https://doi.org/10.52973/rcfcv-e34445
Received: 28/04/2024 Accepted: 08/07/2024 Published: 19/09/2024
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Revista Científica, FCV-LUZ / Vol. XXXIV, rcfcv-e34445
ABSTRACT
It was aimed to isolate Escherichia coli from infected trouts in
different farms, and to investigate antibiotic susceptibility proles
and antibiotic resistance genes of these isolates. Identication
processes were carried out according to ISO 6887–3:2017 and ISO
16654:2001 guidelines. Antimicrobial susceptibility was tested
according to the Clinical and Laboratory Standards Institute (CLSI)
guidelines. Extended–spectrum beta–lactamase (ESBL) resistant
strains were investigated by the Modied Double Disc Synergy Test
(MDDST) method. The specic regions of 15 genes were analyzed by
the real–time PCR system. As a result, 24 isolations were performed
from different tissues belonging to eight out of 108 diseased trouts.
The highest phenotypical resistance status was found against
penicillins (ampicillin 100%, amoxicillin 91.67%) and rst–generation
cephalosporins (cefazolin 100%). Phenotypic resistance rates of
amoxicillin–clavulanate, nalidixic acid, and erythromycin were 83,33%,
tetracycline was 75%, ceftazidime, ceftriaxone, cefotaxime, cefepime,
and ciprooxacin were 66,67%, trimethoprim‐sulfamethoxazole was
50%, and chloramphenicol and gentamycin were 33.33%. Phenotypical
resistances for amikacin and imipenem were detected at the level of
16.67%. In addition, ESBL production was detected phenotypically in
12 (50%) out of 24 E. coli isolates. The highest antimicrobial resistance
gene rate was 58.33% for tetA. Gene regions of sull, ermB, ermF,
qnrB, suIll, qnrS, and tetB were detected at 50%, 50%, 50%, 33.33%,
25%,16.67%, and 16.67% respectively. None of the isolates included
the gene region of the qnrA, qnrC, qnrD, and qepA. ESBL–producing
genes, blaTEM, blaCTX, and blaSHV were detected at 33.33%, 33.33%,
and 16.67% respectively. In conclusion, E. coli contamination of the
water can cause infections among sh and increase the agent’s
antimicrobial resistance. Resistant strains of E. coli cannot only
cause nancial damage to create yield loss but also can threaten
human health by causing infections throughout the food chain.
Key words: Aquaculture; antibiotic susceptibility; E. coli; isolation;
resistance genes
RESUMEN
Con el objetivo de aislar Escherichia coli de truchas infectadas
en diferentes granjas, e investigar los perles de susceptibilidad
a los antibióticos y los genes de resistencia a los antibióticos de
estos aislados. Los procesos de identicación se llevaron a cabo
de acuerdo con las directrices ISO 6887–3:2017 e ISO 16654:2001.
La susceptibilidad antimicrobiana se probó de acuerdo con las
directrices del Instituto de Normas Clínicas y de Laboratorio (CLSI).
Las cepas resistentes a betalactamasas de espectro extendido
(EBSL) se investigaron mediante el método de prueba de sinergia
de doble disco modificado (MDDST). Se analizaron las regiones
especícas de 15 genes mediante el sistema PCR en tiempo real.
Como resultado, se realizaron 24 aislamientos a partir de diferentes
tejidos pertenecientes a ocho de las 108 truchas enfermas. El mayor
estado de resistencia fenotípica se encontró frente a penicilinas
(ampicilina 100%, amoxicilina 91,67%) y cefalosporinas de primera
generación (cefazolina 100%). La tasa de resistencia fenotípica a
la amoxicilina–clavulánico, el ácido nalidíxico y la eritromicina fue
del 83,33%, la de la tetraciclina del 75%, la de la ceftazidima, la
ceftriaxona, la cefotaxima, la cefepima y la ciprooxacina del 66,67%,
la del trimetoprim–sulfametoxazol del 50%, y la del cloranfenicol y
la gentamicina del 33,33%. La resistencia fenotípica a la amicaína y
al imipenem se detectó a un nivel del 16,67%. Además, se detectó
fenotípicamente la producción de ESBL en 12 (50%) de los 24 aislados
de E. coli. La tasa más alta de genes resistentes a los antimicrobianos
fue del 58,33% para tetA. Las regiones génicas de sull, ermB, ermF,
qnrB, suIll, qnrS y tetB se detectaron en un 50%, 50%, 50%, 33,33%,
25%,16,67% y 16,67% respectivamente. Ninguno de los aislados incluía
la región génica de qnrA, qnrC, qnrD y qepA. Los genes productores de
ESBL, blaTEM, blaCTX y blaSHV se detectaron en un 33,33%, 33,33%
y 16,67% respectivamente. En conclusión, la contaminación del agua
por E. coli puede causar infecciones entre los peces y aumentar la
resistencia antimicrobiana del agente. Las cepas resistentes de E.
