Ali Rabaan - saudi aramco medical services

Molecular Detection of MRSA and its Impact on Infection Control

Dr. Ali Rabaan, M.Med.Sci, PhD.

Head of Molecular Microbiology Laboratory

Saudi Aramco Medical Services Organization

Outlines

• History of MRSA and Antibiotics.

• Why We Worried About It.

• Prevalence.

• Transmission.

• Factors Enhance the Emergence and Transmission.

• Impact of Molecular Testing on Infection Control.

• Molecular Testing of MRSA.

Staphylococcus aureus

• Gram positive cocci.

• Arranged in a grape-like structure.

Lowy. N Engl J Med. 1998;339:520-532.

Why We Are Worried

• Greater morbidity and mortality.Greater morbidity and mortality.

• Hospitalization and supportive care.Hospitalization and supportive care.

• Increased use of:Increased use of:

Laboratory and diagnostic tests.Laboratory and diagnostic tests.

Infection control procedures.Infection control procedures.

Housekeeping procedures.Housekeeping procedures.

More expensive antimicrobialsMore expensive antimicrobials

(Very limited choices).(Very limited choices).

Length of hospital stay (9 days).

• Rubinstein and Zhanel. Lancet Infect Dis 2007.

• Lynch and Zhanel. Sem Resp Crit Care Med 2005.

www.thelancet.com Vol 367 Month xx, 2006

Prevalence of MRSA in Saudi Arabia

• Prevalence is unknown, and varies geographically.

• In Jeddah, the prevalence increased from 2% in 1988 to 33% in 1998 (T. Madni et al, 2001).

• Another study in Jeddah, MRSA comprised 7.5%/year of all S. aureus (T. Austin et al, 1994).

• In Riyadh, the prevalence ranged from 12 to 49.4% in six major hospitals (Baddour et al, 2006).

Prevalence of MRSA infection in Saudi Aramco

• A study conducted from 1999 to 2003 (J. Al-Tawfiq, 2006).

• A total of 5162 S. aureus isolates.

• MRSA constitutes 6% (308) of all isolates.

• Currently ~15%.

Who Gets MRSA

MRSA Colonization sites

• Nose/throat.

• Axilla.

• Groin.

• Wounds.

• IV access sites.

• Urinary catheter exit sites.

Transmission

• Direct person to person contact.

• Sharing of towels or personal hygiene items.

• Athletic equipment.

• Clothes.

• Drug use equipment.

• Contact sports.

• Food-borne.

Factors that Facilitate Transmission

Contaminated Surfacesand Shared Items

Cleanliness

Crowding

Compromised Skin

Antimicrobial Use

Frequent Contact

Practice of HCW

Hospital of Saint Raphael, New Haven, CT

http://www.handhygiene.org/

• A male infant suffering Pierre Robin syndrome. He was intubated and mechanically ventilated 4 days after birth. Because of respiratory insufficiency. A suspected respiratory tract infection (amoxicillin/clavulanic acid).

• Became bacteraemic after 3 days (amoxicillin and cefotaxime).

• Blood culture grew methicillin-susceptible S. aureus (MSSA) (flucloxacillin).

• He seemed to recover, but amoxicillin/clavulanic acid was reinstated for 10 more days on day 32 after the respiratory tract infection had recurred.

MRSA screening Options

• Microbiology culture.

• Molecular Testing.

Microbiology Culture

• Gold standard: sensitive but slow.

• 48 hr broth enrichment.

• Dedicated skilled lab personnel.

• Confirm identification and resistance

patterns of multiple colonies.

• Restricted to lab opening hours.

• Report final results in 48 - 120 hours (5 days).Good solution if it is not urgentGood solution if it is not urgent (e.g. elective surgery/planned hospital stay).

Why Utilize Molecular Testing

infection control and hospital epidemiology April 2010, vol. 31, no. 4

PAGE | 25

Raw Sample Prep

2 - 4 hours

PCR Amplification

1.5 - 2.5 hours

Fluorescence Detection

1 - 2 hours

Conventional PCR/ 1st generation rt-PCR

●Test-to-result time theoretically rapid 5h ●Labor-intensive●Dedicated skilled personnel

● Several separated lab rooms● Batch-testing required for cost-efficiency●Average time-to-report 36 h (24-72)

Molecular testing

• Cepheid GeneXpert® MRSA.

• Continuous and individual patient random access.

• Fully automated.

• All testing processes - sample preparation, real-time PCR amplification and detection - are performed in a closed single testing cartridge.

• Individual patient results in 5656 minutes.

• Very easy to implement.

• Can be performed “near-patient”.

Handling

56 minutes maximum

In House MRSA Validation Study• Analytical sensitivity (lower limit of detection) is 80

CFU/swab.

• Analytical specificity showed No cross-reactivity with other microorganisms and it cab be detected in mixed population.

• Comparative study included 51 clinical and volunteer samples. All results are correlated with Microbiology results.

Why we introduce GeneXpert MRSA in Saudi Aramco

• To reduce the turn around time (TAT) of MRSA result.

• To release the results within 120 minutes and our target is at least 90%.

Monitoring of Rapid MRSA Molecular assay results in Saudi Aramco

• A total of 1071 samples processed from October 15, 2008 to April 19, 2009. MRSA comprised (64) 6.4%

• Analysis of data obtain from laboratory information system (LIS) showed the following:

1. A total of 250 specimens were processed from Jan to Feb, 2009.

2. Nursing department 21% delay.

3. Lab triage section 17% delay.

4. From receiving to resulting 77% delay.

5. From ordering to resulting 77% delay.

6. Samples processed by techs 44-100% delay.

Time allocation for MRSA Sample Processing

1. Nursing department =10 minutes.

2. Lab triage section =10 minutes.

3. Molecular or Microbiology lab =100 minutes.

Monitoring of Rapid MRSA Molecular assay in Saudi Aramco

Month # of specimens

% results within 2 hours

% of results beyond 2 hours

Jan-Feb 09 250 23 77

March 09 195 53 47

April 09 161 75 25

May 09 164 69 31

Limitations of the assay

Increasingly, several reports about presence of SCC WITHOUT mecA

MRSA SCCmec True positive

S. aureus False positive

orfXmecA

orfXSCC

orfXmecA

Old versus New KitOld kit % old kit New Kit % New

KitNegative 552 78 453 71

Positive 134 19 50 8

Error 11 1.5 17 2.7

Invalid 2 0.3 61 9.6

No result 7 1 6 1

Total 706 634

Limitations• Mutations or polymorphisms in primer or probe binding regions

may affect detection of new or unknown MRSA variants resulting in a false negative result.

• Blood or mucus or both have been shown to cause inhibition in 4.2% of nasal swab specimens.

• A positive test result does not necessarily indicate the presence of viable organism.

• Therapeutic success or failure cannot be assessed using this test because DNA might persist following antimicrobial therapy.

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Summary

• MRSA is a global health problem.

• MRSA is transmitted easily between patients and HCWs and vice versa.

• Rapid molecular assay helps very effectively in infection control.

Thank you