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SAN FRANCISCO — At hospital admission, 5%–7% of patients are colonized with methicillin-resistant Staphylococcus aureus, according to investigators at Evanston Northwestern Healthcare, the first hospital group in the United States to screen patients routinely for nasal carriage of the resistant bacteria.
It was not surprising that older patients, sicker patients, and patients on dialysis had the highest likelihoods of MRSA colonization, according to a case-control analysis using the data, Dr. Ari Robicsek said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
The prevalence of nasal carriage was 5% for patients in their 40s. Prevalence steadily increased with age to about 9% among patients in their 70s and peaked at 19% in patients 90 years or older, said Dr. Robicsek, the hospital epidemiologist for Evanston Northwestern Healthcare, which has three hospitals in the suburbs northwest of Chicago.
Over 24,000 patients have been screened by Dr. Robicsek's program, which began in August 2005.
The polymerase chain reaction (PCR) testing used to evaluate nasal carriage has been shown to have a sensitivity of 100% and a specificity of 98%, he said. The rates account for the variation in prevalence, considered to be 7% before and 5% after correcting for the specificity of the testing.
The association between nasal carriage of MRSA and being a sicker patient at admission was evident in the case-control analysis, which considered the number of ICD-9 codes a patient had on admission. The risk of being a MRSA carrier increased about 8% for each additional ICD-9 code.
Among adults who were admitted with a diagnosis of septicemia, the prevalence was 20%, Dr. Robicsek said.
Dr. Robicsek also found that MRSA carriage is difficult to eradicate. Fully 50% of the patients who had previously had a positive result on a nasal test or a clinical culture were carriers on readmission, compared with 4% of patients who had recently been tested or cultured and found to be negative.
Furthermore, patients who had had a prior history of a positive MRSAtest or infection, but had tested negative on their most recent test prior to admission, still had a 30% likelihood of being MRSA carriers on their readmission.
SAN FRANCISCO — At hospital admission, 5%–7% of patients are colonized with methicillin-resistant Staphylococcus aureus, according to investigators at Evanston Northwestern Healthcare, the first hospital group in the United States to screen patients routinely for nasal carriage of the resistant bacteria.
It was not surprising that older patients, sicker patients, and patients on dialysis had the highest likelihoods of MRSA colonization, according to a case-control analysis using the data, Dr. Ari Robicsek said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
The prevalence of nasal carriage was 5% for patients in their 40s. Prevalence steadily increased with age to about 9% among patients in their 70s and peaked at 19% in patients 90 years or older, said Dr. Robicsek, the hospital epidemiologist for Evanston Northwestern Healthcare, which has three hospitals in the suburbs northwest of Chicago.
Over 24,000 patients have been screened by Dr. Robicsek's program, which began in August 2005.
The polymerase chain reaction (PCR) testing used to evaluate nasal carriage has been shown to have a sensitivity of 100% and a specificity of 98%, he said. The rates account for the variation in prevalence, considered to be 7% before and 5% after correcting for the specificity of the testing.
The association between nasal carriage of MRSA and being a sicker patient at admission was evident in the case-control analysis, which considered the number of ICD-9 codes a patient had on admission. The risk of being a MRSA carrier increased about 8% for each additional ICD-9 code.
Among adults who were admitted with a diagnosis of septicemia, the prevalence was 20%, Dr. Robicsek said.
Dr. Robicsek also found that MRSA carriage is difficult to eradicate. Fully 50% of the patients who had previously had a positive result on a nasal test or a clinical culture were carriers on readmission, compared with 4% of patients who had recently been tested or cultured and found to be negative.
Furthermore, patients who had had a prior history of a positive MRSAtest or infection, but had tested negative on their most recent test prior to admission, still had a 30% likelihood of being MRSA carriers on their readmission.
SAN FRANCISCO — At hospital admission, 5%–7% of patients are colonized with methicillin-resistant Staphylococcus aureus, according to investigators at Evanston Northwestern Healthcare, the first hospital group in the United States to screen patients routinely for nasal carriage of the resistant bacteria.
It was not surprising that older patients, sicker patients, and patients on dialysis had the highest likelihoods of MRSA colonization, according to a case-control analysis using the data, Dr. Ari Robicsek said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
The prevalence of nasal carriage was 5% for patients in their 40s. Prevalence steadily increased with age to about 9% among patients in their 70s and peaked at 19% in patients 90 years or older, said Dr. Robicsek, the hospital epidemiologist for Evanston Northwestern Healthcare, which has three hospitals in the suburbs northwest of Chicago.
Over 24,000 patients have been screened by Dr. Robicsek's program, which began in August 2005.
The polymerase chain reaction (PCR) testing used to evaluate nasal carriage has been shown to have a sensitivity of 100% and a specificity of 98%, he said. The rates account for the variation in prevalence, considered to be 7% before and 5% after correcting for the specificity of the testing.
The association between nasal carriage of MRSA and being a sicker patient at admission was evident in the case-control analysis, which considered the number of ICD-9 codes a patient had on admission. The risk of being a MRSA carrier increased about 8% for each additional ICD-9 code.
Among adults who were admitted with a diagnosis of septicemia, the prevalence was 20%, Dr. Robicsek said.
Dr. Robicsek also found that MRSA carriage is difficult to eradicate. Fully 50% of the patients who had previously had a positive result on a nasal test or a clinical culture were carriers on readmission, compared with 4% of patients who had recently been tested or cultured and found to be negative.
Furthermore, patients who had had a prior history of a positive MRSAtest or infection, but had tested negative on their most recent test prior to admission, still had a 30% likelihood of being MRSA carriers on their readmission.