Poxviruses and the passive quest for novel hosts.

Poxviruses are famous, or infamous, as agents of disease introduced into novel host species and between populations of the same species. This discussion concerns selected examples of poxviruses associated with vertebrate infections, i.e., the Chordopoxvirus subfamily of the family Poxviridae. Brief note is made of examples of members of the genera Leporipoxvirus and Parapoxvirus-like agents that have been recognized to have significant trans-host species impact. The remaining bulk of the discussion involves examples of members of the genus Orthopoxvirus, which are known to be (have been) involved with human disease, and their zoonotic origins.

Extensive lesions of monkeypox in a prairie dog (Cynomys sp).

Monkeypox with extensive lesions was diagnosed in a prairie dog that was involved in a recent human outbreak of monkeypox in the Midwestern United States. Gross lesions included oral ulcers, pulmonary consolidation, enlarged cervical and thoracic lymph nodes, and multifocal, small, white umbilicated plaques in the gastrointestinal wall. Microscopic lesions were extensive in the lungs and consisted of fibrinonecrotic bronchopneumonia with vasculitis and poorly defined eosinophilic intracytoplasmic inclusion bodies in cells thought to be alveolar epithelial cells, histiocytes, and fibroblasts. Multifocal necrotizing lesions, often accompanied by myxedema, were also present in most of the other examined organs. Aggregates of pox viral particles were observed within lesions by transmission electron microscopy. Monkeypox virus infection was confirmed by real-time polymerase chain reaction and virus culture at the Centers for Disease Control and Prevention. This report highlights the difficulties of rapid diagnosis of exotic or emerging diseases and further substantiates the prairie dog as an animal model of monkeypox.

In vitro susceptibilities of Bartonella and Rickettsia spp. to fluoroquinolone antibiotics as determined by immunofluorescent antibody analysis of infected Vero cell monolayers.

The in vitro susceptibilities of Bartonella and Rickettsia spp. to different concentrations of ciprofloxacin, levofloxacin, ofloxacin and sparfloxacin in Vero cell cultures, were determined by enumeration of immunofluorescent-stained bacilli. After incubation in a CO(2)-enriched atmosphere, inocula were replaced and tested with media containing 12 different concentrations of each antibiotic in replicate for each species and the monolayers were re-incubated. Growth status was determined by evaluation of immunofluorescent staining bacilli. Effective inhibitory antibiotic dilution endpoints were determined by counting Bartonella- and Rickettsia-specific fluorescent foci across a range of antibiotic dilutions with an epi-fluorescent microscope, and were compared with an antibiotic-negative control. Based upon the use of C(max):MIC and AUC:MIC data, levofloxacin exhibited activity against Bartonella elizabethae and B. quintana.

Serodiagnosis of Bartonella bacilliformis infection by indirect fluorescence antibody assay: test development and application to a population in an area of bartonellosis endemicity.

Bartonella bacilliformis causes bartonellosis, a potentially life-threatening emerging infectious disease seen in the Andes Mountains of South America. There are no generally accepted serologic tests to confirm the disease. We developed an indirect fluorescence antibody (IFA) test for the detection of antibodies to B. bacilliformis and then tested its performance as an aid in the diagnosis of acute bartonellosis. The IFA is 82% sensitive in detecting B. bacilliformis antibodies in acute-phase blood samples of laboratory-confirmed bartonellosis patients. When used to examine convalescent-phase sera, the IFA is positive in 93% of bartonellosis cases. The positive predictive value of the test is 89% in an area of Peru where B. bacilliformis is endemic and where the point prevalence of infection is 45%.

Bartonella henselae, B. quintana, and B. bacilliformis: historical pathogens of emerging significance.

Bartonella species were virtually unrecognized as modern pathogens of humans until the last decade. However, identification of Bartonella species as the agents of cat-scratch disease, bacillary angiomatosis, urban trench fever, and possible novel presentations of Carrion's disease has left little doubt of the emerging medical importance of this genus of organisms. The three primary human pathogenic bartonellae, Bartonella bacilliformis (Carrion's disease), B. henselae (cat-scratch disease), and B. quintana (trench fever), present noteworthy comparisons in the epidemiology, natural history, pathology, and host-microbe interaction that this review will briefly explore.

Differentiation of pathogenic Bartonella species by infrequent restriction site PCR.

