Deleterious effect of trimethoprim-sulfamethoxazole in Mediterranean spotted fever

Murine Typhus: A Review of a Reemerging Flea-Borne Rickettsiosis with Potential for Neurologic Manifestations and Sequalae

Murine typhus is an acute febrile illness caused by Rickettsia typhi, an obligately intracellular Gram-negative coccobacillus. Rats (Rattus species) and their fleas (Xenopsylla cheopis) serve as the reservoir and vector of R. typhi, respectively. Humans become infected when R. typhi-infected flea feces are rubbed into flea bite wounds or onto mucous membranes. The disease is endemic throughout much of the world, especially in tropical and subtropical seaboard regions where rats are common. Murine typhus is reemerging as an important cause of febrile illness in Texas and Southern California, where an alternate transmission cycle likely involves opossums (Didelphis virginiana) and cat fleas (Ctenocephalides felis). Although primarily an undifferentiated febrile illness, a range of neurologic manifestations may occur, especially when treatment is delayed. Serology is the mainstay of diagnostic testing, but confirmation usually requires demonstrating seroconversion or a fourfold increase in antibody titer from acute- and convalescent-phase sera (antibodies are seldom detectable in the first week of illness). Thus, early empiric treatment with doxycycline, the drug of choice, is imperative. The purpose of this review is to highlight murine typhus as an important emerging and reemerging infectious disease, review its neurologic manifestations, and discuss areas in need of further study.

Manifestations and Management of Flea-Borne Rickettsioses

Murine typhus and flea-borne spotted fever are undifferentiated febrile illnesses caused by Rickettsia typhi and Rickettsia felis, respectively. These organisms are small obligately intracellular bacteria and are transmitted to humans by fleas. Murine typhus is endemic to coastal areas of the tropics and subtropics (especially port cities), where rats are the primary mammalian host and rat fleas (Xenopsylla cheopis) are the vector. In the United States, a cycle of transmission involving opossums and cat fleas (Ctenocephalides felis) are the presumed reservoir and vector, respectively. The incidence and distribution of murine typhus appear to be increasing in endemic areas of the US. Rickettsia felis has also been reported throughout the world and is found within the ubiquitous cat flea. Flea-borne rickettsioses manifest as an undifferentiated febrile illness. Headache, malaise, and myalgia are frequent symptoms that accompany fever. The incidence of rash is variable, so its absence should not dissuade the clinician to consider a rickettsial illness as part of the differential diagnosis. When present, the rash is usually macular or papular. Although not a feature of murine typhus, eschar has been found in 12% of those with flea-borne spotted fever. Confirmatory laboratory diagnosis is usually obtained by serology; the indirect immunofluorescence assay is the serologic test of choice. Antibodies are seldom present during the first few days of illness. Thus, the diagnosis requires acute- and convalescent-phase specimens to document seroconversion or a four-fold increase in antibody titer. Since laboratory diagnosis is usually retrospective, when a flea-borne rickettsiosis is considered, empiric treatment should be initiated. The treatment of choice for both children and adults is doxycycline, which results in a swift and effective response. The following review is aimed to summarize the key clinical, epidemiological, ecological, diagnostic, and treatment aspects of flea-borne rickettsioses.

Assessment of Risk Factors and Outcomes of Severe Ehrlichiosis Infection

IMPORTANCE

Ehrlichiosis cases in the US have increased more than 8-fold since 2000. Up to 57% of patients with ehrlichiosis require hospitalization and 11% develop a life-threatening complication; however, risk factors for serious disease are not well documented.

OBJECTIVE

To examine risk factors associated with severe ehrlichiosis.

DESIGN, SETTING, AND PARTICIPANTS

An analytic cross-sectional study of patients diagnosed with ehrlichiosis by polymerase chain reaction (PCR) between January 1, 2007, and December 31, 2017, was conducted in a single tertiary-care center in a region endemic for ehrlichiosis. Analysis was performed from February 27, 2018, to September 9, 2020. A total of 407 positive Ehrlichia PCR results were identified from 383 unique patients, with 155 unique patients meeting study criteria. Patients hospitalized at other institutions who had a positive Ehrlichia PCR performed as a reference test (n = 222) were excluded as no clinical data were available. Electronic medical record review was performed to collect demographic, clinical, laboratory, treatment, and outcomes data. Cases were excluded when there were insufficient clinical data to assess the severity of illness (n = 3) and when the clinical illness did not meet the case definition for ehrlichiosis (n = 3).

