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Streptococcus zooepidemicus (Lancefield group C) septicaemia in Hong Kong
Insights
Streptococcus zooepidemicus causes severe infections, particularly linked to cardiovascular issues and high mortality. Hong Kong strains show distinct characteristics, with pigs identified as a potential infection source.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Medicine
Background:
- Streptococcus zooepidemicus is an emerging cause of human infections.
- Septicemia due to S. zooepidemicus can lead to severe complications and mortality.
- Understanding the clinical spectrum and microbial characteristics is crucial for effective management.
Purpose of the Study:
- To review clinical findings of Streptococcus zooepidemicus septicemia in Hong Kong.
- To identify associations with cardiovascular disease and other conditions.
- To characterize Hong Kong strains of S. zooepidemicus and compare them to previously reported biotypes.
Main Methods:
- Retrospective review of clinical data from 11 Hong Kong patients.
- Comparison with 43 previously reported cases.
- Microbiological characterization including aesculin hydrolysis, colony morphology, electron microscopy for capsules, and DNA fingerprinting (HindIII restriction endonuclease).
- Antimicrobial susceptibility testing (MIC and MBC for penicillin).
Main Results:
- A significant association with cardiovascular disease (27%), including endocarditis and aortic aneurysm.
- Previously unreported associations with pharyngitis and persistent post-operative fever.
- Overall mortality rate of 22%.
- Hong Kong strains were aesculin-negative, mucoid, with hyaluronic acid capsules, and identical DNA fingerprints to porcine strains.
- Penicillin MIC was very low (<=0.03 mg/l), but MBC was high (>32 mg/l).
Conclusions:
- Pigs are a likely source of human S. zooepidemicus infection in Hong Kong.
- Contaminated dairy products are a significant source elsewhere.
- Penicillin is effective, but combination therapy may be needed for severe cases.
- Distinct microbiological features of Hong Kong strains warrant further investigation.
Abstract:
The clinical findings relating to 11 patients in Hong Kong (HK) and to 43 patients described elsewhere, all with Streptococcus zooepidemicus septicaemia, are reviewed. There was a particular association with cardiovascular disease (27%) with seven cases of endocarditis, three of abdominal aortic aneurysm and two of deep venous thrombosis. Associations not previously reported included two cases of pharyngitis and two patients with persistent post-operative fever. The overall mortality was 22%. Both human and porcine strains of S. zooepidemicus from HK did not hydrolyse aesculin in contrast to the aesculin-positive biotypes reported previously. HK strains also had very mucoid colonies and capsules of hyaluronic acid were seen in electron micrographs. Samples of chromosomal DNA, extracted by means of HindIII restriction endonuclease, of strains from human beings and pigs were identical. The MIC of penicillin for all strains was less than or equal to 0.03 mg/l but the MBC for all was greater than 32 mg/l. Penicillin alone is generally sufficient for cure but combination with an aminoglycoside may be indicated in seriously ill patients. In our locality, pigs were incriminated as a possible source of human infection whereas consumption of contaminated dairy products is important elsewhere.