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835 > Bacterial Pathogens > Flashcards

Bacterial Pathogens Flashcards

1
Q

12 Considerations for Antibiotic Usage

A
  • *1. What condition are you treating?
  • *2. What bacteria generally cause this type of infection?
    3. What ABX are usually active against those bacteria?
    4. What are the local resistance patterns (Antibiogram)?
    5. Can the ABX reach the site of infection (organ penetration)?
    6. What is the optimal route of administration?
    7. Are there any contraindications?
    8. Are dose adjustments needed (renal/hepatic disease)?
    9. Are there any drug-drug interactions?
    10. Is monitoring required?
    11. Can a narrow-spectrum ABX be used after pathogen identification/sensitivities are available?
    12. What is the planned duration of therapy?
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2
Q

Main Bacteria Groups

A
  1. Gram “+”
  2. Gram “-“
  3. Anaerobes
  4. Atypicals
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3
Q

Gram “+” Examples

A
  • Staphylococci
  • Streptococci
  • Pneumococci
  • Enterococci
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4
Q

Gram “-“ Examples

A
  • Enterobacteriaceae
  • Pseudomonas
  • Gram-negative cocci/coccobacilli
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5
Q

Gram “+” Classifications

A
  • Shape
  • Production of proteins
  • Hemolysis capabilities
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6
Q

Gram “+” Cocci - 1st/2nd Differentiation

A
  • First: Catalase Test
  • Chains/Pairs: catalase “-“
  • Clusters: catalase “+”
  • Second: Coagulase Test (for catalase “+”)
  • Positive or Negative
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7
Q

Catalase Negative - Chain Examples

A
  • Streptococcus pyogenes (GAS)

- Viridans streptococcus

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8
Q

Catalase Negative - Pair Examples (Diplococci)

A
  • Streptococcus pneumoniae
  • E. faecalis (former Group D. Strept)
  • E. faecium (former Group D. Strept)
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9
Q

Catalase “+”/Coagulase “+” Example

A

S. Aureus (MSSA, MRSA)

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10
Q

Catalase “+”/Coagulase “-“ Example

A

S. epidermidis
S. lugdunensis
S. saprophyticus

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11
Q

Staphylcocci

A
  • Common colonizers of skin/nose and cause range of infections
  • Gram “+” clusters, Catalase “+” bacterium
  • Mild to severe skin infections (ABSSSI/SSTI), life threatening pneumonia, and endocarditis
  • Can also cause UTIs, post surgical infections, catheter infections, osteomyelitis, and more
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12
Q

MSSA

A

Methicillin-sensitive staphylcoccus aureus

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13
Q

MRSA

A

Methicillin-resistant staphylcoccus aureus

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14
Q

HA-MRSA

A

Heathcare-associated Methicillin-resistant staphylcoccus aureus

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15
Q

CA-MRSA

A

Community-acquired Methicillin-resistant staphylcoccus aureus

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16
Q

ABSSSI

A

Acute bacterial skin and skin structure infections

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17
Q

SSTI

A
  • Skin and soft tissue infections

- EX: cellulitis, furuncles/carbuncles, wounds, trauma

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18
Q

Biofilms

A
  • Innately resistant to antibiotics
  • Difficult to treat and act as a source for bacterial dissemination
  • May have to remove devices with biofilm development (catheters)
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19
Q

Biofilms + Abx Resistance

A
  • Slow growth/metabolism of bacterial in biofilm (Abx often target replicating/metabolically active bacteria)
  • Structure of biofilm (ECM proteins, bacterial proteins, dead bacteria, DNA) may limit penetration/diffusion
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20
Q

Streptococci

A
  • Gram “+”, catalase “-“
  • Chains/pairs
  • Differentiated by hemolytic phenotype on blood agar or by Lancefield system
  • Infections ranging from strep throat to endocarditis/meningitis
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21
Q

Streptococci + Blood Agar Types

A
  1. Alpha-Hemolytic: partial hemolysis, green/brown
  2. Beta-Hemolytic: complete, clear
  3. Gamma-hemolytic: no hemolysis
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22
Q

Alpha-Hemolytic Bacterium Examples

A
  • **S. pneumoniae
  • **Viridans streptococci
  • S. mutans
  • S. salivarius
  • S. mitis
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23
Q

Beta-Hemolytic Bacterium Examples

A
  • Broken down by Lancefield classes based on cell wall carbohydrates
  • **Group A S. pyogenes (GAS)
  • Group B - S. agalacitae
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24
Q

GAS Infection Examples

A
  • Cellulitis, necrotizing fasciitis (SSTI)
  • Pharyngitis (strep throat)
  • Rheumatic fever
  • Scarlet fever
  • Glomerulonephritis
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25
Q

Group B S. Agalacitae Infection Example

A

Neonatal meningitis

26
Q

Viridans Streptococci Infection Examples

A
  • Dental caries

- Bacteremia/endocarditis in immunocompromised

27
Q

Streptococcus Pneumoniae

A
  • One of the most common causers of URTI
  • Alpha hemolytic
  • Gram “+” diplococci
  • Polysaccharide capsule is target for vaccine
28
Q

URTI

A

Upper respiratory tract infection

29
Q

Streptococcus Pneumoniae Infection Examples

A
  • Otitis media
  • Sinusitis
  • Bronchitis
  • Pneumonia (CAP)
  • Pneumonia secondary to flu
  • Meningitis
  • Bacteremia
30
Q

Encapsulated Bacteria + Asplenic Patients

A
  • Difficult to clear
  • Lack filtration mechanisms provided by splenic macrophages
  • Risk for fulminant sepsis syndrome
31
Q

