Co-Resistance to Antibiotics and Heavy Metals in ESBL-Producing Gram-Negative Bacteria from Clinical Samples

Abstract

There is growing concern about the combined impact of antimicrobial resistance in pathogenic bacteria and environmental contaminants, such as heavy metals, on the efficacy of routine antibiotics. The specific aim of this study is to evaluate the co-resistance of Extended Spectrum Beta-Lactamase (ESBL)-producing isolates to common heavy metal pollutants (Copper, Arsenic, and Lead) individually and in combination with antibiotics. The present study evaluated the effects of three heavy metals (arsenic, copper, and lead) on the antimicrobial susceptibility profiles of 5 ESBL-producing bacteria. A total of 200 clinical specimens were collected, from which 150 Gram-negative bacterial isolates were obtained and studied. This included Escherichia coli 60 (40%), Pseudomonas aeruginosa 35 (23%), Enterobacter aerogenes 27 (18%), Proteus mirabilis 15 (10%), and Klebsiella pneumoniae 13 (8.60%). The Antibiotics, Double Disc Synergy Test (DDST) test revealed that 30 samples were ESBL-producing bacteria: 15 E. coli, 5 Enterobacter aerogenes, 3 Proteus mirabilis, 5 Pseudomonas aeruginosa, and 2 Klebsiella pneumoniae. These samples were tested for heavy metal resistance; ESBL-producing bacteria grew densely in the presence of different concentrations of arsenic, copper, and lead and Growth was observed up to and including 0.5 mg/mL, but was inhibited at 0.75 mg/ml. When Antibiotic Susceptibility Test (AST) was performed in the presence of heavy metals, the susceptibility profile shifted from susceptible to resistant for Meropenem. For the remaining antibiotics tested in combination with heavy metals, and antibiotics did not change the susceptibility profile, but heavy metals did affect the zone size. Heavy metal presence either reduced or increased the zone size, depending on the type of metal and antibiotic.