835 > Bacterial Pathogens > Flashcards

Bacterial Pathogens Flashcards

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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
Group B S. Agalacitae Infection Example
Neonatal meningitis
26
Viridans Streptococci Infection Examples
- Dental caries | - Bacteremia/endocarditis in immunocompromised
27
Streptococcus Pneumoniae
- One of the most common causers of URTI - Alpha hemolytic - Gram "+" diplococci - Polysaccharide capsule is target for vaccine
28
URTI
Upper respiratory tract infection
29
Streptococcus Pneumoniae Infection Examples
- Otitis media - Sinusitis - Bronchitis - Pneumonia (CAP) - Pneumonia secondary to flu - Meningitis - Bacteremia
30
Encapsulated Bacteria + Asplenic Patients
- Difficult to clear - Lack filtration mechanisms provided by splenic macrophages - Risk for fulminant sepsis syndrome
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Examples of Encapsulated Bacterium
- S. pneumoniae - H. influenzae - N. meningitidis
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Enterococci
- 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
Enterococci Infection Examples
- UTIs - Intraabdominal infections - Bacteremia - Endocarditis
34
Enterococci Bacterium Examples
- E. faecalis: increased prevalence, decreased AMR | - E. faecium: decreased prevalence, increased AMR
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AMR
Antimicrobial resistance
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Gram "-" Classifications
- Shape - Lactose fermentation - Oxidase and H2S production
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Lactose Fermentation Test
- Grow on MacConkey's agar | - Turns pink when lactose is fermented
38
Oxidase Assay
- Tests for bacterial cytochrome c oxidases - Part of cellular respiration - Turns paper blue if the enzyme is present
39
H2S Assay
- Cysteine or thiosulfate in medium | - Utilizes enzymatic action to produce H2S from the medium
40
Gram "-" Shape Distinctions
- Diplococci - Coccobacilli - Bacilli - Comma-Shapes (all oxidase positive) **Largest group: Rod/bacilli**
41
Coccobacilli Bacteria Example
-H. influenzae
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Diplococci Bacteria Examples
- N. meningitidis | - N. gonorrhoeae
43
Bacilli Bacteria Example
- E. coli - Klebsiella spp. - Proteus spp. - S. marcescens - Enterobacter spp. - Pseudomonas spp.
44
H. influenzae
- No capsule: colonizes URT causing otitis media, sinusitis, CAP - Encapsulated: more virulent, not regular colonizer, causes meningitis and sepsis
45
N. meningitidis
- Humans are the only natural host - Colonizes oro/nasopharynx - Encapsulated - Causes meningitis and less commonly PNA
46
N. gonorrhoeae
-STD
47
Moraxella Catarrhalis
- Gram "-" diplococci | - Infections: otitis media, PNA, sinusitis
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Bordatella Pertussis
- Gram "-" coccobacillus | - Whooping cough
49
Acinetobacter spp.
- Gram "-" rods and coccobacillus (depending on growth) - Usually encapsulated - HA- and CA- infections - HIGHLY antibiotic resistant - Infections: PNA, bacteremia, wound infections
50
Enterobacteriaceae
- 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
Pseudomonas spp.
- 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
Pseudomonas spp. Infections
- Cystic fibrosis in immunocompromised (P. aeruginosa) - Chronic obstructive lung disease - Nosocomial infections - HAP - Febrile neutropenia - SSTI (burns, trauma, post-surgical) - UTI
53
Spriochete Bacteria
- Treponema pallidum: Gram "+", causes syphilis | - Borrelia burgdorferi: Gram "-", causes Lyme disease
54
Clostridium spp.
- Gram "+" anaerobic rods - C. difficile: most serious causes of Abx resistant diarrhea - C. perfringens: food poisoning, has hangrene
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Bacteroides fragilis
- Gram "-" anaerobic rods - Colonize gut - Usually 0.5% of fecal flora - Involved in 90% of anaerobic peritoneal infections
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Atypical Bacteria
- Live inside hosts - Do not gram stain - Not normal colonizers - Multiply intracellularly - Frequent cause of CAP
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Legionella Pneumophila
- Atypical bacteria - Grow inside amoebae in environment - Grow inside macrophages in humans
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Mycoplasma Pneumoniae
- Atypical bacteria - No peptidoglycan cell wall - Cell membrane contains sterols taken from host serum - Can fuse with host cells (intracellular survival)
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Chlamydia spp.
- Atypical bacteria - Obligate intracellular organism - C. trachomatis: STD and blindness - C. pneumoniae: URTI
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Cell Walls + Shock
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
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Simplified Bacterial Classification
- Gram "+": Staph., Strept., Entero. - Gram "-": almost everything else for this block - Anaerobes: Clostridium, Bacteroides - Atypical: Legionella, Mycoplasma, Chlamydia
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