MICRO - Bacteria Associated with CVS and Lymphatic Infections 6 (Rickettsia, Yersinia, Brucella)

Rickettsiaceae

Which bacterial family includes the human pathogens Rickettsia and Orientia?

Obligate intracellular

What type of parasite describes Rickettsia due to its requirement for living host cells?

Transovarial transmission

What arthropod-borne mechanism allows infection to pass from vector mother to offspring?

Vector reservoir

What two arthropod roles allow Rickettsia to persist and spread disease?

Giemsa, Gimenez

Which stains are most useful for identifying Rickettsia in tissues?

OmpA and OmpB

Which outer membrane proteins mediate host cell adherence in Rickettsia?

Endothelial cells

What cells of the human body are the primary targets of Rickettsia?

Vasculitis

What pathological lesion results from Rickettsia damage to endothelial cells?

DIC

What severe coagulation disorder may complicate advanced rickettsial infection?

Cell-mediated immunity

What type of immunity is essential for stopping Rickettsia multiplication?

Rickettsia prowazekii

What organism causes epidemic typhus in humans?

Human body louse

What vector transmits epidemic typhus?

Brill-Zinsser disease

What milder relapse condition follows latent R. prowazekii infection years later?

Ricketssia typhi

What organism causes endemic (murine) typhus?

Rat flea

What vector transmits murine typhus from rodents to humans?

Rickettsia rickettsii

What organism causes Rocky Mountain spotted fever?

Dermacentor variabilis

What tick vector transmits R. rickettsii in the eastern United States?

Centripetal rash

What classical rash pattern begins on wrists and ankles and spreads to the trunk?

Rickettsia conorii

What eschar-forming organism causes Mediterranean spotted fever?

Rickettsia akari

What organism causes rickettsialpox transmitted by mouse mites?

Brain

What organ shows characteristic “typhus nodules” in rickettsial infections?

Hepatosplenomegaly

What systemic organ enlargement may occur due to rickettsial infection?

Vascular permeability

What endothelial process causes edema and hemorrhage in Rickettsia infections?

Lymphocytes

What immune cells infiltrate perivascular areas during rickettsial vasculitis?

IFN-y

What major cytokine activates endothelial cells to kill Rickettsia?

NK cells

What innate lymphocyte contributes IFN-γ and perforin-mediated killing?

TLR receptors

What innate receptor family detects Rickettsia and induces IL-6 and TNF-α?

NRLP3

What inflammasome becomes activated during rickettsial infection?

IL-1B

What cytokine is produced due to inflammasome activation?

CD8 T cells

What T-cell subset performs cytotoxic killing of infected endothelial cells?

CD4 T cells

What T-cell subset becomes suppressed (“anergic”) in severe Rickettsia?

Tregs

What regulatory cell type contributes to immunosuppression in severe disease?

IDO

What enzyme produced by endothelial cells restricts bacterial growth via tryptophan depletion?

Autophagy

What cellular process in endothelial cells helps degrade intracellular Rickettsia?

Macrophages

What immune cell type may harbor Rickettsia when not fully activated?

Shock

What physiologic failure results from widespread vascular leakage?

Microvasculature

What organ system is primarily damaged in severe endothelial dysfunction?

Tissue necrosis

What type of necrosis may occur due to thrombosis in small vessels?

Immune balance

What is the main determinant of rickettsiosis severity?

Dysregulated immunity

What immunologic failure leads to severe or fatal Rickettsia infection?

Rickettsia prowazekii

What organism is the agent of epidemic typhus?

Body louse

What arthropod transmits epidemic typhus?

Louse feces

What is the primary mode of entry of R. prowazekii into skin?

Brill-Zinsser disease

What dormant relapse form of epidemic typhus occurs years later?

Rickettsia typhi

What organism causes endemic (murine) typhus?

Rats

What animal serves as the reservoir for R. typhi?

Rat flea

What vector transmits endemic typhus?

Rickettsia rickettsii

What organism causes Rocky Mountain spotted fever?

Dermacentor variabilis

What U.S. tick species is the main vector of RMSF in the east?

