ABCs Report: Methicillin-Resistant Staphylococcus aureus, 2010

June 6, 2012: Content on this page kept for historical reasons.

Active Bacterial Core Surveillance (ABCs): Emerging Infections Program Network

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ABCs Areas

California (3 county San Francisco Bay area); Colorado (5 Denver area county); Connecticut; Georgia (8 county Atlanta area); Maryland (Baltimore City and County); Minnesota (2 metro Twin City counties); New York (1 Rochester county); Oregon (3 county Portland area); Tennessee (1 Nashville county).

ABCs Population

The surveillance areas represent 19,154,389 persons.
Source: National Center for Health Statistics bridged-race vintage 2010 postcensal file.

ABCs Case Definition

Invasive methicillin-resistant Staphylococcus aureus (MRSA) disease: isolation of MRSA from a normally sterile site in a resident of the surveillance area in 2010. Cases of disease are classified into one of three epidemiologic classifications. A case is classified as hospital-onset (HO) if the MRSA culture was obtained on or after the fourth calendar day of hospitalization, where admission is hospital day 1; as healthcare-associated community-onset (HACO) if the culture was obtained in an outpatient setting or before the fourth calendar day of hospitalization and had one of more of the following: 1) a history of hospitalization, surgery, dialysis, or residence in a long term care facility in the previous year, or 2) the presence of a central vascular catheter (CVC) within 2 days prior to MRSA culture; and as community-associated (CA) if none of the previously mentioned criteria are met.

ABCs Methodology

ABCs personnel routinely contacted all microbiology laboratories serving acute care hospitals in their area to identify cases. Standardized case report forms that include information on demographic characteristics, clinical syndrome, and outcome of illness were completed for each identified case. Convenience samples of isolates were collected and sent to CDC for routine testing, including: antimicrobial susceptibility testing, toxin testing and SCCmec typing. Pulsed field gel electrophoresis (PFGE) of all isolates was discontinued in 2008; an inferred PFGE algorithm was developed based on microbiologic and molecular characteristics of isolates. The algorithm has been validated for use with isolates collected though this surveillance only. Regular laboratory audits were performed to ensure completeness of case detection.

Rates of invasive MRSA disease among all patients were calculated using population estimates for 2010. Cases with unknown race were assigned race based on distribution of known race and gender by EIP site. Confidence intervals for nationally estimated incidence rates of disease and mortality were calculated based on the gamma distribution (Stat Med, 1997 16:791-801). Rates of invasive MRSA disease among patients who are undergoing chronic dialysis treatment were calculated using the December 31, 2009 point prevalent counts of patients on dialysis from the United States Renal Data System (USRDS).

ABCs Results

ABC Racial/Ethnic Profiles

Race	No.	(Ratea)
White	3,034	(22.5)
Black	1,773	(48.2)
Other	187	(9.5)

Unknown race (n=524) distributed amongst known

^aCases per 100,000 population for ABCs areas (crude rates).

Reported Cases on Chronic Dialysis (n=973)

Dialysis and Access Type	No. (%)
Peritoneal	24 (2.5)
Hemodialysis	947 (97.5)
AV Fistula/Graft	361 (38..1)
CVC	558 (55.7)
Unkown	58 (6.1)

Distribution of cases, deaths and PFGE type by Epidemiological Classification

MRSA Class	No. (Rate) Casesb	No. (Rate) Deaths c	PFGE Type (N,%)d Tot N	PFGE Type (N,%)d USA100	PFGE Type (N,%)d USA300	PFGE Type (N,%)d USA500 Iberian
CA	868 (4.5)	66 (0.3)	276	59 (21.4)	176 (63.8)	10 (4.2)
HCAa	4,053 (21.2)	496 (3.1)	956	489 (51.2)	298 (31.2)	74 (7.7)
HCA-HO	970 (5.1)	206 (1.1)	228	134 (58.8)	57 (25.0)	16 (7.1)
HCA-HACO	3,083 (16.1)	390 (2.0)	728	355 (48.8)	241 (33.1)	58 (8.0)

^aHCA: Healthcare-associated invasive MRSA infections; sum of patients that are classified as either HO or HACO.
^bn=73; epidemiologic category unknown.
^cn=10; epidemiologic category unknown.
^disolates were eligible for testing at CDC

