Clinical Significance and Phylogenetic Relationship of Novel Australian Pneumocystis jirovecii Genotypes

Abstract

Pneumocystis jirovecii is an important opportunistic pathogen in immunocompromised patients. Molecular typing is employed to study this pathogen, as no culture system exists. No Australian P. jirovecii strains have been previously studied. Direct sequencing, targeting the internal transcribed spacer (ITS) regions of the nuclear rRNA operon, the mitochondrial large-subunit rRNA (mt LSU rRNA), and the dihydropteroate synthase (DHPS) gene, was performed on 68 Australian samples, collected between 2001 and 2007. Seven novel Australian ITS haplotypes (a composite of the ITS1 and ITS2 regions) were identified (SYD1m, SYD1g, Isyd2, Esyd3, Osyd4, Ag, and Hc). A dendrogram of published ITS haplotypes revealed that of the seven novel haplotypes, three (SYD1m, SYD1g, and Osyd4) are closely related to the haplotype Eg. Applying statistical parsimony, an Australian haplotype network was constructed which identified Eg as the ancestral haplotype, with two unresolved loops encountered. This suggests that the ITS lacks the resolution required for evolutionary analysis. Only two mt LSU rRNA genotypes were detected, with genotype 1 predominating. Mutant DHPS genotypes were present in 13% (8/60) of the samples. The novel haplotype Isyd2 was associated with less severe disease than the other Australian haplotypes. In contrast, patients with mutant DHPS genotypes were more likely to have severe disease, require invasive ventilation, and have a poor outcome than patients with wild-type DHPS genotypes. In conclusion, genetic clinical correlates continue to be found for Pneumocystis pneumonia; however, they remain controversial and warrant further study.

Internal Transcribed Spacer Region Sequence Heterogeneity in Rhizopus microsporus : Implications for Molecular Diagnosis in Clinical Microbiology Laboratories

“…For molecular identification of fungal pathogens, the ITS is one of the most commonly used targets because its length and sequence are relatively conserved for the same fungal species but often different in different fungal species (4,23). On the other hand, due to variation in ITS sequence among different strains in some fungal species, it has also been used for fungal genotyping (11,14,21). For example, in the recent outbreak of intestinal mucormycosis, eight alleles were observed among 24 strains of R. microsporus, thereby confirming multiple strain …”

Epidemiology and clinical relevanceofPneumocystis jiroveciiFrenkel, 1976 dihydropteroate synthase gene mutations

“…Concerning PcP clinical outcomes, in a multivariate analysis, a higher death rate (3-months survival rate) was reported in patients who had mutant P. jirovecii compared to patients with the wild-type DHPS, after important mortality cofactors like age, CD4 + T cells count, and arterial oxygen partial pressure (PaO 2 ) were controlled for (Helweg-Larsen et al, 1999). Also van Hal and collaborators reported associations between P. jirovecii DHPS mutations and poor outcomes (death) compared to patients with wild-type DHPS (van Hal et al, 2009). But this correlation could not be confirmed in other studies.…”

“…These results are consistent with latter studies (Valerio et al, 2007;Alvarez-Martinez et al, 2008). A higher lactate dehydrogenase (LDH) and the need for intubation at admission were considered, also, as predictors of mortality in these patients (Valerio et al, 2007;Alvarez-Martinez et al, 2008;van Hal et al, 2009). And PaO 2 < 60 mm Hg at admission (P = 0.02) and requirement of adjunctive corticosteroids (P = 0.03) were also factors influencing outcome and mortality of patients who died of PcP (Alvarez-Martinez et al, 2008).…”

Pneumocystis jirovecii Pneumonia in AIDS Patients

“…Such mutations were shown to be associated with the use of TMP-SMX or dapsone (two DHPS inhibitors), the duration of sulfa or dapsone prophylaxis and with geographic areas in which sulfamethoxazole or dapsone were commonly used for PcP prophylaxis Kazanjian et al, 2000). However, results of studies searching specifically to establish an association between the presence of P. jirovecii DHPS mutations and clinical outcomes, such as treatment failure or death, are contradictory (Alvarez-Martinez et al, 2008, Helweg-Larsen et al, 1999Huang et al, 2004, www.intechopen.com Stein et al, 2004;van Hal et al, 2009). Outstandingly, most PcP patients carrying P. jirovecii isolates with DHPS mutations responded well to TMP-SMX treatment and survived probably because these mutations may confer a low-level of resistance to sulfa-drugs that is overcome by high drug concentration achieved in lung tissues by sulfamethoxazole (Calderon et al, 2004;Huang et al, 2004).…”