coli no sólo pueden causar perjuicios económicos al crear pérdidas
de rendimiento, sino que también pueden amenazar la salud humana
al provocar infecciones en toda la cadena alimentaria.
Palabras clave: Acuicultura; sensibilidad a los antibióticos; E. coli;
aislamiento; genes de resistencia
Antibiotic susceptibility and resistance genes of Escherichia coli isolates
from diseased rainbow trouts (Oncorhynchus mykiss)
Susceptibilidad a los antibióticos y genes de resistencia de aislados de Escherichiacoli
procedentes de truchas arco iris (Oncorhynchus mykiss) enfermas
Ahmet Murat Saytekin
1
* , Muhammed Yaşar Dörtbudak
2
, Hikmet Dinç
3
, Mehmet Demirci
4
, Akın Yiğin
5
, Emine Atçı Saytekin
6
1
Harran University, Faculty of Veterinary Medicine, Department of Microbiology. Şanlıurfa, Türkiye.
2
Harran University, Faculty of Veterinary Medicine, Department of Fisheries and Diseases. Şanlıurfa, Türkiye.
3
Gaziantep Islam Science and Technology University, Faculty of Medicine, Department of Pharmacology. Gaziantep, Türkiye.
4
Kırklareli University, Faculty of Medicine, Department of Medical Microbiology. Kırklareli, Türkiye.
5
Harran University, Department of Genetics, Faculty of Veterinary Medicine. Şanlıurfa, Türkiye.
6
Harran University, Faculty of Arts and Science, Department of Biology, Şanlıurfa, Türkiye.
*Corresponding Author: ahmetmurat.saytekin@harran.edu.tr
Antibiotic susceptibilities and resistance genes of E. coli from trouts / Saytekin et al. ______________________________________________
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INTRODUCTION
With the increasing demand for seafood, intensive shing activities
are increasing daily. On the other hand, with the gradual decrease
of physical and biological capacity due to worsening environmental
conditions, and increases in shing costs, it has been understood
that the sh production that can be obtained through conventional
shing will not increase at the needed pace. However, aquaculture
can meet this high demand that traditional sheries cannot reach.
Additionally, it is developing in the world and creates an important
trade opportunity for countries and human livelihood [1].
Thanks to a similar increase in national demand, there have
been great developments in aquaculture in the 29 trout production
facilities located in Karkamış Dam Lake in the Birecik district of
Şanlıurfa province in recent years. Current development has driven
capacity increases and accordingly, increases in sh production.
With support from the Ministry of Agriculture and Forestry for sh
farming, the total production capacity of aquaculture facilities within
the borders of Karkamış Dam Lake reaches 16.012 tons/year as of
February 20, 2015 [2].
Bacterial pathogens such as Escherichia coli, Campylobacter
spp., Salmonella spp., Shigella spp., Yersinia enterecolitica, Listeria
monocytogenes, and Vibrio spp. are responsible for 75% of sh–borne
food infections in humans. For this reason, in aquaculture, various
antibiotics are applied in the form of oral or premixed by adding to
the feed, both for ghting and protection against such pathogens.
While most oxytetracycline is used for this purpose in the world,
orfenicol, sulfadiazine + trimethoprim, enrooxacin, and amoxicillin
are used as licensed antibiotics in Türkiye [3, 4]. If infected sh are
not treated with antibiotics, mortality rates can reach 60% to 80%
cumulatively in farms and may cause serious losses in production [5].
