Serogroup 19 pneumococci containing both mef and erm macrolide resistance determinants in an American city.
BACKGROUND
Asia has experienced a striking incidence of infection by highly resistant pneumococi containing both principal macrolide resistance determinants, namely, the mef efflux pump and the erm ribosomal methylase. mef/erm-containing pneumococci have not been identified in significant numbers in North America.


METHODS
Pneumococci were isolated as part of a larger study in Cleveland, OH examining colonization patterns among children randomized to 1 of 4 outpatient antibiotics for acute otitis media. Azithromycin-resistant organisms were tested for the presence of mef and erm sequences by polymerase chain reaction. The clonal relationship of pneumococci containing both genes was determined by pulsed field gel electrophoresis and multilocus sequence testing. Selected characteristics of children harboring mef/erm-containing organisms were compared with other participants of the larger study.


RESULTS
Of 221 children colonized by pneumococci, 17 (7.7%) were colonized with an organism containing both determinants. All mef/erm-positive organisms demonstrated azithromycin minimum inhibitory concentrations > or =256 microg/mL and were coresistant to all other agents tested. The mef/erm-containing organisms were serotype 19A and 19F, all but 1 of which manifested similar pulsed field gel electrophoresis patterns. Multilocus sequence testing analysis indicated a relationship to the Taiwan-14 macrolide-resistant strain that has spread throughout Eastern Asia. More than one-third of children colonized by a mef/erm-containing organism had received > or =1 dose of conjugate pneumococcal vaccine, a significantly higher proportion than children carrying less resistant organisms (P< 0.01). No other characteristics distinguished children harboring a mef/erm-containing pneumococcus from other children enrolled in the larger study.


CONCLUSIONS
Clonally related mef/erm-containing serogroup 19 pneumococci were prominent among otherwise healthy children in a North American metropolitan area. Our findings suggest that spread of these organisms may be poorly contained by immunization.
Toltzis
Philip
P
Department of Pediatrics, Rainbow Babies and Children's Hospital, University Hospitals of Cleveland, Case Western Reserve University School of Medicine, Cleveland, OH, USA. pxt2@case.edu
Dul
Michael
M
O'Riordan
Mary Ann
MA
Jacobs
Michael R
MR
Blumer
Jeffrey
J
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017963:Azithromycin / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial; D006801:Humans; D007223:Infant; D008565:Membrane Proteins / Q000235:genetics*; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D009820:Ohio; D010033:Otitis Media / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C117866:MefA protein, Streptococcus; D008565:Membrane Proteins; D017963:Azithromycin; C111078:ErmTR protein, bacteria; D008780:Methyltransferases