Infrequent restriction site PCR (IRS-PCR) is a recently described DNA fingerprinting technique based on selective amplification of restriction endonuclease-cleaved fragments. Bartonella isolates associated with human disease and related nonhuman isolates were analyzed by IRS-PCR genomic fingerprinting. Preparation of DNA templates began with double digestion using three different restriction endonuclease combinations. Combinations included the frequently cutting endonuclease HhaI in conjunction with an infrequently cutting endonuclease, EagI, SmaI, or XbaI. Digestion was followed by ligation of oligonucleotide adapters designed with ends complementary to the restriction endonuclease sites. Amplification of fragments flanked with an EagI, SmaI, or XbaI site in combination with an HhaI site produced a series of different-sized amplicons resolvable into patterns by polyacrylamide gel electrophoresis (PAGE). The pattern complexity was varied by the addition of selective nucleotides to the 3' ends of the EagI-, SmaI-, or XbaI-specific primers. Amplicons were also generated with fluorescently labeled primers and were subsequently resolved and detected by capillary electrophoresis. Analysis by traditional slab PAGE and capillary electrophoresis provided suitable resolution of patterns produced with the enzyme combinations EagI-HhaI and SmaI-HhaI. However, the combination of XbaI-HhaI produced too many fragments for sufficient resolution by traditional PAGE, thus requiring the better resolving properties of capillary electrophoresis. Due to the flexibility in modulating the pattern complexity and electrophoresis methods, these techniques allow for a high level of experimental optimization. The results provide evidence of the discriminatory power, ease of use, and flexibility of the IRS-PCR method as it applies to the identification of human-pathogenic Bartonella species.

In vitro susceptibilities of Rickettsia and Bartonella spp. to 14-hydroxy-clarithromycin as determined by immunofluorescent antibody analysis of infected vero cell monolayers.

The in vitro susceptibilities of Rickettsia akari, Rickettsia conorii, Rickettsia prowazekii, Rickettsia rickettsii, Bartonella elizabethae, Bartonella henselae and Bartonella quintana to different concentrations of clarithromycin, 14-hydroxy-clarithromycin (the primary metabolite of clarithromycin) and tetracycline in Vero cell cultures, were determined by enumeration of immunofluorescently-stained bacilli. The extent of antibiotic-induced inhibition of foci was recorded for each dilution of antibiotic and compared with an antibiotic-negative control. Based upon MIC data, clarithromycin alone is highly active against all three Bartonella spp., R. akari and R. prowazekii, while 14-hydroxy-clarithromycin is active against R. conorii, R. prowazekii and R. rickettsii. Further testing is warranted in animal models and human clinical trials, to examine the activity of both clarithromycin and its primary metabolite and to define further the role of clarithromycin in therapy, particularly of infections caused by obligate intracellular bacteria such as Rickettsia and Bartonella spp.

Characterization of Bartonella henselae-specific immunity in BALB/c mice.

BALB/c mice were inoculated with Bartonella henselae by both systemic and mucosal routes. Culture analysis of tissues from mice infected intraperitoneally with a high dose of B. henselae yielded positive results 24 hr after infection. However, culture analysis of blood taken between 6 hr and 7 days after infection from groups receiving live B. henselae were negative. Following intraperitoneal infection, B. henselae was detected by polymerase chain reaction in liver and mesenteric lymph nodes by 6 hr and up to 7 days after infection in liver, kidney and spleen tissue. Enzyme-linked immunosorbent assay (ELISA) of serum samples collected as early as 13 days after infection indicated humoral immune responses to B. henselae. Specific humoral responses remained through week 6. Analysis of faecal samples revealed induction of B. henselae-specific immunoglobulin A by day 28 after infection. In addition, B. henselae-specific cellular responses were indicated by a positive delayed-type hypersensitivity and a T helper 1 (Th1) (CD4+ T cell)-type cytokine response following in vitro stimulation of splenocytes. The significance and implications of these data in relation to B. henselae infections are discussed.

Evaluation of intraspecies genetic variation within the 60 kDa heat-shock protein gene (groEL) of Bartonella species.

A phylogenetic investigation was done on the members of the genus Bartonella, based on the DNA sequence analysis of the groEL gene, which encodes the 60 kDa heat-shock protein GroEL. Nucleotide sequence data were determined for a near full-length fragment (1368 bp) of the groEL gene of the established Bartonella species and used to infer intraspecies phylogenetic relationships. Phylogenetic trees were inferred from multiple sequence alignments by using both distance and parsimony methods, which demonstrated an architecture composed of six well-supported lineages. The results are consistent with relationships deduced from recent sequence analysis studies based upon citrate synthase (gItA) and previously observed genotypic and phenotypic characteristics; however, they showed greater statistical support at the intragenus level. This suggests that groEL may be a more robust tool for phylogenetic analysis of Bartonella lineages.

