Antibiotic Selection and Clinical Applications

Introduction to Antibiotic Classes

The American College of Physicians recommends selecting the most appropriate IV antibiotics based on the suspected pathogen, infection site, and patient factors, with beta-lactams forming the backbone of treatment for most serious infections 1, 2
The Infectious Diseases Society of America suggests that beta-lactam antibiotics, including penicillins, cephalosporins, and carbapenems, are effective against a wide range of gram-positive and gram-negative bacteria 1, 2

Penicillin G is recommended as first-line treatment for streptococcal infections, including Streptococcus pneumoniae with penicillin MIC <2 3
Ampicillin/Amoxicillin is used for susceptible streptococcal and enterococcal infections 1
Oxacillin/Nafcillin is specific for methicillin-susceptible Staphylococcus aureus (MSSA) infections 2, 3
Piperacillin-tazobactam provides broad-spectrum coverage for mixed infections, including Pseudomonas and anaerobes, and is commonly used for intra-abdominal infections 1, 4

Gentamicin/Tobramycin is used for serious gram-negative infections, often in combination with beta-lactams 1, 5
Vancomycin is the primary agent for MRSA infections and resistant gram-positive organisms 2, 5
Ciprofloxacin has strong gram-negative coverage, including Pseudomonas 1
Linezolid is effective against resistant gram-positive infections, including MRSA and VRE 6

For skin and soft tissue infections, such as cellulitis/abscess, cefazolin is recommended for MSSA, while vancomycin is recommended for suspected MRSA 2
For respiratory infections, such as community-acquired pneumonia, ceftriaxone plus macrolide or respiratory fluoroquinolone monotherapy is recommended 3
For intra-abdominal infections, such as peritonitis/abscess, piperacillin-tazobactam, carbapenem, or ceftriaxone plus metronidazole is recommended 4

For neutropenic fever, initial empiric therapy with anti-pseudomonal beta-lactam (piperacillin-tazobactam, cefepime, carbapenem) is recommended 7
For multi-drug resistant organisms, such as carbapenem-resistant Enterobacterales, ceftazidime-avibactam or polymyxin-based combinations are recommended 6
For pediatric patients, dosing should be based on weight and age-specific pharmacokinetics, and tetracyclines should be avoided in young children due to dental staining 3, 4