Clindamycin Clindamycin induction test in induction test in treating patients treating patients

infected with infected with methicilin resistant methicilin resistant

Staphylococcus Staphylococcus aureusaureus

Presented by Iyad KaddoraPresented by Iyad Kaddora

Staphylococcus aureusStaphylococcus aureus Belongs to Micrococcaceae family.Belongs to Micrococcaceae family. Gram positive cocci.Gram positive cocci. Clusters resembling grape.Clusters resembling grape. Part of the humans normal flora.Part of the humans normal flora. Exist in air and water.Exist in air and water.

Number one cause of nosocomial Number one cause of nosocomial infections.infections.

Approximately 25% to 30% of the Approximately 25% to 30% of the population is colonized.population is colonized.

Staphylococcus aureus Staphylococcus aureus images images

Health info. 2005

S. aureus Virulence S. aureus Virulence FactorsFactors

Surface proteinsSurface proteins Invasions Invasions Surface factorsSurface factors Biochemical propertiesBiochemical properties Exotoxins Exotoxins

Inherent and acquired resistance to Inherent and acquired resistance to antimicrobial agentsantimicrobial agents

molbio.princeton. university

40% of nosocomial 40% of nosocomial S. S. aureusaureus infections are infections are methicillin resistantmethicillin resistant

First reported in 1960sFirst reported in 1960s Causes severe morbidity and mortality Causes severe morbidity and mortality

worldwide worldwide Endemic in many European and American Endemic in many European and American

hospitals hospitals Many in-patients are colonized or infected Many in-patients are colonized or infected 25% hospital personnel may be carriers 25% hospital personnel may be carriers Spread by hand, usually of health Spread by hand, usually of health

care workers care workers

Risk factors for methicilin Risk factors for methicilin resistant Staphylococcus resistant Staphylococcus

aureus colonizationaureus colonization Advanced age Advanced age Male gender Male gender Previous hospitalization Previous hospitalization Length of hospitalization Length of hospitalization Chronic medical illness Chronic medical illness Prior and prolonged antibiotic therapy Prior and prolonged antibiotic therapy Presence and size of a wound Presence and size of a wound Exposure to colonized or infected Exposure to colonized or infected

patient patient

Proportion of nosocomial Proportion of nosocomial MRSA among the intensive MRSA among the intensive

care unit patientscare unit patients

NNIS System.

Rates of hospital MRSA Rates of hospital MRSA isolates from 324 isolates from 324

geographically distributed geographically distributed US health care institutions US health care institutions

in year 2003in year 2003

Pfizer. © 2005 Pfizer Inc.

Antibiotics ResistanceAntibiotics Resistance Antibiotics are used to treat bacterial Antibiotics are used to treat bacterial

infections, but recently they start infections, but recently they start becoming less effective.becoming less effective.

In the past few years In the past few years S. aureus S. aureus has began has began to show more resistant to commonly used to show more resistant to commonly used antibiotics.antibiotics.

S. aureus has developed new strains S. aureus has developed new strains called methicilin resistant called methicilin resistant Staphylococcucs aureus (MRSA).Staphylococcucs aureus (MRSA).

Methcilin resistance now refers to multi-antibiotic resistant group.

ClindamycinClindamycin antibiotic is drug antibiotic is drug of choice for treating patients of choice for treating patients infected with MRSAinfected with MRSA

Clindamycin Clindamycin ββ-lactam-lactam antibiotic. antibiotic. Inhibits the synthesis of protein in bacterial Inhibits the synthesis of protein in bacterial

organism.organism. Prevents the bacteria from replicating.Prevents the bacteria from replicating.

The failure of clindamycin treatment to MRSA The failure of clindamycin treatment to MRSA infected patients, raises a big concern to health infected patients, raises a big concern to health care professional and attending physicians.care professional and attending physicians.

Antibiotics resistance Antibiotics resistance mechanismsmechanisms

The resistance to erythromycin and The resistance to erythromycin and clindamycin occurs by one of two clindamycin occurs by one of two mechanisms.mechanisms.

Efflux: typically mediated by Efflux: typically mediated by msrAmsrA gene.gene.

Ribosome alteration: occur through Ribosome alteration: occur through methylation of the ribosomal target methylation of the ribosomal target site, and this resistance is mediated site, and this resistance is mediated by by erm erm gene.gene.

Objective:Objective: Many studies have been performed Many studies have been performed

regarding MRSA. regarding MRSA.

