15 Urinary Tract Infections

Question 1

Epidemiology of UTIs

• Antibiotic prescriptions
• Most infections
• Men vs. women
• Relative frequency of nosocomial (hospital-acquired) infections

Answer 1

• Antibiotic prescriptions
  
  • 2nd most common cause for antibiotic prescription after URIs
• Most infections
  
  • Limited to the lower urinary tract (bladder only)
• Men vs. women
  
  • 30x more common in young women than young men
    
    • 50% of women have _>_1 UTi by age 32
  • Incidence rises in men after age 50
• Relative frequency of nosocomial (hospital-acquired) infections
  
  • Urinary tract: 34%
  • Other: 21%
  • Surgical wound: 17%
  • Bloodstream: 14%
  • Pneumonia: 13%

Question 2

Pathogenesis of UTIs

• Ascending route
• Hematogenous
• Direct

Answer 2

• Ascending route (most common (95%))
  
  • Via the urethra
  • E. coli
• Hematogenous (rare)
  
  • Blood –> kidney –> bladder
  • Endocarditis (S. aureus), TB
• Direct (rare)
  
  • Connection or fistula b/n bowl & bladder
  • Passing air/gas through urethra
  • Urine culture w/ pus & multiple organisms (polymicrobial)

Question 3

Bacterial factors promoting risk of UTIs

Answer 3

• Colonization
• Adherence factors of bacteria
  
  • E. coli spp adhere to urothelial cells
  • Proteus spp adhere to lumen of catheter material
• Inoculum size
  
  • Stasis of urine increases inoculum
• Virulence of the bacteria
  
  • Low: Enterococcus / Candida
  • High: E. coli

Question 4

Host defense mechanisms decreasing risk of UTIs

• Mechanical
• Interference
• Chemical
• Immune mechanisms

Answer 4

• Mechanical
  
  • Dilution & flow of urine
  • Length of urethra (female tract is shorter than the male tract)
• Interference
  
  • Normal bacterial flora (meatus) prevents overgrowth pathogenic flora
• Chemical
  
  • Osmolality & pH of urine
  • Prostatic fluid
• Immune mechanisms
  
  • Anti-adherence mechanisms
  • Mucosal antibacterial activity
  • IgA & antibacteiral proteins secreted in urine

Question 5

Clinical risk factors for developing UTIs

• Alteration of colonizing bacteria
• Retrograde introduction of bacteria
• Urinary stasis
  
  • Neurogenic bladder
  • Reflux into ureters
  • Obstruction
• Nutrients
• Foreign materials

Answer 5

• Alteration of colonizing bacteria
  
  • Antibiotics, spermicides
  • Vaginal atrophy (postmenopausal)
• Retrograde introduction of bacteria
  
  • Vaginal sex (translocation of vaginal flroa into female urethra)
  • Insertive rectal sex (translocation of GI bacteria into male urethra)
  • Inserting items in urethra (catheters or sex toys)
• Urinary stasis
  
  • Neurogenic bladder
    
    • Diabetes mellitus
    • Multiple sclerosis
    • Paraplegia
  • Reflux into ureters
    
    • Congenital anatomical abnormalities
    • Pregnancy (hormonal influence)
  • Obstruction
    
    • Stones, tumor
    • Pregnancy (compression from gravid uterus)
    • Prostate hypertrophy (age)
• Nutrients
  
  • Glycosuria (Diabetes mellitus)
• Foreign materials
  
  • Aid in colonization by promoting adherent surfaces
  • Stones, stents, catheters

Question 6

Types & definitions of urinary tract problems

• Uncomplicated
• Complicated

Answer 6

• Uncomplicated
  
  • Asymptomatic bacteriuria
  • Dysuria
    
    • Vaginitis
    • Urethritis
    • Cystitis
  • Cystitis
  • Uncomplicated pyelonephritis
• Complicated
  
