keywords:
Bookmark and Share



Front Back
Mechanisms of Bacterial Injury
damage depends on ability of bacteria to adhere to host cells, invade cells & tissues, or deliver toxins
Tissue Tropism
bacterial proteins adhesins (fimbriae or pilli) bind to specific host receptors
Killing Host Cells
Intracellular bacteria: rapid replication & lysis; Shigella, E. Coli
Some live & multiply in the host cells; Mycobacterium tb, Listeria
Endotoxin
aka LPS, component of Gm- wall

causes septic shock by inducing high levels of TNF, IL1 & IL2
Exotoxins
proteins released by bacteria, cause damage to host tissues:
  • Enzymatic destruction: S. aureus exfoliative toxin
  • Binding component delivers a toxic active component in the cytoplasm of the host cells, altering singaling pway-->cell death; Bacillus anthracis toxins
  • Neurotoxins: block NT release-->paralysis; Clostridia
Superantigens
stimulate large #s of T cells to proliferate by binding MHC II molecules & TCRs & releasing cytokines-->TSS; S. aureus
Gram positive
  • Bacterial infectious diseases
  • Pyogenic cocci: Staph, Strept
  • Diptheria
  • Filamentous bacteria
Gram Negative
  • Bacterial infectious diseases
  • Gram neg. cocci
  • Infections in childhood
  • Gm neg. rods
Anaerobic Bacteria
  • Bacterial infectious diseases
  • Anaerobic abscesses
  • Anaerobic clostridia
Intracellular Bacteria
  • Bacterial infectious diseases
  • Chlymidia
  • Richettsiae
  • Mycoplasma
Other Bacterial infectious diseases
  • Mycobacteria
  • Spirochetes
  • STDs
  • Zoonotic Bacteria
Staphylococci
coagulase & β-lactamase producers--> Pen-Resis-strains; need (Nafcillin, Oxacillin, Diclociliin)-->Multi Drug resistant strains-->nosocomial infections
Staphylococcus aureus
  • hemolytic toxins--> lyse RBC & phagocytes
  • exotoxins--> split superficial epidermis from dermis (necrolysis): leaves pt. vulnerable for 2ndary infxn.
  • superAg--> Toxic Shock Syndrome & Food poisoning
S. aureus Exfoliation
Localized: bullous impetigo

Widespread: Scalded-skin syndrome
Staph Food Poisoning
bacteria in food produce enterotoxin

not destroyed by heating

Vom/Cramps/Dia
Staphylococcal PNA
PMN infiltrate

more destructive of lung tissue than pneumococcus


can--> acute endocarditis
Scalded Skin Syndrome
  • Staph infections
assoc. w/ S. aureus


sub-epidermal bleeding & large areas of skin exfoliation
Toxic Shock Syndrome
  • Staph infections

can also be caused by Strept. pyo

assoc. w/ use of vaginal tampons (hyper absorbent)  or infected surgical sites

Clinical: Medical emergency: hypotension (shock), renal failure, coagulopathy, liver disease, ARDS, generalized erythematous rash, soft tissue necrosis @ site of infx.  Untreated can be fatal
Localized Staph Infections
Abscesses: most often encountered
  • Furuncle (boil): in hair follicle
  • Carbuncle: involves several follicular abscesses-->skin necrosis & pus
Furunculosis
  • localized Staph infections
can develop w/ very virulent strains or IC
Hidradenitis suppurativa
  • Localized staph infx.
abscess formation of aprocrine gland of the axilla
Paronychia & Felon abscesses
  • Localized staph infx.
Paronychia: in nail bed
Felon: in fingertips


very painful


can occur w/ trauma or embedded splinters
Staph post surgery wound infection
can complicate normal healing of wound
Impetigo
today: more commonly caused by Staphylococcus


historically: more common w/ Strept.
Staphylococcal lymphadenitis
infection of lymphatic ducts & nodes
Chalazion
  • Staphylococcal infx.
lipo-granuloma of the Zeis & Meibomius embedded in eyelid fibrous tarsus
Periodontal abscess
  • Staph infx.
abscess around apex of the teeth


may produce fistulae to drain the pus to the skin
Staphylococcal Pus
draining pus from mastitis- abscess of mammary ducts

In osteomyelitis: osteonecrosis --> small bone pieces & osseous carries after draining pus
Spread of Staphylococcal Infx.
local--> lymphatics--> blood-->

cavernous sinus thrombosis
acute endocarditis
Cerebral & liver abscesses
Streptococcal Infections
  • Various Streptococci
  • Strept. pyo (Gp. A)
  • Strept. agalactiae (Gp B)
  • Enterococcus faecalis (Gp D)
  • Strept. viridans (α-hemolysis)
  • Strept. pneumoniae
  • Strept. Mutans: dental carries
Strept. pyogenes
--> pharyngitis, scarlet fever, erysipelas, impetigo, rheumatic fever, glomerulonephritis
Strept. agalactiae (Gp. B)
colonizes the female genital tract--> sepsis & meningitis (neonates)

chorioamnioitis
(pregnancy)
Enterococcus Faecalis (Gp. D)
--> endocarditis & UTIs
Strept. viridans
  • a-hemolytic
  • part of normal oral flora
  • --> subacute endocarditis
Strept. pneumoniae
community acquired PNA

meningitis (adults)
Types of Infections
  • Streptococcus
  • Primary: @ site of inoculation
  • Secondary: after spreading through blood to cardiac valves or meninges
  • Non-infective = immune complications: after a disease free interval--> rheumatic fever, immune complex glomerulonephritis, erythema nodosum
Scarlet Fever
  • Strept. pyogenes
Pharyngitis & Rash

from production of erythrogenic toxin
Streptococcal Throat
Pharyngitis: complicaionts--> peri-tonsillar abscess, ottitis media, meningitis
Streptococcal Impetigo
feet & facial papules w/ central necrosis covered by beeswax colored crust
Erysipelas
  • Strept. infx.
diffuse cellulitis: cheeks & foot

obese women
Puerperal fever
  • Strep. infx.
post-abortum & post partum endometritis
Neonatal Sepsis
  • Strept. infx
overwhelming neonate infection shortly after birth
Streptococcal Necrotizing Fascitis
destroys connective tissue of fascia
does not effect muscle as much

(Flesh eating bacteria = misnomer)
Corynebacterium diphtheriae: Diphtheria
Gm+ Rod: produces an exotoxin

Transmission: aerosols, skin shedding, asymptomatic carrier

Tropics: skin lesions in neglected wounds

Life threatening: croup w/ pharyngeal pseudo-membrane & toxin-mediated damage to heart & nerves

Decreased vaccination leads to outbreaks


Corynebacterium diphtheria: Exotoxin
may cause fatty myocardial change (myocarditis) & polyneuritis w/ myelin degeneration
Coryne. diphtheria: Morphology
necrosis of epithelium

PMN infiltrate, vascular congestion, interstitial edema, fibrin exudation

Coagulation of exudate
on necrotic surface creates a tough, dirty gray to black pseudo-membrane (in throat & bronchi)--> suffocation

May need emergency tracheostomy
Gram+ Filamentous Bacteria
Actinomyces

Nocardia
x of y cards Next > >> >|