197

1 Bihar Veterinary College, Bihar Animal Sciences University, Patna, Bihar 800014, India. 
2 Regional Centre for Eastern Region-Indian Council of Agricultural Research, Patna, Bihar 800014, India.

* Corresponding author at: Department of Veterinary Public Health & Epidemiology, Bihar Veterinary College, Bihar Animal Sciences University, 
Patna, Bihar 800014, India. 

Tel.: 91 9431260790, e-mail: drkaushikvet@gmail.com.

Parole chiave
Pollame,
E. coli,
resistenza antimicrobica,
caratterizzazione 
molecolare,
stx

1
 gene,

stx
2
 gene.

Riassunto
In questo studio, condotto su 228 campioni di carne e 24 di uova, sono stati rilevati dalla 
carne 62 isolati di Escherichia coli appartenenti a differenti sierogruppi basati sul sierotipo 
O, ovvero O29 (10.8%), O8 (7.7%), O40 (6.15%), O2 (4.61%), O60 (3.08%), O106 (3.08%), O42 
(1.54%), O87 (1.54%); per ciascun sierotipo O1, O7, O30, O45, O59, O66, O105, O1116, O136, 
O141, O147, O148, O166, O172, ne è stato individuato uno; 16 (24,62%) sono risultati non 
dimostrabili e 6 (9,23%) erano di tipi approssimativi. La caratterizzazione molecolare è stata 
eseguita mirando ai frammenti dei geni di virulenza stx

1
 e stx

2
; 10 (16,12%) trasportavano 

il gene stx
2
 mentre nessuno lo stx

1
. Gli isolati di E. coli hanno mostrato un'ampia variazione 

nel pattern di resistenza contro gli agenti antimicrobici usati (9-90%). La massima resistenza 
è stata osservata contro cefuroxima (89,1%) e penicillina (89,4%), seguita da ampicillina 
(80,43%), vancomicina (74,1%), cotrimossazolo (73,1%), cefalotina (60,8%) , ceftriaxone 
(28,2%), tetraciclina (17,4%), gentamicina (13,0%), amikacina (13,04%), ofloxacina (13%) 
e ciprofloxacina (6,5%). È stato invece notato un alto grado di suscettibilità nei confronti 
di amikacina (84,7%) e ciprofloxacina (76%), seguita da gentamicina (71,73) e ofloxacina 
(60,86%). Sono state riscontrate elevate resistenze antibiotiche multiple e identificato un 
totale di 34 pattern di resistenza.

Resistenza antimicrobica e caratterizzazione molecolare di Escherichia coli 
nel pollame in India orientale

Keywords
Poultry,
E. coli,
Anti-microbial 
resistance,
Molecular 
characterisation,
stx

1
,

stx
2
.

Summary
In this study 252 poultry samples comprised of poultry meat (n  =  228) and poultry eggs 
(n = 24) were screened for the isolation of Escherichia coli (E. coli). A total of 62 E. coli isolates 
were recovered from poultry meat. The E. coli isolates belonged to different serogroups 
based on ‘O’ serotyping of the isolates viz O29 (10.8%), O8 (7.7%), O40 (6.15%), O2 (4.61%), 
O60 (3.08%), O106 (3.08%), 42 (1.54%), O 87 (1.54%), and 01 serotypes of O1, O7, O30, O45, 
O59, O66, O105, O1116, O136, O141, O147, O148, O166, and O172. Sixteen (24.62%) of the 
isolates were UT (untypable) and 6 (9.23 %) were rough types. Molecular characterisation of 
the isolates was performed, targeting stx