Rats of the genus Rattus are reservoir hosts for pathogenic Bartonella species: an Old World origin for a New World disease?

Bartonella species were isolated from the blood of 63 of 325 Rattus norvegicus and 11 of 92 Rattus rattus from 13 sites in the United States and Portugal. Infection in both Rattus species ranged from 0% (e.g., 0/87) to approximately 60% (e.g., 35/62). A 337-bp fragment of the citrate synthase (gltA) gene amplified by polymerase chain reaction was sequenced from all 74 isolates. Isolates from R. norvegicus were most similar to Bartonella elizabethae, isolated previously from a patient with endocarditis (93%-100% sequence similarity), followed by Bartonella grahamii and other Bartonella species isolated from Old World rodents (Clethrionomys species, Mus musculus, and Rattus species). These data suggest that Rattus species are a reservoir host for pathogenic Bartonella species and are consistent with a hypothesized Old World origin for Bartonella species recovered from Rattus species introduced into the Americas.

Experimental infection of cotton rats with three naturally occurring Bartonella species.

The kinetics of infection and humoral immune response of laboratory-bred cotton rats (Sigmodon hispidus) challenged with three Bartonella spp. recovered from the blood of naturally infected cotton rats captured in Georgia (USA) are described. Bartonella spp. infection, as determined by bacteremia, occurred in all 18 cotton rats inoculated with live Bartonella of each species at either a low dose, 10(3) colony-forming units (CFU's), or high dose, 10(7) CFU. Cotton rats inoculated with lower doses of Bartonella spp. developed higher bacteremia that persisted for longer periods than in those inoculated with high doses. Peak bacteremia varied among Bartonella spp, ranging from 10(4) to 10(6) CFUs per 1.0 ml of blood. Antibody measured by immunofluorescence assays using species-specific antigens indicated more rapidly rising and higher antibody titers in cotton rats challenged with high doses vs. low doses and with inactivated bacteria vs. live bacteria. Each group of rats produced high IgG titers to the homologous challenge antigen; low or unmeasurable cross-reactivity was detected to heterologous Bartonella antigens. Exposure of cotton rats to a specific Bartonella sp. resulted in protection, as measured by detectable bacteremia, in eight of nine animals challenged with the same Bartonella sp. used initially; no evidence of resistance to secondary challenge with different Bartonella spp. was obtained. Cross-protection between Bartonella spp., isolated from the same rodent species, may not occur.

Prevalence of Bartonella henselae and Bartonella clarridgeiae in an urban Indonesian cat population.

We studied evidence of Bartonella henselae and Bartonella clarridgeiae infection in 54 cats living in Jakarta, Indonesia. By using an indirect immunofluorescence assay, we found immunoglobulin G antibody to B. henselae in 40 of 74 cats (54%). The blood of 14 feral cats was cultured on rabbit blood agar plates for 28 days. Bartonella-like colonies were identified as B. henselae or B. clarridgeiae by using restriction fragment length polymorphism analysis and direct sequencing of the PCR amplicons. Of the cats sampled in the study, 6 of 14 (43%; all feral) were culture positive for B. henselae; 3 of 14 (21%; 2 feral and 1 pet) culture positive for B. clarridgeiae. This is the first report that documents B. henselae and B. clarridgeiae infections in Indonesian cats.

Characterization of human immunoglobulin (Ig) isotype and IgG subclass response to Bartonella henselae infection.

Serologic parameters of cat scratch disease (CSD) were evaluated by Western blot analysis. Sera from patients with serologically confirmed CSD antigen were screened for immunoglobulin (Ig) isotype-specific as well as IgG subclass-specific reactivity against Bartonella henselae whole-cell antigen. Bartonella-negative control sera were used to determine baseline antibody activity. Heterogeneous B. henselae-specific IgG reactivity with numerous protein bands, ranging from >150 to <17 kDa, was observed. Though individual banding patterns were variable, one approximately 83-kDa B. henselae protein (Bh83) was immunoreactive with all CSD sera tested, suggesting it is a conserved antigen during infection. Bh83 was not recognized by reference human antisera against Rickettsia rickettsii, Chlamydia group positive, Treponema pallidum, Orientia tsutsugamushi, Fransciscella tularensis, Ehrlichia chaffeensis, Mycoplasma pneumoniae, and Escherichia coli, although other cross-reactive proteins were evident. Significantly, CSD sera failed to recognize the 83-kDa protein when tested against Bartonella quintana antigen, though sera from B. quintana-infected patients did react to Bh83. This cross-reactivity suggests epitope conservation during infection with B. henselae or B. quintana. Western blot analysis further revealed similar banding patterns when B. henselae was reacted against the Ig isotypes IgG and IgG1 and both secretory and alpha chains of IgA. Neither IgM nor IgE reacted significantly to Bartonella antigen by our Western blot analysis. Dissection of the antibody response at the IgG subclass level indicated that prominent antigen recognition was limited to IgG1. These observations provide insight into induced immunity during CSD and provide evidence for conserved epitope expression during infection with B. henselae or B. quintana.

