Ali Rabaan - saudi aramco medical servicesPresentation Transcript
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
History of MRSA and Antibiotics.
Why We Worried About It.
Factors Enhance the Emergence and Transmission.
Impact of Molecular Testing on Infection Control.
Molecular Testing of MRSA.
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.
Hospitalization and supportive care.
Increased use of:
Laboratory and diagnostic tests.
Infection control procedures.
More expensive antimicrobials
(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.
Who Gets MRSA Anyone can get MRSA!
MRSA Colonization sites
IV access sites.
Urinary catheter exit sites.
Direct person to person contact.
Sharing of towels or personal hygiene items.
Drug use equipment.
Factors that Facilitate Transmission Contaminated Surfaces and Shared Items Cleanliness Crowding Compromised Skin Antimicrobial Use Defense Offense 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
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 urgent (e.g. elective surgery/planned hospital stay).
Why Utilize Molecular Testing
infection control and hospital epidemiology April 2010, vol. 31, no. 4
All testing processes - sample preparation, real-time PCR amplification and detection - are performed in a closed single testing cartridge.
Individual patient results in 56 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:
A total of 250 specimens were processed from Jan to Feb, 2009.
Nursing department 21% delay.
Lab triage section 17% delay.
From receiving to resulting 77% delay.
From ordering to resulting 77% delay.
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
orfX mecA orfX SCC orfX mecA
Old versus New Kit Old kit % old kit New Kit % New Kit Negative 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
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.
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.