Acquired Macrolide Resistance Genes in Pathogenic Neisseria spp. Isolated between 1940 and1987

Of the 176 randomly selected, commensal, gram-negative bacteria isolated from healthy children with low exposure to antibiotics, 138 (78%) carried one or more of the seven macrolide resistance genes tested in this study. These isolates included 79 (91%) isolates from the oral cavity and 59 (66%) isolates from urine samples. The mef(A) gene, coding for an efflux protein, was found in 73 isolates (41%) and was the most frequently carried gene. The mef(A) gene could be transferred from the donors into a gram-positive E. faecalis recipient and a gram-negative Escherichia coli recipient. The erm(B) gene transferred and was maintained in the E. coli transconjugants but was found in 0 to 100% of the E. faecalis transconjugants tested, while the other five genes could be transferred only into the E. coli recipient. The individual macrolide resistance genes were identified in 3 to 12 new genera. Eight (10%) of the oral isolates and 30 (34%) of the urine isolates for which the MICs were 2 to >500 g of erythromycin per ml did not hybridize with any of the seven genes and may carry novel macrolide resistance genes.The use of macrolide and related antibiotics (ketolides, oxazolidinones, streptogramins, and lincosamide) has increased dramatically over the last 15 years. A number of different mechanisms of macrolide resistance have been reported for gram-negative bacteria. These mechanisms include two esterase genes [ere(A) and ere(B)] found in Escherichia coli and Enterobacter, Klebsiella, Citrobacter, and Proteus species (1) and more recently, in Providencia stuartii, Pseudomonas species, and Vibrio cholerae (5,17,22). These mechanisms also include three phosphorylase genes [mph(A), mph(B), and mph(D)] found in E. coli (14,15) and Pseudomonas (12) and one rRNA methylase gene [erm(B)] previously found in E. coli and Actinobacillus, Klebsiella, Neisseria, and Wolinella species (1, 4, 18-21). The strains described above were principally clinical isolates from hospital settings and/or from patients with clinical disease (17,18,20,21), with members of the family Enterobacteriaceae and Pseudomonas species primarily isolated from France and Japan

Section: Discussionmentioning

confidence: 99%

“…Isolates were initially screened by DNA-DNA hybridization of whole-cell dot blots and/or DNA dot blots as previously described (2-4, 6-9, 18). PCR was performed on selected isolates to confirm the presence of the various macrolide genes (3,4,8). Oligonucleotide probes for PCR and DNA-DNA hybridization are listed in Table 2.…”

mentioning

confidence: 99%

The mef (A) Gene Predominates among Seven Macrolide Resistance Genes Identified in Gram-Negative Strains Representing 13 Genera, Isolated from Healthy Portuguese Children

Ojo

Ulep

Kirk

et al. 2004

“…There is limited information describing the molecular bases of macrolide resis-tance in gonococci. Although macrolide resistance mediated by ribosomal methylation or mutations has been described, increased activity of the MtrCDE efflux pump is the most common mechanism responsible for the phenotype (8,11,12,34,43,53,55,60).…”

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confidence: 99%

Molecular Analysis of Antimicrobial Resistance Mechanisms in Neisseria gonorrhoeae Isolates from Ontario, Canada