1
 and stx

2
 virulence gene fragment. Out of 62 E. coli 

isolates, 10 (16.12%) were carrying virulence gene stx
2
, whereas none of the isolate was 

carrying stx
1
 gene. The E.  coli isolates showed wide variation in resistance pattern against 

the antimicrobial agents that we used (9-90%). Among E. coli isolates, maximum resistance 
was observed against cefuroxime (89.1%) and penicillin (89.4%), followed by ampicillin 
(80.43%), vancomycin (74.1%), co-trimoxazole (73.1%), cephalothin (60.8%), ceftriaxone 
(28.2%), tetracycline (17.4%), gentamicin (13%), amikacin (13.04%), ofloxacin (13%), and 
ciprofloxacin (6.5%). A high degree of susceptibility was observed against amikacin (84.7%) 
and ciprofloxacin (76%) followed by gentamicin (71.73) and ofloxacin (60.86%). High multiple 
antibiotic resistances were observed and a total of 34 resistance patterns were identified. 

Purushottam Kaushik1*, Anjay1, Savita Kumari1, Shanker Dayal2 and Sunil Kumar1

Antimicrobial resistance and molecular 
characterisation of E. coli from poultry

in Eastern India

Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2 
Accepted: 09.05.2014  |  Available on line: 30.09.2018



198 Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2

and molecular characterisation of stx
1
 and stx

2
 genes 

in E. coli isolated from poultry meat.

Materials and methods

Sample Collection
A total of 252 samples constituting of fresh poultry 
meat (n  =  228) and eggs (n  =  24) were collected 
randomly from different shops and market of Patna, 
India during September 2010 to March 2013. The 
samples were transported under cold conditions 
to the laboratory in the Department of Veterinary 
Public Health, Bihar Veterinary College, Patna, India, 
and processed within 1 hour of collection. 

Isolation and biochemical 
characterization
Ten grams of meat sample and egg white were 
inoculated in MacConkey broth (HiMedia, Mumbai, 
India) and incubated at 37 °C for 12 hours. Samples 
showing acid and gas production were further 
inoculated on MacConkey agar plates (HiMedia, 
Mumbai, India) and incubated at 37  °C for 
18-24  hours. Pure and characteristic pink coloured 
single colonies selected from MacConkey agar 
were subcultured on Eosin Methylene Blue (EMB) 
agar (HiMedia, Mumbai, India) in order to observe 
the metallic sheen that is characteristic of E.  coli. 
The pure colonies were picked up on Nutrient Agar 
slants and subjected to standard morphological and 
biochemical tests (Edwards and Ewing 1972).

Serotyping E. coli
All the biochemically confirmed isolates of E. coli were 
submitted to the National Salmonella and Escherichia 
Centre, Central Research Institute, Kasauli, India for 
serotyping based on somatic (O) antigens. 

Extracting E. coli DNA for the detection 
of virulence genes
The bacterial DNA was prepared as per Dutta 
and colleagues (Dutta et  al. 2011), with slight 
modification. The isolates were inoculated into 5 ml 
Luria Bertani (L-B) broth and incubated at 37  °C for 
18 hours. After incubation, 1 ml of the broth culture 
was centrifuged in a 1.5 ml microcentrifuge tube at 
8,000  rpm for 10 minutes. The pellet was washed 
twice in sterile normal saline solution (NSS) (0.85% 
NaCl) then re-suspended in 400  μl of nuclease-free 
sterile distilled water and boiled for 10  minutes 
followed by immediate chilling. Cell debris was 
removed by centrifugation at 5,000  rpm for 

Introduction
Escherichia coli (E.  coli) is a commensal bacterium 
in humans and animals; however some strains are 
capable of causing intestinal diseases. This organism 
is commonly present in the environment and is 
considered an indicator of faecal contamination of 
food and water. On the basis of virulence factors, 
E.  coli has been classified into different pathotypes: 
enterotoxigenic E.  coli (ETEC), enteroinvasive 
E.  coli (EIEC), enteropathogenic E.  coli (EPEC), 
diffusely adherent E.  coli (DAEC), enteroaggregative 
E.  coli (EAEC), and enterohemorrhagic or shiga 
toxin-producing E.  coli (EHEC/STEC). The latter 
is most commonly associated with outbreaks of 
foodborne diseases (Bandyopadhyay et  al. 2011). 
The pathogenicity of EHEC/STEC is mediated mainly 
through Shiga toxins 1 and 2 encoded by stx