  • Complicated UTIs
  • Special problems / other

Question 7

Types & definitions of urinary tract problems: uncomplicated

• Asymptomatic bacteriuria
• Dysuria
  
  • Vaginitis
  • Urethritis
  • Cystitis
• Cystitis
• Uncomplicated pyelonephritis

Answer 7

• Asymptomatic bacteriuria
  
  • Isolation of _>_10² cfu/ml in an appropriately collected urine specimen from a pt w/o symptoms or signs of a UTI
• Dysuria
  
  • Discomfort when voiding / burning sensation
  • Vaginitis
    
    • Bacteria < 10² cfu/ml & absence of pyuria
    • Atrophy of vaginal tissues (postmenopausal)
    • Candida (overgrowth)
      
      • Risk factors: antibiotic exposure, DM, & HIV
    • Trichomonas (STI)
  • Urethritis
    
    • Pyuria due to inflammation of the urethra
    • Chlamydia, Ureoplasma
    • Neisseria gonorrhoeae
  • Cystitis
    
    • Bacteria > 10^2-5 cfu/ml & pyuria
• Cystitis
  
  • Symptomatic bladder infection
  • Frequency, urgency, dysuria, or suprapubic pain
    
    • Any symptom: >50% predictive cystitis
    • Dysuria & frequency w/o discharge: >90%
  • Aka acute uncomplicated cystitis in women w/ normal genitourinary tracts
  • Aka complicated cystitis in recurrent cystitis & cystitis in non-healthy women
• Uncomplicated pyelonephritis
  
  • Renal tissue infection
  • Flank pain, costovertebral angle tenderness, fever, pyuria, nausea/vomiting, & 2^o bacteremia (sometimes)
  • Acute non-obstructive pyelonephritis in healthy women

Question 8

Types & definitions of urinary tract problems: complicated

• Complicated UTIs
• Special problems / other

Answer 8

• Complicated UTIs
  
  • Anything other than uncomplicated pyelonephritis
  • Symptomatic UTIs in pts w/ functional or structural urinary tract abnormalities
  • May involve the bladder or kidneys
  • Ex. UTIs in men, pregnant women, & children
  • Include prostatitis & pyelonephritis in non-healthy women
• Special problems / other
  
  • Catheter associated asymptomatic bacteriuria
  • Catheter-associated UTI
  • Prostatitis
  • Candida in urine
  • Sterile pyuria caused by Mycobacterium tuberculosis

Question 9

Urinalysis

• Microscopy
• Dipstick
• Leukocyte esterase (LE)
• Urinary nitrite

Answer 9

• Microscopy
  
  • WBCs & gram stain
• Dipstick
  
  • 75% sensitive, 82% specific
• Leukocyte esterase (LE)
  
  • Rapid screening test ofr detecting pyuria
  • Pts w/ symptoms & negative LE should have a urine microscopic exam for pyuria
• Urinary nitrite
  
  • Formed when bacteria (Proteus, Providencia, Pseudomonas, Klebsiella) reduce the nitrate that’s normally found in the urine
  • False negatives common
  • False positives rare

Question 10

Microbiology evaluation (culture)

• Types of cultures
• Bladder vs. distal urethra urine
• True UTIs are accompanied by…
• Don’t culture urine unless…

Answer 10

• Types of cultures
  
  • Quantitative culture
  • Specialized cultures (TB, fungi)
  • Antigen detection (Histoplasma)
• Bladder vs. distal urethra urine
  
  • Bladder urine: sterile
  • Distal urethra urine: not sterile
• True UTIs are accompanied by…
  
  • Symptoms
  • Pyuria
    
    • >10 leukocytes/mm³ of uncentrifuged urine
    • Higher threshold if catheter is in place
  • Lack of epithelial cells
    
    • >5/mm³ indicates contamination from the meatus
  • Only 1 bacterial species (monoculture)
    
