Pneumocystis carinii dihydropteroate synthase mutations and treatment with sulfa or sulfone regimens: a proposal for standardized definitions for clinical evaluation

Pneumocystis jirovecii colonization in Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is associated with a chronic inflammatory response in airways and lung parenchyma that results in significant morbidity and mortality worldwide. Cigarette smoking considered as an important risk factor plays a role in pathogenesis of disease. Pneumocystis jirovecii is an atypical opportunistic fungus that causes pneumonia in immunosuppressed host, although the low levels of its DNA in patients without signs and symptoms of pneumonia, which likely represents colonization. The increased prevalence of P. jirovecii colonization in COPD patients has led to an interest in understanding its role in the disease. P. jirovecii colonization in these patients could represent a problem for public health since colonized patients could act as a major reservoir and source of infection for susceptible subjects. Using sensitive molecular techniques, low levels of P. jirovecii DNA have been detected in the respiratory tract of certain individuals. It is necessary to elucidate the role of P. jirovecii colonization in the natural history of COPD patients in order to improve the clinical management of this disease. In the current review paper, we discuss P. jirovecii colonization in COPD patients.

Colonization by Pneumocystis jirovecii and its role in disease

Although the incidence of Pneumocystis pneumonia (PCP) has decreased since the introduction of combination antiretroviral therapy, it remains an important cause of disease in both HIV-infected and non-HIV-infected immunosuppressed populations. The epidemiology of PCP has shifted over the course of the HIV epidemic both from changes in HIV and PCP treatment and prevention and from changes in critical care medicine. Although less common in non-HIV-infected immunosuppressed patients, PCP is now more frequently seen due to the increasing numbers of organ transplants and development of novel immunotherapies. New diagnostic and treatment modalities are under investigation. The immune response is critical in preventing this disease but also results in lung damage, and future work may offer potential areas for vaccine development or immunomodulatory therapy. Colonization with Pneumocystis is an area of increasing clinical and research interest and may be important in development of lung diseases such as chronic obstructive pulmonary disease. In this review, we discuss current clinical and research topics in the study of Pneumocystis and highlight areas for future research.

Dihydropteroate synthase gene mutations in Pneumocystis and sulfa resistance

We review studies of dihydropteroate synthase gene mutations in Pneumocystis jirovecii and summarize the evidence for resistance to sulfamethoxazole and dapsone.

Pneumocystis pneumonia (PCP) remains a major cause of illness and death in HIV-infected persons. Sulfa drugs, trimethoprim-sulfamethoxazole (TMP-SMX) and dapsone are mainstays of PCP treatment and prophylaxis. While prophylaxis has reduced the incidence of PCP, its use has raised concerns about development of resistant organisms. The inability to culture human Pneumocystis, Pneumocystis jirovecii, in a standardized culture system prevents routine susceptibility testing and detection of drug resistance. In other microorganisms, sulfa drug resistance has resulted from specific point mutations in the dihydropteroate synthase (DHPS) gene. Similar mutations have been observed in P. jirovecii. Studies have consistently demonstrated a significant association between the use of sulfa drugs for PCP prophylaxis and DHPS gene mutations. Whether these mutations confer resistance to TMP-SMX or dapsone plus trimethoprim for PCP treatment remains unclear. We review studies of DHPS mutations in P. jirovecii and summarize the evidence for resistance to sulfamethoxazole and dapsone.

Pneumocystis jirovecii dihydropteroate synthase genotypes in immunocompetent infants and immunosuppressed adults, Amiens, France

To date, investigations of Pneumocystis jiroveci circulation in the human reservoir through the dihydropteroate synthase (DHPS) locus analysis have only been conducted by examining P. jirovecii isolates from immunosuppressed patients with Pneumocystis pneumonia (PCP). Our study identifies P. jirovecii genotypes at this locus in 33 immunocompetent infants colonized with P. jirovecii contemporaneously with a bronchiolitis episode and in 13 adults with PCP; both groups of patients were monitored in Amiens, France. The results have pointed out identical features of P. jirovecii DHPS genotypes in the two groups, suggesting that in these two groups, transmission cycles of P. jirovecii infections are linked. If these two groups represent sentinel populations for P. jirovecii infections, our results suggest that all persons parasitized by P. jirovecii, whatever their risk factor for infection and the form of parasitism they have, act as interwoven circulation networks of P. jirovecii.

Similar genotypes of Pneumocystis jirovecii in different forms of Pneumocystis infection

This study describes the genotyping of Pneumocystis jirovecii organisms isolated from three groups of patients that developed diverse forms of P. jirovecii infection; the patients were monitored in the same French hospital. Forty archival specimens from 13 adults with Pneumocystis pneumonia, eight adults colonized by P. jirovecii and 19 immunocompetent infants infected with the fungus contemporaneously with a bronchiolitis episode were analysed retrospectively. Genotyping was performed by analysis of sequences of the internal transcribed spacer (ITS)1 and ITS2 regions, and of the dihydropteroate synthase (DHPS) locus. At the ITS regions, a high diversity of genotypes, identical main genotypes (B1a3 and B2a1) and the occurrence of mixed infections (more than one genotype) were observed in the three patient groups. At the DHPS locus, the results indicated the presence of mutants in the two adult groups, as well as in the infant group. Consequently, at these two independent genomic regions, P. jirovecii isolates from patients who developed different forms of infection and who lived in the same geographical region presented common characteristics. These results suggest that patients infected with P. jirovecii, whatever the form of infection they present, are part of a common human reservoir for P. jirovecii.