23b: strep pneumoniae, listeria, anthrax - jonathan Flashcards
With regard to morphology, how do you distinguish between 1) Streptococci Group A through O
2) Streptococcus pneumoniae (pneumococcus)
3) Neisseria (gonorrhea and meningiditis)
1) Chains of G+
2) Diplococci with short dimension apposed
3) Diplococci with long dimension apposed
THIS WAS IN THE NOTES, NOT SURE ABOUT WHY. What are the features of Neisseria... Hemolytic status? Optochocin status? Bile status? Quellung status?
How does Viridians Streptococci compare on optochin and bile status?
Alpha hemolytic Optochin senstive (viridians strep are optochin-resistent) Bile solulbe (viridians are not soluble in bile) Quelling rxn used to determine capsule (over 90 different types)
What is the Quelling reaction?
The Quellung reaction is a biochemical reaction in which antibodies bind to the bacterial capsule of Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Haemophilus influenzae, and Salmonella. The antibody reaction allows these species to be visualized under a microscope. If the reaction is positive, the capsule becomes opaque and appears to enlarge.
Streptococcus Pneumoniae Gram status? Morphology? O2 status? Catalase? Oxidase? Optochin status? Bile solubility? Hemolytic status?
G + diplococci Faculative Anaerobe Catalase - Oxidase - Optochin SENSITIVE Bile SOLUBLE Alpha-hemolytic
Compare Strep Pneumoniae with Viridians Strep in terms of
Optochin
Bile solubility
Strep pneumoniae is optochin SENSITIVE and bile SOLUBLE
Viridians Strep is optochin RESISTANT and bile INSOLUBLE
Streptococcus pneumoniae pathogenesis... Where are these bacteria resident? What causes infection? How does the bacteria deal with IgA? What is its lytic compound?
Resident in the oropharynx
If aspirated plus cilia or phagocytosis is compromised, pneumonia can develop
Protease to IgA
Pnuemolysin
What are the clinical syndromes of Streptococcus pneumoniae?
What are the symptoms?
Bacteremic?
Fatal?
Pneumococcal pneumonia is the most frequent form of bacterial pneumonia
Cough, fever, chills, pleuritic pain, RUSTY SPUTUM, leukocytosis
15% bacteremic
15% fatal if hospitalized
Other syndromes include meningitis, otitis media, and sinusitis
Who is at highest risk for pneumococcal pneumonia?
Compromized HUMORAL immunity
Spleenectomized patients
pt with sickle cell anemia
What is laboratory Dx for pneumococcal pneumonia?
Microscopic examination and culture of sputum
Blood culture
CSF culture
What is Tx for pneumococcus?
What must be determined for adaquate Tx?
Multiple antibiotic resistance is frequent.
May be penicillin resistent
Sensitivity testing is required
What are the two vaccines for pnuemococcus?
Pneumovax is a 23 valent polysaccharide vaccine
Prevnar 13 is a conjugated vaccine conjugated to Diptheria proteins
Compare pneumovax to prevnar 13 with regard to…
Recommended for what populations?
T cell dependence or independence?
Which prevents pnuemococcal meningitis?
Pneumovax is recommended for pt over 65 and people over 2 years old who are at risk for infection (sickle cell, spleenectomy, HIV, and immunocompromised patients). T cell independent and has low booster yeilds.
Prevnar 13 is recommended as part of normal pediatric vaccination and prevents pneumococcal menigitis. T cell dependent
Bacteriology for Listeria monocytogenes... Gram status? Morphology? Hemolytic status? Motile? Temperature for growth?
G+ Rod
Beta-hemolytic
Motile with tumbling movement
Grows well at cold temperatures, and creates risk for food contamination
Epidemiology for Listeria monocytogenes…
Where is it found?
What foods are implicted?
Soil, water, and infected animals
Dairy and meat
What are the risks of a pregnant woman becoming infected with Listeria monocytogenes?
Early term?
Late term?
Who is susceptible?
Bacteremia and transplacental infection
Early term: abortion and still birth
Late term: live births with risk of neonatal septicemia and meningitis
Patients with cell-mediated immunosuppression are at risk
What is the pathogenesis of Listeria moncytogenes?
Invades mononuclear cells
Grows intracellularly
Moves from cell to cell by host actin filament
Escapes form host phagosome into cytosol by secreting cytolysin (Listeriolysin O)
What is Listeriolysin O?
A cytolysin secreted by Listeria that allows it to escape a phagosome
What are prevention practices for Listeria monocytogenes?
Pregnant women and immunosuppressed patients should avoid raw milk and unprocessed soft cheese
Bacteriology of Bacillus anthracis…
Gram status?
Spore?
O2 status?
G + rod, spore forming, aerobic
Epidemiology for Anthrax (Bacillus anthracis)…
Transmission?
Usually animal to animal.
Humans are an accidental host.
What are the three pathways for human infection by Anthrax?
Note: all of these come from animals.
Cutaneous anthrax
Inhalation anthrax
Intestinal anthrax
What are the two exotoxins of anthrax?
EDEMA FACTOR: adenylate cyclase which enters host cell and is activated by calmodulin
LETHAL FACTOR: disrupts signal transduction for cell division
What is the “protective antigen” of anthrax?
A protein that facilitates entry of exotoxins into host cells.
An antibody to this protein is protective
Cutaneous anthrax…
How does infection occur?
What is its distinctive symptom?
How serious is it?
Contamination of skin lesions by spores
The lesion now produces a BLACK SCAB
May lead to bacteremia
The most common and least serious anthrax
Inhalation anthrax... How does infection occur? What demographic is most at risk of exposure? What are the steps of infection? How serious is it?
Inhalation of spores
In undeveloped nations, people who work with wool and animal hides
Spores»_space; phagocytized by macrophages»_space; germinate in lymph nodes»_space; medialstinal lymph enlargement
Rapidly fatal
Intestinal anthrax…
What food source?
How common?
Ingestion of spores from meat.
Rare.
What are prevention efforts against Bacillus anthracis?
Who?
Vaccination
Veterinarians and military if biological warfare is possible.
What is Tx for Bacillus anthracis?
Ciprofloxacin
Tetracycline
Penicillin
What are the qualities of Ciprofloxacin…
Bacteria used on?
Cidal or static?
Mechanism?
Cidal G- often used for G- enteric bacilli DNA replication inhibitor Inhibits DNA gyrase
What are the qualities of Tetracycline?
Bacteria used on?
Cidal or static?
Mechanism?
Broad spectrum, especially used for intracellular bacteria (mycoplasm, rickettsia, chlamydia, bacillus anthracis)
Static
Protein inhibitor
Prevents t-RNA from binding to 30s subunit
What are the qualities of Penicillin?
Bacteria used on?
Cidal or static?
Mechanism?
Most G- and G+ G- enterics Cidal Cell wall synthesis inhibitors Prevents transpeptidase and peptidoglycan cross-linking
