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Flashcards in Pharmacology-Antibiotic Resistance Deck (13)
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What drugs are effective against MDR pseudomonas?

Carbapenems and aminoglycosides. It is resistant to cephalosporins, beta lactams and fluoroquinolones


Central line nosocomial infection

MRSA and Candida


Cather-associated UTI

ESBL E. coli


Ventilator-associated pneumonia

MDR gram negatives like pseudomonas and MRSA


Antibiotic-associated diarrhea

C. diff


A 25 year old with multiple surgeries develops fever, chills, elevated WBC w/left shift and fluid collection on CT. Gram stain shows gram-negative rods that ferment lactose on MacConkey agar. The lab tells you it produced an extended-spectrum beta-lactamase (ESBL). What is the most likely organism? How do you treat it?

E. coli. ESBL is also produced in Klebsiella species. These bugs are resistant to penicillins, cephalosporins and monobactams. These are becoming increasingly resistant to fluoroquinolones, aminoglycosides and TMP-SMX so therapy is restricted to carbapenems (imipenem and ertapenem).


A 60 year old woman had knee replacement surgery. She gets a UTI post-op and is admitted to the ICU for 2 days. She improves, but on hospital day 7, she develops fever and respiratory distress. Respiratory culture grows a gram-negative, lactose-fermenting mucoid bacteria. The lab tells you it produces carbapenemase. What is your diagnosis? How do you treat her?

She has carbapenem-resistant enterobacteriaceae, specifically Klebsiella, but it could also be E. coli. These bugs are resistant to penicillins, cephalosporins, monobactams and carbapenems. These are also resistant to fluoroquinolones, aminoglycosides and TMP-SMX. The only treatment option is colistin, which has lots of toxicities. 


What is concerning about bacteria that produce carbapenemases and ESBLs?

They are plasmid associated and can be transferred between bacterium.


A 60 year old woman is admitted to the hospital for pyelonephritis complicated by E. coli bacteremia. She is given IV ciprofloxacin. On hospital day 7 she develops watery diarrhea, cramping abdominal pain, fever and leukocytosis. Stool culture reveals a gram-positive bacillus and PCR shows toxin-forming genes. Sigmoidoscopy shows pseudomembranous colitis. What is your diagnosis and what are risk factors for this bug? How do you treat her?

Clostridium difficile, toxins A and B mediate diarrhea and colitis. Risk factors include antibiotic exposure (especially fluoroquinolones and clindamycin), hospitalization, old age, PPIs and recent GI surgery. Never give her anti-motility drugs like loperamide. Correct electrolytes and fluid. Give fidaxomicin, oral/enema vancomycin, IV metronidazol and consider fecal transplant.


Worst presentation of C. diff infection?

Fulminant colitis. Note that this may present with ileus and toxic megacolon instead of diarrhea.


Why do you wash your hands when seeing a patient with C. diff infection?

Spores can be alcohol resistant


A 24 year old man returns from Iraq and develops fever and rising inflammatory markers on hospital day 14 after surgery. CT shows fluid collection in the leg adjacent to the femur. His wounds grow a non-lactose fermenting pleomorphic gram-negative rod. What is the most likely organism and how do you treat it?

MDR acinetobacter baumannii. This can manifest as nosocomial pneumonia, bacteremia, wound infection and UTIs. It is treated with colistin, aminoglycosides or sulbactam, all which have significant nephro, oto and neurotoxicities.


A 24 year old man recently returned from Afghanistan and describes a “spider bite” on his knee. He denies fever or chills. Wound culture grows a beta hemolytic gram positive cocci in clusters. The lab tells you the bacteria are methicillin resistant. What drugs are used to treat this infection?

1st line is vancomycin.