prudent antimicrobial stewardship strategies should be implemented urgently.