Antimicrobial Resistance and Genetic Diversity of Shigella sonnei Isolates from Western Ireland, an Area of Low Incidence of Infection

Abstract

Shigella sonnei is a significant cause of gastroenteritis in both developing and industrialized countries. Definition of the diversity and antimicrobial susceptibility of S. sonnei isolates may be helpful in the management of individual cases and outbreaks. Antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) were performed with 67 isolates of S. sonnei predominantly (n ‫؍‬ 59) from three counties in the west of Ireland. Phage typing (n ‫؍‬ 17), plasmid profiling (n ‫؍‬ 28), and integron analysis (n ‫؍‬ 24) were performed with subsets of strains. PFGE typing permitted recognition of two major clusters: PFGE type A (n ‫؍‬ 53) and PFGE type B (n ‫؍‬ 14). PFGE type A was associated with resistance to ampicillin, streptomycin, and sulfonamides (51 of 53 isolates), and those that were phage typed (n ‫؍‬ 6) were phage type 3. PFGE type B was associated with resistance to streptomycin, sulfonamides, tetracycline, and trimethoprim (11 of 14 isolates) and phage type 6 (9 of 11 isolates). Fifteen different plasmid profiles were identified among the 28 isolates analyzed. A class 2 integron was present in all 14 PFGE type B isolates. One of these isolates also contained a class 1 integron and showed a unique variant of the PFGE type B pattern. Sequence analysis of the gene cassette structures contained within these integrons identified distinct open reading frames that encoded determinants of resistance to trimethoprim, streptomycin, and streptothricin. Our data demonstrate two predominant PFGE types among S. sonnei isolates circulating in this region. The limited diversity of the S. sonnei isolates in this region means that detection of isolates indistinguishable by PFGE and according to their antibiograms in two or more patients is not persuasive evidence of a common-source food-or waterborne outbreak. Indistinguishable plasmid profiles in addition to indistinguishable PFGE and antibiogram types may be more suggestive of an epidemiologically relevant link between cases.

Genotypes and antimicrobial profiles of Shigella sonnei isolates from diarrheal patients circulating in Beijing between 2002 and 2007

“…We have used PFGE to characterize the diversity of S. sonnei isolates and to determine the clonality of these isolates in subtype levels as other studies have previously reported (DeLappe et al, 2003;Huang et al, 2005). In our study, the PFGE genotype analysis of 272 S. sonnei strains indicated that 96.7% were determined to be 1 epidemic clonal genotype A.…”

Surveillance of Antimicrobial Susceptibility Patterns among Shigella Species Isolated in China during the 7-Year Period of 2005-2011

“…The number of deaths due to shigellosis has been estimated to be 1.1 million annually, particularly among children in developing countries [1]. S. sonnei is the predominant cause of shigellosis in developed countries, and it is more common in children than in adults [10, 11]. However, in developing countries with low socioeconomic conditions, S. flexneri is the predominant species.…”

A 10-year surveillance of antimicrobial susceptibility patterns in Shigella sonnei isolates circulating in Jiangsu Province, China

“…The class 1 integron containing 0.15-kb and 2.2-kb amplicons was the most common type in this study, and aacA4-cmlA1 was the most prevalent gene cassette, conferring resistance to aminoglycoside and chloramphenicol, respectively. The gene cassette array dfrA1-sat1-aadA in class 2 integrons conferred resistance to trimethoprim, streptothricin and streptomycin [16,36]. The gene cassette bla OXA-30 -aadA1, conferring resistance to b-lactams and aminoglycosides, was detected in an atypical class 1 integron.…”