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Incidence, capsular types, and antibiotic susceptibility of invasive Streptococcus pneumoniae in Sweden
J Hedlund1, S B Svenson, M Kalin
1Swedish Institute for Infectious Disease Control, Stockholm.
Abstract:
The number of reported cases of invasive pneumococcal infections in Sweden increased more than threefold from 1988 through 1992. We studied the capsular types and the antibiotic susceptibility of 619 pneumococcal strains isolated from blood or CSF at 18 Swedish microbiological laboratories in 1987 and in 1992. These strains belonged to 35 of the 84 recognized capsular types. We noted a remarkable increase in the prevalence of invasive infections with type 14 from 1987 (8.2%) to 1992 (18%) (P = .001), which correspond to a sevenfold increase in absolute numbers. The most prominent increase in infections was seen among elderly people; in 1992, type 14 accounted for 22.5% of the isolates from infected persons who were >64 years of age. The majority of the strains were susceptible to all antibiotics tested. However, there was a significant increase in trimethoprim-sulfamethoxazole resistance from 1.4% in 1987 to 7.1% in 1992. Nine multiresistant isolates (1.5%) were found.
Insights
Invasive pneumococcal infections in Sweden significantly increased, particularly type 14, especially in the elderly. Antibiotic resistance, notably to trimethoprim-sulfamethoxazole, also rose.
Area of Science:
- Microbiology
- Infectious Diseases
- Epidemiology
Background:
- Reported cases of invasive pneumococcal infections in Sweden saw a threefold increase between 1988 and 1992.
- Streptococcus pneumoniae remains a significant cause of invasive bacterial infections globally.
Purpose of the Study:
- To investigate the changes in capsular types and antibiotic susceptibility of pneumococcal strains causing invasive infections in Sweden between 1987 and 1992.
- To identify specific serotypes and resistance patterns contributing to the rise in invasive pneumococcal disease.
Main Methods:
- Analysis of 619 pneumococcal isolates from blood or cerebrospinal fluid (CSF) collected from 18 Swedish laboratories in 1987 and 1992.
- Serotyping of isolates to determine capsular types and antimicrobial susceptibility testing against various antibiotics.
Main Results:
- A significant increase in invasive infections caused by pneumococcal type 14 was observed, rising from 8.2% in 1987 to 18% in 1992 (P = .001), representing a sevenfold increase in absolute numbers.
- Invasive pneumococcal infections disproportionately affected the elderly, with type 14 accounting for 22.5% of isolates in individuals over 64 years old in 1992.
- While most strains remained susceptible to antibiotics, a significant rise in trimethoprim-sulfamethoxazole resistance was noted, increasing from 1.4% in 1987 to 7.1% in 1992. Nine multiresistant isolates (1.5%) were identified.
Conclusions:
- Pneumococcal type 14 emerged as a major driver of the increased invasive pneumococcal disease in Sweden during the study period, particularly in the elderly population.
- The rising resistance to trimethoprim-sulfamethoxazole is a concerning trend that warrants monitoring and may impact treatment strategies.
- Continued surveillance of pneumococcal epidemiology and antibiotic resistance is crucial for public health interventions.