New test has been developed to test the New test has been developed to test the future resistance of MRSA strains to future resistance of MRSA strains to clindamycin. clindamycin.

The hypotheses: MRSA strains are The hypotheses: MRSA strains are becoming more resistant to clindamycin becoming more resistant to clindamycin during 2004/2005 year compared to during 2004/2005 year compared to 2000/2001.2000/2001.

Materials and Materials and methodologymethodology

The testing specimens were collected in The testing specimens were collected in year 2000/2001, and year 2004/2005. year 2000/2001, and year 2004/2005.

The specimens were saved in order to be The specimens were saved in order to be evaluated for clindamycin resistance.evaluated for clindamycin resistance.

D test is performed on MRSA strains from D test is performed on MRSA strains from sources other than urine.sources other than urine.

MRSA has to be erythromycin resistant MRSA has to be erythromycin resistant and clindamycin sensitive.and clindamycin sensitive.

The D TestThe D Test

D test is way to detect inducible D test is way to detect inducible clindamycin resistance.clindamycin resistance.

In order for the resistance to show In order for the resistance to show up inducing agent is required.up inducing agent is required.

D test output:D test output:

1. Positive D test.1. Positive D test.

2. Negative D test.2. Negative D test.

D-test principleD-test principle

D test is done to allow erythromycin D test is done to allow erythromycin induce production of methylase. induce production of methylase.

Erythromycin ribosome methylase is a Erythromycin ribosome methylase is a gene that encodes enzymes which confer gene that encodes enzymes which confer inducible or constitutive resistance to inducible or constitutive resistance to clindamycin.clindamycin.

Induced clindamycin resistance is Induced clindamycin resistance is detected by forming a D shape letter on detected by forming a D shape letter on the agar plate. the agar plate.

D-test positivist on the original wound culture isolate from the case patient. E, erythromycin; CL, clindamycin.

Clindamycin disk

Erythromycin disk

A flattening of the zone in the area between the two A flattening of the zone in the area between the two disks disks (letter D shape) will indicate the organism’s ability to (letter D shape) will indicate the organism’s ability to induce induce clindamycin resistance in the future.clindamycin resistance in the future.

“D”

Clinical Infectious Diseases 2003;37:1257-60

D test procedure: D test procedure:

Make 0.5 McFarland suspensions Make 0.5 McFarland suspensions (turbidity measurement) in3 ml sterile (turbidity measurement) in3 ml sterile inoculum’s water.inoculum’s water.

Sterile swab is used to inoculateSterile swab is used to inoculate

the organism to blood agar plate.the organism to blood agar plate. Place an erythromycin disk 15 to Place an erythromycin disk 15 to

26 mm away from the clindamycin disk, 26 mm away from the clindamycin disk,

in the blood agar plate.in the blood agar plate. Incubate 18-24 hours at 35Incubate 18-24 hours at 35°C.°C.

Disk induction testing. (A)Constitutive clindamycin resistance. (B) Negative disk induction test indicating the absence of inducible clindamycin resistance. (C) Positive disk induction test indicating inducible clindamycin resistance.

Journal of Clinical Microbiology, April 2005, p. 1716-1721, Vol. 43, No. 4

Results of the D testResults of the D test

Clinical Infectious Diseases 2003;37:1257-60

- All clinical S. aureus Isolates at the Johns Hopkins Hospital- Nov 1, 2002 through Dec 17, 2002- 512 Total S. aureus Isolates

Clindamycin Susceptibility Testing for Adult & Pediatric S. aureus Isolates

Discordant Susceptibility

•Adult: 36%

•17% iMLS

•Pediatric: 32%

•20% iMLS

All Adult S. Aureus

64%16%

3%

17%

AdultNonDiscordant

Adult Neg DTest

Adult DtestMissing

Adult iMLS

All Pediatric S. Aureus

68%8%

4%

20%

PedNonDiscordant

Ped Neg Dtest

Ped DtestMissing

Ped iMLS

Clinical Infectious Diseases 2003;37:1257-60

Clindamycin Susceptibility Testing for MRSA

All MRSA

59%20%

1%

20%

MRSANonDiscordant

MRSA NegDtest

MRSA DtestMissingMRSA iMLS

Clinical Infectious Diseases 2003;37:1257-60

ReportReport LocationLocation

(Pediatric vs. (Pediatric vs. Adult)Adult)

Subject for Subject for D-testD-test

Positive Positive

D-testD-test

Como-Como-SabettiSabetti IDSA IDSA 2002 #922002 #92

Minnesota Minnesota

(Not (Not specified)specified)

