Comparative study of the beta-lactamase activity found in Achromobacter

Area of Science:

• Microbiology
• Enzymology
• Genetics

Background:

• Achromobacter species are Gram-negative bacteria.
• Beta-lactamase activity is a significant factor in antibiotic resistance.
• Understanding beta-lactamases in Achromobacter is crucial for clinical microbiology.

Purpose of the Study:

• To characterize beta-lactamase activity in clinical isolates of Achromobacter species.
• To identify and differentiate the types of beta-lactamases present.
• To assess the clinical relevance of these enzymes.

Main Methods:

• Survey of 21 clinical Achromobacter isolates.
• Isoelectric focusing for enzyme characterization.
• Affinity chromatography, molecular weight determination, immunological identity, and genetic analysis.
• Microacidimetric method for kinetic analysis (Km, Vmax).

Main Results:

• All tested strains showed high beta-lactamase activity.
• Three distinct beta-lactamase patterns were identified in 19 strains.
• Two cephalosporinases (MULB 901, pI 7.4; MULB 905, pI 9.3) are of chromosomal origin.
• One cephalosporinase (MULB 906, pI 8.1) is plasmid-mediated (8.2 MDal) and hydrolyzes cefoxitin, cefotaxime, and moxalactam.
• Enzymes primarily function as cephalosporinases, not hydrolyzing oxacillin, cloxacillin, or methicillin.
• Beta-lactamase synthesis was constitutive in all cases.

Conclusions:

• Beta-lactamase activity is common in Achromobacter clinical isolates.
• The identified cephalosporinases are distinct from those in other Gram-negative bacteria.
• These enzymes possess significant clinical interest due to their prevalence and unique properties.