Intro to ID 2 Flashcards
What is the visual difference between gram-positive and gram-negative bacteria?
- gram-positive bacteria appear purple under a microscope due to thick peptidoglycan cell wall
- gram-negative bacteria appear pink/red under a microscope due to thin peptidoglycan cell wall
How do atypical bacteria stain?
Atypical bacteria do not stain using gram-stain
How do acid-fast bacilli (AFB) stain?
AFB are resistant to acids/ethanol based decolorization procedures
What is the morphology of most medically important gram-positive pathogens?
cocci
What form do staphylococcus take?
gram positive
clusters
What form do streptococci and enterococci take?
gram positive
Streptococci & enterococci appear in pairs or chains
Which biochemistry tests help to further differentiate gram-positive bacteria?
- catalase test
- coagulase test
- Catalase catalyzes the conversion of hydrogen peroxide to water oxygen. When a colony is placed in H2O2, liberation of O2 as gas bubble can be seen.
- Coagulase acts with plasma factor to convert fibrinogen to a fibrin clot.
What does the catalase production test differentiate between?
- staphylococci are catalase positive
- streptococci are catalase negative
Staph and strep are both gram-positive
What does the coagulase test differentiate between?
The coagulase test is used to differentiate staphylococcus aureus from other, less pathogenic staphylococci (CoNS)
- s. aureus is coagulase (+)
- s. epidermis is coagulase (-)
- CoNS = coagulase negative staphylococcus
Which biochemical test helps differentiate between the gram-positive pairs/chains?
Blood agar/hemolysis test
- alpha is partially hemolytic
- beta is completely hemolytic
- gamma is nonhemolytic
Which gram-positive, catalase-negative bacteria display alpha-hemolysis?
- streptococcus pneumoniae
- viridans streptococci
oral flora
Which gram-positive, catalase-negative bacteria display beta-hemolysis?
- streptococci pyogenes (Group A)
- streptococci agalactiae (Group B)
skin, pharynx, genitourinary
Which gram-positive, catalase negative bacteria display gamma-hemolysis?
- enterococcus faecium
- enterococcus faecalis
gastrointestinal
How are the gram-positive bacilli further differentiated?
- anaerobic vs aerobic
- spore forming vs non-spore forming
List the gram-positive bacilli bacteria that are anaerobic:
- spore forming: clostridium spp, clostridioides difficile
- non-spore forming: cutibacterium, actinomyces
spp = species
List the gram-positive bacilli bacteria that are aerobic:
- Spore forming: bacillus spp
- non-spore forming: corynebacterium, lactobacillus spp, listeria monocytogenes
What is the morphology of gram-negative bacteria?
- mostly bacilli
- some cocci
- some coccobacilli
List the gram-negative cocci pathogens:
- aerobic: neisseria spp, moraxella catarrhalis
- anaerobic: veillonella spp
List the gram-negative coccobacilli:
haemophilus spp
aerobic
How are gram-negative bacilli further differentiated?
- anaerobic
- aerobic, fastidious
- aerobic, oxidase (+), lactose fermenters
- aerobic, non-lactose fermenters
- aerobic enterobacterales, lactose fermenters
- aerobic enterobacterales, non-lactose fermenters
List the gram-negative, anaerobic, bacilli:
- bacteriodes spp
- fusobacterium spp
- prevotella spp
List the gram-negative, aerobic, bacilli, enterobacterales, lactose fermenting pathoges:
- citrobacter spp
- enterbacter spp
- e. coli
- klebsiella spp
CEEK
List the gram-negative, aerobic, bacilli, enterobacterales, non-lactose fermenting pathogens:
- morganella morgnaii
- proteus spp
- providencia spp
- salmonella spp
- serratia marcescens
- shigella spp
List the gram-negative aerobic bacilli that are oxidase-positive lactose fermenters:
- aeromonas hydrophila
- pasteurella multocida
- vibrio cholerae
List the gram-negative aerobic bacilli that are non-lactose fermenters:
- pseudomonas spp
- acinetobacter spp
- alcaligenes spp
- burkholderia cepacia
- stenotrophomonas maltophilia
List the gram-negative aerobic bacilli that are fastidious:
- campylobacter
- helicobacter
- bartonella
- haemophilus
- actinobacillus
- cardiobacterium
- eikenella
- kingella
List the atypical bacteria:
- chlamydia pneumoniae
- chlamydia trachomatis
- legionella pneumonphila
- mycoplasm pneumoniae
List the spirochetes:
- treponema pallidum (syphilis)
- borrelia burgdorferi (Lyme disease)
What is the oxidase test helpful in differentiating?
- Oxidase test help distinguish between enteric vs non-enteric lactose fermenters
Which pathogens are a part of the normal flora for skin?
- diptheroids (Corynebacterium spp)
- staphylococci
- streptococci
- cutibacterium acnews
- propionibacterium spp
Which pathogens compose the oropharynx (upper) normal flora?
- haemophilus spp
- streptococci (viridans group)
- diptheroids
- neisseria spp
- oral anaerobes
Which pathogens compose the normal flora for the GI tract?
- bacteroides spp
- enterobacterales
- enterococci
- fusobacterium spp
- peptostreptococcus spp
- clostridium spp
- lactobacillus
Which pathogens compose the normal flora for the genital tract?
- corynebacterium spp
- enterobacterales
- lactobacillus spp
- mycoplasma spp
- staphylococci
- streptococci
- anaerobes
- candida spp