Dermacentor andersoni

What U.S. tick species is the main vector of RMSF in the west?

Centripetal rash

What rash in RMSF spreads from wrists/ankles to the trunk?

Palms and soles

What body areas show RMSF involvement unlike most other rickettsioses?

Encephalitis

What severe CNS manifestation can occur in RMSF?

Rickettsia conorii

What spotted fever species produces the eschar called “tache noire”?

Orientia tsutsugamushi

What organism causes scrub typhus?

Mite

What arthropod transmits scrub typhus?

Rodents

What animal is the reservoir of O. tsutsugamushi?

Eschar

What classic necrotic lesion forms at the mite bite site in scrub typhus?

Conjunctival injection

What ocular complication appears in severe scrub typhus?

Systemic vasculitis

What term describes the severe multi-organ involvement in advanced scrub typhus?

Ehrlichia

Which bacterial genus causes Human Monocytic Ehrlichiosis?

Ehrlichia chaffeensis

Which species specifically causes Human Monocytic Ehrlichiosis?

Monocyte

Which leukocyte is infected in Human Monocytic Ehrlichiosis?

Morula

What intracellular inclusion forms in monocytes during ehrlichiosis?

Lone Star tick

What tick transmits Ehrlichia chaffeensis?

Anaplasma

Which bacterial genus causes Human Granulocytic Anaplasmosis?

Anaplasma phagocytophilum

Which species specifically causes Human Granulocytic Anaplasmosis?

Neutrophil

Which leukocyte is infected in Human Granulocytic Anaplasmosis?

Morula

What intracellular structure is found in neutrophils in anaplasmosis?

Ixodes tick

What arthropod vector transmits Anaplasma phagocytophilum?

Leukopenia

What common laboratory abnormality in ehrlichiosis shows low white blood cells?

Thrombocytopenia

What platelet abnormality commonly appears in both ehrlichiosis and anaplasmosis?

Elevated transaminases

What liver-related abnormality is common in ehrlichiosis?

IFA

Which diagnostic test is the gold standard for ehrlichiosis and anaplasmosis?

PCR

Which molecular method is the most sensitive early diagnostic test?

Doxycyline

What broad-spectrum antibiotic is the treatment of choice for ehrlichial infections?

Fluoroquinolones

What antibiotic class is ineffective in treating ehrlichiosis?

Rash

What symptom is notably rare in ehrlichiosis, distinguishing it from Rickettsia infections?

Meningoencephalitis

What severe neurologic complication may occur in untreated ehrlichiosis?

Myocarditis

What severe cardiac condition may develop in advanced ehrlichiosis?

Coxiella burnetii

Which bacterium is the causative agent of Q fever?

Small cell variant

What unique spore-like structure allows Coxiella burnetii to resist environmental stress?

Phagolysosome

What intracellular compartment does Coxiella replicate within?

Gimenez stain

What stain is used to visualize Coxiella organisms in tissues?

Phase I

What antigenic phase of Coxiella burnetii is virulent?

Phase II

What antigenic phase of Coxiella burnetii is avirulent?

Inhalation

What is the most common transmission route of Q fever to humans?

Farmers

What occupational group has the highest risk of Q fever exposure?

Sheep, goats, cattle

What animals commonly serve as reservoirs for Coxiella burnetii?

Unpasteurized milk

Which dairy product may transmit Q fever if not properly treated?

Acute Q fever

What form of Q fever typically presents as atypical pneumonia?

Phase II antibody

Which antibody type rises during acute Q fever infection?

Endocarditis

What chronic condition is strongly associated with persistent Coxiella infection?

Phase I antibody

Which antibody is elevated in chronic Q fever cases?

Doxycycline

What is the recommended treatment for acute Q fever?

Doxycycline + hydroxychloroquine

What drug combination is used for chronic Q fever therapy?

18 months

What is the minimum duration of treatment for chronic Q fever?

Pasteurization

What standard food-processing step prevents Coxiella transmission?

BSL-3

What laboratory infection category requires special containment for Coxiella?

Aerosol stability

What environmental feature contributes to the wide distribution of Q fever?