Wednesday, March 19, 2008

ICEID 2008 Methicillin-Resistant Staphylococcus aureus MRSA

Methicillin-Resistant Stapylococcal Infections

Trends in Invasive Infection with Methicillin-resistant Staphylococcus
aureus (MRSA) in Connecticut, 2001-2006

S. Petit1, Z. Fraser1, M. Mandour2, J. L. Hadler1; 1Connecticut Department
of Public Health, Hartford, CT,
2Connecticut Department of Public Health Laboratory, Hartford, CT.

Background: In 2007, CDC published an article that described the epidemiology of invasive
MRSA infections in 2004-05 in 9 sentinel sites, including Connecticut (CT). The CT system has been in place since 2001 and provides an opportunity to examine trends in the 3 major groupings of MRSA by place of onset and relationship to healthcare: hospital-onset (HO) vs. community-onset but healthcareassociated (HA) or community-associated (CA) MRSA. Methods: Cases identified from laboratory reporting of MRSA isolates from normally sterile body sites were classified after medical record review as HO (isolate >2 days after hospital admission), HA (hospital admission, surgery, dialysis, or long-term care facility stay in the past year, a history of MRSA, or an indwelling device); or CA (by exclusion). A systematic sample of blood isolates were typed by pulsed-field gel electrophoresis (PFGE). Results: In
2001-2006, 5464 cases of invasive MRSA were reported; 34.5% HO, 58.9% HA and 6.6% CA. Annual incidence overall (26.2 per 100,000) and of HA-MRSA (15.4) was stable. However, incidence of HOMRSA decreased (10.0 to 7.6) while CA incidence increased (1.1 to 2.8, p<0.01 p="0.02)." p =".049,"> 1 hospitalization (80%, [268/335] vs. 63% [245/390], P <.0001) and had > 2 infections (33%, [110/335]) vs. 23% [88/390], P =.002) respectively. There were twice as many deaths during the 6-month follow up period among patients with MRSA infection (24%,
79/335) as among patients with MSSA infection (12% 45/390, OR 2.4, 95% CI 1.6-3.5, P < .0001). After adjustment for age and CH-IND, this difference remained significant (OR 1.9, 95% CI 1.2-2.9, P =.005). There was clinical evidence that SA infection caused or clearly contributed to death in 28% (35/124) of all deaths; 7% (25/335) among those with MRSA infection and 3% (10/390) among those with MSSA infection. After adjustment for age, those with MRSA infection were almost 3 times more likely than those with MSSA infection to die of SA disease (OR 2.8, 95% CI 1.3-6.0, P =.007). Conclusions: In this patient population, methicillin resistance was associated with a greater risk of death attributable to SA disease and to death from any cause. MRSA infections were more common among those with chronic illnesses. Optimal methods of prevention and treatment of healthcare-associated SA, particularly MRSA infections, are urgently needed. Community-Associated (CA) Methicillin-Resistant Staphylococcus aureus (MRSA) in Affected Households: Prevalence of Colonization and Incidence of Subsequent Infections J. M. Buck1, R. Gorwitz2, R. Lynfield1, K. Harriman3; 1Minnesota Department of Health, Saint Paul, MN, 2Centers for Disease Control and Prevention, Atlanta, GA, 3California Department of Public Health, Richmond, CA. Background: MRSA has emerged as a community pathogen over the last decade. Several reports indicate that CA-MRSA infections can occur among multiple household members (HHMs). We describe MRSA colonization prevalence and subsequent infection incidence among children with CAMRSA infections and their HHMs. Methods: MRSA infections in children <18 p =" 0.03)," p =" 0.03)."> 0.05). Conclusions: The prevalence of MRSA colonization in affected HHs did not decrease during the study period; over 20% of HHs had at least one colonized HHM one year after initial CP infection. Use of mupirocin did not appear to affect long term MRSA colonization or infection in HHs. Behavior modifications (e.g. not sharing personal items) may be more important in reducing MRSA transmission. Additional strategies to prevent CA-MRSA infection and transmission in HHs should be evaluated.

