1428. Genetic Diversity of Multi-Drug Resistant Pseudomonas aeruginosa In a Patient, In a Ward and In a Hospital
Session: Poster Abstract Session: Epidemiology of Multiple Drug-Resistant Gram Negative Rods
Saturday, October 20, 2012
Room: SDCC Poster Hall F-H
Background: Multidrug-resistant Pseudomonas aeruginosa(MDRPA) is one of the cause of troublesome nosocomial infections. Although the mechanisms for multidrug-resistance(MDR) have been demonstrated over years, the precise mechanisms focused on each patients are poorly understood. In this study, we demonstrated the diversity of MDRPA resistant pattern isolated from hospitalized patients in a university hospital.

Methods: MDR was defined as triple antibiotic resistance (i.e., carbapenems, fluoroquinolones, and aminoglycosides), and pre-MDRPA was defined as two kinds of aforementioned antibiotic resistance. All patients isolated both MDRPA and pre-MDRPA in 2008 and all strains of Pseudomonas aeruginosa isolated from those patients were listed. MIC determination, Amp C and metallo-beta lactamases;MBLs detection, PFGE, and MLST of each strain were performed and compared against the clinical antibiotic treatment course.

Results: Totally 58 strains were isolated from 10 patients harboring both MDRPA and pre-MDRPA. PFGE pattern revealed 17 pulsotypes, and MBL and AmpC detection rate were 24 and 43%, and the prevalence of MDRPA and pre-MDRPA were 19 and 47%, respectively. The highest number of isolation from one patient was 24 strains. From the timeline of the isolation of resistant strain and antibiotic treatment, cephalosporin use might be closely-involved in Amp C detection, however, antibiotic sensitivities were back-and-forth between sensitive and resistant in same individual. PFGE analysis revealed different clones and same clones with different sensitivity patterns identified in one specimen from same individual. Surprisingly, appearance of the colonies of different PFGE types with different sensitivities were quite similar, which indicates clinical sensitivity results might be influenced by coincidental selection of either sensitive or resistant strains at the time of picking colony.

Conclusion: Our results indicated the diversity of MDRPA, possible co-existence of different clones and same clones in a patient, spreading in a ward and in a hospital. For the clinical impact, we might need to pay attention to the sensitivity results of clinical isolates, which might be just one of the results of resistant reservoir. In the presentation, MLST type of the resistant strains is also demonstrated.

Sadako Yoshizawa, MD, PhD1, Yuichi Kouyama2, Ryuuji Sakata3, Tomoo Saga, M.D., Ph.D2, Yoshikazu Ishii, Ph.D.2 and Kazuhiro Tateda, M.D, Ph.D2, (1)Toho University School of medicine, Tokyo, Japan, (2)Department of Microbiology and Infectious Diseases, Toho University School of Medicine, Tokyo, Japan, (3)Toho University School of Medicine, Tokyo, Japan


S. Yoshizawa, None

Y. Kouyama, None

R. Sakata, None

T. Saga, None

Y. Ishii, None

K. Tateda, None

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