MRSAMRSADefinitionDefinition

Methicillin-resistant Methicillin-resistant Staphylococcus Staphylococcus aureusaureus ( (MRSAMRSA) is a bacterium ) is a bacterium responsible for difficult-to-treat infections responsible for difficult-to-treat infections in humans. MRSA is by definition a strain in humans. MRSA is by definition a strain of of Staphylococcus aureusStaphylococcus aureus that is resistant that is resistant to a large group of antibiotics called the to a large group of antibiotics called the beta-lactams, which include the penicillins beta-lactams, which include the penicillins and the cephalosporins.and the cephalosporins.

HA–MRSA CharacteristicsHA–MRSA Characteristics

HospitalHospital––associated strains of associated strains of S. S. aureusaureus still cause about 85% of still cause about 85% of all MRSA cases.all MRSA cases.

Hospital patients with Hospital patients with S. aureusS. aureus infections are five times more infections are five times more likely to die in the hospital than likely to die in the hospital than are patients without the infection.are patients without the infection.

Multi-drug resistant (MDR)Multi-drug resistant (MDR) Vancomycin is one of the few Vancomycin is one of the few

remaining treatments for HA-remaining treatments for HA-MRSA, but it is no longer MRSA, but it is no longer effective in every case due to effective in every case due to rising MICs. rising MICs.

This electron micrograph depicts large numbers of Staphylococcus aureus bacteria, which were found on the inside surface of a catheter. The sticky-looking substance woven between the round cocci bacteria is known as a “biofilm”. Biofilms help to protect the bacteria.

Courtesy of the CDC

EvolutionEvolutionFrom HA and CA-MRSAFrom HA and CA-MRSA

1961 – MRSA first described1961 – MRSA first described Until recently, most MRSA infections started in Until recently, most MRSA infections started in

hospitals, especially among surgery and hospitals, especially among surgery and immunocompromised patients. (HA-MRSA) immunocompromised patients. (HA-MRSA)

In the 1990s, new strains of MRSA began to In the 1990s, new strains of MRSA began to strike healthy people in community settings. strike healthy people in community settings. (CA-MRSA) (CA-MRSA)

These two types of MRSA are now known as These two types of MRSA are now known as hospital-associated MRSA (HAhospital-associated MRSA (HA––MRSA) and MRSA) and community-associated MRSA (CAcommunity-associated MRSA (CA––MRSA). MRSA).

CACA––MRSAMRSA Characteristics Characteristics

Staphyloccal bacteria that have become Staphyloccal bacteria that have become resistant to beta-lactam antibiotics but resistant to beta-lactam antibiotics but NOT multi-drug resistant (MDR).NOT multi-drug resistant (MDR).

Several antibiotics remain effective Several antibiotics remain effective against CAagainst CA––MRSA, but it is an MRSA, but it is an aggressive and rapidly evolving form of aggressive and rapidly evolving form of S. aureusS. aureus..

Usually appears as a skin infection, but Usually appears as a skin infection, but it can spread quickly to a bloodstream it can spread quickly to a bloodstream infection or a very serious form of infection or a very serious form of pneumonia.pneumonia.

Cutaneous abscess caused by methicillin–resistant Staphylococcus aureus bacteria.

Courtesy of the CDC

MRSAMRSAPrevalence in ShirazPrevalence in Shiraz

Prevalence is increasing!! Prevalence is increasing!! MRSA in Nemazi hospital patientsMRSA in Nemazi hospital patients

• 2000 = 33%2000 = 33%• 2010 = 49.5% 2010 = 49.5%

VancomycinVancomycin 100%100% RifampinRifampin 100%100% ChloramphnicoleChloramphnicole 9494 ClindamycinClindamycin 8989 CiprofloxacinCiprofloxacin 8787 Co-trimoxazoleCo-trimoxazole 8585 GentamycinGentamycin 7070 CephalothinCephalothin 7070 AmikacinAmikacin 6666 ErythromycinErythromycin 7070