Detection of Community Acquired Methicillin Resistant Staphylococcus aureus
Associated with Nosocomial Infections

S. M. Tallent, D. M. Toney; Virginia Division of Consolidated Laboratory
Services, Richmond, VA.

Background: Staphylococcus aureus is a human commensal that has emerged as a significant
pathogen due to the production of a variety of virulence factors and acquisition of numerous antimicrobial resistant genes. Methicillin resistant S. aureus (MRSA) is an antimicrobial resistant strain traditionally associated with hospital infections, but is now increasingly associated with illness in typically healthy individuals outside healthcare facilities. Pulsed-field gel electrophoresis (PFGE) genotyping of staphylococcal isolates by the CDC categorized MRSA strains into two groups, community-acquired methicillin resistant S. aureus (CA-MRSA) and hospital-acquired methicillin resistant S. aureus (HAMRSA). The two groups clustered into ten lineages which were designated as pulsetypes USA100- USA1100. More recently, distinctions between HA-MRSA and CA-MRSA have become less apparent, presumably due to recombination events giving rise to new MRSA strains that differ from the USA pulsetypes. Methods: S. aureus isolates from previous hospital and community outbreaks occurring in
Virginia as early as 1997 were subjected to PFGE genotyping, generating a DNA fingerprint database at the Division of Consolidated Laboratory Services (DCLS), the Virginia state laboratory. Archived isolates from 2005-2007 (N=258) were compared to the prototype USA fingerprint patterns and classified based on pattern similarities. Clusters of isolates possessing >80% similarity to the USA pulsetypes were further evaluated. Results: Forty percent of the 258 MRSA isolates examined clustered with USA100, the most common HA-MRSA pulsetype. Of these strains, 23% were associated with community outbreaks not hospital infections based on epidemiologic investigations. In contrast, 22% of the 258 isolates clustered with USA300, the most common CA-MRSA pulsetype. Of these, 88% were previously determined to be
associated with nosocomial infections. Conclusions: This study has identified a subset of MRSA strains designated as outliers based on PFGE pulsetype patterns and epidemiology. Additional molecular characterization is ongoing to understand these findings, determine if this is a representative trend in Virginia and whether the most invasive form of MRSA has become endemic to Virginia’s healthcare facilities.

Board 7. Community-Associated Methicillin-Resistant Staphylococcus aureus
Infection Risk Factor Study

K. Como-Sabetti1, K. Harriman2, S. Fridkin3, R. Lynfield4; 1Minnesota Department of Health, Minneapolis, MN, 2California Department of Public Health, Richmond, CA, 3Centers for Disease Control and Prevention, Atlanta, GA, 4Minnesota Department of Health, Saint Paul, MN.

Background: Little is known about risk factors for methicillin-resistant Staphylococcus aureus (CA-MRSA) infection in non-outbreak settings. Methods: MN Department of Health initiated a hypothesis-generating CA-MRSA case control study in 2003. 150 patients with S. aureus infections, including both CA-MRSA and CA methicillinsensitive SA (MSSA), were identified by 3 sentinel labs. 2-3 age-group matched healthy community controls (CC) were identified by sequential digit dialing. Participants were interviewed about possible risk factors and an antibiotic history was obtained from healthcare providers. Univariate and multivariate conditional logistic regression were conducted using SAS for 3 separate analyses to avoid biased estimates: CA-MRSA cases vs. CA-MSSA cases, CAMRSA cases vs. CA-MRSA CCs, and CA-MSSA cases vs. CA-MSSA CCs.Results: 75 CA-MRSA and CA-MSSA cases and 438 CCs were enrolled. Antibiotic use in the prior 1-6 months (recent ABX) was more frequent among CAMRSA cases than CA-MSSA cases or CCs (33% vs. 17% vs. 14%). History of boils was infrequent (10% CA-MSSA, 1% CA-MSSA, 1% CCs). Race, education, income, household members per room, dog in the home, history of boils, and towel sharing were associated with CA-MRSA when compared to CA-MSSA or CA-MRSA CCs. Recent ABX and number of recent ABX courses were associated with CA-MRSA when compared to CA-MSSA cases (p=0.03;
OR=2.5, and p<0.01; OR=2.2 respectively) and persisted when compared to CA-MRSA CCs (p=0.05; OR=2.3, and p=0.02; OR=1.9 respectively), but were not associated with CA-MSSA cases compared to CA-MSSA CCs. After adjusting for socioeconomic factors, history of boils was associated with CA-MRSA compared to CA-MSSA (p=0.002; AOR=76.8) but not when compared to CA-MRSA CCs. Recent ABX and ABX courses were associated with CAMRSA compared to CA-MSSA (p=0.02, AOR=1.9, and p=0.01, AOR=2.2 respectively) and compared to CA-MRSA CCs (p=0.05, AOR=2.4, and p=0.02 and AOR = 1.9 respectively). Conclusions: In non-outbreak settings, antibiotic use and history of boils (which may be a proxy for prior CA-MRSA skin disease) appear to be risk factors for CAMRSA. Further investigation of antibiotic use and specific antibiotic classes is needed. Although not definitive, this study reinforces the importance of careful antibiotic stewardship.

