Introduction_to_Obligate_Intracellular_Bacteria_2023 (1).pptx

OBLIGATE INTRACELLULAR BACTERIA: RICKETTSIA, EHRLICHIA, ANAPLASMA AND COXIELLA Michael E. Woods, Ph.D. November 1, 2022 LEARNING OBJECTIVES By the end of the session you should be able to:  Discuss the advantages of intracellular growth from a microbial perspective  Name the obligate intracellul...

OBLIGATE INTRACELLULAR BACTERIA: RICKETTSIA, EHRLICHIA, ANAPLASMA AND COXIELLA Michael E. Woods, Ph.D. November 1, 2022 LEARNING OBJECTIVES By the end of the session you should be able to:  Discuss the advantages of intracellular growth from a microbial perspective  Name the obligate intracellular bacteria of clinical significance and the disease associated with each  Describe the epidemiology, clinical aspects of disease, and characteristics of the immune response to Rickettsia, Ehrlichia, Anaplasma, and Coxiella organisms  Characterize the intracellular survival mechanisms used by Rickettsia, Ehrlichia, Anaplasma and Coxiella.  Describe methods of diagnosis for Rickettsia, Ehrlichia, Anaplasma, and Coxiella organisms  Describe the methods of prevention of disease caused by Rickettsia, Ehrlichia, Anaplasma, and Coxiella organisms Required reading Recommended reading  Murray, Rosenthal and Pfaller,  D. Raoult, “Chapter 327: Medical Microbiology, 9th Edition Chapter 34 Rickettsial Infections,” in Goldman-Cecil Medicine, 25th Edition, 2016, pp. 2046–2056 MANY BACTERIA GROW INTRACELLULARLY; FEW REQUIRE IT Obligate intracellular bacteria – absence of ability to multiply in a cell-free environment Facultative intracellular bacteria – capable of multiplying in a cell-free environment  Rickettsia spp.  Listeria monocytogenes  Orientia tsutsugamushi  Salmonella spp.  Ehrlichia spp.  Mycobacteria spp.  Anaplasma spp.  Shigella spp.  Coxiella burnetii  Legionella  Chlamydia spp. OBLIGATE INTRACELLULAR BACTERIA ARE A CASE STUDY IN REDUCTIVE EVOLUTION  The transition from free-living to intracellular life is associated with the loss of large segments of DNA.  Metabolic pathways  Bacterial toxin/antitoxin loci  Mobile genetic elements (reduces gene transfer and therefore genetic diversity)  Must evade host defenses to survive intracellularly  Survive in one of two intracellular compartments  Vesicular (e.g., phagosome)  Non-vesicular (e.g., cytoplasm)  Prevent apoptosis long enough to replicate Coxiella burnetii Anaplasma phagocytophilum Ehrlichia chaffeensis Rickettsia spp. Disease Clinical presentation Q fever Mild-to-severe pneumonia and hepatitis; it may progress to chronic infection Anaplasmosis Asymptomatic-to-severe fever, malaise, leukopenia and increased liver enzymes Ehrlichiosis Mild-to-severe fever, malaise, leukopenia, increased liver enzymes and occasional CNS symptoms Spotted fever and typhus Fever, respiratory and CNS symptoms, and organ failure Distribution Global The Americas, Europe and Asia The Americas and Asia Global Epidemiology Ubiquitous in animals; potential for outbreaks among agricultural workers 2,600 reported cases annually in the United States with increasing incidence but limited global estimates 3 cases per million people annually in the United States; increasing incidence but limited global estimates Historically devastating outbreaks, global estimates limited and new species constantly emerging Transmission Inhalation Tick vector Tick vector Arthropod vector Major mammalian host cell Alveolar macrophage Granulocytes and endothelial cells Monocytes and macrophages Endothelial cells Organs affected • Acute: the lungs Inflammatory lesions in Multiple organs and liver damage Multiple Lacks LPS and Lacks LPS and peptidoglycan; peptidoglycan; antigenic macrophages are minor variation targets of infection; antigenic variation SFG, typhus group, transitional and ancestral groups • Chronic: the heart and liver Notes Highly