The FDA has approved Exblifep (Allecra), a fixed-dose combination of the cephalosporin cefepime and the beta-lactamase inhibitor enmetazobactam, for IV treatment of adults with complicated urinary tract infections (cUTIs), including pyelonephritis, caused by designated susceptible microorganisms (see Spectrum of Activity). Exblifep is the first product that contains enmetazobactam to be approved in the US.

The CDC has issued new recommendations for treatment of gonococcal infection. A single 500-mg IM dose (1000 mg in patients weighing ≥150 kg) of the third-generation cephalosporin ceftriaxone is now the treatment of choice for patients with uncomplicated urogenital, rectal, or pharyngeal gonorrhea.

The FDA has approved the new aminoglycoside antibiotic plazomicin (Zemdri – Achaogen) for IV treatment of adults with complicated urinary tract infections (cUTIs). Plazomicin is active against multi-drug- resistant Enterobacteriaceae, including strains resistant to other aminoglycosides.

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 announced that it is requiring changes in the labeling of systemic fluoroquinolones to warn that the risk of serious adverse effects, including tendinitis, peripheral neuropathy and CNS effects, generally outweighs their benefit for the treatment of acute sinusitis, acute exacerbations of chronic bronchitis, and uncomplicated urinary tract infections. For these infections, the new labels will recommend reserving fluoroquinolones for patients with no other treatment options.

The FDA has approved ceftazidime/avibactam (Avycaz – Actavis) for IV treatment of complicated urinary tract and intra-abdominal infections in adults who have limited or no other treatment options. Ceftolozane/tazobactam (Zerbaxa – Cubist), another cephalosporin/beta-lactamase inhibitor combination, was approved in 2014.

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.

A reader who took the online continuing medical education (CME) exam for issue 1406 (Med Lett Drugs Ther 2012; 54:101) pointed out that the first question assumed that a rash following oral administration of ampicillin would be due to allergy. Perhaps we should have mentioned in our article on penicillin allergy that late-appearing maculopapular rashes associated with oral ampicillin or amoxicillin are generally considered non-allergic and need not preclude subsequent administration of ampicillin or amoxicillin.

Only a small minority of patients who say they are allergic to penicillin will have a reaction if they take a penicillin.

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 text below reviews some common bacterial infections and their treatment. The recommendations made here are based on the results of susceptibility studies, clinical trials and the opinions of Medical Letter consultants.

Some readers have asked why the June 2009 issue of Treatment Guidelines (Antimicrobial Prophylaxis for Surgery) did not recommend use of ertapenem (Invanz) for prevention of infection after elective colorectal surgery. Ertapenem is a broad-spectrum carbapenem that has been approved for such use by the FDA. Medical Letter consultants do not recommend use of broad-spectrum drugs such as ertapenem, third-generation cephalosporins such as cefotaxime (Claforan), ceftriaxone (Rocephin), cefoperazone (Cefobid), ceftazidime (Fortaz, and others) or ceftizoxime (Cefizox), or fourth-generation cephalosporins such as cefepime (Maxipime) for routine surgical prophylaxis because they are expensive, some are less active than first- or second-generation cephalosporins against staphylococci, and their spectrum of activity includes organisms rarely encountered in elective surgery. These drugs should be reserved for treatment of serious infections, particularly those likely to be caused by organisms resistant to other antimicrobials.

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.

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment could also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

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Most patients with community-acquired pneumonia (CAP) are treated empirically. New guidelines published jointly by the Infectious Diseases Society of America and the American Thoracic Society have recently become available.

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.

Telithromycin (Ketek - Aventis) has been approved by the FDA for oral treatment of mild to moderate community-acquired pneumonia, acute exacerbations of chronic bronchitis and acute bacterial sinusitis in patients age 18 and older. The drug is the first in a new class of antibiotics, the ketolides, derived from the macrolide erythromycin. Telithromycin has been marketed in Europe since 2001.

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.

Immune-mediated hemolysis is a rare adverse effect of second- and third-generation cephalosporins, especially cefotetan (Cefotan) (PA Arndt et al, Transfusion 1999; 39:1239). A recent report serves as a reminder that life-threatening immune-mediated hemolysis rarely can follow administration of ceftriaxone (Rocephin), one of the most commonly used parenteral antibiotics in the US (A Citak et al, J Paediatr Child Health 2002; 38:209).

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment may also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

Cefditoren pivoxil (Spectracef — TAP), a new oral third-generation cephalosporin, has been approved by the FDA for treatment of acute exacerbations of chronic bronchitis, pharyngitis, tonsillitis and uncomplicated skin and soft tissue infections in adults and children 12 or more years old. The drug has been used in Japan for 7 years.

Cefdinir (Omnicef - Parke-Davis), a third-generation oral cephalosporin, has been approved by the FDA for treatment of acute sinusitis, otitis media, acute exacerbations of chronic bronchitis, pharyngitis, community-acquired pneumonia and skin infections. Other drugs available for these indications are reviewed in The Medical Letter Handbook of Antimicrobial Therapy, 1998.

