Cholera in Vietnam: Changes in Genotypes and Emergence of Class I Integrons Containing Aminoglycoside Resistance Gene Cassettes in Vibrio cholerae O1 Strains Isolated from 1979 to 1996

Abstract

The number of cholera cases and the mortality rates reported from different regions of Vietnam varied considerably in the period from 1979 to 1996, with between 2,500 and 6,000 cases reported annually from 1992 to 1995. Annual mortality rates ranged from 2.0 to 9.6% from 1979 to 1983 to less than 1.8% after 1983. Major cholera outbreaks were reported from the High Plateau region for the first time in 1994 and 1995; this is an area with limited access to health services and safe drinking-water supplies. All cases were associated with Vibrio cholerae O1. Using ribotyping, cholera toxin (CT) genotyping, and characterization of antibiotic susceptibility patterns and antibiotic resistance genes by PCR, we show that strains isolated after 1990 were clearly different from strains isolated before 1991. In contrast to strains isolated before 1991, 94% of 104 strains isolated after 1990 showed an identical ribotype R1, were resistant to sulfamethoxazole and streptomycin, and showed a different CT genotype. Furthermore, PCR analysis revealed that sulfamethoxazole-resistant strains harbored class I integrons containing a gene cassette ant(3")-1aencoding resistance to streptomycin and spectinomycin. This is, to our knowledge, the first report of class I integrons in V. cholerae. The development of cholera and the changes in the phenotypic and genotypic properties of V. cholerae O1 shown in the present study highlight the importance of monitoring V. cholerae O1 in Vietnam as in other parts of the world. In particular, the emergence of the new ribotype R1 strain containing class I integrons should be further studied.

Bacterial resistance evolution by recruitment of super‐integron gene cassettes

“…The perpetual phenomenon of lateral gene transfer (Jain et al, 1999) will inevitably lead to an encounter between a class 1 integron and a bacterial species harbouring a SI. This is supported by the recent finding of class 1 integrons in many V. cholerae isolates (Dalsgaard et al, 1999;2000a,b;Falbo et al, 1999) and a new fourth class of resistance integron in the SXT ET constin of V. cholerae (Hochhut et al, 2001). We have shown that class 1 integrons can randomly recruit the gene cassettes harboured within SIs.…”

Resistance integrons and super-integrons

“…Several studies have described the presence of a class 1 integron in multiple strains or species [15], outbreaks caused by a single strain with an integron [17,29,33,59], multiple integrons [78,79], or a combination of these factors [8][9][10][11]18,19,21,32,55,58,80]. Remarkably, most of these reports come from Western Europe and Eastern Asia, but there are also reports from Africa [55,60,81] and South America [13,65,81].…”

Molecular characterization of ICEVchVie0 and its disappearance inVibrio choleraeO1 strains isolated in 2003 in Vietnam

“…Vibrio cholerae O1 biotype El Tor came to South Vietnam in 1964 from Indonesia and was detected mainly in the central coastal areas and in South Vietnam. Besides the specific natural and socio economic factors, the long lasting war contributed to the epidemic explosion of the disease (Dalsgaard et al, 1997(Dalsgaard et al, , 1999. In recent years, prevention by vaccine campaigns (Vu et al, 2003) and environmental control as well as case treatment resulted in a significant control of cholera epidemics in Vietnam and a relative low drug resistance profile in V. cholerae, compared with other epidemics in other developing countries (Dalsgaard et al, 2001;Thungapathra et al, 2002).…”

“…In the first half of the 1990s new multiple resistant strains of V. cholerae O1 emerged: these strains were characterized by streptomycin and spectinomycin resistances located on class 1 integrons (Dalsgaard et al, 1999). Aminoglycoside resistant integrons have also been found in Shigella spp.…”

“…strains isolated from patients with diarrhea in Vietnam (Iversen et al, 2003). The worldwide occurrence of class 1 integrons in many enteric bacteria, including V. cholerae, and their role in acquisition and diffusion of drug resistance, is well documented (Dalsgaard et al, 1999(Dalsgaard et al, , 2000(Dalsgaard et al, , 2001Thungapathra et al, 2002).…”