Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2013

Study of ampC gene in clinical Stenotrophomonas maltophilia and determination of its expression level (#331)

Chong Seng Shit 1 , Rukman Awang Hamat 1 , Salasawati Hussin 2
  1. Universiti Putra Malaysia, Serdang, K.L, Malaysia
  2. Medical Microbiology and Immunology, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, K.L, Malaysia

A clinical strain of S. maltophilia exhibited resistant to a series of beta-lactams antibiotics including ceftazidime and cefepime was isolated from a tertiary hospital in Malaysia. Minimum Inhibitory Concentration value of ceftazidime and cefepime was determined by E-test strip and the result was 64mg/L and 48mg/L, respectively. However, the strain showed sensitive to co-trimioxazole and polymyxin-B. Thus, AmpC β-lactamase is suspected since ampC gene profile of S. maltophilia k279a is published in National Center for Biotechnology Information (NCBI) database. Sequencing result of ampC gene of clinical strain was examined with S. maltophilia ATCC 13637 and ten nucleotides changes were found. This ten nucleotides change causes switching in four amino acids sequence and this mutation might contribute to the ceftazidime and cefepime resistance. Hence, expression level of ampC gene was studied and found that the ampC gene of clinical strain was expressed 1.7-fold higher than S. maltophilia ATCC 13637. L1 and L2 β-lactamase genes were included and the expression level of these two genes was 1.03 and 0.97-fold, respectively. As a result, the clinical strain with high expression of ampC gene is believed to contribute the resistance to a series of beta-lactams antibiotics including ceftazidime and cefepime. Characterization of ampC gene will be carried on for kinetic assay study.