Microbiology Flashcards
appendages of bacteria and their purpose
flagellum
- protein
- motility
pilus/fimbria
- glycoprotein
- helps bacteria adhere to cell surface
- forms “sex pilus” during conjugation (transfer of DNA from one bacteria to another)
components of bacterial cell envelopes
capsule (not all bacteria)
- polysaccharide
- protects against phagocytosis
slime (S) layer
- polysaccharides (loose network)
- helps with cell adhesion
- supports biofilm formation
- common in indwelling catheters
why can encapsulated bacteria cause more severe disease?
the capsule prevents macrophages from identifying the bacteria before opsonization with Ab, can hangout in the body and cause damage longer before they are identified
what are the important encapsulated bacteria?
Please SHine my SKis
- pseudomonas aeruginosa
- strep pnemoniae (not opsonized)
- H flu type B (not opsonized)
- neisseria meningitidis (not opsonized)
- e coli
- salmonella
- klebsiella pneumoniae
- group B strep
components of outer membrane of gram negative bacteria
outer leaflet: endotoxin (LPS/LOS)
- lipid A induces TNF and IL1
embedded proteins
- porins: transport across outer membrance (transmission of substances)
inner leafleft: phospholipids
difference in outer cell wall between gram - and gram + bacteria
gram neg bacteria
- outer membrane
- periplasm (space between cytoplasmis membrane and outer membrane, peptidoglycan is in the middle) - hydrolytic enzymes can accumulate here as they exit
gram pos
- larger cell wall
both have cell walls made up of peptidoglycan sugar backbones with peptide side chains
- rigid support
- protection against osmotic pressure damage
composition of cytoplasmic membrane
phospholipid bilayer sac with embedded proteins
- penicillin binding proteins > help with cell wall synthesis
- lipoteichoic acids (gram + only) extend from membrane to outer exterior (induce TNFa and IL1)
- site of oxidative and transport enzymes
explain gram staining
- crystal violent stain is applied
- iodine (fixes stain)
- alcohol (decolorizer; gram POS still retain violet dye due to their THICK peptidoglycan layer)
- counterstain > gram NEG appear red/pink
what are spores?
- only occur in gram POS bacteria (bacillus, clostridium)
- kertain-like coat, contains peptidoglycan, and DNA
- helps resist dehydration, heat, and chemicals
what are the urease positive organisms?
Pee CHUNKSS
- proteus
- cryptococcus
- H pylori
- Ureaplasma
- Nocardia
- Klebsiella
- S epidermidis
- S saprophyticus
positive versus negative stains
positive
- basic
- bacteria are neg (proteins)
- take up pos stain
- bacteria will be in color under microscopy
- ex: methalene blue
negative
- acidic
- bacteria are neg
- repel neg stain
- bacteria will be white/clear w color background under microscopy
- ex: india ink, nigrosin
what bacteria can not gram stain and why?
These Little
Microbes
May Unfortunately
Lack Real Color, But Are Everywhere
- Treponema, Leptospira (too thin)
- Mycobacteria (cell wall with high lipid content)
- Mycoplasma, Ureaplasma (no cell wall)
- Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, Ehrlichia (intracellular)
what is an acid fast/ziehl-neelsen stain
- stains acid fast bacteria (mycobacteria and nocardia)
- uses carbol fuchsin > turns bacteria red
what is choc agar
heated up blood agar
IDs H flu
what is macconkey agar
- fermentation produces acids
- colonies turn pink
- lactose-fermenting bacteria (enteric gram NEG) > colorless colonies
-** lactose fermenters (e coli, citrobacter, klebsiella, enterobacter) > pink colonies**
what is eosin-methylene blue (EMB) agar
colonies have green metallic stain
IDs: E coli
what is sabouraud agar
fungi exclusively; too acidic for bacteria
what are anaerobes? give examples
Cant Breathe Fresh Air
- clostridium
- bacteroides
- fusobacterium
- actinomyces israelii
what are the obligate intracellular bacteria
stay inside when its Really Chilld and Cold
- rickettsia
- chlamydia
- coxiella
what are the facultative intracellular bacteria
Some Nasty Bugs May Live FacultativeLY
- salmonella
- neisseria
- brucella
- mycobacterium
- listeria
- francisella
- legionella
- yersinia pestis
what does catalase do?
degrades H2O2 into water and oxygen; helps bacteria survive ROS
what are the catalase positive organisms?
