Distribution and abundance of Ixodes scapularis (Acari: Ixodidae) in North America: ecological processes and spatial analysis

Conditions influencing the distribution and abundance of Ixodes scapularis Say in North America have been the object of considerable study during the past 2 decades, resulting in new information about its expanding range, population structure, host associations, and environmental constraints. Variation in the methods, timing, or extent of sampling, the type of population estimate developed, and the spatial scale of analysis makes comparisons of results difficult. This report summarizes research on I. scapularis habitat, including the diversity of hosts and physical conditions in the environment where they are abundant, and how this may influence dispersal and range expansion. Recent efforts to analytically address spatial distributions are considered. Approaches that may be useful in clarifying and resolving unanswered questions are suggested, and a conceptual framework for analyzing this vector's expanding abundance and distribution is offered.

Streptomyces pneumonia in a patient with human immunodeficiency virus infection: case report and review of the literature on invasive streptomyces infections

Streptomyces species are most widely known for their production of antimicrobial substances and, apart from mycetoma, have rarely been reported as a cause of infection. We describe a patient with early human immunodeficiency virus infection who presented with fever, cough, and nodular pulmonary infiltrates. Open lung biopsy revealed necrotic tissue and a sulfur granule; aerobic bacterial cultures yielded Streptomyces species. The patient was treated successfully with clarithromycin for 6 months. We review the clinical presentation and treatment of invasive streptomyces infections.

Development and duration of antibody response against Ehrlichia equi in horses

OBJECTIVE

To characterize antibody response in horses with clinical signs of Ehrlichia equi infection.

DESIGN

Prospective study.

ANIMALS

13 horses with confirmed acute E equi infection.

PROCEDURE

Sequential serum sampling was performed in Connecticut and New York during 1995 and 1996 to identify horses with naturally acquired equine granulocytic ehrlichiosis (EGE). Horses with clinical signs of EGE (i.e., fever without respiratory involvement) were confirmed as having E equi infection by polymerase chain reaction detection of ehrlichial DNA and by a minimum fourfold increase in total antibody titer by indirect fluorescent antibody staining methods. Infection was corroborated by use of DNA sequencing.

RESULTS

11 of 13 horses did not have detectable antibody in serum samples obtained at onset of disease. Seroconversion was evident in samples obtained 19 to 81 days thereafter. Median time to peak antibody response was 46 days after onset and median titer was 1:320. For 11 of 13 horses, antibody titers were < or = 1:40 by 215 days after onset.

CLINICAL IMPLICATIONS

E equi was found in horses in the northeastern United States and caused EGE. Concentration of antibodies to E equi increased within 19 to 81 days of disease onset and were low during early weeks of infection. Therefore, antibody detection may be of limited value for early serologic diagnosis. We suggest that disease may develop from a reinfection, and retrospective serologic studies to determine exposure to E equi may reflect a disproportionate number of negative reactions.

Multicenter comparison of BACTEC 9050 and BACTEC 9240 blood culture systems

The overall recovery of organisms and time to detection with the BACTEC 9050 and BACTEC 9240 systems were compared in a multicenter evaluation. In the first phase of the study, a total of 4,383 compliant aerobic (Plus Aerobic/F) blood culture sets were processed. There was no significant difference in the recovery of individual groups of organisms with the two systems, with the exception of Streptococcus pneumoniae which was isolated more frequently with BACTEC 9050. False-positive signals occurred more often with BACTEC 9240 (58 cultures) than with BACTEC 9050 (43 cultures), but false-negative cultures were uncommon with both systems (3 cultures for each system). Time to detection of positive cultures of clinically significant organisms was essentially the same with both instruments. In the second phase of the study, 2,431 compliant anaerobic (Plus Anaerobic/F) blood culture sets were processed. There was no significant difference in the recovery of organisms with BACTEC 9050 compared with BACTEC 9240. Significantly (P < 0.03) more false-positive signals occurred with BACTEC 9240 (15 cultures) than with BACTEC 9050 (4 cultures). Likewise, more false-negative cultures occurred with BACTEC 9240 (11 cultures) than with BACTEC 9050 (8 cultures). Time to detection of positive cultures of clinically significant organisms was essentially the same with both systems with the exception of anaerobes (N = 10), which were recovered earlier (P < 0.01) with BACTEC 9240 (35.0 h) than with BACTEC 9050 (61.4 h).

