Bugs Flashcards
Staphylococcus aureus
*Coagulase positive
Clumping factor (fibrinogen binding protein)
Intrinsically virulent organism
Skin syndromes - lots
Toxicities - scalded skin/bulbous impetigo, toxic shock syndrome
Staphylococci - general
Aerobic, gram positive, grape cluster
*Catalase positive - allows growth in oxygen
Positive or negative coagulase
*systemic infections can end up almost anywhere
Coagulase negative staphylococcus
About 30
S. epidermis - causes disease on medical devices
S. saprophyticus - causes uti in young women
Staphylococci reservoirs
Nose - s. aureus, often a source for bacteremia
Skin - s. aureus intermittently, all coagulase-negative
Staphylococcal virulence factors
*capsular polysaccharide = antiphagocytic
Protein a - binds Ig, possible immune evasion
Secreted factors
*antibiotic resistance - 60-70% MRSA nationwide, 50% at parkland
Beta hemolytic streptococci serogroups pathogenic for humans
- lancefield group A - pharyngitis
* lancefield group D - bacteremias associated with colon cancers
Group A streptococcal virulence factors
- adherence - m protein, lipoteichoic acids, fibronectin binding protein
- immune evasion - m protein, capsule, Ig binding protein, c5a peptidase
- invasion and spread
- toxicity - super antigens, pyrogenic exotoxins
Where are group a streptococci resident?
On skin and in throat, can include local and invasive infections and toxicity syndromes
Antibiotics don’t shorten duration of illness but can prevent later complications
Strep can spread to deeper tissues
Streptococcal toxicity syndromes and post infectious sequelae
Scarlet fever - skin infection following throat, lysogen if phages
Streptococcal toxic shock - follows invasive disease, bacteremia, superantigen, different than toxic shock from staph
Post - rheumatic fever (follows pharyngitis only), acute post-streptococcal glomerulonephritis (follows skin infection or pharyngitis)
Group b streptococci
Postpartum infections
Neonatal infections
Capsular polysaccharide - antiphagocytic, type 3 most associated with disease
Streptococcus pneumoniae
Gram positive, alpha hemolytic, grows in pairs, capsule
*optochin sensitive - rest of alpha streps resist lysis by this chemical
Otitis media in children, sinusitis, conjunctivitis, chronic bronchitis, pneumonia, meningitis
Polysaccharide adhesion factors adhere to n-acetylglucosamine for attachment
Enterococcus
Non hemolytic or weak alpha hemolysis Same group antigen as group d strep -*grows in 6.5% Salt, s. bovis does not - easy lab ID 12 species - 2 imp in humans Live in intestines of many animals Poor pathogen Nosocomial infections Vancomycin resistance
Bacillus anthracis
Aerobic, nonhemolytic, spore forming gram positive rod, chain like appearance histologically
Encapsulated - polyglutamic not carb
Intracellular pathogen of macrophages
Habitat is soil or GI tract of animals
Anthrax
Toxin mediated
Three main clinical syndromes - cutaneous, GI, inhalation
Inhalational - spores carried in macrophage to draining lymph nodes and germinate, form toxins to kill macrophage and other tissue, spread to blood stream and other organs
Bacillus cereus
Aerobic, spore forming gram pos. rod Soil and GI tract of herbivores Identical gram stain to b. anthracis GI disease - emetic, *classically associated with eating fried rice, diarrheal blood stream infections and cellulitis
Listeria monocytogenes
Non spore forming gram positive rod, beta hemolytic, aerobic coccobacillary Tumbling motility Intracellular - grows in cytoplasm *can grow at "deli temp" Animal reservoir, food borne disease *treatment is ampicillin
Enterobacteriaceae
Gram negative rods, facultative anaerobes Non spore forming Catalase positives Reduce nitrate to nitrite Ferment glucose and other sugars Motile with flagella Includes e. coli
E. Coli
Motile, facultative anaerobe, gram negative rod
Most commensal in GI tract
Most common syndromes - uti, diarrhea, neonatal sepsis and meningitis
*number 1 cause of UTI
E. Coli toxins
- heat labile toxins (plasmid)
- AB toxin, travelers diarrhea
