Metallo-beta-lactamase-producing Pseudomonas putida as a reservoir of multidrug resistance elements that can be transferred to successful Pseudomonas aeruginosa clones.
OBJECTIVE
To study the prevalence, nature, involved genetic elements and epidemiology of metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa and Pseudomonas putida isolated in a Spanish hospital between 2005 and 2008.


METHODS
Etests were used for susceptibility testing and screening for MBLs, confirmed through bla(VIM) PCRs and sequencing. Clonal relatedness was evaluated by PFGE and multilocus sequence typing (MLST). MBL-carrying plasmids were characterized by restriction fragment length polymorphism, Southern blot and electroporation. MBL genetic elements were studied by cloning and sequencing.


RESULTS
MBL-producing P. putida was detected in eight patients (one clone each; two harbouring bla(VIM-1) and six harbouring bla(VIM-2)), representing 14% of all the infections by the P. putida/fluorescens group. MBLs were detected in only 0.3% of P. aeruginosa infections (11 patients) during the same period. PFGE revealed four P. aeruginosa clones: one producing bla(VIM-13) (two patients); and three producing bla(VIM-2) (two patients, six patients and one patient, respectively). MLST indicated that the VIM-13 clone was the internationally spread sequence type (ST)235, while the major VIM-2 lineage corresponded to ST179, which is associated with chronic respiratory infections. The VIM-1 integron was shown to have both plasmid and chromosomal location, while the VIM-13 integron was only chromosomal. The VIM-2 integron was located in the same transposon (Tn402/Tn5053-like) in all P. aeruginosa and P. putida isolates, suggesting its crucial role in the dissemination of VIM-2.


CONCLUSIONS
The high diversity and proportion of MBL-positive P. putida suggests an environmental reservoir of these resistance determinants. Dissemination of these multidrug resistance elements to successful P. aeruginosa clones presents a major epidemiological and clinical threat.
Juan
Carlos
C
Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Institut Universitari de Investigació en Ciències de la Salut (IUNICS), Palma de Mallorca, Spain. carlos.juan@ssib.es
Zamorano
Laura
L
Mena
Ana
A
Albertí
Sebastián
S
Pérez
Jose Luis
JL
Oliver
Antonio
A
D015373:Bacterial Typing Techniques; D015139:Blotting, Southern; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D022761:Gene Transfer, Horizontal; D005838:Genotype; D006761:Hospitals; D006801:Humans; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010957:Plasmids; D011110:Polymorphism, Genetic; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D016958:Pseudomonas putida / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D013030:Spain / Q000453:epidemiology; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
D004269:DNA, Bacterial; D001618:beta-Lactamases