Big cats Have BeeN to PLACESS
- bordatella pertussis
- h pylori
- burkholderia cepacia
- nocardia
- pseudomonas
- listeria
- aspergillus
- candida
- e coli
- serratia
- staphylococci
staphlycocci general characteristics
- skin/mucous membranes
- spherical cells in irregular clusters
- gram pos
- lack spores/flagella
- may have capsules
staph aureus effects, if any, on:
skin/skeletal
- boils, carbuncles
- impetigo
- scalded skin syndrome
- osteomyelitis
staph aureus effects, if any, on:
CV, lymphatic, systemic
- endocarditis
- TSS
staph aureus effects, if any, on:
GI
food intoxication
staph aureus effects, if any, on:
respiratory
pneumonia
coag-neg staph effects, if any, on:
skin/skeletal
surgical infections
coag-neg staph effects, if any, on:
CV/lymphatic/systemic
endocarditis
coag-neg staph effects, if any, on:
urogenital
UTIs
strep pyrogenes (group A) effects, if any, on:
skin/skeletal
- pyoderma (impetigo)
- erysipelas
- necrotizing fasciitis
strep pyrogenes (group A) effects, if any, on:
CV/lymphatic/systemic
- scarlet fever
- rheumatic fever
strep pyrogenes (group A) effects, if any, on:
respiratory
- pharyngitis (strep throat)
- sinusitis
strep pyrogenes (group A) effects, if any, on:
urogenital
glomerulonephritis
strep agalactiae (group B) effects, if any, on:
skin/skeletal
wound infections
strep agalactiae (group B) effects, if any, on:
nervous/muscle
neonatal meningitis
strep agalactiae (group B) effects, if any, on:
CV/lymphatic/systemic
- neonatal sepsis
- endocarditis
strep agalactiae (group B) effects, if any, on:
respiratory
neonatal pneumonia
enterococci effects, if any, on:
skin/skeletal
wound and surgical infections
enterococci effects, if any, on:
urogenital
healthcare associated UTIs
strep viridans effects, if any, on:
CV/lymphatic/systemic
subacute endocarditis
strep viridans effects, if any, on:
GI
dental caries
strep pneumoniae effects, if any, on:
nervous/muscle
pneumococcal meningitis (adult)
strep pneumoniae effects, if any, on:
respiratory
- pneumonia
- otitis media
- sinusitis
neisseria gonorrhoeae effects, if any, on:
skin/skeletal
gonococcal opthalmia
neisseria gonorrhoeae effects, if any, on:
urogenital
gonorrhea
neisseria meningitidis effects, if any, on:
nevous/muscle
meningococcal meningitis
staphylcoccus aureus general characteristics
- grows in large, round, opaque colonies
- facultative anaerobe
- withstands high salt, pH extremes, high temps
- produces many virulence factors
staphylcoccus aureus epidemiology/pathogenesis
- present in most environments frequented by humans
- readily isolated from fomites
- 20-60% in healthy adults in ant nares, skin, nasopharynx, intestine
- inc in community acquired methicillin resistance (MRSA)
- predisposition to infection: poor hygiene and nutrition, tissue injury, pre-existing primary infection, diabetes, immunodeficiency
staph aureus pathology
- localized skin infections (folliculitis, furuncle, carbuncle, impetigo)
- osteomyelitis
- bacteremia (>endocarditis)
- toxigenic dz (food intoxication, scalded skin syndrome, TSS)
coagulase negative staphylococci
healthcare associated and opportunistic infections in immunocompromised pts
- S epidermidis - skin and mucus membranes (endocarditis, bacteremia, UTI)
- S hominis - around apocrine sweat glands
- S capitis - around scalp, face, external ear
all three above can cause wound infections by penetrating through broken skin - S saprophyticus - infrequently lives on skin, intestine, vagina, UTI
what differentiates staph aureus from other staph species?
