Specific amplification of Rickettsia japonica DNA from clinical specimens by PCR.

The gene encoding the 17,000-molecular-weight genus-common antigen (17K genus-common antigen) has been cloned and sequenced from Rickettsia japonica. The primer pair used for PCR was designed from this sequence. A 357-bp fragment was observed by amplifying the genomic DNA from R. japonica and also the DNA from blood clots of patients with spotted fever group rickettsiosis. The results indicated that this method is suitable for the diagnosis of spotted fever group rickettsiosis in Japan.     

Causative agent of spotted fever group rickettsiosis in Japan.

Since 1984, it has been known that spotted fever group rickettsiosis exists in Japan. We isolated three strains of the causative rickettsiae, designated Katayama, Misaka, and Abe, from patients with the disease and studied the characteristics of the isolates. Nude mice and cyclophosphamide-treated mice died after infection with the isolates. However, infected normal mice recovered and acquired immunity. Infected adult male guinea pigs had fever, a scrotal reaction, and seroconversion. The isolates propagated well in tissue-cultured Vero cells. Analysis by the cross-immunofluorescence antibody method showed that these isolates were closely related serologically. To reveal their immunological properties in detail, we produced 21 anti-Katayama monoclonal antibodies. Seven of these antibodies reacted with all representative strains of spotted fever group rickettsiae used in this study, and five others reacted only with the homologous strain, revealing that the Katayama strain has a strain-specific antigen(s) different from those of other spotted fever group rickettsiae. Moreover, these strain-specific antibodies also reacted with the Misaka and Abe strains. These results demonstrate that the causative agent of spotted fever group rickettsiosis in Japan is a new serotype of spotted fever group rickettsiae.     

First serologic evidence of human spotted fever group rickettsiosis in Korea

To investigate the prevalence of spotted fever group rickettsioses in Korea, a serosurvey of Japanese spotted fever rickettsiosis in patients with acute febrile illness was conducted with an indirect immunofluorescence assay. Overall, 19.88% of the patients were found to have polyvalent antibody against Rickettsia japonica. This study is the first documentation of spotted fever group rickettsiosis in Korea.     

Mediterranean spotted fever in north Dalmatia: is there a problem?

We analyzed clinical and therapeutic characteristics of Mediterranean spotted fever (MSF) in north Dalmatia. Analysis was conducted in 93 patients hospitalized with MSF at Zadar General Hospital during the 1988-2000 period. The most frequently found signs of the disease were high fever (91; 97.8%), maculopapular rash (89; 95.7%), headaches (84; 90.3%), arthralgia (75; 80.6%), exhaustion (75; 80.6%) and nausea (65; 69.9%). Tache noire, as a pathognomonic sign of MSF, was found in 22 (23.7%) patients. The most frequently indicated diagnoses were febris cum exanthemate (43; 46.2), rickettsiosis suspecta (21; 22.6%) and exanthema maculopapulosum (15; 16.1%). Early therapeutic efficiency was achieved by doxycycline in 34/43 (79.1%), and by ciprofloxacin in 10/14 (71.4%) treated adult patients, and by azithromycin in 7/9 (77.8%) children. The identification of MSF endemic rickettsiosis in north Dalmatia, serious clinical forms of the disease and the success of early and adequate anti-rickettsial antibiotic therapy are a clear warning that our physicians must be very familiar with this disease and include this rickettsial disease in differential diagnosis of acute febrile diseases accompanied by rash.     

Adaptation of Ehrlichia sennetsu to canine blood monocytes: preliminary structural and serological studies with cell culture-derived Ehrlichia sennetsu.

