Reuben Notes


  • What should you always consider before starting an antibiotic?
    • What is the most likely infecting organism?
    • Have a gram stain and C&S been done? What are the results?
    • Allergies?
    • Kidney function (check BUN and Cr)?
      • Many antibiotics are renally metabolized
    • What medications is the patient currently taking?
      • Possible drug interactions.

Drug Names

  • Augmentin - amoxacillin/clavulonic acid
    • 500 or 875 mg PO BID
    • 125 mg Clavulonic Acid
    • Indication:
      • PO antibiotic for outpatient therapy of polymicrobial infections
    • Spectrum
      • Staph (not MRSA), Strep, Enterococci, Gram negatives, anaerobes
    • NO Pseudomonas Coverage
  • Zosyn piperacillin/tazobactam
    • 3.375 g IV q6h
    • Indication:
      • Approved for use in adults for the treatment of moderate to severe diabetic foot infections
    • Spectrum
      • Staph (not MRSA), Strep, Enterococci, Gram negatives, anaerobes
      • YES Pseudomonas coverage
  • Unasyn ampicillin/sulbactam
    • 3.0 IV q6h
    • Indication:
      • Empiric therapy for polymicrobial diabetic foot infections
    • Spectrum
      • Staph (not MRSA), Strep, Enterococci, Gram negatives, anaerobes
      • NO Pseudomonas Coverage
  • Zyvox linezolid
  • Invanz ertapenem
  • Cubicin daptomycin
  • Tygacil tigecycline
  • Bactrim trimethoprim/sulfamethoxazole (TMP/SMX)
  • Rocephin ceftriaxone
  • Avelox moxifloxacin
  • Zithromax azithromycin
  • Synercid dalfopristin-quinupristin
  • Timentin ticarcillin/clavulonic acid
    • 3.1 g IV q4-6h
    • Indication:
      • Broad spectrum antibiotic for polymicrobial infections
    • Spectrum:
      • Staph (not MRSA), Strep, Gram negatives, anaerobes
      • YES Pseudomonas coverage
    • Caution:
      • Increased Na+ load (5.2 meq/gram)
  • Primaxim imipenem/cilastatin
  • Cleocin clindamycin
  • Flagyl metronidazole



  • Which cover Pseudomonas?
    • (4th and 5th generations)
    • piperacillin, Zosyn
    • ticarcillin, Timentin
    • carbenicillin, mezlocillin, azlocillin


  • What are IV alternatives for PCN allergic patients?
    • clindamycin, vancomycin, Levaquin, Bactrim


  • How are PNC’s excreted?
    • All are renally excreted except mezlocillin, azlocillin, piperacillin (the ureidopenicillins are 20-30% renal)


  • What concern is there of a patient on both PCN and probenecid?
    • Probenecid will increase duration of serum levels of PCN and most cephalosporins



What is the cross-reactivity of cephalosporins and PCN?

1-10% (depending on whom you talk to)


Are cephalosporins contraindicated for a patient with a PCN allergy?

Many people will say yes, and according to Dr. Warren Joseph, "Cephalosporins should be

avoided entirely in patients with a history of anaphylaxis to penicillin." However, he states that

if there is a questionable allergy history (rash or upset stomach), "Cephalosporins can be used

with little worry." Personally, I will give a cephalosporin to a patient with a PCN allergy if all

he or she had was an upset stomach and I document this.


How to treat serious hospital acquired Gram negative infections?

3rd generation cephalosporins, aminoglycoside (i.e. Rocephin, gentamycin)


What is the coverage of cephalosporins for each class?

  • 1st Generation
    • Gram positive – Staph (not MRSA) and Strep
    • Gram negative – Proteus, E. coli, Klebsiella, Salmonella, Shigella (PECKSS)
    • Anaerobes – not Bacteroides
  • 2nd Generation
    • Gram positive – similar to 1st gen
    • Gram negative – more coverage, H. influenza, Neisseria, Proteus, E. coli, Klebsiella,
    • Salmonella, Shigella (HEN PECKSS)
  • 3rd Generation
    • Gram positive – less than 1st and 2nd gen
    • Gram negative – expanded coverage, ceftazadime covers Pseudomonas
  • 4th Generation
    • Gram positive – similar to 1st gen
    • Gram negative – similar to 3rd gen, including Pseudomonas
    • No anaerobic coverage


Name a couple cephalosporins for each generation

  • 1st Generation – cefazolin (Ancef), cephalexin (Keflex)
  • 2nd Generation – cefaclor (Ceclor), cefuroxime (Ceftin)
  • 3rd Generation – ceftriaxone (Rocephin), ceftazidime (Fortaz), cefdinir (Omnicef)
  • 4th Generation – cefepime (Maxipime)


How are they excreted?

