SUMMARY One hundred and ninety E.coli isolates were recovered from broiler chickens 2-6 weeks of age, with respiratory manifistation at Suez Canal area.
Serotyping of 46 isolates demonstrated a predominance of serotypes 0114K-, 078K, 0158K- and O125K70. Other eight serotypes were identified (O119K69, 0126K71, 086K61, OssK60, 028K67, 01K58, 026K60 and 0127K63). The virulence of the 46 identified isolates was confirmed in 2 weeks old chicks, 14 serotypes were highly pathogenic, 21 isolates were intermediate while 11 serotypes were low pathogenic. The in vitro sensitivity testing of 190 isolates using 15 antimicrobials revealed that the majority of the isolates were sensitive to Gentamycine. Enrofloxacin, Danoflaxacin and Norofloxacin. Three types of bacterine were prepared from the most virulent serotype (0125K70) by using formaldhyde, irradiation and sonication. Evaluation of protection were studied in three groups of 2 week old chicks. The preliminary results revealed that prepared bacterins could protect chickens vaccinated at two weeks of age and the degree of protection provided varried with the method of inactivation. Bacterin based on ultrasonic inactivation provided the best protection when compaired with other methods used for inactivation.