The FDA has approved Vowst (Seres Therapeutics/Nestle HealthScience), an oral capsule containing live fecal microbiota spores, for prevention of additional recurrences of Clostridioides difficile infection (CDI) in adults. Vowst is the first orally administered microbiota-based treatment to be approved for this indication. A rectally-administered live fecal microbiota-based suspension (Rebyota) was approved in 2022 for the same indication. Neither product is approved for acute treatment of CDI.

The FDA has approved Rebyota (Ferring), a rectally-administered, live fecal microbiota suspension, for prevention of additional recurrences of Clostridioides difficile infection (CDI) following antibiotic treatment for a recurrent episode of CDI in adults. Rebyota is the first microbiome-based treatment to be approved for this indication. It is not approved for initial treatment of CDI. Fecal microbiota transplantation (FMT) has been used in patients with multiple CDI recurrences.

Clostridioides (formerly Clostridium) difficile infection (CDI) is the most common infectious cause of healthcare-associated diarrhea in adults. Guidelines on management of CDI have recently been updated.

The FDA has approved Kimyrsa (Melinta), a new IV formulation of the long-acting lipoglycopeptide antibiotic oritavancin, for treatment of adults with acute bacterial skin and skin structure infections caused by susceptible gram-positive bacteria. Orbactiv (Melinta), another IV formulation of oritavancin, was approved in 2014 for the same indication. Kimyrsa has a smaller infusion volume (250 mL vs 1 L) and a shorter infusion time (1 hour vs 3 hours) compared to Orbactiv (see Table 1).

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.

The FDA has approved vancomycin oral solution (Firvanq – Cutis Pharma) for treatment of Clostridium difficile-associated diarrhea and enterocolitis caused by Staphylococcus aureus, including methicillin-resistant strains (MRSA).

The FDA has approved delafloxacin (Baxdela – Melinta), an anionic fluoroquinolone antibiotic, for oral and parenteral treatment of adults with acute bacterial skin and skin structure infections (ABSSSIs), including those caused by methicillin-resistant Staphylococcus aureus (MRSA). It is the first fluoroquinolone to be approved for treatment of MRSA.

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.

The FDA has approved the fully human monoclonal antibody bezlotoxumab (Zinplava – Merck) for use with antibacterial drug treatment to reduce recurrence of Clostridium difficile infection (CDI) in adults with CDI at high risk for recurrence. It is the first drug to be approved for this indication.

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 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.

The FDA has approved fidaxomicin (Dificid – Optimer), a new oral macrolide antibiotic, for treatment of Clostridium difficile-associated diarrhea in patients ≥18 years old. The incidence and severity of C. difficile infection (CDI) have increased in recent years with the emergence of an epidemic hypervirulent strain (NAP1/B1/027), possibly related to widespread use of fluoroquinolones.

Clostridium difficile infection (CDI) is the most common infectious cause of healthcare-associated diarrhea in adults. The incidence and severity of CDI have increased in recent years with the emergence of an epidemic virulent strain (NAP1/BI/027). Common risk factors include admission to a healthcare facility, increasing age and severity of underlying illness, gastric acid suppression and exposure to antimicrobials, particularly clindamycin, ampicillin, cephalosporins or fluoroquinolones. Patients who develop CDI while receiving a precipitating antibiotic should have the antibiotic discontinued, if possible, or switched to another appropriate antimicrobial with a lower risk of CDI.

The FDA has approved ceftaroline fosamil (Teflaro – Forest), an intravenous (IV) cephalosporin, for treatment of acute bacterial skin and skin structure infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA), and for treatment of community-acquired bacterial pneumonia in adults. It is the first beta-lactam antibiotic approved for treatment of MRSA.

Telavancin (Vibativ - Astellas and Theravance), a lipoglycopeptide derivative of vancomycin (Vancocin, and others), has received FDA approval for treatment of complicated skin and skin structure infections caused by susceptible gram-positive bacteria in adults.

Antimicrobial prophylaxis can decrease the incidence of infection, particularly surgical site infection, after certain procedures. Recommendations for prevention of surgical site infection are listed in the table that begins on page 48. Antimicrobial prophylaxis for dental procedures to prevent endocarditis is discussed in The Medical Letter 2007; 49:99.

The recent Medical Letter article on vancomycin dosing and monitoring briefly mentioned use of an alternative antibiotic for treatment of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin. Some readers have asked for more information on this subject.

Click here to view the free full article.

Information about empirical treatment of bacterial infections, emerging trends in antimicrobial resistance, new drugs and new data about older drugs continue to become available. Usual pathogens and empiric treatment for some common types of infections are summarized in the text and a table listing the drugs of choice and alternatives for each pathogen begins on page 40. The recommendations made here are based on the results of susceptibility studies, clinical trials and the opinions of Medical Letter consultants.

