From the Guidelines
For empiric coverage of gram-negative infections, a carbapenem such as meropenem (1g IV every 8 hours) is recommended, as it provides broad-spectrum coverage against gram-negative rods, including resistant organisms 1. The choice of antibiotic depends on various factors, including the suspected organism, local resistance patterns, infection site, and patient factors such as allergies and kidney function. Key factors to consider when selecting an antibiotic include:
- The severity of the infection and the risk of mortality
- The presence of multidrug-resistant (MDR) pathogens
- The local antibiogram and susceptibility patterns of the suspected organism
- The potential for antibiotic resistance development Some of the main classes of antibiotics that effectively cover gram-negative rods include:
- Fluoroquinolones (ciprofloxacin, levofloxacin)
- Aminoglycosides (gentamicin, tobramycin, amikacin)
- Carbapenems (meropenem, imipenem, ertapenem)
- Third and fourth generation cephalosporins (ceftriaxone, cefepime)
- Piperacillin-tazobactam
- Polymyxins (colistin) It is essential to note that antibiotic stewardship is crucial to prevent resistance development, and narrowing therapy based on culture results is recommended whenever possible 1. In cases where the risk of MDR pathogens is high, initial empiric therapy may involve a single broad-spectrum agent or a combination of agents, depending on the local antibiogram and the patient's condition 1. For example, in patients with septic shock or at high risk of mortality, a dual-pseudomonal regimen plus MRSA coverage may be necessary, using agents such as imipenem, meropenem, cefepime, piperacillin/tazobactam, or ceftazidime, in combination with an aminoglycoside or an antipseudomonal quinolone 1.
From the FDA Drug Label
Levofloxacin has in vitro activity against Gram-negative and Gram-positive bacteria fections as described in Indications and Usage (1): Gram-Negative Bacteria Enterobacter cloacae Escherichia coli Haemophilus influenzae Haemophilus parainfluenzae Klebsiella pneumoniae Legionella pneumophila Moraxella catarrhalis Proteus mirabilis Pseudomonas aeruginosa Serratia marcescens
Levofloxacin is an antibiotic that covers Gram-negative rods, including:
- Enterobacter cloacae
- Escherichia coli
- Klebsiella pneumoniae
- Proteus mirabilis
- Pseudomonas aeruginosa
- Serratia marcescens 2
From the Research
Antibiotics for Gram-Negative Rods
The following antibiotics have been found to be effective against Gram-negative rods:
- Imipenem and meropenem, members of the carbapenem class of beta-lactam antibiotics, are active against aerobic gram-negative nosocomial pathogens including Pseudomonas 3
- Aztreonam, a monobactam, has activity against most aerobic gram-negative bacilli including P. aeruginosa 3
- Ceftazidime, a third-generation cephalosporin, is active against Enterobacteriaceae and Pseudomonas aeruginosa 4
- Cefepime and piperacillin-tazobactam are considered as carbapenem-sparing alternatives for the treatment of cephalosporin-resistant Gram-negative bacteria 5
- Novel β-lactam-β-lactamase inhibitor combinations such as ceftolozane-tazobactam and ceftazidime-avibactam have been found to be effective against multidrug-resistant Gram-negative infections 5
Specific Gram-Negative Rods
The following antibiotics have been found to be effective against specific Gram-negative rods:
- Pseudomonas aeruginosa: imipenem, meropenem, aztreonam, ceftazidime, ceftolozane-tazobactam, and ceftazidime-avibactam 3, 4, 5
- Enterobacteriaceae: imipenem, meropenem, ceftazidime, cefepime, and piperacillin-tazobactam 3, 4, 5
Treatment Considerations
When treating Gram-negative rod infections, the following considerations should be taken into account:
- Early, appropriate antibiotic treatment significantly improves patients' outcomes and prevents the development of septic shock 6
- Monitoring of serum concentrations of antibiotic is recommended in critically ill septic patients 6
- Combination therapy with two or more antibiotics may be necessary for the treatment of serious Gram-negative infections 6, 7