Characterization of a Chromosomal Gene Encoding Type B β-Lactamase in Phage Group II Isolates of Staphylococcus aureus

Abstract

In contrast to most Staphylococcus aureus isolates in which the gene for staphylococcal β-lactamase (blaZ) is plasmid borne, isolates typeable by group II bacteriophages frequently carry blaZ on the chromosome. Furthermore, the chromosomal gene encodes the type B variant of staphylococcal β-lactamase for which the nucleotide and deduced amino acid sequences have not yet been reported. To better understand β-lactamase production among phage group II staphylococci and the nature of the type B β-lactamase, we determined the type and amount of enzyme produced by 24 phage group II isolates. Of these isolates, 1 did not produce β-lactamase, 8 produced the type B enzyme, and 15 produced the type C enzyme. In all eight type B β-lactamase-producing isolates, blaZ was located on the chromosome. This was in contrast to the type C β-lactamase-producing isolates, in which blaZ was located on a 21-kb plasmid. The nucleotide sequence corresponding to the leader peptide and the N-terminal 85% of the mature exoenzyme form of type BS. aureus was determined. The deduced amino acid sequence revealed 3 residues in the leader peptide and 12 residues in the exoenzyme portion of the β-lactamase that differ from the prototypic type A β-lactamase sequence. These include the serine-to-asparagine change at residue 216 found in the kinetically similar type C enzyme, a threonine-to-lysine change at residue 128 close to the SDN loop (residues 130 to 132), and several substitutions not found in any of the other staphylococcal β-lactamases. In summary, modern isolates ofS. aureus typeable by group II phages produce type B or type C staphylococcal β-lactamase. The type B gene resides on the chromosome and has a sequence that, when compared to the sequences of the other staphylococcal β-lactamases, corresponds well with its kinetic properties.

Relapse of Type A -Lactamase-Producing Staphylococcus aureus Native Valve Endocarditis during Cefazolin Therapy: Revisiting the Issue

“…A modest decrease (to 44 mg/mL) was also observed at 48 h in the control flask (cefazolin without bacterial cells). DNA sequencing of the amplified product from the TX0117 strain showed an identical nucleotide sequence to that previously reported for the type A b-lactamase gene [4,16].…”

“…A higher concentration of the drug is then needed to overcome this effect. The phenotypic characteristics of this strain were confirmed by DNA sequencing of the b-lactamase gene, the findings of which were identical to previously described staphylococcal type A b-lactamase [4,16].…”

“…DNA sequencing of the b-lactamase gene showed that it was identical to that of the S. aureus type A b-lactamase, known to efficiently inactivate cefazolin. A word of caution is given regarding the use of this antibiotic for treatment of endocarditis caused by this type of S. aureus isolate.Four different variants of Staphylococcus aureus b-lactamases (A, B, C, and D) have been identified, initially by immunologic methods [1], later by their rate of hydrolysis of different b-lactam substrates using extract and whole-cell suspension extraction [2,3], and more recently by DNA sequencing of the b-lactamase gene [4]. The difference in hydrolysis rates of the 4 types of b-lactamases for various b-lactams was well documented in the past, showing, for instance, that the rate of hydrolysis of cefazolin by the type A b-lactamase was 5-and 20-fold greater than those for cefamandole and cephalothin, respectively [5].…”

The Cefazolin Inoculum Effect Is Associated With Increased Mortality in Methicillin-Susceptible Staphylococcus aureus Bacteremia

“…Identification of the BlaZ protein sequence was done with BlastX using the reference sequence WP_000733289.1 from the NCBI. Typing of BlaZ was carried out by identification of the amino acid residues in positions 128 and 216 [22]. Phylogenetic reconstruction of all sequenced genomes using the core genome was performed with RAxML, based on RAST annotations [39, 40].…”

“…Initially, typing of such enzymes (BlaZ) was based on immunological methods with 4 different serotypes (A, B, C, and D) described [19]. Subsequently, typing was performed based on limited sequences of BlaZ and some support by kinetic studies that involved hydrolysis of different β-lactams [21, 22]. From those studies, type A BlaZ seemed to be more efficient in hydrolyzing cefazolin, and the preferred substrate for type C BlaZ was cephalothin.…”