Geographical Differences in Human Oral Yeast Flora, ARTYKUŁY NAUKOWE (probiotyki, mikroflora, germ-free)
[ Pobierz całość w formacie PDF ]
//-->BRIEF REPORTGeographical Differencesin Human Oral Yeast FloraJianping Xu1and Thomas G. Mitchell2Department of Biology, McMaster University, Hamilton, Ontario, Canada;and2Department of Molecular Genetics and Microbiology, Duke UniversityMedical Center, Durham, North Carolina1The oral yeast flora of healthy humans from eastern NorthAmerica and China were sampled and compared. Chinesepersons harbored a greater number and diversity of yeastspecies in the mouth. Furthermore,Candida albicans,whichis the predominant commensal and etiologic species of can-didiasis in Europe and the Western Hemisphere, was rela-tively rare in China.The most prevalent fungal infection of humans is candidiasis,which is caused by endogenous species ofCandidathat aremembers of the microbial flora of the oral mucosa and otherbody surfaces [1, 2]. Although there is global interest inCandidaspecies, there is little knowledge about global ecological char-acteristics ofCandidaspecies. Numerous studies of the asso-ciations betweenCandidaspecies and human populations inEurope and the Americas have repeatedly confirmed that themost common commensal and etiologic species isCandidaalbicans[1–5]. However, relatively little is known about theyeast flora and etiology of yeast infections in developing coun-tries. Because yeast infections are often caused by endogenousspecies and strains, and because species ofCandidaand othercommensal yeasts differ in their pathogenicity, susceptibility toantifungal drugs, and other clinically important phenotypes[1–3], it is prudent to investigate the distribution of these path-ogenic yeasts in different geographical areas. The objective ofthis study was to compare the oral yeast flora of healthy peoplein China and eastern North America.Subjects and methods.The Chinese samples were obtainedfrom 239 healthy volunteers from 5 geographically distinct areasReceived 9 July 2002; accepted 8 October 2002; electronically published 19 December2002.Financial support: US National Institutes of Health (grant AI 28836).Reprints or correspondence: Dr. Thomas G. Mitchell, Box 3803, Dept. of Molecular Geneticsand Microbiology, Duke University Medical Center, Durham, NC 27710 (tom.mitchell@duke.edu).Clinical Infectious Diseases 2003; 36:221–42003 by the Infectious Diseases Society of America. All rights reserved.1058-4838/2003/3602-0015$15.00in 3 provinces, which are located in the south-central (Jiangxi),east-central (Jiangsu), and west-central (Sichuan) regions ofChina. The North American samples were obtained from 483individuals in 3 geographic areas of eastern North America, 2of which are in the United States (Miami, FL, and Durham,NC) and 1 of which is in Canada (Wolfville, Nova Scotia).These Chinese and North American populations were com-parable in age (range, 15–76 years) and sex (378 men and 344women). All samples were obtained during the period of Feb-ruary 1997 through January 1998. No individual had an ap-parent illness, and none had taken any antifungal medicationin the weeks before samples were obtained. In China, all of thepeople who were sampled were Han Chinese, the major ethnicgroup. The North American subjects from Miami consistedentirely of Latin American individuals, the Canadians were allwhite, and the racially mixed Durham population was separatedinto 3 subgroups (Chinese American, African American, andwhite/other).Sterile swabs were used to sample the upper and lower outergingiva of each person. After sampling, the tip of each swabwas immediately severed and submerged in a sterile cryogenictube for storage and transport. Each tube contained 0.5 mL ofsterile enrichment broth composed of 2% (weight/volume)yeast extract, 1% Bacto-peptone (BD), 2% dextrose, 18% glyc-erol, and chloramphenicol (50mg/mL).This medium affordsexcellent survival and recovery of medical yeasts. All specimenswere processed in the same laboratory. Subcultures werestreaked onto CHROMAgar medium (CHROMAgar), whichselects for yeast growth and permits the direct identification ofC. albicans(green color) andCandida tropicalis(blue color).This medium does not select for any particular species of yeasts[6]. Every yeast colony of a different color or morphology wastransferred to nutrient medium and identified with use of thestandard yeast identification system, API 20C (bioMerieux).