Cefepime hydrochloride (Maxipime - Bristol-Myers Squibb), a new 'fourth-generation' cephalosporin, has been approved by the US Food and Drug Administration (FDA) for parenteral treatment of urinary tract infections and skin and skin-structure infections due to susceptible pathogens, and for moderate to severe pneunmonia caused by Streptococcus pneumoniae (pneumococci), Pseudomonas aeruginosa, Enterobacter or Klebsiella pneumoniae.

Ceftibuten (Cedax - Schering), an oral cephalosporin similar to cefixime (Suprax - Medical Letter, 31:73, 1989), has been approved by the US Food and Drug Administration (FDA) for treatment of acute otitis media, pharyngitis or tonsillitis, and for acute bacterial exacerbations of chronic bronchitis.

Cefpodoxime proxetil (Vantin - Upjohn), a new third-generation oral cephalosporin, has been approved for marketing by the US Food and Drug Administration. It is available for twice-daily treatment of pharyngitis, upper and lower respiratory infections, otitis media, urinary tract infections, skin and soft tissue infections, and for single-dose treatment of uncomplicated gonorrhea in men or women and anorectal gonorrhea in women.

Loracarbef (Lorabid - Lilly), a new beta-lactam antibiotic with antimicrobial activity similar to the second-generation cephalosporins, has been approved by the US Food and Drug Administration for treatment of respiratory, skin, and urinary tract infection caused by susceptible organisms in both adults and children. It will probably compete with drugs such as trimethoprim-sulfamethoxazole (Bactrim, Septra, and others), amoxicillin-clavulanic acid (Augmentin), cefaclor (Ceclor), cefuroxime axetil (Ceftin), and cefprozil (Cefzil - Medical Letter, 34:63, 1992).

Cefprozil (Cefzil - Bristol-Myers Squibb), a new oral second-generation cephalosporin, was recently released in the USA for treatment of pharyngitis, bronchitis, otitis media, and skin and skin-structure infections.

Ciprofloxacin, previously available orally (Cipro - Medical Letter, 30:11, 1988) and for ophthalmic use (Ciloxan - Medical Letter, 33:52, May 31, 1991), is now the first fluoroquinolone antibiotic to become available in the USA in an intravenous (IV) formulation. Cipro I.V. (Miles) is being promoted as an alternative to third-generation cephalosporins, aminoglycosides, and other drugs used for treatment of serious infections.

Since the last Medical Letter review of cephalosporin antibiotics (volume 25, page 57, 1983), many new cephalosporins have become available in the USA.

Cefmetazole sodium (Zefazone - Upjohn), a second-generation parenteral cephalosporin, was recently marketed in the USA for intravenous (IV) treatment of various infections caused by susceptible organisms. Like cefotetan (Cefotan), cefamandole (Mandol), cefoperazone (Cefobid), and moxalactam (Moxam), cefmetazole contains a methylthiotetrazole group that has been associated with prothrombin deficiency.

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).

Cefixime (Suprax - Lederle), an oral cephalosporin antibiotic, was recently approved for marketing by the US Food and Drug Administration. Claimed to be the first oral third-generation cephalosporin, the new drug is offered for once-a-day treatment of otitis media, pharyngitis, bronchitis and urinary tract infections.

Lyme disease, a multisystem bacterial transmitted by Ixodid ticks, particularly in early summer, continues to be a common problem in the USA and many other countries. Since last year (Medical Letter, 30:65, 1988), some new information has become available, but data on the choice, dosage and duration of antibiotic therapy are still available, but data on the choice, dosage and duration of antibiotic therapy are still limited.

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.

Lyme Disease, a multisystem inflammatory disorder transmitted by lxodid ticks and caused by the spirochete Borrelia burgdorferi, is now the most common tick-transmitted illness in the USA. It has been reported in 32 states and on all other continents except Antarctica. Infected ticks have been found not only in wooded areas, but also on well-maintained suburban lawns (RC Falco and D Fish, Am J Epidemiol, 127:826, April 1988). Optimal treatment for this newly discovered disease is still being determined, but some recommendations based on published experience and work in progress can be made.

Cefuroxime axetil (Ceftin - Glaxo), an oral form of the second-generation parenteral cephalosporin cefuroxime (Zinacef), was recently marketed in the USA. Previously available oral cephalosporins are the first-generation drugs cephalexin (Keflex; and others), cephradine (Anspor; and others) and cefadroxil (Duricef; and others), and the second-generation cefaclor (Ceclor); second-generation cephalosporins have more activity against gram-negative bacteria.

Ciprofloxacin hydrochloride (Cipro - Miles), a synthetic antibacterial agent, was recently marketed in the USA for oral treatment of a wide variety of infections. Ciprofloxacin is the second fluoroquinolone to become available in this country; norfloxacin (Noroxin - Medical Letter, 29:25, 1987) is marketed only for treatment of urinary tract infections. Fluoroquinolones are more potent and have a much broader spectrum of activity than older quinolones such as nalidixic acid (NegGram).