Prevalence Of Dihydropteroate Synthase Mutations Research Articles

Clinical characteristics and prevalence of dihydropteroate synthase gene mutations in Pneumocystis jirovecii-infected AIDS patients from low endemic areas of China.

Pneumocystis pneumonia (PCP) is an opportunistic and potentially life-threatening infection of AIDS patients caused by the fungus Pneumocystis jirovecii (P. jirovecii). Trimethoprim-sulfamethoxazole (TMP-SMX) is the most commonly used drug combination in the treatment and prophylaxis of PCP. However, with long-term use of this combination, mutations in the dihydropteroate synthase (DHPS) gene of P. jirovecii bring about the development of resistance. Data on the prevalence of P. jirovecii and its DHPS mutants in China, especially in low endemic areas, are still limited. Thus, in the present study, we measured the P. jirovecii infection rate among HIV-positive and AIDS (HIV/AIDS) patients with suspected PCP and investigated the relationship between CD4+ T cell count and PCP occurrence. As well as the polymerase chain reaction (PCR) analysis and sequencing, the restriction fragment length polymorphism (RFLP) method was used to analyze DHPS point mutation in P. jirovecii strains. P. jirovecii was detected in 40.82% of cases. The clinical symptoms and signs of PCP were not typical; with decreasing CD4+ T cell counts, PCP infection in HIV/AIDS patients increased. In only one case (1.67%), the patients’ DHPS gene could not be cut by the Acc I restriction enzyme. Furthermore, mutation at codon 171 was detected in 11 cases and no mutation was found at codon 57. Patients treated with sulfamethoxazole combined with Voriconazole or Caspofungin exhibited favorable results. After treatment, the symptoms of dyspnea were alleviated, and chest computed tomography findings showed the improvement of lung shadows. These indicated that the prevalence of DHPS mutations in P. jirovecii isolates in AIDS-PCP patients in the region was low. Thus, the contribution of gene mutations to treatment failure requires further research.

Interhuman Transmission as a Potential Key Parameter for Geographical Variation in the Prevalence ofPneumocystis jiroveciiDihydropteroate Synthase Mutations

Pneumocystis jirovecii dihydropteroate synthase (DHPS) mutations are associated with failure of prophylaxis with sulfa drugs. This retrospective study sought to better understand the geographical variation in the prevalence of these mutations. DHPS polymorphisms in 394 clinical specimens from immunosuppressed patients who received a diagnosis of P. jirovecii pneumonia and who were hospitalized in 3 European cities were examined using polymerase chain reaction (PCR) single-strand conformation polymorphism. Demographic and clinical characteristics were obtained from patients' medical charts. Of the 394 patients, 79 (20%) were infected with a P. jirovecii strain harboring one or both of the previously reported DHPS mutations. The prevalence of DHPS mutations was significantly higher in Lyon than in Switzerland (33.0% vs 7.5%; P < .001). The proportion of patients with no evidence of sulfa exposure who harbored a mutant P. jirovecii DHPS genotype was significantly higher in Lyon than in Switzerland (29.7% vs 3.0%; P < .001). During the study period in Lyon, in contrast to the Swiss hospitals, measures to prevent dissemination of P. jirovecii from patients with P. jirovecii pneumonia were generally not implemented, and most patients received suboptimal prophylaxis, the failure of which was strictly associated with mutated P. jirovecii. Thus, nosocomial interhuman transmission of mutated strains directly or indirectly from other individuals in whom selection of mutants occurred may explain the high proportion of mutations without sulfa exposure in Lyon. Interhuman transmission of P. jirovecii, rather than selection pressure by sulfa prophylaxis, may play a predominant role in the geographical variation in the prevalence in the P. jirovecii DHPS mutations.

High Prevalence of Dihydropteroate Synthase Mutations in Pneumocystis jirovecii Isolated from Patients with Pneumocystis Pneumonia in South Africa

Pneumocystis jirovecii pneumonia (PCP) is an important cause of morbidity and mortality in immunocompromised patients. Sulfa-containing drugs are used for the treatment and prophylaxis of PCP. Mutations in the P. jirovecii fas gene, which encodes dihydropteroate synthase (DHPS), are associated with prior exposure to sulfa drugs, and their appearance suggests the emergence of variants with reduced sulfa susceptibility. The present study examined the prevalence of DHPS mutations in P. jirovecii strains isolated from South African patients with PCP. P. jirovecii infection was investigated by immunofluorescence microscopy and quantitative real-time PCR with respiratory specimens from 712 patients (93% of whom were >15 years of age) with suspected PCP consecutively received for the detection of P. jirovecii over 1 year. PCR amplification and sequencing of the DHPS fas gene was attempted with DNA from the P. jirovecii-positive samples. P. jirovecii infection was confirmed by immunofluorescence microscopy in 168/712 (24%) of the patients. Carriage of the fungus was revealed by real-time PCR in 17% of the patients with negative microscopy results. The P. jirovecii fas gene was successfully amplified from specimens from 151 patients and sequenced. Mutations resulting in the Thr55Ala and/or Pro57Ser amino acid substitution were detected in P. jirovecii strains from 85/151 (56%) patients. The high frequency of PCP episodes with P. jirovecii harboring DHPS mutations in South Africa indicates that populations of this fungus are evolving under the considerable selective pressure exerted by sulfa-containing antibiotics. These results, similar to previous observations of sulfa drug resistance in bacterial populations, underscore the importance of the rational use of sulfa medications either prophylactically against PCP or for the treatment of other infections.

