Stability of plasmid sequences in an acute Q-fever strain of Coxiella burnetii. (49/167)

The rickettsial pathogen Coxiella burnetii undergoes a variation in which virulent isolates (phase 1) become avirulent (phase 2) after repeated passage in a non-immunologically competent host. Biochemically, this variation is associated with a lipopolysaccharide modification and possibly other factors. Genetically, the regions of DNA responsible for phase variation have not been identified. We have sought to determine whether the plasmid identified in acute disease isolates, QpH1, which represents approximately 5% of the coding capacity of this organism is involved in phase variation. Plasmids from phase 1 and phase 2 variants (designated QpH1 and QpH2, respectively) were compared by restriction endonuclease digestion and Southern blot hybridization to determine whether sequence changes in the phase 2 plasmid might account for changes in the virulence of phase 2 organisms compared with that of phase 1 cells. Using over 20 different restriction enzymes, no changes in DNA restriction fragment patterns were detected regardless of whether the phase change occurred during egg or tissue culture passage. The plasmid-specific mRNAs produced from metabolically active, purified cells were identical for each phase type. Using QpH1 or QpH2 DNA as a template, the mRNA produced by an E. coli extract was also identical. Finally, the proteins encoded by either plasmid in an in vitro transcription/translation reaction were identical. These data indicate that within the limits of our analysis, the plasmid DNA from C. burnetii phase variants is structurally and functionally the same and is therefore unlikely to be involved in phase variation.  (+info)

Probe directed at a segment of Rickettsia rickettsii rRNA amplified with polymerase chain reaction. (50/167)

In an effort to explore a sensitive taxon-specific detection system for bacteria, we sequenced the 16S rRNA from two strains of Rickettsia rickettsii, five other rickettsiae, and Coxiella burnetti to find a probe site unique to R. rickettsii. We then synthesized a 16-mer that hybridized only to the rRNA of R. rickettsii. Using a primer complementary to a sequence found only in rickettsial rRNA, we then generated a cDNA. We amplified the probe site in a 180-base segment of the cDNA by using the cDNA primer and a second primer also unique to rickettsiae in a polymerase chain reaction. The segments of rRNA from each of the rickettsiae were amplified 10(6)- to 10(7)-fold, and the R. rickettsii probe hybridized only to the amplified segment from R. rickettsii. The rRNAs from Staphylococcus aureus, C. burnetii, and Neisseria meningitidis were not amplified and did not hybridize with the probe. The approach detailed below may prove clinically useful in the direct detection of pathogens that are difficult to cultivate.  (+info)

Inactivation of Coxiella burnetii by gamma irradiation. (51/167)

The gamma radiation inactivation kinetics for Coxiella burnetii at -79 degrees C were exponential. The radiation dose needed to reduce the number of infective C. burnetii by 90% varied from 0.64 to 1.2 kGy depending on the phase of the micro-organism, purity of the culture and composition of suspending menstruum. The viability of preparations containing 10(11) C. burnetii ml-1 was completely abolished by 10 kGy without diminishing antigenicity or ability to elicit a protective immune response in vaccinated mice. Immunocytochemical examinations using monoclonal antibodies and electron microscopy demonstrated that radiation doses of 20 kGy did not alter cell-wall morphology or cell-surface antigenic epitopes.  (+info)

The ability of mononuclear cells to coagulate blood in response to Coxiella burnetii. (52/167)

Endocarditis is a rather frequent complication of Q fever caused by Coxiella burnetii. We examined the ability of phase I (virulent) or phase II (avirulent) C. burnetii to coagulate blood in the presence of human blood mononuclear cells in vitro. After incubation for 4 h, virulent phase I C. burnetii was an effective stimulant for mononuclear cells. Since this interaction is a potent trigger of blood coagulation through the extrinsic pathway, it could be responsible for the local deposition of fibrin on the surface of infected valves and the development of large vegetations in cases of endocarditis complicating Q fever.  (+info)

Susceptibility of Coxiella burnetii to pefloxacin and ofloxacin in ovo and in persistently infected L929 cells. (53/167)

