Dermatologic Manifestations of Bacterial Infections Flashcards
What are the bacteria that cause rashes?
- Neisseria meningitidis*
- Staphylococcus aureus*
- Rickettsia rickettsii*
- Ehrlichia cheffeensis*
- Anaplasma phagocytophilum*
- Bartonella spp.*
- Borrelia burghodorferi*
- Treponema pallidum*
What are the Neisseria species that leads to skin manifestations?
Gram-negative diplococci
- N. meningitidis*
- N. gonorrhoeae*
- Moraxella catarrhalis*
general features of Neisseria meningitidis
five major serogroups - A, B, C, W-135, Y
- B, C, and Y are common in the US
- serogroup A causes major epidemics in sub-Saharan Africa, China, and South America
in the U.S., most disease is sporadic or occurs as part of small epidemics (college campuses, day-care center, etc.)
Neisseria meningitidis determinants of pathology
endotoxin
pili - antigenic variation and may avoid recognition by the immune system in this manner
polysaccharide capsule - resists phagocytosis and complement-mediated killing, antibodies to the capsule confer immunity
surface receptors that bind and remove iron from transferrin and lactoferrin
What are factors that help fight N. meningitidis infections?
carriage of this organism in the upper respiratory tract is at about 10% of the general population - not sure why these people are resistant
antibodies to the capsule confer immunity
complement is important in host resistance to N. meningitidis, particularly the terminal complement component (C5-C9)
individuals lacking functional spleens are more susceptible
What are the clinical disease of Neisseria meningitidis infection?
meningococcemia
meningitis
meningococcemia
caused by N. meningitidis
sudden onset of fever, chills, nausea, vomiting, rash (diagnostic), myalgia and arthralgias
rash may be maculopapular, petechial, or ecchymotic
in fulminant disease, patients present with a very rapidly progressive illness characterized by shock, disseminated intravascular coagulation, and multiple-organ failure
meningitis
caused by N. meningitidis
associated with meningococcemia
severe headache, confusion, lethargy, vomiting
leads to coma, seizures, and focal neurologic signs
What are the diagnostic laboratory tests for Neisseria meningitidis?
gram-negative diplococci can usually be seen in samples of cerebral spinal fluid
culture of blood or CSF samples
counterimmunoelectrophoresis or latex agglutination assays (can detect live or dead organisms and can be useful even after antibiotic treatment)
What is the treatment of a Neisseria meningitidis?
penicilin G
resistant isolates have been reported with increasing frequency
cephalosporins (ceftriaxone) are also very active
chloramphenicol should be used in patients with severe penicillin allergies
What is the prevention of Neisseria meningitidis?
MCV4 - meningococcal conjugate vaccine (menactra) - capsular polysacchries conjugated to diptheria toxin (ages 2-55)
MPSV4 - meningococal polysaccharide vaccine (menomune) - capsular polysaccharides without conjugate, and protection is about 3 years
prophylatic rifampin or ciprofloxacin
What are the skin manifestations of Staphylococcus aureus?
toxic shock syndrome - blanching erythematous rash, hypotension or shock, organ failure, high fever, vomiting, diarrhea, sore throat, muscle pain
dequamation of skin after resolution
tampon use or infected wounds
TSST-1 or endotoxin
general features of Rickettsia rickettsii
gram-negative rod
obligate intracellular pathogen - requires host cell nucleotide cofactors and ATP to multiply
cause of Rocky mountain spotted fever (RMSF) - most common in the central and mid-atlantic states
What are the determinants of pathogenicity for Rickettsia rickettsii?
transmitted through tick bites (American dog tick and Rocky Mountain wood tick)
disseminate via lymphatics and bloodstream
OmpA to attach to endothelial cells
induces its own engulfment by endothelial cells and subsequent escape from vacuole into the cytoplasm
multiples in cytoplasm
uses host action to propel itself through cytoplasm and spread
endothelial cells are eventually killed and leads to increase vascula permeability, edema, and hemorrhage
What is the clinical disease of Rickettsia rickettsii?
Rocky Mountain Spotted Fever (RMSF)
fever, headache, mailaise, myalgia, nausea, and vomiting
after a few days, a macular rash develops - starts from wrists and ankles and subsequently spreads to the rest of the body, evolves over several horus or days to petechiae
vascular damage can lead to edema
disseminated intravascular coagulation, thrombocytopenia, shock and organ failure may develop if not promptly treated
What are the diagnostic laboratory tests for Rickettsia rickettsii?
takes up gram stain poorly - best visualized by Giemsa stain
culture is difficult and hazardous to laboratory personnel
serological tests require both acute and convalescent sera, most patients will have negative titers at the time of presentation
immunohistologic examination of a cutaneous biopsy of a rash lesion
PCR
treatment should not be withheld while wiating for results
What is the treatment for Rickettsia rickettsii?
doxycyclin is the drug of choice
chloramphenicol is alternative - doxycycline allery and pregnant women
What is the prevention of Rickettsia rickettsii?
avoidance of tick bites
What are the general features of Ehrlichia chaffeensis?
causes erlichiosis - transmitted by tick bite (Lone Star tick)
infects monocytes and macrophages
presents with fever, headaches, myalgias, thrombocytopenia, and leukopenia
only a minority of patients (30%) develop a rash
organisms can be seen inside leukocytes as “mulberry”-like clusters called morulae
PCR diagnosis
What are the general features of Anaplasma phagocytophilum?
causes anaplasmosis
infects neutrophils
transmitted by tick bite (Ixodes scapularis)
clinically, causes disease similar to Ehrlichiosis
organism forms morulae inside neutrophils
What are the two medicall important Bartonella spp.?
- B. henselae*
- B. quintana*
What are the general features of Bartonella spp.
tiny gram-negative bacilli that invade the endothelial cells and erythrocytes
NOT obligate intracellular bacteria but are discussed here beause they were formerly classified as Rickettsiaceae
16S ribosomal sequencing shows that they are not obligate intracellular
What disease is called by Bartonella spp.?
bacillary angiomatosis
seen in immunocompromised invidiuals (especially those with AIDS)
vascular skin lesions that often resemble Kaposi’s sarcoma
may disseminate to almost any organ
cat-scratch disease
B. henselae -> an enlargement of one or more lymph nodes following a cat scratch or bite
What are the general features of Borrelia burgdorferi?
spirochete
microaerophilic (grows best in presence of lower levels of oxygen)
three main loci of endemicity - Northeast, Centra, and Pacific Coast
