Characterization of two Escherichia coli isolates associated with poult enteritis and mortality syndrome

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Abstract
Two colonial types (1 and 2) of Escherichia coli are represented predominantly in cultures isolated from turkey poults with poult enteritis and mortality syndrome (PEMS). Biotype codes determined using two systems (BBL: 36570 and 34560 for colony types 1 and 2, respectively; API-20E: 5144572 and 5144512 for colony types 1 and 2, respectively) clearly establish these organisms as E. coli. These isolates were not clearly divergent from the general profile for E. coli, but colony type 2 differs from colony type 1 with regard to its negative reactions for ornithine decarboxylase and the fermentation of dulcitol, rhamnose, sucrose, and melibiose, suggesting that it is atypical. Colony type 1 is nonserotypable and nonmotile, whereas colony type 2 is serotyped as O136: motile because it has H antigens associated with flagella. Capsular antigens were not found, but thin capsules were seen on cells from both colony types in stained preparations. Cultural morphology was different with colony type 1 having a circular, mucoid, raised morphology and colony type 2 having an irregular, flat, rough morphology. Colony type 1 has a doubling time at 37 C of about 20 min, whereas colony type 2 doubles in 30 min. Furthermore, colony type 1 is a potent colicin producer, but colony type 2 is not a colicin producer. Both E. coli isolates have resistance profiles for multiple antibiotics. Each strain responds to third generation fluoroquinolone antibiotics by changing their biotypes and become resistant after culturing once in their presence. These E. coli are proposed as possible etiological links in the complex series of events that take place in poults susceptible to PEMS.