EXPOSURES

Date of presentation, onset of symptoms, date of PCR testing, date of treatment initiation, site of care, age, birth sex, race/ethnicity, Charlson Comorbidity Index, trimethoprim with sulfamethoxazole use within the prior 2 weeks, and immunosuppression.

MAIN OUTCOMES AND MEASURES

Requirement for intensive care unit (ICU) admission.

RESULTS

Of the 155 patients who met inclusion criteria, 99 patients (63.9%) were men, and 145 patients (93.5%) identified as non-Hispanic White; median age was 50 years (interquartile range, 23-64 years). Intensive care unit admission was indicated in 43 patients (27.7%), 94 patients (60.6%) were hospitalized on general medical floors, and 18 patients (11.6%) received care as outpatients. In adjusted analysis, time to treatment initiation was independently associated with an increased risk for ICU admission (adjusted prevalence ratio [aPR], 1.09; 95% CI, 1.04-1.14; P < .001). Documentation of tick exposure was independently associated with a decreased risk for ICU admission (aPR, 0.54; 95% CI, 0.34-0.86; P = .01). There appeared to be a nonsignificant change toward a decreased need for ICU care among immunosuppressed persons (aPR, 0.51; 95% CI, 0.26-1.00; P = .05).

CONCLUSIONS AND RELEVANCE

This study suggests that delay in initiation of doxycycline therapy is a significant factor associated with severe ehrlichiosis. Increased recognition of infection by front-line clinicians to promote early treatment may improve outcomes associated with this increasingly common and life-threatening infection.

Epidemiology, Clinical Aspects, Laboratory Diagnosis and Treatment of Rickettsial Diseases in the Mediterranean Area During COVID-19 Pandemic: A Review of the Literature

The purpose of the present review is to give an update regarding the classification, epidemiology, clinical manifestation, diagnoses, and treatment of the Rickettsial diseases present in the Mediterranean area.

We performed a comprehensive search, through electronic databases (Pubmed – MEDLINE) and search engines (Google Scholar), of peer-reviewed publications (articles, reviews, and books).

The availability of new diagnostic tools, including Polymerase Chain Reaction and nucleotide sequencing has significantly modified the classification of intracellular bacteria, including the order Rickettsiales with more and more new Rickettsia species recognized as human pathogens. Furthermore, emerging Rickettsia species have been found in several countries and are often associated with unique clinical pictures that may challenge the physician in the early detection of the diseases.

Rickettsial infections include a wide spectrum of clinical presentations ranging from a benign to a potentially life treating disease that requires prompt recognition and proper management. Recently, due to the spread of SARS-CoV-2 infection, the differential diagnosis with COVID-19 is of crucial importance. The correct understanding of the clinical features, diagnostic tools, and proper treatment can assist clinicians in the management of Rickettsioses in the Mediterranean area.

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.

Treatment of Rickettsia spp. infections: a review

Human rickettsioses caused by intracellular bacteria of the genus Rickettsia are distributed worldwide and are transmitted by arthropod vectors such as ticks, fleas, mites and lice. They have a wide range of manifestations from benign to life-threatening diseases. Mortality rates of up to 30% have been reported for some rickettsioses. Here, the authors will review in vitro and human studies of the various compounds that have been used for the treatment of Rickettsia spp. infections. The authors will also provide recommendations for the treatment of spotted fever and typhus group rickettsioses.

Host, pathogen and treatment-related prognostic factors in rickettsioses

Diseases caused by rickettsiae, which are vector-borne bacteria, vary widely from mild and self-limiting, to severe and life-threatening. Factors influencing this diversity of outcome are related to the host, to the infectious agent and to the treatment used to treat the infection. A literature search was conducted on PubMed using the phrases "factors-related severity, outcome, host, pathogen, Rickettsia conorii, R. rickettsii, R. africae, R. felis, R. prowazekii, R. typhi, genomics". Among host factors, old age and the male gender have been associated with poor outcome in rickettsioses. Co-morbidities, ethnical factors and the genetic background of the host also seem to influence the outcome of rickettsial diseases. Moreover, although the degree of the host response is beneficial, it could also partly explain the severity observed in some patients. Among pathogen-related factors, traditional concepts of factors of virulence had been challenged and genomic reductive evolution with loss of regulatory genes is the main hypothesis to explain virulence observed in some species, such as Rickettsia prowazekii, the agent of epidemic typhus. R. prowazekii is the more pathogenic rickettsiae and harbours the smaller genome size (1.1 Mb) compared to less or non-virulent species, and is not intracellularly motile, a factor considered as a virulence factor for other intracellular bacteria. The antibiotic regimen used to treat rickettsioses also has an influence on prognosis. Usual concepts of severity and virulence in rickettsioses are challenging and are frequently paradoxical. In this mini-review, we will describe factors currently thought to influence the outcome of the main rickettsioses responsible for illness in humans.