Reported Clinical Syndrome by Epidemiologic Class

Syndromea	CA (n=868)	HACO (n=3,083)	HO (n=970)
Bloodstream Infection with other syndrome	456	1,710	394
Bloodstream Infection with no other syndrome	174	920	342
Pneumonia	102	388	165
Lower Respiratory Infectionb	34	106	63
Osteomyelitis	123	385	93
Endocarditis	66	164	35
Cellulitis	163	289	75
Wounds - Surgicalc	13	214	45
Wounds - Decubitus/Pressure Ulcers	19	106	30
Other wounds/abscessesd	11	41	15
Traumatic Wounds	8	23	11

^aSome case patients had more than one syndrome.
^bLower Respiratory Infection is defined as: a patient with pneumonia documented in their discharge summary, who has a positive MRSA non-sterile respiratory specimen with accompanying chest radiology results documenting any of the following: bronchopneumonia/pneumonia, air space density/opacity, new or changed infiltrates.
^cCombines deep tissue/organ infection and infection of a surgical wound, post operatively.
^dCategory includes skin abscess, necrotizing fasciitis, gangrene, non-traumatic wounds.

Table data for this chart

National Estimates and Adjusted Incidence Rates of Invasive MRSA Infections

Epidemiologic Category	Estimated Cases of Infection
	Non-Dialysis Patients		Dialysis Patients		Total
	Estimated No.	Incidence Rate (Confidence Interval)a	Estimated No.	Incidence Rate (Confidence Interval)b	Estimated No.	Incidence Rate (Confidence Interval)
CA	13,799	4.47 (4.17-4.79)	0	0	13,799	4.47 (4.17-4.79)
HCA	51,300	16.68 (16.08-17.29)	15,734	3,950.52 (3,697.66-4,217.73)	67,034	21.76 (21.08-22.46)
HO	13,894	4.51 (4.20-4.83)	1,850	463.95 (379.75-563.07)	15,744	5.10 (4.78-5.44)
HACO	37,406	12.13 (11.62-12.66)	13,884	3,481.03 (3,244.23-3,732.17)	51,290	16.61 (16.02-17.23)
Overallc	66,312	21.51 (20.83-22.20)	15,730	3,943.86 (3,691.40-4,210.65)	82,042	26.57 (25.82-27.34)

^aNational Estimates and Incidence (no. per 100,000 population per year) are adjusted for age, race, gender, and receipt of dialysis treatment using 2010 US Census Data.
^bNational Estimates and Incidence (no. per 100,000 dialysis patients per year) for dialysis patients are adjusted for age, race and gender using 2009 USRDS point prevalence data.
^c73 cases could not be classified into an epidemiological category or category is unknown and therefore are counted in the overall estimate only.

National Estimates and Adjusted Incidence Rates for Mortality among Cases

Epidemiologic Class	Estimated No.	Mortality Rate (Confidence Interval)a
CA	665	0.22 (0.14-0.36)
HCA	10,202	3.31 (3.04-3.59)
HO	3,507	1.14 (0.98-1.31)
HACO	6,695	2.17 (1.95-2.40)
Overallb	11,478	3.73 (3.44-4.02)

^aNational Estimates and Mortality Rate (no. per 100,000 population per year) are adjusted for age, race, gender and receipt of dialysis treatment in the using 2010 US Census Data.
^b10 cases could not be classified into an epidemiological category or category is unknown and therefore are counted in the overall estimate only.

National Metric for Healthy People 2020 and the Department of Health and Human Services Action Plan to Prevent Healthcare-Associated Infections

	Disease Rate			Estimate of Cases in United States.a
	Baseline (07-08)	2010	% Change	Baseline (07-08)	2010	Difference
HCA	27.08	21.76	-19.7	82,000	67,000	15,000

^aDisease Rate (no. per 100,000 population per year) and National Estimates are adjusted for age, race, gender and receipt of chronic dialysis using 2010 US Census Data

ABCs Discussion

Surveillance data from 2010 represent the sixth full year of performing population-based surveillance for invasive MRSA infections through the Emerging Infections Program/Active Bacterial Core Surveillance Activity.

Overall, compared to the baseline incidence (2007-2008 calendar years) identified in the HHS Action Plan, there was a decrease of 19.7%.

Citation

1. Centers for Disease Control and Prevention. 2010. Active Bacterial Core Surveillance Report, Emerging Infections Program Network, Methicillin-Resistant Staphylococcus aureus, 2010.
2. Centers for Disease Control and Prevention. 2007. Invasive Methicillin-Resistant Staphylococcus aureus Infections Among Dialysis Patients --- United States, 2005. MMWR. 2007;56(09):197.

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