Cluster Analysis of Antibiotic Resistant Escherichia coli Isolates from Piglet Faecal Samples of Selected Organised Farms in India

The objective of the study was to assess the cluster analysis technique for phenotypic resistance to imipenem, meropenem, ertapenem, moxalactam and aztreonam in Escherichia coli isolates from piglet faecal samples of selected organised farms in India. A cross-sectional study was conducted at 10 different farms of seven states of India to ascertain the epidemiology of antibacterial resistance in piglets below 3 months of age. From 673 piglet faecal samples, 112 E. coli were isolated on MacConkey agar added with imipenem (1 mg/L). Of the 112 E. coli screened for imipenem, meropenem, ertapenem, moxalactam and aztreonam resistance, 23 isolates were carbapenem resistant. Different cluster analysis techniques were used to identify similar clusters. The hierarchical cluster analysis showed the resistant isolates in two major clusters. The cluster A (Hassan and Mannuthy) comprised of 9 isolates and cluster B (Bareilly, Sitapur, Guwahati and Barapani) comprised of 14 isolates. In two-stage cluster analysis, the season (F = 47.563**, P = 0.00) and location (F = 171.741**, P = 0.00) showed statistical significance in forming clusters. The hierarchical cluster analysis showed more homogenous cluster. Thus, cluster analysis appeared as a better statistical technique for discriminating the isolates based on epidemiological factors and phenotypic antibiotic resistance pattern.