Board 83. Critical or Fatal Illness Due to Community-associated Staphylococcus aureus (CA-SA) Infection, Minnesota (MN), 2005-2007

Page 121 of 262 L. Lesher1, J. Buck1, J. Bartkus1, S. Jawahir1, D. Boxrud1, K. Harriman2, R. Lynfield1; 1Minnesota Department of Health, Saint Paul, MN, 2California Department of Public Health, Richmond, CA.

Background: CA-SA infections have been associated with critical illness and death. Methods: Reporting for rapidly fatal or critical illness due to CA-SA infection, including isolate collection, was instituted statewide in MN in 2005. Cases were defined as previously healthy people who had fatal illness or ICU admission and no healthcareassociated (HA) MRSA risk factors per CDC definition, excluding hospitalization for birth. Isolates were characterized by pulsed-field gel electrophoresis (PFGE) and PCR for toxic shock syndrome toxin 1 (TSST1), Panton-Valentine leukocidin (PVL), and staphylococcal enterotoxin (SE) genes A, B, C, D. Results: 32 cases were reported January 2005 through October 2007; 21 (66%) methicillin-resistant SA (MRSA) and 11 (34%) methicillin-susceptible SA (MSSA) cases. 14 (67%) MRSA cases were male; median age, 17 years (12 days-88 years), and 5 (45%) MSSA cases were male; median age, 18 years (1 day-59 years). Two cases had multifocal infections; MRSA with pneumonia and septic arthritis; MSSA with meningitis, lumbar wound, pneumonia (fatal). Of MRSA cases, 11 (52%) had pneumonia (3 fatal), 5 (24%) had skin infections (4 bacteremic - 1 fatal; 1 necrotizing fasciitis - fatal), 2 (9%) had sepsis (1 fatal), 1 (5%) had meningitis, 1 (5%) had osteomyelitis. Of MSSA cases, 4 (36%) had pneumonia (2 fatal), 2 (18%) had skin infections with bacteremia, 2 (18%) had TSS, 1 (9%) had meningitis (fatal), 1 (9%) had sepsis. The median age of fatal cases was 58 years for MRSA, 27 years for MSSA. PFGE typing and toxin PCR were performed on 17 MRSA and 7 MSSA isolates. All MRSA isolates belonged to clonal groups associated with CAMRSA; USA300 (15), USA400 (1), USA1000 (1). MSSA isolates were found in groups associated with CA and HAMRSA; USA200 (1), USA400 (1), USA600 (2), USA700 (1), USA1000 (2). Among MRSA, toxin PCR found PVL in 14 USA300 isolates (2 fatal) and 1 USA400 (fatal), which also had SEA and SEC. Among MSSA, SEB was found in 1 USA1000 isolate (fatal) and TSST1 in 1 USA200 (clinical TSS), and 2 MSSA isolates from fatal cases were negative for all toxins tested. Conclusions: Most critical/fatal CA-SA reported cases were MRSA. A high fatality rate was observed in cases with meningitis or pneumonia. Fatal MRSA cases were older than MSSA cases. Most isolates contained toxins previously implicated in severe disease. Molecular

Epidemiology Board 109. Staphylococcal Cassette Chromosome mec (SCCmec) Characterization and Panton-Valentine Leukocidin Gene Occurrence for Methicillin-Resistant Staphylococcus aureus in Turkey, from 2003 to 2006

