新生隐球菌格鲁比变种国内菌株的多位点微卫星灶分型

目的 应用多位点微卫星灶分型（MLMT）对国内6个城市分离出的新生隐球菌格鲁比变种（Cryptococcus neoformans var.grubii）进行基因分型，了解该变种的国内基因型分布特征。方法 提取已鉴定的43株新生隐球菌格鲁比变种DNA，用PCR 对3个微卫星位点（CNG1, CNG2, CNG3）的基因片段进行扩增后测序.再计算每一菌株位点基序重复数（CNG1对应TA重复,CNG2对应GA重复,CNG3对应CAT重复）；据基序重复数判定各菌株的基因型。结果 所有43株菌中，MLMT-17型占83.72%, 该型在临床和环境的菌株中分别占86.67%, 70%。MLMT-39,-40是新发现的基因型。结论 在我国，MLMT-17是最常见的新生隐球菌格鲁比变种基因型，普遍存在于临床和环境菌株中。表明国内临床新生隐球菌病的感染菌株主要源于本土环境菌株。     

新生隐球菌格鲁比变种临床株与环境株微卫星基因型的小鼠毒力实验研究

目的 了解巴西新生隐球菌格鲁比变种(C. neoformans var.grubü)多位点微卫星定型(multilocus microsatllite typing,MLMT)在临床和环境中的分布特点,探讨不同微卫星型的新生隐球菌格鲁比变种临床株和环境株的毒力差异.方法 根据多位点微卫星分型技术对分离自巴西的40株(17株临床株和23株环境株)新生隐球菌格鲁比变种进行分型,筛选出临床株及环境株中分布占优势的菌株,应用小鼠毒力试验分别对其进行毒力检测,通过发病情况及病理切片比较毒力差异.结果 40株格鲁比变种共鉴定出11种微卫星型,临床株中的优势菌株为MLMT-13型,共9株,占临床株的52.9%(9/17),环境株中的优势菌株为MLMT-36型,共10株,占环境株的43.5%(10/23);小鼠毒力试验结果显示MLMT-13型感染小鼠后发病率为100%,而MLMT-36型发病率为7.5%,且病理结果也存在明显差异.结论 格鲁比变种在从环境迁徙到宿主的过程中,毒力随环境的变化发生了改变,该变化也可在其微卫星重复序列上体现出来.该实验证明新生隐球菌格鲁比变种的分布及来源与微卫星型之间存在相关性,临床株MLMT-13型和环境株MLMT-36型之间存在着显著毒力差异.

Abstract：

Objective To investigate the genetic relation between Cryptococcus neoformans var.the clinical strains in MLMT - 13 genotype and the environmental strains in MLMT - 36 genotype. Methods Multilocus microsatellite typing (MLMT) method was applied for the genotype analysis in our study.Through this method, we recognized two genotypes that distinguish a majority of clinical and environmental strains. In order to compare virulence between the two types, we chose to infect BALB/c mice (6 weeks,female) with 9 MLMT-13 strains and 10 MLMT-36 strains intravenously. Results Forty( 17 clinical and 23 environmental isolates) were analyzed. Of 17 clinical strains, 9 belonged to a major type of MLMT-13 (52.9%). They were mainly isolated from clinical specimens. About 43.5% of strains from the environment belong to a major type of MLMT-36, which are indigenous to environments and which were not isolated from clinical samples. The mortality rate and pathological changes of the above mice were observed during two months after injection. The results showed that the mortality rate of mice infected with MLMT-13 strains was 100%, while the mortality rate with MLMT-36 strains was 7. 5%. The pathological sections showed that lesions of MLMT-13 infected mice appeared in the brain, lungs, liver and kidneys, while the lesions of MLMT-36 infected mice only appeared in the brain. Most brains of MLMT-13 infected mice were distorted,and both the number and size of lesions in such brains were much larger than those of MLMT-36 infected mice. Conclusion Our study illustrated the virulent difference between MLMT-13 and MLMT-36, which are isolated from patients and environment respectively. The results inferred that some genetic changes, such ss microsatellite repeats, might occur between environmental and clinical isolates through their environmental adaptation progress.     