Evaluation of a disk diffusion method for determining susceptibility of Mycobacterium avium complex to clarithromycin

We evaluated an agar disk diffusion method for determining the susceptibility of Mycobacterium avium complex to clarithromycin. Isolates were inoculated onto the surface of a Middlebrook 7H11 plate, followed by the application of a 15-microgram clarithromycin disk. Zone sizes were read after 5-7 days of incubation. Zone sizes had a bimodal distribution; 40 isolates (10%) had no zone of inhibition, whereas the zone sizes for the remaining isolates ranged from 11 to 60 mm. Most isolates (37/40) having no zone of inhibition came from patients who had been treated previously with clarithromycin. Fifty-one isolates were also tested for clarithromycin susceptibility using a microdilution broth method. Defining susceptibility as a zone size of > 10 mm, disk diffusion test results agreed with the results by the microdilution broth method for 50 of 51 (98%) isolates tested by both methods. Agar disk diffusion is a promising method for the determination of clarithromycin susceptibility testing for M. avium complex.

Emergence of raccoon rabies in Connecticut, 1991-1994: spatial and temporal characteristics of animal infection and human contact

The North American raccoon rabies epizootic continues to expand, now affecting most of New England. In 1990, raccoons became the vertebrate most often reported rabid in the United States. Emergence of this zoonosis poses increasing, but poorly defined risks to humans. This study analyzed various demographic, environmental, and behavioral factors associated with animal infection and human exposure before and during the epizootic in Connecticut. Rabies virus infections among terrestrial vertebrates were analyzed from 1985 through 1994. From March 1991, when the first case was diagnosed, through December 1994, 2,522 of 13,147 animals tested were found positive for rabies viral antigen. Forty-seven percent of the raccoons tested were infected, representing 88.0% of all animals found positive. Domestic animals constituted only 1.7% of positive test results, but 40.6% of the tests performed. The epizootic wave of transmission advanced approximately 30 km/year. Most rabies-positive wild animals were taken from private properties, usually near houses. Possible human exposures involved 939 people on 556 occasions through direct contact (20.7%) or indirectly through another animal (79.3%). Of 3,239 domestic animals exposed to rabies-positive wild animals, 18.4% lacked vaccination. Rabies has become enzootic in Connecticut and risk to humans and animals persists. The public health burden is considerable, yet knowledge is lacking to develop sustainable prevention strategies.

The early humoral response in human granulocytic ehrlichiosis

The early antibody response in patients with human granulocytic ehrlichiosis (HGE) and in mice infected with the HGE agent was characterized by using sera to probe lysates of HL-60 cells infected with HGE organisms. Sera were obtained from 18 patients with HGE, mostly within the first 6 weeks of clinical infection, and from mice infected with the HGE agent for up to 3 weeks. A 44-kDa antigen was reactive with IgG in all 18 patients, and IgG to 40-, 65-, and 80-kDa antigens was present in 6, 8, and 7 patients, respectively. In addition, IgM to 40-, 44-, 65-, and 80-kDa antigens was found in 9, 5, 4, and 4 subjects. Immunoglobulins to antigens ranging between 95 and 125 kDa were detected less frequently. HGE agent-infected C3H/HeJ mice had an antibody response similar to that in humans. Thus, the 40- and 44-kDa proteins of the HGE agent elicit early strong antibody responses during infection. Characterization of the antigens recognized by antibodies during HGE should aid in diagnosis and understanding of the disease.

Update on detection of bacteremia and fungemia

The presence of microorganisms in a patient's blood is a critical determinant of the severity of the patient's illness. Equally important, the laboratory isolation and identification of a microorganism present in blood determine the etiologic agent of infection, especially when the site of infection is localized and difficult to access. This review addresses the pathophysiology and clinical characteristics of bacteremia, fungemia, and sepsis; diagnostic strategies and critical factors in the detection of positive blood cultures; characteristics of manual and instrument approaches to bacteremia detection; approaches for isolating specific microorganisms associated with positive blood cultures; and rapid methods for the identification of microorganisms in blood cultures.

