Pseudomonas cepacia at Summer Camps for Persons with Cystic Fibrosis

Pseudomonas cepacia (PC) is a multidrug-resistant, gram-negative bacillus that causes chronic colonization and infection of the respiratory tract of persons with cystic fibrosis (CF). PC colonization is usually difficult to eradicate with antimicrobial therapy and, in some patients, infection is associated with rapid decline in pulmonary function, increased hospitalization, and earlier death (1-4). Previous studies have suggested person-to-person transmission of PC both within and outside of hospitals (2,3,5-7). However, possible transmission of PC at CF summer camps -- sites for physical and psychosocial therapy for many patients -- has not been well characterized. To assess the risk for PC transmission in this setting, in 1987 and 1990, the CF Foundation and CDC conducted epidemiologic investigations in four CF summer camps in Michigan, Ohio, Utah, and Ontario, Canada. This report summarizes the results of these studies. Michigan

In June 1987, 55 previously known PC-negative patients who were PC-culture negative immediately before attending camp attended a week-long CF camp with 36 other campers known to be colonized or infected with PC. The camp was staffed by 79 volunteer medical, paramedical, and laypersons who served as counselors and administered respiratory therapy and chest physiotherapy to campers. To determine the incidence of sputum conversion from PC-negative to PC-positive among campers, sputum or throat cultures were performed on all participants on arrival at, daily during, and within 3 months after camp.

To determine exposures of PC-negative campers to PC-positive patients or to particular camp staff and potential environmental sources of PC at camp, two investigators visually monitored campers' activities and administered a daily written questionnaire to each camper and/or the camper's counselor. None of the 55 CF campers with initially PC-negative sputum had PC-positive sputum cultures on departure from camp. However, five (9%) were PC-positive on their first follow-up culture within 2-13 weeks after camp. None were exposed to PC outside of the camp setting during this period. All five had reported close contact with PC-positive patients at camp, including participating in the same activities together for most of the day (four patients), hugging (three), lip-to-cheek kissing (one), and sharing toothpaste or finger food with (two) a PC-positive camper.

PC isolates from all five converters had the same ribotype (i.e., the restriction fragment-length polymorphism banding patterns were identical or had one- or two-band differences) as isolates from one or more PC-colonized campers and different from those of control isolates from other CF campers from other summer camps or CF centers. Of the five converters, three had PC with the same ribotype as that of isolates from PC-colonized campers with whom they had reported close contact.

Of 22 environmental cultures, three lake water samples grew PC. All three had an identical ribotype distinct from any of the PC isolates from campers. Ohio, Utah, and Ontario

From June through August 1990, a study was conducted at three CF summer camps attended by PC-negative and PC-positive patients in Ohio, Utah, and Ontario. Sputum or throat cultures were performed on campers on their arrival at camp, every 7 days until the end of camp, and 14-30 days after camp. To compare the incidence of sputum conversion from PC-negative to PC-positive of CF patients at camp with that outside of camp, sputum cultures were also performed on consenting noncamper CF patients who were known to be PC-negative and who, during the 2 weeks before camp, visited outpatient clinics or were hospitalized at the CF centers that the campers attended. The noncampers' sputum cultures were repeated 14-30 days after their corresponding CF-center summer camp ended.

Overall, of 191 CF patients who were PC-negative on arrival at camp, 181 completed their after-camp follow-up. Their cumulative incidence of PC sputum conversion was 11 (6%) of 181. The CF campers' risk for acquiring PC was approximately 12 times (Woolf's estimate of relative risk {RR}=11.7, lower 95% confidence limit=1.7) that of 92 noncamper controls, none of whom acquired PC during the study period. The increased risk for acquiring PC was not associated with older age or more severe underlying CF -- host factors that predispose CF patients to develop PC colonization. Compared with noncampers, PC-negative campers were younger and had milder CF. In addition, PC-negative campers and noncampers had similar sex distributions.

The risk for conversion to PC-positive was directly proportionate to the prevalence of PC-positive persons at camp: zero of 84 PC-negative campers in the Ohio camp (3% of attendees were PC-positive on entry); two (4%) of 47 PC-negative campers in the Utah camp (16% were positive on entry); and nine (18%) of 50 PC-negative campers in the Ontario camp (38% were PC-positive on entry) (p<0.001, chi-square test for linear trends). The risk for conversion also was increased in the camp with the longer duration: nine (18%) of 50 in the Ontario camp (duration: 4 weeks), compared with two (2%) of 131 in Ohio and Utah combined (duration for each: 1 week) (RR="11.8;" 95% CI="2.7-53.5)."

Risk-factor assessment based on daily (in Ohio and Utah) or weekly (in Ontario) written questionnaires indicated that the risk for sputum conversion was higher in those who reported sharing an eating utensil (RR=8.9; 95% CI=2.7-30.1), dancing (RR=4.2; 95% CI=1.2-15.4), or sleeping in the same cabin with a PC-positive camper (RR=3.7; 95% CI=1.1-12.3).

Of 11 campers whose sputum converted from PC-negative to PC-positive, nine had PC isolates with the same ribotype as that of PC isolates of other campers at their respective camps, and two had a common ribotype distinct from those of PC isolates of 33 known PC-positive persons in the same camp. Of the nine campers whose PC ribotypes matched those of other campers, four reported any contact with the campers whose isolates were of the same ribotype as theirs, including sleeping in the same cabin with and/or spending more than 4 hours per day in the company of a PC-positive camper.

