Population-based incidence of human granulocytic ehrlichiosis in northwestern Wisconsin, 1997-1999.

The incidence of human granulocytic ehrlichiosis (HGE) in the upper Midwest is uncertain. Active surveillance for suspected HGE was conducted from 1997 through 1999 in a 13-county region of northwestern Wisconsin. Suspected HGE cases were classified, according to the national case definition, as confirmed, probable, or not HGE. In total, 112 confirmed cases and 30 probable cases of HGE were identified. The median age of the 142 case patients was 56 years, and 92 (65%) were male; 111 (78%) were residents of the surveillance region. The mean annual incidence of confirmed and probable HGE was 9.3 cases per 100,000 residents; there was no increase from 1997 to 1999. The incidence was highest among persons > or =50 years old and residents of Washburn County. The incidence of HGE in this region exceeded prior estimates, but it was lower than the reported incidence in areas of endemicity in Connecticut.

Tickborne infections as a cause of nonspecific febrile illness in Wisconsin.

Lyme disease, human granulocytic ehrlichiosis (HGE), and babesiosis are tickborne infections that are indigenous to Wisconsin. To assess their importance as a cause of nonspecific fever, we recruited patients with febrile illness at 10 clinics in northwestern Wisconsin from May through August of both 1997 and 1998. Eligible patients had a temperature >38.0 degrees C but no rash or other localizing source. Acute and convalescent serological tests were performed for Borrelia burgdorferi, Babesia microti, and Ehrlichia equi; polymerase chain reaction was performed to detect granulocytic Ehrlichia rDNA. Seventeen (27%) of 62 eligible patients had laboratory evidence of tickborne infection, including 7 (11%) with probable Lyme disease only, 8 (13%) with HGE only, and 2 (3%) with apparent coinfection. No patients with Babesia infection were identified. Patients with and without tickborne infection were similar with regard to age, sex, symptoms, history of tick bite, and outdoor exposure. The results suggest that tickborne infections are an important cause of nonspecific febrile illness during the tick season in northwestern Wisconsin.

Ixodes scapularis (Acari: Ixodidae): abundance and rate of infection with Borrelia burgdorferi in four state parks in Wisconsin.

Four state parks located in Lyme disease endemic regions of Wisconsin were surveyed for the presence of Ixodes scapularis Say during May and June of 1998 by drag sampling along hiking trails. Nymphal abundance varied between parks, with the average number of nymphs encountered in 1 h ranging from 6.2 +/- 3.8-47.1 +/- 36.3 (mean +/- SD). Questing nymphs were tested for the presence of Borrelia burgdorferi by culture in BSK medium and 7-12% was found to be infected. The average risk of encountering an infected nymph (entomologic risk index) ranged from 0.5 to 5.2 infected nymphs per hour. The highest entomological risk index was recorded from a small island park in northwestern Wisconsin during the last week in May (8.0 infected nymphs per hour). These results indicate a lower risk for human Lyme disease exposure in Wisconsin state parks in comparison with highly endemic areas of the northeastern United States.

Antibiotic susceptibility of invasive Streptococcus pneumoniae in Wisconsin, 1999.

BACKGROUND: Streptococcus pneumoniae is a major cause of community acquired infections in the United States, and rates of antibiotic resistance have increased dramatically in the past decade. Statewide rates of pneumococcal resistance to penicillin and other antibiotics have not been previously reported in Wisconsin. To determine these rates, we assessed invasive pneumococcal isolates for reduced susceptibility to nine different antibiotics. METHODS: Pneumococcal isolates from blood, cerebrospinal fluid or other normally sterile body sites were submitted by 91% of laboratories that perform invasive bacterial cultures. Isolates were tested for susceptibility to penicillin, cefotaxime, ceftriaxone, levofloxacin, meropenem, erythromycin, vancomycin, sulfamethoxazole-trimethoprim and chloramphenicol. RESULTS: There were 409 invasive pneumococcal isolates identified in 1999 among Wisconsin residents, including 385 (94%) isolates from blood. The mean patient age was 42.5 years (range, < 1 year to 96 years), and 213 (52%) were male. Of the pneumococcal isolates, 24% were not susceptible to penicillin, including 10% with high level resistance. Isolates with reduced penicillin susceptibility were also likely to have reduced susceptibility to other antibiotics. Patients with penicillin nonsusceptible (intermediate and fully resistant) pneumococcal isolates were significantly younger (mean, 37.0 years) than those with susceptible isolates (mean, 44.3 years) (p = .04). The proportion of patients with a penicillin nonsusceptible isolate varied by region, ranging from 12.8% in northeastern Wisconsin to 35.5% in northern Wisconsin. CONCLUSIONS: The proportion of invasive pneumococcal isolates with penicillin resistance in Wisconsin is similar to other regions of the United States. Inappropriate antibiotic use contributes to the emergence of resistant pneumococcal infections, and educational efforts are underway to promote judicious antibiotic use in Wisconsin.

