Identification of the Conjugative mef Gene in Clinical Acinetobacter junii and Neisseria gonorrhoeae Isolates

Abstract

The mef gene, originally described for gram-positive organisms and coding for an efflux pump, has been identified in clinical isolates of Acinetobacter junii and Neisseria gonorrhoeae. These strains could transfer the mef gene at frequencies ranging from 10 ؊6 to 10 ؊9 into one or more of the following recipients: gram-negative Moraxella catarrhalis, Neisseria perflava/sicca and Neisseria mucosa and gram-positive Enterococcus faecalis. Three Streptococcus pneumoniae strains could transfer the mef gene into Eikenella corrodens, Haemophilus influenzae, Kingella denitrificans, M. catarrhalis, Neisseria meningitidis, N. perflava/sicca, and N. mucosa at similar frequencies. The mef gene can thus be transferred to and expressed in a variety of gram-negative recipients.The mef gene encodes a membrane-bound efflux protein and confers resistance to macrolides but not to lincosamides or streptogramin B (24, 25). From geographically diverse areas, two gene variants with 90% nucleotide sequence identity, mefA and mefE, have been identified in gram-positive organisms, including Streptococcus pneumoniae, Streptococcus pyogenes, Corynebacterium spp., Enterococcus spp., Micrococcus luteus, and viridans group streptococci (2,5,9,20,(23)(24)(25). Both genes have now been combined as mef(A) (20).Recently, we have shown that both Neisseria gonorrhoeae and oral commensal Neisseria spp. carry known rRNA methylase genes (20). However, we have also identified several of these Neisseria spp. and oral gram-negative isolates that were macrolide resistant yet did not carry Erm determinants (ErmA, -B, -C, or -F) (21). We selected a gram-negative Acinetobacter junii strain and screened two groups of N. gonorrhoeae in order to determine if the mef gene was present. Because we have shown that the mef gene can be transferred by conjugation in various gram-positive genera, we also wanted to determine the mobility of the mef gene in these gram-negative isolates as well as the ability of gram-positive donors to move the mef gene to gram-negative species (9).(This work was presented, in part, at the 39th Interscience Conference on Antimicrobial Agents and Chemotherapy, 23 to 27 September 1999, San Francisco, Calif.) MATERIALS AND METHODSBacteria. Erythromycin-resistant (Ery r ) Acinetobacter junii strain 329 was isolated from the oral gumline of a child in Portugal (Table 1). The organism was identified by D. Stroman (Alcon Laboratories, Inc., Fort Worth, Tex.) by sequencing the 16S rRNA. Sixteen N. gonorrhoeae isolates with variable susceptibilities to erythromycin (MIC ϭ 0.25 to 4 g/ml) were collected from urethral specimens from adults in Seattle, Wash., and identified by the Neisseria Reference Laboratory at the University of Washington (Table 1). Thirteen N. gonorrhoeae isolates carrying the tetM 25.2-MDa plasmid were collected in Seattle and the eastern United States during 1983 through 1986 and have been previously described (7). Of the three Ery r S. pneumoniae strains carrying the mef gene, two (n011 and 970146) were isolated in Washington...

Clinical and Molecular Epidemiology of Erythromycin-Resistant Beta-Hemolytic Lancefield Group G Streptococci Causing Bacteremia

“…Macrolide resistance in beta-hemolytic group G streptococci has resulted from horizontal transfer of mef genes among different species of streptococci, staphylococci, and enterococci, as well as among the beta-hemolytic group G streptococci themselves. Efflux of macrolides, mediated by mef genes, has been described mainly in various gram-positive cocci (5,7,8,11,12). From the available sequence information, it can be observed that the amino acid sequence corresponding to the mef gene (AY355407) of the beta-hemolytic group G streptococcus strain isolated from one patient shared more than 99% identity with that corresponding to a mef gene (U70055) from a strain of S. pyogenes (Fig.…”

Moraxella catarrhalis: from Emerging to Established Pathogen

“…Expansion of such competitive types has also been documented during distinct periods and in particular geographic regions (157). Frequent horizontal gene transfer seems possible (31,150), and in relation to the observations made for complement resistance, it may be postulated that other phenotypic traits could be acquired through cross-species gene acquisition. For instance, Bootsma et al (31) demonstrated that the barrier between M. catarrhalis and gram-positive microorganisms may be occasionally crossed by antimicrobial resistance genes.…”

Distribution of mef (A) in Gram-Positive Bacteria from Healthy Portuguese Children

“…All four of these sequences were identical to each other at the DNA and amino acid levels and identical with the GenBank U83667 and AF376746 sequences. Seventeen of the isolates in Table 3 hybridized with orf1 to orf8 from Tn1207.1, and seven of the isolates have been shown here or previously (5,6) to transfer the mef(A) gene to related and/or unrelated recipients. Whether these strains carry transposons similar to Tn1207.3, a recently described conjugal element from S. pyogenes (Santagati et al, 41st ICAAC), needs to be investigated.…”

“…strain 130, and E. faecalis 2, as the donors. Matings were done as previously described (1,2,5,6,8,13). We also used the S. aureus 5 and S. intermedius 424 donors with Kingella denitrificans 87.023461 and Neisseria mucosa CTM1.1 as recipients as previously described (6).…”

“…isolated in Seattle, Wash., and Micrococcus luteus and Corynebacterium spp. isolated in the United Kingdom (5), as well as in gram-negative Acinetobacter junii and Neisseria gonorrhoeae (6). All of these species have been able to conjugally transfer the mef(A) genes to a variety of recipients.…”