Household transmission of Streptococcus pneumoniae, Alberta, Canada.

Outbreaks of Streptococcus pneumoniae (antibiotic resistant and nonresistant) have been reported from child-care centers, nursing homes, hospitals, military camps, homeless shelters, and penal institutions (1-6). Simultaneous cases within households have rarely been reported (7-11); such cases require common exposure and transmission, as well as similar likelihood of disease in the hosts or increased virulence in the pathogen. In December 1996 and January 1997, three married couples with multidrug-resistant S. pneumoniae (MDRSP) were admitted to Foothills Medical Centre in Calgary. The couples were not admitted on the same day. None of the couples lived with children, although couple C had daily contact with children. All patients received appropriate antibiotic therapy after their culture and antibiotic sensitivity results were known. We reviewed each patient’s health record (Table) and were able to contact two of the three couples for further information. S. pneumoniae were identified by standard methods. MICs were determined by E-Test (AB Biodisk, Solna, Sweden) and classified as susceptible (S), intermediate resistant (I), or fully resistant (R) to each antibiotic, according to National Committee for Clinical Laboratory Standards guidelines (12). Serotyping of S. pneumoniae was performed by the Quellung reaction technique at the National Centre for Streptococcus, Edmonton. Electrophoretic fingerprinting of S. pneumoniae was performed by pulsed-field gel electrophoresis (PFGE) of DNA digested with Sma1 (BRL, Gaithersburg, MD). The PFGE patterns were classified as indistinguishable, related, or different according to criteria suggested by Tenover (13). The diagnosis of S. pneumoniae pneumonia in couple A was confirmed by positive blood cultures, chest X-ray lobar pneumonia, and disease-compatible clinical findings. Patient 1 in couple A was a health records clerk at Foothills Medical Centre. Her illness was complicated soon after admission by empyema, which was drained; the fluid was S. pneumoniae-negative. Vertebral osteomyelitis was suspected from clinical evidence 18 days after admission and was confirmed by bone scan; no diagnostic culture was obtained. Osteomyelitis in this patient was presumably caused by S. pneumoniae. The initial 7-day course of cefuroxime (to which S. pneumoniae was resistant) may not have cleared the infection and thus allowed secondary seeding to bone. Household Transmission of Streptococcus pneumoniae, Alberta, Canada