Many hospitals now seeing CA-MRSA in healthcare associated infections
Differences in Strains
Pulse field gel electrophoresis (PFGE) USA 100, 200 & 500
Panton valentine leucocidin (PVL) gene rare
More resistant to antibiotics
Pulse field gel electrophoresis (PFGE) USA 300, 400, 1000 &1100
PVL gene more common
Less resistant to abx
Clindamycin resistance developing in USA 300 strains
Susceptible to Clindamycin, Tetracyclines, and Bactrim
Genotypes of CA-MRSA
most common in US is clonal cluster ST-8 classified by the CDC as "USA 300."
CA-MRSA has a novel methicillin-resistance cassette element: type SCC mec IV, which has not been found in HA-MRSA isolates
CA-MRSA is more likely to encode for the Panton-Valentine leukocidin (PVL) toxin
virulence factor associated with severe necrotizing pneumonia and skin and soft-tissue infections.
Severe CA-MRSA – Not PVL
Most scientists believed the cause of severe CA-MRSA infection was Panton-Valentine leukocidin (PVL) toxin released by the organism
However, a study indicating that PVL does not play a major role in CA- MRSA infections was published in 2006
Question: what does????
Reference: J Voyich et al. Is Panton-Valentine leukocidin the major virulence determinant in community-associated methicillin-resistant Staphylococcus aureus disease? The Journal of Infectious Diseases 194(12), 2006
Phenol Soluble Modulin Protein
Newly described proteins in CA-MRSA
members of the phenol-soluble modulin (PSM) protein family
CA-MRSA strains attract and then destroy protective human white blood cells
eliminates immune defense mechanisms
production of the protein was typically higher in CA-MRSA strains
Release Panton Valentine Leukocidin virulence toxin to destroy tissue
Identification of novel cytolytic peptides as key virulence determinants of community-associated MRSA. Wang, Otto et al. Nature Medicine 2007 Nov 11 epub.
In 1996, the first clinical isolate - Japan
In June 2002, Vancomycin Resistant Staph aureus (VRSA) isolated from a intravenous catheter site
Michigan resident aged 40 years with diabetes, peripheral vascular disease, and chronic renal failure
It contained the Van A resistance gene – from VRE
vanA in this VRSA - acquired through exchange of genetic material from the vancomycin-resistant enterococcus also isolated from the swab culture
MMWR July 5, 2002 / 51(26);565-567
New, lethal MRSA strain emerges……
A new strain of methicillin-resistant Staphylococcus aureus (MRSA) is emerging
Researchers with Henry Ford Hospital say the USA600 strain is partially immune to vancomycin
Half of the USA600-infected patients in the study died within a month, a death rate five times that of those infected with known MRSA strains. (Ordinarily, 11 percent of patients infected with MRSA die within 30 days)
Factor may be age - those with the strain were, on average, 64 years old, as compared with 52 years old for other MRSA-infected people.
Source: Presentation at the Infectious Diseases Society of America, October 29, 2009
Populations at Risk for CA-MRSA
CA-MRSA do not have the usual risk factors associated with nosocomial MRSA.
Populations at greater risk include:
children and day care centers
persons in correctional facilities
Sports: football, basketball, baseball,
wrestlers, fencing, soccer
injection drug users
Pets can carry MRSA
German woman - multiple deep abscesses
Strain of drug-resistant MRSA
Cured after the family's cat was tested and treated.
Husband and two children carriers of MRSA
Treated and tested negative, she still was infected
Three apparently healthy cats screened
One tested positive for MRSA
4 weeks after the cat was treated with antibiotics, the woman was also free of MRSA
"We conclude that pets should be considered as possible household reservoirs of MRSA that can cause infection or reinfection in humans ” .
Source: March 13 2007, New England Journal of Medicine
MRSA Skin/Soft Tissue
NEJM – August 17, 2006
Emergency departments in 11 university-affiliated August 2004
Researchers enrolled adult patients with acute, purulent skin and soft-tissue infections
MRSA found to be the most common causative agent
S. aureus was isolated from 320 of 422 patients (76%) with skin and soft-tissue infections, with the prevalence of MRSA being 59% overall.