Comparison of four immunoserologic assays for detection of antibodies to Borrelia burgdorferi in patients with culture-positive erythema migrans.

In view of the significant sequelae associated with Lyme borreliosis, there is a need for timely and accurate diagnosis of erythema migrans (EM). Although Borrelia burgdorferi can be cultured from biopsies of EM lesions, immunodiagnostic testing is more widely available. Four immunoserologic methods were studied by using the sera of 51 patients with EM lesions that were culture positive for B. burgdorferi. Nineteen patients had single primary lesions, and thirty-two had multiple secondary lesions. At the time of biopsy, 40 patients, 8 with primary lesions and all patients with secondary lesions, were seropositive by an immunoglobulin M (IgM) indirect fluorescent-antibody (IgM IFA) test (Bion Enterprises). Twenty-three patients were seropositive by a whole-cell fluorescence enzyme immunoassay (EIA) (BioWhittaker, Inc.), twenty-two were positive by immunoblotting (ViroStat, Inc.), and one was positive by a P39 recombinant EIA (P39 EIA) (General Biometrics, Inc.). Sera from various patient control groups were tested: rheumatoid arthritis (n = 19), infectious mononucleosis (n = 20), systemic lupus (n = 22), syphilis (n = 13), streptococcal sequelae (n = 20), and healthy subjects (n = 16). None of these sera reacted with the IgM IFA test or P39 EIA. Fifteen reacted with the fluorescence EIA. We conclude that the IgM IFA test is an effective and reliable assay for the diagnosis of EM, particularly for patients with secondary lesions. Immunoblot, fluorescence EIA, and P39 EIA lack the sensitivity to reliably diagnose EM.

Evaluation of a commercial DNA purification system for plasmid analysis of nosocomial bacterial pathogens.

This study evaluated the Promega Magic Minipreps (MM) (Promega Corporation, Madison, WI) DNA purification system for use in plasmid analysis of common nosocomial bacterial pathogens. The MM system is a kit that includes lysis solutions and buffers and incorporates a minicolumn of DNA binding resin for recovery of plasmid DNA. The MM system was used according to the manufacturer's directions to recover plasmids for agarose gel electrophoresis from clinical isolates of Acinetobacter calcoaceticus, Enterobacter cloacae, and Klebsiella pneumoniae. For Salmonella enteritidis and Staphylococcus aureus, lysozyme and lysostaphin, respectively, were used for pretreatment. Plasmid DNA from ten isolates could be recovered in approximately one hour with very little manipulation and no phenol/chloroform extractions and was suitable for restriction endonuclease digestion. Compared with a standard miniprep protocol, the MM system was much easier to perform and resulted in significant cost savings due to a 50% reduction in technologist time. The authors conclude that the MM system is a convenient and cost-effective method for clinical microbiology laboratories for recovering plasmid DNA from nosocomial bacterial pathogens.

Isolation of Borrelia burgdorferi from skin biopsy specimens of patients with erythema migrans.

Procedures for the cultural isolation and identification of Borrelia burgdorferi from skin biopsy specimens are described. B. burgdorferi was isolated from 24 of 34 skin biopsy specimens from patients with erythema migrans. Eight of the culture-positive patients had single, primary lesions and 16 had multiple, secondary lesions. The 17 male and 7 female patients were 2 to 70 years old. Biopsy samples were obtained from erythematous or normal-appearing skin within 1 cm of the peripheral aspect of the lesion. Twenty-three of the isolates were detected within 8 days of incubation in Barbour-Stoenner-Kelly medium with no antimicrobial agents. The identities of the isolates were determined by reactivity with monoclonal antibodies H9724 and H5332. Cultivation of B. burgdorferi from skin lesions suggestive of erythema migrans is a practical and clinically relevant procedure. Clinical isolates and corresponding patient sera and urine will contribute to efforts to improve existing immunoserologic testing methods and develop new assays to diagnose Lyme borreliosis.