- heat stable toxin (plasmid)
- shiga-like toxin (lysogenic prophage)
Vibrio
Curved GNR shaped like comma
Motile with single flagellum
*habitat = aqueous environments
Vibrio cholerae - classic syndrome
Heliobacter pylori
Curved motile GNR
microaerophilic - use amino acids for energy
*malignancies - gastric carcinoma, MALT lymphoma (can be cured by antibiotics)
Campylobacter
Curved, motile GNR
*temperature optimum of 42 deg c
Reservoir is birds - most chickens
Syndrome of febrile bloody diarrhea
Pseudomonas aeruginosa
GNR, motile with polar flagellum Aerobic, non fermenter *oxidase positive Fruity smell in culture Soil and water organisms *forms biofilms (imp in CF)
Pasteurella multocida
Nonmotile GNR
Kills many
Lives in mouths of cats and dogs
Francisella tularensis
Causes tularemia - zoonotic infection
Nonmotile GNR
Bioterrorism a gent
Acquired by skin puncture or inhalation
Legionella pneumophilia
Aerobic GNR
ubiquitous in water
Grows in macrophage
Community acquired pneumonia
Neisseria meningitidis and neisseria gonorrhoeae
Gram negative diplococci No motile, aerobic - do not ferment Require increased co2 for growth in lab Grow on chocolate agar Oxidase positive All other neisseria not pathogens IgA protease
The meningococcus
Reservoir is nasopharynx of humans
Epidemics in densely congregated of closed populations
Encapsulated
Vaccine effective against 4 of 5 disease serotypes (not B)
Most common cause of sporadic bacterial meningitis in young adults
The gonococcus
Humans only reservoir
Pilin for attachment
Phase variation for immune evasion
Anaerobes
Mouth - lung, oral, and pharyngeal abscesses, periodontal disease
*GI tract - comprise 99.99% of colonic flora - abdominal abscess
GU tract - PID, tubo-ovarian abscesses
Skin appendages - hair follicles and sweat glands
Chlamydia and clamydophila
*obligate intracellular parasites
Grow in culture on embryonic eggs or in tissue culture
Rigid cell wall - *no peptidoglycan
LPS
*cannot synthesize ATP - rely entirely on host
Different types of chlamydia
Chlamydophila pneumoniae - pneumonia
Chlymadophila psittaci - in birds, causes pneumonia syndrome
Chlamydia trachomatis - std, neonatal disease, ocular disease (leading cause of infectious blindness in the world)
Rickettsia
Structurally gram neg - LPS and peptidoglycan
*does not stain with gram stain
Obligate intracellular parasite - egg yolk and tissue culture
*replicate in endothelial cells of blood vessels
Rocky Mountain spotted fever and typhus
Rocky Mountain spotted fever
Mostly in southeast
Spring and summer peaks
One week incubation
First present with fever myalgias and headache
After one week rash - must treat presumptively before this
Epidemic typhus
Transmitted by human body louse
Problem in areas with poor hygienic conditions
Ehrlichia and anaplasma
Gram negative like with dual membrane but *no LPS or peptidoglycan
*no stain with gram stain - use wright or giemsa
Obligate intracellular parasite
E - in monocytes
A - in granulocytes
*acute febrile syndrome with blood cell abnormalities
Coxiella burnetii
Causes Q fever - acute (resolves without treatment) and chronic (endocarditis) and pregnancy (abortions and neonatal deaths)
Obligate intracellular parasite
Gram neg membrane but doesn’t stain with gram
*undergoes phase variation based upon LPS
animal reservoir - humans acquire by inhalation
Mycoplasma
*causes walking pneumonia = community acquired pneumonia
Spirochetes
Never cultivated in vitro
Too narrow tone seen in gram stain or light microscope - use dark field
In tissue use silver based stains - *warthin-starry or dieterle
Two membranes but not gram neg
*treponema and borrelia do not have LPS but leptospira does
Peptidoglycan
Periplasmic flagella and corkscrew motility
Treponema pallidum
Causes syphilis
Obligate parasites - humans only hosts, extra cellular
Microaerophiles
Not cultivable in vitro but can be in rabbits
Multiply locally and disseminate throughout body
Syphilis
3 stages
Primary - 3 weeks after infection, painless genital ulcer, heals on it own