MRSA coverage when antimicrobial therapy is needed for the treatment of skin and soft-tissue infections
Risk Factors for Acquiring HA-MRSA
Break in natural skin barrier:
Surgery – especially implants
Invasive devices and procedures
Overuse of antibiotics
Patients with co-morbidities
obesity, diabetes, steroids
Contaminated shared equipment
Contaminated hands of healthcare workers – especially if presence of contact dermatitis and other skin conditions
Staph aureus Colonization
Colonization: Staph bacteria are present on or in the body without causing illness.
Approximately 25 to 30% of the population is colonized in the nose with sensitive Staph aureus at a given time
NEBH is finding 23% are colonized
~2-10% general population colonized with MRSA
NEBH is finding 5% are colonized
~0.9%-13.2% healthcare workers are colonized with MRSA
Higher rates in prison (~10%), among drug users, day care centers, professional sports teams and high schools
Once colonized for more than three months, it becomes much more difficult to clear
Rate of MRSA and MSSA in Surgeons and Residents
Schwarzkopf, et al: MRSA and MSSA in nares of physicians at the Hospital for Joint Diseases in New York.
Ran Schwarzkopf, Richelle C. Takemoto, Igor Immerman, James D. Slover, and Joseph A. Bosco Prevalence of Staphylococcus aureus Colonization in Orthopaedic Surgeons and Their Patients: A Prospective Cohort Controlled Study J Bone Joint Surg Am. 2010;92:1815-1819
74 surgeons and 61 residents screened
Surgeons: MRSA 2.7% and MSSA 23.3%
Residents: MRSA 0% and MSSA 59%
Control Group of Patients: MRSA 2.17% and MSSA 35.7%
Previous studies - 3% of MRSA outbreaks are caused by asymptomatic colonized health-care workers.
Vonberg RP, Stamm-Balderjahn S, Hansen S, Zuschneid I, Ruden H, Behnke M, Gastmeier P. How often do asymptomatic healthcare workers cause methicillin-resistant Staphylococcus aureus outbreaks? A systematic evaluation. Infect Control Hosp Epidemiol. 2006;27:1123-7
Higher Rate of Infection if Colonized
Colonized patients have a 30-60% risk of infection following colonization.
Host factors influence the onset of infection.
Immunosuppression, steroids, diabetes, invasive devices and procedures, surgery, skin breakdown, pneumonia, obesity, hematoma, etc.
Reference: Graham P, Lin S, Larson E (2006). "A U.S. population-based survey of Staphylococcus aureus colonization". Ann Intern Med 144 (5): 318-25.
Antimicrobial Agents for Treating MRSA
Systemic/PO Topical Decolonization
Vancomycin Chlorhexidine body was
Clindamycin 2% Mupirocin ointment
Zyvox (Linezolid)IV or po
New Antibiotics for MRSA
ETX1153 ( e-Therapeutics plc) found to be highly potent against the most common epidemic strain of MRSA in the UK ( EMRSA-16) and effective against V.I.S.A. strains
Platensimycin (Merck) blocks the enzymes that produce fatty acids - essential for the construction of the membranes of bacteria – still under investigation
Daptomycin (Cubist) can be used in combination regimens when infection with a gram-negative or anaerobic organism is either suspected or confirmed. This drug's action is rapidly bactericidal.
Linezolid (Zyvox) is active against gram-positive organisms, such as VRE and MRSA
MRSA is transmitted by:
Direct Contact with body fluids, skin, secretions, excretions – during patient care and procedures, during sports, in close quarters
Indirect contact by contaminated inanimate objects – such as BP cuffs, oximeter sensors, thermometers, environment, contaminated hands, stethoscopes, otoscopes, commodes, bedside curtains, towels, locker rooms, prisons, toys in daycare
Outbreaks in Sports Teams
An outbreak of methicillin resistant Staphylococcus aureus infection in a rugby football team. British Journal of Sports Medicine, Vol 32, Issue 2 153-154, 1998
Methicillin-Resistant Staphylococcus aureus in a High School Wrestling Team and the Surrounding Community Arch Intern Med. 1998;158:895-899.
Cutaneous Community-acquired Methicillin-resistant Staphylococcus aureus Infection in Participants of Athletic Activities. Southern Medical Journal. 98(6):596-602, June 2005.