Telomerase expression in normal endometrium, endometrial hyperplasia, and endometrial adenocarcinoma

Telomerase activity has been detected in a broad range of human cancers and its expression could be an important step in tumor progression. Here, telomerase activity by the telomeric repeat amplification protocol in cases of benign endometrium, endometrial hyperplasia, and endometrial adenocarcinoma was tested. Telomerase expression was detected in 13 of 14 cases of proliferative phase endometrium, in 7 of 12 cases of secretory phase endometrium, but was not detected in any of 7 cases of atrophic endometrium. Three of three cases with evidence of luteal phase defect and one of four cases of chronic endometritis also expressed telomerase activity. Hyperplastic endometrium was positive for telomerase in 13 of 17 cases. Telomerase activity was detected in 40 of 48 cases of endometrial adenocarcinoma, which included 36 of 43 cases of endometrioid adenocarcinoma and four of five cases of papillary serous carcinoma. The detection of telomerase in endometrial adenocarcinoma was not associated with either architectural grade, myometrial invasion, or stage. There was statistically significant association, however, between telomerase activity in benign atrophic endometrium versus any endometrial abnormality in women 52 years of age or older.

Malignant transformation of mammalian cells initiated by constitutive expression of the polo-like kinase

Polo-like kinase (Plk) is the mammalian homologue of the Drosophila polo and Saccharomyces cerevisiae CDC5 genes, which are thought to be involved in regulating chromosomal segregation. Previously, we showed that transient ectopic expression of Plk could induce DNA synthesis in quiescent NIH 3T3 cells, suggesting that Plk might also have a function during G1 or S phase. Here we report that microinjection of Plk mRNA is sufficient to drive quiescent cells into mitosis and that constitutive expression of Plk in NIH 3T3 cells causes oncogenic focus formation. These transformed cells grow in soft agar and form tumors in nude mice. Because Plk expression has been shown to be high in various human tumors, we suggest that Plk may contribute to the promotion and/or progression of human cancers.

Comparison of BACTEC 12B vs solid media for the recovery of Mycobacterium avium complex from blood cultures in AIDS patients

We compared liquid (BACTEC 12B) and solid culture media for the diagnosis of Mycobacterium avian complex (MAC) bacteremia among 258 AIDS patients with a positive blood culture. Neither culture media alone had adequate sensitivity; BACTEC 12B detected growth earlier. Use of both liquid and solid media may improve the yield of mycobacterial blood culture.

Propagation of granulocytic Ehrlichia spp. from human and equine sources in HL-60 cells induced to differentiate into functional granulocytes

Ehrlichia spp. from human and equine sources in the northeastern Unites States were detected by PCR, isolated, and propagated in the HL-60 promyelocytic leukemia cell line. Growth of Ehrlichia from both equine and human sources was enhanced by addition of retinoic acid, which causes granulocytic differentiation of the HL-60 cells. DNA sequencing of a portion of the 16S rDNA gene supported the hypothesis that the same pathogen was responsible for both equine and human granulocytic ehrlichiosis.

The diagnostic yield of acid-fast-bacillus smear-positive sputum specimens

The yield of mycobacterial culture from acid-fast-bacillus smear-positive sputum specimens was 387 or 439 (88.2%). Forty-nine of 52 culture-negative specimens came from patients on treatment. We conclude that the yield of culture from smear-positive sputum specimens is very high and that only two acid-fast-bacillus smear-positive specimens are needed for the initial evaluation of pulmonary mycobacteriosis.

Microhabitat-independent regional differences in survival of unfed Ixodes scapularis nymphs (Acari:Ixodidae) in Connecticut

The effects of habitat and microclimate on survival of unfed nymphal black-legged ticks, Ixodes scapularis Say (approximately I. damnini Spielman, Clifford, Piesman & Corwin), were studied under natural conditions in southcentral and northwestern Connecticut. At both coastal and inland locations, survival of 3 groups of 20 wild-caught questing nymphs placed in nylon mesh bags was monitored in each of 3 different habitats (field, forest canopy, and forest/field edge) during summer 1995. Simultaneously, soil temperature, ground-level air temperature, and relative humidity were measured continuously within each habitat at both sites. The number of ticks surviving in each habitat was monitored weekly. Average daily survival rates of nymphs were related inversely to soil temperature but were not related to air temperature or humidity. Overall, nymphal ticks at the inland site survived significantly longer than those at the coastal site; however, no significant differences in mortality rates were found among habitats. These results suggest that inland environmental conditions are suitable for lengthy survival of unfed nymphal I. scapularis in regions where this tick is not yet abundant.

