Cecilia Y. Kato

Assessment of Real-Time PCR Assay for Detection of Rickettsia spp. and Rickettsia rickettsii in Banked Clinical Samples

ABSTRACT Two novel real-time PCR assays were developed for the detection of Rickettsia spp. One assay detects all tested Rickettsia spp.; the other is specific for Rickettsia rickettsii. Evaluation using DNA from human blood and tissue samples showed both assays to be more sensitive than nested PCR assays currently in use at the CDC.

Rickettsia parkeri Rickettsiosis in Different Ecological Regions of Argentina and Its Association with Amblyomma tigrinum as a Potential Vector

Rickettsia parkeri, a newly recognized tick-borne pathogen of humans in the Americas, is a confirmed cause of spotted fever group rickettsiosis in Argentina. Until recently, almost all cases of R. parkeri rickettsiosis in Argentina have originated from the Paraná River Delta, where entomological surveys have identified populations of R. parkeri-infected Amblyomma triste ticks. In this report, we describe confirmed cases of R. parkeri rickettsiosis from Córdoba and La Rioja provinces, which are located several hundred kilometers inland, and in a more arid ecological region, where A. triste ticks do not occur. Additionally, we identified questing A. tigrinum ticks naturally infected with R. parkeri in Córdoba province. These data provide evidence that another human-biting tick species serves as a potential vector of R. parkeri in Argentina and possibly, other countries of South America.

Rickettsia parkeri Rickettsiosis, Arizona, USA

The likely vector was Amblyomma triste, a Neotropical tick species only recently recognized in the United States.

Inadequacy of IgM antibody tests for diagnosis of Rocky Mountain Spotted Fever.

Among 13 suspected Rocky Mountain spotted fever (RMSF) cases identified through an enhanced surveillance program in Tennessee, antibodies to Rickettsia rickettsii were detected in 10 (77%) patients using a standard indirect immunofluorescent antibody (IFA) assay. Immunoglobulin M (IgM) antibodies were observed for 6 of 13 patients (46%) without a corresponding development of IgG, and for 3 of 10 patients (30%) at least 1 year post-onset. However, recent infection with a spotted fever group rickettsiae could not be confirmed for any patient, based on a lack of rising antibody titers in properly timed acute and convalescent serologic specimens, and negative findings by polymerase chain reaction testing. Case definitions used in national surveillance programs lack specificity and may capture cases that do not represent current rickettsial infections. Use of IgM antibodies should be reconsidered as a basis for diagnosis and public health reporting of RMSF and other spotted fever group rickettsiae in the United States.

Co-Infection of Rickettsia rickettsii and Streptococcus pyogenes: Is Fatal Rocky Mountain Spotted Fever Underdiagnosed?

Rocky Mountain spotted fever, a tick-borne disease caused by Rickettsia rickettsii, is challenging to diagnose and rapidly fatal if not treated. We describe a decedent who was co-infected with group A β-hemolytic streptococcus and R. rickettsii. Fatal cases of Rocky Mountain spotted fever may be underreported because they present as difficult to diagnose co-infections.

Coxiella burnetii Infection in a Community Operating a Large-Scale Cow and Goat Dairy, Missouri, 2013

Coxiella burnetii is a zoonotic pathogen that causes Q fever in humans and is transmitted primarily from infected goats, sheep, or cows. Q fever typically presents as an acute febrile illness; however, individuals with certain predisposing conditions, including cardiac valvulopathy, are at risk for chronic Q fever, a serious manifestation that may present as endocarditis. In response to a cluster of Q fever cases detected by public health surveillance, we evaluated C. burnetii infection in a community that operates a large-scale cow and goat dairy. A case was defined as an individual linked to the community with a C. burnetii phase II IgG titer ≥ 128. Of 135 participants, 47 (35%) cases were identified. Contact with or close proximity to cows, goats, and their excreta was associated with being a case (relative risk 2.7, 95% confidence interval 1.3-5.3). Cases were also identified among individuals without cow or goat contact and could be related to windborne spread or tracking of C. burnetii on fomites within the community. A history of injection drug use was reported by 26/130 (20%) participants; follow-up for the presence of valvulopathy and monitoring for development of chronic Q fever may be especially important among this population.

