Multidrug-resistant bacteria isolated from automated teller machine in metropolitan area of São Paulo, Brazil

The aim of this study was to investigate bacterial contamination on surfaces of randomly selected Automated Teller Machine and their sensitivity to antibiotics in São Paulo city, Brazil. The swabs collected aseptically were inoculated in selective and non-selective media in triplicate and incubated at 37 °C for 24 h. After Gram staining the isolated colonies, complementary biochemical tests were applied. The antibiotic sensitivity pattern of all isolates (15 Gram-positive bacteria and 7 Gram-negative bacteria) was determined using the Kirk Bauer method using chloramphenicol, clindamycin, norfloxacin, erythromycin, gentamicin and tetracycline diffusion discs. All ATM surfaces tested were contaminated with at least one genus of bacteria. The most frequently isolated bacteria were Staphylococcus aureus (64%), Enterococcus spp. (28%) and Acinetobacter spp. (21%), followed by coagulase-negative staphylococci (14%), Pseudomonas spp. in 12 (14%), Salmonella spp. (7%), Escherichia coli (7%). ATMs in the São Paulo metropolitan region were shown to be contaminated with bacteria that are resistant to the commonly used antibiotics. All Gram-negative and Gram-positive bacteria isolated were multidrug-resistant, however, the strains were sensitive (S) or showed an intermediate response profile (I) to tetracycline, with the exception of three strains of Pseudomonas spp., Acinetobacter spp. and Staphylococcus aureus, which were resistant to tetracycline. Norfloxacin and gentamicin showed resistance response profile to all bacteria. Based on these findings, it is recommended to perform hand washing and use of antiseptics after using ATMs.