ArticleBysjö E, Dornbusch K.
Scand J Infect Dis. 1977;9(4):293-6.
A 1-year-old boy with recurrent otitis media had been repeatedly treated with antibiotics. A few days after withdrawal of administered ampicillin he again contracted otitis media and ampicillin-resistant Haemophilus influenzae was isolated. The strain was serologically untypable. No ampicillin-resistant H. influenzae was found in his family or at the day-care centre that he attended. The ability to produce the beta-lactamase elaborated from this strain could be transferred to ampicillin-sensitive strains of H. influenzae and Escherichia coli in frequencies of 0.7 X 10(-7) and 4.1 X 10(-4) respectively. The transcipients obtained were ampicillin-resistant and beta-lactamase producing. In the transcipients of E. coli, however, the marker for ampicillin resistance was quite unstable.