Dịch tễ học phân tử nhiễm MRSA

National Institute of Infectious DiseaseJanuary 18, 2017 Lecture 9: Molecular epidemiology of Methicillin-resistant Staphylococcus aureus MRSA infections Practices of Molecular Epidemio

National Institute of Infectious Disease

January 18, 2017

Lecture 9:

Molecular epidemiology of Methicillin-resistant Staphylococcus

aureus (MRSA) infections

Practices of Molecular Epidemiology

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Staphylococcus aureus (SA): pathovar vs non-pathovar

factors?

subsequent invasive disease?

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Staphylococcus aureus overview

 ~30% are carriers of SA (nares, intestine)

 In the US, more people die of S aureus infections than from HIV/AIDS

 Prevalence of MRSA varies from 0.6% in The Netherlands to >60% in Japan.

 Community-associated-methicillin-resistant (CA-MRSA) or community-onset SA emerged in the 1990’s

 Responsible for the increasing incidence of all MRSA infections in the US and other regions of the world

 Gaining resistance to multiple drugs

 Associated with severe clinical manifestations:

 Necrotizing faciitis

 Severe or necrotizing pneumonia

 bone and joint infections with septic thromboembolic disease

 purpura fulminans with or without Waterhouse-Friderichsen syndrome

 orbital cellulitis and endophthalmitis

 central nervous system infection

 bacteremia

 endocarditis

Story of drug-resistant S aureus

 1940-60’s: First wave: Plasmid-encoded penicillinase; became pandemic by the mid

1950s to 1960s; mostly caused by phage-type 80/81 S aureus.

 1960s: Second wave: Methicillin resistance reported in 1961 from UK; resistance

encoded by mecA (encodes penicillin binding protein, PBP 2a—low affinity to PCN);

mostly caused by COL, mostly limited to Europe

 1970s-80s: Third wave: Iberian and other clones—spread to the US and the globe in hospitals and health care settings; epidemic evolving with emergence of VISA and VRSA

 1990s: Fourth wave: CA-MRSA earliest cases reported from Australia among the indigenous populations; US: 1997-99—severe disease in children with no underlying medical problems

 2010s: Fifth wave: CA-MRSA emerging in healthcare settings

Genotyping methods for SA

 MLST: based on 7 housekeeping genes (arcC, aroE,glpF, gmk, pta, tpiA,

yqiL)(http://saureus.mlst.net/)

 Sequence type (ST): identical sequences in all 7 genes

 Clonal complex (CC): identical sequences in 5 or more of the 7 genes

 PFGE:

 Based on SmaI-digested S aureus genomic DNA

 Used to examine more recent evolutionary changes

 SCCmec

 spa typing:

 Based on 24-bp tandem repeats of the spa gene—diversity results from deletions,

duplications, and mutations

 Rapid but not as discriminatory as PFGE

 Useful in an outbreak situation

Common globally-spread MRSA lineages

Clonal complex MLST designation PFGE and other designations

CC1 ST1 USA400; Native Americans in Alaska, Canada

ST59 USA1000; most common CA-MRSA in Asia ST80 Most common CA-MRSA in Europe

CC5 ST5 USA100 and NewYork/Japan clone (N315)

ST5 USA800/Pediatric clone ST5 HDE288/Pediatric clone (Portugal)

CC8 ST250 Archaic (includes COL): Europe, UK in the

70’s; never entered the US; now gone ST247 Iberian clone and EMRSA-5

ST239 Brazilian/Hungarian clone ST239 EMRSA-1: most common in Asia (except

Japan, Korea, Australia) ST8 AUS-2 and AUS-3

ST8 USA500 and EMRSA-2,-6 ST8 CA-MRSA USA300

Common globally-spread MRSA lineages—cont.