A. Kilic, A. Uskudar Guclu, Z. Senses, H. Aydogan, A. C. Basustaoglu; Gulhane Military Medical Academy, Ankara, TURKEY.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) cause serious community-acquired and nosocomial diseases all over the world. Methods: We determined the SCCmec types and occurrence of the PVL gene by using TaqMan real-time PCR method, and correlated these with phenotypic antibiotic susceptibility patterns for MRSA strains collected from Gulhane Military Medical Academy Hospital (GMMAH) during four years study period. To our knowledge, this is the first report from Turkey of molecular SCCmec typing analysis of MRSA stains. From 2003 through 2006, a total of 385 clinical MRSA strains were collected in the Clinical Microbiology Laboratory at GMMAH were included in the study. Results: Overall, SCCmec types-I, II, II, IV, V, nontypeable and PVL occurrence were detected in 11 (2.8%), 3 (0.8%), 316 (82.1%), 20 (5.1%), 20 (5.1%), 15 (3.9%) and 5 (1.3%) isolates, respectively. A total of 330 (85.5%) were SCCmec-I/II/III, and of 40 (10.3%) were SCCmec-IV/V. SCCmec-I/II/III isolates were recovered more from serious infections in surgical departments especially having intensive care units than the SCCmec-IV/V isolates (?2=13.560, p<0.001). SCCmec-I/II/III MRSA strains were predominantly recovered from the blood stream as 53.0% (?2=6.016, p=0.014), while SCCmec-IV/V strains were predominantly isolated from skin, soft tissue and abscess as 55.0% (?2= 11.025, p<0.001). The PVL gene was detected in 10.0% of SCCmec- IV/V isolates in contrast to 0.3% in SCCmec-I/II/III (?2= 25.164, p<0.001). SCCmec-I/II/III MRSA strains were more resistant to clindamycin (?2=5.078, p=0.024), amoxicillin-clavulanate (?2=84.912, p<0.001), erythromycin (?2=4.651, p=0.031), gentamicin (?2=24.869, p<0.001), and rifampin (?2=18.878, p<0.001) than SCCmec-IV/V MRSA strains. Conclusions: These data indicate that SCCmec-III MRSA strains not to carrying PVL gene are the predominant MRSA strains in our hospital settings in Ankara, capital of Turkey. SCCmec-I/II/III MRSA strains may cause serious infections in surgical department especially having intensive care units.

Board 227. Staphylococcus aureus and Methicillin Resistant Staphylococcus aureus on surfaces in a University and a Jail Setting

M. Felkner1, K. Bartlett2, K. Andrews2, L. Field2, J. Taylor1, T. Baldwin1, J. Presley2, J. Duncan2, S. Newsome1; 1Texas Department of State Health Services, Austin, TX, 2The University of Texas at Austin, Austin, TX.

Background: Longtime pathogen Staphylococcus aureus has become more threatening with its evolution of antibiotic resistance, particularly the emergence of methicillin resistance outside health care settings. Commonly touched surfaces may harbor methicillin resistant S. aureus (MRSA) and be possible reservoirs of organisms facilitating disease transmission in the community. This study provides information regarding the presence of MRSA on commonly touched objects in both a university and a jail setting. Methods: University surface samples were obtained from bathrooms, common use areas, and recreational and sports facilities. Samples were collected at the jail from bathrooms, cells, common use areas, the clinic, laundry, and vehicles. Samples were collected using sterile, cotton-tipped swabs. Specimens were screened for S. aureus and MRSA using standard media. Susceptibility was determined using the ETest strip. Percentages of contaminated surfaces were calculated and chi-square comparisons were made between university and jail settings. Results: Seventeen (7.0%) of 244 university samples and 10 (7.5%) of 132 jail samples grew S. aureus. MRSA was recovered from 3 (1.2%) university samples, constituting 17.6% of S. aureus samples. Eight (6.1%) jail samples were MRSA, comprising 80% of jail S. aureus samples. The proportion of MRSA-contaminated surfaces and the ratio of MRSA to methicillin susceptible S. aureus were significantly greater at the jail that at the university (p<0.05). Conclusions: Our results indicate that environmental contamination with MRSA may be positively correlated with the carriage rate within the population. Page 191 of 262 Implementation of environmental sanitation should be of particular concern in populations with high MRSA nasal carriage rates.

