Outbreak of Multidrug- Resistant Pneumococcal Pneumonia: A Stitch in Time

Abstract & Commentary

Synopsis: In 84 nursing home residents, only three of whom had received pneumococcal vaccination, a multidrug-resisant Streptococcus pneumoniae serotype 23F was isolated from either the blood or sputum of 4% with pneumonia and from the nasal pharyngeal specimens of 23% of those without pneumonia.

Source: Nuorti J, et al. JAMA 1998;338:1861-1868.

In 84 residents of a nursing home, only three of whom had received pneumococcal vaccination, a multidrug-resistant S. pneumoniae serotype 23F was isolated from either the blood or sputum of 4% with pneumonia and from the nasal pharyngeal specimens of 23% of those without pneumonia. Following the use of pneumococcal vaccination and prophylactic antibiotics, there were no additional cases of pneumonia and rates of colonization declined significantly.

Pneumonia in the elderly remains a significant and persistent public health problem. Rates of pneumonia increase significantly after age 65 (10-20 fold) and the mortality rate increases up to five times. Morbidity and prolonged recovery are the rule. Pneumococcal pneumonia is the most common bacterial pneumonia resulting in hospitalization. Mortality for bacteremic pneumonia remains at 25%. Drug-resistant pneumococcal disease is increasingly common throughout the United States with rates of both intermediate and highly resistant strains approaching 40-50% in some geographic regions.1-3 These organisms are frequently resistant not only to penicillin but to macrolides, cephalosporins, and trimethoprim-sulfamethoxazole combinations. Pneumoccal vaccination has been recognized as effective and cost effective in preventing pneumonia and mortality in the elderly, but rates of vaccination remain below one-third for eligible elderly patients. Recently, the Centers for Disease Control (CDC) reported on an outbreak of multidrug-resistant S. pneumoniae serotype 23F in a nursing home population in rural Oklahoma. In a group of 84 patients, only three had been vaccinated against pneumococcus. An epidemiologic investigation of both invasive infection and pneumococcal carriage was undertaken. A retrospective cohort study compared attack rates among colonized and non-colonized residents who had pneumonia and remained asymptomatic. The median age of the patient population was 85 and 92% were over age 65. Illness developed in 13%, all of whom had lobar consolidation on chest x-ray. Bacteremia resulted in death four three of four patients and only 4% had pneumococcal vaccination while 71% had received influenza vaccinations. The outbreak strain identified as S. pneumoniae serotype 23F was isolated in 23% of the residents (17 of 74) and two of 69 employees. Following the interventions, which included pneumococcal polysaccharide vaccination and penicillin 500 mg, three times per day; Ofloxacin 400 mg, twice per day for one week, the recovery of serotype 23F declined to only three residents and none of the employees. In the cohort study, colonization and attack rates were significantly higher among those taking antibiotics at the time of illness. Antecedent respiratory tract infection in the two weeks prior to illness was not associated with colonization. Invasive infection was more likely to develop in patients who had been hospitalized the previous year (relative risk of 3.3), who had pneumonia during the previous year (relative risk of 5.6), and who needed assistance with taking medications (relative risk of 3.7).

Comment by alan M. fein, MD

Pneumonia in the elderly remains a devastating problem despite the use of antibiotics. Interestingly, neither influenza vaccination nor pneumococcal vaccine which are both independently, effective in preventing pneumonia and co-morbid illness, are fully employed. Recent data from the CDC indicates that less than half of those eligible for influenza vaccination and less than one-third of those eligible for pneumococcal vaccination are receiving this intervention. These numbers may be higher in certain ethnic group, those with less access to medical care, or those with lower socioeconomic status. At the same time, these effective preventive strategies are not being employed and the use of antibiotics is increasing. This results in a rising prevalence of multidrug-resistant pneumococci which are often multidrug-resistant. In this study, all isolates had intermediate resistance to penicillin and cefotaxime, were resistant to trimethoprim-sulfamethoxazole and erythromycin, but were sensitive to vancomycin. The intervention that abruptly halted the epidemic included vaccination of patients and staff and the use of prophylactic antibiotics. This simple program proved highly effective in eliminating the carriage of the organism and the development of invasive disease. Drug-resistant pneumococcal infection is associated with extremes of age and the excessive use of antibiotics in patients who are often treated sporadically and empirically for respiratory infection. As in other studies, colonization by penicillin resistant S. pneumoniae was associated with multiple factors which, in addition to the use of antibiotics, may serve as surrogates for antibiotic use (i.e., hospitalization and having had pneumonia within the last year). This highly resistant strain (23F) was transmitted from person to person and, as suggested by its culture, from both patients and staff. Previous work has underscored the importance of pneumococcal vaccination in preventing the development of drug-resistant invasive infections. Most drug-resistant serotypes are included within the 23 valent vaccine and, as pointed out in this study, is a highly effective intervention. Even with reduced antibody response, it is highly cost effective.

In summary, pneumococcal disease remains a persistent risk to the elderly living at home and even more so in chronic care facilities. The importance of pneumococcal vaccination must be stressed given the high fatality once bacteremia or meningitis supervenes. Pneumonia in the elderly is both common and late to be recognized. The use of pneumococcal vaccination needs to be more effectively brought into the mainstream of preventive care.