Infectious Disease: Bacteria

crystal violet

what is the water soluble dye used in gram staining?

peptidoglycan wall

what part of the bacteria does the gram stain adhere to?

purple

what color is a gram positive bacteria?

pink

what color is a gram negative bacteria?

safranin or fuchsine

counterstain that stains gram - bacteria pink

gram +

these bacteria have cell walls made of polysaccharides and charged amino acids in the peptidoglycan wall

lysozymes

what can digest gram + bacteria?

bile

gram + bacteria are resistant to ____

beta-lactam, glycopeptide

these 2 antibiotics interfere with gram + cell wall synthesis

gram -

these bacteria have an outer membrane, a thin peptidoglycan wall and an inner membrane

outer membrane

the ________________ protects gram - bacteria against antibiotics, detergents, and lysozymes

antigenic

lipopolysaccharides in the outer membrane of gram - bacteria can be _____

interfere with protein synthesis, inhibit DNA replication or folate synthesis

effective antibiotics for gram - bacteria do what?

bacitracin

interferes with gram + and gram - cell wall synthesis

pili

filamentous proteins that help bacteria bind to host surface and helps the bacteria resist phagocytic engulfment

bacterial ligands

bind to receptors on host cell (adhesions)

pili and adhesions

what establishes bacterial infection?

adhesions

basis of acquired immunity with bacterial infections

bacteremia

systemic immune response

exotoxins

excreted by bacteria, released from cells and may act at distant sites

endotoxins

cell-associated factors from gram - bacteria, usually lipids in the outer membrane/cell wall

cholera toxin

promotes secretion of fluid and electrolytes in intestinal epithelium leading to diarrhea

pesudomonas exotoxin A

inhibits protein synthesis in susceptible cells, resulting in death of the cells

botulinum toxin

inhibits presynaptic acetylcholine release from peripheral cholinergic neurons resulting in flaccid paralysis

tetanus toxin

inhibits neurotransmitter release from inhibitory neurons in the CNS resulting in spastic paralysis

anthrax toxin

induces cytokine release and death of target cells

staphylococcus aureus

separation of the stratum granulosum of the epidermis, between the living layers and the superficial dead layers

staphylococcus

• gram +

• causes styes, boils, sinusitis, pneumonia, toxic shock syndrome, and UTIs

• ubiquitous bacteria

phlyctenular keratoconjunctivitis

• immune response to exotoxins from a staphylococcal blepharitis

• tx is a combo of antibiotic & steroid eye drops to eliminate bacterial activity and suppress the inflammatory response

contact lenses

soak in bacterial exotoxins and irritate the cornea

blood

allows bacteria to flourish leading to exotoxin release causing vascular insufficiency and tissue necrosis

scalded skin syndrome

epidermolytic exotoxins cause detachment within the epidermal layer

MRSA

• now spreading & relatively common

• can cause necrotizing fasciitis, necrotizing pneumonia, infective endocarditis, cellulitis, abscesses, conjunctivitis

• potent membrane-destroying toxin kills leukocytes

• becoming more common in eye infections

culture

what should you do with all corneal ulcers?

change antibiotic

what should you do if the patient’s corneal ulcer doesn’t improve within a few days?

staphylococcus

• gram +

• grape-like clusters

• large, round, golden-yellow colonies on Mannitol salt agar

• catalase +

catalase

neutralizes H2O2, which is usually present in phagolysosomes that would digest foreign materials

S. aureus

• staph

• can be coagulase + or coagulase -

• bacteria coats itself with fibrin as camouflage from the immune system

resistance

culture bacteria with antibiotic tablets in plates to find out __________

streptococcus

• gram +

• different strains

• can cause corneal ulcers, rheumatic fever, childbirth fever, scarlet fever, erysipelas

exotoxins

staph and strep _________ open new tissues in the host to infection

septic shock

bacteria in the blood stream that can be fatal

septic shock, food poisoning, scalded skin syndrome

what are some complications associated with staph and strep infections?

pyrogenic exotoxins

• superantigens

• causes massive proliferation of T cells and massive release of cytokines into the systemic circulation

• results in high fever, hypotension

impetigo

• common childhood skin infection secondary to head lice

• staph or strep

• causes pustular lesions that usually start around the nose and spread over the face

  • highly contagious

honey yellow crust

what is the hallmark of impetigo?

furuncles

• staph or strep

• deep-seated infections around hair follicles

• boils

hordeolum

• boil of the meibomian gland

• staph

• sealed off inside gland where the immune system cannot attack

• can become a chalazion

carbuncles (cellulitis)

• deeper infection that spreads laterally under subcutaneous fascia

• staph or step

• can occur in the eye and travel to the brain from the eye

streptococcus

• gram +

• grow in pairs or chains

• catalase -

• lancefield subtyping subtypes differ by antigen on the cell surface

hemolysis

blood agar culture can be used to determine _____

bacillus anthracis

• causes anthrax

• spore-forming rods

• infection can be cutaneous, inhalation, or GI anthrax and then become systemic

• huge immune reaction pulls in neutrophils that liquefies organs

• has a poly-D-glutamyl capsule

poly-D-glutamyl capsule

characteristic of bacillus anthracis; protects it from phagocytosis and bactericidal components in serum and degradation in lysosomes

bacillus anthracis

• gram +

• non-motile

• non-hemolytic

• rough creamy white colonies

• ground glass appearance

protective antigen, edema factor, lethal factor

what are the 3 factors of anthrax toxin?

