1 EFFICACY OF PEFLOXACIN FOR THE TREATMENT OF BROILER CHICKENS EXPERIMENTALLY INFECTED WITH ESCHERICHIA COLI O 78 : K 80

This study was conducted to assess the efficacy of pefloxacin in controlling the adverse effects of experimentally induced colibacillosis in broiler chickens. Twohundreds and thirty, one-day old broiler chicks were used and randomly allocated into four experimental groups; group (1) uninfected-untreated, group (2) infected-untreated, group (3) infected-treated with pefloxacin in the drinking water and group (4) infected-treated with pefloxacin by intramuscular injection (I/M) injection. The drug was given at dose level of 10 mg/kg b.wt/day for 3 consecutive days. Experimental colibacillosis was induced at 21-day of age by I/M inoculation of Escherichia coli (E.coli) serotype O78: K80. Clinical signs, mortalities, mean lesion scores, performance including body weight and feed conversion efficiency, frequency of E.coli re-isolation and histopathological alterations were recorded and evaluated. Also, clinical chemistry parameters including serum levels of total bilirubin and liver enzymes (liver function parameters) as well as uric acid, blood urea nitrogen and creatinin (kidney function parameters) were estimated. The humoral immune response to sheep red blood cells (SRBC) and serum protein electrophoresis were measured. The pharmacokinetic of pefloxacin were investigated. The Results showed that infectedpefloxacin treated chickens had less pronounced clinical signs, significant (P<0.05) lower mortalities, lower average gross pathology scores, higher body weight and better feed conversion than infected-untreated birds. Serum levels of total bilirubin and liver enzymes as well as uric acid, blood urea nitrogen and creatinin were significantly (P<0.05) decreased toward normal values in chickens of infected-pefloxacin treated groups when compared with those in infected-untreated group. The haemagglutinating antibody titers to SRBC and serum levels of gammaglobulins (albumin/globulin ratios) were significantly (P<0.05) increased in the treated groups than untreated ones. The results of pefloxacin pharmacokinetics cleared that higher drug serum concentration was recorded following I/M injection than after oral dosing. The absorption half life time (t1/2ab) was 0.53±0.08 and 0.21±0.026 h following oral and I/M administration, respectively. The maximum serum concentration (Cmax) recorded after oral dosing (2.71±0.14 μg.ml -1 ) and (1.68±1.15 μg.ml -1 ) following I/M injection. The tissues residues results revealed that pefloxacin was not detected on the 9 th day following cessation of water medication; however, the drug was still detected in the liver, kidney and skin of I/M injected birds. The results of pefloxacin pharmacokinetic and serum drug concentrations cleared that pefloxacin have good absorption with high bioavailability, long half-life time and excellent tissue and body fluid penetration. In the present study, although there were no convincing differences in clearing the clinical or pathological features of E.coli between the two methods of pefloxacin administration, but I/M route was more efficacious than drinking water method because of its ability to completely eliminate E.coli from its site of action and so it may could minimize the risk of disease reoccurring. In conclusion, pefloxacin administration (regardless to the method) at 10 mg/kg b.wt /day for 3 consecutive days is efficacious for the treatment of colibacillosis in broiler chickens evident by improvement of all investigated parameters and good pharmacokinetic profile .