Ehrlichia sennetsu, the causative agent of human sennetsu rickettsiosis, was successfully propagated in primary canine blood monocyte cultures. The growth cycle of this organism appears to be similar to that of Ehrlichia canis. The antigen derived from our E. sennetsu cultures was used to develop an indirect fluorescent antibody test for detection and titration of serum antibodies to the organism. Using this test system, we found that five human serum samples obtained from patients clinically diagnosed as having sennetsu rickettsiosis were positive for anti-E. sennetsu antibodies. In addition, 29% of the serum samples obtained from 200 patients having a fever of unknown origin and residing in various regions of Malaysia were also serologically positive. All sera from apparently healthy individuals were negative in the test. Dogs inoculated with cell culture-adapted E. sennetsu developed a significant specific antibody titer to E. sennetsu, and the organism was subsequently isolated from their blood. These animals showed no clinical evidence of disease. The possibility of a higher prevalence of human sennetsu rickettsiosis in Southeast Asia and the potential usefulness of the canine model for studies of human sennetsu rickettsiosis are discussed.     

Kinetics of antibody responses in Rickettsia africae and Rickettsia conorii infections

African tick-bite fever, caused by Rickettsia africae, is the most common tick-borne rickettsiosis in sub-Saharan Africa. Mediterranean spotted fever due to Rickettsia conorii also occurs in the region but is more prevalent in Mediterranean countries. Using microimmunofluorescence, we compared the development of immunoglobulin G (IgG) and IgM titers in 48 patients with African tick-bite fever and 48 patients with Mediterranean spotted fever. Doxycycline treatment within 7 days from the onset of disease significantly prevented the development of antibodies to R. africae. In patients with African tick-bite fever, the median times to seroconversion with IgG and IgM were 28 and 25 days, respectively, after the onset of symptoms. These were significantly longer by a median of 6 days for IgG and 9 days for IgM than the times for seroconversion in patients with Mediterranean spotted fever (P < 10(-2)). We recommend that sera collected 4 weeks after the onset of signs of patients with suspected African tick-bite fever should be used for the definitive serological diagnosis of R. africae infections.     

Serological diagnosis of Mediterranean boutonneuse fever

Mediterranean spotted fever is a rickettsiosis due to R. conori. The authors have tested 2 serological reactions available in this disease: Weil-Felix (WF) and indirect immunofluorescent antibody test IF. IF, tested on 184 sera is sensitive (100% of positivity 30 days after the onset of the disease) and specific if a four fold in two sera is obtained at a level upper than: 80. The WF tested on 112 sera is not specific and its sensitivity is poor.     

Isolation of a spotted fever group rickettsia from a patient and related ecologic investigations in Xinjiang Uygur Autonomous Region of China.

Investigation of patients, healthy persons, and ticks in Jinghe County, Xinjiang Uygur Autonomous Region, People's Republic of China, for evidence of spotted fever group (SFG) rickettsiosis demonstrated strong evidence for a high prevalence of pathogenic SFG rickettsiae. Antibodies to SFG rickettsiae were detected in 62.5% of healthy subjects tested by enzyme-linked immunosorbent assay and 20% tested by complement fixation test. Two febrile patients were documented as having acute spotted fever rickettsiosis by complement fixation seroconversion. One, and 11-year-old Kazakh boy with eschar and regional lymphadenopathy, had an SFG rickettsia (An strain) isolated from his blood. A hemolymph test revealed that 20% of ticks contained rickettsiae. Two strains of SFG rickettsiae were isolated from male and female Dermacentor nuttalli ticks. The human SFG rickettsial isolate is the first to be obtained in the People's Republic of China.     

Genetic Identification of Rickettsial Isolates from Fatal Cases of Brazilian Spotted Fever and Comparison with Rickettsia rickettsii Isolates from the American Continents

Fifteen bacterial isolates from spotted fever group rickettsiosis in Brazil were genetically identified as Rickettsia rickettsii. In a phylogenetic analysis with other R. rickettsii isolates from GenBank, the Central/South American isolates showed low polymorphism and formed a clade distinct from two North American clades, with the North American clades having greater in-branch polymorphism.     

