Gram -

Question 1

obligate aerobic

Answer 1

require oxygen to grow and thrive
use oxygen for energy production and metabolism

Question 2

obligate anaerobic

Answer 2

can grow and thrive without oxygen and may even be harmed by its presence
use alternative electron acceptors and their metabolism is less efficient

Question 3

facultative

Answer 3

versatile/can adapt to different oxygen conditions
can grow and thrive in the presence of absence of oxygen

Question 4

human gut facultative anaerobes

Answer 4

can thrive in the presence of oxygen in the upper intestine
switch to anaerobic metabolism in the lower intestine where oxygen levels are lower

Question 5

carbohydrate fermentation tests

Answer 5

evaluate how a Gram negative organism generates energy from sugars and what metabolic byproducts are produced (outputs create visible changes in culture media)

Question 6

what is assessed in carbohydrate fermentation testing

Answer 6

sugar fermentation (ex. glucose, lactose, sucrose)
acid production
gas production

Question 7

high yield examples of carbohydrate fermentation testing

Answer 7

MacConkey agar
triple sugar iron (TSI) agar

Question 8

MacConkey agar

Answer 8

lactose fermenter -> pink colonies
non-lactose fermenter -> colorless

Question 9

Triple Sugar Iron (TSI) agar

Answer 9

glucose/lactose/sucrose fermentation
Gas and H2S production

Question 10

serovar

Answer 10

short for serological variant
subcategory of bacteria that shares certain antigenic characteristic
used to classify and distinguish closely related strains of a bacterial species based on the specific antigens present on their surgaves
antigens often associated with the bacterium’s cell wall, capsule, or flagella

Question 11

enterobacteriaceae

Answer 11

family gram-negative rods whose natural habitat is the intestinal tract
among largest bacteria
ferment glucose, reduce nitrates to nitrites, and are oxidase-negative

Question 12

enteric organisms

Answer 12

microorganisms that primarily inhabits the GI tract
is adapted to survive in bile, variable pH, and low oxygen environments
often belongs to Gram negative rod group

Question 13

enterobacteriaceae system of dividing species into serotypes

Answer 13

O = LPS
K = polysaccharide capsule
H = flagellar protein

Question 14

O antigen

Answer 14

outer membrane lipopolysaccharide (LPS)
antigen specificity is determined by variation in the sugar that form the long terminal polysaccharide side chains linked to the core polysaccharide and lipid A

Question 15

K antigen

Answer 15

cell surface polysaccharide may form a well-defined capsule or an amorphous slime layer providing protection from environmental pressures as well as host immune responses

Question 16

H antigen

Answer 16

mobile strains have peritrichous flagella which extend well beyond the cell wall and are called the H antigen called the H protein
many have adhesive surface pili which are protein structures that extend from the bacterial cell envelope and function to attach cells to surfaces

Question 17

fermenting glucose is not the same as

Answer 17

fermenting lactose
lactose fermentation is more specialized and unique

Question 18

enterobacteriaceae genus and species designations

Answer 18

based on phenotypic characteristics such as patterns of carbohydrate fermentation and amino acid breakdown
O, K, and H antigens used to further divide some species into multiple serotypes/serovars/subtypes

Question 19

genera containing the species most virulent for humans

Answer 19

Eschericheia
Shigella
Salmonella
Klebsiella
Yersinia

Question 20

beta-lactams (some)

Answer 20

bind penicillin-binding proteins (PBPs)
block peptidoglycan cross-linking
cause osmotic lysis

Question 21

why basic penicillins often don’t work against gram-negative bacteria?

Answer 21

unique in gram-negtivae, beta lactamases are located in the periplasmic space
places the enzyme directly between the drug and its target (PBPs)
beta-lactamase hydrolyzes the beta lactam ring before the drug can bind the PBPs and drug is inactivated prior to reaching peptidoglycan

Question 22

modified beta lactams

Answer 22

smaller, more hydrophilic, more stable than basic penicillins
improves their ability to traverse the outer membrane
higher affinity for Gram-negative PBPs and greater resistance to degradation
advance cephalosporins, carbapenems

Question 23

beta-lactamase inhibitors

Answer 23

clauvinic acid, taxobactam, sulbactam
function by competitively binding and inactivating beta-lactamases
protects beta lactam ABX from destruction
giving it time and concentration to bind PBPs and inhibit peptidoglycan cross linking
particularly effective against plasmid-mediated beta lactamases whcih are common among Gram negative organisms

Question 24

gram negative treatment

Answer 24

protein synthesis inhibitors
-30S ribosomal subunit
-50S ribosomal subunit

DNA/RNA synthesis inhibitors
Cell membrane disruptors

Question 25

30S ribosomal subunit

Answer 25

aminoglycosies ex. gentamicin, tobramycin MOA: protein mistranslation tetracyclines ex. doxycycline, minocycline MOA: block tRNA binding

Question 26

50S ribosomal subunit

Answer 26

macrolides (azithromycin) MOA: block peptide chain elongation

Question 27

DNA/RNA synthesis inhibitors

Answer 27

fluoroquinolones ex. ciprofloxacin, levofloxacin MOA: inhibit DNA gyrase

Question 28

Cell membrane disruptors

Answer 28

polymyxins ex. colistin MOA: disrupts outer membrane last resort for MDR organisms

Question 29

Escherichia coli (e. coli)

Answer 29

have flagella and are mobile part of normal intestinal flora but can also be cause of illness in humans virulence: evade host defenses and develop resistance to common ABXs facultative anaerobe fast lactose fermenter causative organisms of many diarrheal illnesses most common pathogen leading to cystitis

Question 30

Klebsiella

Answer 30

non motile facultative capable of fermenting glucose and lactose quickly, producing acid and gas during fermentation

Question 31

klebsiella virulence factors

Answer 31

capsule formation: protecting bacteria from host immune defenses pili LPS

Question 32

Klebsiella pneumoniae

Answer 32

range of clinical disease states including PNA, UTIs, septicemia

Question 33

pseudomonas

Answer 33

gram-negative rods aerobic non-fermentative oxidase positive

Question 34

pseudomonas virulence factors

Answer 34

adhesions, toxins, ability to form biofilms

Question 35

pseudomonas aeruginosa

Answer 35

wide range of clinical disease including lung infections, UTIs, swimmer's ear, septicemia known for its intrinsic ABX resistance, ability to acquire resistance through mutations and horizontal gene transfer ABX choice guided by susceptibility testing

Question 36

haemophilus

Answer 36

gram negative coccobacili (short round rods) non motile facultative anaerobe

Question 37

distinguishing feature of Haemophilus

Answer 37

growth requirement some species are obligate parasites, require specific growth factors not in standard laboratory media H. influenzae requires both X and V factors H. parainfluenzae only requires V factors

Question 38

X and Y factors

Answer 38

hemin (X factor) nicotinamide adenine dinucelotide (NAD, V factor)

Question 39

haemophilus virulence factors

Answer 39

adhesions and capsule which help attach to host cells and evade the immune system

Question 40

haemophilus influenzae (type B = Hib)

Answer 40

various clinical disease states including meningitis, PNA, epiglottitis, otitis media, sinusitis vaccination effective