Antimicrobial therapy of rickettsial diseases

A Brief History of the Major Rickettsioses in the Asia-Australia-Pacific Region: A Capstone Review for the Special Issue of TMID

The rickettsioses of the "Far East" or Asia-Australia-Pacific region include but are not limited to endemic typhus, scrub typhus, and more recently, tick typhus or spotted fever. These diseases embody the diversity of rickettsial disease worldwide and allow us to interconnect the various contributions to this special issue of Tropical Medicine and Infectious Disease. The impact of rickettsial diseases-particularly of scrub typhus-was substantial during the wars and "police actions" of the last 80 years. However, the post-World War II arrival of effective antibiotics reduced their impact, when recognized and adequately treated (chloramphenicol and tetracyclines). Presently, however, scrub typhus appears to be emerging and spreading into regions not previously reported. Better diagnostics, or higher population mobility, change in antimicrobial policies, even global warming, have been proposed as possible culprits of this phenomenon. Further, sporadic reports of possible antibiotic resistance have received the attention of clinicians and epidemiologists, raising interest in developing and testing novel diagnostics to facilitate medical diagnosis. We present a brief history of rickettsial diseases, their relative importance within the region, focusing on the so-called "tsutsugamushi triangle", the past and present impact of these diseases within the region, and indicate how historically, these often-confused diseases were ingeniously distinguished from each another. Moreover, we will discuss the importance of DNA-sequencing efforts for Orientia tsutsugamushi, obtained from patient blood, vector chiggers, and rodent reservoirs, particularly for the dominant 56-kD type-specific antigen gene (tsa56), and whole-genome sequences, which are increasing our knowledge of the diversity of this unique agent. We explore and discuss the potential of sequencing and other effective tools to geographically trace rickettsial disease agents, and develop control strategies to better mitigate the rickettsioses.

Post-fever retinitis - Newer concepts

Post-fever retinitis (PFR) is an infectious or para-infectious uveitic entity caused by bacterial or viral agents and seen mainly in tropical countries. Systemic symptoms such as joint pain, skin rash are common during the febrile stage. On the basis of only clinical presentation, it is difficult to pin-point the exact etiology for PFR. Serological investigations, polymerase chain reaction, and knowledge of concurrent epidemics in the community may help to identify the etiological organism. Bacterial causes of PFR such as rickettsia and typhoid are treated with systemic antibiotics, with or without systemic steroid therapy, whereas PFR of viral causes such as chikungunya, dengue, West Nile virus, and Zika virus have no specific treatment and are managed with steroids. Nevertheless, many authors have advocated mere observation and the uveitis resolved with its natural course of the disease. In this article, we have discussed the clinical features, pathogenesis, investigations, and management of PFR.

Susceptibility of Rickettsia rickettsii to Tigecycline in a Cell Culture Assay and Animal Model for Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF), caused by Rickettsia rickettsii, is a severe tick-borne infection endemic to the Americas. Oral doxycycline is effective, but during severe life-threatening disease, intravenous therapy is recommended. Unfortunately, intravenous formulations of doxycycline are not always available. Therefore, we aimed to determine the susceptibility of R. rickettsii to an alternative parenteral agent, tigecycline, in vitro and in vivo. To determine the minimum inhibitory concentration of tigecycline, R. rickettsii-inoculated Vero cells were incubated with medium containing tigecycline. At various time points, monolayers were collected and R. rickettsii was quantified via real-time polymerase chain reaction (PCR). The growth of R. rickettsii was inhibited in the presence of ≥ 0.5 µg/mL of tigecycline. To determine the effectiveness of tigecycline in vivo, guinea pigs were inoculated with R. rickettsii. Five days after inoculation, they were treated twice daily with subcutaneous tigecycline 3.75 mg/kg or subcutaneous doxycycline 5 mg/kg. Treated animals improved, whereas untreated controls remained ill. Tissues were collected for quantitative PCR-determined bacterial loads on day 8. Median bacterial loads in the tigecycline group were less than those in untreated animals: liver (0 versus 2.9 × 10⁴ copies/mg), lung (0 versus 8.3 × 10³ copies/mg), skin (2.6 × 10² versus 2.2 × 10⁵ copies/mg), spleen (0 versus 1.3 × 10⁴ copies/mg), and testes (0 versus 1.0 × 10⁵ copies/mg, respectively). There were no significant differences in the bacterial loads between doxycycline-treated versus tigecycline-treated guinea pigs. These data indicate that tigecycline is effective against R. rickettsii in cell culture and in an animal model of RMSF.

Molecular confirmation & characterization of Rickettsia conorii in north India: A report of three cases

Background & objectives

In India, spotted fever group rickettsiae (SFGR) are an underdiagnosed cause of acute febrile illness (AFI). The non-specific Weil-Felix test is the first diagnostic modality for the diagnosis of SFGR in many laboratories due to the lack of advanced diagnostic facilities in developing countries. The aim of this study was to detect SFGR using molecular methods in the patients, presenting with AFI in a tertiary care centre in north India.

Methods

Consecutive patients (>14 yr of age) with AFI were enrolled over a six month period. Standard investigations for common pathogens causing AFI in India (malaria, dengue, scrub typhus, leptospirosis and enteric fever) were carried out. In patients who were negative for all of the above investigations, blood was subjected to polymerase chain reaction (PCR) targeting outer membrane protein A (ompA) gene of Rickettsia.