He et al. [6] stated that using low doses of antibiotics as growth
promoters is banned in most countries because it increases the
development of antibacterial resistance, and that illegal usage may
be too large to be ignored. They showed that by modeling in zebrash,
using low doses of antibiotics causes immunosuppression in sh over
a long time and negatively affects the intestinal microbiota of sh
resulting in increased susceptibility to pathogens. In Türkiye, antibiotics
used in sh are sold and applied with a veterinarian’s prescription. In
addition, according to the “Medicated Feed Communiqué” of the Ministry
of Agriculture and Forestry numbered 2005–12, which entered into
force in 2005, it is forbidden to add antibiotics and pharmaceutical
substances to feed as feed additives (as protection against pathogens
or growth promoters). In case of an outbreak of any disease in the
animals, and if the medication will be used on the animals with the
feed, it is allowed to produce medicated feed only in feed factories.
Factors such as the use of antibiotics in wrong doses, non–
compliance with dose times, immediate empirical treatment, and
illegal antibiotics can cause high selective pressure to resistance to
antibiotics in some pathogens [7]. It is thought that transmission of
resistance genes may be realized if these pathogens encounter other
bacterial agents. This situation may increase the resistance proles
of the bacteria. For the reason of formed antibacterial resistance
the doses of antibiotics used against bacterial diseases in people
are either increased or new types of antibiotics are used [8, 9, 10, 11].
The researchers stated that the physicochemical properties of the
water in the dams where sh production activities are carried out
may change according to the seasons, and urban, agricultural and
industrial wastes are the most important factors affecting water
quality. They stated that pollutant elements could be physical,
chemical, or biological according to their sources, and in this context,
“many parameters such as temperature, pH, dissolved oxygen content,
electrical conductivity, turbidity, nitrite, nitrate, phosphate, biological
oxygen demand, and chemical oxygen demand can be accepted as
criteria”, especially in surface waters in determining water quality and
pollution level. In the water analyses, researchers conducted between
January 2015 and December 2015 in Karkamış Dam Lake, they reported
that the surface water and the water column between 0–8 m depths
are in class I, high–quality water class according to the classes and
quality criteria of the surface water quality management regulation
in terms of general chemical and physicochemical parameters of
continental surface water resources [12].
In this study, it was aimed to investigate the presence of E. coli
in tissues such as muscle, liver, kidney, and gill of infected trouts
detected in trout farms in Karkamış Dam Lake and to evaluate the
antibiotic susceptibility proles of E. coli isolates from these different
tissues of infected sh.
MATERIALS AND METHODS
Collection and preparation of samples
This study was carried out with 108 infected sh provided in nine
different trout farms in Karkamış Dam Lake between May 2022 and
March 2023. Nine different farms were visited every two months.
Two sh samples were taken from each farm on each visit. The sh
were taken into sterile sample containers and placed in refrigerated
isothermal boxes and quickly delivered to the veterinary clinic. In
the clinic, 4 different tissue samples (Liver, kidney, muscle, and
gill) were taken from each sh by aseptic surgical techniques, and
approximately 20 g of tissue samples were placed in stomacher bags
containing 200 mL of transport medium (buffered peptone water)
and delivered to the laboratory [13].
Bacterial identication
Escherichia coli identication and microbiological analyses in sh
samples were performed according to ISO 6887–3:2017 [14] and ISO
16654:2001 [15] guidelines. The stomacher bags delivered to the
laboratory were incubated in an incubator (Panasonic, MCO–18AC–PE,
Japan) at 41.5°C for 6 hours (h). After incubation, the bag contents
were homogenized using a homogenizer. After taking the amount of
200 μL sample from each bag contents using a ltered pipette tip, the
samples were inoculated on Sorbitol–MacConkey (SMAC) agar (Becton
Dickinson GmbH), and these petri dishes were incubated at 37°C for
24 h. E. coli colonies that do not ferment sorbitol and were negative
for slide agglutination using the E. coli O157 latex test kit (Oxoid) were
inoculated on Levine Eosin Methylene Blue agar (L–EMB) (Merck) and
incubated for 24 h at 37°C. Indole, citrate, and Voges–Proskauer tests
were also used for biochemically characterizing [16].