Board 264. 30-Day and 180-Day Case Fatality Rates among Invasive Methicillin-Resistant Staphylococcus aureus Patients (Tennessee, 2004–2007)

K. R. Glenn, M. A. Kainer; Tennessee Department of Health, Nashville, TN.

Background: Tennessee had the second highest incidence of invasive MRSA (I-MRSA) of 10 EIP study sites in 2005, with an incidence of 53 per 100,000. The national in-hospital case-fatality was 17.8%. U.S. in-hospital mortality rate from I-MRSA was 6.3 per 100,000. We wanted to assess the 30-day and 180-day crude case-fatality (CFR) and mortality rates of I-MRSA and determine factors associated with death. Methods: Vital statistics data was available up to Oct. 31, 2007. We used data from the Active Bacterial Core (ABC) surveillance component of the Emerging Infections Program in Davidson County. Cases from Oct. 2004-Jul. 2007 were included for 30-day CFR/mortality rates. Cases from Oct. 2004-Apr. 2007 were included to determine 180-day CFR/mortality rates. We reviewed Tennessee vital statistic data to determine patient outcomes; we matched by name and birthdate. We

Page 208 of 262

calculated the number of days between the initial MRSA-positive culture and date of death recorded on death certificates for each matched case to determine the numerator for the 30- and 180-day CFR/mortality rates. Results: I-MRSA rates for 2004-2007 were 59.1 per 100,000. The 30-day I-MRSA mortality rate was 7.3; 180-day I-MRSA mortality rate was 9.9 per 100,000. Fifty-four of 192 deaths (28%) were identified from vital statistic records alone (i.e., occurred following discharge). The overall 30- and 180-day CFRs were 13.2% and 19.1%, respectively. Blood stream infections (BSI) accounted for 85% of I-MRSA. Patients with MRSA BSI had higher 30- and 180-day crude CFRs compared to patients with non-BSI I-MRSA (14.7% vs. 4.5% [relative risk {RR}= 3.3, 95% CI: 1.5-7.3] and 21.4% vs. 5.7%, [RR= 3.8, 95% CI: 1.8-7.9], respectively). 30-day CFRs were not statistically significant among Blacks and Whites (12.6% vs. 14.3%, respectively). Healthcare-associated I-MRSA had a higher 30- and 180-day CFR compared to community-associated MRSA (14.4% vs. 9% [RR= 1.7, 95% CI: 1.0-2.9] and 21.0% vs. 12.7%, [RR= 1.7, 95% CI: 1.1- 2.8] respectively). Conclusions: MRSA BSI is associated with much higher CFR than other IMRSA. Policy and practices aimed toward the reduction of I-MRSA rates in Tennessee are necessary to decrease the number of deaths annually associated with I-MRSA.

Board 268. Dissemination of Community-Associated Methicillin-Resistant Staphylococcus aureus CMRSA7 (USA400) in Northern Saskatchewan, Canada

J. Irvine1, B. Quinn1, D. Stockdale1, S. Woods2, M. Nsugngu2, P. Levett3, R. McDonald3, G. Golding4, G. Horsman3, M. Mulvey4, the Northern Antibiotic Resistance Partnership; 1Population Health Unit, LaRonge, SK, CANADA, 2Northern Inter-tribal Health Authority, Prince Albert, SK, CANADA, 3Saskatchewan Disease Control Laboratory, Regina, SK, CANADA, 4National Microbiology Laboratory, Winnipeg, MB, CANADA.

