Mosaic Structure of a Multiple-Drug-Resistant, Conjugative Plasmid from Campylobacter jejuni

Abstract

Partial sequence analysis of a tet(O) plasmid from a multiple-drug-resistant clinical isolate of Campylobacter jejuni revealed 10 genes or pseudogenes encoding different aminoglycoside inactivating enzymes, transposaselike genes, and multiple unknown genes from a variety of pathogenic and commensal bacteria. The plasmid could be mobilized by a P incompatibility group plasmid into Escherichia coli, where it apparently integrated into the chromosome and expressed high-level resistance to multiple aminoglycoside antibiotics. This work provides new information about both the nature of drug resistance in C. jejuni and the ability of C. jejuni to exchange genes with other bacterial species.Campylobacter jejuni is among the most frequent causes of diarrheal disease worldwide (2, 23), and the incidence is particularly high in Thailand, where both antimicrobial resistance and multidrug resistance are increasing problems (6). Although the levels of resistance to the macrolides erythromycin and azithromycin have remained low, the incidence of resistance to the quinolones has risen to 96% in a 1998 study of U.S. military personnel (22). Plasmid-mediated resistance to tetracycline, chloramphenicol, and kanamycin has been well documented in C. jejuni (25,31,29), but no other plasmidencoded resistance genes have been reported, other than a very recent report of streptomycin and streptothricin resistance (12). Recently, comparison of the sequences of transferable tet(O) plasmids from a C. jejuni strain and a C. coli strain isolated on different continents more than 20 years apart revealed high conservation (4, 5). Surveys of clinical isolates of C. jejuni in Thailand in our laboratories have revealed a high incidence of both multiple drug resistance and plasmids (unpublished data). Given these observations, we hypothesized that at least some of these antibiotic resistances in recent Thai isolates were plasmid encoded. Here we describe the partial genetic structure of a multiple-drug-resistant plasmid from a Thai clinical isolate of C. jejuni. The plasmid is related to other tet(O) plasmids but is novel in that it also contains multiple aminoglycoside-inactivating enzymes and transposon-like sequences from a variety of bacteria that have not previously been reported in C. jejuni.(This work was done in partial fulfillment of the requirements for a Ph.D. degree from Mahidol University by W.N.) MATERIALS AND METHODSBacterial strains and plasmids. C. jejuni strain CG8245 was isolated from a diarrhea case of a U.S. soldier deployed to Thailand during a military exercise in 1999. Escherichia coli DH5␣ was used as the host for cloning experiments, and pBluescript (Stratagene, La Jolla, CA) was used as the cloning vector. For conjugation experiments with another C. jejuni strain, a mutant of C. jejuni NCTC 11168 that had been insertionally inactivated with a chloramphenicol resistance (cat) cassette (32) in the Cj1316c gene was used as the recipient (P. Guerry, unpublished data). For conjugation experiments with E. coli, E. coli C600(RK...

Genome Sequence of a Clinical Isolate of Campylobacter jejuni from Thailand

“…These contigs cover 37 kb of the 45.2 kb of pTet, and experimental analysis confirmed the presence of an approximately 45-kb plasmid in CG8486 (data not shown). The presence of a tetO gene on the CG8486 plasmid is consistent with the observed resistance of this strain to tetracycline and with the reported high incidence of tetracycline resistance among C. jejuni strains from Asia (26). The cpp2, cpp3, cpp4, cpp6, cpp7, cpp24, cpp25, and cmgB7 genes, which code for proteins with unknown functions, and repA, encoding a putative replication initiator protein, appear to be missing from the CG8486 plasmid, as sequenced.…”

Characterization of Two Campylobacter jejuni Strains for Use in Volunteer Experimental-Infection Studies

“…Thus, as shown in Table 5, homologs of other pTet and pCC31 genes (Cj8421_0812, Cj8421_0816, Cj8421_0820, and Cj8421_0821) are also found in zone 11. Additionally, there are two transposase genes (Cj8421_0822 and Cj8421_0823) at this locus that were found on a plasmid from another C. jejuni isolate from Thailand (40). This suggests that a transposition event was responsible for the integration of part of a tetracycline plasmid into the chromosome of CG8421.…”

Antimicrobial Susceptibilities of Campylobacter jejuni Isolates from Poultry from Alberta, Canada

“…While multidrug resistance in C. jejuni isolates from poultry (9/104) is not common, the report of multidrug-resistant conjugative plasmids within C. jejuni (20) combined with the minimal regulation of antimicrobial usage (12) may result in the appearance of more such isolates.…”

“…One study suggested that the tet(O) gene may be rapidly and spontaneously transferred in vivo without antimicrobial selection pressure between C. jejuni strains in the digestive tracts of chickens (3). Surveillance of tetracycline resistance is important due to the potential for plasmid-mediated transfer of the tet(O) gene (25) as well as genes encoding resistance to other antimicrobials (20) for other potential pathogens.…”