Secondary - general rash resolves spontaneously, relapses
Then latency
Tertiary - skin and bones, cardiovascular, neurosyphilis
Treatment =penicillin
Borrelia
Lyme disease
Relapsing fever - endemic or epidemic
Lyme disease
Zoonotic, follows ioxodid ticks
Early - characteristic rash, joints, conduction abnormalities, neurological symptoms
Late - arthritis, carditis, neuropathy
Relapsing fever
Endemic - soft bodied ticks, rodent reservoirs with humans as accidental hosts
Epidemic - carried by body louse, humans only host, associated with unhygienic environments, more mortality
Leptospira
Has LPS
primarily disease of tropics and subtropics
Urban cycle in temperate environments
Zoonotic
*excreted in urine and contaminates water
Absorbed through skin or mucous membranes then bacteremia
Weil’s disease - bleeding, liver failure
Mycobacteria and filamentous bacteria
*slow growing
Resemble fungi on plates
Mycobacteria
Aerobic, sort of gram pos, lack LPS
*does not stain with gram stain
Waxy coat of mycolic acids - long chain fatty acids
Cell wall has LAM - glycolipid that is major virulence factor and modulates macrophage function and scavenges oxygen radicals
Cord factor - causes serpentine cords in culture, toxic to PMN, damages mitochondria, causes formation of granulomas
Acid fast staining
Acid fastness is property of mycobacteria and nocardia
Procedure analogous to gram stain
Background is blue
*“red snappers” = mycobacterium tuberculosis
Mycobacterium tuberculosis
Five species
Humans major reservoir - 1/3 of worlds population
Transmission usually through inhalation - does not require a lot
Ingestion also possible
Tuberculosis - engulfed by macrophages and inhibits phagolysosome fusion, resistant to reactive species and killing by macrophages, drain to hilar and mediastinal lymph nodes, then bacteremia
Stages of tuberculosis
Primary - most people a symptomatic, may present as pneumonia
Progressive - usually in elderly or immunocompromised
Re activation - about 4% per year first two years then 1% per year
Testing and diagnosis of tuberculosis
Skin testing - tuberculin, PPD Quantiferon - interferon gamma release assays Staining Culture - "gold standard" Molecular techniques - PCR, probes
Treatment of tuberculosis
Multiple drugs over extended periods of time
Multidrug resistant and extremely drug resistant tb exist
Nontuberculous mycobacteria
Runyon classification
Group 1 - photochromogens - produce pigment only in light
Group 2 - scotochromogens - produce pigment in light or dark
Group 3 - nonchromogens - no pigment
Group 4 - rapid growers
Mycobacterium avium complex
Runyon group 3 Ubiquitous in water environments Temp optimum of 41 deg c Causes avian tb Two major disease syndromes - lung disease and HIV infections
Mycobacterium chelonae
Associated with tattoos
Mycobacterium leprae
Morphologically identical and genetically related to m. Tb
Not cultivable in vitro but grows in footpads of mice or armadillo
Spread by respiratory or direct contact but transmission difficult
Incubation period 2-10 years
Treatment = dapsone, rifampin and clofazimine
Tuberculoid and lepromatous responses
Tuberculoid m. Leprae
Stronger T cell response
Fewer skin lesions
Localized skin reaction
Few bacteria
Lepromatous m. Leprae
Absent T cell response
Many modular legions - leonine faces
Abundant bacteria in lesions
Progressive clinical course
Nocardia
Gram pos - SOD and catalase Branching and filamentous Slow growing *weakly acid fast (modified acid fast stain) Shorter chain mycolic acids Soil bacteria Opportunistic pathogens Clinical syndromes - pneumonia, skin disease, long duration of treatment
Actinomyces
Filamentous branching gram pos rod
*does not stain with acid fast - no mycolic acids
Anaerobic or microaerophilic
Slow growing
Part of normal flora in mouth, GI tract, and GU tract - infections in immunocompromised host
Chronic draining sinuses - *“sulfur granules”
Clinical syndromes - bad dentition and lumpy jaw, thoracic descending infection, abdominopelvic after surgery or IUD
prolonged therapy with penicillin
