What are some commonly used broad-spectrum antibiotics?

Broad-Spectrum Antibiotics: Comprehensive List

Broad-spectrum antibiotics are antimicrobials with activity against both Gram-positive and Gram-negative bacteria, and the most commonly used classes include fluoroquinolones, carbapenems, extended-spectrum cephalosporins, and beta-lactam/beta-lactamase inhibitor combinations.

Beta-Lactam/Beta-Lactamase Inhibitor Combinations

• Piperacillin-tazobactam provides excellent broad-spectrum coverage and is recommended for complicated intra-abdominal infections, neutropenic fever, and serious nosocomial infections 1
• Ampicillin-sulbactam covers Gram-positive cocci including penicillin-susceptible Streptococcus pneumoniae and Staphylococcus aureus, plus many Gram-negative organisms 1
• Amoxicillin-clavulanate is effective for respiratory tract infections, skin infections, and urinary tract infections with both oral and IV formulations available 1
• Ticarcillin-clavulanate provides antipseudomonal activity and is used for complicated intra-abdominal infections 1

Carbapenems

• Meropenem (1 g IV q8h) offers the broadest spectrum including Pseudomonas aeruginosa, ESBL-producing Enterobacteriaceae, and most anaerobes 1
• Imipenem-cilastatin (500 mg IV q6h or 1 g IV q8h) has similar spectrum to meropenem and is used for severe nosocomial infections 1
• Ertapenem (1 g IV daily) covers Enterobacteriaceae including ESBL producers but lacks antipseudomonal activity, making it suitable for community-acquired infections 1
• Doripenem (500 mg IV q8h) provides coverage similar to meropenem for complicated intra-abdominal infections 1

Fluoroquinolones

• Levofloxacin (750 mg IV/PO daily) demonstrates excellent activity against Gram-negative bacteria including Haemophilus influenzae, atypical pathogens (Mycoplasma, Chlamydophila, Legionella), and improved Gram-positive coverage including S. pneumoniae 1, 2
• Moxifloxacin (400 mg IV/PO daily) has enhanced activity against Gram-positive organisms including S. pneumoniae and anaerobes compared to other fluoroquinolones 1
• Ciprofloxacin (400 mg IV q12h or 500 mg PO q12h) is highly active against Gram-negative bacteria including P. aeruginosa but has limited Gram-positive coverage 1, 2, 3, 4

Important caveat: Ciprofloxacin should not be used as monotherapy for respiratory infections where penicillin-susceptible S. pneumoniae is the primary pathogen due to inadequate Gram-positive coverage 3

Extended-Spectrum Cephalosporins

Third-Generation Cephalosporins

• Ceftriaxone (1-2 g IV q12-24h) provides excellent Gram-negative coverage including H. influenzae and good activity against S. pneumoniae 1
• Cefotaxime (1-2 g IV q6-8h) has similar spectrum to ceftriaxone and is used for pneumonia, intra-abdominal infections, and meningitis 1
• Ceftazidime (1-2 g IV q8-12h) has enhanced antipseudomonal activity but reduced Gram-positive coverage 1

Fourth-Generation Cephalosporin

• Cefepime (2 g IV q8-12h) combines the Gram-negative coverage of third-generation agents with improved Gram-positive activity and antipseudomonal coverage 1

Combination Regimens for Broader Coverage

• Aminoglycoside plus antipseudomonal penicillin or extended-spectrum cephalosporin is recommended for neutropenic fever and severe Gram-negative infections 1
• Third- or fourth-generation cephalosporin plus metronidazole provides comprehensive coverage for intra-abdominal infections including anaerobes 1
• Fluoroquinolone plus metronidazole offers broad-spectrum coverage for intra-abdominal infections in beta-lactam allergic patients 1

Second-Generation Cephalosporins

• Cefuroxime (1.5 g IV q8h or 500 mg PO q12h) covers S. pneumoniae, H. influenzae, and many Enterobacteriaceae 1
• Cefoxitin (2 g IV q6h) includes anaerobic coverage making it useful for intra-abdominal infections 1

Glycopeptides and Alternatives (for Gram-Positive Enhancement)

• Vancomycin (15-20 mg/kg IV q8-12h) should be added to broad-spectrum regimens when MRSA or resistant Gram-positive organisms are suspected 1
• Linezolid (600 mg IV/PO q12h) is effective against MRSA and vancomycin-resistant enterococci but may delay neutrophil recovery in neutropenic patients 1

Clinical Context for Selection

For neutropenic fever: Monotherapy with carbapenems, antipseudomonal cephalosporins, or piperacillin-tazobactam is recommended as initial empiric therapy 1

For complicated intra-abdominal infections: Community-acquired infections can be treated with ertapenem, ampicillin-sulbactam, or fluoroquinolone plus metronidazole; nosocomial infections require broader coverage with meropenem, imipenem, or piperacillin-tazobactam 1

For respiratory tract infections: Fluoroquinolones (levofloxacin, moxifloxacin) or combination therapy with ceftriaxone plus macrolide provide appropriate broad-spectrum coverage 1

Critical warning: Tigecycline carries an FDA Boxed Warning and infectious disease consultation is recommended before use 1