Antimicrobial resistance in Salmonella isolated from broiler chicken carcasses

The development of antimicrobial resistance has bee n a public health issue worldwide. The aim of this study was to determine the antibiotic resistance pa ttern of Salmonella species isolated from broiler chickens in Iran. 37 isolates of Salmonella recovered from broiler chicken carcasses were anal yzed for resistance to 14 antimicrobial agents. Salmonella isolates were serogrouped by standard agglutinatio n test using O and H antisera before antibiotic susce ptibility testing. Serogroup screening showed 4 different serogroups (D1, B, C1 and C2) among 37 Salmonella isolates. Salmonella serogroup D1 with frequency 48.64% was the most prevalent serogroup. Antimicrobial susceptibility testing was performed by the standard disc diffusion method acc ording National Committee for Clinical Laboratory Standards. The results showed that Amikacin, Cephal otin, Tylosin,and Chloramphenicol, were the most effective antibiotics (100% sensitivity). Antibioti cs for which Salmonella isolates exhibited resistance were: Neomycin (10.81%), Amoxicillin (18.91%), Stre ptomycin (29.72%), Chlortetracycline (32.43%), Trimethoprim (13.51%), Nalidixic acid (18.91%), Tet racycline (29.72%), Kanamycin (16.21%), Ampicillin (13.51%). Also 51% of resistant isolates belonged t o serogroup D1 and serogroups B, C1, and C2 included 37, 9 and 3% of resistant isolates respect ively. Overall 28% of Salmonella isolates were resistant to more than 4 antibiotics (MDR). Finding s of present study indicated that the development o f antimicrobial resistance in Salmonella is an increasing problem in Iran and resistant stra ins are widespread.


INTRODUCTION
Salmonellosis is an important health problem and a major challenge worldwide.Salmonella spp are recognized as the most causative agents of food poisoning.These organisms are Gram negative and rod shape which have been divided into over 2700 serotypes based on somatic, flagellar and capsular antigens (Gallegos et al., 2008).Salmonella enterica seovar Typhimurium and S. enterica serovar Enteritidis are the most frequent isolated serovars worldwide (Chiu et al., 2010).Foods of poultry origin such as poultry meat and poultry egg have been implicated as important sources of human Salmonella infections (Doyle et al, 2007).Poultry are commonly infected with different Salmonella serovars.Salmonella pullourum and Salmonella gallinarum are two host specific serovars in poultry.Since the antibiotics discovery in the 1940, they have been widely used in both animals and humans.However, many important human and animal pathogens have developed resistance to these compounds (Musgrove et al., 2006, Yismaw et al., 2007).The widespread and indiscriminate use of antibiotic in the treatment of poultry diseases has lead to an increase in the number of resistant Salmonella strains isolated from poultry (Enabulele et al., 2010).In Iran factors such as insufficient control of drug prescription, and widespread use of antibiotics in the treatment and prophylaxis of salmonellosis, promote and favour drug resistance.Therefore the antibacterial resistance in Salmonella is an increasing problem in Iran .The Rplasmid has clinical importance in the acquisition of antibiotic resistance among bacteria.The antibiotic sensitive bacteria may acquire resistance traits from antibiotic resistant strains and thus become resistant to antibiotics (Mandal et al., 2003).Antibiotic resistant organisms lead to increase health costs and mortality and have therefore become an important health concern due to serious consequences of the treatment of disease.In  (Zahraei et al, 2005;Pokharel et al., 2009;Wei et al., 2011;Mohanty et al., 2006;Murugkar et al., 2005;Selvaraj et al., 2010).Knowledge of the epidemiology of Salmonella antibiotic resistance and understanding their risk factors for infection are necessary for control of drug resistance in both animals and humans.The objective of the present study was antibiogram of different Salmonella strains isolated from broiler chickens in poultry farms in Ardebil province, Iran.

Serogroup screening
37 Salmonella strains which were isolated from broiler poultry farms in Ardebil province, Iran were serogrouped in this study.Serogroup screening of isolates was performed by standard agglutination test using O and H antisera (Difco, USA) as described by Quinn et al. (1994).

RESULTS
Based  et al., 2010;Madadgar et al., 2008;Akbarmehr, 2010).It must be considered that the prevalent Salmonella serovars are different between chickens and associated with chicken lines and geographic area.Factors influencing the prevalence of chicken-associated Salmonella are feeds and growth environment, transportation process, and chicken sources (Chiu et al., 2010).Antibiotc susceptibility of 37 Salmonella isolates was performed by 14 different antimicrobial agents.As Table 2 shows Salmonella isolates were most sensitive towards Amikacin, Cephalotin, Although it must be considered that the incidence of resistant, susceptible and intermediately resistant isolates differed from procedure to procedure following the performance of disc diffusion assay (Cotter et al. 2001).
In Iran the use of antimicrobial drugs are not well controlled.Thus most of microbial resistance may be due to widespread use of antibiotics in treatment of animal disease.Many reports support the hypothesis that the presence of plasmids together with the usage of antimicrobial agents in human medicine and veterinary may largely contributed to the spread of antibiotic resistance (Carattoli, 2003).Findings of present study indicated that the development of antimicrobial resistance in Salmonella is an increasing problem in Iran and resistant strains are widespread.Hence antimicrobial susceptibility test must be performed before using antibiotics in the treatment or prophylaxis of disease.

Table 1 .
The results of serogroup screening of Salmonella isolated from broiler chicken carcasses in Ardebil province, Iran.
on serological tests which carrid out by Salmonella
Pokharel et al. (2009)s the most prevalent serotype and demonstrated the greatest multiple resistance.Pokharel et al. (2009)in a study which was carried out in Nepal reported that S. paratyphi was most sensitive towards Amikacin and Ciprofloxacin which agree with our results.