coagulase POS
streptococci general characteristics
- gram pos spherical/ovoid cocci in long chains, usu pairs
- non spore forming, non motile
- can form capsules and slime layers
- faculatative anaerobes
- no catalase, but have peroxidase system
- small, nonpigmented colonies
- sensitive to drying, heat, disinfectants
- most parasitic forms are fastidious and require enriched media
streptococcus subspecies breakdown
beta hemomlytic
- bacitracin sensitive: group A strep (pyogenes)
- bacitracin resistant: group B, C strep
alpha hemolytic
- optochin sensitive: strep pneumoniae
- optochin resistant: group D, viridans strep
strep pyogenes
hemolysis type
habitat
pathology
beta hemolytic
human throat
skin, throat infections, scarlet fever
strep agalactiae
hemolysis type
habitat
pathology
beta hemolytic
human vagina, cow udder
neonatal, wound infections
Strep equi
hemolysis type
habitat
pathology
beta hemolytic
various mammals
rare; abscesses
Strep dysgalactiae
hemolysis type
habitat
pathology
beta hemolytic
cattle
rare
enterococcus faecalis
hemolysis type
habitat
pathology
alpha, beta, N hemolytic
human, animal intestine
endocarditis, UTI
E faecium, E durans
hemolysis type
habitat
pathology
alpha hemolytic
human, animal intestine
endocarditis, UTI
strep bovis
hemolysis type
habitat
pathology
no hemolysis
cattle
subacute endocarditis, bacteremia
Strep sanguinis
hemolysis type
habitat
pathology
alpha hemolytic
human oral cavity
endocarditis
strep mutans
hemolysis type
habitat
pathology
no hemolysis
human oral cavity
dental caries
Strep pneumoniae
hemolysis type
habitat
pathology
alpha hemolytic
human respiratory tract
bacterial pneumonia
Strep anginosus
hemolysis type
habitat
pathology
beta hemolytic
humans, dogs
endocarditis, URT infections
strep salivarius
hemolysis type
habitat
pathology
no hemolysis
human saliva
endocarditis
strep pyogenes surface antigens
- C carbohydrates: protects against lysozymes
- fimbriae: adherence
- M protein: resistance to phagocytosis
- Hyluronic acid capsule: provokes no immune response
- C5a protease: hinders complement and neutrophil response
strep pyogenes major extracellular toxins
- streptolysins (hemolysins): streptolysin O (SLO) and streptolysis (SLS); both cause cell and tissue injury
- erythrogenic toxin (pyrogenic) - induces fever and typical red rash
- superantigens - strong monocyte and lymphocyte stimulants; cause release of tissue necrosis factor
strep pyogenes extracellular enzymes
- streptokinase: digests fibrin clots
- hyluronidase: breaks down CT
- DNase - hydrolyzes DNA
strep pyogenes epidemiology and pathogenesis
- humans only reservoir
- unapparent carriers
- transmission: contact, droplets, food, fomites
- portal of entry generally skin or pharynx
- children predominant group for cutaneous and thraot infxns
- sys infxn and progressive sequelae possible if untreated
strep pyogenes pathology
- skin infections (impetigo/pyoderma, erysipelas)
- throat infections
- systemic infections (scarlet fever via erythrogenic toxin, septicemia, TSS)
strep pyogenes/group A strep
long-term complications
- rheumatic fever: follows overt or subclinical pharyngitis in kids, carditis with extensive valve damage, arthritis, chorea, fever
- acute glomerulonephritis (PSGN): nephritis, inc BP, occ HF, can become chronic > kidney failure
strep agalactiae/Group B strep
location, transmission, pathology
- resides in human vagina, pharynx, large intestine
- can be transferred to infant during delivery and cause neonatal pneumonia, sepsis, and meningitis
- wound and skin infections and endocarditis in immunocompromised people
group D strep
name
location
pathology
- enterococus faecalis, e faecium, e durans
- normal colonists of human large intestine
- cause opportunistic urinary, wound, and skin infections, esp in immunocompromised ppl
groups C and G strep
location
pathology
- common animal flora, frequently isolate from upper respiratory
- pharyngitis, glomerulonephritis, bacteremia
strep viridans general information
- gums, teeth, oral cavity; nasopharynx, genital tract, skin
- alpha hemolytic
- not very invasive; dental/surgical procedures facilitate entrance
- strep mutans, oralis, salivarus, sanguis, milleri, mitis
strep viridans pathology
bacteremia, meningitis, abdominal infection, tooth abscesses
subacute endocarditis - blood bourne bacteria settle and grow on heart lining or valves
- ppl with preexisting heart dz at high risk
- colonization of heart by forming biofilms
strep mutans pathology
slime layers that adhere to teeth > basis of plaque
- dental caries
- give ppl with preexisting heart conditions prophylactic antibiotics before surgery or dental procedures
strep pneumoniae details and pathology
- small, lanclet shaped cells in pairs and short chains
- lack catalase and peroxidase (cultures die in O2)
- culture requires blood or chocolate agar
- causes 60-70% of bacterial pneumonias,
- otitis media
