Emergence of NDM-1- and IMP-14a-producing Enterobacteriaceae in Thailand.
OBJECTIVE
To detect carbapenemases in clinical isolates of Enterobacteriaceae collected from patients in a university hospital in Thailand between October 2010 and August 2011.


METHODS
A total of 4818 Enterobacteriaceae isolates were screened for the presence of carbapenemases by ertapenem and imipenem disc diffusion tests. All positive screening isolates were subjected to modified Hodge test, phenylboronic acid- and EDTA-carbapenem combined disc tests and two multiplex PCRs of bla(IMP), bla(VIM), bla(SPM), bla(SIM) and bla(GIM), and of bla(KPC), bla(NDM) and bla(OXA-48). Carbapenemase-producing isolates were typed by PFGE and then characterized by antimicrobial susceptibility tests. Conjugation was performed using a broth culture mating method.


RESULTS
Two isolates each of Escherichia coli, Klebsiella pneumoniae and Citrobacter freundii produced NDM-1, whereas two other isolates of K. pneumoniae produced IMP-14a. DNA fingerprints revealed that the metallo-β-lactamase (MBL)-producing isolates were of different strains except for clonal strains of C. freundii. In vitro transfer of carbapenem resistance was successful for the eight MBL-producing isolates. All MBL producers were susceptible to colistin and tigecycline. The six NDM-producing isolates were recovered from the urine of three patients, who had no history of travel outside Thailand. Interestingly, one patient had chronic urinary tract infections caused by a K. pneumoniae strain and two strains of E. coli producing NDM-1.


CONCLUSIONS
Surveillance of carbapenemases, particularly NDM-1, in Enterobacteriaceae is urgently needed to control and prevent the spread of these resistance determinants in our country.
Graduate School,  Khon Kaen University, Khon Kaen 40002,  Thailand.
Benchamas
B
Rimrang
Aroonwadee
A
Chanawong
Aroonlug
A
Lulitanond
Chotechana
C
Wilailuckana
Nicha
N
Charoensri
Pipat
P
Sribenjalux
Waewta
W
Phumsrikaew
Lumyai
L
Wonglakorn
Anusak
A
Kerdsin
Ploenchan
P
Chetchotisakd
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D016521:Electrophoresis, Gel, Pulsed-Field; D004755:Enterobacteriaceae / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D004756:Enterobacteriaceae Infections / Q000145:classification / Q000235:genetics / Q000382:microbiology*; D000077727:Ertapenem; D006785:Hospitals, University; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000379:methods; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D013785:Thailand; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D047090:beta-Lactams; D015378:Imipenem; D001618:beta-Lactamases; C063912:carbapenemase; D000077727:Ertapenem