The relative lack of efficacy of the antibiotic treatment of chronic Q fever endocarditis justifies the further evaluation of the susceptibility of Coxiella burnetii to the modern quinolone antibiotics. We evaluated the efficacies of pefloxacin and ofloxacin in controlling the Nine Mile isolate of C. burnetii by using an embryonated egg assay and persistently infected L929 cells in culture. Pefloxacin was effective in controlling the intracellular parasite at a concentration of 50 micrograms per egg and 1 microgram/ml in cultures of infected cells. Ofloxacin was effective at a concentration of 25 micrograms per egg and 0.5 microgram/ml in infected-cell cultures. In light of the fact that the concentrations of antibiotics used fall within physiological ranges used in humans, ofloxacin and pefloxacin may be useful in the clinical management of chronic Q fever, for which, to date, results have been poor.  (+info)

Antibiotic susceptibilities of two Coxiella burnetii isolates implicated in distinct clinical syndromes. (54/167)

Antibiotic susceptibility testing of two isolates of the Q-fever agent, Coxiella burnetii, was performed with recently and persistently infected L929 fibroblast cells. The two genetically distinct isolates, Nine Mile and Priscilla, are implicated in two different clinical disease syndromes, acute and chronic Q fever, respectively. We compared the efficacies of rifampin, doxycycline, and five 4-quinolone compounds (ciprofloxacin, difloxacin, ofloxacin, norfloxacin, and pefloxacin) in reducing persistent C. burnetii infection of L929 fibroblasts. In persistently infected cells, the Priscilla isolate was less susceptible to all antibiotics tested when compared with the Nine Mile isolate. The most effective antibiotics against the Priscilla isolate were ofloxacin, pefloxacin, and ciprofloxacin (50% inhibitory concentrations of 0.5, 2.2, and 2.5 micrograms/ml, respectively). In persistently infected cells, the Nine Mile isolate was highly susceptible to all antibiotics tested except doxycycline. In contrast, the Priscilla and Nine Mile isolates in recently infected cells were somewhat susceptible to doxycycline; the Priscilla isolate was significantly more susceptible to ofloxacin and rifampin in recently infected host cells than in persistently infected cells. Persistently infected L929 cells were also treated with antibiotic combinations. Although ciprofloxacin and doxycycline had no synergistic effect on the Priscilla isolate, ciprofloxacin and rifampin acted synergistically. Collectively, these in vitro results are in accord with the fact that chronic Q fever in humans is generally not successfully managed with antibiotics. They also indicate that early diagnosis may be essential and that combination antibiotic therapy that includes quinolones may be effective in treating chronic Q fever.  (+info)

Endotoxicosis induced by Coxiella burnetii lipopolysaccharide stimulates a ribosomal protein S6 kinase: some properties of the partially purified enzyme. (55/167)

Guinea pig endotoxicosis induced by lipopolysaccharide from Coxiella burnetii Nine Mile phase I stimulates phosphorylation of liver ribosomal protein S6, with a 50% increase at 12 h postinoculation. The responsible protein kinase (S6PK) has been partially purified from liver; its activity is independent of cyclic AMP and of Ca2+ plus phosphatidyl serine or diacylglycerol. The preparation has an apparent optimum concentration of 20 mM Mg2+, while Ca2+ and Mn2+ are each inhibitory at 2 mM. The apparent Km for ATP is 30 microM with intact ribosomes. Because of the central role of phosphorylation in metabolic regulation and a purported role of phosphorylated S6 in protein synthesis, the lipopolysaccharide-induced stimulation of S6PK suggests a significant regulatory role of such enzymes in the pathobiochemistry of Q fever infection and endotoxicosis.  (+info)

Truckin' pneumonia--an outbreak of Q fever in a truck repair plant probably due to aerosols from clothing contaminated by contact with newborn kittens. (56/167)

We describe an outbreak of Q fever affecting 16 of 32 employees at a truck repair plant. None of the cases were exposed to cattle, sheep or goats, the traditional reservoirs of Q fever. The cases did not work, live on, or visit farms or attend livestock auctions. One of the employees had a cat which gave birth to kittens 2 weeks prior to the first case of Q fever in the plant. The cat owner fed the kittens every day before coming to work as the cat would not let the kittens suckle. Serum from the cat had high antibody titres to phase I and phase II Coxiella burnetii antigens. The attack rate among the employees where the cat owner worked, 13 of 19 (68%), was higher than that of employees elsewhere, 3 of 13 (28%) [P less than 0.01]. The cat owner's wife and son also developed Q fever. None of the family members of the other employees with Q fever was so affected. We conclude that this outbreak of Q fever probably resulted from exposure to the contaminated clothing of the cat owner.  (+info)