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Susceptibility of Streptococcus pneumoniae to penicillin: a prospective microbiological and clinical study
M E García-Leoni1, E Cercenado, P Rodeño
1Servicio de Microbiología Clínica, Hospital General Gregorio Marañón, Madrid, Spain.
Abstract:
We performed a prospective study of all infections with Streptococcus pneumoniae documented during a 22-month period at our hospital. A total of 163 clinically significant strains of S. pneumoniae were isolated from 139 patients whose ages ranged from 8 days to 91 years (mean +/- SD, 42.6 years +/- 26.8 years). Twenty percent of the patients had cancer, and 18% were infected with the human immunodeficiency virus. Pneumococcal infection was nosocomially acquired in one-fourth of cases. One-third of patients had nonpneumonic disease. A wide range of serotypes were isolated, and 42.5% of all strains were nonsusceptible--i.e., showed either intermediate or high-level resistance--to penicillin. The rates of resistance to chloramphenicol, erythromycin, and tetracycline were 23%, 10.8%, and 48.2%, respectively. Twenty-two percent of the infected patients died, with a 15.8% mortality directly attributable to pneumococcal infection. Factors associated with infection by strains of S. pneumoniae not susceptible to penicillin included an age of less than or equal to 10 years, immunosuppression, the presence of a rapidly fatal underlying disease, previous antimicrobial therapy, and infection by serotypes 14 and 23. All clinically significant isolates of S. pneumoniae should be submitted for antimicrobial susceptibility studies, and, whenever a high prevalence of resistance to penicillin and macrolides is detected, the use of these well-established empirical therapeutic regimens should be reconsidered.
Insights
High rates of penicillin resistance in Streptococcus pneumoniae infections were observed, particularly in young, immunocompromised patients. This highlights the need for antimicrobial susceptibility testing and reconsideration of empirical treatment.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Medicine
Background:
- Streptococcus pneumoniae is a significant cause of morbidity and mortality.
- Antimicrobial resistance in S. pneumoniae poses a growing public health threat.
- Understanding resistance patterns is crucial for effective treatment strategies.
Purpose of the Study:
- To prospectively investigate the characteristics and antimicrobial susceptibility of Streptococcus pneumoniae infections.
- To identify factors associated with penicillin-nonsusceptible S. pneumoniae (PNSP) infections.
- To evaluate the impact of PNSP on patient outcomes.
Main Methods:
- Prospective study over 22 months.
- Isolation and characterization of 163 clinically significant S. pneumoniae strains from 139 patients.
- Antimicrobial susceptibility testing for penicillin, chloramphenicol, erythromycin, and tetracycline.
- Analysis of patient demographics, clinical data, and outcomes.
Main Results:
- 42.5% of S. pneumoniae strains were nonsusceptible to penicillin.
- High resistance rates observed for tetracycline (48.2%) and chloramphenicol (23%).
- Mortality rate was 22%, with 15.8% directly attributable to pneumococcal infection.
- Factors associated with PNSP included young age (≤10 years), immunosuppression, and underlying fatal diseases.
Conclusions:
- A significant proportion of S. pneumoniae infections exhibit resistance to commonly used antibiotics, especially penicillin.
- Antimicrobial susceptibility testing is essential for all clinically significant S. pneumoniae isolates.
- Empirical treatment guidelines may need revision in areas with high resistance prevalence.