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Abstract - Expansion of plasmid mediated blaACT-2 among Pseudomonas aeruginosa associated with postoperative infection and its transcriptional response under cephalosporin stress.
Birson Ingti, Deepjyoti Paul, Anand Prakash Maurya, Debajyoti Bora, Debadatta Dhar (Chanda), Atanu Chakravarty, Amitabha Bhattacharjee

Expansion of plasmid mediated blaACT-2 among Pseudomonas aeruginosa associated with hospital infection and its transcriptional response under cephalosporin stress

Birson Ingti1, Deepjyoti Paul1, Anand Prakash Maurya1, Debajyoti Bora3, Debadatta Dhar (Chanda)2, Atanu Chakravarty2, Amitabha Bhattacharjee1

1Department of Microbiology, Assam University, Silchar, India

2Department of Microbiology, Silchar Medical College and Hospital, Silchar, India

3Department of Statistics, Dibrugarh University, Dibrugarh, India


Objectives: Organisms harboring multiple plasmid mediated β-lactamases are major concerns in nosocomial infections. Among these plasmid mediated β-lactamases, ACT (EBC family) is a clinically important enzyme capable of hydrolyzing broad spectrum cephalosporins. Therefore, the present study was undertaken to determine the prevalence of ACT determinant along with other co-existing β-lactamase genes in P. aeruginosa strains.

Methods: A total of 176 Pseudomonas isolates were phenotypically screened for the presence of AmpC β-lactamase by M3DET Method followed by Molecular detection using PCR assay. Transcriptional evaluation of blaACT-2 gene was analyzed by RT-PCR and its transferability was performed by transformation and conjugation.

Results: Present study demonstrates the presence of ACT-2 allele among 12 strains of P. aeruginosa. Co-existence of other β-lactamase genes were encountered among ACT-2 harboring strains which includes CTX-M (n=2), SHV (n=3), TEM (n=2), VEB (n=2), OXA-10 (n=1), CIT (n=2) and DHA (n=3). Fingerprinting by REP PCR revealed the isolates harboring ACT-2 to be distinct and these isolates showed high resistance to expanded-spectrum cephalosporins and even to carbapenem group of drugs. This ACT-2 allele was encoded in the plasmid (L/M, FIA, FIB Inc group) and conjugatively transferable. Transcriptional analysis revealed a significant increase in ACT-2 expression (483 fold) when induced by ceftriaxone at 4 µg/ml followed by ceftazidime at 8 µg/ml (31 fold) and cefotaxime 4 µg/ml (8 fold).

Conclusion: In this study detection of ACT-2 plasmid mediated AmpC β-lactamase along with other β-lactamase genes in clinical isolates of P. aeruginosa represents a serious therapeutic challenge. Therefore, revision in antimicrobial policy is required for effective treatment of patients infected with pathogen expressing this mechanism.  J Microbiol Infect Dis 2017; 7(2): 75-82

Keywords: Plasmid mediated, ACT-2 β-lactamase, P. aeruginosa

Volume 07, Number 02 (2017)