AVALIAÇÃO DE DISTÂNCIAS NA DETECÇÃO FENOTÍPICA DE BETALACTAMASE DE ESPECTRO ESTENDIDO EM CEPA PADRÃO DE Klebsiella pneumoniae

Among bacteria with high resistance to antimicrobials, the Gram-negative types, producers of extended-spectrum beta-lactamases (ESBL), have become an extensive problem for public health. ESBL-producing strains are often associated with various infections, such as pneumonia, septicemia, urinary infections, bacteremia, and meningitis. Klebsiella pneumoniae is a Gram-negative bacillus found in the normal microbiota of the human intestine. This microorganism has high rates of ESBL-producing strains that catalyze the hydrolysis of the beta-lactam ring of antimicrobials that have it. The TSDD methodology uses the synergism of the antibiotics diffused in the Muller Hinton agar (MHA) so that the appearance of the phantom area occurs. However, this synergism may present false results in case the distance between the discs containing the drugs is greater than the capacity of antimicrobial diffusion in MHA. ESBL detection is a low-cost technique that has been frequently used in microbiology laboratories because it is easy to perform and provides reliable results, though a consensus as to the standard distances between disks is nonexistent. The objective of this research is to measure how far, considering center to center, this laboratory routine can be used in the double-disc synergism test (TSDD) for phenotypic detection of ESBL. A strain of ESBL-producing K. pneumoniae ATCC ™ 700603 was used to perform this work as recommended by BrCAST. Our results indicate that the variations in distances can bring false-negative results to values ​​greater than 34 mm and smaller than 20 mm.