中国部分地区新生隐球菌临床感染患病情况分析

常见的致病性隐球菌分为新生隐球菌和格特隐球菌两个种,其中新生隐球菌分为血清A型(grubii变种)和血清D型(新生变种),格特隐球菌分为血清B型和C型.隐球菌的有性期分为a和α两个交配型.它们在生态学、易感人群和临床特征等方面存在明显不同,我国关于新生隐球菌临床感染患病情况的资料稀少.     

新生隐球菌格鲁比变种表型变异菌株的基因及毒力对比研究

新生隐球菌(Cryptococcus neoformans)属于真菌界担子菌门隐球菌属,是临床上的致病真菌,可致器官移植等免疫抑制患者发生新生隐球菌病,与艾滋病有一定相关.宽大的荚膜是其典型形态学特征及临床分离鉴定的重要依据,我们在实验中对获赠自日本千叶大学医学部真菌研究所的新生隐球菌进行传代培养时发现有2株菌(IFM56803和IFM56743)发生了显著的表型变异,出现光滑型(SM)及黏液型(MC)两种不同的菌落,荚膜形态也出现明显差异,墨汁染色发现MC株的隐球菌荚膜较SM株的厚4～5倍.     

万古霉素非敏感肠球菌的筛选和基因型分析

目的对实验室保存的325株肠球菌进行万古霉素非敏感肠球菌筛选,并对筛选出的菌株进行耐药表型、耐药基因型、菌株同源性分析。方法采用琼脂平皿二倍稀释法筛选万古霉素非敏感肠球菌,并检测菌株对替考拉宁的敏感性;采用PCR方法检测万古霉素非敏感肠球菌的耐药基因型;通过肠道细菌基因间重复一致序列(ERIC)PCR技术、脉冲场凝胶电泳(PFGE)技术、多位点序列分型(MLST)技术进行菌株的同源性分析。结果从325株临床分离肠球菌中共筛选出17株万古霉素非敏感肠球菌,包括1株粪肠球菌、11株屎肠球菌和5株鹑鸡肠球菌。其中1株粪肠球菌和11株屎肠球菌对万古霉素显示高水平耐药,对替考拉宁耐药或中介耐药,PCR检测结果显示van A型;5株鹑鸡肠球菌对万古霉素中介耐药,对替考拉宁敏感,PCR检测结果显示van C1型。ERIC同源性分析显示同基因型的大多数菌株显示相似的分型;PFGE同源性分析显示,17株临床万古霉素非敏感肠球菌分型不同,不属于单克隆流行播散;MLST同源性分析显示,1株临床万古霉素非敏感粪肠球菌属于ST4,11株临床万古霉素非敏感屎肠球菌共分为6个ST型,其中4株属于ST78,是屎肠球菌出现频率最高的ST型。结论我国万古霉素耐药菌在粪肠球菌中分离率较低,但屎肠球菌中万古霉素耐药情况较严重,并且耐药菌株携带易于传播和转移的van A基因。同源性分析结果显示万古霉素耐药存在同源性传播的可能性。     

鲍曼不动杆菌临床分离株表型、基因型和耐药基因的对比研究

目的 对比研究鲍曼不动杆菌临床分离株基因型和编码耐药基因的差异,并分析其与临床多重耐药性的关系.方法 随机收集中南大学湘雅二医院2008年9月至2009年9月分离的77株鲍曼不动杆菌,采用WHO推荐的K-B法对鲍曼不动杆菌进行临床常见15种抗生素药物敏感试验,并对药敏谱进行分析.用随机扩增多态性DNA法(RAPD)技术进行基因分型.并利用PCR对β-内酰胺酶基因TEM-1、IMP、OXA-23、OXA-24、AmpC和氨基糖苷类修饰酶基因aac(3)-Ⅰ、aac(6')-Ⅰ、ant(3")-Ⅰ和16S rRNA甲基化基因armA、rmtA、rmtB进行扩增及序列分析.对比分析鲍曼不动杆菌耐药基因的携带情况,以及与基因型和耐药性的关系.结果 77株鲍曼不动杆菌中敏感菌株有31株,对5种或5种以上抗生素耐药的多重耐药菌株46株,内含全耐药菌株10株.RAPD技术将其分为17型,为A-G型,多重耐药株中E型为优势克隆株(17株),在重症监护病房(ICU)中流行最广,占47.1%(8/17).敏感株中各型散在分布.PCR扩增结果显示,多重耐药株和敏感株携带TEM-1、IMP、OXA-23、OXA-24、AmpC、aac(3)-Ⅰ、aac(6')-Ⅰ、ant(3")-Ⅰ和armA耐药基因的比率分别为95.7%、39.1%、84.8%、54.3%、87.0%、89.1%、84.8%、45.7%、63.0%和58.1%、9.7%、32.3%、48.4%、48.4%、29.0%、45.2%、12.9%、9.7%,未发现rmtA和rmtB基因阳性菌株.经x2检验,除OXA-24外,其余各耐药基因携带率比较差异有统计学意义(P＜0.05).药敏分析提示携带以上耐药基因的鲍曼不动杆菌菌株的耐药率明显高于未携带该基因的菌株,其中对阿米卡星和庆大霉素耐药的菌株,其氨基糖苷类酶基因均阳性(34.8%),含所测的所有β-内酰胺酶基因的菌株均为全耐药株.结论 与临床分离的敏感鲍曼不动杆菌相比,多重耐药株耐药谱广,耐药率高,其携带β-内酰胺酶基因和氨基糖苷类酶基因种类多,分离率高,且同一克隆的多重耐药株可在病室内和病室间传播.     