Clonal complex MLST designation PFGE and other designations

 Dominant type: ST239

 Other names: Brazilian, British epidemic

(EMRSA-1, -4, -7, -9 and -11),Canadian

epidemic (CMRSA-3), Hungarian,

Portuguese, Nanjing/Taipei, Vienna, and

Eastern Australian epidemic

(EMRSA Aus-2 and -Aus-3) clones

Baines, SL et al, mBio, 2015

Emergence of 5 Major CA-MRSA Clonal Lineages

Diep and Otto, Trends in Microbiol 2008

Community-acquired MRSA (CA-MRSA)

CA-MRSA—risk populations

 American Indians and Alaska natives

 Pacific Islanders

 Athletes

 Jail and prison inmates

 Men who have sex with men

 Contacts of patients with CA-MRSA infection

 Military personnel

 Adult emergency room patients

 Children in day care centers

 Hospital-onset and heathcare-associated infections

USA300 or ST8 CA-MRSA clone

 Most common CA-MRSA in the US

 First reported among college football team members in Pennsylvania and prisoners in Mississippi and Los Angeles (Tenover FC, Goering RV, J AAC, 2009)

 Increased transmissibility associated with arginine catabolic mobile element (ACME) (Diep

BA et al JID, 2008)

 Carries type IV SCCmec encoding methicillin resistance; otherwise susceptible to most

other drugs

 Now appearing in hospitals

 Recently acquired a plasmid encoding resistance to β‐lactams, fluoroquinolones,

tetracycline, macrolide, clindamycin, and mupirocin (San Francisco, Chicago, New

York)(McDougal LK et al, AAC 2010; Diep BA et al Ann Intern Med 2008)

A USA300 B USA100

Proportions of methicillin-resistant Staphylococcus aureus isolates

(Carrell, M et al, EID, 2015)

A spa type B ST (Carrell, M et al, EID, 2015)

Worldwide distribution of ST8 clone

SCCmecIV: Abu Dhabi, Argentina, Australia, Austria, Belgium, Brazil, Bulgaria, Cameroon,

Canada, Canary Islands, China, Colombia, Costa Rica, Cuba, Czech Republic, Denmark, Ecuador, Finland, France, French Polynesia, Gabon,Germany, Greece, Hong Kong, Iceland, India, Iraq, Ireland, Israel, Italy, Japan,Madagascar, Mexico,Netherlands, New Zealand, Nigeria, Norway, Pakistan, Peru, Poland, Portugal, Romania, Russia, Samoa,South Korea, Spain, Sweden, Switzerland, Trinidad & Tobago, United Kingdom, United States, Uruguay, Venezuela

SCCmecV:Germany, Nigeria

SCCmecVI: Portugal

• Does colonization with SA predispose to

subsequent invasive disease?

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Severe pneumonia associated with CA-MRSA

 >8000 cases reported annually in the US

 High mortality rate: 30-70%

 Most cases are caused by USA300

 USA300 hyperproduces Panton Valentine leukocidin (PVL), α‐hemolysin (Hla), and phenol soluble modulin PSM‐α‐1‐4)

 Overproduction of these products associated with increased virulence in a rabbit model

Diep et al PNAS, 2010

Severe HA-MRSA epidemic in China (Li et al, Nature

Medicine, 2012)

 sasX, sasG genes (encoding surface proteins) associated with enhanced colonization and

increased virulence

 Found in sublineages of ST239 strains

 Located at the 3’ end of a 127.2-kb ΦSPβ‐like prophage (mobile element)

 In China,the frequency of sasX+ MRSA isolates increased from 21% to 39% between

2003-2011, mostly in hospital isolates

Phenotypes of sasX, G MRSA strains

(Roche et al 2003; Li et al, Nat Med, 2012)

 attachment to human nasal epithelial cells in vitro

 better colonization in nasal colonization mouse model

 promotes biofilm production

 decreased phagocytosis by neutrophils

 Increased abscess formation in skin and lungs in mouse models

Staphylococcus aureus (SA): pathovar vs non-pathovar

 Why do some strains of SA cause disease while others do not?

 Why do some strains of SA cause epidemics while others do not?

 Because of drug resistance?

 Because of biological factors unrelated to drug resistance?

 Because of epidemiological factors not related to any biological factors?

 Does colonization with SA predispose to

subsequent invasive disease?

