Drug-resistant strains of pneumonia-causing bacteria are becoming increasingly prevalent and dangerous among the elderly, new research suggests.
In a study of 590 adult patients who became infected with pneumococcal bacteria between January 1991 and April 1994, researchers in Columbus, Ohio, found that more than half the cases occurred in patients age 65 or over.
Furthermore, they found that penicillin-resistant pneumococcal bacteremia doubled among elderly patients over the course of the study. Cases increased from 5.3 per 100,000 people in 1991 to 10.6 per 100,000 in 1993.
"The incidence of bacteremia cases resistant to penicillin in the elderly patients increased to where it exceeded the total incidence of pneumococcal bacteremia in the younger patients," said Dr. Joseph F. Plouffe, professor of internal medicine at Ohio State University and lead author of the study.
"The findings of this study suggest that physicians who treat the elderly will have to consider drug resistance when deciding about treatment options. Increased use of pneumococcal vaccines and recognition of antimicrobial resistance patterns may help physicians in treating patients with pneumococcal bacteremia."
Plouffe conducted this research with Drs. Robert F. Breiman and Richard R. Facklam, both from the Centers for Disease Control and Prevention (CDC). The group's work appeared in the January 16, 1996, special issue of the Journal of the American Medical Association on global and emerging microbial threats.
For their study, Plouffe and his colleagues identified 590 patients who were treated for pneumococcal bacteremia at 10 hospitals in Franklin County, Ohio, between January 1991 and April 1994. For each patient, the researchers identified the particular strain of Streptococcus pneumoniae causing the infection, as well as its susceptibility to antimicrobial drugs. To determine patient age, gender, and outcome, researchers reviewed the microbiology logs and patient charts at each hospital.
The study had the following results:
Patients age 65 or over were almost nine times more likely to suffer from bacteremia as were younger patients. Patients who were HIV-positive were 42 times more likely than other adults to develop the condition.
Nearly one-fifth (19%) of the patients in the study died as a result of bacteremia. The death rate was 11% among patients under 65 years of age, 22% among patients age 65 to 84, and 38% among patients age 85 and over. "Bacteremia with S pneumoniae continues to be a severe disease with a significant mortality rate," said Plouffe.
The specific pneumococcal bacteria strains causing patients' bacteremia remained relatively unchanged over time. However, several of these bacterial strains became resistant to antimicrobial drugs over the course of the study. Specifically, penicillin, ceftazidime(Drug information on ceftazidime), and trimethoprim(Drug information on trimethoprim)-sulfamethozazole appeared to lose some of their potency.
More Vigorous Pneumococcal Vaccine Campaigns Warranted
The bacterial strains identified as penicillin-resistant belonged to eight general categories or serotypes. These bacterial serotypes are all included in the currently available pneumococcal vaccine, Plouffe said. Unfortunately, he said, studies in Franklin County suggest that fewer than one-fifth (19%) of people at risk for pneumococcal infection have been immunized against it.
"We believe that more vigorous pneumococcal vaccine campaigns should be mounted," Plouffe said. "'Administrators of managed health care plans could be valuable allies by adding pneumococcal vaccination to routine preventive health strategy."
The hospital stays of patients with penicillin-resistant pneumococcal infections were, on average, 3.7 days longer than those of patients whose infections responded to penicillin.
"At current hospital charges of at least $1,000 per day, it's clear that significant additional expenditures of health care resources are required to treat bacteremic patients with these infections," Plouffe said.
Plouffe said the study's findings underscore the need for restraint in prescribing and using antibiotics. "Excessive antibiotic use appears to be the driving force behind the spread of drug-resistant pneumococcal bacteria in communities," he said. "National educational programs must be aimed at patients and their physicians to reduce the demand and use of unnecessary antibiotics. Such efforts may be particularly valuable in communities that have not yet experienced a dramatic rise in drug-resistant pneumococcal bacteria."
"Physicians face new challenges with pneumococcal disease," he said. "Increased use of pneumococcal vaccine and knowledge of antimicrobial susceptibility patterns of the pneumococcal bacteria present in their communities will assist physicians in better caring for their patients."