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.

Antimicrobial prevention and therapy for travelers' infection

International journeys are increasing and more than 70 million people from industrialized countries cross the borders of tropical countries every year. More than 50% of them will suffer from some form of infectious illness, ranging from mild travelers' diarrhea to severe dengue fever to fatal malaria, with a wide spectrum of microbiological entities. Travel-related respiratory infections, including TB, and sexually transmitted infections are also increasingly reported. Awareness of travel-related risk is not always adequate among international travelers. Specific training on travel medicine-related issues, as well as better diagnostic facilities for imported diseases, is crucial for physicians and nurses in industrialized countries.

Spotted fever rickettsioses in southern and eastern Europe

Mediterranean spotted fever due to Rickettsia conorii conorii was thought, for many years, to be the only tick-borne rickettsial disease prevalent in southern and eastern Europe. However, in recent years, six more species or subspecies within the spotted fever group of the genus Rickettsia have been described as emerging pathogens in this part of the world. Tick-borne agents include Rickettsia conorii israelensis, Rickettsia conorii caspia, Rickettsia aeschlimannii, Rickettsia slovaca, Rickettsia sibirica mongolitimonae and Rickettsia massiliae. Many Rickettsia of unknown pathogenicity have also been detected from ticks and could represent potential emerging pathogens to be discovered in the future. Furthermore, a new spotted fever rickettsia, Rickettsia felis, was found to be associated with cat fleas and is an emerging human pathogen. Finally, the mite-transmitted Rickettsia akari, the agent of rickettsialpox, is also known to be prevalent in Europe. We present here an overview of these rickettsioses, focusing on emerging diseases.

Human monocytic ehrlichiosis in children

BACKGROUND

Human monocytic ehrlichiosis (HME) is a tick-borne illness caused by Ehrlichia chaffeensis. Data about disease in children have been largely derived from case reports or small case series.

METHODS

A retrospective review of all medical and laboratory records from 6 sites located in the "tick belt" of the Southeastern United States was carried out. Demographic, history and laboratory data were abstracted from the identified medical records of patients. Bivariate statistical comparisons were performed using Fisher exact test or Wilcoxon rank sum tests.

RESULTS

Common clinical signs and symptoms of patients with HME (n = 32) included fever (100%), headache (69%), myalgia (69%), rash (66%), nausea/vomiting (56%), altered mental status (50%) and lymphadenopathy (47%). Only 48% had a complaint of fever, headache and rash. Common laboratory abnormalities included thrombocytopenia (94%), elevated aspartate aminotransferase (90%), elevated alanine aminotransferase (74%), hypoalbuminemia (65%), lymphopenia (57%), leukopenia (56%) and hyponatremia (55%). The median number of days of illness before the initiation of antirickettsial therapy was 6. Patients who received sulfonamides before starting doxycycline therapy developed a rash, were admitted to the hospital, and started doxycycline at a later date. Twenty-two percent of patients were admitted to the intensive care unit with 12.5% of patients requiring ventilatory and blood pressure support.

CONCLUSIONS

Although HME has been recognized among children for almost 20 years, there is only a limited knowledge about its clinical course. Even among physicians practicing in endemic regions, few cases are diagnosed each year. More work is needed to understand the true burden of disease and the natural history among asymptomatically and symptomatically infected children.

Genome Comparison Analysis of Molecular Mechanisms of Resistance to Antibiotics in the Rickettsia Genus

In this study we describe molecular mechanisms of resistance to several classes of antibiotics within drug targets by in silico genome comparisons for bacteria of the genus Rickettsia. Apart from the mutations in the rpoB gene in naturally rifampin-resistant Rickettsia species previously reported by our team, we found that typhus group (TG) rickettsiae had a triple amino acid difference in the highly conserved region of the L22 ribosomal protein as compared to the spotted fever group rickettsiae (SFG), which could explain the natural resistance of SFG rickettsia to erythromycin. We found also that the genome of R. conorii contains an aminoglycoside 3'-phosphotransferase. Finally, either folA gene (encoding dihydrofolate reductase) and/or folP gene (encoding dihydropteroate synthase) was missing in the genome of rickettsial strains explaining the natural resistance to cotrimoxazole. Finally, multiple genes encoding for pump efflux were found especially in the genome of R. conorii that could be involved in resistance to antibiotics. Five specific ORFs related to antibiotic resistance have been identified in the genome of R. felis including a streptomycin resistance protein homologue, a class C beta-lactamase, a class D beta-lactamase, a penicillin acylase homologue, and an ABC-type multidrug transporter system. For the first time, using this approach, an experimental beta-lactamase activity has been shown for this bacterium. We believe that whole genome sequence analysis may help to predict several phenotypic characters, in particular resistance to antibiotics for obligate intracellular bacteria.