National Athletic Trainers' Association, Inc.Outbreak of Community-Acquired Methicillin-Resistant Staphylococcus aureus Skin Infections Among a Collegiate Football Team. J Athl Train. 2006; 41(2): 141 – 145.
CA-MRSA in Sports Teams
Toronto Blue Jays
San Francisco Giants
Dutch Soccer Team
Many high school football teams
Sources for Transmission
Hands number one!
Close contact sports
Cuts, abrasions and bruises – wound care
Bandages, soiled towels
Locker rooms, Jacuzzi, hot tub
Benches, chairs, exercise equipment
Sharing items: towels, razors, drinks, weights, bikes, etc.
Prevention: Wash and Sanitize Alcohol Foam, Liquid and Hand Wipes At NEBH all patients admitted receive package of alcohol wipes In each patient room, outside rooms, cafeteria and other areas Wash hands often – before eating, before leaving work, after contamination, after bathroom
MRSA Patient Rooms
Brigham and Women ’ s Hospital - environmental contamination and the accompanying relative odds of infection acquisition.
Newly-admitted patients housed in a room in which the most recent occupant was MRSA-positive or VRE-positive, “ significantly increased the odds of acquisition ” for a MRSA-related or VRE-related infection.
3.9 percent of new patients acquired an infection.
4.5 percent acquired a VRE infection.
Huang SS, Datta R, Platt R. Risk of acquiring antibiotic-resistant bacteria from prior room occupants. Arch Intern Med. 2006 Oct 9;166(18):1945-51.
MRSA contamination in precaution rooms
Ref: Boyce, Infec Cont Hosp Epid 1977
70% of rooms had environmental contamination when the patient was colonized or infected
42% of nurses’ gloves cultured were contaminated after touching environmental surfaces WITHOUT touching the patient!
Ref: Boyce, et. Al. SHEA 1998 Abstract
Results: 14 (40%) of 35 HCWs gowns were culture + for MRSA on exiting room. Clothing underneath was negative. 11 (69%) of 16 HCWs wearing freshly laundered lab coats had detectable contamination. 3 of 11 developed positive hand cx after touching the coat.
Institutional Prescreening for Detection and Eradication of Methicillin-Resistant Staphylococcus aureus in Patients Undergoing Elective Orthopaedic Surgery J Bone Joint Surg Am. 2010;92:1820-1826
David H. Kim, Maureen Spencer, Susan M. Davidson, Ling Li, Jeremy D. Shaw, Diane Gulczynski, David J. Hunter, Juli F. Martha, Gerald B. Miley, Stephen J. Parazin, Pamela Dejoie, and John C. Richmond
February 2006 Anonymous Nares Cultures
Obtained nasal cultures
Purpose: to determine pre-op
MRSA and MSSA colonization
38 – Staph aureus (29%)
*5 - MRSA ( 4%)
*all undiagnosed and no precautions used in OR or postop nursing unit
Decolonization Treatment Protocol
5-day application of intranasal 2% mupirocin - applied twice daily - for MRSA and Staph aureus positive patients.
Daily body wash with chlorhexidine
MRSA Patients - Vancomycin surgical prophylaxis
What were the outcomes?
MRSA/MSSA Eradication Results
From July 17, 2006 through July 2010
25,025 patients screened
5770 (23%) positive for Staph aureus
1027 ( 4%) positive for MRSA
Repeat nasal screens on MRSA patients
revealed 78% eradication
Time Period Inpatient surgeries # Surgical Infections % MRSA/MSSA
10/01/05-07/16/06 5293* 24 0.45%
07/17/06-09/30/07 7019 6 0.08%
10/01/07-09/30/08 6323 7 0.11%
10/01/08-09/30/09 6364 11 0.17%
10/01/10-07/31/10 5397 5 0.09%
% MRSA and Staph aureus SSI
MRSA is increasing in the community and in hospitals
Overuse of antibiotics has created some of the problem
Resistance among the species is a factor in resistance
Close quarters, equipment, environments and contaminated hands are sources for transmission
Limited antibiotics available to treat MRSA
Pre-surgical screening program is an effective method of detection for treatment and precautions