Coxiella burneti endocarditis in a patient with positive chlamydial serology

High Seroprevalence of Mycoplasma pneumoniae and Chlamydia pneumoniae among Scrub Typhus Patients in South Korea

Scrub typhus is an acute febrile illness caused by the obligate intracellular organism Orientia tsutsugamushi, endemic to South Korea. The course of scrub typhus can range from a self-limiting disease to a fatal illness. Serological cross-reactivity has been reported with other intracellular organisms, including Rickettsia species, Chlamydophila species, and Mycoplasma pneumoniae. We conducted a retrospective study to assess the current seroprevalence of M. pneumoniae IgM and Chlamydia pneumoniae IgM in scrub typhus patients in South Korea. We enrolled 150 patients with suspected rickettsial disease over the course of 2 years. Of these patients, 60 were confirmed to have scrub typhus and had paired acute and convalescent serum. Among the 60 scrub typhus patients, 40 (66.7%) had M. pneumoniae IgM and 19 (31.7%) had C. pneumoniae IgM in acute- or convalescent phase sera. The seroconversion rates of M. pneumoniae IgG and IgM were 16.7% and 33.3%, respectively. The seroconversion rates of C. pneumoniae IgG and IgM were 8.3% and 11.7%, respectively. Compared with previous study results, this may indicate a relatively high seroprevalence of M. pneumoniae IgM and C. pneumoniae IgM in scrub typhus patients, indicating possible misdiagnosis of M. pneumoniae and C. pneumoniae infections in non-endemic scrub typhus areas.

Unusual manifestations of acute Q fever: autoimmune hemolytic anemia and tubulointerstitial nephritis

Q fever is a worldwide zoonotic infection that caused by Coxiella burnetii, a strict intracellular bacterium. It may be manifested by some of the autoimmune events and is classified into acute and chronic forms. The most frequent clinical manifestation of acute form is a self-limited febrile illness which is associated with severe headache, muscle ache, arthralgia and cough. Meningoencephalitis, thyroiditis, pericarditis, myocarditis, mesenteric lymphadenopathy, hemolytic anemia, and nephritis are rare manifestations. Here we present a case of acute Q fever together with Coombs’ positive autoimmune hemolytic anemia (AIHA) and tubulointerstitial nephritis treated with chlarithromycin, steroids and hemodialysis. Clinicians should be aware of such rare manifestations of the disease.

Getting to the heart of the problem: serological and molecular techniques in the diagnosis of infective endocarditis

Infective endocarditis is diagnosed using the Duke criteria, which rely predominantly on cardiac imaging and recovery of a causative organism from the bloodstream. These criteria can be inconclusive, particularly when blood cultures remain sterile either due to the fastidious nature of the infecting organism or prior antibiotic therapy. Serology and, more recently, molecular techniques have been investigated as a solution to the problematic negative blood culture. The detection of elevated antibody levels has proved particularly useful in the diagnosis of those patients infected with organisms that cannot be cultured using standard laboratory methods, whilst molecular methods have been successfully used in the detection of both fastidious pathogens and those inhibited by prior antibiotic therapy. In view of recent and ongoing developments in the field of molecular diagnostics, these techniques will become increasingly important not only in the routine investigation of infectious disease, but specifically the diagnosis of endocarditis.

Concomitant or consecutive infection with Coxiella burnetii and tickborne diseases

BACKGROUND

Q fever is a worldwide zoonosis caused by Coxiella burnetii, which can be isolated from ticks. Reports of people with both Q fever and other tickborne diseases are rare. In this study, we describe 6 patients with Q fever who were infected with 1 of the following tickborne pathogens: Rickettsia conorii (2 patients), Rickettsia slovaca (2), Rickettsia africae (1), and Francisella tularensis (1).

METHODS

Diagnoses were made on the basis of results of microimmunofluorescence assays for detection of C. burnetii, R. conorii, R. slovaca, R. africae, and F. tularensis antigens. Cross-adsorption studies and Western blots were used to confirm dual infections.

RESULTS

Among the 6 cases presented, 3 were probably due to a concomitant infection after a tick bite, whereas the remaining 3 were more likely consecutive infections.

CONCLUSIONS

Because acute Q fever is often asymptomatic, we recommend that patients infected with the tickborne pathogens mentioned above also undergo routine testing for concurrent infections with C. burnetii.

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.