Bactericidal (bacteria-killing) versus bacteriostatic (bacteria-inhibiting) drugs for treating infections

When treating an infection, physicians may face a choice between using a bactericidal (bacteria-killing) drug, a bacteriostatic (bacteria-inhibiting) drug or a combination of the two.

The solution is not always obvious, particularly since a drug that is bactericidal for one strain of bacteria may only inhibit the growth of another strain, according to an article in the November 1 issue of Clinical Infectious Diseases.

Although it might seem logical that bactericidal drugs would be preferable to bacteriostatic drugs, the type of infection is important in determining which kind of drug to use. Endocarditis seems to be best treated by bactericidal drugs. Meningitis is another candidate for bactericidal drugs. Strikingly, a bacteriostatic drug can antagonize the action of a bactericidal one in the treatment of meningitis. In treating urinary tract infections and preventing staphylococcal wound infections, studies have shown that bacteriostatic drugs work as well as bactericidal drugs.

In central nervous system infections, a rapidly bactericidal drug can release bacterial products that stimulate inflammation. For this reason, it is recommended that corticosteroids be given at the same time as a bactericidal antibiotic for bacterial meningitis. Certain bacteriostatic drugs may be preferable in cases of streptococcal and clostridial gangrene, because they inhibit the production of the toxins that cause much of the morbidity.

Some infectious disease physicians wrongly believe that bacteria-killing drugs are automatically preferable to those that inhibit bacterial growth, according to Dr. Robert Finberg, of the University of Massachusetts, lead author of the study. "The misperception that it's always better to use a bactericidal drug is incorrect," said Dr. Finberg.

"It's probably important to use bactericidal drugs in treating endocarditis and meningitis," Dr. Finberg added, "but in many situations, cidal drugs are not preferable over static drugs."