Anaïs Potron

OXA-48-like carbapenemases: the phantom menace

OXA-48-type carbapenem-hydrolysing class D β-lactamases are increasingly reported in enterobacterial species. To date, six OXA-48-like variants have been identified, with OXA-48 being the most widespread. They differ by a few amino acid substitutions or deletions (one to five amino acids). The enzymes hydrolyse penicillins at a high level and carbapenems at a low level, sparing broad-spectrum cephalosporins, and are not susceptible to β-lactamase inhibitors. When combining permeability defects, OXA-48-like producers may exhibit a high level of resistance to carbapenems. OXA-163 is an exception, hydrolysing broad-spectrum cephalosporins but carbapenems at a very low level, and being susceptible to β-lactamase inhibitors. The bla(OXA-48)-type genes are always plasmid-borne and have been identified in association with insertion sequences involved in their acquisition and expression. The current spread of the bla(OXA-48) gene is mostly linked to the dissemination of a single IncL/M-type self-transferable plasmid of 62 kb that does not carry any additional resistance gene. OXA-48-type carbapenemases have been identified mainly from North African countries, the Middle East, Turkey and India, those areas constituting the most important reservoirs; however, occurrence of OXA-48 producers in European countries is now well documented, with some reported hospital outbreaks. Since many OXA-48-like producers do not exhibit resistance to broad-spectrum cephalosporins, or only decreased susceptibility to carbapenems, their recognition and detection can be challenging. Adequate screening and detection methods are therefore required to prevent and control their dissemination.

Characterization of OXA-204, a Carbapenem-Hydrolyzing Class D β-Lactamase from Klebsiella pneumoniae

ABSTRACT Klebsiella pneumoniae KP3 was isolated from a patient transferred from India to the Sultanate of Oman. K. pneumoniae KP3 was resistant to all β-lactams, including carbapenems, and expressed the carbapenem-hydrolyzing β-lactamase OXA-181, which differs from OXA-48 by four amino acid substitutions. Compared to OXA-48, OXA-181 possessed a very similar hydrolytic profile. The blaOXA-181 gene was located on a 7.6-kb ColE-type plasmid and was linked to the insertion sequence ISEcp1. The ISEcp1-mediated one-ended transposition of blaOXA-181 was also demonstrated.

Origin of OXA-181, an Emerging Carbapenem-Hydrolyzing Oxacillinase, as a Chromosomal Gene in Shewanella xiamenensis

ABSTRACT Plasmid-mediated carbapenem-hydrolyzing β-lactamases are becoming emerging threats with Enterobacteriaceae. In particular, the carbapenem-hydrolyzing class D β-lactamase OXA-48 and its derivative OXA-181 have been reported increasingly worldwide. Using a PCR-based strategy, environmental samples were screened for blaOXA-48-like genes. Shewanella xiamenensis, an environmental species from marine and freshwater, was identified as the progenitor of the blaOXA-181 gene. This work identifies the reservoir of an emerging carbapenemase gene that is clinically significant.

Genetic and biochemical characterisation of OXA-232, a carbapenem-hydrolysing class D β-lactamase from Enterobacteriaceae.

Three enterobacterial isolates (two Klebsiella pneumoniae and one Escherichia coli) were recovered from three patients transferred from India to France in 2011. All three isolates were resistant or of intermediate susceptibility to all β-lactams and of decreased susceptibility to carbapenems. These three isolates expressed a novel carbapenem-hydrolysing β-lactamase, OXA-232, differing from OXA-181 and OXA-48 by one and five amino acid substitutions, respectively. Compared with OXA-181, OXA-232 had a lower ability to hydrolyse carbapenems but conversely possessed higher hydrolytic activities against penicillins. The bla(OXA-232) gene was located on a 6.1-kb ColE-type non-conjugative plasmid.

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 blaOXA-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.