Tick-borne infections in children: epidemiology, clinical manifestations, and optimal management strategies

Ticks can transmit bacterial, protozoal, and viral infections to humans. Specific therapy is available for several of these infections. Doxycycline is the antimicrobial treatment of choice for all patients, regardless of age, with Rocky Mountain spotted fever, human monocytic ehrlichiosis, or human granulocytic ehrlichiosis. Chloramphenicol has been used to treat these infections in children but is demonstrably inferior to doxycycline. In patients with Mediterranean spotted fever, doxycycline, chloramphenicol, and newer macrolides all appear to be effective therapies. Therapy of Lyme disease depends on the age of the child and stage of the disease. For early localized disease, amoxicillin (for those aged <8 years) or doxycycline (for those aged >/=8 years) is effective. Doxycycline, penicillin V (phenoxymethylpenicillin) or penicillin G (benzylpenicillin) preparations, and erythromycin are all effective treatments for tick-borne relapsing fever. Hospitalized patients with tularemia should receive gentamicin or streptomycin. Doxycycline and ciprofloxacin have each been investigated for the treatment of tularemia in outpatients; however, these agents do not yet have established roles in the treatment of this disease in children. Combination therapy with clindamycin and quinine is preferred for children with babesiosis; the combination of azithromycin and atovaquone also appears promising. Ribavirin has been recently shown to markedly improve survival in patients with Crimean-Congo hemorrhagic fever. The role of antiviral therapy in the treatment of other tick-borne viral infections, including other hemorrhagic fevers and tick-borne encephalitis, is not yet defined.

Tick-borne rickettsioses around the world: emerging diseases challenging old concepts

During most of the 20th century, the epidemiology of tick-borne rickettsioses could be summarized as the occurrence of a single pathogenic rickettsia on each continent. An element of this paradigm suggested that the many other characterized and noncharacterized rickettsiae isolated from ticks were not pathogenic to humans. In this context, it was considered that relatively few tick-borne rickettsiae caused human disease. This concept was modified extensively from 1984 through 2005 by the identification of at least 11 additional rickettsial species or subspecies that cause tick-borne rickettsioses around the world. Of these agents, seven were initially isolated from ticks, often years or decades before a definitive association with human disease was established. We present here the tick-borne rickettsioses described through 2005 and focus on the epidemiological circumstances that have played a role in the emergence of the newly recognized diseases.

Fatal spotted fever rickettsiosis, Kenya

We report a fatal case of rickettsiosis in a woman from the United States living in Kenya, who had a history of tick exposure. Immunohistochemical staining of skin, kidney, and liver demonstrated spotted fever group rickettsiae. The clinical findings, severity, and fatal outcome are most consistent with Rickettsia conorii infection.

Acute spotted fever rickettsiosis among febrile patients, Cameroon

Although potential arthropod vectors are abundant in Cameroon, acute febrile illnesses are rarely evaluated for arboviral or rickettsial infections. Serum samples from 234 acutely febrile patients at clinics in Tiko and Buea, Cameroon, were examined for antibodies to Rickettsia africae and African alphaviruses and flaviviruses. These serum samples did not contain antibodies against typhoid, and blood malarial parasites were not detected. Serum samples of 32% contained immunoglobulin M antibodies reactive with R. africae by immunofluorescence assay and were reactive with outer membrane proteins A and B of R. africae by immunoblotting. These findings established a diagnosis of acute rickettsiosis, most likely African tick-bite fever. Hemagglutination inhibition testing of the serum samples also detected antibodies to Chikungunya virus (47%) and flaviviruses (47%). High prevalence of antibodies to arboviruses may represent a major, previously unrecognized public health problem in an area where endemic malaria and typhoid fever have been the principal diagnostic considerations.

Acute spotted fever rickettsiosis among febrile patients, Cameroon

Although potential arthropod vectors are abundant in Cameroon, acute febrile illnesses are rarely evaluated for arboviral or rickettsial infections. Serum samples from 234 acutely febrile patients at clinics in Tiko and Buea, Cameroon, were examined for antibodies to Rickettsia africae and African alphaviruses and flaviviruses. These serum samples did not contain antibodies against typhoid, and blood malarial parasites were not detected. Serum samples of 32% contained immunoglobulin M antibodies reactive with R. africae by immunofluorescence assay and were reactive with outer membrane proteins A and B of R. africae by immunoblotting. These findings established a diagnosis of acute rickettsiosis, most likely African tick-bite fever. Hemagglutination inhibition testing of the serum samples also detected antibodies to Chikungunya virus (47%) and flaviviruses (47%). High prevalence of antibodies to arboviruses may represent a major, previously unrecognized public health problem in an area where endemic malaria and typhoid fever have been the principal diagnostic considerations.