    • >10^2-5 CFU
• Don’t culture urine unless…
  
  • Abnormal UA
  • Indicated

Question 11

Significance of urine findings in UTIs

• No infection
  
  • Symptoms
  • WBCs or LE
  • Bacteria in CFUs
• Colonization
  
  • Symptoms
  • WBCs or LE
  • Bacteria in CFUs
• Infection
  
  • Symptoms
  • WBCs or LE
  • Bacteria in CFUs

Answer 11

• No infection
  
  • Symptoms
    
    • No symptoms
  • WBCs or LE
    
    • <10
  • Bacteria in CFUs
    
    • <10³
• Colonization
  
  • Symptoms
    
    • Asymptomatic bacteriuria
    • Foley catheter
  • WBCs or LE
    
    • ?
  • Bacteria in CFUs
    
    • 10^3-5
• Infection
  
  • Symptoms
    
    • Cystitis
    • Pyelonephritis
    • Urosepsis
  • WBCs or LE
    
    • _>_10
    • Pyelonephritis: pus or TNTC
  • Bacteria in CFUs
    
    • >10⁵

Question 12

Asymptomatic bacteriuria in healthy, premenopausal women

Answer 12

• Bacteriuria increases risk for symptomatic UTI but is not associated with adverse outcomes
• Treatment of asymptomatic bacteriuria neither decreases frequency of symptomatic infection nor prevents further episodes of asymptomatic bacteriuria
• So screening for and treatment of asymptomatic bacteriuria is not indicated

Question 13

Asymptomatic bacteriuria in pregnant women

Answer 13

• Bacteriuria increases the risk of…
  
  • Developing pyelonephritis during pregnancy 20-30 fold
  • Premature delivery and to have low birthweight infants
• Gp B Streptococcus (GBS) colonization puts newborn at risk for bacterial GBS meningitis
• Treatment of bacteriuria decreases above risks so screening for bacteriuria by urine culture is indicated at least once in early pregnancy.

Question 14

Asymptomatic bacteriuria in elderly institutionalized subjects

Answer 14

• Bacteriuria increases the risk for symptomatic UTI
  
  • Not associated w/ adverse outcomes
• Treatment w/ antibiotics…
  
  • Does not decrease the rate of symptomatic infections
  • Does not improve survival
  • Does not decrease chronic GU symptoms
• Screening and treatment of asymptomatic bacteriuria in elderly institutionalized residents of long-term care facilities is not recommended

Question 15

Asymptomatic bacteriuria in patients with indwelling catheters

Answer 15

• Antimicrobial therapy
  
  • Not associated w/ a decreased rate of symptomatic infections
  • Associated w/ a high incidence of recurrences w/ more resistnat organisms
• Asymptomatic bacteriuria or gunguria should not be screened for or treated in pts w/ an indwelling urethral catheter

Question 16

Screening of asymptomatic people for bacteriuria

• When appropriate
• Undesirable outcomes associated w/ therapy

Answer 16

• Only appropriate to prevent adverse events
  
  • In pregnancy (Gp B Streptococcus)
  • Prior to urologic surgery (manipulation that can facilitate retrograde introduction)
• Undesirable outcomes associated w/ therapy
  
  • Antimicrobial resistance
  • Adverse drug effects
  • Costs w/o benefits
  • Antibiotic-associated disease (ex. C. difficile associated diarrhea)

Question 17

Acute uncomplicated UTI (cystitis)

• Symptoms
• Exclude other causes
• Diagnosis
  
  • Dipstick or microscopy
  • Culture
• Common bacterial causes

Answer 17

• Symptoms
  
  • Dysuria, frequency, urgency
  • Initial and terminal hematuria
  • Suprapubic discomfort
  • Low-grade fever may occur
• Exclude other causes
  
  • STIs
  • Urethritis
  • Vaginitis
• Diagnosis
  
  • Dipstick or microscopy
    
    • Nitrite positive
    • Positive LE/WBC (>10 WBCs)
  • Culture
    
    • Not routinely done or necessary
    • Carefully obtained clean catch
    • 10^2-5 cfu/ml
    • 1 bacterial species only
• Common bacterial causes
  
