Multiple Antimicrobial Resistance and Heavy Metal Tolerance of Biofilm-Producing Bacteria Isolated from Dairy and Non-Dairy Food Products

Abstract

Foodborne pathogens have acquired the ability to produce biofilms to survive in hostile environments. This study evaluated biofilm formation, antimicrobial resistance (AMR), and heavy metal tolerance of bacteria isolated from dairy and non-dairy food products. We aseptically collected and processed 200 dairy and non-dairy food specimens in peptone broth, incubated them overnight at 37 °C, and sub-cultured them on various culture media. Bacterial growth was identified with biochemical tests and API 20E and 20NE strips. The AMR of the isolates was observed against different antibacterial drug classes. Biofilm formation was detected with the crystal violet tube method. Heavy metal salts were used at concentrations of 250–1500 µg/100 mL to observe heavy metal tolerance. We isolated 180 (50.4%) bacteria from dairy and 177 (49.6%) from non-dairy food samples. The average colony-forming unit (CFU) count for dairy and non-dairy samples was 2.9 ± 0.9 log CFU/mL and 5.1 ± 0.3 log CFU/mL, respectively. Corynebacterium kutscheri (n = 74), lactobacilli (n = 73), and Staphylococcus aureus (n = 56) were the predominant Gram-positive and Shigella (n = 10) the predominant Gram-negative bacteria isolated. The correlation between biofilm formation and AMR was significant (p < 0.05) for most cephalosporins, aminoglycosides, and fluoroquinolones. Heavy metal tolerance tended to be higher in biofilm producers at different metal concentrations. The pathogens isolated from dairy and non-dairy food showed a high burden of AMR, high propensity for biofilm formation, and heavy metal tolerance, and pose an imminent threat to public health.

Physiological Characteristics of Putative Enterobacteria Associated with Meat and Fish Available in Southern Brazilian Retail Markets: Antimicrobial Susceptibility, Toxic Metal Tolerance and Expression of Efflux Pumps

“…The occurrence of metal tolerant foodborne pathogens has been reported by multiple studies. It is accepted that an antimicrobial co-resistance and cross-resistance phenomena (resistance borne by adjacent genetic markers in mobile genome such as integrons and the multiple-resistance physiological mechanisms related to one genetic marker, respectively) may be screened by a toxic metal tolerance [ 36 , 37 , 38 ]. Nonetheless, the lack of technical standards for such experimental designs hinders a data comparison.…”

The Impact of Metal and Heavy Metal Concentrations on Vancomycin Resistance in Staphylococcus aureus within Milk Produced by Cattle Farms and the Health Risk Assessment in Kurdistan Province, Iran

“…The correlation between biofilm formation and AMR has been observed for most cephalosporins, aminoglycosides, and fluoroquinolones, with biofilm-producing bacteria exhibiting greater tolerance to various metal concentrations. The results of the study suggest that pathogenic genes isolated from dairy and non-dairy foods exhibit high levels of AMR, a clear inclination for biofilm formation, and tolerance to heavy metals, posing an imminent threat to public health [ 13 , 14 ]. In this context, the transfer of pollutants through the food chain is more significant than through water [ 15 ].…”

Phytochemicals: potential alternative strategy to fight Salmonella enterica serovar Typhimurium

“…Foodborne diseases are brought on by consuming food, herbs, and beverages that have been contaminated by microorganisms as well as hazardous compounds including heavy metals ( 1 ), mycotoxins and bacterial toxins, as well as fermentation byproducts including biogenic amines and ethyl carbamate ( 2 ). Most of these foodborne illnesses are a problem for worldwide public health because they are brought on by pathogenic bacteria, viruses and parasites ( 3 , 4 ).…”