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Streptococcus mitis. A cause of serious infection in adults
Abstract:
Twenty strains of Streptococcus mitis were isolated from blood or body fluids at the Cleveland Veterans Administration Medical Center from Jan 1, 1981, to April 30, 1984. Fifteen (75%) isolates were considered contaminants. Five (25%) were clinically important and associated with a serious infection of the oropharynx or gastrointestinal tract (three of five), endovascular system (one of five), or a prosthetic hip. Four of five patients required surgical intervention for treatment. Two of five died; one death was directly attributable to S mitis infection. Eighteen strains were available for detailed bacteriologic study. Three strains had a minimum inhibitory concentration of greater than 0.1 micrograms/mL of penicillin and six other strains were tolerant to penicillin. This review suggests that S mitis can be an important pathogen in adults and may cause infections other than endocarditis.
Insights
Streptococcus mitis can cause serious infections in adults, not just endocarditis. This bacterium, often a contaminant, can lead to severe outcomes requiring intervention and potentially causing death.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Clinical Bacteriology
Background:
- Streptococcus mitis is a common bacterium found in the human oropharynx.
- Its role as a pathogen, particularly in non-endocarditis infections, is often underestimated.
- Distinguishing between contaminants and true pathogens is crucial for appropriate patient management.
Purpose of the Study:
- To investigate the clinical significance of Streptococcus mitis isolates from a tertiary care setting.
- To characterize the bacteriologic properties of S. mitis strains associated with serious infections.
- To assess the spectrum of infections caused by S. mitis in adult patients.
Main Methods:
- Retrospective analysis of S. mitis isolates from blood or body fluids collected between 1981 and 1984.
- Clinical data review to determine the significance of each isolate (contaminant vs. pathogen).
- Bacteriologic studies, including penicillin minimum inhibitory concentration (MIC) and tolerance testing, on selected strains.
Main Results:
- Of 20 S. mitis isolates, 15 (75%) were contaminants, while 5 (25%) were clinically significant.
- Clinically important isolates were associated with oropharyngeal/gastrointestinal infections (3), endovascular infections (1), and prosthetic hip infection (1).
- Four of five patients with significant infections required surgery; two died, one directly due to S. mitis.
Conclusions:
- Streptococcus mitis can act as a significant pathogen in adults, causing severe infections beyond endocarditis.
- Penicillin resistance and tolerance were observed in some S. mitis strains, highlighting potential therapeutic challenges.
- Increased awareness and careful evaluation of S. mitis isolates are necessary for accurate diagnosis and treatment.