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 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 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.

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.

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.

Lyme disease in North America is caused by the spirochete Borrelia burgdorferi, which is transmitted to humans by Ixodes scapularis or pacificus ticks. These ticks may also carry other pathogens; coinfection with Babesia microti or Anaplasma phagocytophilum (formerly Ehrlichia) has been reported.1 In 2001 and 2002, 12 states (CT, DE, ME, MD, MA, MI, NH, NJ, NY, PA, RI, WI) reported about 95% of all the Lyme disease in the US, but cases occurred in all states except HI, MT and OK. Most Lyme disease in North America occurs between May and September.

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.

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.

Lyme disease is caused by the spirochete Borrelia burgdorferi and transmitted to humans by Ixodes ticks. These ticks may also carry other pathogens; co-transmission of Babesia and Ehrlichia species has been reported.

Gatifloxacin and moxifloxacin are now available for once-daily treatment of patients with community-acquired pneumonia, acute bacterial exacerbations of chronic bronchitis, or acute sinusitis.

Lyme disease, a multisystem infection transmitted by ixodid ticks and caused by the spirochete Borrelia burgdorferi is the most common vector-borne illness in the USA. Cases have been reported in 44 states, and also in Canada and many countries in Europe and Asia (ME Falagas and SL Gorbach, Infect Dis Clin Pract, 5:217, 1996).

Sparfloxacin (Zagam - Rh ne-Poulenc Rorer) and levofloxacin (Levaquin - Ortho-McNeil) are the newest fluoroquinolone antimicrobials to be approved by the US Food and Drug Administration. Sparfloxacin in a once-daily oral preparation is being marketed for treatment of community-acquired pneumonia and acute bacterial exacerbations of chronic bronchitis. Levofloxacin, which is the active stereoisomer of ofloxacin (Floxin), is available for either oral or parenteral use; it is approved for oncedaily treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis, sinusitis, skin and skin structure infections and complicated urinary tract infections.

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).

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.

Piperacillin/tazobactam (Zosyn - Lederle), an antibiotic combination product, has been approved by the US Food and Drug Administration for intravenous treatment of intra-abdominal, pelvic, skin, and skin-structure infections and for community-acquired pneumonia of moderate severity.

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.

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.

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.

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).