Characteristics of Escherichia coli Isolates from Avian Cellulitis

The purpose of this study was to characterize Escherichia coli isolates from avian cellulitis, particularly with respect to the occurrence of potential virulence factors. At slaughter, five broilers with lesions of cellulitis were selected from each of 20 farms from among the broilers processed. One hundred E. coli isolates from the lesions were characterized with respect to serotype; biotype; drug susceptibility; plasmid profile; ability to produce aerobactin, colicin, colicin V, and hemolysin; and cytotoxicity for Vero cells and chicken fibroblasts. The same properties were determined from a collection of 25 E. coli from the feces of chickens. Serotyping showed that, among the cellulitis isolates, 23 belonged to O group 78, 14 belonged to O2, eight belonged to O115, and seven belonged to O(21,83); 25 were untypable. Isolates from a single farm typically belonged to three to five O groups. More than half of the fecal isolates were untypable, and the rest were distributed among seven O groups. Biotype, drug-resistance pattern, and plasmid profile could not be used as markers of avian cellulitis E. coli. No plasmid was detected in 12% of cellulitis isolates and 48% of fecal isolates. No isolate was hemolytic or showed cytotoxic effects. Aerobactin was produced by 90% of cellulitis isolates, and colicin was produced by 85% of these isolates; the corresponding percentages for the fecal isolates were 16% and 40%. Production of colicin V was detected in 21% of cellulitis isolates and 24% of fecal isolates. The major conclusions were that E. coli from avian cellulitis were predominantly of the same O groups (O78, O2) as those associated with respiratory and septicemic diseases in poultry and usually produced aerobactin and colicin. /// El objetivo de este trabajo fue caracterizar cepas de Escherichia coli aisladas de celulitis aviar particularmente con respecto a la ocurrencia de factores potenciales de virulencia. En el matadero se seleccionaron cinco pollos de engorde con lesiones de celulitis entre los pollos procesados de cada una de 20 granjas. Cien cepas de E. coli aisladas de las lesiones se caracterizaron con respecto a serotipo, biotipo, susceptibilidad a drogas, perfil de plásmidos, capacidad de producir aerobactina, colicina, colicina V y hemolisina; y toxicidad para células VERO y para fibroblastos de pollo. Se determinaron las mismas propiedades a partir de 25 cepas de E. coli aisladas de las heces de pollos. La serotipificación mostró que entre las