New Cluster of Plasmid-Located Class 1 Integrons in Vibrio cholerae O1 and a dfrA15 Cassette-Containing Integron in Vibrio parahaemolyticus Isolated in Angola

Abstract

The resistance profile and its correlation with mobile genetic elements were investigated in 11 Vibrio cholerae O1 and 2 Vibrio parahaemolyticus clinical isolates, as well as in 1 V. cholerae O1 and 1 V. cholerae non-O1 environmental isolate, isolated between 1991 and 1996 in different provinces of Angola. All clinical isolates of V. cholerae O1 were resistant to ampicillin, chloramphenicol, trimethoprim, sulfamethoxazole, and tetracycline. They also contained a large conjugative plasmid (p3iANG) with a set of three class 1 integrons harboring dfrA15, blaP1, and qacH-aadA8 cassettes, which code for resistance to trimethoprim, beta-lactams, quaternary ammonium compounds, and aminoglycosides, clustered in a 19-kb region. Chloramphenicol (cat1), kanamycin (aph), sulfonamide (sul2), and tetracycline (tetG) resistance genes were also carried on the plasmid within the same 19-kb region. A chromosomal integron containing the dfrA15 cassette was also revealed in V. parahaemolyticus strains. SXT integrase genes were present in six V. cholerae isolates but apparently were not associated with known SXT-associated resistance genes. This study indicates that plasmids and integrons contributed mainly to the circulation of multiple-drug resistance determinants in Vibrio strains from Angola.The genus Vibrio includes harmless aquatic strains as well as strains capable of causing diseases and epidemics, mainly in developing countries. Vibrio cholerae O1 and O139, the causative agents of cholera epidemics, and Vibrio parahaemolyticus, a cause of acute gastroenteritis in humans, can be isolated from infected patients as well as from the aquatic environment.Besides morbidity and mortality, multiple-drug resistance expressed by pathogenic bacteria is a major public health problem, and both V. cholerae-and V. parahaemolyticus-resistant strains may contribute to the spread of resistance through mobile genetic elements. Genetic horizontal transfer alone may explain the rapid acquisition of resistance determinants seen in epidemic strains and their high variability among different outbreaks in the same area. It is well known that in V. cholerae as well as in other enteric pathogens, large plasmids are able to confer resistance to drugs and to be naturally conjugative (7,14).Integrons are an important mechanism for the acquisition of antibiotic resistance genes in many bacteria (16, 17), including V. cholerae. These elements are not autonomously mobile but are able to capture, integrate, and express resistance cassettes in their variable regions (28). So far, several classes of integrons have been identified according to integrase sequence located in the 5Ј conserved sequence (CS). Class 1 integrons have been found to be present among clinical V. cholerae isolates and are usually characterized by the presence of qacE⌬1 and sul1 genes, which provide resistance to quaternary ammonium compounds and sulfonamide, respectively, in the 3Ј CS. To our knowledge, no resistance integrons have been found in Vibrio spp. other than V. cholerae, with th...

Antibiotic resistance among bacterial pathogens in Central Africa: a review of the published literature between 1955 and 2008

“…Similar findings were described in Bangui (CAR) [66]. [40,42,[67][68][69][70][71][72][73][74][75] Eleven reports from nearly all countries in the region were available. Most were published in the second half of the 1990s, often describing outbreaks among refugees, all by V. cholerae O1 El Tor.…”

Genetic Context and Biochemical Characterization of the IMP-18 Metallo-β-Lactamase Identified in a Pseudomonas aeruginosa Isolate from the United States

“…The qacF-like gene encodes a quaternary ammonium compound resistance protein variant identical to a QacF variant reported only once in the database (accession no. DQ149925) encoded by a plasmid-borne cluster of three integrons in several isolates of Vibrio cholerae (2) and showing two amino acid substitutions (L7M and S10A) compared with the QacF determinant encoded by In40 from Enterobacter aerogenes BM2688 (21). It encodes an efflux protein belonging to the small multidrug resistance family and shows sequence similarity with other Qac/Erm-type drug:proton antiporters that have been reported in other integrons or hosts (sequence identity ranging from 79.3 to 35.1% with QacG and QacC, respectively) (15,16).…”

Clinical isolates of Vibrio fluvialis from Kolkata, India, obtained during 2006: plasmids, the qnr gene and a mutation in gyrase A as mechanisms of multidrug resistance

“…Three plasmid-bearing strains (L13828, L10734 and L9978) were tested for their ability to transfer resistance traits to a recipient strain in conjugation experiments. These experiments were carried out according to a published protocol (Ceccarelli et al, 2006). For strain L13828, which was sensitive to nalidixic acid as well as to streptomycin, both E. coli DH5a and V. cholerae O1 El Tor were used as recipients.…”