virulent; lung endothelium and epithelium are minor targets of infection RICKETTSIA Rickettsia SFG Cell-to-cell spread  Small (0.3 × 1.0 μm), gram-negative rods  Minimal peptidoglycan layer TG and SFG  LPS has weak endotoxin activity  Invade cells through receptor-mediated internalization  Escape the phagosome and replicate in the cytoplasm using a Phospholipase to degrade the vacuolar membrane  Spotted Fever group (SFG) rickettsiae polymerize host-cell actin, spread from cell to cell  Typhus group (TG) rickettsiae require cell lysis for spread Spotted fever group R. rickettsii R. conorii R. parkeri R. australis R. africae Typhus group R. prowazekii R. typhi Cell lysis R. rickettsii IS THE ETIOLOGICAL AGENT OF ROCKY MOUNTAIN SPOTTED FEVER (RMSF) Tobia fever (Colombia) São Paulo fever (Brazil) Febre maculosa (Brazil) Fiebre manchada  Despite its namesake, most common in Fiebre maculosa de las Montañas Rocosas North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri (>60%)  Has become increasingly common in Arizona  Occurs throughout North and South America  RMSF is the most severe tick-borne illness in the United States  3% case fatality rate among confirmed cases in the US (2000–2007)  >20% case fatality rate if untreated  Highest case fatality and hospitalization rates in children (<9 years) and adults (>70 years), and cases where treatment was delayed Annual Incidence of RMSF, 2018 https://www.cdc.gov/rmsf/stats/index.html R. RICKETTSII IS TRANSMITTED BY TICKS; OCCURS MOST OFTEN IN THE SUMMER MONTHS Primary vectors of RMSF in North Dermacento Dermacento Rhipicephalus America r variabilis r andersoni sanguineus M.E. Eremeeva and G.A. Dasch, “Challenges posed by tickborne rickettsiae: eco-epidemiology and public health implications,” Frontiers in Public Health, April 2015, Up to 40% of patients do not report a history of tick bite, but a history of travel or outdoor activity can often be ascertained R. RICKETTSII TARGETS ENDOTHELIAL CELLS, CAUSES VASCULITIS  Incubation period is 2–14 days  Sudden onset of fever, myalgia, nausea, headache  Rash occurs in 90% of patients 2–5 days after onset  Begins as maculopapular progressing to petechial rash in severe cases  Centripetal spread is a classic feature of RMSF; begins on wrists, arms and ankles and then spreads to the trunk  Involvement of palms and soles is diagnostically important  Severe complications  Hypotension  Non-cardiogenic pulmonary edema  Confusion  Lethargy  Encephalitis progressing to coma Rickettsia rickettsii (Rocky Mountain Spotted Fever) McQuiston, Jennifer H., Principles and Practice of Pediatric Infectious Diseases, 178, 926929.e2 R. RICKETTSII TARGETS ENDOTHELIAL CELLS, CAUSES VASCULITIS  Incubation period is 2–14 days  Sudden onset of fever, myalgia, nausea, headache  Rash occurs in 90% of patients 2–5 days after onset  Begins as maculopapular progressing to petechial rash in severe cases  Centripetal spread is a classic feature of RMSF; begins on wrists, arms and ankles and then spreads to the trunk  Involvement of palms and soles is diagnostically important  Severe complications  Hypotension  Non-cardiogenic pulmonary edema  Confusion  Lethargy  Encephalitis progressing to coma EARLY RECOGNITION AND INITIATION OF TREATMENT IS CRITICAL FOR A SUCCESSFUL OUTCOME  Empirical treatment is Outcome by day of symptoms that doxycycline was started doxycycline  Chloramphenicol may be an alternative in pregnant women and those that are allergic to doxycycline, but is not as effective Median day of rash onset! https://www.ihs.gov/telebehavioral/includes/themes/ newihstheme/display_objects/documents/slides/ 2015winternational/rockymtsptfvr508.pdf Patient presents with fever (>100ºF) or history of subjective fever AND Resident of RMSF endemic area OR History of travel to endemic area within 2 weeks of onset of symptoms OR Contact