Examples of Encapsulated Bacterium

A
  • S. pneumoniae
  • H. influenzae
  • N. meningitidis
32
Q

Enterococci

A
  • Used to be Group D Streptococcus
  • Gamma-hemolysis
  • Gram “+” diplococci or short chains
  • Opportunistic
  • Antibiotic resistance is their best defense
  • Commonly colonize GI and female genital tracts
33
Q

Enterococci Infection Examples

A
  • UTIs
  • Intraabdominal infections
  • Bacteremia
  • Endocarditis
34
Q

Enterococci Bacterium Examples

A
  • E. faecalis: increased prevalence, decreased AMR

- E. faecium: decreased prevalence, increased AMR

35
Q

AMR

A

Antimicrobial resistance

36
Q

Gram “-“ Classifications

A
  • Shape
  • Lactose fermentation
  • Oxidase and H2S production
37
Q

Lactose Fermentation Test

A
  • Grow on MacConkey’s agar

- Turns pink when lactose is fermented

38
Q

Oxidase Assay

A
  • Tests for bacterial cytochrome c oxidases
  • Part of cellular respiration
  • Turns paper blue if the enzyme is present
39
Q

H2S Assay

A
  • Cysteine or thiosulfate in medium

- Utilizes enzymatic action to produce H2S from the medium

40
Q

Gram “-“ Shape Distinctions

A
  • Diplococci
  • Coccobacilli
  • Bacilli
  • Comma-Shapes (all oxidase positive)

Largest group: Rod/bacilli

41
Q

Coccobacilli Bacteria Example

A

-H. influenzae

42
Q

Diplococci Bacteria Examples

A
  • N. meningitidis

- N. gonorrhoeae

43
Q

Bacilli Bacteria Example

A
  • E. coli
  • Klebsiella spp.
  • Proteus spp.
  • S. marcescens
  • Enterobacter spp.
  • Pseudomonas spp.
44
Q

H. influenzae

A
  • No capsule: colonizes URT causing otitis media, sinusitis, CAP
  • Encapsulated: more virulent, not regular colonizer, causes meningitis and sepsis
45
Q

N. meningitidis

A
  • Humans are the only natural host
  • Colonizes oro/nasopharynx
  • Encapsulated
  • Causes meningitis and less commonly PNA
46
Q

N. gonorrhoeae

47
Q

Moraxella Catarrhalis

A
  • Gram “-“ diplococci

- Infections: otitis media, PNA, sinusitis

48
Q

Bordatella Pertussis

A
  • Gram “-“ coccobacillus

- Whooping cough

49
Q

Acinetobacter spp.

A
  • Gram “-“ rods and coccobacillus (depending on growth)
  • Usually encapsulated
  • HA- and CA- infections
  • HIGHLY antibiotic resistant
  • Infections: PNA, bacteremia, wound infections
50
Q

Enterobacteriaceae

A
  • Heterogeneous family of Gram “-“ rods
  • *DON’T CONFUSE WITH ENTEROCOCCI**
  • Normally inhabit intestines of humans/animals
  • Examples: E. coli, Klebsiella spp., Proteus spp., Enterobacter spp., Serratia marcescens, Salmonella enterica, Shigella spp.
51
Q

Pseudomonas spp.

A
  • Gram “-“ rods, non-lactose fermenting, oxidase “+”
  • Highly antibiotic resistant and opportunistic (HA-infections)
  • Increased risks: immunocompromised, broad-spectrum antibiotic use, ventilation equipment
  • Form Biofilms
  • Can be fatal
52
Q

Pseudomonas spp. Infections

A
  • Cystic fibrosis in immunocompromised (P. aeruginosa)
  • Chronic obstructive lung disease
  • Nosocomial infections
  • HAP
  • Febrile neutropenia
  • SSTI (burns, trauma, post-surgical)
  • UTI
53
Q

Spriochete Bacteria

A
  • Treponema pallidum: Gram “+”, causes syphilis

- Borrelia burgdorferi: Gram “-“, causes Lyme disease

54
Q

Clostridium spp.

A
  • Gram “+” anaerobic rods
  • C. difficile: most serious causes of Abx resistant diarrhea
  • C. perfringens: food poisoning, has hangrene
55
Q

Bacteroides fragilis

A
  • Gram “-“ anaerobic rods
  • Colonize gut
  • Usually 0.5% of fecal flora
  • Involved in 90% of anaerobic peritoneal infections
56
Q

Atypical Bacteria

A
  • Live inside hosts
  • Do not gram stain
  • Not normal colonizers
  • Multiply intracellularly
  • Frequent cause of CAP
57
Q

Legionella Pneumophila

A
  • Atypical bacteria
  • Grow inside amoebae in environment
  • Grow inside macrophages in humans
58
Q

Mycoplasma Pneumoniae

A
  • Atypical bacteria
  • No peptidoglycan cell wall
  • Cell membrane contains sterols taken from host serum
  • Can fuse with host cells (intracellular survival)
59
Q

Chlamydia spp.

A
  • Atypical bacteria
  • Obligate intracellular organism
  • C. trachomatis: STD and blindness
  • C. pneumoniae: URTI
60
Q

Cell Walls + Shock

A

Bacterial cell wall lipopolysaccharide is cause of endotoxic shock

  • LPS: endotoxin
  • Cell wall component of Gram “-“ bacteria
  • Endotoxin that causes septic “shock” from inflammatory response
61
Q

Simplified Bacterial Classification

A
  • Gram “+”: Staph., Strept., Entero.
  • Gram “-“: almost everything else for this block
  • Anaerobes: Clostridium, Bacteroides
  • Atypical: Legionella, Mycoplasma, Chlamydia

835 (27 decks)

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