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Published on: July 21, 2023
Prevalence of integrons in antibiotic-resistant Salmonella spp. in Hong Kong
1Department of Microbiology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong SAR, P. R. China.
Abstract:
Of the 834 Salmonella spp. isolates collected from 2002 to 2004 in the New Territories East Cluster hospitals in Hong Kong, 21% were resistant to 3-14 antibiotics and 30% were resistant to nalidixic acid with reduced susceptibility to ciprofloxacin. A class 1 integron was present in 105 (13%) isolates, of which more than 50% were Salmonella Typhimurium. Class 2 or 3 integrons were not detected in any of the isolates. DNA sequencing showed that there were 16 different integrons, of which the most common, detected in 40% of isolates, was dfrA12-orfF-aadA2. Almost half of the isolates had lost the qacEdelta1-sulI 3' conserved segment (3'CS). Four isolates had an orf513 gene downstream of the 3'CS. There was probably one predominant clone among each heterogeneous population of integron-harboring S. Typhimurium, S. Virchow, and S. Derby isolates in our community. This is the first thorough study of the prevalence and characteristics of integrons in Salmonella isolates in Hong Kong and the first to report a class 1 integron in S. Birkenhead, S. Landwasser, S. Litchfield, and S. Reading.
Insights
A study of Salmonella in Hong Kong found that 13% of isolates carried class 1 integrons, often linked to antibiotic resistance. This research highlights the prevalence of specific integron types and their genetic elements in bacterial populations.
Area of Science:
- Microbiology
- Molecular Biology
- Public Health
Background:
- Salmonella spp. are significant foodborne pathogens.
- Antibiotic resistance in bacteria is a growing global concern.
- Integrons are genetic elements that contribute to antibiotic resistance.
Purpose of the Study:
- To investigate the prevalence and characteristics of integrons in Salmonella isolates from Hong Kong.
- To identify specific integron types and associated antibiotic resistance genes.
- To understand the genetic diversity and clonal structure of integron-harboring Salmonella.
Main Methods:
- Collection and antimicrobial susceptibility testing of 834 Salmonella isolates (2002-2004).
- Detection and characterization of integrons using molecular methods, including DNA sequencing.
- Analysis of the genetic structure of integrons, including conserved segments and associated genes.
Main Results:
- 21% of isolates showed resistance to 3-14 antibiotics; 30% were resistant to nalidixic acid.
- Class 1 integrons were found in 13% of isolates, predominantly in Salmonella Typhimurium.
- Sixteen different integrons were identified, with dfrA12-orfF-aadA2 being the most common; loss of the 3' conserved segment was frequent.
Conclusions:
- Class 1 integrons are present in Hong Kong Salmonella isolates and are associated with multidrug resistance.
- Specific integron structures and predominant clones were identified, suggesting localized dissemination.
- This study provides crucial data on integron epidemiology in Salmonella within the region.
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