Relationship between penicillin-binding protein patterns and β-lactamases in clinical isolates of Bacteroides fragilis with different susceptibility to β-lactam antibiotics

• Published in: Journal of medical microbiology Vol. 53; no. 3; pp. 213 - 221
• Main Authors: PIRIZ, Segundo, VADILLO, Santiago, QUESADA, Alberto, CRIADO, Jeronimo, CERRATO, Rosario, AYALA, Juan
• Format: Journal Article
• Language: English
• Published: Reading Society for General Microbiology 01.03.2004
• Subjects: Amino Acid Sequence; Anti-Bacterial Agents - pharmacology; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - physiology; Bacteroides fragilis; Bacteroides fragilis - chemistry; Bacteroides fragilis - drug effects; Bacteroides fragilis - enzymology; Bacteroides fragilis - genetics; Base Sequence; beta-Lactamases - chemistry; beta-Lactamases - genetics; beta-Lactamases - physiology; beta-Lactams - pharmacology; Biological and medical sciences; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - physiology; DNA Fingerprinting; DNA, Bacterial - chemistry; Drug Resistance, Bacterial; Escherichia coli; Fundamental and applied biological sciences. Psychology; Hexosyltransferases - chemistry; Hexosyltransferases - genetics; Hexosyltransferases - physiology; Humans; Infectious diseases; Medical sciences; Microbial Sensitivity Tests; Microbiology; Molecular Sequence Data; Molecular Weight; Muramoylpentapeptide Carboxypeptidase - chemistry; Muramoylpentapeptide Carboxypeptidase - genetics; Muramoylpentapeptide Carboxypeptidase - physiology; Penicillin-Binding Proteins; Peptidyl Transferases - chemistry; Peptidyl Transferases - genetics; Peptidyl Transferases - physiology; Polymerase Chain Reaction; Antibiotic; Sensitivity; Microbiology; Enzyme; Bacteroides fragilis; β-Lactams; Bacteria; Hydrolases; β-Lactamase; Clinical isolate; Bacteroidaceae; Penicillin binding protein
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/jmm.0.05409-0

This study examines the role of the penicillin-binding proteins (PBPs) of Bacteroides fragilis in the mechanism of resistance to different beta-lactam antibiotics. Six of the eight strains used were beta-lactamase-positive by the nitrocefin assay. These strains displayed reduced susceptibility to imipenem (MIC, 2-16 mg l(-1)) and some of them were resistant to the actions of ampicillin, cefuroxime, cephalexin, cefoxitin and piperacillin. When studying specific enzymic activity, the capacity to degrade cefuroxime was only detected in strains AK-4, R212 and 0423 and the capacity to degrade cephalexin was only detected in strains R212 and 2013E; no specific activity was detected on imipenem. Metallo-beta-lactamase activity was only detected in strains AK-2 and 119, despite the fact that the cfiA gene was identified in four strains (AK-2, 2013E, 119 and 7160). The cepA gene was detected in six of the eight strains studied. Three high-molecular-mass PBPs were detected in all strains; however, in some cases, PBP2Bfr and/or PBP3Bfr appeared as a faint band. PBP4Bfr and PBP5Bfr were detected in six strains. PBP6Bfr only was detected in B. fragilis strains AK-2, 0423, 119 and 7160. By analysis of the sequence of B. fragilis chromosomal DNA and comparison with genes that are known to encode PBPs in Escherichia coli, six genes that encode PBP-like proteins were detected in the former organism. The gene that encodes the PBP2 orthologue of E. coli (pbpABfr, PBP3Bfr) was sequenced in six of the eight strains and its implications for resistance were examined. Differences in the PBP3Bfr amino acid sequences of strains AK-2 and 119 and their production of beta-lactamases indicate that these differences are not involved in the mechanism of resistance to imipenem and/or cephalexin.