  • E. coli (gram negative rod) in 80-90%
  • S. saprophyticus (gram positive coccus) in 5-15%
  • Proteus & Klebsiella (gram negative rods)

Question 18

Therapy for acute uncomplicated UTI in a non-pregnant adult female without anatomic/functional/immunologic abnormalities

• Goal
• W/o treatment…
• E. coli resistance (lowest to highest)
• First line treatment
• Alternatives

Answer 18

• Goal
  
  • Treat symptoms b/c acute uncomplicated cystitis rarely progresses to severe disease
• W/o treatment…
  
  • 25-42% of UTI symptoms resolve spontaneously
  • Antimicrobial resistance doesn’t necessarily prevent a cure but “tips the balance” when host factors overcome the decreased bacterial burden
• E. coli resistance (lowest to highest)
  
  • Fosfomycin
  • Nitrofurantoin
  • Cefuroxime
  • TMP-SMX (bactrim)
  • Ciprofloxacin
  • Ampicillin / sulbactam
  • Amoxicillin
• First line treatment
  
  • Nitrofurantoin
    
    • 100 mg BID for 5 days
    • 93% cure
    • Not for pyelonephritis
  • Fosfomycin
    
    • 3 grams once PO
    • 91% cure
    • Not for pyelonephritis
• Alternatives
  
  • Cefuroxime
    
    • 250 mg BID PO for 7 days
    • Ecologic AE
  • TMP-SMX (bactrim)
    
    • DS PO for 3 days
  • Fluoroquinolones (ciprofloxacin)
    
    • 3-5 days
    • Ecologic AE

Question 19

Therapy for recurrent uncomplicated cystitis

• General
• Relapse
• Reinfections

Answer 19

• General
  
  • Obtain UA & culture
• Relapse: same organism in <2 weeks
  
  • Non-adherence
    
    • Side effects, too expensive, stopped too early due to resolved symptoms
    • Urge patient to take Abx, think of cheaper alternative
  • Abx resistance
    
    • Use sensitivities to prescribe alternative antibiotic
  • Un-eradicated focus (stone)
    
    • Consider urologic evaluation
• Reinfections: may be same or different organism >2 weeks
  
  • Post-coital
    
    • Consider “prophylactic” antibiotic
  • Vaginal atrophy
    
    • Consider application of topical estrogen
  • Post-void residual
    
    • Decrease size of prostate, intermittent catheterization

Question 20

Therapy for uncomplicated UTI: acute pyelonephritis

• Acute pyelonephritis
• For mild to moderately ill patients (hospitalized)
• For severely ill patients and life-threatening urosepsis
• If fever persists and in all children and men (obtain urine culture)

Answer 20

• Acute pyelonephritis
  
  • Mostly an ascending infection
  • Usually caused by E. coli
  • Obtain urine culture
  • Obtain blood cultures if hospitalized
• For mild to moderately ill patients (hospitalized)
  
  • Ceftriaxone 1 gram IV once daily
  • Patients usually improve in 48-72 hours
  • Treat for 10-14 days
• For severely ill patients and life-threatening urosepsis
  
  • Ceftriaxone + aminoglycoside (gentamicin or tobramycin)
  • IV therapy until patient afebrile for 48-72 hours
  • Treat for 2 weeks
• If fever persists and in all children and men (obtain urine culture)
  
  • Consider renal US, CT scan or ± Intravenous pyelogram (IVP)
  • Look for perinephric abscess
  • Exclude urinary obstruction

Question 21

Therapy for uncomplicated UTI: cystitis & pyelonephritis in males

• General
• Young men
• Older men
• Most common cause of relapsing UTI in males

Answer 21

• General
  
  • Obtain urine culture
• Young men
  
  • UTI’s are rare in men under 50
  • Concurrent prostatitis
  • Consider anatomic abnormalities
  • Consider anal insertive sex or use of sex toys
• Older men
  
