A study on emerging resistance to carbapenem antibiotics in gram-negative bacteria isolated from clinical samples

Objectives Gram-negative bacteria are a major cause of public health concern due to their resistance to different antibiotics. Numerous reports on carbapenem resistance were published by different authors in different places in India, but there are very few studies on the prevalence of carbapenem resistance in northeast India. Material and Methods Pathogens isolated from urine, pus, respiratory, etc., samples were identified & tested with the antibiotic sensitivity test. The modified Hodge's test was performed to detect carbapenemase production. The carbapenemase producers were tested with the synergy test using a checkerboard assay with two antibiotics, meropenem and colistin. Results Bacterial isolates (144) from urine, pus, respiratory samples, etc., were collected from the Downtown Hospital, Guwahati, Assam. Klebsiella spp. (54.86%) and Escherichia coli (36.81%) were the most common isolates, followed by Pseudomonas spp. (3.47%), Enterobacter spp. (2.78%), Proteus spp.(0.69%), Citrobacter spp. (0.69%), and Morganella spp. (0.69%). We observed resistance against meropenem (27.8%), ertapenem (25.7%), fosfomycin (16.7%), ceftazidime (45.8%), ceftriaxone (53.5%), cefoxitin (54.9%), ampicillin (61.8%), colistin (52.1%), gentamycin (26.4%), tetracycline (27.8%), chloramphenicol (18.8%), and ciprofloxacin (38.9%). Conclusion The study reported high resistance against third-generation cephalosporins, such as ceftriaxone and ceftazidime, including penicillin and colistin. We found carbapenam resistance very common among the isolates, however combination drugs showed lower levels of minimum inhibitory concentration (MIC). More studies with bigger sample sizes need to be conducted in future.