Related Experiment Video
Updated: Jun 25, 2026
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Study of dihydropteroate synthase (DHPS) gene mutations among isolates of Pneumocystis jiroveci
A K Tyagi1, B R Mirdha, Randeep Guleria
1Department of Microbiology, All India Institute of Medical Sciences New Delhi, India.
Background & Objectives:
Pneumocystis jiroveci (also known as P. carinii) causes fatal pneumonia in patients with AIDS and other immunocompromised patients. Co-trimoxazole (trimethoprim + sulphamethoxazole, TMP-SMZ) is the drug of choice for treatment and prophylaxis. Widespread use of sulpha medication has raised the possible selection of resistant P. jiroveci strains worldwide. Non-synonymous polymorphisms associated with sulpha resistance have been observed in P. jiroveci dihydropteroate synthase (DHPS) gene at codons 55 and 57. In view of this, we investigated mutation at DHPS locus amongst P. jiroveci isolates obtained at a tertiary care hospital in north India.
Methods:
Microscopic examination of P. jiroveci in 69 clinical samples obtained from patients suspected to have P. carinii pneumonia (PCP), was performed by Grocott's Gomori methenamine silver and direct fluorescent antibody staining. Molecular studies were carried out by polymerase chain reaction (PCR) using major surface glycoprotein (MSG) as the target gene. Investigations for DHPS mutations were carried at specific 55th and 57th codon using PCR-RFLP (restriction fragment length polymorphism) assay.
Results:
Microscopic examination detected P. jiroveci in four cases and MSG gene was amplified in five cases. Further, amplification of DHPS gene was successful in four of the five cases positive by MSG gene PCR. No point mutation was observed and all four isolates presented wild-type sequences at DHPS gene by RFLP analysis.
Interpretation & Conclusion:
Although our findings suggest that in Indian subpopulation, point mutations in DHPS gene of P. jiroveci are not as common as in other parts of the developed world, further studies are needed.
Insights
Pneumocystis jiroveci pneumonia (PCP) is a serious infection in immunocompromised patients. This study found no sulfa drug resistance mutations in the DHPS gene of P. jiroveci isolates in North India, suggesting lower resistance prevalence.
Area of Science:
- Medical Mycology
- Molecular Epidemiology
- Antimicrobial Resistance
Background:
- Pneumocystis jiroveci pneumonia (PCP) is a life-threatening opportunistic infection.
- Co-trimoxazole (TMP-SMZ) is the primary treatment and prophylactic agent for PCP.
- Increasing sulfa drug use raises concerns about P. jiroveci resistance, potentially linked to DHPS gene mutations.
Purpose of the Study:
- To investigate the prevalence of dihydropteroate synthase (DHPS) gene mutations in P. jiroveci isolates from North India.
- To assess potential sulfa drug resistance in P. jiroveci strains within this population.
Main Methods:
- Clinical samples from suspected PCP patients were analyzed using microscopy and direct fluorescent antibody staining.
- Polymerase chain reaction (PCR) was employed to amplify the major surface glycoprotein (MSG) and DHPS genes.
- PCR-RFLP was used to detect specific mutations at codons 55 and 57 of the DHPS gene.
Main Results:
- P. jiroveci was detected in 4 of 69 samples via microscopy.
- The DHPS gene was successfully amplified in 4 isolates.
- No point mutations were identified in the DHPS gene; all isolates exhibited wild-type sequences.
Conclusions:
- The study suggests a lower prevalence of DHPS gene mutations associated with sulfa resistance in Indian P. jiroveci isolates compared to other regions.
- Further research is warranted to confirm these findings and understand the broader implications for PCP treatment in India.
Related Concept Videos
01:29Pneumonia II: Pathophysiology
01:05Single Nucleotide Polymorphisms-SNPs
01:18Mutations in Microorganisms
01:23Cystic Fibrosis: Pathogenesis
CF is primarily caused by a genetic mutation in a chromosome 7 gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The most common gene mutation leading to CF is the ΔF508 mutation, but...