Principles of ID and Antibacterial Classes

Question 1

Presence of Infection and Abx Selection

Answer 1

Infection Signs
-Fever, elevated WBC
-Site-specific sx (dysuria with UTIs ex)
-Culture results, inflammation markers, X-rays

Abx Selection
-Infection site and likely organisms
-Infection severity and risk of MDR pathogens
-Spectrum of activity, ability to penetrate the site of infection
-Pt factors: age, body weight, renal/hepatic function, colonization, recent abx use, allergies

Question 2

CNS/Meningitis: Common Pathogens

Answer 2

-Streptococcus pneumoniae
-Neisseria meningitidis
-Haemophilus influenzae
-Group B Streptococcus/E. coli (young)
-Listeria (young/old)

Question 3

Upper Respiratory: Common Pathogens

Answer 3

-Streptococcus pyogenes
-Streptococcus pneumoniae
-Haemophilus influenzae
-Moraxella catarrhalis

Question 4

Heart/Endocarditis: Common Pathogens

Answer 4

-Staphylococcus aureus, including MRSA
-Staphylococcus epidermidis
-Streptococci
-Enterococci

Question 5

Mouth: Common Pathogens

Answer 5

-Mouth flora (Peptostreptococcus)
-Anaerobic GNR (Prevatella)
-Viridans group streptococi

Question 6

Lower Respiratory: Common Pathogens

Answer 6

Community
-Streptococcus pneumoniae
-Haemophilus influenzae
-Atypicals: Legionella, Mycoplasma, Chlamydophila
-Enteric GNR (alcohol use disorder) (Proteus, E. coli, Klebsiella, Enterobacter, Serratia)

Hospital
-Staphylococcus aureus, including MRSA
-Pseudomonas aeruginosa
-Acinetobacter baumanni
-Enteric GNR (including ESBL+, MDR) (Proteus, E. coli, Klebsiella, Enterobacter, Serratia)
-Streptococcus pneumoniae

Question 7

Intra-abdominal: Common Pathogens

Answer 7

-Enteric GNR (Proteus, E. coli, Klebsiella, Enterobacter, Serratia)
-Enterococci
-Streptococci
-Bacteroides species

Question 8

Skin/Soft Tissue: Common Pathogens

Answer 8

-Staphylococcus aureus
-Staphylococcus epidermidis
-Streptococcus pyogenes
-Pasteurella multocida + aerobic/anaerobic GNR (in diabetes)

Question 9

Bone/Joint: Common Pathogens

Answer 9

-Staphylococcus aureus
-Staphylococcus epidermidis
-Streptococci
-Neisseria gonorrhoeae
-GNR (in specific situations)

Question 10

Urinary Tract: Common Pathogens

Answer 10

-E. coli
-Proteus
-Klebsiella
-Staphylococcus saprophyticus
-Enterococci

Question 11

Empiric Treatment

Answer 11

-Fluid/tissue sample sent to lab for Gram stain, culture, susceptibility testing
-Abx started while awaiting results (before pathogen is identified)
-Empiric tx is usually broad-spectrum and guided by local resistance patterns (antibiograms)

Question 12

Antibiograms

Answer 12

Bug listed vertically, drug listed horizonatally

inside represent the % of samples of each isolated organism that were susceptible to the listed drug

Question 13

Gram Stains

Answer 13

Gram + = thick cell wall, dark purple/blue (from crystal violet stain)

Gram - = thin cell wall, pink (from safranin)

Atypical = no cell wall, do not stain well

Question 14

Gram + RODS (BACILLI)

Answer 14

-Listeria monocytogenes
-Corynebacterium spp

Question 15

Gram + ANAEROBES

Answer 15

-Peptostreptococcus
-Propionibacterium acnes
-Clostridioides difficile
-Clostridium spp

Question 16

Gram + COCCI CLUSTERS

Answer 16

-Staphylococcus spp. including MSSA,
MRSA

Question 17

Gram + COCCI PAIRS/CHAINS

Answer 17

-Streptococcus pneumoniae (diplococci - pairs)
-Streptococcus spp. (including pyogenes)
-Enterococcus spp. (including VRE)

Question 18

Atypicals

Answer 18

-Chlamydia spp.
-Legionella spp.
-Mycoplasma pneumoniae
-Mycobacterium tuberculosis

Question 19

Gram - ANAEROBES

Answer 19

-Bacteroides fragilis
-Prevotella spp.

Question 20

Gram - COCCI

Answer 20

-Neisseria spp.

Question 21

Gram - COCCOBACILLI

Answer 21

-Acinetobacter baumannii
-Bordetella pertussis
-Moraxella catamhalis

Question 22

Gram - RODS (ENTERIC/GUT)

Answer 22

-Proteus mirabilis
-Escherichia coli
-Klebsiella spp.
-Serratia spp.
-Enterobacter cloacoe
-Citrobacter spp.

Question 23

Gram - RODS (NON GUT)

Answer 23

-Pseudomonas aeruginosa
-Haemophilus influenza
-Providencia spp.

Question 24

Gram - CURVED/SPIRAL

Answer 24

-H. pylori
-Campylobacter spp.
-Treponema spp.
-Borrelia spp.
-Leptospira spp.

Question 25

Staphylococcus aureus

Answer 25

Is coagulase positive (others like epidermidis are referred to as coagulase negative)

Question 26

Synergy

Answer 26

Effect of 2 abx can be additive like aminoglycosides and beta-lactams can be used to treat certain invasive gram + infections (infective endocarditis) -BL breaks down cell wall allowing AG to reach intracellular target at safe doses

Question 27

Abx Resistance

Answer 27

Mechanisms: -Intrinsic (resistance is natural to bug) -Selection pressure (abx kills sus bugs leaving more resistant bugs to multiply) -Acquired (DNA resistant genes can be transferred between species/picked up from dead fragments) -Abx degradation (enzymes break down abx)

Question 28

Common Resistant Pathogens

Answer 28

-Kiebsiella pneumonice (ESBL, CRE) -Escherichia coli (ESBL, CRE) -Acinetobacter baumannif -Enterococcus faecolis, Enterococcus faecium (VRE) -Staphylococcus aureus (MRSA) -Pseudomonas aeruginosa Remember: Kill Each And Every Strong Pathogen

Question 29

C. diff (Clostridioides difficile)

Answer 29

All abx have a warning for C. diff Risk is highest with -PCNs -Cephalosporins -Quinolones -Carbapenems -Clindamycin*** (BBW)