Results

Of the 51 patients with an undiagnosed aetiology, three were positive by ompA PCR. Two of the PCR products produced good sequences and BLAST identification confirmed them as Rickettsia conorii. The sequences of R. conorii reported from south India clustered with two previously reported novel rickettsial genotypes. The study sequences clustered in a group different from that of Rickettsia spp. of the south Indian sequences reported earlier.

Interpretation & conclusions

This study showed the existence of R. conorii in north India. Testing for SFGR may be included in the diagnostic workup of AFI for better disease management.

Spotted fever rickettsiosis presenting with bilateral anterior uveitis and retinitis: A case report

Spotted fever is a common rickettsial disease in India. It is caused by Rickettsia conorii, which demonstrates vascular tropism and causes endothelial injury. Ocular manifestations include multifocal retinitis and disc edema. Anterior uveitis as a presenting feature of spotted fever is uncommon. We present a 32-year-old man with spotted fever and bilateral anterior uveitis.

Novel high-throughput screening method using quantitative PCR to determine the antimicrobial susceptibility of Orientia tsutsugamushi clinical isolates

Objectives

To develop a method to enable the large-scale antimicrobial susceptibility screening of Orientia tsutsugamushi clinical isolates, using one timepoint and one concentration of antibiotics to considerably speed up the time to result.

Methods

Growth, harvesting, multiplicity of infection (moi) and the day to determine the MICs were optimized using five O. tsutsugamushi reference strains [susceptible (Karp, Kato and Gilliam) and putatively resistant (AFC-3 and AFSC-4)], one clinical isolate (UT76) and one rodent isolate (TA763). Subsequently, the MICs of azithromycin, chloramphenicol and doxycycline for these strains and 51 clinical isolates including AFSC-7 were determined. An optimal concentration was calculated using the epidemiological cut-off value.

Results

The conditions for O. tsutsugamushi infection, growth and harvesting were determined to be an moi of 100:1 and trypsinization with the peak growth on day 10. The resulting MICs were in line with previously published susceptibility data for all reference strains, except for Karp and AFSC-4, which showed azithromycin MICs of 0.0156 and 0.0313 mg/L, compared with 0.0078 and 0.0156 mg/L, respectively, in previous reports. The MIC of doxycycline for AFC-3 was 0.125 mg/L compared with >4 mg/L in earlier reports. The final single screening concentrations were identified as: azithromycin, 0.125 mg/L; chloramphenicol, 8 mg/L; and doxycycline, 1 mg/L.

Conclusions

This simplified procedure facilitates the simultaneous screening of 48 isolates for actively monitoring potential resistance of this important fever pathogen, with an 8-fold throughput improvement over early methods. The data do not support the existence of doxycycline- and chloramphenicol-resistant scrub typhus.

South African Tick Bite Fever: An Overview

The rickettsiae are a diverse group of vector-borne zoonotic bacterial pathogens. The two common spotted fever diseases in existence in southern Africa are boutonneuse fever-like tick bite fever (TBF), caused by Rickettsia conorii, and African TBF, caused by R. africae. This review addresses demographic, epidemiological, clinical, diagnostic, therapeutic, and preventive aspects of TBF in the southern African context, including a discussion of the dermatopathological findings and potential diagnostic pitfalls.

Prospective Cohort Study of Single-Day Doxycycline Therapy for Mediterranean Spotted Fever

The objective of this study is to evaluate the results of single-day doxycycline therapy for Mediterranean spotted fever (MSF). This is a prospective cohort study of cases with confirmed MSF treated with the single-day doxycycline regimen in a teaching hospital from 1990 to 2015. Patients received two oral doses of 200 mg of doxycycline for 1 day. The outcomes evaluated were the time interval between the start of treatment and apyrexia, the time interval between the start of treatment and disappearance of other symptoms, and the adverse reactions to treatment and death. The study included 158 subjects, 18 of whom (11.4%) had a severe form of MSF and 31 (19.6%) were >65 years. The interval between onset of symptoms and start of treatment was 4.31 ± 1.54 days. All patients recovered uneventfully. Fever disappeared 2.55 ± 1.14 days after the start of treatment. The remaining symptoms (headache, arthromyalgia) disappeared 3.63 ± 1.35 days after the start of treatment. Only one patient had a delay in reaching apyrexia (8 days). The fever disappeared somewhat later in severe cases (median, 3 days; interquartile range [IQR], 2 to 4 days) than in nonsevere cases (median, 2 days; IQR, 2 to 3 days). Likewise, the remaining symptoms disappeared later in severe cases (median, 5 days; IQR, 4 to 6 days) than in nonsevere cases (median, 3 days; IQR, 3 to 4 days). The outcome was similar in both elderly and nonelderly patients. Eight patients had mild adverse effects possibly related to treatment. The results of the study confirm that single-day doxycycline therapy is an effective and well-tolerated treatment for MSF, including elderly patients and severe cases.

