Microbiology/ pharmacology Flashcards
What type of toxins do GPC and GNR have?
GPC have exotoxins, GNR have endotoxins.
What is the treatment for VAP?
VAP treatment is vanc + Cefepime. Add another pseudomonal coverage if high risk for MDR for 7 days.
What is the most common organism in central line infections?
Staph epidermidis is the most common organism in central line infections, staph aureus #2
Also Staph epidermidis:
- MC organism in peritoneal dialysis catheter infection (peritonitis)
- MC organism in AV graft infection
- MC organism MC late AAA graft infection
- MC organism in blood product contamination
What is the most common organism in VAP?
Staph aureus is the most common organism in VAP.
Also staph aureus:
- MC organism in surgical wound infections
- MC organism in osteomyelitis
- MC organism in peritoneal dialysis catheter infection (exit site and tunneled catheter infection) NOT peritonitis
- MCC of lung abscess
- MCC of mycotic aneurysm
- MC organism overall and MC for early (<2 weeks) AAA graft infection
- MC organism in Superficial and suppurative thrombophlebitis
What is the most common organism in intra-abdominal abscess?
The most common organism in intra-abdominal abscess is Enterococcus faecalis (GPC), E. Coli (GNR), and B. Fragilis (anaerobic).
Broad spectrum abx is recommended for intra-abdominal abscesses with: diabetes, sepsis, fever, WBC, cellulitis, any hardware
What should be done in the presence of bacteremia from non-cuffed catheters?
All non-cuffed catheters should be removed.
- bacteremia due to S. aureus, Pseudomonas, or Candida infection and with other access options, we recommend immediate removal of the cuffed catheter and placement of a temporary catheter into another site
- Remove all catheters that have exit site infection or pus
What is the most potent trigger of TNF-alpha in E. coli during gram-negative sepsis?
Endotoxin, specifically Lipid A, is the most potent trigger of TNF-alpha in E. coli.
Necrotizing soft tissue infections
MC polymicrobial
Can present rapidly after surgery (POD 0-2)
Group A beta hemolytic strep pyogenase, staph aureus, clostridium perfringens
Type I = polymicrobial = MC. Staph, strep, pseudomonas, enterococcus, etc
Type II = monomicrobial – two types
1. Monobacterial - #1 MC is Group A Beta hemolytic strep = Strep PYOGENES, Releases exotoxin A + C.
2. Monobacterial - Staph aureus also has exotoxin.
Type III = Clostridium perferingens, vibrio vulnificus (Seafood, boats)
Wound biopsy for type II (monocrobial) will show GPC with paucity of PMNs
Tx: broad spectrum abx until organism identified. Strep pyogenase, or Clostridium Perferingens: high dose PEN G + clindamycin
What is the best method to diagnose osteomyelitis?
MRI is the best to diagnose osteomyelitis.
Staph aureus MC. If cannot get MRI (metal): 3 phase bone scan (Technetium-99). Don’t get bone biopsy in patients with diabetic infections and ulcers: can seed infection into bone
- Tx: abx X 6 weeks and debridement
What is the initial treatment for Clostridium difficile?
Initial treatment for severe or non-severe is oral vanc or fidaxomicin for 10 days.
- Initial recurrence: fidaxomicin (BEST) OR oral vanc pulsed regimen then tapered dose for 21 days
- If fidaxomicin or metronidazole was used then Vancomycin 125 mg orally 4 times daily for 10 days
- Second recurrence: fidaxomicin OR oral vanc as above
- Stool transplant only for third recurrence
- Severe colitis: Oral vanc + IV flagyl.
- Add rectal vanc of patient has ileus
- Fulminant colitis – shock with requirement of pressors OR for subtotal colectomy with end ileostomy
- For active C. diff infection diagnosis: Toxin A or B must be present. (can also be colonized)
- Dx: best is PCR to detect toxin producing genes. MC used. Rapid, sensitive, and high NPP. However, cannot distinguish colonized vs infection. High FP
- Stool culture followed by a test to detect toxin producing gene or toxin itself
- Most sensitive test
- Takes days to complete, not a good test
- ELISA (enzyme immunoassay) for Toxin A and B: Used for decades, now found to be insensitive
What is the recommended treatment for candidemia?