Renally except for ceftriaxone (renal/hepatic) and cefoperazone (hepatic)



What is the main indication?



What is its spectrum of activity?

All Gram positives, including MRSA and MRSE


What is the dose?

1 g IV q12h with slow infusion


When are levels drawn?

Peak taken 30 min after the 3rd dose

Trough taken 30 min before the 4th dose


What should the peaks and troughs be?

Peak 15-30 mg/mL

Trough <10 mg/mL


How do you adjust the dose?

If the peak is too high, decrease the dose

If the peak is too low, increase the dose

If the trough is too high, increase the interval between doses

If the trough is too low, decrease the interval between doses


What happens when you infuse too quickly?

Red Man syndrome – erythema and pruritis to the head, neck, and upper torso. It is caused by an

anaphylactoid reaction where histamine is released by mast cells. (A different Red Man

syndrome is associated with excessive Rifampin that causes a bright reddish-orange

pigmentation of the skin.)


How can you decrease the risks of Red Man syndrome?

Slow infusion over one hour


How do you treat Red Man syndrome?

Antihistamines (Benadryl 25-50 mg IV q2-4h) until symptoms resolve

Symptoms are self-limiting


What are other side effects?

Ototoxicity and nephrotoxicity

Does the duration a patient has been on vancomycin increase the risks of side effects?

Yes. Vancomycin has a reservoir effect: the more often a patient receives vancomycin, the

higher the chance of getting either ototoxicity or nephrotoxicity. Therefore, use vancomycin

carefully; it is a powerful drug with severe side effects.


When should PO vancomycin be used?

Treatment of Pseudomembranous colitis (125 mg PO q6h)



What is the dose?

One tab PO BID


How much is in the single strength tablet? Double strength?

Single strength – TMP 80 mg / SMX 400 mg

Double strength (DS) – TMP 160 mg / SMX 800 mg


How does it work?

Trimethoprim and sulfamethoxazole inhibit folate synthesis in bacteria which prevents DNA



What is the spectrum of activity?

Broad spectrum covering Gram positives (MRSA) and Gram negatives


Does it cover Pseudomonas?



What allergy should be avoided?



What are the side effects?

Hemolytic anemia, hypersensitivity


What are the contraindications?

Patient on oral hypoglycemic or with G6PD deficiencies



  • Dose:
    • 250 mg PO, two tabs on the first day then one tab for the next four days
  • Spectrum
    • Staph, Strep, and some anaerobes (but not bacteroides)
  • Ok with PCN Allergy - YES
  • Half-Life: 68 hours



  • Dose:
    • 500 mg IV q6-8h (most common) or 1 gm IV q6-8h
  • Spectrum
    • Very broad spectrum including most Gram positive, Gram negative, and most anaerobes
    • NO MRSA
    • NO Pseudomonas
  • Side effects
    • Seizure in patients with history of seizures
      • 1% risk with 500 mg dose, 10% risk with 1 g dose
  • Mechanism
    • imipenem – antibiotic
      • imipenem nicknamed "Gorillamycin" because of its very broad of spectrum activity
    • cilastatin – renal dehydropeptidase inhibitor, which prevents imipenem from being metabolized by the kidneys



  • Dose:
    • 1 g IV q24h
  • Indications
    • Approved for use in adults for the treatment of moderate to severe diabetic foot infections
  • Spectrum
    • Gram positive, Gram negative, and anaerobes
  • NO Pseudomonas Coverage
  • Class
    • It is a structurally unique 1-β-methyl-carbapenem related to β-lactams



  • Dose:
    • 400-600 mg PO/IV q12h
  • Indications
    • Oral Zyvox may be used for outpatient treatment of MRSA infections
  • Spectrum
    • All Gram positives, including MRSA and VRE
  • Side Effects
    • Thrombocytopenia (check CBC)
  • Expensive - can prohibit use



  • Common Quinolones
    • Ciprofloxacin
      • 250-750 mg PO q12h
      • 200-400 mg IV q12h
    • Levaquin
      • 250-500 mg PO/IV q24h
    • Avelox
      • 400 mg PO/IV q24h
  • Spectrum
    • Gram negative, including Pseudomonas
    • YES Pseudomonas
    • Cipro – limited Gram positive
    • Levaquin and Avelox – better Gram positive
  • Side Effects
    • Tendonitis and tendon ruptures
  • Contraindicated
    • children with open growth plates. Risk of cartilage degeneration.