  • Consider calculi, an enlarged prostate (obstruction), or chronic prostatitis
  • Organisms differ:
    
    • E. coli accounts for 40-50%
    • Proteus, Providencia and Enterococcus account for rest
• Most common cause of relapsing UTI in males
  
  • Chronic bacterial prostatitis

Question 22

Therapy for uncomplicated UTI: in males other than cystitis & pyelonephritis

• Urethritis (STIs)
• Prostatitis
  
  • Causes in older males
  • Acute prostatitis
    
    • Diagnosis
    • Therapy
    • Complications if untreated
  • Chronic prostatitis
    
    • Diagnosis
    • Therapy

Answer 22

• Urethritis (STIs)
  
  • Gonorrhea (ceftriaxone 250 mg IM once)
  • Chlamydia, Ureoplasma (doxycycline 100 mg BID PO for 7 days or azithromycin 1 gram PO once)
• Prostatitis
  
  • Causes in older males
    
    • Gram negative rods
    • Enterococci (gram positive cocci)
    • Staph. aureus
    • Gonorrhea
    • Chlamydia, Ureoplasma
  • Acute prostatitis
    
    • Diagnosis
      
      • Fever, chills
      • Dysuria, pain
      • Marked local tenderness upon palpation of prostate
    • Therapy
      
      • Excellent penetration by most antibiotic classes-easily cured with 2 weeks of antibiotics
    • Complications if untreated
      
      • Prostatic abscess and chronic prostatitis
  • Chronic prostatitis
    
    • Diagnosis
      
      • Chronic pain
      • Dysuria
      • Recurrent “UTI’s” – same organism
    • Therapy is difficult due to…
      
      • Poor antibiotic penetration
      • Acidic environment
      • Presence of biofilm and calculi
      • Preferred agents for a 6 week course
        
        • Fluoroquinolones
        • TMP-SMX

Question 23

Role of catheters in UTI (CA-UTI)

Answer 23

• Conduit (bacterial highway)
  
  • Internal lumen
  • Migration of bacteria along external surface
• Foreign body facilitating biofilm formation
  
  • Protects bacteria from host defense
  • Protects bacteria from antibiotics
• Incomplete emptying of the bladder due to position of catheter

Question 24

Catheter-related UTIs

• Complications in catheterized patients
• Cannot diagnose UTI infection unless pt has…
• Prevention of catheter-related UTI’s
• Prevention methods w/ unproven benefits

Answer 24

• Complications in catheterized patients
  
  • Bacteriuria is universal
    
    • Providencia stuartii (24%)
    • Proteus (15%)
    • E. coli (14%)
    • Pseudomonas (12%)
  • Pyuria is common from bladder irritation and presence of WBC’s cannot be used as diagnostic criterion for UTI
• Cannot diagnose UTI infection unless pt has…
  
  • Fever (cured often w/ cath change alone)
  • Pyelonephritis
• Prevention of catheter-related UTI’s
  
  • Avoid catheterization and early removal or replace catheter frequently
    
    • Intermittent catheterization is superior
    • Condom catheter than indwelling catheter (males)
  • Avoid extrinsic contamination of system
    
    • Closed catheter drainage
• Prevention methods w/ unproven benefits
  
  • Antiseptics in drainage bag
  • Antibiotics will decrease bacteriuria and can then lead to recolonization with resistant organisms
  • Antimicrobial coated catheters

Question 25

Candida in the urine * Almost all candiduria occurs in patients with... * Risk factor * Treatment * Only indications for treatment of asymptomatic candiduria

Answer 25

* Almost all candiduria occurs in patients with... * Indwelling catheters * Risk factor * Prior antibiotics * Treatment * Removal of the catheter results in clearance of most candiduria * Oral fluconazole or amphotericin B bladder irrigation eliminate candiduria short-term but is not more effective than no therapy * Only indications for treatment of asymptomatic candiduria * Urinary tract obstruction (fungus ball) * Neutropenia * Renal transplant recipient * Urologic procedure in next 48-72 hours

Question 26

Sterile pyuria

Answer 26

* Antibiotic pre-treatment * Kills bacteria (culture negative) * Non-infectious cause * Interstitial nephritis / cystitis * Organisms that don’t grow on commonly used culture media * TB * Fungi

Question 27

Genitourinary tuberculosis * General * Requires high index of suspicion * Key finding * Requires... * When confirmed, treat w/...

