Diversity of methicillin-resistant Staphylococcus aureus strains isolated from residents of 26 nursing homes in Orange County, California.

Nursing homes represent a unique and important methicillin-resistant Staphylococcus aureus (MRSA) reservoir. Not only are strains imported from hospitals and the community, strains can be transported back into these settings from nursing homes. Since MRSA bacteria are prevalent in nursing homes and yet relatively poorly studied in this setting, a multicenter, regional assessment of the frequency and diversity of MRSA in the nursing home reservoir was carried out and compared to that of the MRSA from hospitals in the same region. The prospective study collected MRSA from nasal swabbing of residents of 26 nursing homes in Orange County, California, and characterized each isolate by spa typing. A total of 837 MRSA isolates were collected from the nursing homes. Estimates of admission prevalence and point prevalence of MRSA were 16% and 26%, respectively. The spa type genetic diversity was heterogeneous between nursing homes and significantly higher overall (77%) than the diversity in Orange County hospitals (72%). MRSA burden in nursing homes appears largely due to importation from hospitals. As seen in Orange County hospitals, USA300 (sequence type 8 [ST8]/t008), USA100 (ST5/t002), and a USA100 variant (ST5/t242) were the dominant MRSA clones in Orange County nursing homes, representing 83% of all isolates, although the USA100 variant was predominant in nursing homes, whereas USA300 was predominant in hospitals. Control strategies tailored to the complex problem of MRSA transmission and infection in nursing homes are needed in order to minimize the impact of this unique reservoir on the overall regional MRSA burden.

Diversity of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from inpatients of 30 hospitals in Orange County, California.

There is a need for a regional assessment of the frequency and diversity of MRSA to determine major circulating clones and the extent to which community and healthcare MRSA reservoirs have mixed. We conducted a prospective cohort study of inpatients in Orange County, California, systematically collecting clinical MRSA isolates from 30 hospitals, to assess MRSA diversity and distribution. All isolates were characterized by spa typing, with selective PFGE and MLST to relate spa types with major MRSA clones. We collected 2,246 MRSA isolates from hospital inpatients. This translated to 91/10,000 inpatients with MRSA and an Orange County population estimate of MRSA inpatient clinical cultures of 86/100,000 people. spa type genetic diversity was heterogeneous between hospitals, and relatively high overall (72%). USA300 (t008/ST8), USA100 (t002/ST5) and a previously reported USA100 variant (t242/ST5) were the dominant clones across all Orange County hospitals, representing 83% of isolates. Fifteen hospitals isolated more t008 (USA300) isolates than t002/242 (USA100) isolates, and 12 hospitals isolated more t242 isolates than t002 isolates. The majority of isolates were imported into hospitals. Community-based infection control strategies may still be helpful in stemming the influx of traditionally community-associated strains, particularly USA300, into the healthcare setting.

Differences in methicillin-resistant Staphylococcus aureus strains isolated from pediatric and adult patients from hospitals in a large county in California.

Studies of U.S. epidemics of community- and health care-associated methicillin-resistant Staphylococcus aureus (MRSA) suggested differences in MRSA strains in adults and those in children. Comprehensive population-based studies exploring these differences are lacking. We conducted a prospective cohort study of inpatients in Orange County, CA, collecting clinical MRSA isolates from 30 of 31 Orange County hospitals, to characterize differences in MRSA strains isolated from children compared to those isolated from adults. All isolates were characterized by spa typing. We collected 1,124 MRSA isolates from adults and 159 from children. Annual Orange County population estimates of MRSA inpatient clinical cultures were 119/100,000 adults and 22/100,000 children. spa types t008, t242, and t002 accounted for 83% of all isolates. The distribution of these three spa types among adults was significantly different from that among children (χ(2) = 52.29; P < 0.001). Forty-one percent of adult isolates were of t008 (USA300), compared to 69% of pediatric isolates. In multivariate analyses, specimens from pediatric patients, wounds, non-intensive care unit (ICU) wards, and hospitals with a high proportion of Medicaid-insured patients were significantly associated with the detection of t008 strains. While community- and health care-associated MRSA reservoirs have begun to merge, significant differences remain in pediatric and adult patient populations. Community-associated MRSA spa type t008 is significantly more common in pediatric patients.

Strain typing and antimicrobial resistance of fluoroquinolone-resistant Neisseria gonorrhoeae causing a California infection outbreak.

Antimicrobial-resistant Neisseria gonorrhoeae is an emerging public health problem as a result of the alarming limitation in treatment options. We examined an outbreak in California of fluoroquinolone-resistant Neisseria gonorrhoeae (QRNG) by evaluation of a combination of routine isolates from the Gonococcal Isolate Surveillance Project and isolates collected by expanded surveillance performed between April 2000 and June 2002. QRNG isolates were characterized by two methods: (i) determination of a combination of antibiogram, auxotype, serovar, Lip type, and patterns of amino acid alteration in the quinolone resistance-determining region of GyrA and ParC (ASLGP) and (ii) pulsed-field gel electrophoresis (PFGE). Strain typing was used to describe the QRNG outbreak strains and the associated antimicrobial resistance profiles. Among 79 isolates that were completely characterized, we identified 20 different ASLGP strain types, and 2 of the types were considered to belong to outbreak strains that comprised 65% (51/79) of the isolates. By PFGE typing, there were 24 different strain types, and 4 of these were considered outbreak types and comprised 66% (52/79) of the isolates. The overall agreement between the typing methods in distinguishing outbreak strains and non-outbreak strains was 84% (66/79). The most common QRNG ASLGP strain type had chromosomally mediated resistance to penicillin and tetracycline and an azithromycin MIC of 0.5 microg/ml. The occurrence of an outbreak caused by QRNG strains that could fail to be eradicated by most antibiotic classes reinforces the serious problem with antimicrobial resistance in Neisseria gonorrhoeae that the public health system faces. Adherence to a regimen with the recommended antibiotics at the appropriate dose is critical, and monitoring for antimicrobial susceptibility needs to be actively maintained to adapt treatment guidelines appropriately.

Reduction in turnaround time for laboratory diagnosis of pulmonary tuberculosis by routine use of a nucleic acid amplification test.

Every first diagnostic specimen from suspected patients with pulmonary TB was tested by a nucleic acid amplification test (NAAT) to determine the reduction in turnaround time (TAT) for detecting Mycobacterium tuberculosis (MTB) that was possible under normal laboratory operating conditions. NAAT (Gen-Probe Mycobacterium tuberculosis Direct Testtrade mark) was performed on the first specimen and liquid culture (BACTEC 460), solid culture (Lowenstein-Jensen [LJ] agar and selective 7H11 [7H11S] agar), and fluorescent acid-fast bacilli (AFB) smear were performed on all 3 specimens from each patient. Eighty-one (10.2%) of 797 patients tested were diagnosed with pulmonary TB. The sensitivity of NAAT, BACTEC, LJ, 7H11S, and smear for the first specimen was 90%, 85%, 67%, 53%, and 58%, respectively, whereas the sensitivity for the series of 3 specimens was 90%, 95%, 74%, 74%, and 70%, respectively. Positive predictive value was 100% for all tests except AFB smear, which was 79%. The time to detect 75% of all TB cases was 4 days for NAAT and 21 days for liquid culture; other tests had a sensitivity of less than 75%. Identification and testing every first diagnostic specimen by NAAT has the potential to reduce the overall TAT for laboratory TB diagnosis by approximately 2 weeks.