Genetics of Fungi Pathogenic for Man

Abstract

Great strides have been made in research on fungi pathogenic to man and animal during the last three decades, but little progress has been made in the genetics of these microorganisms. The principal reason for such a delay in genetic research is that mechanisms for genetic recombination were not known to exist in most of the pathogens.¹ It was not until the early part of the last decade that the parasexual cycle in Aspergillus fumigatus² and heterothallism in several ringworm fungi were discovered.^3-8 The reports of heterothallism in dermatophytes stimulated medical mycologists to search for the perfect state in systemic pathogens. Within the last 5 years, heterothallism has been discovered in Blastomyces dermatitidis, Histo-plasma capsulatum, and Geotrichum candidum.^9-11 Although for the last 10 years steady progress has been made employing these fungi as genetic tools, our knowledge of the genetics of human pathogenic fungi is fragmentary compared with what is known about the saprophytes and plant pathogens. This review is restricted to the results of recent genetic studies on true fungi pathogenic to man and animals. Although pathogenic fungi, by broad definition, might include those producing poisonous effects upon ingestion and those which cause disease only rarely and under special circumstances, this review is devoted only to those fungi generally recognized as pathogens for man. An understanding of the basic principles of mycology and genetics is assumed.     

CHARACTERIZATION AND ANTI-MICROBIAL SUSCEPTIBILITY OF GRAM-NEGATIVE BACTERIA ISOLATED FROM BLOODSTREAM INFECTIONS OF CANCER PATIENTS ON CHEMOTHERAPY IN PAKISTAN

Purpose: Bloodstream infection remains a major cause of morbidity and mortality in patients undergoing treatment for cancer. Severe infections due to Gram-negative bacilli & staphylococci are common in cancer patients. Altered gut flora because of frequent antibiotic administration and damage of epithelial surfaces contribute to the development of infection. To access the use of new potent antibiotics against bloodstream infection in cancer patients and to determine the cross resistance of Gram-negative bacterial strains. Materials and Methods: We studied the bacterial spectrum & antimicrobial susceptibility pattern of cephalosporins, fluoroquinolones, carbapenems and aminoglycosides against Gram-negative bacterial strains in cancer patients. The susceptibility was determined by broth dilution method according to National Committee for Clinical Laboratory Standards (NCCLS) now called Clinical Laboratory Standards Institute (CLSI) during study period (July 2006 to Jan 2007). Results: A total of 60 Gram-negative bacterial blood cultures were examined. Among these, Pseudomonas aeruginosa was the most common (38%). The Minimum Inhibitory Concentration at which 50% (MIC₅₀) and 90% (MIC₉₀) of Enterobacteriaceae and P. aeruginosa inhibited were found. Resistance in P.aeruginosa against cefepime, meropenem, ciprofloxacin, ceftriaxone, tobramycin, cefoperazone and imipenem was 60%, 13%, 80%, 67%, 40%, 90% and 10% respectively while for Enterobacteriaceae 80%, 20%, 88%, 72%, 20%, 90% and four per cent resistance was observed. Meropenem was found to be the most effective antimicrobial against Gram-negative bacteria. Conclusion: High resistance observed in this study warrants the needs of surveillance of resistant pattern of antimicrobial agents. Due to increased level of drug resistance, carbapenem would be a prudent choice in high- risk cases.     

单管多用快速鉴定培养基在临床微生物实验教学中的应用

目的:简化革兰阴性菌鉴定程序,缩短鉴定时间,便于学生掌握实验技能,提高教学质量。方法:将4株实验菌株分别接种于自己研制的尿素苯丙氨酸单管多用快速鉴定培养基与购买商品化的单管尿素、苯丙氨酸鉴定培养基做对比实验。结果:该课题所选择的两项试验,应用自制尿素苯丙氨酸单管多用快速鉴定培养基只需接种一管鉴定培养基内,35℃,培养3h,即可得到尿素苯丙氨酸试验结果;接种于购买商品化的单管尿素、苯丙氨酸鉴定培养基需接种两支不同鉴定培养基内35℃,培养24h,才能得到尿素苯丙氨酸试验结果。结论:自制尿素苯丙氨酸单管多用快速鉴定培养基,经两组鉴定培养基的对比实验,证明该培养基设计合理,4株实验菌鉴定准确率为100%,操作简单,培养鉴定时间明显缩短,结果易于判定,因此自制的尿素苯丙氨酸单管多用快速鉴定培养基非常适用于临床微生物实验教学。     