Background: Although the USA300 (CMRSA10) strain of community-associated methicillin-resistance (CAMRSA) is rapidly disseminating across North America, some reports have described the emergence of CA-MRSA in northern Canadian communities. This study examines the incidence and molecular epidemiology of CA-MRSA in Page 210 of 262 three of the most northerly Saskatchewan health regions. Methods: Surveillance was conducted over six years beginning in 2001 in three of the most northerly Saskatchewan health regions for all communities (on and offreserve). Specimens from clinical indications were collected from remote community health centers and small rural hospitals (<35 beds) and MRSA positive cases were reported to the respective health authorities. Cases with asymptomatic carriage were excluded. In order to calculate total CA-MRSA rates of recurrence, cases occurring more than 2 months of the preceding episode and / or at a different site, were considered a recurrent episode. Pulsed-field gel electrophoresis (PFGE) of SmaI digested genomic DNA and RT-PCR for the mecA, nuc, and PVL-encoding genes was used to characterize a subset of the isolates. Results: A total of 1,927 MRSA events in 1,409 individuals were reported over the study period with 99% being community-associated. Fifty-six percent (N=783) of the individuals were < 20 years of age, while the majority of their cases (80.8%) were skin and soft tissue infections. The annual rate of CA-MRSA distinct individuals reported in these health regions increased from 9 per 10,000 population in 2001 (range to 4-10 per 10,000) to 169 per 10,000 in 2006 (range 43-233 per 10,000). An annual periodicity was observed with the highest number of cases being reported during the third quarter (July-September). Of the CAMRSA cases, 15.1% of the individuals had at least one recurrent episode after 2 months. A subset of strains (N=192) were typed and 97.4% (N=187) were found to be Canadian PFGE epidemic type CMRSA7 (USA400) with 3 strains being CMRSA2 (USA100/800) and 2 strains being CMRSA10 (USA300). Conclusions: This report describes the rapid emergence of CA-MRSA in Northern Saskatchewan. The molecular epidemiology appears to be different from urban centers in southern Canada with the majority of cases being caused by CMRSA7 (USA400). Antimicrobial Resistance

Board 294. Daptomycin Resistance and hVISA Development in MRSA Endocarditis

M. Pastagia1, N. Casau-Schulhof1, S. G. Jenkins2, J. Jao2; 1Mount Sinai Hospital, New York, New York, NY, 2Mount Sinai Medical Center, New York, NY.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a common etiology of endocarditis in hemodialysis patients. We present a patient without any prior hospitalizations or vancomycin usage within the past ten years who developed MRSA endocarditis with persistent bacteremia while on daptomycin therapy. She then became resistant to daptomycin while on therapy, and ultimately cleared her bacteremia only after valve replacement. We performed microbiological tests on her blood and valve isolates. Methods: We performed E-strip testing of the four blood isolates with MRSA bacteremia as well as the tissue heart valve after replacement with vancomycin, daptomycin, linezolid, and tigecycline E-strips to establish the MIC. These specimens were also tested for

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heterogeneously vancomycin intermediate Staphylococcus aureus (hVISA) via teicoplanin E-strips of 0.5 and 2 McFarland standards. Results: The initial positive blood culture with MRSA was shown to have a MIC to vancomycin of 6 and 3 for daptomycin. These numbers remained similar for the subsequent two positive blood cultures a few days later while she remained on daptomycin, renally dosed. The fourth positive blood culture nearly one week later while on daptomycin was found to have a vancomycin MIC of 6 and a daptomycin MIC of 4. The heart valve was subsequently replaced, and the MICs of the tissue valve to vancomycin was 3, and to daptomycin was 6. All of these isolates were then tested for hVISA via teicoplanin E-strip testing at 0.5 and 2 McFarland standards. This testing revealed MICs of 3 and 4 at 0.5 and 2 McFarland, respectively for the initial blood culture. The subsequent two blood cultures showed MICs of 6 and 8 respectively. By the fourth blood culture, the MICs were 12 and 8 respectively. Ultimately the tissue valve’s MICs to teicoplanin were tested, and found to be 12 and 16, respectively. Conclusions: It is quite uncommon for patients who have not been on prior vancomycin therapy extensively to develop resistance to daptomycin so quickly. Here, we present such a case and were able to demonstrate that this isolate became a heterogeneously vancomyin intermediate Staphylococcus aureus after nearly one week of daptomycin therapy. This transformation from a non-hVISA to an hVISA strain may be predictive of antibiotic failure in this case.

Board 295. Laboratory Analysis of Staphylococcus aureus in Florida: January 1, 2003 to December 31, 2005 with an Emphasis on Methicillin Resistance

