The nature of the genetic determinant for the SHV-1 β-lactamase

188

125

Over a 12-year period (1989 to 2000), 159 Klebsiella pneumoniae isolates harboring extended-spectrum ␤-lactamases (ESBLs) (4.8% of the total number of K. pneumoniae isolates obtained) were recovered from 58 patients, who were mainly hospitalized in intensive care and surgery units. For 62 representative isolates from 58 patients, 31 clonal types harboring TEM-4 (n ‫؍‬ 5), SHV-2 (n ‫؍‬ 7), SHV2a (n ‫؍‬ 4), SHV-5 (n ‫؍‬ 1), CTX-M-10 (n ‫؍‬ 13), or CTX-M-9 (n ‫؍‬ 1) ␤-lactamases were identified by pulsed-field gel electrophoresis. This is the first report to document the presence of the CTX-M-10 or the CTX-M-9 ␤-lactamase in K. pneumoniae. These ␤-lactamases were previously identified in Escherichia coli isolates from Spain. Only two of five K. pneumoniae TEM-4 clones caused more than a single case of infection, with one of them spreading for 9 months. A single plasmid was detected among these TEM-4 clones. Only two of seven K. pneumoniae clones containing SHV-2 and three of four strains harboring SHV-2a were detected in more than one case of infection. Plasmids encoding SHV-2 or SHV-2a were unrelated. Four of 13 K. pneumoniae CTX-M-10 clones were found in more than one patient, with two of them recovered 2 and 5 years apart. As in the case of the SHV-2 isolates, we were unable to document a common transmissible genetic element that could explain the polyclonal structure of our isolates. Nevertheless, the spread of a single gene may be suggested by the presence of a conserved set of noncoding polymorphisms in the sequences. Most ESBL-producing K. pneumoniae clones were ephemeral, being poorly selected and maintained in the hospital setting, but the genes encoding ESBL persisted successfully over the years that the strains were recovered, probably as a minority gene population in the hospital metagenome.

Section: Discussionmentioning

confidence: 99%

Genes Encoding TEM-4, SHV-2, and CTX-M-10 Extended-Spectrum β-Lactamases Are Carried by MultipleKlebsiella pneumoniaeClones in a Single Hospital (Madrid, 1989 to 2000)

Coque

Oliver

Pérez-Díaz

et al. 2002

188

125

“…Purification and further biochemical studies indicated that SHV-type P-lactamases have a wide spectrum of hydrolytic activity towards penicillins and cephalosporins (4). SHV-1 has been associated with an uncharacterized transposon of 14.25 kilobases (kb) (29).…”

mentioning

confidence: 99%

Cloning of SHV-2, OHIO-1, and OXA-6 beta-lactamases and cloning and sequencing of SHV-1 beta-lactamase

Mercier

Levesque

1990

Molecular cloning of DNA fragments permitted the isolation of structural genes coding for SHV-1, SHV-2, OHIO-1, and OXA-6 1-lactamases. DNA probes were constructed for SHV-1, and under conditions of high stringency, hybridization was observed only between SHV-1 and SHV-2. Oligonucleotide typing with a 15-mer SHV-1 probe was capable of discriminating between SHV-1 and SHV-2 but not OHIO-1. The nucleotide sequence of the SHV-1 P-lactamase gene from plasmid R974 has been determined. The structural gene encodes a polypeptide product which differs by 9 residues from the p453 (SHV-1) PIT-2 enzyme determined by peptide sequencing. The significance of each mutation was assessed by alignment of amino acid sequences and comparisons with the Staphylococcus aureus PC1 peniciflinase crystal structure. Structural similarities between SHV-1 and class A 1-lactamases are extensive, with amino acid identities of 88.9% between SHV-1 and LEN-1, 91.8% between SHV-1 and OHIO-1, and 63.7% between SHV-1 and TEM-1.Plasmid-mediated P-lactamases (EC 3.5.2.6) from Klebsiella species share interesting features at the biochemical and molecular levels. Early reports indicated that a high proportion of these enzymes were of the SHV type and unique in their responses to inhibition by the sulfhydryl group reagent p-chloromercuribenzoate (4, 26, 28). Purification and further biochemical studies indicated that SHV-type P-lactamases have a wide spectrum of hydrolytic activity towards penicillins and cephalosporins (4). SHV-1 has been associated with an uncharacterized transposon of 14.25 kilobases (kb) (29).Recent evidence indicates that extended-spectrum 3-lactamases capable of hydrolyzing new cephalosporins have been derived not only from TEM-type but also from SHVtype enzymes (13,22,31). Titration curves of SHV-1-SHV-4 and SHV-2-SHV-4 pairs suggest the replacement of an acidic amino acid in the former P-lactamases by a neutral one in the latter enzyme of each pair (36). Complete amino acid sequencing of the p453 plasmid-mediated PIT-2 (SHV-1) and an Escherichia coli SHV-2 capable of hydrolyzing cefotaxime identified a single amino acid substitution of a serine for glycine at position 234 (3). All of the extended-spectrum SHV-type P-lactamases retained the active-site serine at position 66.This work reports the nucleotide sequence of the prototype SHV-1 bla gene isolated from the Klebsiella sp. plasmid R974. We also present data on intragenic DNA probes and the genetic relatedness of SHV-1 to other SHV-type enzymes, LEN-1, OHIO-1, and other class A P-lactamases. MATERIALS AND METHODSBacterial strains and plasmids. The bacterial plasmids used are described in Table 1. E. coli HB101 (F-hsdS20 recAJ3 ara-14 proA2 leu lacYJ galK2 rpsL20 xyl-S5 mtl-l supE44) was used for cloning, and E. coli JM101 [supE thi A(lacproAB) (F' traD36 proAB lacIq Z AM15)] was utilized as the recipient for M13mpi8 and M13mpl9 recombinant bacterio-* Corresponding author. phages for nucleotide sequencing (7,38). Growth conditions and preparation of DNA for hybridization and c...

“…The principal 8i-lactamases of 112 such strains from London and 96 strains from Nottingham were identified using isoelectric focusing (16). Initially the enzymes were classified as being either chromosomally or R-plasmid mediated or of indeterminate genetic origin (14,15,18,19,27).…”

mentioning

confidence: 99%

Principal beta-lactamases responsible for resistance to beta-lactam antibiotics in urinary tract infections

Simpson¹,

Harper²,

O'Callaghan³

1980

Two independent surveys have been conducted to determine the prevalent bacterial species and beta-lactamase types present in clinical populations of gram-negative, ampicillin-resistant isolates. A total of 208 isolates (112 from Nottingham Hospital and 96 from Charing Cross Hospital), all of which had been collected from out-patients suffering from urinary tract infections, were investigated. The incidence of ampicillin-resistant isolates (minimum inhibitory concentrations, 8 micrograms/ml) was 24.1% and 18.8% within the Nottingham and Charing Cross samples, respectively. The surveys gave similar results within the ampicillin-resistant samples. Escherichia coli was the prevalent bacterial species (52.9%), followed by Klebseilla pneumoniae (30.3%). The majority of isolates, at least 54.8% and possibly as high as 74.5%, owed their principal beta-lactamase activity to enzymes mediated by R-plasmids. The most prevalent beta-lactamases were TEM-1 (53.3%), SHV-1 (30.9%), and OXA-1 (11.5%). Positive associations were found between E. coli and TEM-1 or OXA-1 and between K. pneumoniae and SHV-1.