The Historical Case for and the Future Study of Antibiotic-Resistant Scrub Typhus

Scrub typhus is an acute, and sometimes fatal, human febrile illness, typically successfully treated using chloramphenicol or one of the tetracyclines. Over the past several years, descriptions of strains of Orientia tsutsugamushi with reduced susceptibility to antibiotics have appeared. Because case-fatality ratios approached 50% during the pre-antibiotic era, antibiotic-resistant scrub typhus is concerning. Herein, we review the data on resistant scrub typhus, describe how the theoretical existence of such resistance is affected by interpretation of treatment outcomes, and propose a plan to further identify whether true drug resistance is present and how to deal with drug resistance if it has evolved. Limited resistance is not unambiguous, if present, and antibiotic resistance in scrub typhus is not a dichotomous trait. Rather, evidence of resistance shows a continuous gradation of increasing resistance. The availability of genomes from isolates of O. tsutsugamushi allows the search for loci that might contribute to antibiotic resistance. At least eighteen such loci occur in all genomes of O. tsutsugamushi examined. One gene (gyrA) occurs as a quinolone-resistant form in the genome of all isolates of O. tsutsugamushi. At least 13 other genes that are present in some members of the genus Rickettsia do not occur within O. tsutsugamushi. Even though reports of scrub typhus not responding appropriately to chloramphenicol or a tetracycline treatment have been in the literature for approximately 23 years, the existence and importance of antibiotic-resistant scrub typhus remains uncertain.

Seroprevalence against Rickettsia and Borrelia Species in Patients with Uveitis: A Prospective Survey

Vector-borne diseases such as Lyme borreliosis and rickettsioses have been associated with ocular inflammation. Our aim was to study patients with diagnosed uveitis to evaluate serological signs of infection or exposure to these tick-borne agents. Forty-eight patients were prospectively examined with serology together with medical records and a questionnaire concerning previous exposure, diseases, and treatments. Seven patients (14.6%) showed seroconversion to Rickettsia spp. between acute and convalescent phase sera, which provides support for a positive Rickettsia diagnosis according to guidelines. The specificity was confirmed by Western blot. Additional 28 patients had stationary titres of which eight (16.6%) had 1 : 256 or higher titre in the first serum, and another 13 patients were seronegative. No epidemiological risk factor or marker could be identified. For Borrelia, only three patients showed moderate IgG titres. A control group of 100 blood donors, 60 patients with rheumatic disease, and 56 patients seeking medical care were tested of which 2.0–7.1% showed low anti-Rickettsia titres and 3.0–8.3% anti-Borrelia titres. The findings are indicative for an association between infection or exposure to Rickettsia spp. and uveitis with a seropositivity among patients with recurrent uveitis in concordance with the spread of rickettsial exposure in a tick-exposed population.

First isolation of Rickettsia monacensis from a patient in South Korea

A Rickettsia sp. was isolated from the blood of a patient with an acute febrile illness using the shell vial technique; the isolate was named CN45Kr and was identified by molecular assay as Rickettsia monacensis, which was first recognized as a pathogen in Spain. Sequencing analysis showed that the gltA sequence of the isolate was identical to that of Rickettsia sp. IRS3. The ompA-5mp fragment sequence showed 100% identity to those of R. monacensis and Rickettsia sp. In56 and ompA-3pA In56 and 100% identity to that of Rickettsia sp. IRS3. The ompB sequence was found to have 99.9% similarity to that of R. monacensis IrR/Munich. This study confirms the pathogenicity of this agent and provides additional information about its geographic distribution.

African Tick Bite Fever Treated Successfully With Rifampin in a Patient With Doxycycline Intolerance

African tick bite fever is the most commonly encountered travel-associated rickettsiosis, occurring in as many as 5% of travelers returning from rural subequatorial Africa. This case report illustrates that rifampin represents an effective alternative to doxycycline for treatment of African tick bite fever in some selective situations.

Central Nervous System Infection Associated with Orientia tsutsugamushi in South Korea

Orientia tsutsugamushi is a major cause of vector-borne infection in Asia. Prompt recognition and appropriate treatment are crucial because of its potentially fatal complications and lack of response to beta-lactam antibiotics. The present study retrospectively evaluated the clinical characteristics and laboratory findings of 16 patients with scrub typhus-related central nervous system (CNS) infections. Single titers ≥ 1:40 of total serum antibodies against O. tsutsugamushi detected by an indirect immunofluorescent assay were considered as positive results. The median age was 35.5 (range, 14-72) years, and 10 (62.5%) patients were female. The most common symptoms were headache (81.3%) and fever (81.3%). Eschar formation was found in three (18.8%) patients. Among patients with encephalitis, seizures and altered consciousness occurred in five (83.3%) and four (66.7%) patients, respectively. An abnormal liver function was noted in seven (43.8%) patients. The median antibody titer was 1:120 (range, 1:40-1:2,560). Typical cerebrospinal fluid profiles were lymphocytic pleocytosis, mild protein elevations, and normal glucose levels. All patients received an empirical treatment with doxycycline and most (93.8%) of them recovered without neurological sequelae. None of the patients reported side effects of the doxycycline treatment. An empirical treatment with doxycycline is needed in patients with CNS infections in scrub typhus endemic areas.

Azithromycin and Doxycycline Attenuation of Acanthamoeba Virulence in a Human Corneal Tissue Model

Background

Amoebic keratitis is a potentially blinding eye infection caused by ubiquitous, free-living, environmental acanthamoebae, which are known to harbor bacterial endosymbionts. A Chlamydia-like endosymbiont has previously enhanced Acanthamoeba virulence in vitro. We investigated the potential effect of Acanthamoeba-endosymbiont coinfection in a human corneal tissue model representing clinical amoebic keratitis infection.