Absence of Pneumocystis jirovecii dihydropteroate synthase gene mutations among samples from a group of AIDS patients in China

Pneumocystis jirovecii dihydropteroate synthase (DHPS) gene mutations are associated with failure of sulfur prophylaxis of Pneumocystis pneumonia. Here the P. jirovecii DHPS gene was amplified from bronchoalveolar fluid of 10 AIDS patients in China. No DHPS gene mutations were observed. The results suggest that the prevalence of DHPS mutations in China may be low.

Pneumocystis jirovecii pneumonia in Spanish HIV-infected patients in the combined antiretroviral therapy era: prevalence of dihydropteroate synthase mutations and prognostic factors of mortality

The incidence of Pneumocystis jirovecii pneumonia (PCP) in HIV-infected patients has decreased thanks to sulfa prophylaxis and combined antiretroviral therapy. The influence of P. jirovecii dihydropteroate synthase (DHPS) gene mutations on survival is controversial and has not been reported in Spain. This prospective multicenter study enrolled 207 HIV-infected patients with PCP from 2000 to 2004. Molecular genotyping was performed on stored specimens. Risk factors for intensive care unit (ICU) admission and mortality were identified using a logistic regression model. Seven patients (3.7%; 95% confidence interval [CI], 1.5–7.5%) had DHPS mutations. Overall mortality was 15% (95% CI, 10–21%), rising to 80% (95% CI, 61–92%) in patients requiring mechanical ventilation. None of the patients with DHPS mutants died, nor did they need ICU admission or mechanical ventilation. PaO 2 <60 mm Hg at admission was a predictor of ICU admission ( P = 0.01), and previous antiretroviral therapy predicted non-ICU admission ( P = 0.009). PaO 2 <60 mm Hg at admission and ICU admission during the 1st week were predictors of mortality ( P = 0.03 and P < 0.001, respectively). The prevalence of DHPS mutants in Spain is low and is not associated with a worse outcome. Severe respiratory failure at admission is the strongest predictor of PCP outcome.

Study of DHPS and DHFR genes ofPneumocystis jiroveciiin Thai HIV-infected patients

The combination of trimethoprim-sulfamethoxazole is widely used for the prophylaxis and treatment of Pneumocystis pneumonia (PCP) caused by Pneumocystis jirovecii. Many studies have shown that mutations in the drug target, the dihydropteroate synthase (DHPS) gene, are presumably involved with the failure of prophylaxis and treatment. We have analyzed dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) mutations in P. jirovecii isolates recovered from Thai patients. Out of 17 samples, 11.7% (2) of the DHPS gene contained a double mutation at codon 55 and codon 57, whereas out of 18 samples, 61.1% (11) of the DHFR genes contained the silent mutation at codon 104. In comparison to previous reports, we have found a higher number of DHFR mutations but a lower prevalence of DHPS mutations.

Mutations in the Dihydropteroate Synthase Gene of Human‐DerivedPneumocystis cariniiIsolates from Italy Are Infrequent but Correlate with Prior Sulfa Prophylaxis

Mutations in the human-derived Pneumocystis carinii dihydropteroate synthase (DHPS) gene have been reported with increasing frequency and have been linked to prior sulfa prophylaxis and possible emergence of sulfa resistance. This study was done to examine the prevalence and clinical significance of P. carinii DHPS mutations in Italian patients. A previously described single-strand conformation polymorphism technique was used to identify P. carinii DHPS mutations in 107 patients with acquired immunodeficiency syndrome. Overall prevalence (8%) was low compared with that in other reports. Mutations were observed in 19% (6/31) of patients exposed to sulfa prophylaxis, compared with 4% (3/76) of patients not exposed to sulfa prophylaxis (P=.017). No significant association was observed between the presence of DHPS mutations and mortality, CD4 cell count, or demographic factors. The study confirms the association between DHPS mutations and prior sulfa prophylaxis and shows that the prevalence of DHPS mutations in an Italian patient population is lower than that in other populations.