´For the few isolates that were not identified with use of these2 methods, DNA was extracted, and a portion (D1/D2) of the28S rRNA was amplified, sequenced, and compared with se-quences from the GenBank database. Because neither API 20Cnor CHROMAgar distinguishesC. albicansfrom the closelyrelatedCandida dubliniensis,all strains identified asC. albicanswere further tested for growth at 45 C on Sabouraud glucoseagar, and PCR amplification was performed withC. albicansspecies–specific primers [7]. However, no strain ofC. dublin-iensiswas isolated. All unique colonies were identified, and,with a few exceptions, individual oral swabs yielded only asingle species of yeast.BRIEF REPORT•CID 2003:36 (15 January)•221Downloaded fromby guest on December 13, 2013Table 1.Yeast species isolated from the oral cavities of healthy volunteers in regions of China and North America.No. (%)No. of of hostshosts with yeasts5847 (81.0)5No. (%) of each species isolatedCa5CfCgu32Cl18Cp4CtOtherCgl, 1; Ch, 1;Ha, 1; Rg, 1;Sc, 6Tc, 1Ha, 1Rr, 113 (8.1)Ck, 1Cgl, 12 (1.0)CountryChinaProvinceor stateJiangxiCity orcommunitySitou VillageEthnicityChineseaSpeciesbdiversity0.846Huangtugang ChineseNanchangJiangsuSichuanTotal for ChinaCanadaUSANova ScotiaFloridaWolfvilleMiamiWhiteLatin AmericanChinese AmericanAfrican AmericanWhite, otherTotal for NorthAmericaNanjingChengduChineseChineseChinese903523332392934584831448361 (67.8)23 (65.7)11 (47.8)18 (54.5)160 (66.9)18 (62.1)14 (41.2)17 (29.3)17 (35.4)125 (39.8)191 (39.5)34315 (9.4)1791617114173 (90.6)104134 (2.1)1543912211 (0.5)296551146 (3.1)221235 (2.6)0.6940.8620.7450.6790.7910.1120.5930.1180.1670.17819 (11.9) 34 (21.3) 7 (4.4) 63 (39.4) 9 (5.6)North Carolina DurhamNOTE.Ca,Candida albicans;Cf,Candida famata;Cgl,Candida glabrata;Cgu,Candida guilliermondii;Ch,Candida humicola;Ck,Candida krusei;Cl,Candida lusitaniae;Cp,Candida parapsilosis;Ct,Candida tropicalis;Ha,Hansenula anomala;Rr,Rhodotorula rubra;Rg,Rhodotorula glutinus;Sc,Saccharomyces cerevisiae;Tc,Trichosporon cutaneum;USA, United States of America.No significant difference was observed in the oral yeast carriage rate and species composition between male and female hosts or among different age groups either within a sample or for thewhole collection.bSpecies diversity was calculated as (1Sp2)N/(N 1) , whereNis the sample size andpiis the frequency of a particular species in the sample. Species diversity has a maximum value of 1.0 wheniall hosts have different yeast species, and it has a minimum value of 0 when all hosts harbor the same yeast species.aDownloaded fromby guest on December 13, 2013Results.The resulting yeast isolates and carriage rates arelisted in table 1. In eastern North America, the recovery ofyeasts was similar for all 3 geographic areas and different racialgroups. The overall rate of carriage was 39.5% (range, 29.3%–62%), and species diversity was low (0.178):C. albicanswasthe predominant isolate, with an overall frequency of 90.6%(range, 64%–100%). The other species isolated from the mouthwereCandida parapsilosis(3.1% of species recovered),Candidatropicalis(2.6%),Candida famata(2.1%), and a single isolateeach (0.5%) ofCandida glabrata, Candida krusei,andCandidalusitaniae.These rates of carriage and the species isolated aresimilar to those noted in previous studies of oral yeasts recov-ered from healthy individuals and outpatients in European andWestern nations [1, 4, 7].In contrast to the homogeneity of yeasts among the sites inNorth America, the overall carriage of oral yeasts was higherand the array of yeast species was significantly different in China(P!.01 for both comparisons).C. albicanswas not the mostfrequently isolated species in any of the 5 regions. Indeed,C.albicansranked fourth in prevalence and accounted for only9.4% (range, 0%–17.4%) of all yeasts isolated in China. The 3most common yeast species wereC. parapsilosis(39.4%),Can-dida guilliermondii(21.3%), andC. famata(11.9%). These 3species generally occurred at very low frequency or not at allin other surveyed geographic regions [1]. At 4 of the sites inChina,C. parapsilosiswas the most prevalent species; at theother site,C. guilliermondiiwas the most common isolate. Sev-eral studies have implicated a strong association ofC. para-psilosiscolonization of the hands and attachment to catheterswith opportunistic candidemia among neonates [5, 8, 9].Discussion.The oral yeast microflora of healthy Chinesepersons contrasts with the current conceptions about the ecol-ogy of yeasts in humans. The oral yeast microflora were notdetermined by ethnicity: the rates of carriage and yeast specieswere similar among Chinese individuals and persons from otherracial groups in eastern North America, but they differed fromthe rates and species isolated from Chinese people living inChina. The differences between China and eastern North Amer-ica are not related to the recent shifts in yeast flora that haveresulted from the widespread use of antifungal drugs in NorthAmerican patient populations. All 722 of the volunteers sam-pled here were healthy, and none had taken any commercialantifungal drugs before samples were obtained. Indeed, theusual azole-resistant species,C. glabrata, C. lusitaniae,andC.krusei,were recovered in very low numbers in both China andeastern North America (table 1).There are several possible explanations for the observed dif-ferences in the prevalences and types of oral yeast microflorabetween China and eastern North America. The higher carriagerate in China may be related to poor oral