1
 and stx

2
 

genes, respectively. Although bovines are considered 
to be the major carrier for EHEC/STEC, poultry may 
also harbour the organism and play an important 
role in transmission (Ferens and Hovde 2011). The 
stx

2
 gene is associated with an increased risk of 

developing hemolytic-uremic syndrome (Boerlin 
et  al. 1999). Although reports on the isolation, 
identification, and characterisation of EHEC/STEC in 
humans and animals are available in India, very few 
reports on the association of EHEC/STEC in poultry 
are available in the country (Chattopadhayay et  al. 
2001, Khan  et al. 2002, Wani et al. 2004).

During the past decade, drug resistance to 
Enterobacteriaceae has increased worldwide. Since 
E.  coli is present as gut commensal in humans and 
animals, it has become one of the microorganisms 
that are commonly resistant to antimicrobials due to 
the selective pressure imposed by the antimicrobial 
drugs used in the treatment of food animals and 
humans (Zhao et  al. 2012). Moreover, in animals 
antimicrobial agents are not only used for therapy 
and the prevention of bacterial infection, but also 
for the promotion of growth (Van den Bogaard and 
Stobberingh 2000). In the poultry sector, maximum 
numbers of antimicrobial agents are continuously 
fed to animals in order to promote growth, which 
further imposes selective pressure on the organism 
leading to development of antimicrobial resistance. 
The emergence of antimicrobial resistance among 
E.  coli of animal origin has important public health 
implications. Various authors report that animals 
are the source of drug-resistant E.  coli in humans 
(Johnson and Nolan 2009, Hammerum and 
Heuer 2009, Overdevest et  al. 2011). Szmolka and 
colleagues (Szmolka et  al. 2012) report common 
multi-resistance patterns of E. coli from food animals 
and clinical cases, which suggests that the circulation 
of multi-drug resistant E. coli circulating in the food 
chain is significant. The purpose of this study is to 
determine the prevalence, antimicrobial resistance, 

E. coli in Eastern Indian poultry  Kaushik et al.



199Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2

Kaushik et al.  E. coli in Eastern Indian poultry 

was produced by different isolates. We referenced 
the manufacturer (Hi Media) for the breakpoint 
diameter of the zone of inhibition for different 
antibiotics. Multiple-antibiotic resistance was 
defined as resistance to 2 or more antibiotic classes 
(Shekhar and Singh 2014).

Results 

Bacterial isolation and identification
A total of 62 E.  coli out of 228 meat samples was 
isolated, whereas all egg samples were found 
negative for E.  coli. The E.  coli isolates belonged to 
24 different serogroups: O29 (10.8%), O8 (7.7%), O40 
(6.15%), O2 (4.61%), O60 (3.08%), O106 (3.08%), O42 
(1.54%), O87 (1.54%), and 1 serotypes each of O1, O7, 
O30, O45, O59, O66, O105, O116, O136, O141, O147, 
O148, O166, and O172. Other results indicated 16 
(24.62%) isolates as UT (untypable), and 6 (9.23 %) 
as rough types. 

The molecular characterisation of E. coli 
by multiplex PCR
Multiplex PCR targeting stx

1
 and stx

2
 gene fragment 

of E.  coli resulted in the amplification of 349  bp 
amplicon for stx

1
 and 110 bp amplicon for stx

2
, as 

we expected (Figure 1). Out of 62 E.  coli isolates, 
13 (21%) isolates that carried only the stx

2
 gene were 

screened. These belonged to the serogroups O29, 
O8, O42, and O1.

Antimicrobial resistance 
The E.  coli isolates showed a wide variation in 
resistance patterns (9-90%) against the antimicrobial 

5 minutes. The supernatant was used as a template 
DNA for polymerase chain reaction (PCR).

