Antisera against somatic o antigens

E. coli was recovered and identified as depicted [1 ]. Concisely, samples were inoculated into buffer peptone water and incubated aerobically for 24 h at 37 °C. Each incubated sample was streaked onto MacConkey agar (Oxoid, Manchester, UK) and eosin methylene blue agar (Lioflichem, Roseto degli Abruzzi, Italy) plates and incubated for 24 h at 37 °C. On MacConkey agar, the suspected colonies were 1–2 mm in diameter and had a hot-pink color, whereas on eosin methylene blue agar, they had a metallic color and sheen.
Suspected pure E. coli colonies were collected and subjected to further classical biochemical screening (oxidase test, citrate utilization, indole test, methyl red, Voges Proskauer and Triple Sugar Iron “TSI”) as well as using the API 20E system (BioMérieux, Craponne, France) following the manufacturer’s guidelines. Furthermore, antisera against somatic (O) antigens (DENKA SEIKEN Co., Tokyo, Japan) were used for serotyping isolated E. coli following the kit instructions.

Escherichia coli was isolated and identified according to Nolan et al. [1 ]. Briefly, all the collected samples were pre-enriched in buffered peptone water (Lab M, UK) and incubated aerobically at 37°C for 24 h. A loopful of the broth culture was inoculated onto MacConkey agar (Neogen, US) and eosin methylene blue agar (Lab M) plates, which were incubated at 37°C for 24 h. The isolated colonies were identified morphologically and biochemically (oxidase strips and triple sugar iron agar were from Oxoid, UK; urea, Simmons’ citrate agar, and peptone water were from Lab M; and Kovacs reagent was from HiMedia, India) [1 ]. In addition, antisera against somatic (O) antigens (Denka Seiken Co., Tokyo, Japan) were used for serotyping isolated E. coli following the manufacturer’s instructions.