Related Experiment Videos
Changing trend in susceptibility pattern of Streptococcus pneumoniae to penicillin in India
M K Lalitha1, K Thomas, A Manoharan
1Department of Clinical Microbiology, Christian Medical College & Hospital, Vellore.
Abstract:
Prior to 1995 all strains of Streptococcus pneumoniae isolated at a tertiary care hospital in south India were uniformly susceptible to penicillin. However, since late 1995 strains of S. pneumoniae with intermediate resistance to penicillin have been observed. Altogether there were 25 such isolates, 9 from invasive (5 from CSF as well as blood, 1 from pleural fluid and 3 from CSF alone) and 16 from noninvasive sites (6 from throat, 6 from sputum, 3 from eye and 1 from ear) respectively, thus 4.6 per cent of S. pneumoniae showed intermediate resistance of a total of 535 strains studied so far. The minimum inhibitory concentration (MIC) values of penicillin, erythromycin, chloramphenicol and cefotaxime were determined by agar dilution method and for confirmation, E test was carried out for penicillin alone. The MIC range obtained for penicillin was between 0.125-1.0 microgram/ml. Kirby-Bauer disc diffusion method was adopted for testing of erythromycin, chloramphenicol, co-trimoxazole, cefotaxime, tetracycline and vancomycin. We observed that none of the strains with intermediate resistance to penicillin were multidrug resistant. These strains belonged predominantly to serotype 14 (n = 10), 7B (n = 9), 19A (n = 3), 7F (n = 2) and 23F (n = 1). Clonality was not observed in the 5 representative strains subjected to Box A finger printing method.
Insights
Since 1995, intermediate penicillin resistance in Streptococcus pneumoniae has emerged in South India. Most resistant strains were not multidrug-resistant and belonged to specific serotypes.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Penicillin susceptibility in Streptococcus pneumoniae was uniform in South India before 1995.
- Emergence of intermediate penicillin resistance in S. pneumoniae strains observed since late 1995.
- Intermediate resistance detected in 4.6% of 535 S. pneumoniae strains studied.
Purpose of the Study:
- To characterize Streptococcus pneumoniae strains exhibiting intermediate penicillin resistance.
- To determine antimicrobial susceptibility patterns of these resistant strains.
- To investigate the serotypes and clonality of penicillin-resistant S. pneumoniae.
Main Methods:
- Minimum inhibitory concentration (MIC) determination using agar dilution for penicillin, erythromycin, chloramphenicol, and cefotaxime.
- E test confirmation for penicillin MIC.
- Kirby-Bauer disc diffusion for erythromycin, chloramphenicol, co-trimoxazole, cefotaxime, tetracycline, and vancomycin.
- Box A fingerprinting for clonality assessment of representative strains.
Main Results:
- 25 isolates of S. pneumoniae showed intermediate resistance to penicillin (MIC range: 0.125-1.0 µg/ml).
- Resistant strains were isolated from both invasive and non-invasive sites.
- None of the intermediate penicillin-resistant strains were multidrug-resistant.
- Predominant serotypes included 14, 7B, 19A, 7F, and 23F.
- Box A fingerprinting did not reveal clonality in the tested strains.
Conclusions:
- Intermediate penicillin resistance in Streptococcus pneumoniae has emerged in South India.
- These resistant strains do not exhibit multidrug resistance and are associated with specific serotypes.
- Further surveillance is warranted to monitor the evolution of antimicrobial resistance in S. pneumoniae.