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An outbreak of penicillin resistant Streptococcus pneumoniae investigated by a polymerase chain reaction based
S H Gillespie1, T D McHugh, J E Hughes
1Department of Medical Microbiology, Royal Free Hospital School of Medicine, London, UK.
Aims:
To characterise the genotypes of penicillin resistant Streptococcus pneumoniae infecting patients in a care of the elderly ward and to study its transmission in a hospital environment.
Methods:
Isolates of S pneumoniae were cultured from specimens obtained from patients who had been admitted to a care of the elderly ward where an outbreak had occurred. Penicillin resistant S pneumoniae were also obtained from a series of surveillance throat swabs taken from patients in the same ward. In addition, all penicillin resistant S pneumoniae isolated from specimens submitted for culture at the time of the outbreak were included. Four sensitive strains isolated from a routine microbiology laboratory were included as controls. A simple polymerase chain reaction (PCR) based genotyping method for the penicillin binding protein (PBP) genes 1a, 2x, and 2b was used to characterise the genotypes.
Results:
Nine patients were infected with serotype 9 S pneumoniae. Four of these patients died; two deaths were directly attributable to the infection. Tested against a battery of haemolytic streptococci and other organisms found in the respiratory tract, only two false positive reactions for PBP 2x were found among S mitis. The method demonstrated that the outbreak strain had altered PBP 1a, 2b, and 2x genes, a pattern clearly distinguishable from other penicillin resistant strains isolated at the same time.
Conclusions:
This method is simple to perform and would enable many laboratories to characterise the genotype of penicillin resistant S pneumoniae and investigate transmission in their hospitals.
Insights
A simple polymerase chain reaction (PCR) genotyping method identified the specific genetic changes in penicillin-resistant Streptococcus pneumoniae during a hospital outbreak. This technique aids in tracking the transmission of resistant bacteria in healthcare settings.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Penicillin-resistant Streptococcus pneumoniae (PRSP) poses a significant threat in healthcare settings, particularly in vulnerable populations like the elderly.
- Understanding the genetic basis of penicillin resistance and bacterial transmission is crucial for effective infection control.
Purpose of the Study:
- To genotype penicillin-resistant Streptococcus pneumoniae isolates from a care of the elderly ward outbreak.
- To investigate the transmission dynamics of PRSP within a hospital environment.
Main Methods:
- Isolates were collected from patients during an outbreak and from surveillance throat swabs.
- A simple polymerase chain reaction (PCR)-based genotyping method targeting penicillin-binding protein (PBP) genes (1a, 2x, 2b) was employed.
- Sensitive strains were used as controls.
Main Results:
- Nine patients were infected with serotype 9 S. pneumoniae, leading to four deaths.
- The outbreak strain exhibited distinct alterations in PBP 1a, 2b, and 2x genes, differentiating it from other co-circulating PRSP strains.
- The PCR method showed high specificity, with minimal false positives.
Conclusions:
- The developed PCR genotyping method is simple and effective for characterizing PRSP.
- This technique facilitates the investigation of bacterial transmission within hospital settings.
- It empowers laboratories to enhance their infection control strategies against resistant pathogens.