Antibiotic resistance and genetic diversity of Shigella sonnei isolated from patients with diarrhoea between 1999 and 2003 in Bangladesh

Abstract

Shigella sonnei is a significant cause of diarrhoeal infection in both developing and industrialized countries. From 1999 to 2003, 445 strains of Shigella sonnei were isolated from patients admitted to the diarrhoea treatment centre of the International Center for Diarrhoeal Disease Research, Bangladesh. More than 60 % of the isolates were resistant to nalidixic acid, 89 % to sulfamethoxazole-trimethoprim and 9?5 % to ampicillin. In addition, 4 % of strains were resistant to multiple antibiotics (Amp R Tet R Sxt R Str R ) and 4?2 % of strains were sensitive to all antibiotics tested. None of the strains were positive for the set1 gene, whereas 46 % were positive for the sen gene. Forty-six per cent of the strains (stored at "70 6C) harboured the 120 MDa invasive plasmid and representative strains produced keratoconjunctivitis in the guinea pig eye. In addition, three plasmids of approximately 5, 1?8 and 1?4 MDa were found to be present in more than 90 % of the strains. A self-transmissible, middle-ranged plasmid (35-80 MDa) carrying the multiple antibiotic resistance gene was found in some strains. PFGE analysis of the strains identified five unique types with many subtypes, which were characterized into four unique types by ribotyping analysis. It can be concluded that endemic strains of Shigella sonnei isolated from patients in Bangladesh are diverse in their genetic pattern. INTRODUCTIONBacillary dysentery caused by Shigella species is a serious public health problem in both developing and industrialized countries (Lee et al., 2000;Pan, 1996) and outbreaks due to Shigella infection are difficult to control because of their low infectious dose (Dupont et al., 1989). Increased numbers of cases in a community that appear to be sporadic may in fact be due to unrecognized outbreaks (Litwin et al., 1997). Shigellosis is caused by any of the four species of Shigella, namely Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei. Of these, Shigella sonnei is the most prevalent (77 %) species in industrialized countries and the second most prevalent in developing countries, followed by Shigella flexneri (Kotloff et al., 1999). Shigellosis is endemic in Bangladesh and accounts for 20 % of deaths related to diarrhoea among children (Victora et al., 1993). Fatality rates due to Shigella sonnei infection are highest among children less than 1 year old in Bangladesh (Bennish et al., 1990). Species-wise incidence of shigellosis including that caused by Shigella sonnei in Bangladesh was reported in a previous study (Talukder et al., 2003b). Unlike developed and industrialized countries, an extensive study on Shigella sonnei in terms of clonal diversity and antimicrobial resistance pattern has not been undertaken in the developing world and particularly in Bangladesh. In the past, several conventional typing methods were used for epidemiological subtyping of Shigella sonnei (Lin & Chang, 1992;Morris & Wells, 1974;Pruneda & Farmer, 1977) based on phenotypic properties, but the usefulness of these techniq...

In-vitro antimicrobial susceptibility testing of bacteria causing diarrhea in children at Khartoum StateSudan

“…In the present study the frequency of Shigella isolates resistant to nalidixic acid was only 16.4%. In contrast with data collected in other countries such India, Bangladish, where reported resistance rates exceed 60% [12].…”

Genetic characteristics and changing antimicrobial resistance among Shigella spp. isolated from hospitalized diarrhoeal patients in Kolkata, India

“…Since 2002, isolation of this serotype has steadily declined compared with S. flexneri, and S. dysenteriae type 1 was not isolated from 2005 in Kolkata or other locations such as Bangladesh (Talukder et al, 2006a). We have identified one S. dysenteriae type 1 isolate in 2010, indicating the existence of an isolate that has epidemic potential in our setting.…”

“…In a previous study, S. sonnei isolates were resistant to nalidixic acid, but none were resistant to ciprofloxacin (Pazhani et al, 2005). During 1999-2003, .60 % of Bangladeshi S. sonnei isolates were resistant to nalidixic acid, but none to ciprofloxacin (Talukder et al, 2006a). In developed countries, although nalidixic acid resistance was common among S. sonnei isolates, the trend of fluoroquinolone resistance is slowly increasing (Kim et al, 2008;Vrints et al, 2009).…”

Characterization and complete genome sequence of a novel N4-like bacteriophage, pSb-1 infecting Shigella boydii

“…It is known that the isolation rate of S. boydii is less than 1e2% of all Shigella isolates [40]. Although antibiotic therapy is considered an effective treatment for shigellosis, the imprudent use of antibiotics has led to the increase of multiple-antibiotic-resistant Shigella species globally [5,20,26,33,36,39]. Increasingly, there have been more reports of antibiotic resistance in S. boydii strains.…”