with a dog from an endemic area within 2 weeks of onset of symptoms DIAGNOSIS OF RMSF  No readily available test during acute illness  Antibody titers are usually negative during acute illness  Diagnosis is confirmed with a 4-fold change between acute & convalescent titer Has fever been present 2 or more days? used to make a treatment decision No Yes  Diagnostic tests cannot be Doxycycline Monitor patient with return next day Yes Is a rash present? Is thrombocytopenia No or unknown present? Is AST elevated? Recent tick exposure? R. PROWAZEKII IS THE ETIOLOGICAL AGENT OF EPIDEMIC TYPHUS  Epidemic typhus is one of the most significant infections in history  1812: 220,000 deaths among Napoleon’s army during the invasion of Russia  1990s: 45,000 cases during Burundi civil war  Occurs in conditions of overcrowding and poor hygiene, such as prisons and refugee camps Jail fever Camp fever Louse-borne typhus Soutama (Burundi) Epidemic typhus Bechah, Yassina, PhD, Lancet Infectious Diseases, The, Volume 8, Issue 7, 417-426 Copyright © 2008 Elsevier Ltd R. PROWAZEKII CAUSES AN ACUTE ILLNESS WITH THE POTENTIAL FOR RECURRENCE YEARS LATER Acute infection Brill-Zinsser disease  Incubation period 1–2 weeks  Recrudescent typhus  Abrupt onset with prostration, severe  Occurs years after acute headache, and high fever  Cough is prominent  Rash begins on trunk on 5th day  Involves entire body except face, palms, soles  Begins as macular, becomes maculopapular, petechial and confluent  Untreated CFR up to 40% infection  Probably a result of waning immunity EHRLICHIA AND ANAPLASMA REPLICATE IN THE PHAGOCYTIC VACUOLE Reticulate bodies Elementar y bodies  Target monocytes/neutrophils Endosome s  Two morphologic forms exist lysosome  Elementary bodies (0.2 to 0.4 μm) with dense cores  Reticulate bodies (0.8 to 1.5 μm)  Prevent phagosome fusion with the lysosome by inducing downregulation of the appropriate receptors  Replicating cells assemble into membrane-bound vesicles called morulae  Cells lack peptidoglycan and LPS Ehrlichia chaffeensis Anaplasma EHRLICHIA AND ANAPLASMA DISEASE Human Monocytic Ehrlichiosis (HME)  Ehrlichia chaffeensis Human Granulocytic Anaplasmosis (HGA)  Anaplasma phagocytophilum COXIELLA BURNETII IS THE ETIOLOGICAL AGENT OF Q (QUERY) FEVER  Primarily occurs in veterinarians, ranchers, and animal researchers that are exposed to infected goat and sheep placentas  Primary means of transmission:  Inhalation of infected aerosols  Ingestion of contamination milk  Vector-borne transmission is rare  Incubation period is 2 to 3 weeks  Past history as an offensive biological warfare agent COXIELLA BURNETII IS THE ETIOLOGICAL AGENT OF Q (QUERY) FEVER  Primarily occurs in veterinarians, ranchers, and animal researchers that are exposed to infected goat and sheep placentas  Primary means of transmission:  Inhalation of infected aerosols  Ingestion of contamination milk  Vector-borne transmission is rare  Incubation period is 2 to 3 weeks  Past history as an offensive biological warfare agent Annual incidence (per million) of reported Q fever, 2019 COXIELLA BURNETII IS THE ETIOLOGICAL AGENT OF Q (QUERY) FEVER  Primarily occurs in veterinarians, ranchers, and animal researchers that are exposed to infected goat and sheep placentas  Primary means of transmission:  Inhalation of infected aerosols  Ingestion of contamination milk  Vector-borne transmission is rare  Incubation period is 2 to 3 weeks  Past history as an offensive biological warfare agent Number of reported cases of Q fever, by month of onset–United States, 2000–2019 COXIELLA BURNETII IS THE ETIOLOGICAL AGENT OF Q (QUERY) FEVER  Primarily occurs in veterinarians, ranchers, and animal researchers that are exposed to infected goat and sheep placentas  Primary means of transmission:  Inhalation of infected aerosols  Ingestion of contamination