Serotype, antimicrobial susceptibility and genotype profiles of Salmonella isolated from duck farms and a slaughterhouse in Shandong province, China

BACKGROUND

Salmonella has been considered as one of the most important foodborne pathogens that threatened breeding industry and public health. To investigate the prevalence and characterization of Salmonella isolated from duck farms and a slaughterhouse in Shandong province, a total of 49 Salmonella strains were isolated from 2342 samples from four duck farms and one duck slaughterhouse in Jinan and Tai'an, Shandong province, China.

RESULTS

Among the isolates, S. Enteritidis (20/49, 40.8%) and S. Anatum (10/49, 20.4%) were the most prevalent, and high resistance rates were detected for erythromycin (49/49, 100.0%) and nalidixic acid (47/49, 95.9%). Class I integrons were detected in 17 isolates (34.7%17/49), which contained gene cassettes aadA7 + aac3-Id(15/17) and aadA5 + dfrA17 (2/17). Eleven different kinds of resistance genes were detected while blaTEM(36/49, 73.5%) was the most prevalent, followed by sul2(14/49, 28.6%). Thirteen virulence genes were tested, and all of the strains carried invA, hilA and sipA. Multilocus sequence typing (MLST) results showed that seven sequence types (STs) were identified; ST11 was the most prevalent ST (20/49, 40.8%), followed by ST2441 (10/49, 20.4%). There was a strong correlation between STs and serovars. The results of pulsed field gel electrophoresis(PFGE) showed that 39 PFGE patterns were generated from 49 Salmonella strains. PFGE patterns were mostly diverse and revealed high similarity between the isolates from the same sampling sites.

CONCLUSIONS

The presence of Salmonella infections among duck farms revealed that ducks could also be potential reservoirs for Salmonella. The high resistance rates against commonly used antimicrobials suggested a need for more reasonable use of antimicrobials, as well as for investigating substitutes for antimicrobials.

Non-Typhoidal Salmonella in poultry meat and diarrhoeic patients: prevalence, antibiogram, virulotyping, molecular detection and sequencing of class I integrons in multidrug resistant strains

Background

The worldwide increase of food-borne infections with antibiotic resistant pathogens constitutes a major public health problem. Therefore, this study aimed to determine the prevalence, antibiogram, virulence genes profiles and integron characteristics of non-typhoidal Salmonella spp. isolated from poultry meat and diarrhoeic patients in Egypt.

Methods

A total of 150 samples comprising (100 poultry meat and 50 diarrhoeic patients’ stool) were examined for the presence of Salmonella spp. using culture methods followed by biochemical and serological identification of the isolates. All Salmonella strains were tested for their susceptibility to the antibiotics using disk diffusion method and screened for the presence of virulence genes and class I integrons using PCR.

Results

The overall prevalence of Salmonella spp. in poultry meat samples was 10 % compared to 4 % in diarrhoeic patients. All the isolates were serologically identified into Salmonella Typhimurium (seven isolates), S. Derby, S. Kiel, S. Rubislaw (one isolate, each) and untypable strains (two isolates). Antibiotic susceptibility testing showed a higher resistance of the total isolates to erythromycin and tetracycline (100 %, each), followed by amoxicillin-clavulanic acid (91.7 %), trimethoprim-sulfamethoxazole (83.3 %), streptomycin, nalidixic acid, ampicillin-sulbactam (75 %, each), gentamycin, ampicillin (66.7 %, each), chloramphenicol (58.3 %), ciprofloxacin (25 %) and ceftriaxone (16.7 %). Virulence genes profiles revealed the presence of sopB gene in five Salmonella strains isolated from poultry meat (n = 3) and humans (n = 2). Moreover, pefA was only identified in three isolates from poultry meat. On the other hand, S. Kiel and S. Typhimurium (one isolate, each) were harboring hilA and stn genes, respectively. Class 1 integrons were detected in all Salmonella spp. with variable amplicon sizes ranged from 650–3000 bp. Sequencing of these amplicons revealed the presence of gene cassettes harboring aac(3)-Id, aadA2, aadA4, aadA7, sat, dfrA15, lnuF and estX resistance genes. Nucleotide sequence analysis showed point mutations in the aac(3)-Id of S. Derby, aadA2, estX-sat genes of S. Typhimurium. Meanwhile, frame shift mutation was observed in aadA7 genes of S. Typhimurium.

Conclusions

Increasing rate of antimicrobial resistance and class 1 integrons among multidrug resistant Salmonella spp. has prompted calls for the reduction of antimicrobial use in livestock to prevent future emergence of resistance.

Identification and characterization of class 1 integrons among atypical enteropathogenic Escherichia coli isolated from children under 5 years of age

BACKGROUND AND OBJECTIVES

The therapeutic options for diseases caused by Escherichia coli are limited. In this study we investigated the presence of virulence factors among Enteropathogenic Escherichia coli (EPEC) strains and their antibiotic resistance patterns. The isolates were also checked for the presence of class1 integrons and gene cassettes.

MATERIALS AND METHODS

This study included 70 EPEC strains isolated from children. Antimicrobial resistance patterns were determined using diffusion methods. The broth microdilution methods was used to determine the minimum inhibitory concentration. PCR was used to detect eaeA, bfpA genes. The 5' and 3' conserved sequences (CSs) of class 1 integrons and intI gene were amplified to investigate the presence of integrons and gene cassettes.

RESULTS

Antimicrobial susceptibility testing showed that 4 (5.7%), 3 (4.2%), and 2 (2.8 %) isolates were resistant to ampicillin, trimethoprim-sulfamethoxazole, and ceftazidime, respectively. Resistance rates to ciprofloxacin and aztreonam were 1.4%. Thirteen (18.5%) isolates showed resistance to tetracycline, and 4 (5.7%) were kanamycin resistant. Class I integron detected in 22 (31.4%) isolates. All the gene cassettes found in class I integrons corresponded to different variants of dfr and aadA genes.

CONCLUSION

Prevalence of class I integrons in EPEC strains was high. Presence of aadA and dfr gene cassettes in integrons represents high distribution of resistance determinants in EPEC strains.