Methicillin-Resistant Staphylococcus aureus Infections in California Hospital Patients, 1999 – 2006

Mary Tran, PhD, MPHNiya Fong, BS Microbiology

California Office of Statewide Health Planning and Development

October 2008

Slide 2APHA Annual Meeting

October 2008

Presenter Disclosures

(1) The following personal financial relationships with commercial interests relevant to this presentation existed during the past 12 months:

Mary Nelson Tran, PhD, MPH

“No relationships to disclose”

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Issues

• Steep increase in MRSA rates in US hospital and long-term care patients.– Healthcare-associated MRSA (HA-MRSA)

• Evidence that MRSA is also spreading into the community (schools, gymnasiums)– Community-acquired MRSA (CA-MRSA)

• Some evidence that patients with MRSA infections cost more to treat and have higher mortality rates compared with non-resistant S.aureus infections.

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Methods• Data source:

– Hospital Patient Discharge Data, 1999, 2001, 2003, 2005, 2006.• Definition of MRSA infection:

– S. aureus infection in any diagnosis field of the PDD record:• Three ICD-9 codes are specific for S. aureus:

– 038.11 = S. aureus septicemia– 482.41 = S. aureus pneumonia– 041.11 = S. aureus infection in conditions classified elsewhere or of unspecified

site

– Methicillin resistance: • ICD-9 code = V09.0 in any secondary diagnosis field (1-24)

– MRSA Rate:• % S. aureus infection cases that are resistant• =(MRSA / all S. aureus infections) * 100

• Statistical analyses by SAS, ver. 9.1• Maps by ArcView

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Comparison of National MRSA Rates* with California Rates**

*Klein, et al, Emerg Inf Dis, Dec. 2007:13(12)1840-46. **Authors’ analysis

0

10

20

30

40

50

60

70

1999 2001 2003 2005

% S

. au

reu

s ca

ses

are

MR

SA

Total MRSA rate: National

Total MRSA rate: California

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Volume of Hospitalizations with S. aureus Infection, by Resistance

Type. California, 1999-2006

30,772 28,289 28,986 27,611 27,547

13,50422,008

36,625

52,209 54,317

-

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

1999 2001 2003 2005 2006

Vo

lum

e o

f S

.au

reu

s an

d M

RS

A H

osp

ital

izat

ion

s

MRSA

non-MR SA

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Hospital MRSA Rates by Age Group. California, 1999-2006

0

10

20

30

40

50

60

70

80

1999 2001 2003 2005 2006

% S.aureus

are

MR

SA

0-1718-6465+All Hospitalizations

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Hospital MRSA Rates by Source of Admission. California, 1999-2006

0

10

20

30

40

50

60

70

80

90

1999 2001 2003 2005 2006

% S

.au

reu

s a

re M

RS

A

HomeSNFGACAll Hospitalizations

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Percent of S. aureus Infections Reported as MRSA for Hospital Patients, California

1999 and 2006

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Trends in Length of Stay per Hospitalization, by Infection Type. California, 1999-2006

0

5

10

15

20

25

1999 2001 2003 2005 2006

Ave

rag

e le

ng

th o

f st

ay (

Day

s)

SA not resistant

MRSA

no SA reported

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Trends in Percent of Cases Discharged to Skilled Nursing and to Home,

by Infection Type. California, 1999-2006

0

5

10

15

20

25

30

35

1999 2001 2003 2005 2006

% D

isch

arg

ed t

o s

kill

ed n

urs

ing

non-MR S.aureus

MRSA

No S.aureus

0

10

20

30

40

50

60

70

80

90

1999 2001 2003 2005 2006

% D

isch

arg

ed

to

ho

me

non-MR S.aureus

MRSA

No S.aureus

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Trends in the Percent Died In-Hospital, by Infection Type. California, 1999-2006

0

2

4

6

8

10

12

14

16

18

1999 2001 2003 2005 2006

% C

ases

die

d in

-ho

spit

al

non-MR S.aureus

MRSA

No S.aureus

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Trends in Total and Daily Charges per Hospitalization, by Infection Type.

California, 1999-2006

$0

$20,000

$40,000

$60,000

$80,000

$100,000

$120,000

$140,000

$160,000

1999 2001 2003 2005 2006

Ave

rag

e to

tal

char

ge

for

ho

spit

aliz

atio

n

SA not resistant

MRSA

no SA reported

$0

$1,000

$2,000

$3,000

$4,000

$5,000

$6,000

$7,000

$8,000

$9,000

1999 2001 2003 2005 2006

Av

era

ge

ch

arg

e p

er

da

y o

f h

os

pit

ali

zati

on

SA not resistant

MRSA

no SA reported

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Limitations• This report is a conservative estimate of the volume and rate of

MRSA infection in California.– Only hospitalized cases are included. – Only S. aureus cases that were tested for antibiotic resistance and

reported as resistant could be counted as MRSA.

• Cases reported as “admissions from home” may include patients recently discharged from a hospital or long term care facility.

• These MRSA infections may or may not be cases of Healthcare Acquired Infections (HAI). The discharge records do not include sufficient information to identify which cases are HAI.

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Conclusions• California MRSA rate was lower than the overall US rate in 1999, but

surpassed it around 2003. – Hospital MRSA rate has risen in almost all counties

• Highest MRSA rates are found in patients who are: – Seniors and admissions from SNFs– But rates in other groups are catching up.

• For MRSA cases, in-hospital mortality and charges for care are declining.– Both trends may be related to MRSA patients’ shortened length of stay.

• MRSA rates for admissions from home are rising.– Does this indicate rising prevalence of Community-Acquired MRSA?

• Rates of MRSA discharges to home are rising.– Is there increased risk of spread of MRSA into the community?

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Acknowledgements

• Niya Fong: SAS analyses• Charlene Parham: Maps of MRSA rates

• MRSA electron micrograph. CDC/Janice Carr. http://www.cdc.gov/ncidod/dhqp/ar_MRSA_spotlight_2006.html.

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Questions