High clonal diversity in erythromycin-resistant Streptococcus pneumoniae invasive isolates in Madrid, Spain (2000–07)

Objectives Erythromycin resistance in Streptococcus pneumoniae is still increasing worldwide. All 78 erythromycin-resistant S. pneumoniae isolates collected from blood cultures in our hospital (2000–07) were studied and the population structure was analysed by using different mathematical diversity...

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Published in:	Journal of antimicrobial chemotherapy 2009-12, Vol.64 (6), p.1165-1169
Main Authors:	de la Pedrosa, Elia Gómez G., Baquero, Fernando, Loza, Elena, Nadal-Serrano, José-María, Fenoll, Asunción, del Campo, Rosa, Cantón, Rafael
Format:	Article
Language:	eng
Subjects:	Adult Anti-Bacterial Agents - pharmacology Antibiotics Bacteremia - epidemiology Bacteremia - microbiology Bacterial Proteins - genetics Bacterial Typing Techniques Blood clonal diversity indexes Cluster Analysis DNA Fingerprinting DNA, Bacterial - genetics Drug resistance Drug Resistance, Bacterial Erythromycin - pharmacology Genetic diversity Genetic Variation Hospitals Humans macrolide resistance Medical research Membrane Proteins - genetics Methyltransferases - genetics Molecular Epidemiology pneumococcal blood isolates Pneumococcal Infections - epidemiology Pneumococcal Infections - microbiology Polymerase Chain Reaction - methods Spain - epidemiology Streptococcus infections Streptococcus pneumoniae - classification Streptococcus pneumoniae - drug effects Streptococcus pneumoniae - isolation & purification Young Adult
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Summary:	Objectives Erythromycin resistance in Streptococcus pneumoniae is still increasing worldwide. All 78 erythromycin-resistant S. pneumoniae isolates collected from blood cultures in our hospital (2000–07) were studied and the population structure was analysed by using different mathematical diversity indexes. Methods Erythromycin resistance determinants were screened by PCR. The population structure, including multilocus sequence typing, was analysed by using quantitative clonal diversity (diversity ratio, Simpson, Selander–Levin and Shannon mathematical indexes). Results The leading resistance gene was erm(B) (74.3% of the isolates), followed by the erm(B) plus mef(A) combination (17.9%) and mef(A) alone (7.7%). The most frequent serotypes were 14 (18%), 19A (15.4%) and 6B (11.5%). A polyclonal structure was detected in resistant strains, including the Spain9V-3, Spain6B-2 and Denmark14-32 international clones. Both genetic diversity and genetic distribution were high, particularly among clones containing erm(B) and erm(B) plus mef(A) determinants. Conclusions The resistance determinants erm(B) and the combination of erm(B) plus mef(A) were observed within multiple S. pneumoniae bacteraemic clones. The preservation of a polyclonal structure might provide a suitable background for further evolution of antibiotic resistance.
ISSN:	0305-7453 1460-2091