Detecting virulence genes by 
multiplex PCR
A multiplex PCR protocol was standardized using 
2 sets of oligonucleotide primers targeting stx

1
 and 

stx
2
 genes (Table I). Amplification was carried out in 

a total volume of 25  µl containing 10  pmol each of 
primer, 50 µM each of dNTP, 1.5 mM MgCl

2
, 1U Taq 

DNA polymerase, 1X PCR of buffer, and 5 µl template 
DNA. A negative control containing the same 
reaction mixture except the DNA template was 
included in every experiment. The reaction condition 
was optimised with initial denaturation at 94  °C for 
5 minutes, followed by 35 cycles of denaturation at 
94 °C for 1 minute, annealing at 55 °C for 1 minute, 
and extension at 72  °C for 1 minute. Finally, an 
additional extension was achieved for 5  minutes at 
72 °C. Amplified products were separated by agarose 
gel (2% agarose in 1X Tris-borate-EDTA buffer) 
electrophoresis at 5v/cm for 2 hours and stained 
with ethidium bromide (0.5 μg/ml) (Sambrook 
et  al. 1989). A standard molecular-size marker 
(100 bp DNA ladder) was included in each gel. We 
observed and photographed DNA fragments in a 
gel documentation system (Biorad, USA). 

Antimicrobial resistance
The antimicrobial susceptibility test of isolates 
was determined using the agar disc diffusion 
method (Wayne 2002). The antibiotic discs included 
ampicillin (10  µg), amikacin (30  µg), cefuroxime 
(30  µg), ceftriaxone (30  µg), cephalothin (30  µg), 
ciprofloxacin (5  µg), co-trimoxazole (25  µg), 
gentamicin (10  µg), ofloxacin (5  µg), penicillin-G 
(10  units), tetracycline (30  µg), and vancomycin 
(30  µg). The isolates were grown on autoclaved 
Mueller Hinton broth (HiMedia, India) for 18 hours 
at 37  °C. About 100 µl of the inoculum was spread 
on Mueller Hinton agar using a sterile disposable 
L-shaped spreader. Antibiotic discs were placed 
onto the plate using sterile forceps. The plates were 
incubated at 37  °C for 24 hours and observed for 
zone of inhibition. The results were interpreted as 
susceptible, resistant, or moderately susceptible 
based on the diameter of the zone of inhibition that 

Table I. Oligonucleotide primers used in multiplex PCR reaction.

Primer Sequence Product size
stx

1
 F 5'-CAA CAC TGG ATG ATC TCA G-3'

349 bp
stx

1
 R 5'-CCC CCT CAA CTG CTA ATA-3'

stx
2
 F 5'-ATC AGT CGT CAC TCA CTG GT-3'

110 bp
stx

2
 R 5'-CTG CTG TCA CAG TGA CAA A-3'

Figure 1. Agarose gel electrophoresis showing amplified PCR product 
of stx

1
 and stx

2
 gene. Lane M = 100 bp DNA marker, Lane1 = Positive 

control for stx
1
 (349 bp amplicon) and stx

2
 (110 bp amplicon) gene, 

Lane 2-11 = E. coli isolates from meat samples, Lane12 = Negative 
control.



200 Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2

E. coli in Eastern Indian poultry  Kaushik et al.

(13%), and ciprofloxacin (6.5%). A high degree of 
susceptibility was observed against amikacin (84.7%) 
and ciprofloxacin (76%) followed by gentamicin 
(71.73%) and ofloxacin (60.86%) (Tables  II  and  III). 
The number of multiple antibiotic resistances 
pattern of isolates we observed was high and a total 
of 34 resistance patterns were identified (Table IV).

agents that have been used. The maximum 
resistances among E.  coli isolates were observed 
against cefuroxime (89.1%) and penicillin (89.4%), 
followed by ampicillin (80.43%), vancomycin 
(74.1%), co-trimoxazole (73.1%), cephalothin 
(60.8%), ceftriaxone (28.2%), tetracycline (17.4%), 
gentamicin (13%), amikacin (13.04%), ofloxacin 

Table II. Antimicrobial susceptibility of E. coli isolates.