Methods

Environmental and corneal Acanthamoeba isolates from the American Type Culture Collection were screened for endosymbionts by amplifying and sequencing bacterial 16S as well as Chlamydiales-specific DNA. Each Acanthamoeba isolate was used to infect EpiCorneal cells, a 3-dimensional human corneal tissue model. EpiCorneal cells were then treated with azithromycin, doxycycline, or control medium to determine whether antibiotics targeting common classes of bacterial endosymbionts attenuated Acanthamoeba virulence, as indicated by decreased observed cytopathic effect and inflammatory biomarker production.

Results

A novel endosymbiont closely related to Mycobacterium spp. was identified in Acanthamoeba polyphaga 50495. Infection of EpiCorneal cells with Acanthamoeba castellanii 50493 and A. polyphaga 50372 led to increased production of inflammatory cytokines and cytopathic effects visible under microscopy. These increases were attenuated by azithromycin and doxycycline.

Conclusions

Our findings suggest that azithromycin and doxycycline may be effective adjuvants to standard antiacanthamoebal chemotherapy by potentially abrogating virulence-enhancing properties of bacterial endosymbionts.

A human time dose response model for Q fever

The causative agent of Q fever, Coxiella burnetii, has the potential to be developed for use in biological warfare and it is classified as a bioterrorism threat agent by the Centers for Disease Control and Prevention (CDC) and as a category B select agent by the National Institute of Allergy and Infectious Diseases (NIAID). In this paper we focus on the in-host properties that arise when an individual inhales a dose of C. burnetii and establish a human time-dose response model. We also propagate uncertainty throughout the model allowing us to robustly estimate key properties including the infectious dose and incubation period. Using human study data conducted in the 1950's we conclude that the dose required for a 50% probability of infection is about 15 organisms, and that one inhaled organism of C. burnetti can cause infection in 5% of the exposed population. In addition, we derive a low dose incubation period of 17.6 days and an extracellular doubling time of half a day. In conclusion this paper provides a framework for detailing the parameters and approaches that would be required for risk assessments associated with exposures to C. burnetii that might cause human infection.

Rickettsiae as Emerging Infectious Agents

With advances in molecular genetics, more pathogenic rickettsial species have been identified. Pathogenic rickettsiae are transmitted by vectors, such as arthropods, into the patient's skin and then spread into the microvascular endothelial cells. Clinical manifestations are characterized by fever with headache and myalgias, followed by rash 3 to 5 days later. The undifferentiated nature of clinical symptoms, knowledge of the epidemiology, and the patient's history of travel and exposure to arthropod vectors are critical to the empiric administration of antimicrobial therapy. Doxycycline is currently the most effective antibiotic for treatment of all spotted fever group and typhus group rickettsioses.

Preparing for biological threats: Addressing the needs of pregnant women

Intentional release of infectious agents and biological weapons to cause illness and death has the potential to greatly impact pregnant women and their fetuses. We review what is known about the maternal and fetal effects of seven biological threats: Bacillus anthracis (anthrax); variola virus (smallpox); Clostridium botulinum toxin (botulism); Burkholderia mallei (glanders) and Burkholderia pseudomallei (melioidosis); Yersinia pestis (plague); Francisella tularensis (tularemia); and Rickettsia prowazekii (typhus). Evaluating the potential maternal, fetal, and infant consequences of an intentional release of an infectious agent requires an assessment of several key issues: (1) are pregnant women more susceptible to infection or illness compared to the general population?; (2) are pregnant women at increased risk for severe illness, morbidity, and mortality compared to the general population?; (3) does infection or illness during pregnancy place women, the fetus, or the infant at increased risk for adverse outcomes and how does this affect clinical management?; and (4) are the medical countermeasures recommended for the general population safe and effective during pregnancy? These issues help frame national guidance for the care of pregnant women during an intentional release of a biological threat. Birth Defects Research 109:391-398, 2017.© 2017 Wiley Periodicals, Inc.

CNS Manifestations in Orientia tsutsugamushi Disease (Scrub Typhus) in North India

OBJECTIVE

To present the clinical, lab profile and outcome of a series of six children who had features of meningoencephalitis (median age of 10.5 y) diagnosed as confirmed scrub typhus (ST) by using a lgM ELISA commercial kit (InBiOS International Inc. USA).

METHODS

This was a prospective observational study conducted at a tertiary care hospital, over a period of 7 mo through April 2014. All the patients with undifferentiated febrile illness (aged 1-18 y) with fever of 5-21 d duration were evaluated. After thorough physical examination they were subjected to blood investigations such as complete blood count (CBC), blood culture, hepatic and kidney function tests, serum electrolytes, cerebrospinal fluid (CSF) analysis and IgM ELISA for scrub typhus, coagulogram and chest radiograph, wherever indicated.

RESULTS

During this period, of the total 81 confirmed cases based on a positive scrub IgM ELISA and/or eschar, 6 (7.4 %), had neurological involvement in the form of presence of neck stiffness, altered sensorium and/or seizures and the CSF findings were suggestive of meningoencephalitis and all had evidence of multiple organ dysfunction syndrome (MODS) needing intensive care. The CECT could be performed in four patients only showing evidence of effacement of sulci and evidence of brain edema.

CONCLUSIONS

This communication highlights that variable central nervous system (CNS) involvement is not uncommon in patients with scrub typhus with high mortality. CSF and neuro-radiology findings are nonspecific as these are also observed in patients with aseptic meningitis or encephalitis. Early suspection and institution of appropriate therapy without delay will lead to substantial reduction in the morbidity and mortality.