S. K. Kolar1, R. Sanderson2, A. Sanchez-Anguiano1; 1University of South Florida, Tampa, FL, 2Florida Department of Health, Tampa, FL. Background: Methicillin resistance among S. aureus has been a concern in the healthcare setting. Recently, MRSA has emerged in the community setting. Methods: This cross-sectional study examines methicillin resistance among S. aureus laboratory isolates in an outpatient population in the state of Florida. The database included all S. aureus laboratory results from a large commercial laboratory from January 1, 2003 to December 31, 2005 provided to the Florida Department of Health. Results: There was a total of 61,596 isolates in the database with the number of isolates doubling each year. The percent of isolates that were methicillin resistant significantly increased each year from 35.1% in 2003 to 49.7% in 2005. Isolates from skin and soft tissue comprised 79.6% of the reported site of infections, of which 52.7% were methicillin resistant in 2005. Methicillin resistance varied by year, age group, gender, county, and region. There was little difference in methicillin resistance between males and females (49.0% and 50.2% in 2005). There was some variation between the age groups, the 21- 30 age group had the highest percentage of MRSA (51% in 2005) and the <1 age group the lowest (40.2% in 2005). Variation by region and county was noted with the western panhandle having the highest percentage of MRSA (62.5% in 2005) and the southwest region the lowest (41.7% in 2005). The percentage of MRSA isolates that were resistant to trimethoprim-sulfamethoxazole, gentamycin, and rifampin was less than three percent. Discussion: The percent of isolates that were methiclillin resistant significantly increased during the study period. The differences by age group and region of the state were larger and may be important to consider when evaluating a potential S. aureus infection. Resistance to non beta-lactam antibiotics remains low and these could be alternative for empiric antimicrobial therapy in the outpatient setting.

New or Rapid

Diagnostics Board 38.

Novel Method and Medium for Detecting and Identifying both Methicillin Susceptible (MSSA) and Methicillin resistant(MRSA) Staphylococcus aureus

S. C. Edberg; Yale-New Haven Hospital, New Haven, CT.

Background: Currently, to detect MSSA or MRSA two pathways are available. The first uses semi-selective culture media; incubation 18-24h, then a series of tests for identification; subculture to a mec A inducing medium for an additional 18 to 24h. Accordingly, considerable skilled labor and time are required. The second pathway utilizes specific genetic amplification of the mecA gene for MRSA, and another amplification for MSSA. Each is quite costly in materials and equipment, thus precluding its use from all but the largest hospitals. A novel specific method and medium for detection of (MSSA) and (MRSA) [AureusAlert®, Pilots Point LLC] (AA) is presented. It requires no skilled labor, determines the presence of S. aureus (SA) within 4h, and differentiates MSSA and MRSA in an additional 12- 16h, and costs 25% of PCR. Methods: The testing procedure first utilizes an enhanced plasma substrate. The specimen (e.g., nasal swab) is inoculated into this plasma substrate and incubated at 35C. If SA is present, in from 2 to 6 hours on average, a clot forms because of the detection of coagulase. Hence, the observation of the clot is Page 99 of 262 specific for the presence of SA.. The clot is then dissolved, freeing the SA. An aliquot from the liquefied clot is added to a culture medium that promotes the growth of SA and also has cefoxitin to ascertain methicillin resistance. After incubation (8-18 h), growth, as evidenced by a color change, is specific for MRSA; no color change indicates the presence of MSSA. A total of 60 MSSA and 60 MRSA from patient nasal cultures were constructed to determine minimum SA sensitivity. In addition, 50 ICU patient samples were tested and compared to the mannitol salt agar (MSA) procedure. Results: From the 60 MSSA constructed, all were positive in 5 h; 49 in 4 h; 38 in 3 h; and 26 in 2. From the 60 MRSA constructed, all were positive in 6 h; 54 in 5h; 49 in 4h; 36 in 3h, and 24 in 2h. Detection limit in all were 102-3. From the 50 patients, there were no false positives. MSA and AA both detected MSSA in 9; AA alone in 2. For MRSA, both MSA and MRSA detected 13, MSA alone detected 1, and AA alone detected 2. Conclusions: AureusAlert® offers the prospect for all sized institutions at risk for SA a low cost, rapid means to detect both MSSA and MRSA utilizing unskilled labor. Widespread clinical evaluation is warranted.

Transmission of Methicillin-Resistant Staphylococcus intermedius between Animals and Humans

E. van Duijkeren1, D. Houwers1, A. Schoormans1, M. Broekhuizen-Stins1, R. Ikawaty2, A. Fluit2, J. Wagenaar1; 1Faculty of Veterinary Medicine, Utrecht University, Utrecht, THE NETHERLANDS, Page 19 of 262 2Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, THE NETHERLANDS.

