Outbreak of Dysentery Associated with Ceftriaxone-Resistant Shigella sonnei : First Report of Plasmid-Mediated CMY-2-Type AmpC β-Lactamase Resistance in S. sonnei

Abstract

We document the first report of plasmid-encoded CMY-2-type AmpC ␤-lactamase identified among Shigella sonnei isolates resistant to ceftriaxone and obtained after an outbreak of bacillary dysentery in Taiwan. One hundred eighty-two children in two elementary schools in Yu-Li, Taiwan, where an outbreak occurred after a typhoon hit this area in 2001, were enrolled in this study. Clinical and epidemiologic data on the infected children were collected. Pulsed-field gel electrophoresis (PFGE) was performed on the isolates to determine the genetic relatedness of outbreak strains. Plasmid analysis and PCR were performed to identify ␤-lactamase genes responsible for ceftriaxone resistance. Forty-seven children from the two elementary schools were culture positive for S. sonnei in this outbreak. Twenty-three children were asymptomatic. Of the total isolates 55.3% were resistant to ampicillin. One hundred percent of the isolates obtained from children in school A were initially susceptible to both ampicillin and ceftriaxone. Of isolates obtained from school B 96.2% were nonsusceptible to ceftriaxone. However, two isolates from school A developed resistance to ampicillin during the course of treatment. All 18 available isolates showed closely related PFGE patterns (4, 4a, 4b, and 4c). CMY-2-type AmpC ␤-lactamase was responsible for ceftriaxone resistance in ceftriaxone-nonsusceptible isolates; Southern blot hybridization confirmed that such a resistance gene was located on the plasmid. This is the first report of plasmid-mediated CMY-2-type AmpC ␤-lactamase in S. sonnei. Ampicillin-resistant isolates can develop during the course of antibiotic treatment.Shigellosis is primarily a disease of poor, crowded communities that do not have adequate sanitation or clean water. Among the four Shigella species, S. flexneri is the most commonly isolated species in the developing world. However, in industrialized countries, the predominant species is S. sonnei, which accounts for 90% of the infections caused by Shigella spp. (25). Despite the continual improvement of sanitary conditions and the socioeconomic level of the population in Taiwan, outbreaks of shigellosis still occur after natural disasters such as typhoons or earthquakes.Resistance of Shigella spp. to various antibiotics is increasing (26); however, plasmid-encoded resistance of Shigella spp. to extended-spectrum cephalosporins is still rare. Genetic testing is required to identify the relationship and mechanism of antimicrobial resistance in outbreak situations. Pulsed-field gel electrophoresis (PFGE) is a useful epidemiological tool but provides limited information about the genetic (plasmid) profile of the microorganisms. The purpose of this study was to investigate the epidemiological, clinical, and microbiological features of an outbreak of Shigella dysentery caused by S. sonnei in Yu-Li, Hua-Lien, Taiwan. Of note, this is the first report documenting production of CMY-2-type AmpC ␤-lactamase by S. sonnei. MATERIALS AND METHODSPatients and population. An outbreak of ba...

Molecular characterization of extended-spectrum β-lactamase-producing Shigella isolates from humans in South Africa, 2003–2009

“…The remaining five isolates were identified as Shigella sonnei phase II (4/20, 20 %) and Shigella dysenteriae 3 (1/20, 5 %). These data are in agreement with the distribution of Shigella serotypes in developing countries (Huang et al, 2005). All 20 isolates were resistant to ampicillin, amoxicillin/clavulanic acid and sulfamethoxazole/trimethoprim.…”

“…The CTX-M-type b-lactamase gene was the most commonly identified ESBL via PCR analysis, with DNA sequencing identifying bla CTX-M-15 in 18 isolates and bla CTX-M-14 in one isolate (Table 1). These data are in agreement with worldwide data, which describe bla CTX-M-15 and bla CTX-M-14 as the most common genes encoding CTX-M-type b-lactamases identified in members of the genus Shigella (Mushtaq et al, 2003;Huang et al, 2005). Members of the family Enterobacteriaceae that produce CTX-M-type b-lactamases are a major cause of disease outbreaks and sporadic infections worldwide (Mushtaq et al, 2003).…”

“…This enzyme has been reported in isolates of S. sonnei from Taiwan and is the most commonly encountered plasmid-borne AmpC b-lactamase worldwide (Huang et al, 2005). The bla CMY-2 gene confers bacterial resistance to penicillins, cephalosporins and aztreonam (Rankin et al, 2005).…”

“…Shigella flexneri serotype 2a is the predominant pathogen responsible for bacillary dysentery in developing countries (Huang et al, 2005). Due to their ability to acquire mobile genetic elements, such as resistance plasmids and transposons, species of the genus Shigella have progressively acquired resistance to antimicrobials that are used in treatment of bacillary dysentery (Vinh et al, 2009).…”

“…It is not uncommon for members of the family Enterobacteriaceae to carry multiple b-lactamase genes (Huang et al, 2005). This was also true of the isolates described in the current study, most of which carried multiple b-lactamase genes, including: bla TEM-1 , bla SHV-2 and bla CTX-M-15 (n51); bla TEM-1 , bla CTX-M-15 and bla CMY-2 (n55); bla TEM-1 and bla CTX-M-15 (n59); and bla TEM-1 and bla CMY-2 (n51).…”