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Volume 42, Number 1, February 2009

First report on the occurrence of SHV-12 extended-spectrum β-lactamase–producing Enterobacteriaceae in the Philippines

Esperanza C. Cabrera, Roslyn D. M. Rodriguez
Department of Biology and Center for Natural Science and Ecological Research, De La Salle University; and Department of Laboratories, Philippine General Hospital, Manila, Philippines

Received: March 11, 2008    Revised: April 8, 2008    Accepted: August 13, 2008   


Corresponding author:

Dr. Esperanza C Cabrera, Department of Biology, De La Salle University, 2401 Taft Ave, Manila, Philippines 1004. E-mail: Esperanza C Cabrera This e-mail address is being protected from spam bots, you need JavaScript enabled to view it


Background and purpose: 

Soon after the introduction of extended-spectrum β-lactam antibiotics to treat infections caused by Gram-negative bacteria that were resistant to the existing β-lactams, resistant strains quickly emerged. This study investigated the antimicrobial susceptibility patterns, conjugative transferability, and molecular characterization of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae in the Philippines.



ESBL-producing Enterobacteriaceae were collected from patients at the Philippine General Hospital from June 2000 to August 2001. The antimicrobial susceptibility patterns were determined using the standard disk diffusion assay. ESBL production was confirmed using the double-disk synergy assay and the E-test, while the ESBLs were characterized for type using polymerase chain reaction, sequencing, and isoelectric focusing. Conjugation studies were conducted in vitro on solid medium.



All of the ESBL-producing isolates were also resistant to most other classes of antimicrobials studied. The ESBL genes on conjugative and non-conjugative plasmids were blaSHV-12. Fifteen isolates also carried blaTEM-1. None of the isolates were positive for the CTX-M type of ESBL. Plasmids from cefoxitin-resistant isolates did not produce amplified products using CMY primers for the AmpC gene.



SHV-12 is the dominating ESBL among the Enterobacteriaceae studied. The gene blaSHV-12 is carried together with genes for multiple resistance to other classes of antimicrobials in conjugative and nonconjugative plasmids.


Key words:

beta-Lactamase SHV-12; Conjugation, genetic; Drug resistance, microbial; Enterobacteriaceae; Isoelectric focusing



J Microbiol Immunol Infect. 2009;42:74-85.