Revisiting doxycycline in pregnancy and early childhood--time to rebuild its reputation?

Introduction: Doxycycline is highly effective, inexpensive with a broad therapeutic spectrum and exceptional bioavailability. However these benefits have been overshadowed by its classification alongside the tetracyclines – class D drugs, contraindicated in pregnancy and in children under 8 years of age. Doxycycline-treatable diseases are emerging as leading causes of undifferentiated febrile illness in Southeast Asia. For example scrub typhus and murine typhus have an unusually severe impact on pregnancy outcomes, and current mortality rates for scrub typhus reach 12-13% in India and Thailand. The emerging evidence for these important doxycycline-treatable diseases prompted us to revisit doxycycline usage in pregnancy and childhood.

Areas Covered: A systematic review of the available literature on doxycycline use in pregnant women and children revealed a safety profile of doxycycline that differed significantly from that of tetracycline; no correlation between the use of doxycycline and teratogenic effects during pregnancy or dental staining in children was found.

Expert Opinion: The change of the US FDA pregnancy classification scheme to an evidence-based approach will enable adequate evaluation of doxycycline in common tropical illnesses and in vulnerable populations in clinical treatment trials, dosage-optimization pharmacokinetic studies and for the empirical treatment of undifferentiated febrile illnesses, especially in pregnant women and children.

Minocycline as A Substitute for Doxycycline in Targeted Scenarios: A Systematic Review

Doxycycline remains on intermittent shortage. Evidence supports the substitution of minocycline in skin and soft-tissue infections and carefully selected cases of pneumonia. Minocycline may be carefully considered in Lyme disease prophylaxis and Rickettsial disease in the complete absence of doxycycline.

Doxycycline, a commonly prescribed tetracycline, remains on intermittent shortage. We systematically reviewed the literature to assess minocycline as an alternative to doxycycline in select conditions, given doxycycline's continued shortage. We identified 19 studies, 10 of which were published before 2000. Thirteen of the studies were prospective, but only 1 of these studies was randomized. Based on the available data, we found minocycline to be a reasonable substitute for doxycycline in the following scenarios: skin and soft-tissue infections and outpatient treatment of community-acquired pneumonia in young, otherwise healthy patients or in patients with macrolide-resistant Mycoplasma pneumoniae, as well as Lyme disease prophylaxis and select rickettsial disease should doxycycline be unavailable.

Undifferentiated febrile illness in Kathmandu, Nepal

Undifferentiated febrile illnesses (UFIs) are common in low- and middle-income countries. We prospectively investigated the causes of UFIs in 627 patients presenting to a tertiary referral hospital in Kathmandu, Nepal. Patients with microbiologically confirmed enteric fever (218 of 627; 34.8%) randomized to gatifloxacin or ofloxacin treatment were previously reported. We randomly selected 125 of 627 (20%) of these UFI patients, consisting of 96 of 409 (23%) cases with sterile blood cultures and 29 of 218 (13%) cases with enteric fever, for additional diagnostic investigations. We found serological evidence of acute murine typhus in 21 of 125 (17%) patients, with 12 of 21 (57%) patients polymerase chain reaction (PCR)-positive for Rickettsia typhi. Three UFI cases were quantitative PCR-positive for Rickettsia spp., two UFI cases were seropositive for Hantavirus, and one UFI case was seropositive for Q fever. Fever clearance time (FCT) for rickettsial infection was 44.5 hours (interquartile range = 26–66 hours), and there was no difference in FCT between ofloxacin or gatifloxacin. Murine typhus represents an important cause of predominantly urban UFIs in Nepal, and fluoroquinolones seem to be an effective empirical treatment.

Clinical presentation, convalescence, and relapse of rocky mountain spotted fever in dogs experimentally infected via tick bite

Rocky Mountain spotted fever (RMSF) is a tick-borne disease caused by R. rickettsii in North and South America. Domestic dogs are susceptible to infection and canine RMSF can be fatal without appropriate treatment. Although clinical signs of R. rickettsii infection in dogs have been described, published reports usually include descriptions of either advanced clinical cases or experimental infections caused by needle-inoculation of cultured pathogen rather than by tick bite. The natural progression of a tick-borne R. rickettsii infection has not been studied in sufficient detail. Here, we provide a detailed description of clinical, hematological, molecular, and serological dynamics of RMSF in domestic dogs from the day of experimental exposure to infected ticks through recovery. Presented data indicate that neither the height/duration of fever nor detection of rickettsial DNA in dogs' blood by PCR are good indicators for clinical prognosis. Only the apex and subsequent subsidence of neutrophilia seem to mark the beginning of recovery and allow predicting a favorable outcome in Rickettsia-infected dogs, even despite the continuing persistence of mucosal petechiae and skin rash. On the other hand the appropriate (doxycycline) antibiotic therapy of sufficient duration is crucial in prevention of RMSF relapses in dogs.

[Papulovesicular exanthem after a safari in South Africa]

A 68-year-old man presented with a papulovesicular exanthem, fever and malaise after a safari in South Africa. Based on the history, the typical clinical picture with an exanthema and eschar as well as the detection of antibodies against rickettsioses of the spotted fever group, we diagnosed African tick-bite fever which is due to R. africae. During treatment with doxycycline 200 mg/d, all symptoms resolved completely within 11 days. Rickettsioses should always be considered in patients presenting with exanthema, fever and malaise. Particularly the presence of one or multiple eschars on the skin manifesting as erythematous plaques with central necrosis is a pathognomic sign. The serological detection of antibodies against rickettsia species of the spotted fever group is the established diagnostic standard. Due to extensive cross-reactions it is not possible to distinguish between the members of one rickettsial group. Furthermore antibody titers rise late in the disease, frequently 2 or 3 weeks after the onset of symptoms. This underscores the importance of the clinical diagnosis.