A new tick-borne encephalitis-like virus infecting New England deer ticks, Ixodes dammini

To determine if eastern North American Ixodes dammini, like related ticks in Eurasia, maintain tick-borne encephalitis group viruses, we analyzed ticks collected from sites where the agent of Lyme disease is zoonotic. Two viral isolates were obtained by inoculating mice with homogenates from tick salivary glands. The virus, which was described by reverse transcriptase polymerase chain reaction and direct sequencing of the amplification products, was similar to, but distinct from, Powassan virus and is provisionally named "deer tick virus." Enzootic tick-borne encephalitis group viruses accompany the agents of Lyme disease, babesiosis, and granulocytic ehrlichiosis in a Holarctic assemblage of emergent deer tick pathogens.

The incidence of false-positive cultures for Mycobacterium tuberculosis

The frequency of false-positive cultures for Mycobacterium tuberculosis due to cross-contamination has been difficult to determine because of the lack of specific strain markers. Isolates collected prospectively over 5 yr from a municipal health department laboratory underwent DNA fingerprinting using the IS6110 and pTBN12 sequences. We reviewed the clinical and laboratory records of all isolates that had matching DNA fingerprints and were processed within 42 d of each other; 8 isolates were classified as probable or definite false-positives, representing 4.0% (8/199) of the culture-positive patients. A convenience sample of 42 isolates from three other mycobacterial laboratories also underwent DNA fingerprinting, and five (12%) were found to be definite or probable false-positives. Cross-contamination during initial processing of specimens was the most common source of false-positive cultures. The source of cross-contamination for three false-positive cultures was a laboratory proficiency survey specimen containing strain H37Ra. Ten of the 13 patients were misdiagnosed as having tuberculosis, and seven received unnecessary multidrug treatment. Clinicians should be aware of the potential for false-positive cultures for M. tuberculosis, and mycobacteriology laboratories need to carefully review procedures to minimize this occurrence. DNA fingerprinting provides a valuable tool for the study of false-positive cultures.

Clinical importance of increased sensitivity of BacT/Alert FAN aerobic and anaerobic blood culture bottles

Two recent multicenter blood culture studies found that BacT/Alert FAN (FAN) bottles (Organon Teknika, Durham, N.C.) had increased yields in detecting bacteremia and fungemia compared with standard BacT/Alert (STD) bottles. Because the clinical importance of this increase in microbial recovery is unknown, we performed a retrospective analysis to determine the frequency with which FAN bottles were the sole means of detecting an episode of bacteremia. There were 1,047 positive blood cultures in which both study bottles were adequately filled and the organism isolated was judged to be the cause of sepsis: 240 (23%) were positive only in FAN bottles and 73 (7%) were positive only in STD bottles. Of a total of 664 episodes of bacteremia, 126 (19%) were identified only by FAN bottles and 43 (7%) were identified only by STD bottles (P < 0.0001). Episodes detected only by FAN bottles more often were recurrent events (23 of 126, or 18%) than episodes detected only by STD bottles (2 of 43, or 5%) (P < 0.05) and more commonly occurred in patients receiving theoretically effective antibiotic therapy (33 of 126 [26%] versus 4 of 43 [9%]) (P < 0.05). The medical records for patients with 127 of these episodes (92 FAN bottles only; 35 STD bottles only) were available for review. More than half of both FAN bottle-only (60 of 92, or 65%) and STD bottle-only (20 of 35, or 57%) episodes were judged to be clinically important. We conclude that FAN bottles improve the detection of bacteremia and that the majority of the additional episodes detected are clinically important. The benefits of the greater yield in specific patient populations must be balanced against the higher costs of FAN bottles.

Prolonged incubation of blood and bone marrow cultures in 12B bottles processed on the BACTEC 460 TB system does not increase microbial recovery

Standard references continue to recommend testing specimens processed on the BACTEC TB System for 8 weeks, despite evidence that mycobacteria are rarely recovered beyond 5-6 weeks. To clarify this issue, we retrospectively reviewed all positive blood/bone marrow cultures processed during a 17-month period when specimens were tested for 6 weeks. We then prolonged the incubation period to 8 weeks during the subsequent 5 months. Excluding Mycobacterium genavense, only 1 of 159 mycobacterial isolates was recovered during and none were recovered beyond the 5th week of incubation and testing on the BACTEC TB System.