Anidulafungin is the best treatment for candidemia.
Also: micafungin, caspofungin
What is the most common organism found in human bites?
The most common organism is Strep pyogenes, but Eikenella is only found in human bites. Tx: augmentin and tetanus vaccine
What is the recommended treatment for human bite lacerations?
Do not close wounds primarily; they need wash out and heal by secondary intention.
High infection rate.
Risk for Eikenella corrodens Infection
Px abx only given to wounds on hands and face or near a joint
What is the common organism in surgical site infections?
The most common organism in surgical site infections is Staph.
What is the recommended antibiotic for Enterococcus?
The best initial treatment is ampicillin.
Can use vanc. If VRE: linezolid.
What is the significance of peak and trough levels in vancomycin and gentamicin?
Vancomycin: peak should be 20-30, and trough should be 5-10.
Gentamicin: peak 6-10, trough <1
Peak too high: decrease amount of each dosage. (Don’t get peak levels for vanc or aminoglycoside, not recommended)
Trough too high: Increase the length interval between doses
What is the definition of zero-order kinetics?
Zero-order kinetics means a constant amount of drug is eliminated regardless of dose.
-Alcohol is zero order
What is the definition of ED50?
ED50 is the drug level at which the desired effect occurs in 50% of the population.
Skin infection with lymphedema organism
Streptococcus
Hyperglycemia in sepsis and insulin
Hyperglycemia in sepsis: Early: low insulin, high glucose (impaired utilization). Late: high insulin, high glucose, due to insulin resistance
C. Perfringens
C. Perfringens - Clostridium myonecrosis – gas gangrene: Occurs with farming accident.
* Alpha toxin - major source of morbidity and mortality; cytotic to PMNL
* Also theta toxin
-Destruction of healthy muscle and soft tissues; trauma -> vascular compromise= anaerobic environment
SBP in children
MC due to nephrotic syndrome. MC organism is strep pyogenase
Clean wound <2% infection
-primarily closed
- No inflammation, infection, GU, GI, resp tracts are NOT entered
- Mastectomy, hernia, thyroidectomy, vascular bypass, CABG,
Clean contaminated 5-10% infection
Clean contaminated 5-10% infection – controlled entry into tracts: primarily closed
- GU, GI, resp, tracts entered in controlled fashion. No spillage.
- No inflammation!!!!!!!!!!! Nothing acute here. No infection. No acute appy or acue chole.
- Colectomy, biliary colic, urologic procedures, hemorrhoidectomy, appy that is elective non inflamed
Contaminated 10-20% infection
– secondary intention OR delayed primary closure
- Open fresh accidental wounds < 4 hours
- Major break in sterile technique
- Gross spillage of GI content
- Entering GU or biliary tract in presence of infection
- Acute NON-purulent inflammation encountered
- E.g. Acute appendicitis, acute cholecystitis, Diverticulitis, GSW to colon repair, bile spillage
Dirty wound >30% infection
Dirty wound >30% infection – secondary intention
- Perforated viscera prior to operation.
- ABCSESS, pus, Infection.
- Wounds > 4 hours
Elective laparoscopic chole abx
Elective laparoscopic chole does not require preop abx, if no acute chole, no episodes of biliary colic < 30 days, CBD stones, no recent ERCP, no stone or GB spillage.
