Identification, antimicrobial susceptibility screening and ESBL-status of Gram-negative bacteria from healthy humans and livestock waste by VITEK-2 Automated System

Bacteria in healthy body sites of humans and livestock waste may harbour antibiotic resistance and cause community-based opportunistic and resistant infections. The study profiled the antibiotic susceptibilities of resident bacteria in healthy humans and livestock waste. Gram-negative bacteria were isolated from 23 specimens including skin swabs (6), nasal swabs (4), urine (6), stool (3), chicken droppings (2) and cattle droppings (2). VITEK® 2 Automated System was used for identification, antimicrobial susceptibility and extended-spectrum β-lactamase (ESBL) production test of the isolates. Nineteen (19) Gram-negative bacteria belonging to five genera and six species were identified, including Escherichia coli (n=9) 47.4%, Klebsiella pneumoniae ssp pneumoniae (n=1) 11.1%, Enterobacter cloacae ssp dissolvens (n=1) 11.1%, Acinetobacter baumannii (n=3) 15.8%, Acinetobacter haemolyticus (n=1) 11.1%, and Providentia stuartii (n=4) 21.1%. The isolates showed highest resistances to Ampicillin (78.6%) and Piperacillin (63.2%) and high susceptibilities to Ertapenem, Amikacin, Ciprofloxacin and Levofloxacin (100%); Ceftazidime, Cefepime, Meropenem (94.7%); Cefoxitin (93.3%); Gentamicin and Tobramycin (73.7%). Multiple Antibiotic Resistance (MAR) index values above the critical limit of 0.2 were shown by 100% (4/4) of Providentia stuartii isolates, 75% (3/4) of Acinetobacter isolates and 33.3% (3/9) of E. coli isolates. All the isolates tested negative for ESBL production. The public health implication is that resident bacteria from healthy individuals harbouring antibiotic resistance may transmit these to other bacteria or cause resistant opportunistic infections difficult to treat. Resistant bacteria from livestock can be transmitted to humans through the food chain. Proper disposal or decontamination of human body secretions and livestock waste is necessary.