Original article Clinical aspects and cost of invasive Streptococcus pneumoniae infections in children: resistant vs. susceptible strains Caroline Quach a,b , Karl Weiss a, *, Dorothy Moore b , Earl Rubin b , Allison McGeer c , Donald E. Low c a Department of Microbiology and Infectious Disease, Maisonneuve-Rosemont Hospital, University of Montreal, 5415 l’Assomption, Montreal, Que., Canada H1T 2M4 b Division of Infectious Disease, Department of Pediatrics, The Montreal Children’s Hospital, McGill University, Montreal, Que., Canada c Mount Sinai Hospital, University of Toronto, Toronto, Ont., Canada Abstract Invasive Streptococcus pneumoniae infections in children are associated with serious consequences in terms of morbidity and mortality. The main objective of the study was to determine if invasive infections caused by penicillin-resistant Streptococcus pneumoniae (PRSP) differed in clinical presentation, outcome, risk factors, or cost from those caused by penicillin-susceptible strains (PSSP) in children. All patients aged 18 or less with invasive Streptococcus pneumoniae infections admitted to two teaching hospitals in Montreal between 1989 and 1998 were included in the study. We present a case  /control study in which for each index case of PRSP, 3 controls with PSSP infections were matched for age, sex, and site of infection. One hundred and forty-four patients were included in the analysis (36 cases, 108 controls). There was no difference between the two groups in terms of initial clinical presentation (vital signs, laboratory results) or total length of stay. Mortality was 2.7% in both groups. Hospital antibiotic cost was higher in the PRSP group (211 Canadian dollars (CAD) vs. 74 CAD; P /0.02). Antibiotic consumption in the preceding month was significantly associated with PRSP infection. Underlying diseases or day-care attendance were not shown to be significant risk factors for acquiring invasive PRSP infection. There were no differences between invasive infections caused by PRSP and PSSP in terms of clinical presentation, morbidity or mortality in a paediatric population. # 2002 Elsevier Science B.V. and International Society of Chemotherapy. All rights reserved. Keywords: Streptococcus pneumoniae ; Penicillin resistance; Meningitis; Bacteraemia 1. Introduction Streptococcus pneumoniae is a major cause of pneu- monia as well as the leading cause of bacterial meningi- tis, bacteraemia and otitis media in children [1]. Serious invasive infections occur more commonly in children younger than 2 years of age and may have important consequences in terms of morbidity and mortality [2]. The increasing prevalence of penicillin-resistant strains of S. pneumoniae worldwide is of growing concern. Increased cost of therapeutic alternatives to penicillin need to be evaluated, as does the question of morbidity associated with the emergence of resistance. Some studies have reported that the clinical presentation and outcome of infections caused by penicillin-resistant Streptococcus pneumoniae (PRSP) and penicillin-sensi- tive (PSSP) strains of S. pneumoniae were similar [3  /11]. The cost of PRSP invasive infections has not been previously evaluated in children. A retrospective matched case  /control study was undertaken to determine if invasive infections caused by PRSP or PSSP in children differed in risk factors, clinical presentation, costs of treatment or outcome. 2. Material and methods 2.1. Patient selection All patients aged 18 years or less who presented to the emergency room or who were admitted to one of two * Corresponding author. Tel.:  /1-514-252-3817; fax:  /1-514-252- 3898 E-mail addresses: weisscan@aol.com, kweiss.hmr@ssss.gouv.qc.ca (K. Weiss). International Journal of Antimicrobial Agents 20 (2002) 113  /118 www.isochem.org 0924-8579/02/$ - see front matter # 2002 Elsevier Science B.V. and International Society of Chemotherapy. All rights reserved. PII:S0924-8579(02)00127-9