Of 36 environmental cultures, one (ice water obtained from a picnic jug at the Utah camp) grew PC; this PC isolate had a distinct ribotype that differed from any of the PC isolates from Utah campers.

Reported by: R Honicky, MD, D Harden, MD, Michigan State Univ, East Lansing; J Hsu, MD, Children's Hospital of Detroit; W Howatt, MD, Univ of Michigan Univ Hospitals, Ann Arbor; L Kurlandsky, MD, Butterworth Hospital, Grand Rapids; D Homnick, MD, Michigan State Univ, Kalamazoo Center for Medical Studies. T Stull, MD, J LiPuma, MD, Medical College of Pennsylvania, Philadelphia. W Spohn, MD, Children's Medical Center, Dayton; K McCoy, MD, Columbus Children's Hospital; R Wilmott, MD, Children's Hospital Medical Center, Cincinnati. J Kanga, MD, Chandler Medical Center, Lexington, Kentucky. J Christenson, Univ of Utah School of Medicine, Salt Lake City. D Crozier, MD, Ontario Cystic Fibrosis Camp, J Reisman, MD, Hospital for Sick Children, Toronto; W Wilson, MD, McMaster Medical Center, Hamilton; E Eccelestone, MD, Children's Hospital of Western Ontario, London, Ontario; K Keeley, MD, Children's Hospital of Eastern Ontario, Ottawa. S FitzSimmons, PhD, R Beall, PhD, Cystic Fibrosis Foundation, Bethesda, Maryland. Hospital Infections Program, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Studies to determine the risk for and mechanisms of PC acquisition by CF patients have been limited by the unknown sensitivity of sputum or throat cultures in detecting PC in the CF patient's respiratory tract and, consequently, by the difficulty in determining when PC is acquired by the patient. Despite these limitations, the epidemiologic and laboratory findings in this report suggest that PC can be acquired at CF summer camps, and person-to-person transmission is a likely mode of spread. Factors that may have contributed to an increased risk for PC acquisition at the camps include a high prevalence of PC-positive CF campers (greater than 5%) or prolonged (greater than 1 week) duration of camp, probably reflecting increased opportunity for frequent, close, and prolonged contact between campers.

The degree to which contact-isolation precautions (i.e., handwashing, gloving, gowning, cohorting of CF patients by their PC-colonization status, and discarding contaminated articles) (8) were followed at each camp in this report was not assessed; therefore, the impact of recommended precautions for preventing nosocomially acquired PC at camp is unknown. In CF camps where transmission of PC has been suspected or where the prevalence of PC-positive campers exceeds 5%, and/or camp duration is longer than 1 week, camp personnel should either fully implement contact-isolation precautions at the camp or prohibit PC-positive and PC-negative CF patients from attending camp together (8). In areas with a high prevalence of PC-positive patients, separate CF summer camps for PC-positive and PC-negative patients may be feasible.

These recommendations are dependent on adequate procedures for screening patients before camp. Therefore, sputum or throat cultures should be appropriately collected from patients with CF and transported to and processed in a laboratory that routinely uses PC-selective media and by personnel who are proficient in isolating and identifying PC from sputum of patients with CF (9).

References

1. Isles A, Maclusky I, Corey M, et al. Pseudomonas cepacia infection in cystic fibrosis patients: an emerging problem. J Pediatr 1984;104:206-10.

2. Tablan OC, Chorba TL, Schidlow DV, et al. Pseudomonas cepacia colonization in patients with cystic fibrosis: risk factors and clinical outcome. J Pediatr 1985;107:382-7.

3. Tablan OC, Martone WJ, Doershuk CF, et al. Colonization of the respiratory tract with Pseudomonas cepacia in cystic fibrosis: risk factors and outcomes. Chest 1987;91:527-32.

4. Lewin LO, Byard PJ, Davis PB. Effect of Pseudomonas cepacia colonization on survival and pulmonary function of cystic fibrosis patients. J Clin Epidemiol 1990;43:125-31.

5. LiPuma JJ, Dasen TD, Nielson DW, Stern RC, Stull TL. Person-to-person transmission of Pseudomonas cepacia between patients with cystic fibrosis. Lancet 1990;336:1094-6.

6. Thomassen MJ, Demko CA, Doershuk CF, Stern RC, Klinger JD. Pseudomonas cepacia: decrease in colonization in cystic fibrosis patients. Am Rev Respir Dis 1986;134:669-71.

7. Burdge DR, Nakielna EM, Noble MA. Case-control and vector studies of nosocomial acquisition of Pseudomonas cepacia by adult patients with cystic fibrosis. Infect Control Hosp Epidemiol 1993;14:127-30.

8. Garner JS, Simmons BP. Guideline for isolation precautions in hospitals. Infect Control 1983;4(suppl):245-325.

9. Tablan OC, Carson LA, Cusick LB, Bland LA, Martone WJ. Use of selective media in isolating Pseudomonas cepacia from simulated sputum specimens of cystic fibrosis patients: results of laboratory proficiency tests. J Clin Microbiol 1987;25:485-7.

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