Evolution of Staphylococcus aureus resistance to erythromycin in Denmark, 1959 to 1988: correlations between characteristics of erythromycin-resistant bacteraemia strains.
In an attempt to characterize erythromycin-resistant Staphylococcus aureus we present the intricate relationships between the following factors: phage type, period of isolation, antibiogram, minimum inhibitory concentration (MIC) to erythromycin, inducible or constitutive resistance, spectinomycin susceptibility, hospital- or community-acquired infection, and mortality rate. We studied 718 cases of bacteraemia with erythromycin-resistant S. aureus, occurring between 1959 and 1988. Central factors were phage type pattern, period of isolation, and antibiogram. Between 1959 and 1973 the majority of the erythromycin-resistant strains were multiresistant and belonged to the 83A complex and the related group III. They were mainly inducibly resistant, spectinomycin resistant, and had intermediate MICs (1-4 mg l-1) to erythromycin. The majority of these strains came from hospital-acquired infections and still exist today, although in decreased numbers. By contrast, erythromycin-resistant S. aureus isolated in recent years are usually co-resistant only to penicillin and more rarely also to tetracycline. These strains have inducible resistance, are spectinomycin susceptible, and have a high erythromycin MIC. They are isolated both from hospital- and community-acquired infections. Strains with constitutive resistance to macrolides occurred at a stable low level (13%) during the whole observation period and always had high MICs to erythromycin. The mortality rate among patients with S. aureus bacteraemia due to an erythromycin-resistant strain was only associated with the year of infection and decreased from 61% in the first 15-year period to 40% in the subsequent 15 years.
Department of Diagnostic Microbiology and Antibiotics, Statens Seruminstitut, Copenhagen, Denmark.
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H
Westh
A M
AM
Knudsen
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A
Gottschau
V T
VT
Rosdahl
D001434:Bacteriophage Typing / Q000379:methods; D003428:Cross Infection / Q000382:microbiology / Q000401:mortality; D003718:Denmark; D004352:Drug Resistance, Microbial; D004917:Erythromycin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008954:Models, Biological; D010641:Phenotype; D018805:Sepsis / Q000382:microbiology; D013045:Species Specificity; D000198:Spectinomycin / Q000627:therapeutic use*; D013203:Staphylococcal Infections / Q000382:microbiology / Q000401:mortality; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects*; D013997:Time Factors
D004917:Erythromycin; D000198:Spectinomycin