Serotype Distribution and Antimicrobial Resistance of Salmonella Isolates in Human, Chicken, and Cattle in Iran

Document Type : Original Articles


1 Department of Microbiology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

2 Department of Food Hygiene, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran


Salmonellais a foodborne zoonotic enteric bacterium able to infect both humans and animals. This study aimed to identify the antimicrobial resistance of Salmonella serovars isolated from human, cattle, and poultry. Moreover, we investigated the probable transmission trends of antibiotic-resistant Salmonella isolates from food animals to human. A total of 242 Salmonella isolates collected from various human and animal sources were serotyped. The polymerase chain reaction was performed to detect the invA virulence gene. The isolates were subsequently tested against 14 antimicrobials and the resistance rates among the isolates from three sample sources were statistically analyzed by the Chi-Square test. Serotyping revealed the isolates belonged to various serovars with the dominance of Enteritidis (37%), Typhimurium (35.3%), and Infantis (21.1%). A high frequency of resistance to streptomycin was observed followed by tetracycline, trimethoprim, sulfonamides, spectinomycin, chloramphenicol, florfenicol, ampicillin, kanamycin, ceftazidime, and cefepime. In addition, multidrug resistance was observed in more than 40% of the isolates. The results of the statistical analysis showed a significant relationship (P ˂ 0.001) between the rate of antibiotic resistance among the three sources of Salmonellaisolates. Furthermore, the antibiotic resistance had a statistical relationship between the different serotypes isolated from different sources. These findings demonstrate the possible transmission of resistance to human from animal sources. The prevalence of the Typhimurium, Enteritidis, and Infantis serovars in both human and animals suggested that Salmonella contamination in chicken and cattle may be the major source of salmonellosis in human. The high incidence of antibiotic resistance in Salmonellaisolates along with the close relationship between the antimicrobial resistance of animal and human isolates indicate the role of food animal products as an important source of resistance.


Main Subjects

Article Title [French]

La distribution des Sérotypes et la Résistance aux Antimicrobiens D'isolats de Salmonella chez L'homme, le Poulet et le Bétail en Iran

Abstract [French]

Salmonella est une bactérie entérique zoonotique d'origine alimentaire capable d'infecter aussi bien les les humains que les animaux. Cette étude visait à identifier la résistance aux antimicrobiens des différents sérovars de Salmonella isolés chez l'homme, le bétail et la volaille. De plus, nous avons étudié les tendances probables de transmission d'isolats résistants aux antibiotiques chez des animaux destinés à l'alimentation humaine. Un total de 242 isolats de Salmonella provenant de diverses sources humaines et animales ont été sérotypées. Une réaction en chaîne de la polymérase a été réalisée pour détecter le gène de virulence invA. Les isolats ont ensuite été testés contre 14 antimicrobiens et les taux de résistance parmi les isolats de trois échantillons ont été analysés de manière statistique par le test du chi carré. Le sérotypage a révélé que les isolats appartenaient à divers sérovars avec une dominance d’Enteritidis (37%), Typhimurium (35,3%) et Infantis (21,1%). Une fréquence élevée de résistance à la streptomycine a été observée, suivie de la tétracycline, du triméthoprime, des sulfamides, de la spectinomycine, du chloramphénicol, du florfénicol, de l'ampicilline, de lakanamycine, du ceftazidime et du céfépime. De plus, une multirésistance aux médicaments a été observée dans plus de 40% des isolats. Les résultats de l'analyse statistique ont montré une relation significative (P˂0,001) entre le taux de résistance aux antibiotiques parmi les trois sources d'isolats de Salmonella. En outre, la résistance aux antibiotiques présentait une relation statistique entre les différents sérotypes isolés de différentes sources. Ces résultats démontrent la transmission possible de la résistance aux antibiotiques à l'homme par des sources animales. La prévalence des sérovars Typhimurium, Enteritidis et Infantis chez l'homme et les animaux suggère que la contamination par Salmonella chez le poulet et le bétail peut être la principale source de salmonellose chez l'homme. L'incidence élevée de la résistance aux antibiotiques dans les isolats de Salmonella ainsi que la relation étroite existant entre la résistance aux antimicrobiens des isolats animaux et humains indiquent que les produits des animaux destinés à l'alimentation sont une source importante de résistance.

Keywords [French]

  • Animaux
  • résistance aux antibiotiques
  • Humain
  • Salmonella
  • Sérotype
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