  • Dose
    • 1-2 g IV q8h
  • Spectrum
    • Gram negative aerobes and pseudomonas (its main indication)
  • Side Effects
    • None
  • Expensive - May prohibit use



What are some major aminoglycosides?

Gentamycin, Tobramycin, Amikacin


What is the spectrum of activity?

Gram negative aerobes


What are the side effects?

Ototoxicity – irreversible

Nephrotoxicity – reversible

Neuromuscular blockade – prevented by slow infusion


What are the doses, peaks, and troughs?

                                            Dose                           Peak (μg/mL)         Trough (μg/mL)

Gent and Tobramycin            3-5 mg/kg q8h                  6-10                     2

Amikacin                               15 mg/kg q8h                    20-30                 <10


How to dose gentamycin?

  • Loading dose is 2 mg/kg for Gent and Tobra (7.5 mg/kg for Amikacin)
  • Determine creatinine clearance (CC)

               CC = (140 - Age) x Weight (in kg)

                        72 x Serum Creatinine

               For females, multiply the CC by 0.85

  • Maintenance dose is adjusted for CC (e.g. If the CC is 0.75, then the patient has 75% kidney function. Give 75% of a normal dose.)



  • Dose
    • 600-900 mg IV q8h or 150-300 mg PO BID
  • Spectrum
    • Most Gram positive and most anaerobes
  • Side Effect
    • Pseudomembranous colitis
  • Metabolized
    • Liver



  • Dose
    • 500 mg PO TID
  • Spectrum
    • Some Gram positive anaerobes and most Gram negative anaerobes



What antibiotics cover MRSA?

PO – linezolid, Minocycline, Cipro/rifampin, Bactrim/rifampin

IV – vancomycin, linezolid, minocycline, Cipro/rifampin, Bactrim/rifampin, Synercid,

tigecyclin, telavancin

Topical – Bactroban


What are the only FDA-approved drugs for treating MRSA?





telavancin (Vibativ)



How do you treat VRE?

linezolid or dalfopristin-quinupristin


What is the only PO therapy for VRE?




What drugs cover Pseudomonas?

  • Aztreonam
  • Aminoglycosides – gentamycin, tobramycin, amikacin
  • Cipro
  • Ceftazidime, cefepime
  • Timentin
  • Zosyn


Polymicrobial Infections

What are some empiric therapies for polymicrobial foot infections?

Vanco/Zosyn, Clinda/Cipro, Vanco/Invanz


What are the only FDA-approved drugs for treating diabetic foot infections?

(The 3 Z’s)





Antibiotic-Associated Diarrhea

What are two main causes of antibiotic-associated diarrhea?

Pseudomembranous colitis – Clostridium difficile

Non-specific colitis – Staph aureus


How to you test for Clostridium difficile?

Order ―check stool for C diff‖


What is the most common cause of Clostridium difficile colitis?

clindamycin (though any antibiotic can cause it)


How do you treat Clostridium difficile colitis?

Vanco 125 mg PO q6h

Flagyl 500 mg PO TID



What antibiotics are metabolized by the liver?

  • (3 C’s and 1 E)
  • Clindamycin
  • Cefoperazone
  • Chloramphenicol
  • Erythromycin


Can antibiotics affect PT/INR?

Yes. Antibiotics can affect normal flora, which alters Vitamin K. Therefore, the PT/INR can



What can β-lactams cause?



What is the MOA of aminoglycosides? Macrolides?

Aminoglycosides bind to bacterial 30s ribosomes inhibiting protein synthesis

Macrolides bind to bacterial 50s ribosomes inhibiting protein synthesis

(A boy at 30 does not become a Man until 50)


What antibiotics can be safely used with PMMA beads?

Vancomycin, gentamycin, tobramycin, cefazolin

The curing of PMMA is exothermic, therefore the antibiotic must be not be heat-labile


What open fractures should be treated with antibiotics?

Grades 2 and 3


Bugs and Drugs

Gram Positives

What are Gram positive, catalase positive cocci in clusters?

Staphylococcus aureus


DOC for Staph?

Keflex or Ancef


Alternative for Staph?

clindamycin, Levaquin, Vancomycin, Azithromycin, dicloxacillin, nafcillin


Alternative for Staph if PCN allergy?

clindamycin, Levaquin, Vancomycin, Azithromycin


What if the organism is resistant to methicillin?