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Methicillin-susceptible SA (MSSA) vs MRSA (Chambers & DeLeo, Nat Rev Med, 2009):

 88% of those causing infections from1961 through 2004 from 6 continents: CC1, CC5, CC8, CC9, CC12,CC15, CC22, CC25, CC30, CC45, and CC51/121

SCCmec gene of HA- and CA-MRSA

macrolide-lincosomide-streptogramin B

antibiotics, spectinomycin

2013: 11 SCCmec types (http://www.sccmec.org/Pages/SCC_TypesEN.html)

Factors associated with increased transmissibility

 Arginine catabolic mobile element (ACME) (Diep BA et al JID, 2008)

 SasX protein (Li et al, Nat Med, 2012)

 Lower human transmissibility of ST398 (LA-MRSA) compared to other MRSA

(Hetem DJ et al, EID, 2013)

Staphylococcus aureus (SA): pathovar vs non-pathovar

 Why do some strains of SA cause disease while others do not?

 Why do some strains of SA cause epidemics while others do not?

 Because of drug resistance?

 Because of biological factors unrelated to drug resistance?

 Because of epidemiological factors not related to any biological factors?

 Does colonization with SA predispose to

subsequent invasive disease?

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Are there nonhuman reservoirs of MRSA?

Livestock as a source?

Companion animals?

Livestock associated MRSA (LA-MRSA):

MRSA prevalence in veterinary personnel

 Australia: CC8, (ST8-IV [2B], spa t064; and ST612-IV [2B], spa variable) and ST22

associated with equine practice veterinarians (Groves MD et al PLoS One, 2016).

 Europe: ST398 prevalence among livestock veterinarians: ~40% (Verkade E et al Clin Infect Dis, 2013; Cuny C et al, PLoS One, 2009)

 North America: CC8 prevalence 10-18% among equine veterinarians (Weese JS et al, Emerg ID, 2005)

 United Kingdom: ST22 prevalence ~18% among companion animal veterinarians

 Japan (Hokkaido): ST5, ST30 from companion animal (dog) veterinarians (Ishihara

K Microbiol Immunol 2014)

 Contrast to human healthcare workers: 4.6% in review of 127 outbreaks

(AlbrichWC, Harbarth S, Lancet ID, 2008)

LA-MRSA in livestock animals

 Pigs: ST398 in Europe, occasionally in Japan, China

 Pigs: ST9 in East Asia

 Chicken, duck: ST8 (SCCmecIV) (Ogata K et al, J UOEH, 産業医科大学雑誌 , 2014）

 Horses: CC8 in Australia, Europe

 Bovine milk: ST97 and ST705 in Japan (Hata E et al, J Clin Microbiol 2010)

 2 isolates of ST5 from milk identical to ST5 (New York/Japan clone)

• Does colonization with SA predispose to

subsequent invasive disease?

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strains (Wang, M et al, in prep)

• 12 articles with 6,998 subjects 

• Risk of disease after MRSA colonization: OR‐‐5∙48, 4∙98‐6∙03, 7  studies.

• Risk of disease after MSSA colonization: OR‐‐0∙95, 0∙82‐1∙10, 4  studies.  

Isolate pairs  typed (N, %)

Molecular typing  method

Summary of S aureus pathovar epidemiology

 Does drug-resistance contribute to their spread?

 Clonal distribution found in both MSSA and MRSA strains.

 MRSA USA300 and MSSA USA300 show no difference in virulence in the rabbit model (Diep

et al, J Infect Dis 2008).

 “Successful” epidemic clones have distinct genes and encoded products that may be

responsible for their increased “fitness”

 Panton-Valentine leukocidin? (PVL found in phagetype 80/81)

 Phenol soluble modulin α‐type?

 Alpha hemolysin?

 sasX?

 “Successful” epidemic clones disappear as other new clones replace them This

“competition” drives epidemiology of pathotypes of S aureus.

 Are LA-MRSA potential new reservoir for human MRSA infections?

 Chambers H and DeLeo FR Waves of Resistance: Staphylococcus aureus in the Antibiotic

Era Nat Rev Microbiol 2009; 7: 629–641

 Mediavilla JR, Chen L, Mathema B, Kreiswirth B Global epidemiology of

community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) Current Opinion in

Microbiology 2012, 15:588–595

 Bal AM et al Genomic insights into the emergence and spread of international clones of

healthcare-, community- and livestock-associated methicillin-resistant Staphylococcus

aureus: Blurring of the traditional definitions J Glob Antimicrob Resist 2016; 6:95-101.

 Otto M MRSA virulence and spread Cell Microbiol 2012; 14: 1513–1521