Jpn. J. Infect. Dis., 57, 226-228, 2004

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Laboratory and Epidemiology Communications

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus, Pseudomonas aeruginosa and Serratia marcescens in a Long-Term Care Facility for Patients with Severe Motor and Intellectual Disabilities

Teruo Kirikae1, Osamu Tokunaga, Yasuhiro Inoue, Tomoko Fujino1, Katsutoshi Saruta1, Hiroshi Yoshikura2, Tadatoshi Kuratsuji1 and Takeshi Miyanomae*

Department of Pediatrics, Minami-Kyoto Hospital, National Hospital Organization, Kyoto 610-0113, 1Department of Infectious Diseases and Tropical Medicine, International Medical Center of Japan, Tokyo 162-8655 and 2National Institute of Infectious Diseases, Tokyo 162-8640, Japan

Communicated by Yoshichika Arakawa

(Accepted September 22, 2004)


*Corresponding author: Mailing address: Department of Pediatrics, Minami-Kyoto Hospital, National Hospital Organization, Naka-ashihara 11, Johyoh-shi, Kyoto 610-0113, Japan. Fax: +81-774-55-2765, E-mail: miyanomt@skyoto.hosp.go.jp


Assessing the risk of nosocomial infection is necessary for optimizing the quality of patient care and the practice of infection control in long-term care facilities for patients with severe motor and intellectual disabilities (SMID). We conducted a molecular epidemiological study of pathogens in December 2002 and August 2003 in two wards of such a facility having three wards. Among the 39 inpatients in the wards, 20 had tracheotomy or were cared for with mechanical ventilators. The isolates were tested for chromosomal DNA typing by using a contour-clamped homogeneous electric field system (CHEF MapperTM: Bio-Rad Laboratories, Hercules, Calif., USA).

In December 2002, 14 of 20 patients carried at least one methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Serratia marcescens strain (Table 1). MRSA was isolated from 11 specimens from 9 patients, including eight patients' sputa, one patient's abscess, and one patient's eye mucus. Among these, two were obtained on different days from an abscess of patient P5 and two others from different sites of patient P7. P. aeruginosa was obtained from nine patients' sputa and S. marcescens from five patients' sputa. Three patients, P1, P4, and P6, carried MRSA, P. aeruginosa, and S. marcescens in the same specimen, and the other three patients, P3, P7, and P5, carried MRSA and P. aeruginosa.

The survey was repeated in August 2003. Eighteen patients carried at least one MRSA, P. aeruginosa, or S. marcescens strain (Table 1). MRSA strains were isolated from six patients, including four patients' sputa and two patients' urine. P. aeruginosa was isolated from 13 patients' sputa, and S. marcescens from three patients' sputa. No patient simultaneously carried MRSA, P. aeruginosa, and S. marcescens strains. Only one patient, P15, had both MRSA and P. aeruginosa, and two patients, P1 and P11, had P.aeruginosa and S. marcescens. Nine patients, P1, P2, P3, P4, P7, P8, P11, P13, and P14, carried MRSA, and either P. aeruginosa or S. marcescens both in December 2002 and in August 2003.

The PFGE patterns of these MRSA isolates are shown in Fig. 1A. From a total of 17 isolates, 12 different PFGE patterns were detected. Band-based cluster analysis of these patterns (Molecular AnalystTM: Bio-Rad) revealed a cluster consisting of patterns A1, A3, and A16 (Fig. 1B) (patterns sharing a similarity of 70% or higher were grouped into a cluster). No other clustering was not observed.

Among 11 MRSA isolates found in December 2002, there were two clusters, one consisting of three isolates of PFGE pattern A3 and the other of three isolates of pattern BM. In contrast, in six isolates found in August 2003, clustering was not detected (Table 1). The PFGE patterns obtained from this study were compared with those identified in previous studies conducted in 2000-2003 in Tokyo (1-4), in 2002-2003 in Kumamoto (5-7), and in 2003 in Sendai (8). Among the patterns detected in the present study, pattern A1 was detected in 2000-2003 both in Tokyo and Kumamoto; pattern A3 in 2000-2003 in Tokyo and in 2003 in Sendai; and pattern A16 in 2001 and 2002 in Tokyo. The other nine patterns we identified were not detected in the previous studies.

The PFGE patterns of P. aeruginosa isolates are shown in Fig 2A. From a total of 22 isolates, 19 different PFGE patterns were detected. Band-based cluster analysis of these patterns revealed six clusters, A, C, E, G, I, and J (Fig 2B). The isolates from patients P19 and P22 in August 2003 were of the same pattern, P.J1. The isolates in December 2002 and August 2003 from patient P7 were of the same pattern P.A1, and those from patients P11 in the two surveys were also of the same pattern P.G2.

A total eight S. marcescens isolates were obtained. These represented three different PFGE patterns (Fig. 3A), two of which were similar to each other (Fig. 3A, 3B). Three of five isolates found in December and all of the three isolates found in August were of pattern S.A1.

Comparison of the August 2003 data with December 2002 data clearly shows reduction of MRSA carriers and disappearance of genetically related MRSA clusters in the second survey. Probably interventions taken after the first survey reduced MRSA transmission among the inpatients. The interventions taken were i) an educational program for the ward staff that dealt with infection control practice, ii) promotion of compliance with hand washing, and iii) replacement of the multi-use catheter with the sterile single-use catheter for suction of respiratory tract secretions. The data also suggested that the above interventions were not as successful for control of P. aeruginosa and S. marcescens that were present in the environment of the facility.

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