Answer 27

* General * Hematogenous seeding can occur in cortex and in the medulla * Granulomas --\> caseation --\> erosion into collecting system --\> further spread to ureters, bladder, prostate * Requires high index of suspicion * Clinical disease is mostly insidious with dysuria, renal functional defects * Key finding * Sterile pyuria * Requires... * PPD skin testing or TB-specific Interferon Gamma-Release Assay (blood test) * Imaging * Culture M. tuberculosis from urine * Early AM sample (urine concentrated) * Multiple urine samples * When confirmed, treat w/... * Rifampin & Isoniazid (6 months) * Pyrazinamide & Ehtambutol (first 2 months)

Question 28

Test question 1 A 69 yo woman sees her internist for a periodic health evaluation. She has hypertension that is well controled on hydrochlorothiazide and reports no new symptoms. Medical history includes anaphylaxis following penicillin administration and mild nausea after taking a sulfa drug 20 years ago. Physical examination is normal. Routine laboratory studies are also normal except that urinalysis shows 2-3 WBCs/hpf . Urine culture grows \> 104 cfu E. coli that is sensitive to all antibiotics tested. Which is the most appropriate choice for this patient? A. No antibiotic therapy B. Ciprofloxacin 500 mg BID for three days C. Nitrofurantoin 100 mg BID for five days D. Trimethoprim-sulfamethoxazole (Bactrim) DS BID for three days E. Fosfomycin 3 grams PO (once)

Answer 28

A

Question 29

Test question 2 An 89 yo woman who has moderate cognitive impairment is admitted to a nursing home. She is otherwise well except for a history of urinary tract infections. On admission, her urine is noted to be dark. She is afebrile. Physical examination reveals atrophic vaginitis. Dipstick urinalysis is positive for leukocyte esterase; urine sediment contains 5-10 WBCs/hpf. Urine culture grows \> 105 cfu Klebsiella that is resistant to multiple antimicrobial agents (ESBL+). Which of the following is the best therapy for this patient? A. Estrogen, intravaginally B. Estrogen, orally C. Ceftriaxone 1 gram IV every 24 hours for 7 days D. Fosfomycin 3 grams PO once E. Ertapenem 1 gram IM once

Answer 29

A

Question 30

Test question 3 An 80 yr old male has an IV for chemotherapy and presents with a low grade fever. He has a UA with 20 WBC’s/hpf and Urine culture grows 103 cfu Staph aureus (MRSA). What is the most appropriate next step? A. Do not treat (urinary colonization) B. Vancomycin PO for 7 days C. Nafcillin IV for 14 days D. Draw blood cultures E. Repeat UA and urine cultures

Answer 30

D

Question 31

Available antibiotics commonly used for UTI’s

Answer 31

* Beta-lactams * Penicillins * Cephalosporins * Carbapenems * Quinolones * Aminoglycosides * Vancomycin * Fosfomycin * Doxycycline * Nitrofurantoin * TMP/SMX (bactrim)

Question 32

Beta-lactam bacterial coverage * Penicillins * PCN * Amoxicillin, Ampicillin * Amox/clav, Amp/sulb * Piperacillin/tazo, ticarcillin/clav * Nafcillin, oxacillin, methicillin * Cephalosporins * 1st Generation * 2nd Generation * 3rd Generation * Ceftriaxone * Ceftazidime * 4th Generation * Cefepime * Ceftaroline * Carbapenems * Enterococcus +/- * Ertapenem * Imipenem, Meropenem, Doripenem

