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Bactericidal activity of human serum against strains of Klebsiella from different sources
1Public Health Laboratory, Central Middlesex Hospital, London.
Abstract:
One hundred and eighty strains of Klebsiella were tested for sensitivity to pooled normal human serum, capsular type and faecal coliform reaction. Strains of K. pneumoniae isolated from clinical infections were more likely to be serum resistant than those from the gut flora or environmental sources. For K. oxytoca strains, there was no significant correlation between serum sensitivity and source of isolation. Of 60 strains of K. oxytoca tested, 19 (32%) were serum resistant, as were 27 (23%) of 120 strains of K. pneumoniae. Strains of K. pneumoniae from human sources gave positive reactions in the faecal coliform test more frequently than strains from environmental sources. There was no correlation between a positive faecal coliform reaction and resistance to the bactericidal effect of human serum. Strains of capsular type K21 were isolated more frequently from clinical infections and were more often serum resistant than other strains. Serum resistance appears to be a virulence factor in strains of K. pneumoniae but does not account for the difference in pathogenicity between K. pneumoniae and K. oxytoca.
Insights
Klebsiella pneumoniae strains from infections show higher serum resistance, a potential virulence factor. However, serum resistance doesn't explain pathogenicity differences between K. pneumoniae and K. oxytoca.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Klebsiella species are opportunistic pathogens.
- Understanding bacterial resistance mechanisms is crucial for infection control.
- Serum resistance is a known virulence factor in some bacteria.
Purpose of the Study:
- To investigate the relationship between serum sensitivity, source, and capsular type in Klebsiella pneumoniae and Klebsiella oxytoca.
- To determine if serum resistance contributes to the pathogenicity of K. pneumoniae.
Main Methods:
- Testing 180 Klebsiella strains for sensitivity to pooled normal human serum.
- Analyzing strains based on source (clinical, gut flora, environmental) and capsular type.
- Performing faecal coliform tests on isolates.
Main Results:
- Klebsiella pneumoniae from clinical infections were more serum resistant than environmental or gut flora isolates.
- 23% of K. pneumoniae and 32% of K. oxytoca strains were serum resistant.
- K. pneumoniae from human sources were more likely to be faecal coliform positive.
- No correlation was found between faecal coliform reaction and serum resistance.
- Capsular type K21 strains were more frequent in clinical infections and more serum resistant.
Conclusions:
- Serum resistance is a virulence factor in Klebsiella pneumoniae.
- Serum resistance does not fully explain the difference in pathogenicity between K. pneumoniae and K. oxytoca.