title: Three familial cases of drug-resistant Mycoplasma pneumoniae infection.
abstract: 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.
authors.affiliation: Department of Pediatrics, Kamiamakusa General Hospital, 1419-19, Takado, Ryugatake, Kamiamakusa, Kumamoto 866-0202, Japan. kittysk885@yahoo.co.jp
authors.forename: Shintaro
authors.initials: S
authors.lastname: Kamizono
authors.forename: Hitomi
authors.initials: H
authors.lastname: Ohya
authors.forename: Sadanobu
authors.initials: S
authors.lastname: Higuchi
authors.forename: Norio
authors.initials: N
authors.lastname: Okazaki
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Narita
mesh_terms: D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004198:Disease Susceptibility; D024881:Drug Resistance, Bacterial / Q000276:immunology*; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D007564:Japan; D008297:Male; D011019:Pneumonia, Mycoplasma / Q000188:drug therapy / Q000276:immunology*; D035781:Siblings