Antimicrobial susceptibility tests
Antimicrobial susceptibility tests were performed using the Kirby–
Bauer disc diffusion method. First, the bacterium was swabbed on
Mueller Hinton Agars (Oxoid), then antimicrobial discs were placed on
the agar surface carefully, and then the plates were incubated at 37°C
for 24 h. Inhibition zones formed around the discs after incubation
were measured and the results were evaluated according to the
TABLE I
Distribution of Phenotypical Antibiotic Resistance
Nº Tissues Farm Nº Fish Nº AM AX AMC CZ CAZ CRO CTX CPM C NA CIP TE SXT AMK GEN IPM E ESBL
1 L 1 1 R R R R R R R R R R R R R R R R R +
2 K 1 1 R R R R R R R R R R R R R R R R R +
3 M 1 1 R R R R R R R R R R R R R R R R R +
4 G 1 1 R R R R R R R R R R R R R R R R R +
5 K 2 2 R R R R S S S S S R S S S S S S R –
6 M 2 2 R R R R S S S S S R S S S S S S R –
7 L 2 3 R R R R S S S S S R S S S S S S R –
8 G 2 3 R R R R S S S S S R S S S S S S R –
9 L 3 4 R R R R R R R R S R R R R S S S R +
10 K 3 4 R R R R R R R R S R R R R S S S R +
11 M 3 4 R R R R R R R R S R R R R S S S R +
12 G 3 4 R R R R R R R R S R R R R S S S R +
13 L 4 5 R R R R R R R R S R R R S S S S R –
14 K 4 5 R R R R R R R R S R R R S S S S R –
15 M 4 5 R R R R R R R R S R R R S S S S R –
16 G 4 5 R R R R R R R R S R R R S S S S R –
17 K 5 6 R S S R S S S S S S S R R S S S S –
18 G 5 6 R S S R S S S S S S S R R S S S S –
19 L 6 7 R R S R S S S S S S S S R S S S S –
20 G 6 7 R R S R S S S S S S S S R S S S S –
21 L 7 8 R R R R R R R R R R R R S S R S R +
22 K 7 8 R R R R R R R R R R R R S S R S R +
23 M 7 8 R R R R R R R R R R R R S S R S R +
24 G 7 8 R R R R R R R R R R R R S S R S R +
L: Liver, K: Kidney, M: Muscle, G: Gill, R: Resistant, S: Sensitive, AM: Ampicillin, AX: Amoxicillin, AMC: Amoxicillin–clavulanate, CZ: Cefazolin, CAZ: Ceftazidime, CRO: Ceftriaxone, CTX:
Cefotaxime, CPM: Cefepime, C: Chloramphenicol, NA: Nalidixic acid, CIP: Ciprooxacin, TE: Tetracycline, SXT: Trimethoprim‐sulfamethoxazole, AMK: Amikacin, GEN: Gentamicin,
IPM: Imipenem, E: Erythromycin, ESBL: Production of Extended Spectrum β–lactamases
_____________________________________________________________________________Revista Cientifica, FCV-LUZ / Vol. XXXIV, rcfcv-e34445
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Clinical and Laboratory Standards Institute (CLSI) guidelines [17].
Ampicillin, amoxicillin (penicillins), amoxicillin–clavulanate (penicillins
+ beta–lactamase inhibitors), cefazolin (1
st
generation cephalosporins),
ceftazidime, ceftriaxone, cefotaxime (3
rd
generation cephalosporins),
cefepime (4
th
generation cephalosporins), nalidixic acid, ciprooxacin
(quinolones), tetracycline, trimethoprim‐sulfamethoxazole (folate
pathway inhibitors), amikacin, gentamicin (aminoglycosides), imipenem
(carbapenems) and erythromycin (macrolides) discs (Oxoid) were used as
antimicrobial agents and their antimicrobial susceptibility was tested.