hygiene. For example,toothbrushing is not commonly practiced in 2 of the 5 com-munities that were sampled in China (Sitou Village and Huang-tugang), and these 2 communities had the highest rates of yeastcarriage (81% and 68%, respectively). Alternatively, the widerspectrum of yeast species isolated from people in China mayreflect an ancestral human-yeast association, whereas, in NorthAmerica, undetermined societal factors, which perhaps relateto industrialization, globalization, lifestyle, diet, regular dentalcare, or other factors, may favor the selection ofC. albicansover other species. This hypothesis is supported by studies ofthe yeast flora among Chinese persons in Hong Kong, whorepresent the most westernized population of China. Similarto the findings from eastern North America, Chinese personsin Hong Kong had lower rates of yeast carriage (range,13%–24% of persons), andC. albicanspredominated (range,77%–84% of isolates) [3, 10, 11].It is also possible that the people from whom we obtainedsamples were not representative of their respective geographicpopulations. However, this is unlikely for several reasons. Par-ticipation was voluntary, and the volunteers in each area werenot selected or subject to selective bias. Within each region,the sex ratios were close to 1, and the age ranges were broadand evenly distributed. Furthermore, the different geographicareas within both eastern North America and China were sep-arated by great distances, and travel by natives residing in theselocations was not common.In addition, the results could not be attributed to the in-vestigators or methods because the same procedures were usedto obtain and process the cultures. The specimens from Chinaand Canada and approximately one-half of the specimens fromNorth Carolina were obtained by one of us (J.X.), the remainingsamples from North Carolina were obtained by the other(T.G.M.), and the swabs from Miami were collected by a studentin our laboratory (A. R. Ramos). All of the isolates were cul-tured and identified in our laboratory at Duke (Durham, NC).Unfortunately, there is scant information about which spe-cies ofCandidamost commonly cause candidiasis in China. IfC. albicansis more pathogenic than other species, it may causethe majority of opportunistic infections in China, as elsewhere.However, the incidence of candidiasis may be comparativelylower in China. Conversely, if the incidence and etiology ofopportunistic candidiasis reflect the endogenous yeast flora,which is the current consensus, this report would predict a highincidence of candidiasis in China, predominated by speciesother thanC. albicans.Downloaded fromby guest on December 13, 2013AcknowledgmentsWe are grateful to all of the volunteers who participated inthis study. We thank Adela R. Ramos, for obtaining the samplesfrom Florida, and Dee Amick, for helping with identificationof yeast isolates. We are indebted to Jun Zhou, Xing Wei, TingBRIEF REPORT•CID 2003:36 (15 January)•223Chen, and Huamou Zhou, who helped arrange the samplecollections in China.References1. Odds FC.Candidaand candidosis. London: Bailliere Tindall,1988.2. Hazen KC. New and emerging yeast pathogens. Clin Microbiol Rev1995;8:462–78.3. Leung WK, Dassanayake RS, Yau JY, Jin LJ, Yam WC, SamaranayakeLP. Oral colonization, phenotypic, and genotypic profiles ofCandidaspecies in irradiated, dentate, xerostomic nasopharyngeal carcinomasurvivors. J Clin Microbiol2000;38:2219–26.4. Kleinegger CL, Lockhart SR, Vargas K, Soll DR. Frequency, intensity,species, and strains of oralCandidavary as a function of host age. JClin Microbiol1996;34:2246–54.5. Kam AP, Xu J. Diversity of commensal yeasts within and among healthyhosts. Diagn Microbiol Infect Dis2002;43:19–28.6. Pfaller MA, Houston A, Coffmann S. Application of CHROMagarCandida for rapid screening of clinical specimens forCandida albicans,Candida tropicalis, Candida krusei,andCandida(Torulopsis)glabrata.J Clin Microbiol1996;34:58–61.7. Xu J, Boyd CM, Livingston E, Meyer W, Madden JF, Mitchell TG.Species and genotypic diversities and similarities of pathogenic yeastscolonizing women. J Clin Microbiol1999;37:3835–43.8. Levy I, Rubin LG, Vasishtha S, Tucci V, Sood SK. Emergence ofCandidaparapsilosisas the predominant species causing candidemia in children.Clin Infect Dis1998;26:1086–8.9. Huang YC, Lin TY, Leu HS, Peng HL, Wu JH, Chang HY. OutbreakofCandida parapsilosisfungemia in neonatal intensive care units: clin-ical implications and genotyping analysis. Infection1999;27:97–102.10. Sedgley CM, Samaranayake LP. The oral prevalence of aerobic andfacultatively anaerobic gram-negative rods and yeasts in Hong KongChinese. Arch Oral Biol1994;39:459–66.11. Sedgley CM, Samaranayake LP, Chan JC, Wei SH. A 4-year longitudinalstudy of the oral prevalence of enteric gram-negative rods and yeastsin Chinese children. Oral Microbiol Immunol1997;12:183–8.Downloaded fromby guest on December 13, 2013224•CID 2003:36 (15 January)•BRIEF REPORT
[ Pobierz całość w formacie PDF ]