耐万古霉素肠球菌耐药基因及毒力因子研究

目的 研究耐万古霉素肠球菌(VRE) van基因及肠球菌毒力基因esp、hyl、cylA、gelE 的携带情况,分析其对抗菌药物的耐药特性和流行特性,为临床抗菌药物的选择和感染控制提供依据.方法 采用含有6 μg/ml万古霉素的琼脂筛选平板(ADSP)筛选VRE菌株,VITEK-60全自动微生物分析仪检测常用抗菌药物的敏感性;运用PCR方法检测万古霉素耐药基因vanA、vanB、vanC1/C2、vanM和其携带的毒力基因esp、hyl、cylA、gelE;并对VRE菌株进行多位点序列分型(MLST).结果 360株肠球菌中共筛出VRE菌株7株,均为屎肠球菌;7株VRE对万古霉素均为高水平耐药,部分菌株对替考拉宁中介和敏感.所有VRE菌株均携带vanA基因,vanB、vanC1/ C2、vanM均为阴性;毒力因子esp均为阳性,其中一株菌株同时携带4种毒力因子.7株VRE的ST型呈散在分布.结论 本研究发现基因型为vanA型而表型为vanB型的VRE菌株;VRE菌株常对多种抗菌药物耐药且毒力因子携带率高;利奈唑胺可作为治疗VRE菌株的推荐药物.     

质粒介导KPC-2型碳青霉烯酶肺炎克雷伯菌儿童分离株耐药基因研究

目的 研究碳青霉烯类耐药肺炎克雷伯菌临床儿童分离株的耐药特点及分子流行病学特征.方法 收集温州医学院附属第二医院2010年7月-2011年6月从儿童标本中分离的耐碳青霉烯类肺炎克雷伯菌12株,所有菌株为非重复菌株,菌种鉴定采用全自动微生物分析仪.改良的Hodge试验筛选产碳青霉烯酶阳性菌株,采用PCR法检测KPC、IMP、bla(s)、VIM、SPM和整合酶基因,测序确定基因型.对菌株进行质粒结合试验、质粒消除试验检测质粒的转移性.脉冲场凝胶电泳(PFGE)分析耐药菌株的同源性.结果 12株耐碳青霉烯类肺炎克雷伯菌对庆大霉素、妥布霉素、阿米卡星、环丙沙星、左氧氟沙星、复方磺胺甲噁唑的敏感率分别为8.3％、41.7％、58.3％、8.3％、8.3％、33.3％;12株菌均携带有KPC-2基因,且同时携带有TEM-1和SHV型β-内酰胺酶基因,其中SHV-11-like和SHV-1 2-like各6株;11株携带CTX-M型基因,其中4株为CTX-M-14-like基因,6株CTX-M-15-like基因;2株携带有OXA-10型基因,1株携带有PER-1基因.未检出NDM-1、GIM、SPM、SIM、VIM型碳青霉烯酶基因.12株均为Ⅰ类整合酶基因(int1)阳性.2株通过接合试验把质粒传递给受体菌EC600.所有接合子blaTEM-1基因阳性、超广谱β-内酰胺酶(ESBL)基因阳性及对亚胺培南、庆大霉素、阿米卡星、妥布霉素和头孢噻肟耐药,接合子ESBL基因型与供菌一致.2株菌经质粒消除后对亚胺培南的MIC值均有较大程度降低,消除后KPC-2基因扩增为阴性.12株KPC-2基因阳性菌株经PFGE分成5个基因型,主要为B型和C型.结论 KPC-2型碳青霉烯酶基因已经在儿童肺炎克雷伯菌中播散,常伴随携带多种类型的ESBL基因和Ⅰ类整合酶基因,部分耐药基因可通过质粒播散.     

