Intro to infectious disease

Question 1

Gram positive (structure)

Answer 1

cell wall Rigid, thick
Made up of mostly of peptidoglycan (50-60%)
A series of cross-linking (transpeptidases) help to create the building blocks of the cell wall.

Question 2

Gram negative (structure)

Answer 2

multiple layered structure
Cell Wall Thin layer-one or two glycan chains
Cell wall protected by lipoprotein outer layer-which functions as penetration barrier.
lipopolysaccharide (LPS)
Matrix protein (porin)-important for regulating influx of molecules
phospholipids

Question 3

Walls of mycobacteria (acid fast bacteria)

Answer 3

Contains peptidoglycan w/polysaccharide and glycolipids

Associated w/staining characteristics

Question 4

Cytoplasmic membrane

Answer 4

Osmotic barrier
Energy production (electron transport-energy gradient-ATPases)
Biosynthesis transport (nutrient uptake, enzyme secretion)
Protein and lipid—lacks sterols

Question 5

Minimum Inhibitory Concentration (MIC)

Answer 5

lowest concentration of antibiotic that inhibits visible growth of the bacteria. value used to indicate susceptible, intermediate and resistant

Question 6

List of Gram Positive Cocci (Aerobic)

Answer 6

Staphylococcus aureus (coag+): Methicillin-sensitive (MSSA), Hospital or Community aquired MRSA
Staphylococcus epidemidis (coag -)
Staphylococcus saprophyticus (coag -)
Enterococcus faecalis
Enterococcus faecium
Enterococcus durans
β hemolytic: Streptococcus pyogenes (Grp A), Streptococcus agalactiae (Grp B,) Streptococcus bovis (nonenterococci, Grp D)
Viridans streptococci – α hemolytic: Streptococcus sangius, Streptococcus salivarius, Streptococcus mitis, Streptococcus mutans
Streptococcus pneumoniae (pneumococcus)

Question 7

Staphylococci: colonization and infections caused

Answer 7

Colonization: Skin, Nose
Infections Caused: Cellulitis, wounds, trauma
Bacteremia/Endocarditis, Pneumonia,Osteomyelitis
UTI
Major players in post-surgical infections
Adhere to foreign material and catheters

Question 8

Staphylococcal resistance

Answer 8

Penicillin Resistance: Beta-lactamase production, > 90% of all staphylococcus are resistant to penicillin
Methicillin Resistance: MecA gene codes for novel PBP2a, ~50% of S. aureus are resistant, ~70% of CoNS are resistant
Methicillin-susceptible isolates are also susceptible to cephalosporins and carbapenems

Question 9

Streptococcus: Colonization

Answer 9

Skin: Group A- S. pyogenes
Mouth: Viridans Streptococcus, Anaerobes (e.g., peptostreptococcus)
Nasopharynx: Group A- S. pyogenes
Lower GI: Group D- S. bovis, Viridans, Streptococcus, Anaerobes
Female Genital Tract: Group B- S. agalactiae

Question 10

Streptococcus: infections caused

Answer 10

Cellulitis: Group A- S. pyogenes, may result in Nec fasciitis
Dental carries: Viridans Streptococcus
Pharyngitis (Strep throat): Group A- S. pyogenes
Bacteremia/Endocarditis: Viridans Streptococcus
Neonatal meningitis: Group B- S. agalactiae

Question 11

When establishing MIC, what is the difference between susceptible, intermediate, or resistant?

Answer 11

Susceptible- isolates may be appropriately treated with the recommended doses
Intermediate- isolates may be appropriately treated in body sites where the drug is physiologically concentrated or when a high dosage of drug can be used
Resistant- isolates are not inhibited by the achievable concentrations of a normal dose

Question 12

WBC with differential: parameters

Answer 12

Neutrophils 50-70%
Lymphocytes 25-35%
Monocytes 2-6%
Eosinophils 0-6%
Basophils0-3%

Question 13

granulocytes (B.E.N)

Answer 13

neutrophils, eosinophils, basophils

Question 14

Neutrophils

Answer 14

Prevent microorganism invasion, kill invading organisms
Attracted to site of infection by chemotactic factors
Phagocytize microorganisms- eat up invading organism
Release toxic substances from granules within cell into vacuole containing organism

Question 15

Absolute Neutrophil Count (ANC)

Answer 15

WBC # x (% segs (mature neutrophils)+ %bands (immature neutrophils)
The lower ANC= the higher risk for infection
Neutropenia defined based on ANC-
Mild = ANC 1000-1500/mm3
Moderate= ANC 500-1000/mm3
Severe= ANC < 500/mm3

Question 16

Lymphocytes

Answer 16

Effector cells of immune system, recognize invaders, tag them for removal and kill them.
Make antibodies
T cells- 80%
B cells- 20%

Question 17

Monocytes

Answer 17

precursors to macrophages

Serve to replenish tissues with macrophages prior to and during immune response

Question 18

Eosinophils

Answer 18

Responsible for immune processes against helminths and parasites (also involved in allergic reaction)

Question 19

Basophils

Answer 19

Mediate inflammatory response

Question 20

Gram+: Cocci (list)- Chains

Answer 20

CHAINS
Streptococcus pyrogens
Viridans Streptococcus

Question 21

Gram+: Cocci (list)-Pairs

Answer 21

PAIRS
Streptococcus pneumoniae
Enterococcus spp.