Prospective randomized double blind placebo-controlled evaluation of azithromycin for treatment of cat-scratch disease.

OBJECTIVE: To determine the efficacy of azithromycin in the treatment of patients with typical cat-scratch disease. DESIGN: Prospective, randomized, double blind, placebo-controlled clinical trial. SETTING: Large military medical center and its referring clinics. PATIENTS: Active duty military members and their dependents with laboratory-confirmed, clinically typical cat-scratch disease. INTERVENTION: Study participants assigned by randomization to treatment with oral azithromycin or placebo for 5 days. OUTCOME MEASURES: Lymph node volume was calculated using three dimensional ultrasonography at entry and at weekly intervals. The ultrasonographer was blinded to the treatment groups. Endpoint evaluations were predetermined as time in days to 80% resolution of the initial total lymph node volume. RESULTS: Demographic and clinical data showed that the azithromycin and placebo treatment groups were comparable at entry although the placebo group tended to be older. Eighty percent decrease of initial lymph node volume was documented in 7 of 14 azithromycin-treated patients compared with 1 of 15 placebo-treated controls during the first 30 days of observation (P = 0.026). After 30 days there was no significant difference in rate or degree of resolution between the two groups. CONCLUSIONS: Treatment of patients with typical cat-scratch disease with oral azithromycin for five days affords significant clinical benefit as measured by total decrease in lymph node volume within the first month of treatment.

Isolation of Bartonella spp. from embryos and neonates of naturally infected rodents.

Embryos and neonatal offspring of wild-captured cotton rats (Sigmodon hispidus) and white-footed mice (Peromyscus leucopus) were tested for the presence of Bartonella spp. Isolates of Bartonella spp. were obtained from 18 of 31 embryos and 7 of 19 neonates from bacteremic dams of the two species; no isolates were obtained from material from non-bacteremic dams. Sequence analysis demonstrated that the isolates from embryos and neonates matched the phylogenetic group of Bartonella spp. isolates obtained from the mother. No antibodies to homologous Bartonella spp. antigens were detected in maternal and neonatal blood or embryonic tissue. These findings suggest the possibility of vertical transmission of Bartonella spp. among natural rodent hosts.

Distribution, diversity, and host specificity of Bartonella in rodents from the Southeastern United States.

A number of Bartonella isolates were obtained from seven species of rodents sampled from 12 geographic sites representing the major biotic communities of the southeastern United States. Bartonella were isolated from the blood of 42.2% of 279 tested rodents. The highest prevalence of infection typically occurred among the most commonly captured species in the rodent community. Four phylogenetic groups, uniting 14 genotypic variants of Bartonella, were identified by sequence analysis of the citrate synthase gene. The level of sequence homology between genotypic groups varied from 88.8% to 96.4%, and the degree of homology among variants within groups was > or = 97%. Cotton rats (Sigmodon hispidus) harbored up to three phylogenetic groups of Bartonella at a single site, and Bartonella of two phylogenetic groups were isolated from a single rodent. All the Bartonella isolated from three species of Peromyscus clustered in a single distinct phylogenetic group, suggesting some host specificity may occur. Mouse ascitic fluids produced in BALB/c mice inoculated with Bartonella of three phylogenetic groups demonstrated high indirect fluorescent antibody (IFA) titers to homologous antigens. However, use of eight Bartonella antigens in an IFA test with sera from 394 wild-caught rodents resulted in either little or extremely low titers of antibody.

Isolation of Bartonella (Rochalimaea) henselae: effects of methods of blood collection and handling.

Bartonella (Rochalimaea) henselae causes cat-scratch disease, bacillary angiomatosis, peliosis hepatis, and fever in humans. B. henselae can be difficult to culture axenically, and as many as 5 weeks may be required before colonies are visible. We compared how different methods of blood collection and handling affect isolation of this pathogen. Blood specimens from B. henselae-infected cats were collected in both EDTA and Isolator blood-lysis tubes and were subsequently plated onto rabbit blood-brain heart infusion agar by using three different schedules: plating immediately, plating after 24 h at 25 degrees C, and plating after 26 days at -65 degrees C. Colonies were counted 14 and 35 days after plating. Blood collected in tubes containing EDTA, frozen at -65 degrees C, and then plated on blood agar yielded a median of 60,000 CFU/ml, compared with 25,333 CFU/ml after collection in the Isolator tubes (P < 0.01). Frozen blood yielded the largest number of B. henselae colonies for any of the schedules tested. These results support previous observations that the Isolator system is more sensitive than tubes containing EDTA for isolation of B. henselae and suggest that, for cat blood, collection in tubes containing EDTA and subsequent freezing may further improve the sensitivity of detection of B. henselae.