我院2005～2006年医院感染病原菌分布及其耐药性研究

目的:了解我院近2年医院感染病原菌的分布及其耐药性。方法:采用回顾性调查方法,对4653株病原菌进行统计分析。结果:真菌709株,占15.2%;革兰阳性(G+)球菌1078株,占23.2%;革兰阴性(G-)杆菌2866株,占61.6%。产超广谱β-内酰胺酶大肠杆菌和肺炎克雷伯菌2年平均检出率分别为36.5%、27.9%。G+球菌对青霉素、苯唑西林、头孢唑啉、阿莫西林/克拉维酸、红霉素、复方新诺明、环丙沙星的2年平均耐药率达84.5%;G-杆菌对氨苄西林2年平均耐药率达96.0%,对头孢噻肟、头孢吡肟、庆大霉素、复方新诺明、环丙沙星、氨曲南的2年平均耐药率达52.7%。结论:2年来,医院感染病原菌G-杆菌增加,G+球菌不变,真菌感染有逐年降低趋势。细菌耐药性不断增强,临床应加强对抗菌药物使用的干预。     

2004—2007年某医院1885株临床病原菌的分布与耐药分析

目的了解新乡市第一人民医院2004—2007年1885株临床常见病原菌分布及耐药情况。方法菌株鉴定采用复星公司FORTUNE.2000和珠海黑马生物工程有限公司全自动微生物鉴定系统,药敏试验用纸片扩散法（K-B法）。结果在1885株病原菌中革兰阴性杆菌60.3%,革兰阳性球菌35.7%,真菌4.0%。对革兰阴性杆菌耐药率较低的抗菌药物为亚胺培南、头胞他啶、阿米卡星、呋喃妥因等。某些常见抗菌药物,如头孢他啶、哌拉西林、左氧氟沙星、四环素等2004、2005、2006年耐药率逐年提高,2007年明显降低。对革兰阳性球菌耐药率较低的抗菌药物为万古霉素、亚胺培南、利福平等,青霉素、苯唑西林等2004、2005、2006年耐药率逐年提高,2007年明显降低。红霉素、阿奇霉素、复方新诺明、环丙沙星2006年已开始降低,亚胺培南、头孢唑林、克林霉素、利福平、四环素等有耐药率升高的趋势。结论开发抗菌药物、加强细菌的耐药性检测及强调抗菌药物的合理使用等,依然是今后抗感染界控制细菌耐药性蔓延的主要措施。     

肠杆菌科细菌微量生化数码鉴定板研制及应用研究

目的：研制一种肠杆菌科细菌微量生化数码鉴定板,为微生物鉴定提供一种新的检测手段。方法：作者根据不同细菌的生化反应特性,利用微生物代谢产物,配制高纯度生化基质、采用无菌脱水干燥技术,使不同生化反应培养基吸附在相应结构坚实、透明度高、反应易见的聚苯乙烯载体内。选用15项细菌生化反应按一定顺序排列构成YKS-15 e肠杆菌科细菌微量生化数码鉴定板,同时编制了相应的细菌编码鉴定手册,并进行了真实性、可靠性评价。结果：经6株标准菌株验证：阳性、阴性生化反应明显,结果准确。所有反应均可12 h内完成。60株从各类临床标本分离鉴定临床菌株经肠杆菌科细菌微量生化数码鉴定板与VITEK32法检测,符合率达96.97%。可对24个属85种肠杆菌科细菌进行鉴定。结论：该鉴定板使用方便、具有简易化、标准化、快速化、生化反应明显、结果准确等特点。     

