Gram - Bacteria Flashcards
T or F:all gram negative bacteria are cocci
F - gram negative bacilli and coccobacilli + cocci
Which bacteria are macConkey positive + oxidase negative
Enterobacteriaceae : E. coli, Shigella spp. Salmonella spp. etc
Acinetobacter spp.
T or F: All Enterobacteriacea are normally found in microbiome
F - some are (E. coli) but some are regularly pathogenic (salmonella and shigella)
Enterobacteriaceae traits
Facultative /oxidase -
- grow on MacConkey
- ferment glucose + produce gase
- reduce nitrate to nitrite
E. coli
Catalase -
Oxidase -
Ferment Lactose (pink)
Normally found in GI tract
Infections: UTI, neonatal meningitis
Shigella Spp.
Catalase -
Oxidase -
Hemolysis gamma
Doesn’t ferment lactose —- doesn’t turn red
Location: only found on us during infection
- causes dysentery (GI shit —- poop)
Salmonella spp.
Catalase -
Oxidase -
Gamma hemolysis
doesn’t ferment lactose
Location: intracellular pathogens, not normal flora
Disease: gastroenteritis, enteric fever
Acinetobacter spp. : shape
coccobacilli
Acinetobacter. spp traits
normally multidrug R
Catalase +
Obligate Aerobes/oxidase -
Hemolysis B (cause browning of agar)
Can’t ferment lactose
location: soil and water
Disease: commensals/ on us and doesn’t cause infection; sometime nosocomial
What are the Gram negative bacilli that are MacConkey + and Oxidase +
Pseudomonads
Pseudomonads traits
found in soil and water
- motile and non-spore forming
- aerobic/oxidase +
P. aeruginosa traits
- can form biofilms
- major pathogenic group
Catalase +, oxidase +
Beta hemolytic
Can’t ferment lactose (no red)
location: soil, water and skin
Infection: opportunistic
Toxins of P. aeruginosa
Pili, exotoxin A, endotoxins and R to antibiotics
Alginate: polysaccharide polymer that inhibits phagocytosis and contribute to infection in those with CF
Pyocyanin: blue green pigment that gives green colour, damages cells by making ROS
What gram negative bacteria are MacConkey - and Oxidase variable
Haemophilia: coccobacilli
Haemophilus spp. traits
small + not motile
requires enriched media with blood
Catalase +
Oxidase +
Don’t grow on blood agar / MacConkey agar
H. influenzae
Catalase +
Oxidase +
don’t grow on blood or MacConkey
Virulence: capsule, antiphagocytic pili
Diseases: meningitis, ear infection, bacteremia
Two categories of H. Influenzae
Typeable : based on capsule
Type B (Hib) most common one seen in human infections
—- vaccine for Hib not effective against non-typeable strains
H. ducreyi
Catalase +
Oxidase +
can’t grow on blood or MacConkey
Cause chancroid (STD)
T or F: Legionella pneumophila can grow on MacConkey
F- needs special media with Fe and cysteine
Legionella pneumophila
Catalase +
Obligate Aerobes - oxidase +
can’t grow on blood or MacConkey
Location: intracellular parasite, normally found in water
Disease: outbreaks in hospitals if in water ; no person to person transmission seen
- Legionnaires disease: wide range in traits
Pontiac fever: LRT + less severe
What are the gram - cocci
Neisseria : gonorrhoeae, meningitidis
Moraxella catarrhalis
Niesseria spp traits
non motile cocci (diplococci)
Catalase +
obligate aerobes
don’t grow on blood or macConkey
rarely ever cause disease
Neisseria gonorrhoeae
catalase +
obligate aerobe
Location: obligate pathogen
Leading cause of STD
Neisseria meningitidis
Catalase +
obligate aerobes
don’t grow on blood or MacConkey
Location: normally in throat; normally care with no symptoms
Disease: meningitis, bacteremia