Kinetics of Antibody Responses in Rickettsia africae and Rickettsia conorii Infections

African tick-bite fever, caused by Rickettsia africae, is the most common tick-borne rickettsiosis in sub-Saharan Africa. Mediterranean spotted fever due to Rickettsia conorii also occurs in the region but is more prevalent in Mediterranean countries. Using microimmunofluorescence, we compared the development of immunoglobulin G (IgG) and IgM titers in 48 patients with African tick-bite fever and 48 patients with Mediterranean spotted fever. Doxycycline treatment within 7 days from the onset of disease significantly prevented the development of antibodies to R. africae. In patients with African tick-bite fever, the median times to seroconversion with IgG and IgM were 28 and 25 days, respectively, after the onset of symptoms. These were significantly longer by a median of 6 days for IgG and 9 days for IgM than the times for seroconversion in patients with Mediterranean spotted fever (P < 10⁻²). We recommend that sera collected 4 weeks after the onset of signs of patients with suspected African tick-bite fever should be used for the definitive serological diagnosis of R. africae infections.     

Histopathology and immunopathology of skin biopsy specimens in Mediterranean spotted fever.

Histology of skin lesions and demonstration in them of Rickettsia conorii by direct immunofluorescence test (DIF) are presented in 13 patients with Mediterranean spotted fever (MSF). The lymphohistiocytic vasculitis which dominated the picture is not specific, however, it could be suggestive for the diagnosis of rickettsiosis. By DIF we demonstrated rickettsial coccobacillary forms in all the patients: in 12 macular lesions and in one "tache noire". The diagnosis was also confirmed by indirect immunofluorescence test in each case. DIF test was shown to be sensitive, specific and reliable in early diagnosis of MSF.     

Evaluation of PCR-based assay for diagnosis of spotted fever group rickettsiosis in human serum samples

A nested PCR assay was developed for the detection of spotted fever group (SFG) rickettsiae in serum samples. The assay was based on specific primers derived from the rickettsial outer membrane protein B gene (rompB) of Rickettsia conorii. An SFG rickettsia-specific signal is obtained from R. akari, R. japonica, R. sibirica, and R. conorii. Other bacterial species tested did not generate any signal, attesting to the specificity of the assay. As few as seven copies of the rompB gene of R. conorii could be detected in 200 microl of serum sample. The assay was evaluated with a panel of sera obtained from patients with acute-phase febrile disease tested by immunofluorescent antibody assay (IFA). The SFG rickettsia-specific DNA fragment was detected in 71 out of 100 sera, which were proven to have immunoglobulin M antibodies against SFG rickettsial antigen by IFA. The results were further confirmed by restriction fragment length polymorphism and sequencing analysis of the DNA fragments. The results indicated that this PCR assay is suitable for the diagnosis of spotted fever group rickettsiosis in Korea.     

The pathogenesis of the vascular lesions in experimental rickettsial disease of the guinea pig (Rocky Mountain Spotted fever group)

Summary Experimental rickettsiosis (Rocky Mountain Spotted fever group) was produced in guinea pigs and the vascular lesions studied by light, electron and immunofluorescent microscopy in an attempt to study the pathological aspects of this infection.The vascular lesion falls roughly into two forms. In the early stage of the disease the non specific endothelial damage observed is probably due to a toxin activity, since no gamma globulin, complement or fibrinogen was detected in the lesion. At the later stage immunological factors superimpose on the initial action of Rickettsia at the vessel walls, leading to extensive deposits of gamma globulin and complement. The extensive damage in larger vessels is morphologically similar to an immediate-type hypersensitivity arteritis. This is probably due to lysosomal enzymes liberated from attracted neutrophils and the toxic activity of both Rickettsia antibody-complement complexes and the microorganisms themselves. Endothelial damage leads to platelet and extensive fibrin deposits.     

