Molecular Epidemiology of Stenotrophomonas maltophilia Isolated from Clinical Specimens from Patients with Cystic Fibrosis and Associated Environmental Samples

Abstract

Stenotrophomonas maltophilia was isolated from the respiratory tracts of 41 (25%) of 163 children attending our pediatric cystic fibrosis unit between September 1993 and December 1995. The extents of S. maltophilia contamination of environmental sites frequented by these patients were investigated with a selective medium incorporating vancomycin, imipenem, and amphotericin B. Eighty-two isolates of S. maltophilia were cultured from 67 different environmental sites sampled between January and July 1996. The organism was widespread in the home environment, with 20 (36%) and 25 (42%) of sampled sites positive in the homes of colonized and noncolonized patients, respectively. In the nosocomial setting, it was isolated from 18 (32%) sites in the hospital ward and from 4 (17%) sites in the outpatient clinic area. The most common sites of contamination were sink drains, faucets, and other items frequently in contact with water. All environmental and clinical isolates were genotyped with enterobacterial repetitive intergenic consensus sequences as primers. A total of 33 of the 41 patients were colonized with unique strains, and four pairs of patients shared strains. Further characterization by pulsed-field gel electrophoresis after digestion with XbaI found that there was no evidence of patient-to-patient transmission; however, there was some evidence that a small number of patients may have acquired the organism from the hospital environment. Resampling of environmental sites in the hospital ward in January 1997 revealed evidence of genetic drift, complicating the accurate determination of environmental sources for clinical strains. The source of the majority of S. maltophiliastrains colonizing the respiratory tracts of these patients with cystic fibrosis remained uncertain but may have represented multiple, independent acquisitions from a variety of environmental sites both within and outside the hospital.

The Changing Microbial Epidemiology in Cystic Fibrosis

“…Several studies reported that the incidence of S. maltophilia infection in CF has also increased in recent years (16,85,195,305). Data from the CFF Patient Registry support this, indicating that the prevalence of S. maltophilia increased from 4.0% in 1996 to 12.4% in 2005, with the highest rates of infection (15.8% in 2005) occurring for adolescents 11 to 17 years old (72,249).…”

“…The inappropriate use of hand moisturizing lotion instead of soap by a health care worker was associated with infection among bone marrow transplant recipients in one center (159), while in another center, contamination of faucet aerators in intensive care unit sinks was implicated as the source of S. maltophilia infection (343). Other studies also reported the recovery of this species from hospital sink drains, faucets, and potable water (84,85). However, genotyping analyses typically have not provided a link between isolates obtained from such hospital environmental sources and those recovered from patients (84,197).…”

“…Denton and colleagues (85) found that 33 of 41 S. maltophilia-infected CF patients in one treatment center harbored genetically distinct strains; four pairs of patients shared strains, suggesting either interpatient spread or acquisition from a common environmental site. Krzewinski and colleagues (166) analyzed S. maltophilia isolates from 183 infected CF patients from multiple centers and found only three instances of shared strains.…”

Cleaning and decontamination of the healthcare environment

“…demonstrate long-term persistence within biofi lm adherent to hospital plumbing components and other water-exposed sites. 14,15 Most respiratory viruses such as coronavirus, rhinovirus and infl uenza can survive on dry surfaces for a few days, with gastrointestinal viruses retaining viability for a couple of months. Norovirus is found in the hospital environment for days after an outbreak, demonstrating survivability despite terminal cleaning with bleach-based products.…”

“…and Stenotrophomonas are associated with damp places such as taps, sinks, showers and baths. 1,13,15,26,27 Coliforms such as Klebsiella and Serratia have been identifi ed from buckets, bowls, mops and liquids. 1,28 Thus, traditional sites for Gram-negative microbes have been sites constantly or intermittently exposed to water, but this is not always the case.…”