Background: Staphylococcus intermedius is a commensal and a pathogen in dogs and cats, but is rarely isolated from humans. However, S. intermedius in humans has been associated with dog bite wounds, bacteraemia, pneumonia and ear infections. In the Netherlands, the prevalence of canine and feline infections with methicillin-resistant S. intermedius (MRSI) is increasing and therefore also the risk of their zoonotic transmission. Methods: At Utrecht University MRSI were cultured from infected surgical wounds of five dogs and one cat which had undergone surgery at the same veterinary clinic (clinic A). Samples were taken from the nose of the surgeon, from six technicians and from the nose and coat of two healthy dogs living at the clinic in order to identify the source. In addition, 22 environmental samples were taken from several sites at the clinic. S. intermedius was identified in these samples using standard techniques. Antimicrobial susceptibilities were determined by an agar diffusion method. The mecA gene was detected by PCR. The isolates were genotyped by PFGE using SmaI as restriction enzyme. Four epidemiologically unrelated MRSI isolates from patients at other veterinary clinics were also included. Results: MRSI was cultured from the nose of the surgeon, three technicians, one healthy dog and four environmental samples. The isolates were resistant against ampicillin, amoxicillin with clavulanic acid, cephalexin, ceftiofur, ceftazidime, enrofloxacin, gentamicin, kanamycin, chloramphenicol, lincomycin, clindamycin, tetracycline and trimethoprim/sulphamethoxazole and susceptible to fusidic acid and rifampicin. This was the same resistance pattern as the initial isolates from the six patients. All isolates were mecA positive by PCR. The PFGE profiles from the MRSI isolates from clinic A were all indistinguishable and differed from the profiles of the isolates from other clinics. Conclusions: Together, these data suggest transmission of MRSI between animals and humans. To our knowledge, this is the first report on the transmission of MRSI between humans and animals. People working at veterinary clinics should be aware of this risk for their own and their patients’ sake.

Methicillin-resistant Staphylococcus aureus (MRSA) Infections among Pets in Minnesota

J. B. Bender1, K. Coughlan1, K. Waters1, D. Boxrud2, K. Peterson3, J. Buck4; 1University of Minnesota, Veterinary Public Health, St. Paul, MN, 2Minnesota Department of Health, Public Health Laboratory, St. Paul, MN, 3University of Minnesota, Veterinary Medical Center, St. Paul, MN, 4Minnesota Department of Health, St. Paul, MN.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) infections are increasingly being reported in dogs, horses, pigs, and cats. The zoonotic potential from these infections is unknown and requires further assessment. To document the occurrence among select animal populations, samples were collected from animals residing in a long-term care facility, pets of patients recently diagnosed with MRSA infection, and clinically ill animals presenting to a veterinary hospital. Methods: Nasal and rectal swabs were collected from asymptomatic animals in a long-term care facility and pets of patients recently diagnosed with MRSA. Culture-confirmed MRSA recovered from ill animals were identified through surveillance in a veterinary hospital. Collected isolates were sent to the Minnesota Department of Health for confirmation, antimicrobial susceptibility testing, and molecular subtyping. Results: Two of 11 resident Page 39 of 262 cats from the long-term care facility were identified with MRSA. All isolates were genotype USA100. MRSA was isolated from 2 of 28 asymptomatic pets of pet owners diagnosed with community-associated MRSA. Isolates from the 2 animals were genotype USA300. Since October 2003, MRSA has been identified in 18 refractory cases presented to the veterinary medical clinic. Isolates were obtained from 12 dogs, 5 cats, and 1 horse. Thirteen of 16 available isolates were genotype USA100 and the remaining 3 were genotype USA300. Nine of 12 interviewed family members of the infected pet were recently hospitalized or had on-going severe illnesses (i.e. chemotherapy), or were healthcare providers. Spread within the veterinary clinic was suspected from several case clusters supported by isolation of indistinguishable strains among case isolates. Conclusions: Pets with MRSA likely acquire their infection from their owners as demonstrated by the presence of common genotypes among the various populations. There is a need to re-enforce precautionary measures and hand hygiene to pet owners diagnosed with MRSA infection. Owner education should describe the potential risk of transmission from and/or to pets. Further research to quantify this household risk, the length of carriage in pets, and the potential treatment options is needed.


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