青岛地区革兰阴性杆菌的分布及耐药性监测

目的了解青岛地区常见革兰阴性杆菌的种类、分布及耐药状况,为临床用药提供依据。方法收集青岛地区4所医院临床分离的2362株革兰阴性杆菌,采用ATB Expression自动细菌鉴定系统对菌种进行鉴定,用K-B法进行药物敏感性实验。结果分离出的革兰阴性杆菌中,主要以大肠埃希菌（ECO）、铜绿假单胞菌（PAE）、肺炎克雷伯菌（KPN）、不动杆菌属（AC-）、阴沟肠杆菌（ECL）多见;大多数革兰阴性杆菌对广谱青霉素、第三代头孢菌素、氨基糖苷类和喹诺酮类抗菌药物的耐药率高;头孢吡肟（FEP）对革兰阴性非发酵菌抗菌作用差,对肠杆菌科细菌耐药率较低,为17.5%-33.9%;头孢哌酮/舒巴坦（CFS）和哌拉西林/他唑巴坦（TZP）对革兰阴性杆菌的抗菌作用强,耐药率分别为9.9%-24.6%和9.3%-29.2%;亚胺培南（IMP）对革兰阴性杆菌的抗菌活性最强,除PAE外,细菌耐药率均〈5%。结论革兰阴性杆菌对常用抗菌药物耐药性较高,开展地区性细菌耐药监测十分重要。     

外科非发酵菌感染的临床分布与耐药性分析

目的了解医院外科非发酵菌的临床分离状况及常见菌株的耐药性,指导临床合理选用抗菌药物。方法分离出的非发酵菌采用VITEK-60 AMS细菌鉴定仪鉴定,用K-B法进行体外药敏试验。结果2002年1月-2005年12月共检出非发酵菌463株,其中铜绿假单胞菌最为常见（55.07%）,其次为鲍氏不动杆菌（20.52%）和嗜麦芽寡养单胞菌（11.88%）;标本来源主要为痰液、引流液、伤口分泌物,分别占31.97%、13.39%、12.31%;科室来源主要是SICU、器官移植外科、烧伤外科,各占28.08%、17.28%、12.10%。居前3位的非发酵菌耐药较为严重,且呈多重耐药性。结论外科非发酵菌以呼吸道、伤口感染常见,其耐药现象严重,宜根据药敏结果选用敏感抗菌药物治疗。     

5年革兰阴性杆菌耐药性变迁分析

目的分析近5年主要革兰阴性杆菌对常用抗菌药物耐药性的变迁。方法对医院1999-2003年1464株革兰阴性杆菌的药敏试验进行回顾性分析,药敏试验采用K-B纸片扩散法。结果铜绿假单胞菌、大肠埃希菌对哌拉西林的耐药率分别由1999年的17.6%、42.9%增至2003年的79.2%、68.9%;对环丙沙星的耐药率分别由1999年的4.3%、40.0%增至2003年的36.0%、73.5%;大肠埃希菌对喹诺酮类抗菌药物耐药率>50.0%,对三代头孢菌素的耐药率多在30.0%~40.0%;不动杆菌属对哌拉西林、头孢曲松的耐药率由1999年的31.2%、36.0%增至2003年的67.5%、74.1%;沙雷菌属对头孢他啶、头孢曲松、庆大霉素、阿米卡星和哌拉西林的耐药率增长迅速;亚胺培南对革兰阴性杆菌依然保持强大抗菌活性,头孢哌酮/舒巴坦和哌拉西林/他唑巴坦也显示较强的抗菌活性。结论近5年革兰阴性杆菌对常用抗菌药物的耐药率增长迅速,如何抑制细菌耐药率的过快增长已成为全球性的难题。     

321株非发酵革兰阴性杆菌耐药性报道

目的了解医院感染常见非发酵革兰阴性杆菌的分布和耐药情况。方法常规方法进行细菌培养及鉴定,Kirby-Bauer法检测非发酵革兰阴性杆菌对12种抗菌药物的药敏结果,2001年版NCCLS标准判断。结果321株菌中铜绿假单胞菌占53.9%;不动杆菌属占17.4%,嗜麦芽寡养单胞菌占12.5%,3种主要非发酵革兰阴性杆菌共占83.8%;铜绿假单胞菌耐药率为28.3%~87.3%,耐药率低的抗菌药物是亚胺培南、哌拉西林、阿米卡星、头孢他啶;不动杆菌属耐药率为14.3%~78.5%,耐药率较低的抗菌药物是亚胺培南、环丙沙星、哌拉西林;嗜麦芽寡养单胞菌耐药率为37.5%~82.5%,耐药率低的抗菌药物是头孢他啶,其他均存在较高耐药率。结论铜绿假单胞菌、不动杆菌属、嗜麦芽寡养单胞菌是引起医院感染的主要非发酵革兰阴性杆菌,对多种抗菌药物存在高耐药率,是临床面临的严峻问题,应加强监测。