Three familial cases of drug-resistant Mycoplasma pneumoniae infection.

UNLABELLED: Mycoplasma pneumoniae infection is believed to result from defective host immune response rather than from direct cell injury by the organism itself. In this context, emergence of drug-resistant M. pneumoniae may provide us with special opportunities to study the pathogenesis from a clinical point of view. In this report, three patients with intrafamilial M. pneumoniae infection are presented. M. pneumoniae was isolated with a Hayflick pleuropneumonia-like organism diphasic medium. Minimal inhibitory concentrations of antibiotics were determined by a broth microdilution method. Polymerase chain reaction and restriction fragment length polymorphism analysis were done to determine point mutation in domain V of the 23S rRNA gene. As a result, all three strains from the three intrafamilial cases had the same drug-resistant point mutation, specifically A-to-G transition at position 2063. However, their clinical courses were quite different; a 6-year-old girl suffered severe pneumonia, a 5-year-old girl had mild pneumonia, and a 3-year-old boy had only a fever of 1-day duration without pneumonia.

CONCLUSIONS: Our clinical and laboratory observations strongly support the idea that the host immune maturity, rather than a virulence factor of the organism, is a major determinant factor of disease severity of M. pneumoniae infection and that drug resistance does not necessarily lead to a serious clinical outcome.