Drug-Resistant Pneumococci Increasingly Common in Elderly, Study Suggests

Drug-resistant strains of pneumonia-causing bacteria are becomingincreasingly prevalent and dangerous among the elderly, new researchsuggests.

In a study of 590 adult patients who became infected with pneumococcalbacteria between January 1991 and April 1994, researchers in Columbus,Ohio, found that more than half the cases occurred in patientsage 65 or over.

Furthermore, they found that penicillin-resistant pneumococcalbacteremia doubled among elderly patients over the course of thestudy. Cases increased from 5.3 per 100,000 people in 1991 to10.6 per 100,000 in 1993.

"The incidence of bacteremia cases resistant to penicillinin the elderly patients increased to where it exceeded the totalincidence of pneumococcal bacteremia in the younger patients,"said Dr. Joseph F. Plouffe, professor of internal medicine atOhio State University and lead author of the study.

"The findings of this study suggest that physicians who treatthe elderly will have to consider drug resistance when decidingabout treatment options. Increased use of pneumococcal vaccinesand recognition of antimicrobial resistance patterns may helpphysicians in treating patients with pneumococcal bacteremia."

Plouffe conducted this research with Drs. Robert F. Breiman andRichard R. Facklam, both from the Centers for Disease Controland Prevention (CDC). The group's work appeared in the January16, 1996, special issue of the Journal of the American MedicalAssociation on global and emerging microbial threats.

For their study, Plouffe and his colleagues identified 590 patientswho were treated for pneumococcal bacteremia at 10 hospitals inFranklin County, Ohio, between January 1991 and April 1994. Foreach patient, the researchers identified the particular strainof Streptococcus pneumoniae causing the infection, as wellas its susceptibility to antimicrobial drugs. To determine patientage, gender, and outcome, researchers reviewed the microbiologylogs and patient charts at each hospital.

The study had the following results:

Patients age 65 or over were almost nine times more likely tosuffer from bacteremia as were younger patients. Patients whowere HIV-positive were 42 times more likely than other adultsto develop the condition.

Nearly one-fifth (19%) of the patients in the study died as aresult of bacteremia. The death rate was 11% among patients under65 years of age, 22% among patients age 65 to 84, and 38% amongpatients age 85 and over. "Bacteremia with S pneumoniaecontinues to be a severe disease with a significant mortalityrate," said Plouffe.

The specific pneumococcal bacteria strains causing patients' bacteremiaremained relatively unchanged over time. However, several of thesebacterial strains became resistant to antimicrobial drugs overthe course of the study. Specifically, penicillin, ceftazidime,and trimethoprim-sulfamethozazole appeared to lose some of theirpotency.

More Vigorous Pneumococcal Vaccine Campaigns Warranted

The bacterial strains identified as penicillin-resistant belongedto eight general categories or serotypes. These bacterial serotypesare all included in the currently available pneumococcal vaccine,Plouffe said. Unfortunately, he said, studies in Franklin Countysuggest that fewer than one-fifth (19%) of people at risk forpneumococcal infection have been immunized against it.

"We believe that more vigorous pneumococcal vaccine campaignsshould be mounted," Plouffe said. "'Administrators ofmanaged health care plans could be valuable allies by adding pneumococcalvaccination to routine preventive health strategy."

The hospital stays of patients with penicillin-resistant pneumococcalinfections were, on average, 3.7 days longer than those of patientswhose infections responded to penicillin.

"At current hospital charges of at least $1,000 per day,it's clear that significant additional expenditures of healthcare resources are required to treat bacteremic patients withthese infections," Plouffe said.

Plouffe said the study's findings underscore the need for restraintin prescribing and using antibiotics. "Excessive antibioticuse appears to be the driving force behind the spread of drug-resistantpneumococcal bacteria in communities," he said. "Nationaleducational programs must be aimed at patients and their physiciansto reduce the demand and use of unnecessary antibiotics. Suchefforts may be particularly valuable in communities that havenot yet experienced a dramatic rise in drug-resistant pneumococcalbacteria."

"Physicians face new challenges with pneumococcal disease,"he said. "Increased use of pneumococcal vaccine and knowledgeof antimicrobial susceptibility patterns of the pneumococcal bacteriapresent in their communities will assist physicians in bettercaring for their patients."