载脂蛋白E、白细胞介素-1α基因多态性与成都地区阿尔茨海默病的关联分析

目的　探讨载脂蛋白E(apolipoprotein E,APOE)和白细胞介素 - 1α(interleukin- 1α,IL- 1α)基因多态性与成都地区阿尔茨海默病 (Alzheimer's disease,AD)的关系。方法　用聚合酶链反应 -限制性片段长度多态性技术检测成都地区流行病学调查中诊断为 AD的 114例患者和 113名健康老年人 APOE基因和 IL - 1α基因多态性。结果　中度、重度 AD组含 APOEε4基因型频率 (2 8.6 % )显著高于轻度 AD组 (18.5 % )和正常对照组 (14 .2 % ) ,其中中度、重度 AD组与正常对照组差异有显著性 (OR=2 .4 ,95 % CI:1.1～5 .5 )。将ε4等位基因频率与ε2和ε3等位基因频率之和比较 ,中度、重度 AD组与正常对照组的差异有显著性 (OR=2 .6 ,95 % CI:1.3～ 5 .3)。 AD患者组和正常对照组 IL - 1α基因型和等位基因频率分布相似 ,差异无显著性 (P>0 .0 5 )。结论　 APOEε4等位基因与中、重度 AD相关联 ,是中、重度 AD的易感因素。 IL - 1α基因多态性与中国成都地区 AD患者无关联。     

应用emm基因序列分析对104株A群链球菌分型

目的　通过emm基因序列分析对A群链球菌 (GAS)进行分型 ,探讨T型与emm型的对应关系。方法　用引物以PCR法扩增GASM蛋白的N末端并进行测序 ,确定GAS的emm型 ,并与T分型对照比较。结果　 (1) 10 4株菌株中 ,emm1所占比例最大 ,为 2 9.8% ,然后依次是emm18(9.6 % ) ,emm12 (7.7% ) ,和emm6 9(5 .8% )等。 (2 )T1、T12和T14 4 9与emm基因对应关系好 ,T116株全部对应emm1型 (10 0 % ) ,T12对应emm12 ,符合率 83.3% ,T14 4 92株均对应emm4 9型 ;其它菌型对应关系差 ;同一T型可对应数个emm基因型 ,同一emm基因型可对应不同的T型。 (3)发现 1株新的emm型菌株 ,序列已递交GenBank ,注册号为AY3472 5 9。结论　emm基因分型方法具有准确、快速、分辨力高的优点 ;我国部分地区A群链球菌emm基因分型主导型为emm1、18、12、6 9、110等菌型。     

Molecular genetic analyses of mating pheromones reveal intervariety mating or hybridization in Cryptococcus neoformans

The sexual mating of the pathogenic yeast Cryptococcus neoformans is important for pathogenesis studies because the fungal virulence is linked to the alpha mating type (MAT(alpha)). We characterized C. neoformans mating pheromones (MF(alpha) 1 and MFa1) from 122 strains to understand intervariety hybridization or mating and intervariety virulence. MF(alpha) 1 in three C. neoformans varieties showed (a) specific nucleotide polymorphisms, (b) different copy numbers and chromosomal localizations, and (c) unique deduced amino acids in two geographic populations of C. neoformans var. gattii. MF(alpha) 1 of different varieties cross-hybridized in Southern hybridizations. Their phylogenetic analyses showed purifying selection (neutral evolution). These observations suggested that MAT(alpha) strains from any of the three C. neoformans varieties could mate or hybridize in nature with MATa strains of C. neoformans var. neoformans. A few serotype A/D diploid strains provided evidence for mating or hybridization, while a majority of A/D strains tested positive for haploid MF(alpha) 1 identical to that of C. neoformans var. grubii. MF(alpha) 1 sequence and copy numbers in diploids were identical to those of C. neoformans var. grubii, while their MFa1 sequences were identical to those of C. neoformans var. neoformans; thus, these strains were hybrids. The mice survival curves and histological lesions revealed A/D diploids to be highly pathogenic, with pathogenicity levels similar to that of the C. neoformans var. grubii type strain and unlike the low pathogenicity levels of C. neoformans var. neoformans strains. In contrast to MF(alpha) 1 in three varieties, MFa1 amplicons and hybridization signals could be obtained only from two C. neoformans var. neoformans reference strains and eight A/D diploids. This suggested that a yet undiscovered MFa pheromone(s) in C. neoformans var. gattii and C. neoformans var. grubii is unrelated to, highly divergent from, or rarer than that in C. neoformans var. neoformans. These observations could form the basis for future studies on the role of intervariety mating in C. neoformans biology and virulence.     