E. coli serotypes Cu G A Ci Ak Ch Cf Co P Va Of T
UT R R R R R R R S R R R S
UT R R R R R R I S R I S I
UT R I R I S R S S R I S S

O106 I I R I I R S R R R S I
O59 I I R R S R S S R I S S
UT R R R I I I R S R I S S

O106 R S R I S R S R R R S R
UT R S R S S R S R R I S R

Rough I R R R R R S R R I S R
Rough R R R R S R S R R R R I

UT R S R I R R S R R R S S
O136 R S R S S R S R R S S S
O45 R R R R R R S R R I S S

Rough R R R S S S S R R R I I
UT R R R R S S S R R R R I

O40 S S R S S I S R R R I I
O40 R S R S S R I S R R R I
O40 R S R S S R I R R R I I
UT S S R S S S S R R R S I

Rough R S R S S R I R R R R I
UT R I R S S R S S R R R I

O147 R S R S S R S R R I I S
UT R S R S S R S R R R I S
UT R R R S I R S S I R S I
UT R I R S S R S R I R S S

O141 R S R I S S S R R S S S
O7 R S R I S R S R R I S S

O40 R S R S S S S R R R I I
O87 R S R I R R S R R R S R
O29 R S R I S R I R I R S I
O8 R S S R R R R S R R S S

O29 R I S R S R I R R R R I
O8 R S R S S S R R R R S I

O60 R S R S S I I R R R R S
O172 R I R S S I S R R R S I
O42 R I R I R R S R R I S S
O2 R S S I S S R I R R R I

Rough R S R S S R S S R S S S
O148 R S R R S I S R R R I I
042 R S R R S I S R R R I R

Rough R S R S S R S R R R S S
O1 R S R I S I S S R R I I

Cu = Cefuroxime;    G = Gentamicin;    A = Ampicillin;    Ci = Ceftriaxone;    Ak = Amikacin;    Ch = Cephalothin;    Cf = Ciprofloxacin;    Co = Co-trimoxazole; P = PenicillinG;    
Va = Vancomycin; Of = Ofloxacin;    T, Tetracycline;    S = Susceptible;    I = Intermediate;    R = Resistant;    UT = Untypeable.



201Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2

Kaushik et al.  E. coli in Eastern Indian poultry 

(Guth et al. 1989, Blanco et al. 2004, Fratamico et al. 
2010, Bandyopadhyay et  al. 2011). In the present 
study however 24 serogroups were detected. They 
were widely distributed in the eastern part of India. 
On the contrary to this finding many studies from 
India reported the isolation of a few numbers of 
serogroups from poultry (Malik et  al. 2002, Wani 
et al. 2004, Dutta et al. 2011). The E. coli of serogroups 
O2, O87, and O172 reported in this study, are 
associated with Shiga toxin producing E. coli (STEC), 
as documented by Fratamico and other authors 
(Fratamico et al. 2010, Meng et al. 2014), whereas the 

Discussion
Foodborne diseases are caused by a number of 
pathogens. Of these, E. coli is considered one of the 
most important. It is responsible for intestinal and 
extraintestinal diseases in humans (Vincent et  al. 
2010, Scallan et  al. 2011). Food plays an important 
role in the dissemination of E.  coli, causing 
community-acquired urinary tract infections 
(Vincent et  al. 2010, Ferens and Hovde 2011, Jana 
and Mondal 2013). In the present study, poultry meat 
samples collected from different retail shops were 
contaminated with different serogroups of E.  coli. 
Out of 228 poultry meat samples, 62 (27.19%) were 
positive for E. coli. This finding is both consistent with 
previous reports from different parts of India (Farooq 
et al. 2009, Bonyadian et al. 2011, Sahoo et al. 2012, 
Jana and Mondal 2013) but higher than the finding 
of Zende and colleagues (Zende et  al. 2013), who 
reported the isolation of E. coli in 16% poultry meat 
from a small sample size of meat from Mumbai, 
India. Our results indicate the contamination of 
poultry meat with E.  coli. This may be due to a lack 
of proper sanitation during slaughtering in the local 
markets or because of contaminated water is used 
to wash carcasses.

