Treatment of community-acquired pneumonia (CAP) is usually empiric, with selected antibiotic regimens directed against some of the most common causative pathogens. Recommended empiric regimens are listed in Table 2; recommended antibiotic dosages for treatment of CAP are listed in Tables 3 and 4. Joint guidelines for treatment of CAP by the American Thoracic Society and the Infectious Diseases Society of America (ATS/IDSA) were updated in 2019.

Lefamulin (Xenleta – Nabriva), a semisynthetic pleuromutilin antibiotic, has been approved by the FDA for IV and oral treatment of community-acquired bacterial pneumonia (CABP) in adults. It is the first systemic pleuromutilin antibiotic to be approved in the US; retapamulin (Altabax), a 1% topical ointment for treatment of impetigo, was approved in 2007.

View the Comparison Table: Some Antibiotics for MRSA Skin and Skin Structure Infections

Bacterial infections in adults are generally treated empirically, with the antibiotic covering most, but not all, of the potential causative pathogens. For some infections, culture and sensitivity testing can guide treatment, allowing for use of narrower-spectrum antibiotics. The recommended dosages and durations of antibiotic treatment for common respiratory, skin, and urinary tract infections are listed in Tables 1-3. Infectious disease experts now recommend shorter treatment durations for many infections to reduce the development of antimicrobial resistance and minimize adverse effects.

Antimicrobial prophylaxis can decrease the incidence of postoperative surgical site infection after some procedures. Since the last Medical Letter article on this subject, consensus guidelines have been published. Recommendations for prophylaxis in specific surgical procedures are listed in Table 1.

The FDA has approved ceftolozane/tazobactam (Zerbaxa – Cubist), a combination of a new cephalosporin antibiotic and a beta-lactamase inhibitor, for intravenous treatment of complicated urinary tract and intra-abdominal infections in adults.

The FDA has approved oritavancin (Orbactiv – The Medicines Company), a long-acting lipoglycopeptide antibiotic given as a single intravenous (IV) dose, for treatment of acute bacterial skin and skin structure infections caused by susceptible gram-positive bacteria in adults. It is the third lipoglycopeptide antibiotic to be marketed in the US; telavancin (Vibativ) and dalbavancin (Dalvance) were approved earlier.

The FDA has approved two new drugs for treatment of adults with acute bacterial skin and skin structure infections caused by susceptible gram-positive bacteria. Dalbavancin (Dalvance – Durata) is a long-acting intravenous (IV) lipoglycopeptide antibiotic similar to telavancin (Vibativ). Tedizolid phosphate (Sivextro – Cubist) is an IV and oral oxazolidinone antibacterial drug similar to linezolid (Zyvox). A third IV antibiotic, oritavancin (Orbactiv), recently approved by the FDA for the same indication, will be reviewed in a future issue.

Methicillin-resistant Staphylococcus aureus (MRSA), which was traditionally a nosocomially-acquired organism but now frequently occurs in the absence of healthcare exposure, is the predominant cause of suppurative skin and soft-tissue infections in many parts of the US. Community-associated MRSA usually causes furunculosis, purulent cellulitis, and abscesses, but necrotizing fasciitis, necrotizing pneumonia, and sepsis can also occur.

The text that follows reviews some common bacterial infections and their empiric treatment pending the results of culture and susceptibility testing. The recommendations made here are based on the results of susceptibility studies, clinical trials, and the opinions of Medical Letter reviewers. Tables 1 and 2 list the usual dosages of antibacterial drugs.

Antimicrobial prophylaxis can decrease the incidence of postoperative infection, particularly surgical site infection, after some procedures. Recommendations for such prophylaxis are listed in the table that begins on page 74. Antimicrobial prophylaxis for dental procedures to prevent endocarditis was recently discussed in The Medical Letter.