ABSTRACT

Background: There is lack of systematic studies simultaneously comparing antibiotics resistance, and related genes (ARGs) from

gut of animals and humans, and subsequently comparison with clinical isolates.

Methods: 137 Gram-negative bacteria from gut of poultry, cattle, and healthy human volunteers and a subset of 74 GNB were

studied for frequency/patterns for antibiotics resistance, and prevalent ARGs (blaCTX-M, blaTEM, blaSHV, blaampC and blaNDM-1) by PCR.

Comparative analyses for resistance rates and patterns, and existing genes were done. Representative PCR amplicons were

sequenced and analysed for precise bla type and RAPD typing of the human faecal and clinical isolates was done to see any

clonal relatedness/diversity.

Results: Varying frequency of resistance was noticed in gut isolates from poultry, cattle and healthy human volunteers and the

patterns were different. Resistance rates were much higher in clinical isolates than the gut flora, including from healthy human

volunteers. No resistance was seen with colistin in neither clinical nor gut isolates from poultry, cattle, and healthy human

volunteers. Resistance to minocycline and tigecycline was noticed in 28.78% and 30.30% clinal isolates, respectively. From 139

faecal isolates, a total of 7 CTX-M (5.03%; 7/139), 10 TEM (7.19%; 10/139), and 4 SHV (2.87%; 4/139) were detected. CTX-M was

more prevalent in the human gut isolates (13.89%; 5/36) as compared to poultry (1.69%; 1/59) and cattle (2.27%; 1/44), whereas

TEM was found to be more prevalent in poultry isolates (13.56%; 8/59). On the other hand, AmpC was present in significant

proportion (58.27%; 81/139) of the gut isolates from all the three test groups and was almost equally distributed with the highest

occurrence in cattle. Among clinical isolates, maximum occurrence of bla genes was of blaCTX-M (58%), followed by blaampC

(40%), blaSHV (26%), and blaTEM (12%). Sequencing of representative isolates showed presence of CTX-M-15, TEM-1 and

SHV-38. There was no clonal relatedness between human faecal isolates and clinical isolates.

Conclusions: Multi-drug-resistance of varying frequency was noticed in faecal isolates and patterns were different between faecal

and clinical isolates. There appears to be frequent and wider dissemination of class C beta-lactamase (AmpC) at animal and

human interface, however wider dissemination of class A ESBL (CTX-M, TEM, SHV) has not yet established. Though no

resistance to colistin in animal- and human-faecal and clinical isolates is a sign of relief, appearance of resistance to reserved drug

such as tigecycline is alarming.

Keywords: gut resistome; antibiotics resistance genes; poultry; cattle, healthy human volunteer; clinical bacterial isolates;

comparative study; India