Scrub typhus meningitis or meningoencephalitis

Orientia tsutsugamushi induces vasculitis leading to symptoms of systemic organ invasion including meningitis and meningoencephalitis. We conducted a retrospective case-control study of scrub typhus patients to investigate the clinical and laboratory features of patients with scrub typhus meningitis or meningoencephalitis, and the therapeutic outcomes, and to determine the predictor factors. Cases were 22 patients with scrub typhus meningitis or meningoencephalitis, and controls were 303 patients without meningitis or meningoencephalitis. Multivariate analysis showed that the presence of pneumonitis was associated with the occurrence of scrub typhus meningitis and meningoencephalitis (odds ratio [OR] 8.9; P < 0.001; confidence interval [CI] 2.9-27.2). Although appropriate antimicrobials such as doxycycline agents were administered at an early stage, meningitis or meningoencephalitis still occurred in some cases. Physicians should be aware that meningitis or meningoencephalitis may develop during appropriate drug therapy such as doxycycline. Close observation and great care are essential for patients with risk factors, particularly pneumonitis.

Nuclear magnetic resonance applied to antimicrobial drug susceptibility

There are many conventional microbiological methods in routine clinical practice to determine the sensitivity of common bacteria. The problem with these methods arises with bacteria that do not grow on habitual media (Rickettsia spp., Coxiella spp. and Anaplasma spp., among others) and for which there are no standardized techniques to determine their antimicrobial susceptibility. In addition, the techniques that are used for the culture of these fastidious bacteria show problems in both accuracy and reproducibility and, in some cases, the in vitro antimicrobial susceptibility of bacteria shows poor correlation with therapeutic outcome. Therefore, it becomes difficult to determine the antimicrobial drug susceptibility of some bacteria and, thus, to assess the therapeutic effect of drugs. The scientific breakthroughs that have taken place in recent years have allowed the use of new techniques that facilitate and improve microbiological study. This paper reviews the use of nuclear magnetic resonance spectroscopy as an alternative tool for determining antimicrobial drug susceptibility.

Murine typhus in southern Taiwan during 1992-2009

Clinical information regarding murine typhus in Taiwan is limited. In this study, 81 cases of serologically documented murine typhus during 1992-2009 at four referral hospitals in southern Taiwan were analyzed. There was a significant correlation between average environmental temperature and case numbers of murine typhus (r = 0.747, P = 0.005). Acute hepatitis was found in 67% of cases, and hyperbilirubinemia (serum total bilirubin ≥ 23.9 μmol/L) was found in 38%. The intervals between the initiation of appropriate therapy to defervescence were longer in patients with hyperbilirubinemia than those without hyperbilirubinemia (6.1 versus 4.1 days; P = 0.015). Nine (11.1%) showed development of severe illnesses such as acute respiratory distress syndrome (2 patients), aseptic meningitis (3), and acute renal failure (4). Only one died of acute respiratory distress syndrome. Cases of murine typhus were often found during the summer and had acute febrile hepatitis. Those patients with hyperbilirubinemia tended to have a delayed recovery even with appropriate therapy.

Comparison of real-time quantitative PCR and culture for the diagnosis of emerging Rickettsioses

Background

Isolation of Rickettsia species from skin biopsies may be replaced by PCR. We evaluated culture sensitivity compared to PCR based on sampling delay and previous antibiotic treatment.

Methodology/Principal Findings

Skin biopsies and ticks from patients with suspected Rickettsia infection were screened for Rickettsia spp. using qPCR, and positive results were amplified and sequenced for the gltA and ompA genes. Immunofluorescence for spotted fever group rickettsial antigens was done for 79 patients. All skin biopsies and only ticks that tested positive using qPCR were cultured in human embryonic lung (HEL) fibroblasts using the centrifugation-shell vial technique. Patients and ticks were classified as definitely having rickettsioses if there was direct evidence of infection with a Rickettsia sp. using culture or molecular assays or in patients if serology was positive. Data on previous antibiotic treatments were obtained for patients with rickettsiosis. Rickettsia spp. infection was diagnosed in 47 out of 145 patients (32%), 41 by PCR and 12 by culture, whereas 3 isolates were obtained from PCR negative biopsies. For 3 of the patients serology was positive although PCR and culture were negative. Rickettsia africae was the most common detected species (n = 25, [17.2%]) and isolated bacterium (n = 5, [3.4%]). The probability of isolating Rickettsia spp. was 12 times higher in untreated patients and 5.4 times higher in patients from our hometown. Rickettsia spp. was amplified in 24 out of 95 ticks (25%) and we isolated 7 R. slovaca and 1 R. raoultii from Dermacentor marginatus.

Conclusions/Significance

We found a positive correlation between the bacteria copies and the isolation success in skin biopsies and ticks. Culture remains critical for strain analysis but is less sensitive than serology and PCR for the diagnosis of a Rickettsia infection.

