A 72 year old male with a past medical history of Parkinson’s disease and type 2 diabetes presents for progressive cough and shortness of breath for 3 days. Vitals include Temp 100.8F, HR 110, BP 126/80, RR 22, SpO2 89% on room air. Lung sounds are notable for crackles in the lower right lung. A chest x-ray shows focal consolidations of the right middle and right lower lobes with a moderate sized right pleural effusion. Aspiration of the pleural effusion demonstrates grossly purulent fluid with a pleural pH of 7.1. Which of the following antibiotic regimens is NOT appropriate for initial treatment of this patient’s condition?
A: Ampicillin & gentamicin
B: Cefepime & metronidazole
C: Ceftriaxone & ampicillin-sulbactam
D: Vancomycin & piperacillin-tazobactam
Answer: Ampicillin & gentamicin
This patient is presenting with pneumonia complicated by an empyema based on the pleural fluid findings. The initial treatment of an empyema consists of drainage with broad spectrum antibiotics that will cover Staphylococcus and anaerobes. Ampicillin has poor sensitivity against Staphylococcus and weak coverage of gram-negative organisms. Gentamicin is a potent aminoglycoside with good sensitivity against MSSA and gram-negatives but has poor anaerobic coverage. In addition, aminoglycosides have poor penetration into the pleural space.
Cefepime, ceftriaxone, ampicillin-sulbactam, piperacillin-tazobactam have good sensitivity against MSSA. Vancomycin has additional coverage against MRSA. Metronidazole, ampicillin-sulbactam, and piperacillin-bactam have good coverage of anaerobic organisms.
| Diagnostic Criteria for Empyema | Light Criteria for Exudative Pleural Effusion (requires 1 of the following) |
| Aspiration of grossly purulent fluid plus one of the following: | Pleural protein/serum protein > 0.5 |
| Positive gram stain or culture | Pleural LDH/serum LDH > 0.6 |
| Pleural fluid glucose < 40 | Pleural LDH > 2/3 upper limit of normal serum LDH |
| Pleural pH < 7.2 | |
| Pleural LDH > 1000 |
References:
Mace SE, Anderson E. Lung Empyema and Abscess. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill Education; 2020.
Vaudaux P, Waldvogel FA. Gentamicin inactivation in purulent exudates: role of cell lysis. J Infect Dis. 1980;142(4):586-593. doi:10.1093/infdis/142.4.586