milk  Vector-borne transmission is rare  Incubation period is 2 to 3 weeks  Past history as an offensive biological warfare agent Average annual incidence (per million population) of reported Q fever, by age group–United States, 2019 COXIELLA BURNETII IS THE ETIOLOGICAL AGENT OF Q (QUERY) FEVER  Primarily occurs in veterinarians, ranchers, and animal researchers that are exposed to infected goat and sheep placentas  Primary means of transmission:  Inhalation of infected aerosols  Ingestion of contamination milk  Vector-borne transmission is rare  Incubation period is 2 to 3 weeks  Past history as an offensive biological warfare agent Number of reported cases of Q fever –United States, 2000–2019 COXIELLA BURNETII SURVIVES IN THE PHAGOSOME  Preferred target is mononuclear phagocytes  Small cell variant is resistant to the environment and infectious (NOT a spore)  Large cell variant is the metabolically active form  Requires acidic environment for metabolic activities, so the organism allows fusion of endosomes with the phagocytic vacuole, but the organism blocks lysosomal fusion  This niche protects the bacteria from most antibiotics COXIELLA BURNETII IS THE ETIOLOGICAL AGENT OF Q (QUERY) FEVER  Primarily occurs in veterinarians, ranchers, and animal researchers that are exposed to infected goat and sheep placentas  Primary means of transmission:  Inhalation of infected aerosols  Ingestion of contamination milk  Tick-borne transmission does not occur  Incubation period is 2 to 3 weeks  Past history as an offensive biological warfare agent ACUTE Q FEVER MAY PRESENT WITH HEPATITIS OR PNEUMONIA; MAY BE DEPENDENT ON ROUTE OF INOCULATION Q fever hepatitis – likely from ingestion of contaminated milk Q fever pneumonia – likely from inhalation of infected aerosols CHRONIC INFECTION MAY LEAD TO ENDOCARDITIS IN A SUBSET OF PATIENTS Q fever endocarditis  My occur years after acute infection  Pregnant women, immunosuppressed patients and those with preexisting heart valve defects are at highest risk  Endocarditis comprises 60–70% of all reported cases of chronic Q fever  Untreated CFR of 25–60%  Long-term antibiotic therapy is required (>18 months)  Other forms of chronic infection include aortic aneurysms, infection of bone, liver or reproductive organs, such as the testes LABORATORY DIAGNOSIS OF THESE INFECTIONS IS TYPICALLY BASED ON SEROLOGY  Most common diagnostic technique is serological detection of antibodies in paired serum samples  IgG IFA assays should be performed on paired acute and convalescent serum samples collected 2–4 weeks apart to demonstrate evidence of a fourfold seroconversion.  Antibody titers are frequently negative in the first week of illness. RMSF cannot be confirmed using single acute antibody results.  The indirect immuno-fluorescent assay (IFA) is the gold standard for diagnosing rickettsial disease Rickettsia  Alternative options  PCR  Affected by cell tropism  May be used on skin biopsies or post-mortem tissue  Culture  Can be difficult and/or hazardous; limited to reference labs  Immunohistochemistry  Limited to skin biopsies or post-mortem tissue Ehrlichia TREATMENT AND PREVENTION OF RICKETTSIA, EHRLICHIA, AND COXIELLA INFECTION  Doxycycline is the treatment of choice for these infections  Chronic Q fever requires an extended course of doxycycline + hydroxychloroquine  In general, therapy should not be delayed to wait for laboratory confirmation  Infection is prevented by avoiding tick-infested areas  Do not consume raw milk or raw milk products (Q fever)  Vaccines are generally not available  A Phase I Q fever vaccine is available in Australia; not commercially available in US  Recommended for people engaged in research with pregnant sheep or live C. burnetii  Previous exposure to C. burnetii is a contraindication for vaccination due to a high risk for adverse reactions