64% of all MRSA

84%84%

Frank PIDJ2002;21:530

Chicago (Pediatric)

38% of all MRSA

94%94%

Sattler Sattler PIDJ2002;21:91PIDJ2002;21:9100

Houston(Pediatric)

90% of all MRSA

8%8%

Current Current StudyStudy

BaltimoreBaltimore

(combined)(combined)Ped:25%Ped:25%

Ad: 44%Ad: 44%43%43%

51%51%

Reported Frequency of In Vitro Inducible Resistance to Clindamycin in MRSA

Clinical Infectious Diseases 2003;37:1257-60

Clindamycin treatment of MRSA infections

31/33 were D test positive

9/31 treated with clindamycin 1 could not be evaluated 3 received multiple antibiotics 5 treated with clindamycin only

3/5: minor skin infections resolved on clindamycin

2/5: clinical failures on clindamycinFrank PIDJ 2002;21:530.

Lab Protocol for Lab Protocol for S. S. aureusaureus

S. aureus cultured

MRSA

Clinda R or Eryth S/Clinda S

MSSA

Clinda S and Erythro R

Routine D-test D-test at request of Physician

Report Clinda MIC Report Clinda=R

Clinda S and Erythro R

Clinda R or ErythS /Clinda S

Report Clinda MIC

+ +- -

Report Clinda=R Report Clinda MICReport Clinda=R Report Clinda MICReport Clinda=R Report Clinda MIC

Clindamycin Treatment Clindamycin Treatment of S. aureus Infectionsof S. aureus Infections

MRSAMRSA Important therapeutic option ifImportant therapeutic option if

Erythromycin and clindamycin sensitive Erythromycin and clindamycin sensitive Erythromycin-resistant, clindamycin sensitive Erythromycin-resistant, clindamycin sensitive

IF D-test negative IF D-test negative

MSSAMSSA Beta lactam more widely usedBeta lactam more widely used Concern for treatment failure same as for Concern for treatment failure same as for

MRSA, if clindamycin S, erythromycin R, MRSA, if clindamycin S, erythromycin R, D test positiveD test positive

Clinical Significance of Clinical Significance of In VitroIn Vitro Inducible Resistance to Inducible Resistance to

ClindamycinClindamycin

Increasing use of clindamycin for MRSAIncreasing use of clindamycin for MRSA Importance of awareness of potential for Importance of awareness of potential for

increased risk of treatment failure with increased risk of treatment failure with positive D test:positive D test: MRSA & MSSAMRSA & MSSA Rates of positive D test in Rates of positive D test in S. aureusS. aureus may may

varies by age, region, timevaries by age, region, time D-test erythromycin R/ clindamycin S MRSA & D-test erythromycin R/ clindamycin S MRSA & MSSA before reporting clindamycin MSSA before reporting clindamycin

susceptibilitysusceptibility

Conclusion Conclusion The high frequency of positive D test for The high frequency of positive D test for

MSSA isolates raises concern that MSSA isolates raises concern that clindamycin may fail to treat MSSA.clindamycin may fail to treat MSSA.

Clindamycin should be avoided as a treatment Clindamycin should be avoided as a treatment for patients infected by S. aureus exhibiting for patients infected by S. aureus exhibiting inducible resistanceinducible resistance

The proportion of S. aureus with in vitro The proportion of S. aureus with in vitro inducible clindamycin resistance may vary by inducible clindamycin resistance may vary by region, age group, and methicillin sensitivity region, age group, and methicillin sensitivity

Conclusion Conclusion There has been a marked increase in the There has been a marked increase in the

number of patients with infections that number of patients with infections that are unreceptive to clindamycin treatment.are unreceptive to clindamycin treatment.

The large number of positive D test may The large number of positive D test may explain the failure of clindamycin in explain the failure of clindamycin in treating the infected patients.treating the infected patients.

This study has demonstrated the This study has demonstrated the

importance of performing D test on MRSA importance of performing D test on MRSA Isolates. Isolates.

Future studies Future studies

Is it gender specific?Is it gender specific? Is it age specific?Is it age specific? Repeated infections?Repeated infections? Environment effects? Environment effects? Molecular mechanism of antibiotics Molecular mechanism of antibiotics

resistance?resistance? Improving the D test.Improving the D test.

Acknowledgment Acknowledgment

Dr. Harrison Dr. Harrison BSC 661BSC 661

Questions? Questions?