Fast Technology Analysis Enables Identification of Species and Genotypes of Latent Microsporidia Infections in Healthy Native Cameroonians.

Several enteric microsporidia species have been detected in humans and other vertebrates and their identifications at the genotype level are currently being elucidated. As advanced methods, reagents, and disposal kits for detecting and identifying pathogens become commercially available, it is important to test them in settings other than in laboratories with "state-of-the-art" equipment and well-trained staff members. In the present study, we sought to detect microsporidia DNA preserved and extracted from FTA (fast technology analysis) cards spotted with human fecal suspensions obtained from Cameroonian volunteers living in the capital city of Yaoundé to preclude the need for employing spore-concentrating protocols. Further, we tested whether amplicon nucleotide sequencing approaches could be used on small aliquots taken from the cards to elucidate the diversity of microsporidia species and strains infecting native residents. Of 196 samples analyzed, 12 (6.1%) were positive for microsporidia DNA; Enterocytozoon bieneusi (Type IV and KIN-1), Encephalitozoon cuniculi, and Encephalitozoon intestinalis were identified. These data demonstrate the utility of the FTA cards in identifying genotypes of microsporidia DNA in human fecal samples that may be applied to field testing for prevalence studies.

Sterols of Saccharomyces cerevisiae erg6 Knockout Mutant Expressing the Pneumocystis carinii S-Adenosylmethionine:Sterol C-24 Methyltransferase.

The AIDS-associated lung pathogen Pneumocystis is classified as a fungus although Pneumocystis has several distinct features such as the absence of ergosterol, the major sterol of most fungi. The Pneumocystis carinii S-adenosylmethionine:sterol C24-methyltransferase (SAM:SMT) enzyme, coded by the erg6 gene, transfers either one or two methyl groups to the C-24 position of the sterol side chain producing both C28 and C29 24-alkylsterols in approximately the same proportions, whereas most fungal SAM:SMT transfer only one methyl group to the side chain. The sterol compositions of wild-type Sacchromyces cerevisiae, the erg6 knockout mutant (Δerg6), and Δerg6 expressing the P. carinii or the S. cerevisiae erg6 gene were analyzed by a variety of chromatographic and spectroscopic procedures to examine functional complementation in the yeast expression system. Detailed sterol analyses were obtained using high performance liquid chromatography and proton nuclear magnetic resonance spectroscopy ((1)H-NMR). The P. carinii SAM:SMT in the Δerg6 restored its ability to produce the C28 sterol ergosterol as the major sterol, and also resulted in low levels of C29 sterols. This indicates that while the P. carinii SAM:SMT in the yeast Δerg6 cells was able to transfer a second methyl group to the side chain, the action of Δ(24(28)) -sterol reductase (coded by the erg4 gene) in the yeast cells prevented the formation and accumulation of as many C29 sterols as that found in P. carinii.

Pneumocystis carinii sterol 14α-demethylase activity in Saccharomyces cerevisiae erg11 knockout mutant: sterol biochemistry.

Pneumocystis carinii is an unusual fungus that can cause pneumonitis in immunosuppressed laboratory rats. Reactions in sterol biosynthesis are attractive targets for development of antimycotic drugs. A key enzyme in sterol biosynthesis is sterol 14α-demethylase (14DM), which is coded by the erg11 gene. Here we describe detailed sterol analysis of wild-type Saccharomyces cerevisiae and in an erg11 knockout mutant expressing either P. carinii or S. cerevisiae 14DM from a plasmid-borne cDNA. Sterols of the three strains were qualitatively and quantitatively analyzed using thin-layer chromatography, high-performance liquid chromatography, and gas-liquid chromatography and mass spectrometry and nuclear magnetic resonance spectroscopy. Biochemical evidence for functional complementation was provided by detecting the same major sterols in all three strains with ergosterol being by far the most abundant. A total of 25 sterols was identified, 16 of which were identified in all three strains. The ratios of lanosterol:14-desmethyllanosterol in the three strains indicate that the mutant transformed with erg11 showed more 14DM activity than wild-type yeast. The sterol analyses also indicated that the P. carinii 14DM can utilize the sterol substrates used by the S. cerevisiae 14DM and suggested that the yeast 14DM in the yeast cell utilizes 4α-methyl sterols better than the P. carinii enzyme.

Evidence for high prevalence of Pneumocystis jirovecii exposure among Cameroonians.

Cameroon lacks the capacity for routine Pneumocystis pneumonia (PcP) diagnosis, thus, the prevalence of Cameroonian exposure to this microbe is unknown. It is known that Pneumocystis infecting different mammalian host species represent diverse phylogenetic backgrounds and are now designated as separate species. The highly sensitive nature of ELISA and the specificity afforded by using human-derived P. jirovecii Msg peptides has been shown to be useful for serological analysis of human sera. Thus, sera from patients in Yaoundé, the capital city of Cameroon, were analyzed for anti-P. jirovecii antibodies by enzyme-linked immunosorbent assay (ELISA) using three recombinant major surface glycoprotein (Msg) peptide fragments, MsgA1, MsgB, and MsgC1. Based on serum recognition of one or more of the three fragments, 82% of the total samples analyzed was positive for antibodies to P. jirovecii Msg, indicating high prevalence of P. jirovecii infection or colonization among Cameroonians. Different Msg fragments appear to be recognized more frequently by sera from different geographic regions of the globe. Antibodies in the Cameroonian serum samples recognized MsgA1>MsgC1>MsgB, suggesting that different P. jirovecii strains exist in different parts of the world and/or human populations differ in their response to P. jirovecii. Also, HIV(+) patients diagnosed with respiratory infections (such as TB and pneumonia) and maintained on trimethoprim/sulfamethoxazol prophylaxis had relatively lower anti-Msg titers. Whether PcP prophylaxis has significant effects on the quality of life among HIV(+) patients in Cameroon warrants further investigation.

Microsporidian infection is prevalent in healthy people in Cameroon.

Most studies of opportunistic infections focus on those with weak immune systems, such as human immunodeficiency virus (HIV)/AIDS patients and children. However, there is a lack of information on these infectious agents in healthy people worldwide. In the present study, stool samples from both HIV patients and healthy people were examined to begin filling in this serious gap in the understanding of human microsporidiosis, particularly the enteric parasite Enterocytozoon bieneusi. Specimens were obtained from 191 individuals living in Yaoundé, the capital city of Cameroon, in sub-Sahara Africa, including 28 HIV-positive patients who also had tuberculosis (TB). E. bieneusi prevalence was 35.7% among the HIV(+) TB patients, whereas it was only 24.0% among 25 HIV(-) TB patients in the same hospital. Unexpectedly, the prevalence (67.5%) of microsporidiosis was found to be even higher for 126 immunocompetent individuals than for those with TB (healthy people compared to HIV(+) TB and HIV(-) TB patients; P < 0.001). The immunocompetent group included people ranging from 2 to 70 years of age living in four different neighborhoods in Yaoundé. The highest prevalence (81.5%) was among teenagers, and the highest mean infection score (+2.5) was among children. Additional studies of immunocompetent people in other parts of Cameroon, as well as in other countries, are needed to better understand microsporidiosis epidemiology. There is still much more to be learned about the natural history of microsporidia, the pathogenicity of different strains, and the role of enteric microsporidia as opportunistic infections in immunodeficient people.