Sodium currents in subthalamic nucleus neurons from Nav1.6-null mice

In some central neurons, including cerebellar Purkinje neurons and subthalamic nucleus (STN) neurons, TTX-sensitive sodium channels show unusual gating behavior whereby some channels open transiently during recovery from inactivation. This "resurgent" sodium current is effectively activated immediately after action potential-like waveforms. Earlier work using Purkinje neurons suggested that the great majority of resurgent current originates from Na(v)1.6 sodium channels. Here we used a mouse mutant lacking Na(v)1.6 to explore the contribution of these channels to resurgent, transient, and persistent components of TTX-sensitive sodium current in STN neurons. The resurgent current of STN neurons from Na(v)1.6(-/-) mice was reduced by 63% relative to wild-type littermates, a less dramatic reduction than that observed in Purkinje neurons recorded under identical conditions. The transient and persistent currents of Na(v)1.6(-/-) STN neurons were reduced by approximately 40 and 55%, respectively. The resurgent current present in Na(v)1.6(-/-) null STN neurons was similar in voltage dependence to that in wild-type STN and Purkinje neurons, differing only in having somewhat slower decay kinetics. These results show that sodium channels other than Na(v)1.6 can make resurgent sodium current much like that from Na(v)1.6 channels.     

Rickettsiosis: state of the art at the turn of the 21st century

Information about changes in the modern taxonomy of intracellular bacteria conditionally united within the nomination of "Rickettsioses" is presented in the paper. Due to a total hobby related with keeping home animals (pets), cats and dogs, apart from the cattle, joined the natural ecological cycles of rickettsioses stimulation. The morbidity of rickettsioses of the acaroid group has been persistently growing; like in case with other pathologies (Lyme's disease) involving the acaroid transfer factor, its obvious "urbanization" is pronounced. Absolute and relative morbidity indices in respect to rickettsioses, which are epidemiologically important for Russia, are presented. The modern knowledge database concerning the rickettsioses makes it possible to control the epidemic process for this infection category. It is noteworthy, that Prowazek's rickettsiosis of its both forms (i.e. the epidemic and relapsing ones), which does not have an independent cycle of circulation of its stimulator in wild nature, and unlike the acaroid group rickettsioses, turned into a socially controllable infection. It will be totally eliminated, during 10-15 years, both in Russia and the CIS countries. The practitioners are well supplied with a variety of drugs of tetracycline and fluorine-quinol groups, which makes it possible to arrest the infection process in patients rapidly and effectively and to prevent the lethal cases. A low incidence rate of rickettsioses, including Q fever, within the general infection morbidity, and taking into consideration the availability of methods for effective therapy and prevention, makes one consider a comprehensive vaccination against the discussed group of infections to be irrational. Obviously, such vaccination must be still applied in respect to a limited number of persons from among high-risk groups and for two or three varieties of rickettsioses only (i.e. Prowazek's rickettsioses, Rocky Mountain spotted fever and Q fever). Live vaccines, obtained on the basis of attenuated and recombined strains (which have a full-scale set of specific antigens), are recommended.     

Proteinic and genomic identification of spotted fever group rickettsiae isolated in the former USSR.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), restriction fragment length polymorphism of polymerase chain reaction-amplified genes (RFLP-PCR), and pulsed-field gel electrophoresis (PFGE) were used to identify 25 isolates of spotted fever group rickettsia collected in the former USSR. Six Rickettsia akari isolates which were identical to the MK reference strain from the American Type Culture Collection were found. Also, 14 isolates were found to be Rickettsia sibirica and identical to reference strain 246. Two of three isolates previously considered as atypical, low-pathogenic strains of R. sibirica, were found to be strains of Rickettsia slovaca. The third, strain S, was similar in its RFLP-PCR profile to "R. africae" sp. nov. (proposed name for a rickettsia pathogenic for human beings in southern Africa) but in its SDS-PAGE and PFGE profiles was unique among spotted fever group rickettsiae. Strain M-1 was confirmed as a genetic variant of Rickettsia conorii. The Astrachan isolate, the causative agent of a tick-bite rickettsiosis at the North of the Caspian Sea, showed a previously described RFLP-PCR profile identical to that of the Israeli tick typhus rickettsia, but its SDS-PAGE and PFGE profiles different from those of the other strains tested.     

