Infectious Diseases II
Patient Case
A 74-year-old man is admitted to the surgical ICU after elective hip replacement surgery. The patient,
who has a history of chronic pulmonary obstructive disease, cannot be weaned off the ventilator after
surgery. During the patientβs course, he develops signs and symptoms of infection. His vital signs and labo-
ratory values are as follows: blood pressure 94/55 mm Hg, heart rate 114 beats/minute, temperature 101.9Β°F
(38.8Β°C), WBC 18 x 103 cells/mm3, and lactate 3.2 mmol/L. The patient is empirically initiated on piper-
acillin/tazobactam and vancomycin and given 2 L of crystalloid fluids; pan cultures are sent. Urinalysis
reveals pyuria, positive leukocyte esterases, and nitrites. Blood and sputum cultures are negative, but urine
culture shows E. coli. The patientβs urinary catheter is removed, and vancomycin is discontinued. On day 3
of therapy, antibiotic susceptibility results are available. The patientβs E. coli is resistant to third-generation
cephalosporins with laboratory confirmation of the presence of ESBL. The laboratory reports the following
antimicrobials and corresponding MIC values: piperacillin/tazobactam less than 2 mcg/mL β S; cefepime
4 mcg/mL β SDD; imipenem 0.5 mcg/mL β S; and ciprofloxacin 0.25 mcg/mL β S. The patientβs vital signs
and laboratory values are as follows: blood pressure 110/70 mm Hg, heart rate 98 beats/minute, respiratory
rate 30 breaths/minute, temperature 98.7Β°F (37.1Β°C), and WBC 9 x 103 cells/mm3. Which is the most appro-
priate antibiotic option?
Carbapenemase
Seen in Acinetobacter, Pseudomonas, and Enterobacterales
The global spread of carbapenem resistance has become an epidemic.
The CDC continues to report that carbapenem-resistant Enterobacterales (CRE) is at an urgent
hazard level, where high consequence and probability for widespread public health concerns exist.
| d. | Confers resistance to most Ξ²-lactams, including carbapenems, cephalosporins, monobactam, and |
|---|
broad-spectrum penicillins
Treatment options
Tigecycline:
| (a) | Glycylcycline antibiotic, which is structurally similar to tetracyclines |
|---|---|
| (b) | Mechanism of action: Inhibition of 30s ribosomal subunit |
| (c) | Spectrum of activity: |
| (1) | Gram-positive bacteria: Enterococcus (including vancomycin-resistant enterococci), |
Listeria, Staphylococcus (including MRSA/CoNS), Streptococcus
| (2) | Most gram-negative bacteria, including Acinetobacter, ESBL-producing Enterobacte- |
|---|
rales, derepressed AmpC Enterobacterales, CRE, and Stenotrophomonas
| (3) | Anaerobes, including Bacteroides and Clostridium |
|---|---|
| (4) | Atypicals |
| (5) | Does not cover Pseudomonas, Providencia, Proteus, or Morganella |
| (d) | PK |
| (1) | Wide volume of distribution: 7β10 L/kg |
| (2) | The intracellular distribution of tigecycline results in a decreased serum/tissue |
concentration ratio. This has led many clinicians to state that tigecycline is not the
ideal drug for bloodstream infections. However, tigecycline has not been evaluated
exclusively for the treatment of bloodstream infections. In a pooled analysis of eight