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Macrolide Resistance Doubles In Five Years
A DGReview of :"Macrolide Resistance Among Invasive Streptococcus pneumoniae Isolates"
Journal of the American Medical Association (JAMA)
10/17/2001
By Elda Hauschildt
Prevalence of macrolide resistance among pneumococci doubled in the United States between 1995 and 1999. M phenotype erythromycin-resistant isolates account for the increase.
"Macrolide resistance is now common in the US among invasive pneumococci," say investigators with the US Active Bacterial Core Surveillance/Emerging Infections Program Network. Members represent 11 different academic and governmental research groups.
"Macrolides are important therapeutic agents," they say. "Clinical treatment guidelines for empiric therapy for community-acquired pneumonia in adults have recommended using macrolides as first-line agents.
"Increasing frequency of macrolide resistance among pneumococci and increasing minimum inhibitory concentrations (MICs) among resistant strains suggest that these treatment recommendations may need re-evaluation."
Researchers analysed 15,481 invasive isolates collected in eight states by the US Centres for Disease Control and Prevention, Atlanta, Georgia.
"From 1993 to 1999, macrolide use increased 13 percent," they report. "Macrolide use increased 320 percent among children younger than five years.
"Macrolide resistance increased to 20.4 percent in 1999 from 10.6 percent in 1995.
"M phenotype isolates increased to 16.5 percent from 7.4 percent, while the proportion with MLSb phenotype was stable (3 percent to 4 percent)."
They also state: "Although M phenotype isolates were previously thought to be less concerning because of low erythromycin MICs, in our sample they had increasingly higher erythromycin MICs and were often resistant to other antibiotic agents."
The investigators suggest the M phenotype has likely become the dominant resistance mechanism "due to a combination of successful spread of clones within the paediatric population in the US and selective pressure of macrolide use in this population."
While the M phenotype is predominant in North America, several European countries report dominance of the MLSb phenotype, they add.
Differences in types of antibiotic used and prevalence of resistant clones probably account for the difference.
JAMA, 2001; 286: 1857-1862.
"Macrolide Resistance Among Invasive Streptococcus pneumoniae Isolates"
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