Open chole all require abx px
Oral carbohydrate loading prior to surgery
Drink carb liquid 2 hours before surgery
decreases insulin resistance
No decrease risk of SSI
Modifiable risk factors that reduce SSI:
Modifiable risk factors that reduce SSI:
- Glycemic control, obesity, smoking, alcohol, prealbumin levels
- A1c does not affect SSI numbers. Only periop glucose levels
Proven to reduce SSI
Proven to reduce SSI
- Cessation of smoking 4-6 weeks before surgery
- Glucose control target 110-150
- Avoid hair removal if have to, use clippers
- Alcohol based prep unless mucosa
- Abx within 1 hour of incision
- Normothermia
- Use wound protectors
- Abx suture – troclosan reduce SSI
- Supplemental oxygen periop
Not been proven to reduce SSI but recommended
- Bathing with chlorhexidine
- All surgical attire
CLABSI
CLABSI – central line infections
- Best is subclavian vein, 2nd is IJ, last is femoral
- Abx impregnated catheters decrease CLABSI rate
- Chlorhexidine impregnant dressings decrease CLABSI rate
- Sutureless retention device should be used decrease CLASBI rate
Viral hepatitis
Hepatitis B, C, and D can cause chronic hepatitis and hepatoma
Hepatitis A, B, C, D+B, and E can cause acute and fulminant hepatitis (very rare with A + C)
Hepatitis A: serious consequences uncommon
Hepatitis B (DNA* only one that is DNA): Anti-HBc-IgM (c=core) elevated in first 6 months, then IgG takes over; vaccination: increased anti-hBs (s=surface) antibodies
Hepatitis C (RNA): can have long incubation period; Tx: Sovaldi (95% cure rate)
Hepatitis D is cofactor for B = these two combined have highest mortality
Hepatitis E = fulminant hepatic failure in pregnancy; most often 3rd trimester
Post exposure prophylaxis HIV:
HAART (Raltegravir + Tenofovir) initiate therapy immediately X 4 weeks. ELISA at time (patient and exposure source) of exposure and at 4 weeks
Candida endophthalmitis
Candida endophthalmitis – liposomal amphotericin
Actinomyces
Not a true fungus, it’s an anaerobe. MC causes abscesses in head and neck. Often has a draining sinus that produces sulfur granules. Tx: penicillin G and drainage
Nocardia
Nocardia– gram positive rod, mimics fungus, branched filamentous morphology, Causes PNA, endocarditis. Tx: bactrim
Brown recluse spider tx
Brown recluse spider tx: Tetanus shot. Don’t give dapsone, not studied. Avoid early surgery
Impetigo, erysipelas, cellulitis, folliculitis MC organism
staph
MCC of infectious proctitis
MCC of infectious proctitis – STD: gonorrhea
Proctitis= inflammation of rectum/ anus
Tetanus wound prophylaxis
Contaminated = dirt, poop, soil, saliva, puncture wounds, avulsions, GSW, crush, burn, frostbite
All burns, frostbite, animal, snake and human bite, feces, saliva, dirt, soil are considered contaminated
Tetanus immunoglobulin – give to contaminated wounds with unknown vaccines or < 3
Flagyl
Flagyl - produces oxygen radicals that break up DNA
Sulfonamides
– has PABA analogue, inhibits purine synthesis
Trimethropin
Trimethropin – inhibits dihydrofolate reductase: inhibits purine synthesis
Bacteriostatic
Bacteriostatic – tetracycline, clindamycin, macrolides, Bactrim
Carbapenems
Carbapenems
-Meropenem, imipenem
-Broad spectrum: GPC, GNR, anaerobes
-Given with cilastatin: prevents renal hydrolysis and increases half-life
-SE: seizures
–Not effective for MEP: MRSA, enterococcus, proteus
Inhibitors of cell wall synthesis
Inhibitors of cell wall synthesis - penicillin, cephalosporins, carbapenems, vanc, monobactam
Inhibit 30S ribosome
Inhibit 30S ribosome - Tetracycline, aminoglycoside
Aminoglycoside: gentamicin, tobramycin
Inhibit 50S ribosome
Inhibit 50S ribosome - macrolides (erythromycin), linezolid, chloramphenicol
Interferes with tRNA complex
clindamycin
Inhibit DNA helicase (DNA Gyrase)
Fluroquinolones
Inhibit RNA polymerase
Rifampin
Length of abx for intra-abdominal infections
4 days after source control (surgery). Not based upon when fever WBC resolves.
1st order
1st order – A constant amount of drug eliminated proportional to dose (Concentration dependent)
- Tylenol is 1st order
half-lives for drug to reach steady state
Takes 5 half-lives for drug to reach steady state
Volume of distribution
Volume of distribution – amount of drug in the body divided by amount of drug in plasma. High Vd have higher concentration in extravascular compartment (Fat tissue) compared with intravascular
LD50
LD50 – drug level at which death occurs in 50%
Drug metabolism
- converts lipophilic compounds to more readily excreted hydrophilic polar water-soluble product
HAART therapy in perioperative period
Should be continued in periooperative period; pausing= incresed viral loads and higher complication rates