Plasmid-mediated transfer of the blaNDM-1 gene in Gram-negative rods

The latest threat of multidrug-resistant Gram-negative bacteria corresponds to the emergence of carbapenemase NDM-1 (New Delhi metallo-β-lactamase) producers, mostly in Enterobacteriacae. Five bla(NDM) (-1) -positive plasmids of different incompatibility groups (IncL/M, FII, A/C and two untypeable plasmids) from clinical Enterobacteriaceae were evaluated for conjugation properties and host specificity. Successful conjugative transfers were obtained using all tested enterobacterial species as recipients (Escherichia coli, Klebsiella pneumoniae, Salmonella typhimurium and Proteus mirabilis) and all plasmid types. Conjugation frequencies varied from 1 × 10(-4) to 6 × 10(-8) transconjugants per donor. Higher conjugation rates were obtained for two plasmids at 30 °C compared with that observed at 25 and 37 °C. Carbapenems used as selector did not lead to higher conjugation frequencies. None of the five plasmids was transferable to Acinetobacter baumannii or Pseudomonas aeruginosa by conjugation. This work underlines how efficient the spread of the carbapenemase bla(NDM) (-1) gene could be among Enterobacteriaceae.

PER-7, an Extended-Spectrum β-Lactamase with Increased Activity toward Broad-Spectrum Cephalosporins in Acinetobacter baumannii

ABSTRACT Acinetobacter baumannii isolate AP2 was recovered from a bronchial lavage sample of a patient hospitalized in Paris, France. A. baumannii AP2 was resistant to all β-lactams, including carbapenems, and expressed the extended-spectrum β-lactamase (ESBL) PER-7, which differs from PER-1 by 4 amino acid substitutions. Compared to PER-1, PER-7 possessed higher-level hydrolytic activities against cephalosporins and aztreonam. The blaPER-7 gene was chromosomally located and associated with a mosaic class 1 integron structure. Additionally, isolate AP2 expressed the carbapenem-hydrolyzing oxacillinase OXA-23 and the 16S RNA methylase ArmA, conferring high-level resistance to aminoglycosides.

Wild Coastline Birds as Reservoirs of Broad-Spectrum-β-Lactamase-Producing Enterobacteriaceae in Miami Beach, Florida

ABSTRACT A high rate of broad-spectrum-β-lactamase-producing Escherichia coli isolates was identified from seagull and pelican feces collected in the Miami Beach, Florida, area. The most commonly identified resistance determinants were CMY-2 and CTX-M-15. Those wild birds might be therefore considered vehicles for wide dissemination of multidrug-resistant Enterobacteriaceae in the United States.

Occurrence of the Carbapenem-Hydrolyzing β-Lactamase Gene blaOXA-48 in the Environment in Morocco

The bla OXA-48 gene is plasmid borne and encodes a carbapenem-hydrolyzing class D β-lactamase that was first identified in a Klebsiella pneumoniae clinical isolate in Turkey in 2004 ([11][1]). The high prevalence of OXA-48 producers in Turkey is well established ([3][2]), but there are also

Genetic and Biochemical Characterization of the First Extended-Spectrum CARB-Type ß-Lactamase, RTG-4, from Acinetobacter baumannii

ABSTRACT Acinetobacter baumannii isolate KAR was uncommonly more resistant to cefepime and cefpirome than to ceftazidime and cefotaxime. Cloning and expression of the β-lactamase gene content of this isolate into Escherichia coli TOP10 identified ß-lactamase RTG-4 (or CARB-10), which corresponds to the first reported extended-spectrum CARB-type enzyme. RTG-4 is a plasmid-encoded Ambler class A β-lactamase whose sequence differs by 4 amino acid substitutions from the narrow-spectrum β-lactamase RTG-3. RTG-4 hydrolyzes cefepime and cefpirome and weakly hydrolyzes ceftazidime due to the single Ser-to-Thr substitution at Ambler position 69. RTG-4 is less susceptible to inhibition by tazobactam and sulbactam than RTG-3. Expression of β-lactamase RTG-4 in a wild-type A. baumannii reference strain showed that it conferred resistance to cefepime and cefpirome. The genetic environment of the blaRTG-4 gene was made of a peculiar transposon located on a ca. 50-kb plasmid. ISAba9, located upstream of blaRTG-4, may be responsible for its acquisition by recognizing a secondary right inverted repeat sequence, thus acting by a one-ended transposition process.