Phenotypic detection of ESBL production
Isolates were tested to determine whether they produce extended–
spectrum beta–lactamases (ESBL) on Mueller–Hinton agar plates
using the MDDST method [18, 19]. An amoxicillin–clavulanate disc
(20/10 μg) and four cephalosporins were used for the determination
and evaluation of ESBL according to the CLSI guidelines [17, 18, 19].
Investigation of antimicrobial resistance genes
After 24 h of incubation at 37°C on L–EMB agar, E. coli colonies were
placed in a sterile microcentrifuge tube (Isolab, Germany) containing PBS
and adjusted to 0.5 McFarland standard. DNA isolations were made from
200 μL of this mixture using the High Pure PCR template preparation
kit (Roche Diagnostics GmBH, Mannheim, Germany) according to the
manufacturer’s instructions. DNAs were stored in deep freeze (Nüve,
DF–590, Türkiye) at -80°C until the qPCR. BlaTEM, blaSHV, blaCTX
(ESBL production genes), qnrA, qnrB, qnrC, qnrD, qnrS, qepA (quinolone
resistance genes), tetA, tetB (tetracycline resistance genes), sulI, sulII
(sulphanamide resistance genes), and ermB and ermF (erythromycin
resistance genes) were detected using the LightCycler 480 real–time
PCR system (Roche, Switzerland) with specic primers by following the
manufacturer’s instructions of LightCycler 480 SYBR Green I Master
kit (Roche Diagnostics GmBH, Mannheim, Germany). The total reaction
volume was 20 µL and the template DNA added 5 µL [20, 21, 22].
RESULTS AND DISCUSSION
Twenty–four E. coli isolates were detected in different tissues
of eight infected sh from the farms except numbers eight and
nine (TABLE I). The phenotypically antibiotic resistance and ESBL
distribution of the isolates from tissues is given in TABLE I.
While the highest resistance was found against penicillin and rst–
generation cephalosporins, resistance to imipenem was detected at
16.67%. It was noticed that the rates of resistance to tetracyclines and
quinolones, which are frequently used in sheries, were high (TABLE
II). In addition, phenotypically extended–spectrum beta–lactamase
production was detected in 12 (50%) of the 24 E. coli isolates (TABLE II).
The distribution of antimicrobial resistance genes from all E. coli
isolates obtained by culture from different tissues is given in TABLE III.
The highest antimicrobial resistance gene rate among the
isolates included in this study was 58.33% for the tetracycline (tetA).
Sulfonamide resistance gene suI and Erythromycin resistance genes
TABLE II
Antibiotic resistance rates of the isolates
Antimicrobial Groups Antimicrobials
N° Resistant
Strains
Resistance
Ratio
Penicillins
Ampicillin 24 100.00
Amoxicillin 22 91.67
Penicillins + beta–lactamase
inhibitors
Amoxicillin–
clavulanate
20 83.33
1
st
generation cephalosporin Cefazolin 24 100.00
3
rd
generation cephalosporins
Ceftazidime 16 66.67
Ceftriaxone 16 66.67
Cefotaxime 16 66.67
4
th
generation cephalosporins Cefepime 16 66.67
Phenicols Chloramphenicol 8 33.33
Quinolones
Nalidixic acid 20 83.33
Ciprooxacin 16 66.67
Tetracyclines Tetracycline 18 75.00
Folate pathway inhibitors
Trimethoprim‐
Sulfamethoxazole
12 50.00
Aminoglycosides
Amikacin 4 16.67
Gentamicin 8 33.33
Carbapenems Imipenem 4 16.67
Macrolides Erythromycin 20 83.33
Modied Double Disc Synergy Test (MDDST) 12 50.00
TABLE III
Distribution of resistance genes of the isolates
N° Tissue Farm N° Fish N° blaTEM blaSHV blaCTX qnrA qnrB qnrC qnrD qnrS qepA tetA tetB sulI sulII ermB ermF
1 L 1 1
+ + + + + + + +
2 K 1 1
+ + + + + + + +
3 M 1 1
+ + + + + + + +
4 G 1 1
+ + + + + + + +
5 K 2 2 + + +
6 M 2 2 + + +
7 L 2 3 + + +
8 G 2 3 + + +
9 L 3 4
+ + + + +
10 K 3 4
+ + + + +
11 M 3 4
+ + + + +
12 G 3 4
+ + + + +
13 L 4 5 + +
14 K 4 5 + +
15 M 4 5 + +
16 G 4 5 + +
17 K 5 6 + + +
18 G 5 6 + +
19 L 6 7 +
20 G 6 7 + +
21 L 7 8 + + +
22 K 7 8 + + +
23 M 7 8 + + +
24 G 7 8 + + +
M: Muscle, L: Liver, K: Kidney, G: Gill
TABLE IV
Percentages of the resistance genes of the isolates
