Derepressed Transfer Properties Leading to the Efficient Spread of the Plasmid Encoding Carbapenemase OXA-48

Abstract

The current emergence of the carbapenemase OXA-48 among Enterobacteriaceae is related to the spread of a single IncL/M-type plasmid, pOXA-48a. This plasmid harbors the bla OXA-48 gene within a composite transposon, Tn1999, which is inserted into the tir gene, encoding a transfer inhibition protein. We showed that the insertion of Tn1999 into the tir gene was involved in a higher transfer frequency of plasmid pOXA-48a. This may likely be the key factor for the successful dissemination of this plasmid. P lasmids belonging to the IncL/M incompatibility group are commonly identified among environmental and clinical enterobacterial isolates (1-3). They have been increasingly identified as a source of multidrug resistance. Indeed, IncL/M-type plasmids are the main plasmids responsible for the dissemination of specific extended-spectrum ␤-lactamase genes such as the bla CTX-M-3 gene and have also been shown to harbor carbapenemase genes such as the bla NDM-1 and bla OXA-48 genes (4-6). OXA-48 carbapenemase is an Ambler class D ␤-lactamase that was first identified in 2001 from a multidrug-resistant Klebsiella pneumoniae isolate from Turkey (7). Many sporadic cases have been reported, first in Turkey and then in many other European countries and Israel (8-13). OXA-48 is now considered an endemic carbapenemase in Enterobacteriaceae, at least in Turkey and in North African countries such as Morocco, Algeria, and Tunisia, and a source of outbreak situations in France, Belgium, Spain, and the Netherlands (14-20). The spread of OXA-48 producers and of KPC producers represents the most important source of multidrug resistance in Europe and the United States. The spread of the bla OXA-48 gene is linked mostly to the dissemination of the single 62-kb IncL/Mtype plasmid pOXA-48a (20). Most of the OXA-48-positive Enterobacteriaceae harbor this specific plasmid, which is spreading among various enterobacterial species (20). Sequence analysis of plasmid pOXA-48a showed that the bla OXA-48 gene is bracketed by two copies of IS1999, giving rise to a composite transposon named Tn1999 (8, 21). Tn1999 is inserted into the tir gene, encoding a transfer inhibition protein, which is therefore not functional (6). Interestingly, a gene similar to this tir gene has been shown to inhibit plasmid RP4 conjugal transfer (22). Therefore, the aim of this study was to evaluate whether the disruption of the tir gene consecutive to the Tn1999 insertion in pOXA-48a could play a role in the dissemination of this plasmid and, consequently, of the bla OXA-48 gene. MATERIALS AND METHODSBacterial strains, plasmids, and culture conditions. Clinical strains K. pneumoniae 11978 (bla ) and K. pneumoniae 601 (bla NDM-1 ) were previously described (7,23). Escherichia coli TOP10(pOXA-48a) and E. coli TOP10(pNDM-OM), harboring the natural plasmids of K. pneumoniae 11978 and K. pneumoniae 601, respectively, were obtained by mating-out assays. Nalidixic acid-resistant E. coli JM109, nalidixic acidresistant Enterobacter cloacae SB, and rifampin-resistant E. coli TOP1...

Dissemination of multiresistant Enterobacter cloacae isolates producing OXA-48 and CTX-M-15 in a Spanish hospital

“…This might be in accordance with the high frequency of dissemination of the bla OXA-48 -carrying plasmid as previously demonstrated [14]. Isolates assigned to each profile as well as the hospital ward and building in which they were collected are shown.…”

Resistencia bacteriana a los antibióticos: una crisis global

“…Otro ejemplo es la diseminación mundial de la carbapenemasa OXA-48 40 , que, procedente del cromosoma de especies del género Shewanella, se relaciona con un determinado plásmido. Se ha demostrado que la inserción del transposón que contiene el gen de la OXA-48 en el gen tir (que codifica una proteína que inhibe la transferencia) hace que haya una mayor frecuencia de transferencia del plásmido, lo que contribuye a su diseminación 41 .…”

Molecular Characterization of Carbapenemase-Producing Escherichia coli and Klebsiella pneumoniae in the Countries of the Gulf Cooperation Council: Dominance of OXA-48 and NDM Producers

“…The primer pairs targeting IncL/M were used, and isolates negative for IncL/M were subsequently screened for IncA/C (Table 1). These two plasmid replicon types were selected based on reports suggesting dissemination of bla in IncL/M-and IncA/C-type plasmids (12,13).…”