Pattern of sensitivity Staphylococcus

aureus, Nemazi hospital -2000

Staphylococcus aureus antibiotic pattern in nemazi hospital -2010

MRSA in IRANMRSA in IRAN

224 224 S.aureusS.aureus Isolated from: Isolated from: bloodblood 210210 PeluralPelural 55 CSFCSF 55 ascitisascitis 33 JointJoint 11 TotalTotal 224224

Staphylococcus aureus Staphylococcus aureus IdentificationIdentification

Isolates identification:Isolates identification: Gram StainGram Stain ●●CatalaseCatalase Coagulase Coagulase ●●DnaseDnase

Antibiotic Susceptibility TestAntibiotic Susceptibility Test Disk diffusion Method (CLSI protocol)Disk diffusion Method (CLSI protocol)

MRSA & VRSA :MRSA & VRSA : Oxacillin & Vancomycin screen plateOxacillin & Vancomycin screen plate MIC determination (E test) for Oxacillin & MIC determination (E test) for Oxacillin &

Vancomycin Vancomycin

MRSA & VISA in IranMRSA & VISA in Iran

Growing on Oxacillin Agar Screen plate (ASP)Growing on Oxacillin Agar Screen plate (ASP) 224 Isolates224 Isolates 84(37.5%) positive MIC84(37.5%) positive MICOXOX> 8 > 8 μμg/ml MRSAg/ml MRSA

Vancomycin MIC(Etest)Vancomycin MIC(Etest) All Isolates All Isolates MIC< 4 MIC< 4 μμg/mlg/ml No suspected

VISA/VRSA

Reporting:Reporting:(according CLSI 2006 )(according CLSI 2006 )

MRSA and methicillin-resistant, MRSA and methicillin-resistant, coagulase-negative staphylococci coagulase-negative staphylococci should be reported as resistant to all should be reported as resistant to all other penicillins, carbapenems, other penicillins, carbapenems, cephems, and β-lactam/β-lactamase cephems, and β-lactam/β-lactamase inhibitor combinations, regardless of inhibitor combinations, regardless of in in vitro vitro test results with those agents.test results with those agents.

Staphylococcus aureus in IranStaphylococcus aureus in Iran(N0=224)(N0=224)

CD

CD

ER

ER

LZ

DL

ZD

PG

PGTS

TS

RP

RP

OX

OX

CIP

CIPCCKF

KF

AK

AKTTVA

VA

QD

QD

GM

GM

FU

FU

RR5353

(24)(24)

8080

(36)(36)

44

(2)(2)

215215

(96)(96)

9292

(41)(41)

2020

(9)(9)

7878

(35)(35)

7272

(32)(32)

55

(2)(2)

7171

(32)(32)

7070

(31)(31)

102102

(45)(45)

00

(0)(0)

00

(0)(0)

7272

(32)(32)

88

(4)(4)

SS170170

(76)(76)

130130

(58)(58)

220220

(98)(98)

99

(4)(4)

131131

(58)(58)

203203

(90)(90)

146146

(65)(65)

148148

(66)(66)

218218

(97)(97)

151151

(67)(67)

150150

(68)(68)

122122

(55)(55)

224224

(100)(100)

224224

(100)(100)152152

(68)(68)

216216

(96)(96)

IRIR11

(0.5)(0.5)

1414

(6)(6)

00

(0)(0)

00

(0)(0)

11

(.5)(.5)

11

(.5)(.5)

00

(0)(0)

44

(2)(2)

11

(.5)(.5)

22

(1)(1)

33

(1)(1)

00

(0)(0)

00

(0)(0)

00

(0)(0)

00

(0)(0)

00

(0)(0)

CD=Clindamycin, ER=erythromycin, LZD=linezolid, PG=PenicillinG, TS=Co-trimoxazol, RP=Rifampin, OX=Oxacillin, CIP=Ciprofloxacin, C=Chloramphenicol, KF=Cephalothin, AK=Amikacin, T=Tetracycline, VA=Vancomycin, QD=Quinupristin-dalfopristin, GM=Gentamycin, FU=Fusidic acid