Mediterranean spotted fever in Portugal: risk factors for fatal outcome in 105 hospitalized patients

Mediterranean spotted fever (MSF) is the most important tick-borne disease in Portugal. It is a notifiable disease and during 1989-2000 the annual incidence rate in Portugal was 9.8/10(5) inhabitants. Although recognized as a benign acute disease and treated mainly with ambulatory procedures, some cases are severe and fatalities have increased in the last few years. In 1997, MSF mortality became more evident in Beja, a Portuguese southern district, with a case fatality rate of 32.3% in hospitalized patients. Analysis of 55 variables regarding epidemiologic, clinical, laboratory, and therapeutic data of fatal and nonfatal MSF cases were compared to identify risk factors in 105 patients hospitalized in Beja District Hospital, between 1994 and 1998. It was statistically significant that the patients dying in 1997 were younger than those in other years. The risk of dying is statistically significant in those who presented with diabetes, vomiting, dehydration, and uremia. The interval between the onset of symptoms to administration of anti-rickettsial therapy was the same for all patients. Therapy delay, reported by some authors to be associated with mortality of MSF, was not a risk factor in our study. The patients who died in 1997 died faster than those in other years. The variables studied could not explain the higher mortality rates observed in our study. Although one may speculate that the pathogenic strain of Israeli tick typhus, isolated in 1997, could be responsible for this increase of fatality rate, inherited patient factors might also be strongly associated with mortality.

In vitro susceptibilities of 27 rickettsiae to 13 antimicrobials

The MICs of 13 antibiotics (doxycycline, thiamphenicol, rifampin, amoxicillin, gentamicin, co-trimoxazole, ciprofloxacin, pefloxacin, ofloxacin, erythromycin, josamycin, clarithromycin, and pristinamycin) were determined for 27 available rickettsial species or strains. We used two in vitro cell culture methods described previously: the plaque assay and the microplaque colorimetric assay. Our results confirm the susceptibilities of rickettsiae to doxycycline, thiamphenicol, and fluoroquinolones. Beta-lactams, aminoglycosides, and cotrimoxazole were not active. Typhus group rickettsiae were susceptible to all macrolides tested, whereas the spotted fever group rickettsiae, R. bellii, and R. canada were more resistant, with josamycin, a safe alternative for the treatment of Mediterranean spotted fever, being the most effective compound. Strain Bar 29, R. massiliae, R. montana, R. aeschlimannii, and R. rhipicephali, which are members of the same phylogenetic subgroup, were more resistant to rifampin than the other rickettsiae tested. Heterogeneity in susceptibility to rifampin, which we report for the first time, may explain in vivo discrepancies in the effectiveness of this antibiotic for the treatment of rickettsial diseases. We hypothesize that rifampin resistance and erythromycin susceptibility may reflect a divergence during the evolution of rickettsiae.

Mediterranean Spotted Fever in Travelers from the United States

Background: We wish to increase awareness by U.S. physicians of the clinical manifestations and diagnosis of Mediterranean spotted fever (MSF), and to determine the incidence of MSF among travelers returning to the United States from endemic areas. Methods: We report a case of a 56-year-old female physician from New Orleans who returned from a 3-week safari trip to Zimbabwe and Zambia with clinical findings of MSF. The diagnosis was confirmed with a greater than fourfold rise in titer of IgM and IgG antibody to Rickettsia conorii on acute and convalescent sera (16 days apart) using indirect immunofluorescence technique. In addition, we conducted a MEDLINE computer search of published MSF cases in U.S. travelers returning to the United States and obtained the United States data over the past 20 years from the Centers for Disease Control and Prevention (CDC). Results: Less than 50 imported cases of MSF have been reported and confirmed by the CDC. Only seven cases have been published in the literature and none in the last 7 years. Conclusions: Despite the increasing incidence of MSF in Europe, Asia and Africa, and the high number of U.S. citizens traveling to these endemic areas, only a few imported cases of MSF in travelers have been reported in the United States. Physicians in the United States are not familiar with the clinical findings and diagnosis of MSF; therefore this disease is underrecognized in the majority of cases.