Q fever endocarditis

Chronic Q fever in the United States

Infections due to Coxiella burnetii, the causative agent of Q fever, are uncommon in the United States. Cases of chronic Q fever are extremely rare and most often manifest as culture-negative endocarditis in patients with underlying valvular heart disease. We describe a 31-year-old farmer from West Virginia with a history of congenital heart disease and recurrent fevers for 14 months who was diagnosed with Q fever endocarditis based on an extremely high antibody titer against Coxiella burnetii phase I antigen. Despite treatment with doxycycline, he continued to have markedly elevated Coxiella burnetii phase I antibody titers for 10 years after the initial diagnosis. To our knowledge, this case represents the longest follow-up period for a patient with chronic Q fever in the United States. We review all cases of chronic Q fever reported in the United States and discuss important issues pertaining to epidemiology, diagnosis, and management of this disease.

Q fever endocarditis in the United States

Infections due to Coxiella burnetii, the causative organism of Q fever, are extremely rare in North America. Endocarditis due to the organism has an unusual presentation and poses echocardiographic and laboratory challenges in establishing a diagnosis. We describe the presentation and clinical course of a 40-year-old American man with Q fever endocarditis and briefly discuss the salient issues regarding this entity.

Q fever in humans and animals in the United States

Coxiella burnetii, the etiologic agent of Q fever, is a worldwide zoonotic pathogen. Although Q fever is present in the United States, little is known about its current incidence or geographic distribution in either humans or animals. Published reports of national disease surveillance, individual cases, outbreak investigations, and serologic surveys were reviewed to better characterize Q fever epidemiology in the United States. In national disease surveillance reports for 1948-1986, 1,396 human cases were reported from almost every state. Among published individual case reports and outbreak investigations, occupational exposures (research facilities, farm environments, slaughterhouses) were commonly reported, and sheep were most frequently implicated as a possible source of infection. In studies conducted on specific groups, livestock handlers had a significantly higher prevalence of antibodies to C. burnetii than did persons with no known risk. Animal studies showed wide variation in seroprevalence, with goats having a significantly higher average seroprevalence (41.6%) than sheep (16.5%) or cattle (3.4%). Evidence of antibody to C. burnetii was reported among various wild-animal species, including coyotes, foxes, rodents, skunks, raccoons, rabbits, deer, and birds. This literature review suggests that C. burnetii is enzootic among ruminants and wild animals throughout much of the United States and that there is widespread human exposure to this pathogen. Sheep and goats appear to be a more important risk for human infection in the United States than cattle or wild animals, and research studies examining the natural history and transmission risk of Q fever in sheep and goats in this country should be encouraged.

Doxycycline and chloroquine as treatment for chronic Q fever endocarditis

Endocarditis is a rare but severe complication of Q fever, an infectious disease caused by the intracellular pathogen Coxiella burnetii. Heart involvement is the most common clinical presentation of chronic Q fever, and it occurs almost invariably in patients with previous valvular disease or artificial valves, and in the immunocompromised host. The optimal treatment of Q fever endocarditis is still today debated, and recommended duration of treatment varies from one year to one's lifespan. A case of chronic Q fever endocarditis is described in a patient with biological prosthetic aortic valve and aortic homograft, successfully treated with doxycycline and chloroquine for 2 years.

Q fever endocarditis in Israel and a worldwide review

The worldwide epidemiology and population-based incidence of Q fever endocarditis (QFE) have been less well studied than those for uncomplicated Q fever. An exhaustive literature review revealed 408 patients with QFE reported between 1949 and 1994, mostly from 3 large geographic areas. Underlying valvular heart disease was almost invariably present, and 38% had prosthetic valves. The most common clinical manifestations were fever and congestive heart failure. The mortality rate dropped over the years from 65% to 25%, but a meta-analysis of published data showed the death rate to be significantly lower among patients receiving combination therapy (12/65, 18%), as compared to patients treated with tetracycline alone (18/41, 44%, p = 0.005). A 10-year (1983-1992) retrospective nationwide survey of QFE in Israel revealed 35 patients with QFE, representing an annual incidence of 0.75 cases per 1 million population. Underlying heart disease, clinical manifestations and outcome in the Israeli group were not substantially different from those described in the world literature. The current state-of-the-art clinical approach includes early diagnosis, prompt initiation of combination therapy for at least 3 years, and long-term clinical and serologic follow-up. Adherence to these rules might have contributed to the improved prognosis in recent years.

Heart transplantation for Q fever endocarditis

A 30-year-old man underwent aortic and mitral valve replacement for the treatment of Q fever endocarditis. Postoperatively, paravalvular leak of the mitral prosthesis, progressive deterioration in cardiac function, and intractable heart failure developed. As a result, the patient underwent orthotopic heart transplantation 15 months after his initial valve operation. The patient is clinically well 14 months after transplantation.

Antibiotic susceptibilities of two Coxiella burnetii isolates implicated in distinct clinical syndromes

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.

Susceptibility of Coxiella burnetii to pefloxacin and ofloxacin in ovo and in persistently infected L929 cells

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.

In vitro susceptibility of Coxiella burnetii to antibiotics, including several quinolones

Antibiotic susceptibility testing of the rickettsial Q fever agent Coxiella burnetii was performed by using persistently infected L929 fibroblast cells. The efficacies of a variety of antibiotics with different metabolic targets were tested and compared. The most effective antibiotics in bringing about the elimination of the parasite from infected cells included several quinolone compounds and rifampin. Of the quinolone compounds tested, difloxacin (A-56619) was the most effective, followed by ciprofloxacin and oxolinic acid. These three quinolones were apparently rickettsiacidal. After 48 h of exposure to microgram amounts of the compounds (ranging from 2 micrograms of difloxacin per ml to 5 micrograms of the other two antibiotics per ml), the number of intracellular parasites markedly declined; after 10 days of treatment, very few intracellular rickettsiae were detected. Rifampin (1 microgram/ml) was also very effective in eliminating the parasites. Some of the 13 other antibiotics tested that were somewhat effective included chloramphenicol, doxycycline, and trimethoprim. The persistently infected L929 cells were found to provide a convenient system for the relatively rapid determination of the susceptibility of C. burnetii to antibiotics.