Most cases of cryptococcal meningitis in HIV-uninfected patients in Vietnam are due to a distinct amplified fragment length polymorphism-defined cluster of Cryptococcus neoformans var. grubii VN1

Cryptococcal disease most commonly occurs in patients with an underlying immune deficit, most commonly HIV infection, and is due to Cryptococcus neoformans var. grubii. Occasionally disease due to this variety occurs in apparently immunocompetent patients. The relationship between strains infecting immunosuppressed and immunocompetent patients is not clear. Amplified fragment length polymorphism (AFLP) analysis was used to characterize the relationship between strains infecting HIV-infected and uninfected patients. Isolates from 51 HIV-uninfected patients and 100 HIV-infected patients with cryptococcal meningitis were compared. C. neoformans var. grubii VNI was responsible for infections in 73% of HIV-uninfected and 100% of HIV-infected patients. AFLP analysis defined two distinct clusters, VNIγ and VNIδ. The majority (84%) of isolates from HIV-uninfected patients were VNIγ, compared with only 38% of isolates from HIV-infected patients (odds ratio, 8.30; 95% confidence interval [CI], 3.04 to 26.6; P < 0.0001). In HIV-uninfected patients, underlying disease was less frequent in those with VNIγ infections. Two clusters of C. neoformans var. grubii VN1 are responsible for the majority of cases of cryptococcal meningitis in Vietnam. The distribution of these clusters differs according to the immune status of the host.     

Genetic characterization of environmental isolates of the Cryptococcus neoformans species complex from Brazil.

The genetic affiliation of a large number of isolates of the Cryptococcus neoformans species complex from environmental sources in Brazil has been investigated using amplified fragment length polymorphism (AFLP). The strains of C. neoformans isolated from a single tree, as well as from neighbouring trees, showed high similarity values (> 95%) of their AFLP patterns, thus suggesting considerable genetic homogeneity. The majority of isolates of C. neoformans belonged to AFLP genotype 1, and had serotype A and mating type alpha (= C. neoformans var. grubii). Three isolates belonged to AFLP genotype 2, with serotype D and mating type alpha (= C. neoformans var. neoformans). One isolate, obtained from a building in Rio de Janeiro inhabited by pigeons, belonged to the AD hybrid AFLP genotype 3. All isolates from trees of C. neoformans var. gattii (= C. gattii) belonged to AFLP genotype 6, and their banding patterns showed relatively low genetic homogeneity with a similarity value of about 76%. Isolates of this genotype occupy an environmental niche in the Americas, and they may cause disease in non-AIDS and AIDS patients as well.     

Origin of Cryptococcus neoformans var. neoformans Diploid Strains

The basidiomycetous yeast Cryptococcus neoformans is an important human fungal pathogen. Two varieties, C. neoformans var. neoformans and C. neoformans var. gattii, have been identified. Both are heterothallic with two mating types, MATa and MATalpha. Some rare isolates are self-fertile and are considered occasional diploid or aneuploid strains. In the present study, 133 isolates, mostly from Italian patients, were investigated to detect the presence of diploid strains in the Igiene Università Milano culture collection. All of the diploid isolates were further investigated by different methods to elucidate their origins. Forty-nine diploid strains were identified by flow cytometry. PCR fingerprinting using the (GACA)(4) primer showed that the diploid state was associated with two specific genotypes identified as VN3 and VN4. Determination of mating type on V8 juice medium confirmed that the majority of the strains were sterile. PCR and dot blotting using the two pheromone genes (MFa and MFalpha) as probes identified 36 of the 49 diploid isolates as MATa/alpha. The results of pheromone gene sequencing showed that two allelic MFalpha genes exist and are distinct for serotypes A and D. In contrast, the MFa gene sequence was conserved in both serotype alleles. Amplification of serotype-specific STE20 alleles demonstrated that the diploid strains contained one mating locus inherited from a serotype A parent and one inherited from a serotype D parent. The present results suggest that diploid isolates may be common among the C. neoformans population and that in Italy and other European countries serotype A and D populations are not genetically isolated but are able to recombine by sexual reproduction.     

