An investigation of antibiotic susceptibility to empiric therapy for community-associated methicillin-resistant Staphylococcus aureus.

OBJECTIVE: To analyze antibiotic susceptibility patterns of community-associated methicillin-resistant Staphylococcus aureus (MRSA) isolates obtained from skin and soft tissue infections among Wisconsin outpatients. DESIGN: Retrospective genotype testing. SETTING: Isolates were forwarded to the Wisconsin State Laboratory of Hygiene and Marshfield Labs from clinical laboratories throughout Wisconsin. METHODS: MRSA isolates submitted during April, 2010-February, 2012 underwent genotype analysis using pulsed-field gel electrophoresis. Antibiotic susceptibility patterns were determined for all isolates identified by electrophoresis subtyping as strain type USA300, and pattern comparisons were made by public health region. RESULTS: Among 835 MRSA isolates submitted, 217 (26%) were genotyped. Of these, 152 (70%) were USA300 MRSA. Among the 152 USA300 isolates, 95% were susceptible to clindamycin and 99% were susceptible to tetracycline and trimethoprim-sulfamethoxazole. The proportion of clindamycin-susceptible isolates from the southern region was significantly lower when compared to the other 4 regions combined (P = 0.03). One southern region clindamycin-resistant isolate was also resistant to trimethoprim-sulfamethoxazole. CONCLUSIONS: USA300 MRSA was the predominant strain isolated from outpatient skin and soft tissue sites. Antibiotic susceptibility patterns among Wisconsin USA300 MRSA isolates are similar to patterns found in national studies. Local providers should continue to follow national practice guidelines for treatment of outpatient skin infections. A cluster of 4 clindamycin-resistant isolates and 1 trimethoprim-sulfamethoxazole resistant isolate was detected in the southern region, warranting continued surveillance for antibiotic resistance among community-associated MRSA isolates.

Comparison of cefoxitin and oxacillin disk diffusion methods for detection of mecA-mediated resistance in Staphylococcus aureus in a large-scale study.

The recommended breakpoints for the cefoxitin disk diffusion test for Staphylococcus aureus were recently modified. In this large-sample study, cefoxitin sensitivity and specificity compared to those of oxacillin were 97.3% and 100%, respectively. This study validated the new cefoxitin breakpoints for the detection of mecA-mediated resistance in S. aureus.

Evaluation of polymerase chain reaction and culture for diagnosis of pertussis in the control of a county-wide outbreak focused among adolescents and adults.

During a large pertussis outbreak, culture and polymerase chain reaction (PCR) were used to identify 149 case patients; of these case patients, 79 had positive PCR and culture results, 59 had positive PCR results and negative culture results, 11 had negative PCR results and positive culture results (10 PCR-negative, culture-positive specimens were collected < or = 14 days after illness onset). PCR and culture of samples obtained < or = 2 weeks after illness onset and PCR of samples obtained > 2 weeks after illness onset proved to be most diagnostically useful.

Meningococcal disease incidence and mortality in Wisconsin, 1993-2002.

Neisseria meningitidis is a major cause of sepsis and meningitis in children and young adults in the United States. To examine recent epidemiologic features of meningococcal disease in Wisconsin, we evaluated Wisconsin case surveillance data collected during 1993-2002. Surveillance data for cases with onsets during this time were analyzed; statistical trends were assessed. Mortality was examined with regard to age, sex, serogroup, college student status, and young adult status by unadjusted and adjusted analyses. During 1993-2002, 462 cases of meningococcal disease were reported in Wisconsin; 55% of case patients were aged < 19 years. The annual incidence was 0.9 cases per 100,000 persons per year, and incidence was highest among children aged <2 years. Two seasonal peaks in cases were observed during January-April and September-October. The annual mortality rate during the 10-year interval was 0.09 deaths per 100,000 persons per year. Adjusted analysis indicated that serogroup C infection, young adult, and college student status (but not sex) were associated with mortality. Meningococcal disease remains uncommon and sporadic in Wisconsin. Incidence and mortality rates are highest among young children, but young adults who acquire the disease appear to be at an increased mortality risk.

A countywide outbreak of pertussis: initial transmission in a high school weight room with subsequent substantial impact on adolescents and adults.

OBJECTIVE: To describe a large communitywide pertussis outbreak where aggressive diagnostic and treatment measures were used to control the outbreak. DESIGN: Retrospective analysis, May 2003 through February 2004. SETTING: Fond du Lac County, Wisconsin (population 98,882). PARTICIPANTS: Health department personnel conducted case and contact investigations of suspected outbreak-associated illnesses using standard pertussis reporting forms and clinical evaluation and management protocols. Persons with compatible illness were tested for Bordetella pertussis using culture and for B pertussis DNA using polymerase chain reaction. Cases were classified using Council of State and Territorial Epidemiologists definitions. INTERVENTIONS: Health alerts and aggressive testing and treatment of suspected cases of pertussis illness and contact prophylaxis in the community. MAIN OUTCOME MEASURES: Incidences by age, onsets over time, and vaccine coverage in case patients. RESULTS: We identified 261 pertussis cases among county residents; 149 (57%) were laboratory confirmed. Of the first 57 case patients, 47% reported using a particular high school weight room. Pertussis incidence was high in all age groups; 86% of case patients were 10 years or older. Among 156 case patients with reported vaccination histories, 84% had received 5 or more doses of pertussis-containing vaccine. Adults reported significantly more severe pertussis symptoms than adolescents. CONCLUSIONS: Pertussis transmission among adolescents using a school weight room instigated a countywide outbreak with substantial incidence and morbidity among adolescents and adults. Aggressive testing and treatment in the outbreak response likely contributed to a sharp reduction in cases. This labor- and resource-intensive outbreak highlights potential benefits of pertussis booster vaccination among adolescent and adult populations.

Human multidrug-resistant Salmonella Newport infections, Wisconsin, 2003-2005.

We conducted a retrospective study of Salmonella Newport infections among Wisconsin residents during 2003-2005. Multidrug resistance prevalence was substantially greater in Wisconsin than elsewhere in the United States. Persons with multidrug-resistant infections were more likely than persons with susceptible infections to report exposure to cattle, farms, and unpasteurized milk.

Transmission of Salmonella enterica serotype typhimurium DT104 to infants through mother's breast milk.

This study documents the first reported transmission of Salmonella enterica serotype Typhimurium definitive type 104 (DT104) to premature fraternal twins via their mother's breast milk. When premature twin neonates developed severe enteritis in the neonatal intensive care unit (NICU), stool samples and the mother's breast milk were cultured for the presence of Salmonella. Antibacterial susceptibility patterns were determined. Semiquantitative organism abundance data were retrospectively gathered on 54 stored breast milk samples collected on 34 different days using a rapid, real-time polymerase chain reaction (PCR) methodology (LightCycler PCR). Fecal samples from other infants in the NICU at that time were also tested. Pulsed-field gel electrophoresis (PFGE) was used to assess the genetic composition of the isolated organisms. The twins' neonatal stools and mother's breast milk cultures revealed a resistance pattern (R-type) to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. LightCycler PCR analysis of sequential breast milk samples confirmed this to be the likely source of transmission. In the subsequent outbreak investigation, none of the NICU surveillance fecal samples proved positive for this organism. The genetic composition of organisms isolated from the maternal breast milk was indistinguishable from those isolated from neonatal specimens as determined by PFGE. Antibiotic susceptibility tests coupled with PFGE patterns suggested that these Salmonella isolates were DT104. Because the prevalence of DT104 infections is rising in the United States, neonatologists should be aware of breast milk as a potential mode of transmission.