Answer 32

* Penicillins: **Streptococcus, Enterococcus, anaerobes** * PCN * Amoxicillin, Ampicillin: **Some GNR** * Amox/clav, Amp/sulb: **GNR, anaerobes, MSSA** * Piperacillin/tazo, ticarcillin/clav: **Resistant GNR, Pseudomonas** * Nafcillin, oxacillin, methicillin: **MSSA, NOT Enterococcus** * Cephalosporins: **Streptococcus, NOT Enterococcus, NOT Listeria** * 1st Generation: **Strep, MSSA, some GNR** * 2nd Generation: **GNR** * 3rd Generation: **Less MSSA, more (resistant) GNR** * Ceftriaxone: **NOT Pseudomonas** * Ceftazidime: **Pseudomonas** * 4th Generation * Cefepime: **Pseudomonas** * Ceftaroline: **Staphylococcus** * Carbapenems: **Streptococcus, Resistant GNR** * Enterococcus +/- * Ertapenem: **NOT Pseudomonas** * Imipenem, Meropenem, Doripenem: **Pseudomonas**

Question 33

Non-beta-lactam bacterial coverage * Quinolones * Ciprofloxacin * Levofloxacin, moxifloxacin * Aminoglycosides (Gent, tobra) * Tetracyclines (TCN) (doxycycline) * Vancomycin * Metronidazole * TMP/SMX (bactrim) * Nitrofurantoin * Fosfomycin

Answer 33

* Quinolones: **GNR, atypicals, Streptococci, NOT Staph** * Ciprofloxacin: **Pseudomonas** * Levofloxacin, moxifloxacin: **More G+ coverage** * Aminoglycosides (Gent, tobra): **Aerobe GNR** * Tetracyclines (TCN) (doxycycline) **G+cocci, atypical** * Vancomycin: **Gram positives** * Metronidazole: **Anaerobes** * TMP/SMX (bactrim): **GNR, CA-MRSA** * Nitrofurantoin: **GNR, Enterococcus** * Fosfomycin: **GNR**

Question 34

Penicillin (PCN) allergy * Frequency * Rate of Type I reaction (anaphylaxis) cross-reactivity * Of 1,000 patients claim PCN allergy... * Use of “other” antibiotics * So it is exceedingly important to... * Base decision on...

Answer 34

* Frequency * ~10% of patients report PCN allergy * ~10-20% will have a positive result to skin testing * Rate of Type I reaction (anaphylaxis) cross-reactivity * 3-10% to cephalosporins (depending on side-chain) * ~1% to carbapenems * Of 1,000 patients claim PCN allergy... * 150 are truly PCN allergic * 5-15 allergic to cephalosporins (0.5-1.5%) * 2 will react to carbapenems (0.2%) * Use of “other” antibiotics may lead to inferior outcomes and possibly higher toxicity * Ex. Ciprofloxacin/aztreonam for gram-negative sepsis * Ex. Vancomycin for MSSA infections * So it is exceedingly important to verify reaction * Talk to patient, family, search past records, etc * Decide whether it was a side effect or allergic reaction and appropriately document new reactions * Base decision on... * Severity of reaction * Whether has safely utilized other agents in class * Degree of cross-reactivity * Likelihood of resistance, etcetera

Question 35

Antibiotic allergies * TMP-SMX (bactrim) * PCN * Rash only * Type I * Cephalosporins * Rash only * Type I

Answer 35

* TMP-SMX (bactrim) * Don't rechallenge * PCN * Rash only * Use cephalosporins * Type I * Avoid PCN, cephalosporins, carbapenems * Use alternativies * Desensitize if necessary * Cephalosporins * Rash only * Use dif cephalosporin or alternatives * Type I * Avoid PCN, cephalosporins, carbapenems * Use alternatives * Densensitize if necessary