Antimicrobial prophylaxis can decrease the incidence of infection, particularly surgical site infection, after certain procedures. Recommendations for prevention of surgical site infection are listed in this article.

The gram-positive anaerobic bacillus Clostridium difficile is the most common identifiable cause of antibiotic-associated diarrhea. The antibiotics most often implicated have been ampicillin, second and third generation cephalosporins, clindamycin and fluoroquinolones. The emergence in recent years of a new, more toxic epidemic strain (BI/NAP1), possibly related to widespread use of fluoroquinolones, has caused a marked increase in the incidence and severity of C. difficile-associated disease (CDAD).

Methicillin-resistant Staphylococcus aureus (MRSA) infections, which have been a concern for many years, previously occurred primarily in hospitalized patients and those recently treated with antibiotics. In the past few years, there has been an increasing incidence worldwide of community-associated (CA) MRSA infections in patients without recent antibiotic exposure or contact with the healthcare system.

Tigecycline (Tygacil - Wyeth), a derivative of minocycline, is a new intravenous (IV) antibiotic approved for treatment of complicated intra-abdominal and skin and skin-structure infections.

Many physicians believe that antimicrobial prophylaxis before procedures that may cause transient bacteremia can prevent endocarditis and prosthetic joint infection in patients at increased risk for these disorders. The effectiveness of this common practice has never been established by controlled trials in humans.

Antimicrobial prophylaxis can decrease the incidence of infection, particularly surgical site infection, after certain operations, but this benefit must be weighed against the risks of toxic and allergic reactions, emergence of resistant bacteria, adverse drug interactions, superinfection and cost. Medical Letter consultants generally recommend antimicrobial prophylaxis only for procedures with high infection rates, those involving implantation of prosthetic material, and those in which the consequences of infection are likely to be especially serious.

New drugs for bacterial infections and new information about older drugs continue to become available. Empirical treatment of some common bacterial infections is discussed in this article. A table listing the drugs of choice and alternatives for each pathogen begins on page 18. These recommendations are based on results of susceptibility studies, clinical trials and the opinions of Medical Letter consultants. Local resistance patterns should be taken into account. Trade names are listed on page 24.

Daptomycin (Cubicin - Cubist), a cyclic lipopeptide (a new class of antibiotics), has been approved by the FDA for intravenous (IV) treatment of complicated skin and skin structure infections. It is being promoted as a once-daily bactericidal alternative to vancomycin (Vancocin, and others) for methicillin-resistant Staphylococcus aureusinfections.

The choice of drugs for treatment of pneumonia depends on the most likely pathogens causing the infection and local antimicrobial resistance patterns. Factors such as severity of illness, presence of co-morbid conditions and whether the infection is community or hospital-acquired also need to be considered.

Linezolid, the first of a new class of antibiotics, the oxazolidinones, has been marketed for treatment of infection due to vancomycin-resistant Enterococcus faecium, nosocomial and community-acquired pueumonia due to Staphylococcus aureus or penicillin-sucsceptible Streptococcus pneumoniae, and skin and skin structure infections, including those due to methicillin-resistant S. aureus (MRSA).

Quinupristin and dalfopristin, two streptogramin antibacterials marketed in a 30:70 combination as Synercid, have received accelerated approval from the FDA for intravenous treatment of bacteremia and life-threatening infection....

Meropenem (Merrem - Zeneca), a carbapenem similar to imipenem-cilastatin (Primaxin), has been approved by the US Food and Drug Administration for intravenous (IV) treatment of complicated intra-abdominal infections in adults and children and bacterial meningitis in children more than three months old. Imipenem (Medical Letter, 28:29, 1986) has been useful for treatment of serious infections in which broad coverage of nosocomial organisms, including anaerobes, is needed. Other drugs for these indications were reviewed in the Medical Letter article on 'The Choice of Antibacterial Drugs' (volume 38, page 25, March 29, 1996).

The gram-positive bacillus Clostridium difficile is the most common identifiable cause of antibiotic-associated diarrhea and pseudomembranous colitis (R Fekety in GL Mandell et al, eds, Principles and Practice of Infectious Diseases, 3rd ed, New York:Churchill Livingstone, 1990, page 863). C. difficile colitis usually develops during or soon after antibiotic treatment. Virtually any antimicrobial agent can cause the disorder, but clindamycin, ampicillin and the cephalosporins have been implicated most frequently. Pseudomembranous colitis was recently reported in five patients who had each taken only a single dose of a cephalosporin (JP Freiman et al, JAMA, 262:902, August 18, 1989).

A penicillin is the drug of choice for treatment of many infections, but allergic reactions to these drugs occur frequently and, rarely, can be fatal. From 5% to 20% of patients have a history of a rash or some other reaction while taking a penicillin, but maculopapular rashes with ampicillin or amoxicillin, especially in children with infectious mononucleosis, are probably not allergic.