Question 22

Gram+: Cocci (list)-clusters

Answer 22

CLUSTERS
Coagulase-Positive Staphylococcus (S. aureus)
Coagulase-Negative Staphylococcus (S. epidermis)

Question 23

Gram+: Bacilli

Answer 23

Listeria

Lactobacillus

Question 24

Gram -: Cocci

Answer 24

COCCI
Neisseria menigitidis
Neisseria gonorrhoeae

Question 25

Gram -: Bacilli

Answer 25

``` Escherichia coli Klebsiella spp. Enterobacter spp. Proteus spp. Serratia marcescens Pseudomonas spp. ```

Question 26

Gram -: coccobacilli

Answer 26

Haemophilus influenzae

Question 27

Pneumococci: Colonization

Answer 27

Oropharynx | Nasopharnyx

Question 28

Pneumococci: infections caused

Answer 28

Otitis media Sinusitis Bronchitis Pneumonia (CAP- community acquired pneumonia)

Question 29

How do you treat Streptococcus

Answer 29

Penicillin | More resistance seen with α- hemolytic strep, specifically S. miti

Question 30

Concern for patients with Asplenia

Answer 30

Patients are at risk for fulminant sepsis syndrome Lack filtration mechanism of spleen macrophages Cannot clear encapsulated organisms (body requires spleen to clear the following bacteria) S. pneumoniae H. influenzae N. menigitiis

Question 31

Treatment of Pneumococci

Answer 31

3rd generation cephalosporins (ceftriaxone) May de-escalate with cultures and sensitivities (Penicillin not a good choice d/t resistance)

Question 32

Enterococci: colonization

Answer 32

Gastrointestinal tract Female genital tract Very resistant- harder to kill than staph or strep

Question 33

Enterococci: infections

Answer 33

Opportunistic- takes over when you lose normal flora or when immune system is compromised. Urinary tract infection Bacteremia/Endocarditis Intra-abdominal infections

Question 34

Gram negative (Aerobic) List

Answer 34

``` Rods: Enterobacteraciae: Enterobacter spp, Escherichia coli Klebsiella pneumoniae Proteus vulgaris, Proteus mirabilis Serratia marcenena Pseudomonas aeruginosa ``` Cocci/coccobaccilli: Haemophilis influenzae, Nisseiria meningitiis

Question 35

Enterobacteraciae (gram -)

Answer 35

GI tract colonization (Also: Soil,Water, Vegetation) Gram negative have Lipopolysaccharide (LPS), Cell wall component Acts as an Endotoxin

Question 36

Enterobacteraciae: infections

Answer 36

Urinary tract infections (accounts for 70%) Intraabdominal infections Bacteremia Nosocomial pneumonia (pts in hospital, not out in community) Diabetic foot infections

Question 37

Enterobacteraciae Resistance

Answer 37

Prevalent More common in hospital-acquired infections Treatment guided by in vitro susceptibility testing--cultures are essential

Question 38

Pseudomonas aeruginosa: colonization

Answer 38

Not considered normal flora (soil, water, vegetation) Can colonize upper respiratory tract of immunocompromised patients Cystic fibrosis COPD

Question 39

Pseudomonas aeruginosa: infections

Answer 39

Opportunist: Immunocompromised patient If pt has been on Broad spectrum antibiotics Ventilation equipment-psudomonas clings to equipment (thats why you see it in cystic fibrosis a lot). Nosocomial infections Hospital acquired pneumonia (HAP) Febrile neutropenia Skin and soft tissue infections (burns, trauma, post-surgical) Urinary tract infections (nursing home or hospital most likely)

Question 40

SPACE

Answer 40

``` Remembering when to double cover—treat these with 2 antibiotics: Serratia Pseudomonas Acinetobacter Citrobacter Enterobacter ```

Question 41

Gram – Coccobacilli

Answer 41

``` Haemophilus influenzae Encapsulated More virulent Not regular colonizer Causes meningititis ``` No capsule Colonizes upper resp tract Causes ottitis media, sinusitis, CA

Question 42

Polysaccharide Capsule

Answer 42

``` Eludes immune system Requires spleen for elimination PS capsule is target for vaccine Hib vaccine Meningococcal vaccine ```

Question 43

Anaerobes

Answer 43

Upper and lower GI tract, vaginal colonizers Associated with intraabdominal infection, aspiration pneumonia, endometritis, PID, diabetic lower extremity infections, dental carries, head and neck Above diaphragm Peptostreptococcus spp. (gram + cocci) Actinomyces spp (gram + rod) Fusobacterium (gram – rod) Below diaphragm Bacteroides fragilis (gram – rod) Lactobacillus (gram + rod) Clostridium spp (gram + rod) Gram-negative isolates are usually penicillinase producers

Question 44

Atypicals

Answer 44

``` Not normal colonizers Not able to gram stain Multiply intracellularly Examples: Mycoplasma pneumonia Legionella pneumophilia Chlamydophila pneumoniae ``` Can result in CAP (community acquired pnemonia)

Question 45

Even Some Super Killers Have Pretty Nice Capsules

Answer 45

``` Escherichia Coli Streptococcus Pneumoniae Salmonella Klebsiella pneumoniae Haemophilus influenzae Pseudomonas aeruginosa Neisseria meningitidis Cryptococcus neoformans (yeast) ```

Question 46

Nine Important “Classes” of Bacterial Pathogens (1-5)

Answer 46

Streptococci- Group A strep, viridans strep Streptococcus Pneumoniae Enterococcus- usually faecalis Staphylococci- S. aureus, coagulase-negative Atypical bacteria- Mycoplasma, Chlamydia, Legionella

Question 47

Nine Important “Classes” of Bacterial Pathogens (6-9)

Answer 47

Haemophilus influenzae Gram- negative rods- E.coli, Klebsiella, Proteus, etc. Pseudomonas aeruginosa Anaerobes- Bacteroides, Clostridia, Prevotella