MRSA (methacillin-resistant Staph aureus)



Vanco IV, Bactrim PO (if sensitive)


Alternative for MRSA?

Synercid or linezolid


Topical DOC for MRSA?



DOC for Strep?

Keflex or Ancef


What are Gram positive, catalase negative cocci that are in pairs or chains?



DOC for Strep?

Keflex or Ancef


Alternative for Strep?

clindamycin, Levaquin, vancomycin


Alternative for Strep in PCN allergy?

clindamycin, Levaquin, vancomycin


DOC for Enterococcus?

amoxicillin or vancomycin


Alternative for Enterococcus?

Augmentin, linezolid


What if the organism is resistant to vancomycin?

VRE (vancomycin-resistant Enterococcus)


DOC for VRE?

linezolid or Synercid


DOC for Diptheroids?



Gram Negatives

What is a short, Gram negative rod?

Escherichia coli


DOC for E. coli?

Keflex or Ancef


Alternative for E. coli if PCN allergy?

Cipro or Levaquin


DOC for Proteus?

Keflex or ampicillin

Alternatives for Proteus if PCN allergy?

Cipro or Levaquin

DOC for E/C/S/M group?

Quinolone (Cipro or Levaquin)

Alternatives for E/C/S/M group?

3rd generation cephalosporin, Aztreonam, Bactrim

What is a small Gram negative rod with pili and polar flagella?

Pseudomonas aeruginosa

DOC for Pseudomonas?


Alternative for Pseudomonas?

3rd gen cephalosporins, Aztreonam, Zosyn, Timentin


How does Pseudomonas typically present?

blue-green purulence with grape-like odor


What Gram negative spirochete causes Lyme disease?

Borrelia burgdorferi


DOC for Lyme disease?

doxycyline or Rocephin


Alternative for Lyme disease?




DOC for Bacteroides?

Augmentin, Zosyn, Unasyn, Timentin


Alternatives for Bacteroides if PCN allergy?

clindamycin/Cipro, Primaxin, Flagyl


What is a large, Gram positive, anaerobic, "racquet-shaped" rod that forms spores?

Clostridium perfringens


DOC for Clostridium?

Penicillin, imipenem, clindamycin, tetracycline


What are two soft tissue clinical manifestations caused by Clostridium?

Anaerobic cellulitis and gas gangrene


Why is gas gangrene a surgical emergency?

It rapidly progresses to shock and renal failure and is fatal in 30% of cases


Less Common Organisims

DOC for Aeromonas?

Cipro PO/IV


Alternative for Aeromonas?



DOC for Pseudomonas cepacia?



Alternative for Pseudomonas cepacia?



DOC for Necrotizing Fasciitis?



DOC for superficial thrombophlebitis?



DOC for Gonorrhea?

Ceftriaxone or PCN if sensitive


DOC of Cutaneous Larva Migrans?

Promethia under occlusion



What organisms may form gas in soft tissue?

Gram positive – Clostridium perfringens, Staphylococcus, Streptococcus, Peptostreptococcus

Gram negative – Bacteroides, E. coli, Klebsiella, Serratia


What are some anaerobes?

Gram positive – Actinomyces, Clostridium, Peptostreptococcus

Gram negative – Bacteroides, Fusobacterium


What is the drug of choice (DOC) for a patient with diabetes and a PCN allergy?



DOC for severe limb-threatening infection?



What are most common organisms of bite wounds?

Human – Eikenella corrodens

Cat and dog – Pasteurella multocida


What is Gram negative rod is associated with dog bites?



DOC for cat and dog bites?



What are the most common organisms causing cellulitis?

Staph and Strep


Which type of Strep can cause impetigo, cellulitis, and erysipelas?

Group A Strep


What is the difference between cellulitis and erysipelas?

Cellulitis – confined superficial infection

Erysipelas – superficial infection that extends into the lymphatics


What is the most common organism that causes acute hematogenous osteomyelitis?

Staphylococcus aureus (adults), Gram negative rods (elderly)


What is the most common organism that causes osteomyelitis following a puncture wound?

Pseudomonas aeruginosa


What is an anaerobic Gram positive filamentous bacteria?



What organism may be found following a puncture wound in the ocean?

Vibrio vulnificus


What type of bacteria is gonorrhea?

Gram negative diplococci


What is gonorrhea cultured on?

Chocolate agar


What is the treatment for gonorrhea?



If a patient is currently on an antibiotic, how long should it be stopped before taking a wound culture?

At least 48 hours (if possible)