Microclimate-dependent survival of unfed adult Ixodes scapularis (Acari:Ixodidae) in nature: life cycle and study design implications

Microclimate and other abiotic factors may be important in determining the survival of arthropod vectors, yet the impact of such variables rarely has received careful examination. The impacts of habitat, microclimate, and experimental confinement on survival rates of unfed adult blacklegged ticks, Ixodes scapularis Say, were studied in field enclosures in southcentral and northwestern Connecticut. At both locations, 2 enclosures were placed in each of 3 different habitats (field, forest canopy, and forest/field edge). Forty wild-caught adult ticks (20 males, 20 females) were placed in each enclosure. At one site, another 40 ticks were confined to nylon mesh bags placed inside each enclosure. Soil temperature, ground-level air temperature and relative humidity were measured within each habitat. The number of ticks surviving within each enclosure was monitored 1 or 2 times per week. Ticks that were confined in nylon bags had a lower survival rate than ticks that were able to move freely within the enclosures. Ticks survived longer in edge and forest habitats than in open fields, which were characterized by greater extremes in air temperature, soil temperature, relative humidity, and vapor pressure deficit than the other 2 habitats. The mean daily survival rates of free-ranging I. scapularis were negatively related to air temperature, vapor pressure deficit, and the coefficient of variation of relative humidity.

Interaction of cyclooxygenases with an apoptosis- and autoimmunity-associated protein

Cyclooxygenases (COXs) 1 and 2 are 72-kDa, intralumenal residents of the endoplasmic reticulum (ER) and nuclear envelope, where they catalyze the rate-limiting steps in the conversion of arachidonate to the physiologically dynamic prostanoids. Recent studies, including the generation of knockout mice, show COX-1 and COX-2 to have biologically distinct roles within cells and organisms. Also apparent is that arachidonate substrate is selectably metabolized by COX-2 after mitogen stimulation in many cells that contain both isoforms. Because COX-1 and COX-2 are highly conserved in all residues needed for catalysis and in their purified forms have almost identical kinetic properties, we have searched for COX-interacting ER proteins that might mediate these unique isoenzymic properties. Using COXs as bait in the yeast two-hybrid system, we identified autoimmunity- and apoptosis-associated nucleobindin (Nuc) as a protein that specifically interacts with both isoenzymes. COX-Nuc binding was substantiated by immunoprecipitation experiments, which showed that COX-1 and, to a lesser extent, COX-2 form complexes with Nuc in vitro. When overexpressed in COS-1 cells, Nuc was found to be extracellularly released. However, when Nuc was co-overexpressed with COX-1 or COX-2, its release was reduced by >80%. This finding suggests that COX isoenzymes participate in the retention of Nuc within the lumen of the ER, where COX may regulate the release of Nuc from the cell. It also identifies Nuc as a potential regulator of COXs through this interaction.

General principles of specimen collection and transport

In this issue of Clinical Infectious Diseases, we present the first article in a series entitled "Diagnostic Microbiology Updates." Although clinical microbiology is included in the curricula of virtually all infectious disease fellowships, the degree of emphasis on this subject varies considerably. Infectious disease physicians--even those who have direct responsibilities or consulting responsibilities for the microbiology laboratories of the institutions in which they practice--may be hard pressed to keep up with the rapidly changing content of the primary literature in clinical microbiology. The purpose of this series, therefore, is at least in part to fill this void and to provide concise updates for clinicians. The first article, written by Dr. Michael L. Wilson, reviews current concepts in specimen collection and transport. A key issue for all clinicians (which is not always sufficiently emphasized) is the quality of the specimen submitted to the laboratory. It is an axiom that if specimens of poor quality are submitted, the results generated by the laboratory will have little or no clinical utility. Dr. Wilson's article describes some of the methods available to assure that only specimens of good quality, i.e., those most likely to be useful clinically, are processed in the microbiology laboratory. Future articles will address specific types of specimens, groups of pathogens, and diagnostic techniques, including molecular methods. We hope this series will be informative and valuable to the readers of Clinical Infectious Diseases, and we look forward to your comments.