Cryptococcus neoformans {alpha} strains preferentially disseminate to the central nervous system during coinfection

Cryptococcus neoformans is a fungal pathogen that has evolved over the past 40 million years into three distinct varieties or sibling species (gattii, grubii, and neoformans). Each variety manifests differences in epidemiology and disease, and var. grubii strains are responsible for the vast majority of human disease. In previous studies, alpha strains were more virulent than congenic a strains in var. neoformans, whereas var. grubii congenic a and alpha strains exhibited equivalent levels of virulence. Here the role of mating type in the virulence of var. grubii was further characterized in a panel of model systems. Congenic var. grubii a and alpha strains had equivalent survival rates when cultured with amoebae, nematodes, and macrophages. No difference in virulence was observed between a and alpha congenic strains in multiple inbred-mouse genetic backgrounds, and there was no difference in accumulations in the central nervous system (CNS) late in infection. In contrast, during coinfections, a and alpha strains are equivalent in peripheral tissues but alpha cells have an enhanced predilection to penetrate the CNS. These studies reveal the first virulence difference between congenic a and alpha strains in the most common pathogenic variety and suggest an explanation for the prevalence of alpha strains in clinical isolates.     

Sexual cycle of Cryptococcus neoformans var. grubii and virulence of congenic a and alpha isolates

Cryptococcus neoformans is a human-pathogenic fungus that has evolved into three distinct varieties that infect most prominently the central nervous system. A sexual cycle involving haploid cells of a and alpha mating types has been reported for two varieties (C. neoformans var. neoformans, serotype D, and C. neoformans var. gattii, serotypes B and C), yet the vast majority of infections involve a distinct variety (C. neoformans var. grubii, serotype A) that has been thought to be clonal and restricted to the alpha mating type. We recently identified the first serotype A isolate of the a mating type which had been thought to be extinct (strain 125.91). Here we report that this unusual strain can mate with a subset of pathogenic serotype A strains to produce a filamentous dikaryon with fused clamp connections, basidia, and viable recombinant basidiospores. One meiotic segregant mated poorly with the serotype A reference strain H99 but robustly with a crg1 mutant that lacks a regulator of G protein signaling and is hyperresponsive to mating pheromone. This meiotic segregant was used to create congenic a and alpha mating type serotype A strains. Virulence tests with rabbit and murine models of cryptococcal meningitis showed that the serotype A congenic a and alpha mating type strains had equivalent virulence in animal models, in contrast to previous studies linking the alpha mating type to increased virulence in congenic serotype D strains. Our studies highlight a role for sexual recombination in the evolution of a human fungal pathogen and provide a robust genetic platform to establish the molecular determinants of virulence.     

Isolation of Cryptococcus gattii and Cryptococcus neoformans var. grubii from the flowers and bark of Eucalyptus trees in India.

The association of Cryptococcus gattii with Eucalyptus trees has been well established. Here we report the isolation of both C. gattii and Cryptococcus neoformans var. grubii from the flowers and bark of Eucalyptus trees in India. We investigated a total of 233 samples of Eucalyptus trees: 120 flowers, 81 fragments of bark, and 32 leaves. C. gattii was isolated from two samples of flowers of Eucalyptus terreticornis. C. neoformans var. grubii was recovered twice from the bark of Eucalyptus camaldulensis, initially from one of three samples, and again 2 months later, from one of four samples collected beneath the canopy of the tree. The primary isolation medium was Nigerseed agar, and brown colonies were presumptively identified as C. gattii or C. neoformans. The species identification was confirmed by morphological and biochemical characteristics. Using the Crypto-Check kit (Iatron, Tokyo, Japan), the first two isolates were identified as serotype B (C. gattii) and the other two were serotype A (C. neoformans var. grubii). PCR analysis of the isolates of C. neoformans var. grubii revealed that they possessed the MATalpha mating type allele. Molecular typing by amplified fragment length polymorphism markers indicated that both isolates of C. neoformans var. grubii possessed the same genotype. This study demonstrates that C. neoformans var. grubii, as well as C. gattii, may be associated with Eucalyptus trees.     

