NEW YORK (Reuters Health) - Pneumococci tolerant to vancomycin appear to be relatively widespread, and based on a study of patients with meningitis, tolerant organisms are more virulent than nontolerant isolates, according to a paper in the October 15th issue of the Journal of Infectious Diseases.
Tolerance changes the activity of an antibiotic from bactericidal to bacteriostatic, Dr. Elaine I. Tuomanen and her colleagues explain, and cannot be overcome by increasing antibiotic concentration. The antibiotic is less lethal to tolerant bacteria, which can resume growth when the antibiotic is removed.
Dr. Tuomanen’s group found that of 113 isolates of Streptococcus pneumoniae obtained from patients with meningitis in 1998, 11 (9.7%) were tolerant to vancomycin. Thirty-day survival was only 49% among those harboring tolerant pneumococci, compared with 86.4% of those infected with nontolerant bacteria (p = 0.048).
Dr. Tuomanen, at St. Jude Children’s Research Hospital in Memphis, Tennessee, and her group also analyzed archival samples of 215 nasopharyngeal isolates from 54 healthy infants obtained in 1998. Eight isolates (3.7%) were tolerant to vancomycin.
And in a prospective study, nasopharyngeal swabs were obtained from 415 infants who were followed from 1999 through 2002. The pneumococcal carriage rate was 28.6%, with tolerance to vancomycin documented in 8.1%.
The researchers observed that tolerant bacteria were obtained days to weeks before or after nontolerant organisms were isolated from the same subjects, and from diverse clonal origins.
Tolerance to vancomycin was highly correlated with resistance to other antibiotics, including beta-lactams, sulfonamides, and erythromycin. And in fact, tolerance was three times more likely in bacteria isolated from the 21 subjects who had been treated with antibiotics during the previous 2 weeks, suggesting “the need to address a possible cause-and-effect relationship for tolerance as well,” the authors maintain.
Source: J Infect Dis 2004;190:1481-1487. [ Google search on this article ]
MeSH Headings:Biological Phenomena: Biological Phenomena, Cell Phenomena, and Immunity: Biological Sciences: Biology: Drug Resistance, Microbial: Genetics: Genetics, Microbial: Microbiologic Phenomena: Pharmacogenetics: Drug Resistance, Multiple: Vancomycin Resistance: Biological SciencesCopyright © 2002 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.