Estimation of Rickettsia rickettsii copy number in the blood of patients with Rocky Mountain spotted fever suggests cyclic diurnal trends in bacteraemia

Infection with Rickettsia rickettsii, an obligate intracellular Gramnegative bacterium, causes Rocky Mountain spotted fever (RMSF), one of the most lethal of all known infectious diseases. Because R. rickettsii infects predominantly fixed endothelial cells of smalland medium-size blood vessels, there are few quantitative assessments of bacteraemia for RMSF, and limited data suggest that low numbers of R. rickettsii circulate in the peripheral blood of ill patients [1]. This observation was described by early investigators who recognized that R. rickettsii bacteria could scarcely be found in stained peripheral blood smears of patients, even those with severe disease [2].We used TaqMan real-time PCR to evaluate levels of rickettsial DNA in a series of clinical samples obtained from patients with RMSF. Whole blood (n = 23), serum (n = 6) and plasma (n = 1) specimens were collected from 13 U.S. patients with RMSF from 2010 to 2015 and submitted to the Rickettsial Zoonoses Branch Reference Diagnostic Laboratory at the Centers for Disease Control and Prevention (Supplementary Table 1). Individual specimens were accompanied by clinical information that varied in completeness. Each sample was positive for PanR8 Rickettsia spp. and RRi6 R. rickettsii–specific targets [3], with controls performing as expected (Supplementary Fig. 1). RMSF specimens were quantified with PanR8 in duplicate (undiluted or 1:10) using tenfold dilutions of R. rickettsii DNA from 0.1 fg to 10.0 pg (1 fg = 0.8282 copies). Samples from patients with fatal (n = 20) and nonfatal (n = 10) outcomes ranged from 1.41 × 10 ± 2.78 × 10 to 2.05 × 10 ± 1.89 × 10 copies/mL (median = 1.63 × 10), and

Diagnosis of Spotted Fever Group Rickettsioses in U.S. Travelers Returning from Africa, 2007–2016

Spotted fever group rickettsioses (SFGRs), such as African tick bite fever (ATBF), are among the most commonly diagnosed diseases for ill travelers returning from southern Africa. We summarized demographic, clinical, and diagnostic features of imported SFGR cases in U.S. travelers returning from Africa who had laboratory specimens submitted to the Centers for Disease Control and Prevention. Diagnosis of SFGR was performed by indirect immunofluorescence antibody assay, immunohistochemical staining, polymerase chain reaction (PCR), or culture. Cases were defined as probable SFGR, confirmed SFGR, or confirmed ATBF. Clinical and epidemiological categorical variables were described as counts and proportions; continuous variables were described using geometric mean titers, median, and range. One hundred and twenty-seven patients satisfied laboratory criteria for confirmed or probable SFGR. Fever was the most common symptom (N = 88; 69%), followed by ≥ 1 eschars (N = 70; 55%). Paired serums were submitted for 36 patients (28%); 12 patients (33%) had nonreactive initial serum sample but converted to a titer ≥ 64 with the convalescent sample. Twenty-seven patients (21%) had infection with Rickettsia africae based on PCR analysis of eschar swab (N = 8) or biopsy (N = 23). Fifteen patients had eschar biopsy or swab samples and serum sample(s) submitted together; 9 (60%) had PCR-positive eschar results and nonreactive acute serology. Health-care providers should consider SFGR when evaluating patients for a febrile illness with eschar and compatible foreign travel history. Polymerase chain reaction testing of eschar biopsies or swabs provides a confirmed diagnosis in early stages of disease; eschar swabs or biopsies are an underutilized diagnostic technique.