Eected Antimicrobial Genes Positivity Percentage (%)
Extended–spectrum beta–lactamase
(ESBL) producing genes [
21]
blaTEM 8 33.33
blaSHV 4 16.67
blaCTX 8 33.33
Quinolone resistance genes [20]
qnrA 0 0.00
qnrB 8 33.33
qnrC 0 0.00
qnrD 0 0.00
qnrS 4 16.67
qepA 0 0.00
Tetracycline resistance genes [22]
tetA 14 58.33
tetB 4 16.67
Sulphonamide resistance genes [22]
sulI 12 50.00
sulII 6 25.00
Erythromycin resistance genes [22]
ermB 12 50.00
ermF 12 50.00
Antibiotic susceptibilities and resistance genes of E. coli from trouts / Saytekin et al. ______________________________________________
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ermB and ermF were detected in 50% of the isolates. QnrB associated
with quinolone resistance, and blaTEM and blaCTX responsible for the
production of extended–spectrum beta–lactamases were detected
in 33.33% of the isolates (TABLE IV).
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proles were detected against antibiotics licensed for sh diseases and
antibiotics that have been in use for a long time all over the world, while
low rates of phenotypic antibiotic resistance proles were detected
against relatively newly discovered antibiotics, and not licensed for use
in sh diseases (TABLE II). This was considered a possible result of a
combination of antibiotic misuse, antibiotics in use for long periods,
and the ability of bacteria to develop resistance [11]. It is seen that
the phenotypic resistance proles detected vary between farms. This
difference may be due to the management of the farms, the variety of
antibiotic drugs used for treatment, differences in doses and duration
of use, incorrect antibiotic use, differences in the origin of the isolates,
and possible gene transfers through various means. Especially in farm
numbered one, the presence of isolates resistant to all antibiotics
tested in this study is noteworthy.
The rates of resistance genes detected against the antibiotics
investigated in this study are compatible with phenotypic resistance
rates. However, this agreement is not one hundred percent. The
greatest agreement is between the rates of tetracycline resistance
genes and the rates of phenotypic resistance to tetracycline. In their
studies on the development of antibiotic resistance, researchers
address hereditary resistance. They reported that for differentiation
in phenotypic resistance, either mutation must occur or antibiotic–
resistance genes must be acquired through gene transfer. However,
researchers have reported that phenotypic resistance can in some
cases be acquired without any genetic modication, that it may
be associated with specic processes such as growth in biolms,
a stationary growth phase or persistence, drug indifference, and
changes in bacterial permeability, and that phenotypic resistance to
antibiotics is a complex phenomenon that depends on the metabolic
state of bacterial populations [11, 29].
ESBL gene regions were detected in sh isolates numbered one,
four, and eight. In addition, it was determined that the isolates
belonging to fish numbered one contained all three ESBL gene
regions. The detection of different molecular class ESBL gene regions
in this study suggests the possible presence of horizontal gene
transfer. All isolates included ESBL gene regions in this study were
determined to produce ESBL phenotypically. This high concordance
is similar to a study conducted previously [30].
CONCLUSIONS
According to the ndings of this study, these bacteria can be
detected in fish farms in Türkiye and they have the potential to
produce serious antimicrobial resistance genes. Also, the detection
of E. coli in sh samples could be accepted as an indicator of fecal
contamination. It was thought that both ndings, the presence of
the contamination and the antimicrobial resistance genes, could be
dependent on the lack of infrastructure, management, and regulation
in sh farms, and erroneous antimicrobial usage.
