Chapter 2: Medically Relevant Bacteria (3) Flashcards
List some Viridans group Streptococcal species.
S. mutans; S. sanguinis; S. gallolyticus (bovis)
Features of scarlet fever?
blanching, sandpaper rash, strawberry tongue
Treatment options for Staphylococcus aureus?
Nafcillin/oxacillin for widespread penicillinase-producing strains
MRSA: vancomycin
VRSA (vancomycin resistant S. aureus) or VISA (vancomycin intermediate S. aureus) quinupristin/dalfopristin
Transmission of Streptococcus pyogenes?
direct contact; respiratory droplets
Pathogenesis/ Virulence factors for Strep pyogenes.
- Hyaluronic acid: is non-immunogenic
- M-protein: antiphagocytic, associated with acute glomerulonephritis, rheumatic fever
- Streptolysin O: immunogenic, hemolysin cytolysin
- Streptolysin S: not immunogenic, hemolysin/cytolysin
Spreading Factors
- Streptokinase: breaks down fibrin clot
- hyaluronidase: hydrolyzes the ground substance of the connective tissues
- Exotoxins A-C (pyrogenic or erythrogenic exotoxins)
-phage-coded (i.e., the cells are lysogenized by a phage)
-cause fever and rash of scarlet fever; superantigens
Lab diagnosis for Streptococcus pyogenes?
- Rapid strep test (ELISA-based) misses approximately 25% of infections. Culture all negatives.
- Ab to streptolysin O (ASO) titer of >200 is significant for rheumatic fever
- Anti-DNAse B and antihyalurondiase titers for AGN
Treatment for Streptococcus pyogenes.
beta lactam drugs, macrolides in the case of penicilin allergy
Prevention of Streptococcus pyogenes?
possible prophylactic antibiotics for at least 5 years post-acute rheumatic fever; beta lactams and macrolides
Transmission of GBS?
newborn infected during birth (increased risk of prolonged labor after rupture of membranes)
Treatment for GBS?
ampicillin with an aminoglycoside or a cephalosporin
Prevention of GBS?
- ampicillin or penicillin are the drugs of choice (to give to mother)
- clindamycin or erythromycin for penicillin allergies
Transmission of Streptococcus pneumoniae?
respiratory droplets (not considered highly communicable; often colonize the nasopharynx without causing disease)
Predisposing factors for Strep pneumoniae?
- antecedent influenza or measles infection
- COPD
- CHF (congestive heart failure)
- alcoholism
- asplenia predisposes to septicemia
What is the major virulence factor of Streptococcus pneumoniae.
- polysacchardie capsule is the major virulence factor
How is the pneumonia produced by Streptococcus pneumonia often desribed?
most common cause of typical penumonia presenting with lobar consolidation, blood-tinged, “rusty” sputum
How would you diagnose someone with S. pneumonia?
- Gram stain and culture of CSF or sputum
- Quellung reaction: positive (swelling of the capsule with the addition of type-specific antiserum, no longer used but still tested!)
- latex particle agglutination: test for capsular antigen in CSF
- urinary antigen test
Treatment for S. pneumoniae?
- beta lactams for bacterial pneumonia; ceftriaxone and cefotaxime for adult meningitis (add vancomycin if penicillin-resitant S. pneumoniae has been reported in community)
- amoxicillin for otitis media and sinusitis in children (erythromycin in cases of allergy)
Prevention for S. pneumonia?
- ab to capsule (>80 capsular serotypes) provide type- specific immunity
- vaccine
-pediatric (PCV, pneumococcal conjugate vaccine) 13 of the most common serotypes; conjugated to diphtheria toxoid; prevents invasive disease
-adult (PPV, pneumococcal polysaccharide vaccine) 23 of most common capsular serotypes
Describe transmission of Viridans Strep?
endogenous
Pathogenesis of Viridans group strep.
dextran (biofilm) mediated adherence onto tooth enamel or damaged heart valve and to each to other (vegetation); growth in vegetation protects organism from immune system
Strep gallolyticus is associated with what type of cancer?
colon cancer
What is the best treatment option of Viridans group strep?
penicillin G with aminoglycosides for endocarditis
Best prevention of Viridans group strep?
prophylactic antibiotics prior to dental work for individuals with damaged heart valve
2 types of enterococcus species?
- Enterococcus faecalis
- Enterococcus faecium
Transmission of Group D strep?
endogenously
Best treatment plan for Group D strep?
all strains carry some drug resistance
- Some vancomycin-resistant strains of Enterococcus faecium or E faecalis have not reliably effective treatment; or low-level resitance use ampiciliin, gentamicin, or streptomycin
Prevention practices for Group D strep?
prophylactic use of penicillin and gentamicin for patients with damaged heart valves prior to intestinal or urinary tract manipulation
Which gram positive rod orgamism are facultative intracellular?
Listeria annd mycobacterium
Which Gram positive rods are acid fast?
mycobacterium and nocardia
Which gram positive rod bacteria have branching rods?
actinomyces and nocardia
Distinguishing features of Bacillus anthracis?
- large boxcar-like, gram positive, spore forming rod
- capsule is polypeptide (poly-d-glutamate)
- potential use in bioterrorism
Resovoir for Bacillus anthracis?
animals, skins (animal hides), soils
Transmission of bacillus anthracis?
contact with innfected animals or inhalation of spores (bioterrorism)
Some virulence factors/pathogenesis of bacillus anthracis.
- capsule polypeptide, anti-phagocytic, immunogenic
- anthrax toxin includes 3 protein components.
- protective ag (B component) mediates entry of LF or EF into eukaryotic cells
-Lethal factor kills cells
-Edema factor is an adenylate cyclase (calmodulin-activated like pertussis adenylate cyclase)
List the diseases that can be caused by bacillus anthracis.
- cutaneous anthrax
- pulmonary (woolsorter’s disease)
- GI anthrax (rare)
Describe cutaneous anthrax.
papule > papule with vesicles (malignant pustules) > central necrosis (eschar) with erythematous border often painful regional lymphadenopathy; fever in 50%
Describe Woolsorter’s disease.
life-threatening pneumonia; cough, fever, malaise, and ultimately facial edema, dyspnea, diaphoresis, cyanosis, and shock with mediastinal hemorrhagic lymphadenitis
Describe GI anthrax.
edema and blockage of G tract can occur, vomiting and bloody diarrhea, high mortality
Diagnosis of Bacillus anthracis.
- mediastinal widening on chest x-ray
- gram stain and culture of blood, respiratory secretions
- serology
- PCRT
Treatment for bacillus anthracis.
ciprofloxacin or doxycyline
Prevention of Bacillus anthracis.
toxoid vaccine (AVA, acellular vaccine adsorbed) is given to high risk occupations (milliary);
raxibacumab for prophylaxis
Bacillus cereus reservoir?
found in nature
