Transcript MRSA - VMC Foundation

MRSA Update 2013
David K. Hong, MD
Pediatrics/Infectious Diseases &
Immunology/Allergy
Santa Clara Valley Medical Center
Stanford University Medical School
Objectives
1. Review the increase in community-associated
MRSA infections in the last decade
2. Describe the unique infectious complications
in neonates
3. Discuss strategies for effective treatment and
prevention of MRSA infections
10 day old ex36wk male presents to urgent care clinic with this rash
Fortunov R M et al. Pediatrics 2007;120:937-945
What is MRSA?
Staphylococcus aureus
• Staphyle – “grape”; aureus – “gold”
– Coagulase positive
Staphylococcus aureus
• Staphyle – “grape”; aureus – “gold”
– Coagulase positive
• Coagulase-negative staph
are usually non-pathogenic
Staphylococcus aureus
• Staphyle – “grape”; aureus – “gold”
– Coagulase positive
• Coagulase-negative staph
are usually non-pathogenic
– Catalase positive
• Turns H2O2 into H20 and O2
Some definitions
MRSA – methicillin-resistant S. aureus
HA-MRSA – healthcare associated MRSA
- MRSA infection occurring within 12 months of
hospitalization
- Nosocomial infection
- Usually has multidrug resistance
CA-MRSA – community associated MRSA
- MRSA infection in the absence of healthcare exposure
- Associated with skin and soft-tissue infections (SSTI)
More definitions
SCCmec - Staphylococcal Cassette Chromosome mec or
SCCmec (I-V) is a resistance island or cassette in the
chromosome that encodes for methicillin resistance
Mec gene - Methicillin resistance: mec gene encodes
for production of penicillin binding protein 2A (PBP2A)
USA300 - Dominant CA-MRSA strain in U.S. causing
increase in SSTI
PVL – Panton Valentine Leukocidin
Panton Valentine Leukocidin
• Cytotoxin that causes white cell destruction
and tissue necrosis
• Commonly present in SCCmec type IV and V
(CA-MRSA strains)
• Can be also present in MSSA strains
• Associated with skin and soft tissue infections
and necrotizing pneumonia
• S. aureus has many other virulence factors
that may modulate infection
Committee on Infectious Diseases et al. Red Book Online
653-668
Evolution of Resistance
Drug
Year
Introduced
Time to R 25%R
Hospitals
25% R
Comm.
Penicillin
1941
1-2 yrs
6 yrs
15-20 yrs
Methicillin 1961
1 yr
25-30
40-50
Vanco
40 yr
?
?
1956
Chambers, HF EID 2001
Resistance
• Penicillin resistance: Gene for penicillin
resistance is carried on a plasmid
• Encodes for a penicillinase
• About 80-90% of S. aureus isolates are R to
penicillin
The -lactam ring
R=
Penicillin G (benzylpenicillin)
R
X
Cephalosporin
Staph
-lactamase
+
Clavulanate
Amoxicillin
MRSA
Methicillin-resistance is NOT due to a superpowerful -lactamase
mecA gene - PBP2a - altered penicillinbinding protein that has low affinity to lactams
MRSA Resistance
Peptidoglycan cell wall
Beta lactam abx
PBP2A
PBP
MLS Resistance Mechanisms
in S. aureus
Macrolides (e.g., erythromycin)
Lincosamides (e.g., clindamycin)
Streptogramin B
Protein
synthesis
erm
Methylase
msrA
Ribosome
Efflux pump
Macrolides
Lincosamides
Streptogramin B
Macrolides
A note about Clindamycin Resistance Testing
All politics is local…
About 20 – 40% of S. aureus is MRSA in our area
About 50 – 87% of MRSA is clindamycin sensitive
Rates of all Staphylococcus aureus infections, of methicillin-resistant S. aureus (MRSA)
infections, and of methicillin-susceptible S. aureus (MSSA) infections in 33 US children's
hospitals from 2002 to 2007.
Gerber J S et al. Clin Infect Dis. 2009;49:65-71
© 2009 by the Infectious Diseases Society of America
Staphylococcus aureus and MRSA
bacteremia/meningitis in NICUs
Shane AL et al, Pediatrics. 2012 Apr;129(4):e914-22
Clone USA300 is remarkably similar from different patients
Kennedy AD et al, PNAS 2008 Jan 29;105(4):1327-32
No difference in mortality
between MSSA and MRSA
Pathogenicity based on
virulence factors not
necessarily antibiotic
resistance patterns
Shane AL et al, Pediatrics. 2012 Apr;129(4):e914-22
MRSA Colonization
1/3 of people have S. aureus
in their nose
~2% carry MRSA
Risk factors for Colonization and Infection
•Very young children or
the elderly
•Athletes
•Lower SE
•Pet owners and
veterinarians
•Prisoners
•Nail biters
•Health care exposure
•Health care workers
•Race
Impact of methicillin-resistant Staphylococcus aureus (MRSA) colonization on risk of
subsequent infection in critically ill children.