Recommendations
The lack of follow–up data on the strains that can be detected
in these farms, their resistance proles, and the status of genes
that can cause resistance is noteworthy. It is predicted that in the
future, new gene editing technologies such as CRISPR and new drugs
to be produced with nanotechnology will play an important role in
the treatment of infections caused by bacterial strains resistant to
existing antimicrobials. However, in order to use the currently available
antimicrobials, erroneous antimicrobial use should be avoided and
In recent years, interest in aquaculture has increased in many
different parts of the world. On the other hand, due to the deciencies
in biosafety principles, especially in developing countries, the use of
antimicrobials especially for poultry is increasing for the treatment
of diseases of sh, and this causes bacteria to develop resistance
to these antimicrobials [23]
When the antibiotic resistance results of the bacteria isolated from
some sh species in Iskenderun Bay were examined by Matyar et al.
[24] the resistance to IPM could not be determined in bacteria isolated
from the gills, while this rate was reported as 5.3% in intestinal
isolates. In the same study, 12.9% of bacteria isolated from gills
were resistant to TE, while this rate was 5.3% in intestinal isolates,
while SXT resistance was 3.2% in gill isolates and 9.3% in intestinal
isolates. In this study, high resistance was observed against penicillin
and rst–generation cephalosporins.
The resistance rates detected in the study on the antibiotic
resistance levels of E. coli strains isolated from Giresun Batlama
Deresi were found lower than in this current study. In the study,
ampicillin 59%, tetracycline 50.8%, nalidixic acid 44.4%, erythromycin
42.9%, chloramphenicol 38.1%, cefazolin 36%, cefuroxime 35.9%
and cefotaxime 28.4%, were found respectively. Value (CAD) rate
was found 73.28% [25].
Gufe et al. [26] investigated the antibiotic susceptibility levels
in isolated bacteria from 36 sh samples collected from the public
market. While all isolates were susceptible to gentamicin, lincomycin
(100%), ampicillin (81%), penicillin (67%), erythromycin (65%),
tetracycline (63%), neomycin (61%), cloxacillin (43%), kanamycin
(24%) and sulfamethoxazole (13%) antibiotic resistance rates were
observed. The detected ampicillin resistance rate was 81%, lower
than the current study (100%). This shows that due to the resistance
developed against penicillin derivatives in the sh farms where the
study was conducted, alternative antibiotics should be used as
alternatives to such drugs.
In their study conducted by Zhang et al. [27] they detected
resistance genes such as blaTEM, qnr, sul, and tetA, as well as
resistance genes such as blaTEM, qnr, sul, and tetA, in seven sh they
detected in sh farms, as well as a resistance gene against colistin,
an antimicrobial used in the treatment, especially in the case of
carbapenem resistance, and that these strains can be quite resistant.
Ryu et al. [28] reported that they detected 6.7% of E. coli in
commercially sold sh collected in South Korea and they found
more than 30% resistance to tetracycline in their origins. When
they examined the resistance genes, they reported that blaTEM was
detected at a rate of 21% and tetD at a rate of 41%.
In their study in Lebanon, Hassuna et al. [19] reported that when
they examined the E. coli strains of six sh with the Whole–Genome
Sequencing method, they detected blaTEM, erm, suI, and tetA
resistance, and they also detected mcr resistance, which may cause
colistin resistance, in the isolates of these sh. All these study data
support current study data. It was observed that different genes that
can affect many antimicrobial groups in E. coli strains detected in
the study were produced by these strains.
In this study, phenotypic resistance proles were detected at various
rates against all antibiotics tested. Contrary to Matyar et al. [24], the
same phenotypic proles were detected among the tissue isolates of
the sh from which bacteria were isolated, and no differences were
observed. In general, high rates of phenotypic antibiotic resistance
Antibiotic susceptibilities and resistance genes of E. coli from trouts / Saytekin et al. ______________________________________________
6 of 7
these farms should be followed with official protocols. Since the
resistance genes of these bacteria have the potential to reach humans
through water and sh, they can pose a high risk to animal and human
health. It is advised that these farms should be kept in mind within the
framework of a single health perspective and they should be followed
up, and similar studies should be carried out in other farms.
Conict of Interest
The authors declared no conict of interest.
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