In the present study, E.  coli isolates belonged to 
24 different serogroups, namely O29, O8, O40, 
O2, O60, O106, O42, O87, O1, O7, O30, O45, O59, 
O66, O105, O116, O136, O141, O147, O148, O166, 
O172; UT (untypable) and R (rough types) were 
also recovered. Most of the serogroups identified 
have also been reported in other similar studies 

Table III. Oligonucleotide primers used in multiplex PCR reaction.

Antibiotic 
Number of 

resistant strain 
(n = 46)

Percent

β lactums 
antibiotic

Ampicillin 37 80.4

Penicillin 41 89.13

Cephalosporins

Cephalothin
(First generation)

28 60.86

Cefuroxime
(Second generation)

41 89.13

Ceftriaxone
(Third generation)

13 28.26

Fluroquinolones
Ciprofloxacin 3 6.52

Ofloxacin 6 13.04

Aminoglysides
Amikacin 6 13.04

Gentamicin 6 13.14

Sulfonamides Co-trimoxazole 34 73.9

Tetracyclines Tetracycline 8 17.39

Glycopeptides Vancomycin 34 74.1

Table IV. Resistance pattern of E. coli serogroups isolated from 
poultry meat.

Resistance patterns E. coli serotypes
CU-CO-VA 2
A-CU-CH 1

G-A-P-CH-VA 1
CU-CO 1

G-P-CU-CH-CO-VA 1
P-CU-CH 1

A-P-CU-VA 2
P-CI-CU-CO-VA 1

A-P-CI-CU-CH-VA 1
A-P-CI-CU-CH-CO-VA-T 1

A-P-CU-CO-VA-T 1
A-P-CU-VA-T 1

A-P-CI-CU-CO-VA-T 1
A-P-CH-CO-VA 1

A-P-CI-CH 1
A-P-CU-CH-CO-VA-T 2

G-AK-A-P-CI-CH-CO-T 1
G-A-P-CI-CU-CH-CO-VA 2

A-P-CU-CH-CO 3
G-A-P-CU-CO-VA 2

G-A-P-CO-VA 1
A-P-CU-CH-OF-VA 1
A-P-CU-CH-CO-VA 3

A-P-CU-CH-OF-CO-VA 1
A-P-CU-CH-CO 4

A-P-CO-VA 1
A-CU-CH-CO-VA-T 1
A-CU-CH-CO-VA 1
P-CU-CH-CF-VA 1

P-CU-CH-OF-CO-VA 1
A-P-CU-CF-CO-VA 1
A-P-CU-OF-CO-VA 1

P-CU-CH-CF-OF-VA 1
A-P-CU-CH 1

Total 46
Antibiotics tested for multiple resistance were: Cu = Cefuroxime;    G = Gentamicin; 
A = Ampicillin;    Ci = Ceftriaxone;    Ak = Amikacin;    Ch = Cephalothin; 
Cf = Ciprofloxacin;    Co = Co-trimoxazole;    P = Penicillin G;    Va = Vancomycin; 
Of = Ofloxacin;    T = Tetracycline.



