Emergence of MDR Enterobacter hormaechei RSM5 in Pharma Effluent and its Implications in β-lactam Antibiotic Removal from Effluent.

Antibiotic resistance poses the biggest threats to global health and development and also to food security. β-lactam antibiotics (BLAs) responsible for the transpeptidation/cross-linking process during cell wall biosynthesis contribute to the maximum resistance. The production of β-lactamase enzyme is a significant contributing factor to the development of antibiotic resistance to β-lactam antibiotics. Unintentional disposal of antibiotics from the manufacturing units of pharma industries to the water bodies enhances the exposure of antibiotics, contributing to resistance. This study describes the presence of > 50 antibiotic-resistant bacterial strains in pharma effluent of Himachal Pradesh, India. Among 54 isolates, 40% showed ampicillin resistance above 100 µg/mL, 13% showed resistance above 5000 µg/mL, and 3 strains showed resistance at 15,000 µg/mL of ampicillin. Enterobacter hormaechei RSM5 showed the highest minimum inhibitory concentration (MIC) and cell viability and was selected for further studies. It produces lactamase (0.24 U/mL) to resist the higher concentration of antibiotics present in the media/effluent and demonstrated resistance against 3 different classes of antibiotics, confirming its status as a multidrug resistance (MDR) strain. The high-performance liquid chromatography (HPLC) analysis of the isolate demonstrated that Enterobacter hormaechei RSM5 can degrade ampicillin within 24 h of incubation in medium/effluent. The emergence of Enterobacter as a pathogen with antibiotic resistance poses a significant health concern that could also be explored for the removal of antibiotics from the effluent at the source. The future of research in this area needs to be open and mindful of new approaches.