clostridium

• gram +

• rod shaped

• spore-forming rods

• obligate anaerobes

• can produce endospores

• pathogenicity due to production of toxins

c. botulinum (botulism)

• spore forming rods

• produces exotoxin that is a neurotoxin that blocks neurotransmitter release leading to muscle paralysis

• causes Bulbar palsy and descending paralysis with no fever and no change in mental faculties

• gram +

serum, stool, food

a lab test is necessary to detect botulism in what?

wrinkles, blepharospasm

what can botox be used as a treatment for?

incomplete blinks & dry eye

what are the side effects of botox?

c. tetani (tetanus)

• often acquired through contaminated puncture wound

• binds to peripheral nerve terminals & blocks release of inhibitory neurotransmitters causing continuous signaling to contract muscles

• gram +

c. difficile

• gram +

• antibiotic associated diarrhea

• antibiotics disrupt the normal GI tract flora and C. difficile overgrows

• treatment with antibiotics worsens

• exotoxin affects actin polymerization and cell signaling

• hides as an alcohol resistant spore form that can reactivate later

• can be treated by fecal transplant

diphtheria

• dead layer of throat epithelial cells that form a pseudomembrane

• strangler

• sx: upper respiratory illness with sore throat, fever

• rod bacteria with barred appearance

• exotoxin can be lethal causing cell death by inhibition of protein synthesis

neisseria

• gram -

• aerobic diplococci

• causes meningococcal meningitis

• virulence is associated with endotoxin and capsule formation

• eye acts as portal of entry into the brain

gonorrhea

• STD

• gram - cocci

• attracts PMNs

• ocular infection is highly purulent

gonorrhea

cause of the most rapid formation of pus in the eye for any bacteria

neisseria

• catalase +

• oxidase +

  • aerobic respiration

n. meningitidis

• type of neisseria

• use carbohydrate test

n. gonorrhoeae

• type of neisseria

• chocolate colored blood agar with antibiotics and nutrients to facilitate its growth and to kill other bacteria types

E. coli, salmonella, cholera, pseudomonas aeruginosa

what are some types of gram- rods?

pseudomonas aeruginosa

• gram- rod

• often low infectivity

• high virulence

• associated with CL wear

• biofilm formation

• secretes endotoxins and enzymes

• makes blue pigment

biofilm

forms as a goop of bacteria that are protected from normal cleaning

yes

can E. coli ferment lactose?

no

can salmonella, shigella, and pseudomonas ferment lactose?

pseudomonas

• can grow at 42 degrees C

• lactose negative

• may produce blue pigment

• grows on most agars

• fruity odor

coccobacilli

round to rod shape

haemophilus influenzae

• gram- coccobacilli

• causes meningitis, pneumonia

• eye is entry portal

• grown on chocolate colored blood agar (turns brown)

pertussis

• gram-

• causes whooping cough

• severe and deadly in children

• stage 1: colonization of upper respiratory tract

• stage 2: toxemic due to multiple toxins

• characteristic cough ends in a whoop

ciliated

pertussis bacteria is toxic to what type of epithelium?

lgeionella pneumophila

• bacteria live in water systems

• causes pneumonia and can be fatal with weak immune system

chlamydiae

• obligate intracellular

• gram-

• caused by: STDs, trachoma, psittacosis, lymphogranuloma venereum

trochoma

roughening of inner surface of the eyelids

trachoma

leading cause of preventable blindness in the world

purulent conjunctivitis

leads to lid scarring, trichiasis, entropion

keratitis

leads to pannuspan

nus

abnormal layer of fibrovascular tissue

follicular conjunctivitis, purulent conjunctivitis, keratitis, inclusion conjunctivitis, inflammation of follicles

what are eye complications associated with chlamydia?

upper & lower

inflammation on _________ eyelids indicated that it is not an allergy, instead is chlamydiae

trachoma

perinatal transmission of chlamydia can lead to a _____ like condition in newborn

Reiter’s syndrome

untreated chlamydia can lead to ______ (autoimmune disease)

rickettsia

• gram -

• obligate intracellular parasites

rocky mountain spotted fever, epidemic typhus (body lice), endemic typhus (fleas/rats)

what are the types of rickettsia diseases?

syphilis

• spirochete

• sexual and transplacental transmission

• primary infection causes a chancre

• spirochetes than disseminate by blood & lymphatics

primary syphilis infection

chancre at site of invasion full of spirochetes about 3 weeks after contact

luetic vasculitis

causes endothelial cells to proliferate and swell and the walls of the vessels become thickened by lymphocytes and fibrocytes

secondary syphilis infection

• appears 2-10 weeks after chancre with syphilis

• rash

• reoccurrence of lesions in anogenital region

• mucosal lesions in eye and tongue

• fever and swollen lymph glands

• thickening of blood vessels

• lymphadenopathy, mild fever, weight loss

tertiary syphilis infection

• long latency

• cardiovascular problems including thickening of large vessels

• neurosyphilis affects proprioception and nerve pain

• gummas

gummas

granulomatous lesions internally and externally

interstitial keratitis, deafness, saddle teeth

what is hutchinson’s triad?

microscopy

lab tests for primary and secondary syphilis infection