Milstone A M et al. Clin Infect Dis. 2011;53:853-859
© The Author 2011. Published by Oxford University Press on behalf of the Infectious Diseases
Society of America. All rights reserved. For Permissions, please e-mail:
[email protected].
California state law SB 1058
- passed in 2008
- requires MRSA screening (nasal swab) for
following patients
- ICU admissions – including NICUs
- Inpatient hemodialysis patients
- patients discharged from general acute care
hospital within 30 ays of admission to SHC
- Transfers from a skilled nursing facility (SNF)
Overlap of nares, oropharynx, and inguinal colonization among the 542 Staphylococcus aureus–
colonized subjects from our total population of 1162 persons of households of persons with a recent
S. aureus skin infection.
Miller L G et al. Clin Infect Dis. 2012;cid.cis213
© The Author 2012. Published by Oxford University Press on behalf of the Infectious Diseases
Society of America. All rights reserved. For Permissions, please e-mail:
[email protected].
Infants with MRSA infection commonly have
mothers colonized with MRSA
MRSA colonization in neonates
25/35 (71%) case
4/19 (21%) control
Fortunov Pediatr Infect Dis J. 2011 Jan;30(1):74-6.
Infants with MRSA infection commonly have
mothers colonized with MRSA
MRSA colonization in moms
12/35 (34%) case
1/19 (5%) control
Fortunov Pediatr Infect Dis J. 2011 Jan;30(1):74-6.
Infants with MRSA infection commonly have
mothers colonized with MRSA
8/34 (24%) identical maternal
nasal and neonatal clinical
isolate
Fortunov Pediatr Infect Dis J. 2011 Jan;30(1):74-6.
Infants with MRSA infection commonly have
mothers colonized with MRSA
21/34 (62%) identical
neonatal nasal and neonatal
clinical isolate
Fortunov Pediatr Infect Dis J. 2011 Jan;30(1):74-6.
Infants with MRSA infection commonly have
mothers colonized with MRSA
6/25 (17%) identical maternal
nasal, neonatal nasal, and
neonatal clinical isolate
Fortunov Pediatr Infect Dis J. 2011 Jan;30(1):74-6.
Late-preterm, previously healthy male neonate with
CA S aureus localized groin pustulosis.
2001-2006 at Texas Children’s
Term and late-preterm <30 days
43 pustulosis – none had
invasive disease
68 cellulitis/abscess – 3 had
bacteremia or CSF pleocytosis
15 invasive infections
Fortunov R M et al. Pediatrics 2007;120:937-945
©2007 by American Academy of Pediatrics
Treatment of MRSA in Neonates
• IV Vancomycin
• Clindamycin or linezolid if a non-endovascular
infection
• For mild cases with localized disease: Topical
treatment with mupirocin may be adequate in
full term neonates and young infants.
What about Vancomycin?
• Don’t use it for MSSA infections – it does NOT
work as well as beta lactam antibiotics.
• Change to appropriate therapy as soon as
susceptibility data is available
Do not use Vancomycin for
Methicillin-sensitive S. aureus (MSSA)
Chang FY etl al, Medicine (Baltimore). 2003 Sep;82(5):333-9
Decolonization
• Nasal decolonization with mupirocin BID for 510 days
• Topical body decolonization with either
chlorhexidine for 5-14 days or bleach baths
(1/4 cup per ¼ tub). Bleach baths are given for
15 minutes semi-weekly for 3 months
Decolonization
• Systemic antibiotics are recommended for
treatment of active infection only
• Only in select circumstances is an oral antibiotic
plus rifampin recommended for decolonization
(CIII)
• If household transmission is suspected, personal
and environmental measures are recommended
for contacts.
Decolonization
• Systemic antibiotics are recommended for
treatment of active infection only
• Only in select circumstances is an oral antibiotic
plus rifampin recommended for decolonization
(CIII)
• If household transmission is suspected, personal
and environmental measures are recommended
for contacts.
Decolonization
• Shown to be effective in the short-term in
reducing nasal carriage of MRSA
• Re-colonization is common
• Rates of SSTI are still high even when
decolonized
Fritz SA et al, Infect Control Hosp Epidemiol. 2011 Sep;32(9):872-80
Decolonization regimens used in NICUs – unclear benefit
Milstone AM et al, Infection Control and
Hospital Epidemiology , Vol. 31, No. 7 (July
2010), pp. 766-768
Prevention - Hand washing works!
Pittet D et al, Lancet. 2000 Oct 14;356(9238):1307-12
Summary
• MRSA colonization and infection has been on the
rise in the community even without exposure to
healthcare facilities
• Both methicillin-resistant and –sensitive S. aureus
can cause similar disease due to the sharing of
virulence factors
• Patients colonized with S. aureus are more likely
to have S. aureus infections
• Decolonization can work in the short term but
the long-term effects are unknown