Agribusiness effluents represent a challenge due to the chemical, physical, and microbiological characteristics of their pollutants, which can generate impacts on public health. Advanced effluent treatment systems can be employed; however, these systems are unable to eliminate resistant microorganisms. In view of this, the objective of this study was to evaluate physical, chemical, and microbiological parameters of treated effluent from a poultry and fish processing industry.

The physical-chemical parameters evaluated were pH, temperature, electrical conductivity, turbidity, hardness, chemical oxygen demand, biochemical oxygen demand, nitrite, nitrate, ammoniacal nitrogen, phenols, oils and greases, chloride, heavy metals (iron, copper, chromium, nickel, zinc, lead, and cadmium), and residue series. Coliform counting was performed using the multiple-tube technique. Bacterial isolation was carried out on Violet Red Bile Agar. Identification of isolates occurred by “Matrix-Assisted Laser Desorption Ionization – Time of Flight”, and antimicrobial susceptibility was evaluated by disk diffusion on Müeller Hinton agar.

Some physical-chemical parameters were above the limits determined by current legislation: salinity (0.06%), nitrate (19.53 mg/L), phosphorus (45.58 mg/L), iron (63 mg/L), chromium (0.39 mg/L), and copper (3.81 mg/L). The amount of total and thermotolerant coliforms was greater than 23 Most Probable Number per 100 mL. A total of 35 isolates belonging to the order Enterobacterales were obtained: 14 Klebsiella pneumoniae, 11 Escherichia coli, 2 Cronobacter sp, 2 Enterobacter cloacae, 2 Enterobacter kobei, 2 Enterobacter roggenkampii, and 2 Providencia stuartii. The isolates showed resistance to amoxicillin + clavulanic acid (52.9%), gentamicin (38.2%), cefoxitin (38.2%), amikacin (35.3%), ceftazidime (32.4%), ertapenem (23.5%), sulfamethoxazole + trimethoprim (23.5%), ciprofloxacin (20.6%), ceftriaxone (20.6%), cefotaxime (17.6%), cefepime (17.6%), nalidixic acid (14.7%), aztreonam (11.8%), imipenem (5.9%), and meropenem (2.9%). Resistance to carbapenems predominated among K. pneumoniae isolates.

Non-compliance of some analyzed parameters indicates failures in the effluent treatment process. Antimicrobial resistance in environmental bacterial isolates represents an emerging concern in the global health scenario.