Analyses of pediatric isolates of Cryptococcus neoformans from South Africa

Compared to the incidence in adults, cryptococcosis is inexplicably rare among children, even in sub-Saharan Africa, which has the highest prevalence of coinfection with HIV and Cryptococcus neoformans. To explore any mycological basis for this age-related difference in the incidence of cryptococcosis, we investigated isolates of C. neoformans recovered from pediatric and adult patients during a 2-year period in South Africa. From reports to the Group for Enteric, Respiratory, and Meningeal Disease Surveillance in South Africa (GERMS-SA), we reviewed all cases of cryptococcosis in 2005 and 2006. We analyzed one isolate of C. neoformans from each of 82 pediatric patients (<15 years of age) and determined the multilocus sequence type (ST), mating type, ploidy, and allelic profile. This sample included isolates of all three molecular types of serotype A or C. neoformans var. grubii (molecular types VNI, VNII, and VNB) and one AD hybrid. Seventy-seven (94%) of the strains possessed the MATα mating type allele, and five were MATa. Seventy-five (91%) were haploid, and seven were diploid. A total of 24 different STs were identified. The ratios of each mating type and the proportion of haploids were comparable to those for the isolates that were obtained from 86 adult patients during the same period. Notably, the most prevalent pediatric ST was significantly associated with male patients. Overall, these pediatric isolates exhibited high genotypic diversity. They included a relatively large percentage of diploids and the rarely reported MATa mating type.     

Molecular epidemiology of clinical Cryptococcus neoformans strains from India

Little is known about the molecular epidemiology of the human pathogenic fungus Cryptococcus neoformans in India, a country now in the midst of an epidemic of AIDS-related cryptococcosis. We studied 57 clinical isolates from several regions in India, of which 51 were C. neoformans var. grubii, 1 was C. neoformans var. neoformans, and 5 were C. neoformans var. gattii. This strain set included 18 additional sequential isolates from 14 patients. Strains were characterized phenotypically by measuring the polysaccharide capsule and by determining the MICs of standard antifungals. Molecular typing was performed by a PCR-based method using the minisatellite-specific core sequence (M13), by electrophoretic karyotyping, by restriction fragment length polymorphisms with the C. neoformans transposon 1 (TCN-1), and by URA5 DNA sequence analysis. Overall, Indian isolates were less heterogeneous than isolates from other regions and included a subset that clustered into one group based on URA5 DNA sequence analysis. In summary, our results demonstrate (i) differences in genetic diversity of C. neoformans isolates from India compared to isolates from other regions in the world; (ii) that DNA typing with the TCN-1 probe can adequately distinguish C. neoformans var. grubii strains; (iii) that TCN-1 sequences are absent in many C. neoformans var. gattii strains, supporting previous studies indicating that these strains have a limited geographical dispersal; and (iv) that human cryptococcal infection can be associated with microevolution of the infecting strain and by simultaneous coinfection with two distinct C. neoformans strains.     

Presence of α and a Mating Types in Environmental and Clinical Collections of Cryptococcus neoformans var. gattii Strains from Australia

Cryptococcus neoformans var. gattii lives in association with certain species of eucalyptus trees and is a causative agent of cryptococcosis. It exists as two mating types, MATalpha and MATa, which is determined by a single-locus, two-allele system. In the closely related C. neoformans var. neoformans, the alpha mating type has been found to outnumber its a counterpart by at least 30:1, but there have been very limited data on the proportions of each mating type in C. neoformans var. gattii. In the present study, specific PCR primers were designed to amplify two separate alpha-mating-type genes from C. neoformans var. gattii strains. These were used to survey for the presence of the two mating types in clinical and environmental collections of C. neoformans var. gattii strains from Australia. Sixty-eight of 69 clinical isolates produced both alpha mating type-specific bands and were assumed to be of the alpha mating type. The majority of environmental isolates were also of the alpha mating type, but the a mating type was located in two separate areas. In one area, the a mating type outnumbered the alpha mating type by 27:2, but in the second area, the ratio of the two mating types was close to the 50:50 ratio expected for sexual recombination.