In vitro susceptibilities of Bartonella henselae, B. quintana, B. elizabethae, Rickettsia rickettsii, R. conorii, R. akari, and R. prowazekii to macrolide antibiotics as determined by immunofluorescent-antibody analysis of infected Vero cell monolayers.

The in vitro susceptibilities of Bartonella (Rochalimaea) henselae, B. quintana, B. elizabethae, Rickettsia akari, R. conorii, R. prowazekii, and R. rickettsii to different concentrations of azithromycin, clarithromycin, dirithromycin, erythromycin, and roxithromycin in Vero cell cultures were evaluated. Bartonella and Rickettsia spp. were allowed to initiate infection of the antibiotic-free Vero cell monolayers, which were maintained in 16-chamber microscope slides in the absence of antibiotics at 32 degrees C in a CO2-enriched atmosphere. The monolayers were then incubated for 3 h to allow for initial host cell intracellular penetration by infecting species. After inoculation, inocula were replaced and tested with media containing 12 different concentrations of each antibiotic in replicate (10 wells of each antibiotic dilution) for each species, and the monolayers were reincubated. Tetracycline served as the control. Growth status of Bartonella spp. and Rickettsia spp. was determined by evaluation of immunofluorescent staining bacilli. Five days later, when antibiotic-free, control-infected cell monolayers demonstrated significant fluorescence, media were removed for all cell monolayers, the monolayers were fixed, and all specimens were stained with standard indirect immunofluorescent antibody reagents. Fluorescent foci were enumerated by counting such foci on random fields visualized with an epifluorescence microscope. The extent of antibiotic-induced focus inhibition was recorded for each dilution of antibiotic and compared with that of an antibiotic-negative control. Effective antibiotic dilution endpoints for inhibition of Bartonella and Rickettsia proliferation, as judged by absence of increase of significant fluorescence (as compared with no-growth controls), were enumerated by determining the number of cell culture chambers at various antibiotic dilutions that were negative or positive for significant Bartonella- or Rickettsia-specific fluorescence. All of the macrolide agents tested were readily active against all three Bartonella organisms, and azithromycin, clarithromycin, and roxithromycin may have potential in the treatment of Rickettsia infections. Animal model-based clinical trials are warranted to define the specific treatment role of the newer macrolide antibiotics.

Experimentally induced Bartonella henselae infections followed by challenge exposure and antimicrobial therapy in cats.

OBJECTIVES: To elucidate kinetics of Bartonella henselae bacteremia and IgG response, evaluate antibiotic therapy, and investigate challenge exposure in cats. ANIMALS: Specific-pathogen-free cats. PROCEDURE: Cats were inoculated with B henselae or B quintana and monitored. Convalescent cats were challenge exposed with B henselae. Amoxicillin, enrofloxacin, erythromycin, and tetracycline HCl were evaluated for effect on B henselae bacteremia. RESULTS: Cats developed B henselae bacteremia within 1 week; bacteremia persisted for longer than 2 months before subsiding spontaneously. IgG antibody titer developed shortly after onset of bacteremia; antibody co-existed with bacteremia for several weeks and remained detectable after bacteremia subsided. Cats inoculated with B quintana remained abacteremic. On challenge exposure to B henselae, cats previously infected with B henselae remained abacteremic; cats previously inoculated with B quintana supported B henselae infection. Tetracycline HCl and erythromycin depressed B henselae bacteremia; however, duration of bacteremia remained similar to that in untreated cats. Obvious signs of illness were not observed. CONCLUSIONS: Long-duration, high-titer B henselae infections were highly reproducible in cats. Convalescent cats were immune to reinfection. B quintana-inoculated cats did not have evidence of infection and were susceptible to B henselae challenge exposure. Antibiotic therapy was incompletely efficacious in terminating cat bacteremia. CLINICAL RELEVANCE: A cat with an inapparent B henselae infection must provisionally be regarded as a possible reservoir for infection for a minimum of 2 to 3 months. Convalescent cats are resistant to reinfection. Usual antibiotic therapy was not completely efficacious. Measurement of IgG antibody can be used to detect past or current infection.