Diagnosis of Rickettsia infection would benefit by use of the more rapid and sensitive method of quantitative real-time PCR than the time-intensive and less sensitive method of culturing Rickettsia species from skin biopsies. We evaluated culture sensitivity compared to PCR according to sampling delay and previous antibiotic treatment. We found that skin biopsies can be positive even when molecular tests were negative, and a negative result using molecular assays did not exclude the diagnosis of Rickettsia spp. infection. Rickettsia africae was the most common species in skin biopsies and R. slovaca was most common in ticks. We found a positive correlation between the number of bacteria copies and the isolation success in skin biopsies and ticks. The probability of isolating Rickettsia spp. was higher in untreated patients and in patients from our hometown. To increase the sensitivity of culture, skin biopsies should be sampled before treatment early in the course of the disease and should be inoculated as soon as possible.

Intraocular inflammation as the main manifestation of Rickettsia conorii infection

Objective

To report the clinical features and management of seven cases of intraocular inflammation caused by Rickettsia infection and review published literature.

Methods

Rickettsia conorii or Rickettsia spp. infection was diagnosed based on the following criteria: (1) positive serology according to the European Guidelines, (2) titer normalization after specific treatment, and (3) complete resolution of ophthalmic disease and accompanying symptoms after antibiotic therapy.

Results

Seven patients were referred for uveitis of unknown etiology. All came from regions where Mediterranean spotted fever is prevalent. One patient met the European guidelines criteria for Rickettsia spp. infection, while the other six cases met the criteria for R. conorii infection. The main symptoms were visual loss, floaters, eye redness, photophobia, and ocular pain. Predominant ophthalmic signs included vasculitis, choroiditis, vitritis, and macular edema. All patients required antibiotic treatment that resulted in the remission of the infection. Doxycycline was the first choice and the only antibiotic used to treat four patients. One patient needed ciprofloxacin as a second antibiotic after not responding to doxycycline. Two patients had doxycycline as a second antibiotic after not responding primarily to sulfonamides (which had been given after 2–3 days of doxycycline gastric intolerance); one of these patients needed ciprofloxacin as a third antibiotic.

Conclusion

Intraocular inflammation can occur as the main manifestation of Rickettsia conorii or Rickettsia spp. infection. It should be considered as a differential diagnosis for uveitis especially for patients living in countries where this infection is endemic in the world. Antibiotic treatment remains effective in the management of Rickettsia infection.

Scrub typhus meningoencephalitis occurring during doxycycline therapy for Orientia tsutsugamushi

We report on a scrub typhus patient who contracted meningoencephalitis during doxycycline administration. This is the first case of scrub typhus in which doxycycline concentrations were measured in serum and cerebrospinal fluid. Clinicians should be alerted to the possibility that meningoencephalitis can occur because of inadequate maintenance of serum doxycycline level caused by antacids administered along with doxycycline.

Detection of Rickettsia conorii strains in Portuguese dogs (Canis familiaris)

This study reports a serological and molecular survey on the spotted fever group Rickettsia found in a group of 51 dogs with suspected tick-borne illness from the south of Portugal. Additionally, a prevalence of IgG antibodies to R. conorii was also estimated in a group of 400 healthy dogs from the same region. In the group of healthy dogs, the immunofluorescence test revealed that 154 (38.5%) of the 400 dogs had IgG antibodies reactive with R. conorii. The highest proportion of dogs (45%) with R. conorii antibodies was found in blood samples collected from October to December. Among the group suspected with tick-borne illness, 35 (62%) dogs showed to be seroreactive (IgG≥128) for antibodies against R. conorii, and the analysis of PCR-positive amplicons revealed that 5 dogs were infected with R. conorii Malish and 2 dogs were infected with R. conorii Israeli tick typhus strain. There was a higher prevalence of antibodies to R. conorii in the group of sick dogs, and the detection of R. conorii DNA in blood samples from this group points to their potential role as a reservoir and sentinel host helping to evaluate and characterize the distribution of circulating rickettsial strains.

Intravenous minocycline versus oral doxycycline for the treatment of noncomplicated scrub typhus

BACKGROUND

Scrub typhus is an acute febrile disease for which synthetic tetracycline antibiotics are efficacious. However, no clinical studies have compared oral doxycycline with intravenous minocycline for treatment of scrub typhus.

METHODS

We conducted a retrospective analysis in patients diagnosed with noncomplicated scrub typhus by serologic or molecular methods from August 2001 to July 2007. We compared the efficacy of intravenous minocycline with oral doxycycline for treatment of noncomplicated scrub typhus in these patients.

RESULTS

Forty seven cases receiving tetracycline antibiotics for the treatment of noncomplicated scrub typhus were included. There was no statistically significant difference for the response rate between the 25 cases receiving intravenous minocycline (96%) and the 22 cases receiving oral doxycycline (91%) (p=0.909). Kaplan-Meier curve with a long-rank test for the time to defervescence showed no statistically significant difference between minocycline therapy (mean 30 hours; range 4-124 hours) and doxycycline therapy (mean 32.4 hours; range 4-144 hours) (p=0.860). After multivariate Cox regression models, the time to defervescence was only affected by Acute Physiology and Chronic Health Evaluation II score (hazard ratio 0.868; p=0.016). Nearly all patients (93.6%) became afebrile within 72 hours after use of tetracycline antibiotics. Prolonged hospitalization (> 7 days) was correlated with the timing to start tetracycline antibiotics after admission.