Presence of Rickettsia conorii subsp. israelensis, the causative agent of Israeli spotted fever, in Sicily, Italy, ascertained in a retrospective study

A retrospective analysis by molecular-sequence-based techniques was performed to correctly identify the etiological agent of 24 Mediterranean spotted fever cases occurring in Western Sicily, Italy, from 1987 to 2001. Restriction analysis of a 632-bp PCR-amplified portion of the ompA gene allowed presumptive identification of five clinical isolates as belonging to Rickettsia conorii subsp. israelensis, the etiological agent of Israeli spotted fever (ISF). The remaining 19 rickettsial isolates were Rickettsia conorii subsp. conorii, the only pathogenic rickettsia of the spotted fever group reported in Italy until the present. Sequence analysis of the ompA gene confirmed the identification of all the R. conorii subsp. israelensis isolates and demonstrated that rickettsiosis caused by R. conorii subsp. israelensis can be traced back to 1991 in Sicily. The recorded clinical data of the five ISF patients support the idea that these strains could correlate to more-severe forms of human disease. Three of five patients experienced severe disease, and one of them died.     

Sequential changes in hematologic and biochemical parameters in African tick bite fever

Objective  To evaluate the sequential changes and to estimate the frequencies of abnormalities in some commonly measured biological variables in patients with African tick bite fever (ATBF), an emerging spotted fever group (SFG) rickettsiosis in international travelers to rural sub-Saharan Africa.
Methods  A study was done of hemoglobin, total leukocyte count, absolute lymphocyte count, blood platelet count and serum levels of C-reactive protein (S-CRP), alanine aminotransferase (S-ALAT), aspartate aminotransferase, lactic dehydrogenase, γ-glutamyl transferase, alkaline phosphatase, bilirubin, sodium and creatinine during the first two weeks of illness and prior to the institution of antirickettsial therapy in 108 patients with travel-associated ATBF.
Results  There were significant falls in mean total leukocyte count, mean absolute lymphocyte count, and mean platelet count, and significant increases in mean S-CRP and S-ALAT. During the first ten days of illness, elevated S-CRP, lymphopenia and elevated S-ALAT were detected in 91.7%, 73.3% and 40.7% of patients, respectively. Most abnormalities were mild. For 55 patients who underwent both S-CRP and absolute lymphocyte count determination, at least one parameter was abnormal in 52 (94.5%) patients.
Conclusions  The sequential changes in many biological parameters during the acute phase of ATBF mimic those reported in other SFG rickettsioses. Mild abnormalities are frequent, with increased S-CRP and lymphopenia being the two most consistent findings.     

Murine Typhus: Clinical and epidemiological aspects

Rickettsia typhi:

is an intracellular bacteria who causes murine typhus. His importance is reflected in the high frequency founding specific antibodies against Rickettsia typhi in several worldwide seroepidemiological studies, the seroprevalence ranging between 3-36%. Natural reservoirs of R. typhi are rats (some species belonging the Rattus Genus) and fleas (Xenopsylla cheopis) are his vector. This infection is associated with overcrowding, pollution and poor hygiene. Typically presents fever, headache, rash on trunk and extremities, in some cases may occur organ-specific complications, affecting liver, kidney, lung or brain. Initially the disease is very similar to other diseases, is very common to confuse the murine typhus with Dengue fever, therefore, ignorance of the disease is a factor related to complications or non-specific treatments for the resolution of this infection. This paper presents the most relevant information to consider about the rickettsiosis caused by Rickettsia typhi.      

Rocky Mountain spotted fever: a disease in need of microbiological concern.

Rocky Mountain spotted fever, a life-threatening tick-transmitted infection, is the most prevalent rickettsiosis in the United States. This zoonosis is firmly entrenched in the tick host, which maintains the rickettsiae in nature by transovarian transmission. Although the incidence of disease fluctuates in various regions and nationwide, the problems of a deceptively difficult clinical diagnosis and little microbiologic diagnostic effort persist. Many empiric antibiotic regimens lack antirickettsial activity. There is neither an effective vaccine nor a generally available assay that is diagnostic during the early stages of illness, when treatment is most effective. Microbiology laboratories that offer only the archaic retrospective Weil-Felix serologic tests should review the needs of their patients. Research microbiologists who tackle these challenging organisms have an array of questions to address regarding rickettsial surface composition, structure-function analysis, and pathogenic and immune mechanisms, as well as laboratory diagnosis.