202 Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2

E. coli in Eastern Indian poultry  Kaushik et al.

of resistance in E.  coli. The coexistence of virulent 
and resistant genes in a species may result in the 
emergence of hybrid plasmids (both resistance 
and virulence) among E.  coli. This, in turn, poses 
an increased public health risk (Szmolka and Nagy 
2013). In the present study, all isolates of E.  coli 
exhibited resistance against 2 or more antimicrobial 
agents, suggesting the presence of multi-drug 
resistant (MDR) E.  coli (Joshi et  al. 2012, Szmolka 
and Nagy 2013). The prevalence of such a large 
number of MDR E. coli indicates the widespread and 
extensive use of antibiotics in the area. Prevalence of 
such MDR E. coli has also been observed by Shakya 
and colleagues (2013) in human stool samples from 
India. The high rate of multiple antibiotic resistance 
against E.  coli also indicates the injudicious use of 
several antimicrobial agents for preventive and 
therapeutic purposes. These all pose serious threats 
to animal and human health.

The present investigation highlights the prevalence 
of pathogenic E. coli (ETEC and EPEC) in poultry meat, 
which is of importance in the field of zoonosis. The 
occurrence of high levels of resistance against most 
of the antibiotics and prevalence of virulent genes 
call for further attention, and the maintenance of 
strict hygienic measures in retail meat shops. The 
present findings also provide information about the 
occurrence of STEC in poultry in eastern India.

Acknowledgments
The authors are thankful to the Honorable Vice 
Chancellor, Bihar Agricultural University, Sabour, 
for providing necessary funds and Principal, Bihar 
Veterinary College, Patna for providing infrastructure 
and facilities to carry out the investigation. We are 
also thankful to the Director CRI, Kasauli, HP, India, 
for serotyping the isolates.

serogroups O8, O29, O111, and O60 are associated 
to enteropathogenic E. coli (Guth et al. 1989, Blanco 
et  al. 2004, Wani et  al. 2004, Bandyopadhyay et  al. 
2011). Thus our findings indicate that meat handlers 
and consumers are at risk of infection from STEC or 
enteropathogenic E. coli.

In this study, molecular characterisation for the 
presence of stx

1
 and stx

2
 genes showed the presence 

of stx
2
 gene in 13 (21%) isolates of E. coli. This finding 

is consistent with other findings from Farooq and 
colleagues (Farooq et  al. 2009) and Grossmann and 
colleagues (Grossmann et  al. 2005), who reported 
the stx

2
 gene in 11% and 9% of E. coli isolated from 

pigeons, respectively. Various authors reported the 
occurrence of the stx

2
 gene in O45, O18, O75, O64, 

O89, O91, O17, and O78 serogroups (Schmidt et  al. 
2000, Morabito et al. 2001, Farooq et al. 2009, Dutta 
et al. 2011). However, our findings demonstrate the 
presence of the stx

2
 gene in O29, O8, O42, and O1 

serogroups. This indicates a variable distribution of 
virulent genes among different serogroups of E. coli 
in different geographical area in India.

Antimicrobial resistance was observed at a range 
of 9-90%, which shows extreme variation in the 
susceptibility of poultry meat to E. coli. Our findings 
show maximum resistance against cefuroxime (a 
cephalosporin) followed by penicillin, ampicillin, 
and vancomycin. The high level of susceptibility 
against amikacin and ciprofloxacin that has been 
observed is consistent with the findings of other 
studies (Mishra et  al. 2002, Carraminana et  al. 2004, 
Jana and Mondal 2013). These findings might be the 
result of the indiscriminate use of these antibiotics 
in poultry or because of sub-therapeutic doses of 
these antimicrobial agents being administered 
for the prevention or control of infection. Other 
explanations include transmissible or plasmid 
mediated drug resistance and mutational changes 
in the genes that are crucial to the development 



203Veterinaria Italiana 2018, 54 (3), 197-204. doi: 10.12834/VetIt.330.1382.2

Kaushik et al.  E. coli in Eastern Indian poultry 

Bandyopadhyay S., Mahanti A., Samanta I., Dutta T.K., 
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