CONCLUSION

Both antibiotics have similar efficacy for the treatment of noncomplicated scrub typhus. Nearly all cases responding to both antibiotics became afebrile within 3 days.

Wolbachia modulates Chikungunya replication in Aedes albopictus

The Aedes albopictus mosquito has been involved as the principal vector of recent major outbreaks due to the chikungunya virus (CHIKV). The species is naturally infected by two strains of Wolbachia (wAlbA and wAlbB). Wolbachia infections are thought to have spread by manipulating the reproduction of their hosts; cytoplasmic incompatibility is the mechanism used by Wolbachia to invade natural populations of many insects including Ae. albopictus. Here, we report a study on the effects of removing Wolbachia from Ae. albopictus on CHIKV replication and examine the consequences of CHIKV infection on some life-history traits (survival and reproduction) of Wolbachia-free Ae. albopictus. We found that Wolbachia-free mosquitoes maintained a highly heterogeneous CHIKV replication compared to Wolbachia-infected individuals. In Wolbachia-infected Ae. albopictus, the regular increase of CHIKV followed by a steady viral load from day 4 post-infection onwards was concomitant with a decline in Wolbachia density. This profile was also detected when examining the two key organs for viral transmission, the midgut and the salivary glands. Moreover, Wolbachia-free Ae. albopictus was not altered in life-history traits such as survival, oviposition and hatching characteristics whether infected or not with CHIKV. We found that Wolbachia is not essential for viral replication, its presence could lead to optimize replication from day 4 post-infection onwards, coinciding with a decrease in Wolbachia density. Wolbachia may regulate viral replication in Ae. albopictus, with consequences on survival and reproduction.

Diagnosis and treatment of tick infestation and tick-borne diseases with cutaneous manifestations

Hard and soft ticks may be associated directly or indirectly with a number of dermatoses, both infectious and inflammatory in origin. Morbidity may occur as a result of tick bites, tick toxicosis, and even infestation. These arthropod vectors may transmit life-threatening protozoan, bacterial, rickettsial, and viral diseases with systemic and cutaneous findings. Additionally, ticks may transmit more than one pathogen with subsequent human coinfection. This article reviews the presentation of tick-borne illnesses and the medical management of these diseases. Among others, diseases such as ehrlichiosis, anaplasmosis, babesiosis, tularemia, borrelioses, tick-borne encephalitides, rickettsial spotted fevers, and tick typhus are discussed in this article. The recognition of skin manifestations associated with these diseases is paramount to early diagnosis and treatment initiation.

Pristinamycin for Rickettsia africae infection

African tick bite fever is caused by Rickettsia africae. The number of reported cases in international travelers has significantly increased recently. The gold standard treatment is doxycycline. Here, we present a case of R africae infection associated with quick complete resolution following the initiation of pristinamycin therapy.

Rickettsial infections around the world, part 1: pathophysiology and the spotted fever group

BACKGROUND

The rickettsial diseases are an important group of infectious agents that have dermatological manifestations. These diseases are important to consider in endemic areas, but in certain suspicious cases, possible acts of bioterrorism should warrant prompt notification of the appropriate authorities.

OBJECTIVE

In this two part review article, we review these diverse diseases by examining established and up-to-date information about the pathophysiology, epidemiology, clinical manifestations, and treatment of the ricksettsiae.

METHODS

Using PubMed to search for relevant articles, we browsed over 500 articles to compose a clinically based review article.

RESULTS

Part one focuses on pathophysiology of the rickettsial diseases and the clinical aspects of the spotted fever group.

CONCLUSIONS

At the completion of part one of this learning activity, participants should be able to discuss all of the clinical manifestations and treatments of the sported fever group. Participants should also be familiar with the pathophysiology of the rickettsial diseases.

Analysis of fluorescent protein expression in transformants of Rickettsia monacensis, an obligate intracellular tick symbiont

We developed and applied transposon-based transformation vectors for molecular manipulation and analysis of spotted fever group rickettsiae, which are obligate intracellular bacteria that infect ticks and, in some cases, mammals. Using the Epicentre EZ::TN transposon system, we designed transposons for simultaneous expression of a reporter gene and a chloramphenicol acetyltransferase (CAT) resistance marker. Transposomes (transposon-transposase complexes) were electroporated into Rickettsia monacensis, a rickettsial symbiont isolated from the tick Ixodes ricinus. Each transposon contained an expression cassette consisting of the rickettsial ompA promoter and a green fluorescent protein (GFP) reporter gene (GFPuv) or the ompB promoter and a red fluorescent protein reporter gene (DsRed2), followed by the ompA transcription terminator and a second ompA promoter CAT gene cassette. Selection with chloramphenicol gave rise to rickettsial populations with chromosomally integrated single-copy transposons as determined by PCR, Southern blotting, and sequence analysis. Reverse transcription-PCR and Northern blots demonstrated transcription of all three genes. GFPuv transformant rickettsiae exhibited strong fluorescence in individual cells, but DsRed2 transformants did not. Western blots confirmed expression of GFPuv in R. monacensis and in Escherichia coli, but DsRed2 was expressed only in E. coli. The DsRed2 gene, but not the GFPuv gene, contains many GC-rich amino acid codons that are rare in the preferred codon suite of rickettsiae, possibly explaining the failure to express DsRed2 protein in R. monacensis. We demonstrated that our vectors provide a means to study rickettsia-host cell interactions by visualizing GFPuv-fluorescent R. monacensis associated with actin tails in tick host cells.