Common Bacterial Pathogens Flashcards
Staphylococcus aureus
Gram (+) Cocci Grows in clusters (like Grapes)
Endogenous and Exogenous source of disease
Disease dependent on strain and circumstances
Makes Coagulase
Drug Resistance- Penicillin-r, Methicillin-r, vancomycin-r Cutneous, Toxinogenic and Pneumonia infections
Staphylococcus epidermidis
Gram (+) Cocci, a SSNA (Staph Species not aureus)
Skin Flora
Biofilm formation (glycocalyx)
Adheres to foreign bodies
Treatment is usually removal of foreign devices
Streptococcus pyogenes
Group A Strep
Lancefield Group: B-hemolytic strep
Normal flora in subset of population
Strep Throat can lead to glomerulonephritis and Rheumatic Fever
Toxinogenic
Streptococcus pneumoniae
Gram Positive diplococus
Normal Flora in UR tract of 40%
Leads to:
Noninvasive: pneumonia, sinusitis,
nvasive: meningitis, septicemia
Enterococccus faecalis and Enterococcus faecium
Gram Positive diplococcus
ses enterococcal infections
Urinary tract, surgical and biliary tract infections
Cause of nosocomal infections
Mixed infection
Intrinsic and emerging acquired resistance
Clostridium difficile
Gram Positive Rod
Anaerobic Spore forming- not killed by alcohol
Typically hospital acquired
Part of the normal flora in 10%
Resistant to a lot of drugs
Diarrhea and pseudomembranous colitis
Normal flora is suppressed by atbx treatment, so C. diff proliferates
Clostridium tetani
Gram (+)
Strict anaerobe
Spore formation
Localized infection
Toxin infection
Blocks INHIBITORY interneurons (important for relaxation)
Natural Immunity DNE
Clostridium botulinum
Gram (+)
Toxin targets achetylcholine transmission (flaccid paralysis)
Common in home canned, but normaly soil
Clostridium perfringens
Gram (+)
Anaerobic
Cause of gas gangrene
Wound infection (cellulitis, to fasciitis, to myonecrosis)
Alpha toxin kills neutrophils
Escherichia coli
Gram (-) Rod
Normal GI flora
GI disease- depends on strain
ATBX treatment is not usually indicated
Also UTIs
Pseudomonas aeruginosa
Gram (-) Rod
Environmental organism
Infects traumatic injuries, surg woudns and burns
Cystic Fibrosis lungs
Neisseria gonorrhoeae
Gram (-) dipplococci
Lots of antigenic variation
Infecitvity ffacilitated by pili
Adhere, interfere with neutro killing
Bacteroides fragilis
Aero tolerant
Gram(-) Rod
Lives in your mouth and tissues adjacent to oral cavity
Virulence factors: tissue destruction enzymes, capsule, superoxide dismutase
Chlamydia trachomatis
Intracellular bacteria (obligate)
Elementary body (infecitous particle)
Causes trachoma (blindness) and genital infections
Mycoplasma pneumoniae
No cell walls
Amorpheus
Atypical pneumonia
Adheres to respiratory epi cells, extracellular
Cutaneous infections
Localized focal abscess
Bacteria need to adhere, have pore forming toxins, impair phagocytosis, wall itself off
Protein A
Cellbound/Secreted protein that attaches to the Fc portion of antibodies and downregulates phagocytosis
Scalded Skin Syndrome
Local infection, toxin mediated, systemic effects
Mediated by a serine protease for desmoglein I, a protein responsible for the adherence between the epidermis and the dermis
More widespread in children, localized in adults
Toxic Shock Syndrome- TSST
Local infection, toxin mediated (super antigen)
Staph A main cause, sometimes streptococci
Requires O2, neutral pH, high protein concentration
High fever, shock, vomiting, muscle, eventually leading to multiple organ failure
Staph Food Poisoning
Ingestion of superantigen toxin Vomiting and diarrhea
Super Antigen
Even in the absence of a specific antigen, it facilitates the binding of the MHC molecule and T-cell receptor and activates it without an actual antigen
Streptococci
Catalase negative Chains or pairs Gram (+) S. pyogenes S. pneumoniae E. faecalis E. faecium
Streptococcal Pharyngitis “Strep Throat”
S. pyogenes
Asymptomatic carriers possible
Spread by droplet/nasal secretions
Self limiting
Post infection can lead to glomerulonephritis and/or Rheumatic
Fever Bugs need to: adhere (M-protein), invade, reduce phagocytosis (M-protein)
M Protein on Strep
Helps with Adhesion
Antiphagocytic properties- Binds factor H (surface marker on a lot of cells), reduces C3b (reduction in opsoninization) on surface and produces C5a peptidase (anaphylotoxin and chemotaxin) Strep antibodies tend to target this
Rheumatic Fever
Some M-types associated with rheumatic fever
Shares antigenic similarity with protein components in heart and heart valve
Glomerulonephritis
Non a specific antigen or antibody and it’s filtered out by the kidney, where it deposits on the basement membrane
Complement mediated damager
Infective Endocarditis
Infection of heart valves S, aureus
VIridans Streptococci
Coagulase-negative staphylococci
Streptococcus pneumoniae Pathogenesis
Capsule- antiphagocytic, plosysaccharide, 91 antigenic types
Anti-capsular antibody for recovery Multiple types of this capsule T-Cell independent antigen
Pneumococcal Disease Predisposing factors
Young (<6mo) and old Alcoholism (mucocillary defect)
Respiratory Viral Infection
Pneumococcal Vaccine
23-Valent vaccine for adults
Good against invasive diseases but not pneumonias 7-,13- valent for kids (more dependent on herd immunity)
Conjugate them to immunogenic carrier proteins (eg. diptheria)!
That’s how this works for kids
Staphylococcus aureus
Note:
Gram positive cocci
“Grapes”
Staphylococcus epidermidis
Note: They form a biofilm
Staphylococcus pyogenes
Streptococcus pneumoniae
Note:
Diplococcus
Enterococcus faecalis /faecium