Allen

Farrell

Rebbapragada

et al. 2011

Surveillance of gonococcal antimicrobial resistance and the molecular characterization of the mechanisms underlying these resistance phenotypes are essential in order to establish correct empirical therapies, as well as to describe the emergence of new mechanisms in local bacterial populations. To address these goals, 149 isolates were collected over a 1-month period (October-November 2008) at the Ontario Public Health Laboratory, Toronto, Canada, and susceptibility profiles (8 antibiotics) were examined. Mutations in previously identified targets or the presence of some enzymes related to resistance (r), nonsusceptibility (ns) (resistant plus intermediate categories), or reduced susceptibility (rs) to the antibiotics tested were also studied. A significant proportion of nonsusceptibility to penicillin (PEN) (89.2%), tetracycline (TET) (72.3%), ciprofloxacin (CIP) (29%), and macrolides (erythromycin [ERY] and azithromycin; 22.3%) was found in these strains. Multidrug resistance was observed in 18.8% of the collection. Although all the strains were susceptible to spectinomycin and extended-spectrum cephalosporins (ESC) (ceftriaxone and cefixime), 9.4% of them displayed reduced susceptibility to extended-spectrum cephalosporins. PBP 2 mosaic structures were found in all of these ESC rs isolates. Alterations in the mtrR promoter, MtrR repressor (TET r , PEN ns , ESC rs , and ERY ns ), porin PIB (TET r and PEN ns ), and ribosomal protein S10 (TET r ) and double mutations in gyrA and parC quinolone resistance-determining regions (QRDRs) (CIP r ) were associated with and presumably responsible for the resistance phenotypes observed. This is the first description of ESC rs in Canada. The detection of this phenotype indicates a change in the epidemiology of this resistance and highlights the importance of continued surveillance to preserve the last antimicrobial options available.

“…However, the erythromycin MICs for the two mef(I)-positive isolates (16 g/ml) were in the high MIC range (2 to 16 g/ml) for the mef-positive isolates examined in this study. Remarkably, evidence is emerging that the mef gene, far from being confined to streptococci, can be associated with a wide range of gram-positive and gramnegative bacteria (8,20,21,43). Whether the mef gene is close to an msr gene has not generally been investigated in these organisms, but, at least in Bacteroides strains, an msr gene has been found adjacent to mef (43).…”

Section: Tet(l) Tet(m) and Tet(o)mentioning

confidence: 99%

Molecular Characterization of Pneumococci with Efflux-Mediated Erythromycin Resistance and Identification of a Novel mef Gene Subclass, mef (I)

Cochetti

Vecchi

Mingoia

et al. 2005

The molecular genetics of macrolide resistance were analyzed in 49 clinical pneumococci (including an "atypical" bile-insoluble strain currently assigned to the new species Streptococcus pseudopneumoniae) with efflux-mediated erythromycin resistance (M phenotype). All test strains had the mef gene, identified as mef(A) in 30 isolates and mef(E) in 19 isolates (including the S. pseudopneumoniae strain) on the basis of PCRrestriction fragment length polymorphism analysis. Twenty-eight of the 30 mef(A) isolates shared a pulsed-field gel electrophoresis (PFGE) type corresponding to the England 14 -9 clone. Of those isolates, 27 (20 belonging to serotype 14) yielded multilocus sequence type ST9, and one isolate yielded a new sequence type. The remaining two mef(A) isolates had different PFGE types and yielded an ST9 type and a new sequence type. Far greater heterogeneity was displayed by the 19 mef(E) isolates, which fell into 11 PFGE types, 12 serotypes (though not serotype 14), and 12 sequence types (including two new ones and an undetermined type for the S. pseudopneumoniae strain). In all mef(A) pneumococci, the mef element was a regular Tn1207.1 transposon, whereas of the mef(E) isolates, 17 carried the mega element and 2 exhibited a previously unreported organization, with no PCR evidence of the other open reading frames of mega. The mef gene of these two isolates, which did not match with the mef(E) gene of the mega element (93.6% homology) and which exhibited comparable homology (91.4%) to the mef(A) gene of the Tn1207.1 transposon, was identified as a novel mef gene variant and was designated mef(I). While penicillin-nonsusceptible isolates (three resistant isolates and one intermediate isolate) were all mef(E) strains, tetracycline resistance was also detected in three mef(A) isolates, due to the tet(M) gene carried by a Tn916-like transposon. A similar mechanism accounted for resistance in four of the five tetracyclineresistant isolates carrying mef(E), in three of which mega was inserted in the Tn916-like transposon, giving rise to the composite element Tn2009. In the fifth mef(E)-positive tetracycline-resistant isolate (the S. pseudopneumoniae strain), tetracycline resistance was due to the presence of the tet(O) gene, apparently unlinked to mef(E).