汤一苇

获上海复旦大学医学院医学学士和硕士学位，一九九五年获美国范德堡大学微生物学与免疫学博士学位。曾先后在美国联邦疾病控制预防中心和美国梅约医学中心接受博士后或住院医师培训。现任美国范德堡大学内科系和病理系双系副教授，病理系传染病分子生物学诊断室和内科系分子流行病室主任。是美国医学微生物委员会资格认证的临床微生物学家。二零零二

年入选为美国微生物学会核心期刊<<临床微生物学杂志>>主编之一，二零零五年入选为美国微生物学院院士和美国感染病与艾滋病学会会士。建立了四十余种体外核酸扩增诊断技术并用于传染病病原体的检测和定量。拥有美国或中国专利局专利四份并发表相关论著、综述和著书章节逾百篇。Dr. Yi-Wei Tang (汤一苇)

美国范德堡大学医学中心

分子传染病实验室主任

Methicillin-Resistant Staphylococcus aureus Screening: State-of-the-Art

Yi-Wei Tang, MD, PhD, FAAM, FIDSA

Associate Professor of Medicine and Pathology

Director, Molecular Infectious Disease Laboratory

Boucher & Corey.Clin. Infect. Dis. 46:S344-9, 2008

Staphylococcus aureus Causes a

Variety of Pus-forming Infections

and Toxinoses in Humans

?Superficial skin lesions such as boils,

styes and furunculosis

?Serious infections such as pneumonia, mastitis,

phlebitis, meningitis, and urinary tract infections

?Deep-seated infections, such as osteomyelitis and

endocarditis

?Food poisoning, toxic shock syndrome, necrotizing

pneumonia

?Hospital acquired (nosocomial) infection of

surgical wounds and infections associated with

indwelling medical devices

Staphylococcus aureus: a Super Bug with Loaded Virulence determinants

Lowy.N. Engl. J. Med. 339:520-32, 1998

Virulence Factors E xpressed by

Staphylococcus aureus

?Surface proteins that promote colonization of host tissues ?Invasins that promote bacterial spread in tissues; leukocidin, kinases, hyaluronidase

?Surface factors that inhibit phagocytic engulfment: capsule, protein A

?Biochemical properties that enhance their survival in phagocytes: carotenoids, catalase

?Immunological disguises: protein A, coagulase, clotting factor

?Inherent and acquired resistance to antimicrobial agents

?Exotoxins that damage host tissues or otherwise provoke symptoms of disease: SEA-G, TSST, ET

?Membrane-damaging toxins that lyse eukaryotic cell membranes: hemolysins, leukotoxin(PVL), leukocidin

Evolving “Milestones ”of Staphylococcus aureus: Resistance to Antibiotics

?PRSA: penicillin-resistant S. aureus ?MRSA: methicillin-resistant S. aureus ?VISA: vancomycin-intermediate S. aureus ?

VRSA: vancomycin-resistant S. aureus ?CA-MRSA : community-acquired MRSA

1960s 199820032005MRSA VISA VRSA CA-MRSA 1940s

PRSA

Emergency of CA-MRSA

?Dramatic emergence of new public health problem in recent years: infections with novel community-associated strains (CA-MRSA) in previously healthy individuals

?Most infections involve skin and skin structures ?Unusual frequency of invasive and lethal

infections

Epidemiology of CA-MRSA

?Increasing community-associated S. aureus infections are methicillin resistant: 2000-1 (56%), 2001-2 (57%), 2002-3 (78%)

?Risk factors included children, competitive athletes, prisoners, soldiers, native Americans, Pacific islanders, low socioeconomic status, IVDU, men who have sex with men

?Associated with unusually severe disease ?Septic shock

?Necrotizing pneumonia

?Necrotizing fasciitis

Drivers of Active Surveillance for MRSA

?Leading cause (8%) of nosocomial infections, especially surgical wound infections and pneumonia (28% each)?19,000 deaths attributable to invasive MRSA infections in 2005, most associated with health care delivery

?~1.5% of US residents carry MRSA in anterior nares

who are at higher risk of infection than noncarriers

?~25% of patients that become colonized with MRSA

during hospital stay subsequently develop infection

?MRSA is readily transmitted in health-care settings and causes frequent outbreaks

?>$500 million excess health care expenditures annually Diekema and Climo, 2008, JAMA, 299:1190

Nasal Swab Specimen Collection for MRSA

Screening

Laboratory Techniques for MRSA

Screening

?Conventional approaches

?Solid agar-based selective media

?Inhibitory substances: NaCl, tellurite, cefoxitin

?Chromogenic media: MRSA Select (Bio-Rad), CHROMagar

MRSA (BioConnections), MRSA ID (bioMerieus)

?Enrichment broths

?Molecular methods

?BD GeneOhm(Infectio Diagnostic, Ste-Foy, Canada)

?GeneXpert(Cepheid, Sunnyvale, CA, USA)

?Directly from screening specimens

?Rapid procedure done within 5 hours

?Multiple genes covered in one single reaction

?Nasal-rectal “dual”swabs

?Simultaneous screening for MRSA and VRE

Rapid and Simultaneous Screening of MRSA and VRE from Screening Clinical Specimens

?When: July 6 to November17, 2006

?Where: Waukesha Memorial Hospital, Wisconsin ?What:

?307 swabs: ear (4), nares(234), rectum (7) and skin (62)?Standard reference 1: routine culture (SBA and CAN)

?Standard reference 2: BD-Genom as tiebreaker for discrepant results between culture and MVPlex ?MVPlex: Genaco Biomedial Products, Huntsville, AL

StaphPlex Simultaneously Amplifies 18 Genes: How a Multiplex PCR Really Works

MVPlex Results and Interpretation

?Detection: Staphylococci, enterococci

?Identification: MRSA, VRE

?Speciation: 5 common CoNS

Sensitivity and Specificity of MVPlex in Comparison to Culture

Sensitivity, 93.7%; specificity, 89.9%

Sensitivity and Specificity of MVPlex in Comparison to A Resolved Standard

Sensitivity, 84.4% (culture), 97.8% (MVPlex), p=0.002

Specificity, 98.6% (culture), 95.8% (MVPlex), p>0.05

Technique Availabilities (1)

Conclusion A universal,

rapid MRSA admission

screening strategy did not

reduce nosocomial

MRSA infection in a

surgical department with

endemic MRSA

prevalence but relatively

low rates of MRSA

infection.

University of Geneva Hospitals, Switzerland