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22 © 2017 BLDE University Journal of Health Sciences | Published by Wolters Kluwer Medknow
Prevalence of efflux genes and ribosomal protection genes among tetracyclineresistant Aeromonas hydrophila isolated from diarrheic patients in Iraq Alaa Hani Al-Charrakh, Lubna Abdul-Muttalib Al-Shalah1
Abstract: OBJECTIVE: The aim of this study was to investigate the prevalence of tetracyclineresistant Aeromonas hydrophila isolated from clinical sources in Iraq, using polymerase chain reaction (PCR) technique. MATERIALS AND METHODS: A total of 822 samples were collected from patients suffering from diarrhea. Isolates were identified using biochemical tests, Vitek 2 system, and 16S rRNA specific primer. PCR was used to detect tetracyclineresistant isolates. RESULTS: Out of the 822 clinical samples collected, 13 Aeromonas spp. isolates (1.58%) were recovered, out of which eight isolates (61.53%) were identified as A. hydrophila. Results found that all tetracyclineresistant isolates carried at least one of the tet genes examined. Among efflux genes, tet (A) was most commonly observed in isolates, followed by efflux tet gene (tet B and C) and ribosomal protection protein (tet O). However, efflux genes tet (D and G) were not detected in any of the isolates. CONCLUSIONS: The prevalence of tet O chromosomal protection protein among A. hydrophila isolates was first recorded in Iraq and in many other neighboring countries. Keywords: Aeromonas hydrophila, clinical sources, efflux genes, ribosomal protection gene, tetracycline resistance
Members of the genus Aeromonas are facultatively anaerobic, rodshaped
oxidase positive, Gramnegative bacteria, and mesophilic and facultative anaerobic bacteria. Some species are pathogenic for animals and humans. Aeromonas species are widely distributed in the aquatic environment, including raw and processed drinking water and have been frequently isolated from various food products such as fish and shellfish, raw meat, vegetables, and raw milk. In addition, in recent years, aeromonades have been implicated as the
causative agents of human disease, ranging from gastroenteritis to wound infections.[1,2]
T h e g e n u s A e r o m o n a s c o m p r i s e s important human pathogens causing primary and secondary septicemia in immunocompromised persons, serious wound infections in healthy individuals and in patients undergoing medical leech therapy, and a number of less welldescribed illnesses such as peritonitis, meningitis, and infections of the eye, joints, and bones. Gastroenteritis, the most common clinical manifestation, remains controversial.[3]
Address for correspondence:
Department of Microbiology, College of Medicine, Babylon
University, Hilla, Babylon Governorate, Iraq.
Email: [email protected] com
Department of Microbiology, College of Medicine, Babylon University, 1Center of
Environmental Research, Babylon University, Hilla,
Iraq
Website: www.bldeujournalhs.in
DOI: 10.4103/bjhs.bjhs_53_16
How to cite this article: AlCharrakh AH, AlShalah LA. Prevalence of efflux genes and ribosomal protection genes among tetracyclineresistant Aeromonas hydrophila isolated from diarrheic patients in Iraq. BLDE Univ J Health Sci 2017;2:228.
This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
For reprints contact: [email protected]
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AlCharrakh and AlShalah: Tetracyclineresistant A. hydrophila from diarrheic patients
BLDE University Journal of Health Sciences Volume 2, Issue 1, JanuaryJune 2017 23
Aeromonas species are known to cause severe diarrheal disease of short duration or chronic loose stools in children, the elderly, or the immunocompromised individuals and they have been implicated in travelers’ diarrhea. They are commonly isolated from fecal sample of children <5 years old, whereas their isolation from other body sites usually occurred in adult populations.[4,5]
Tetracyclines belong to a family of broadspectrum antibiotics that inhibit protein synthesis in Grampositive and Gramnegative bacteria by preventing the binding of aminoacyltRNA molecules to the 30S ribosomal subunit and inhibiting protein synthesis,[6] contributing to higher levels of microbial resistance, especially among the genus Aeromonas.[5] The aim of this study was to evaluate the incidence and spreading of Aeromonas hydrophila isolated from diarrheic patients in Hilla city, Iraq, and study the tetracycline resistance at molecular level by detecting efflux pump genes and ribosomal protection protein genes responsible for tetracycline resistance among these isolates.
Materials and Methods
Sample collection and isolation of bacterial isolates This crosssectional study was designed to assess the occurrence of tetracyclineresistant A. hydrophila in patients with diarrhea. A total of 822 fecal samples were collected from rectal swab (routine work) and from patients suffering from diarrhea who were attending public health laboratory, Hilla city, Iraq. The period of specimen collection and analysis was extended from October 2015 to February 2016.
For isolation and identification of bacterial isolates, all specimens were cultured on alkaline peptone water, and then transferred to TCBS and MacConkey agar by swabbing and incubated at 37°C for 24 h. Each primary positive culture was identified depending on the morphological properties such as shape, swarming, odor, and lactose or nonlactose fermentation on MacConkey agar.[7] Different biochemical tests were used for the identification of bacterial isolates according to standard methods.[7,8] Vitek 2 system (BioMerieux, France) was used to confirm the identification according to the manufacturer’s instructions. Finally, identification was confirmed using 16S rRNAspecific primer using molecular technique (polymerase chain reaction [PCR]).
In light of antibiotic susceptibility results of our previous study,[9] eight tetracyclineresistant hydrophila isolates were detected using phenotypic methods. Out of the 822 clinical samples collected, 13 isolates (1.58%)
were belonged to Aeromonas spp., out of which eight A. hydrophila isolates (61.53%) were obtained. These bacterial isolates were identified as A. hydrophila based on their morphology, biochemical tests[8] in addition to Vitek 2 system, and as suggested previously.[9]
Extraction and quantification of DNA For genomic DNA extraction, a single colony of cultivated bacteria, which had been incubated overnight, was transferred to 2 ml of sterile Luria broth and incubated at 37°C for 18–20 h. The DNA was extracted and purified using Genomic DNA kit (EURx/Korea). All the clinical isolates were screened for chromosomal DNA according to manufacturer’s instructions. The total DNA was used to detect 16S rRNA, efflux pump, and ribosomal protection protein genes. For plasmid DNA extraction, a single colony of cultivated bacteria, which had been incubated overnight, was transferred to 2 ml of sterile Luria broth and incubated at 37°C for 18–20 h. The DNA was extracted and purified using highspeed mini DNA plasmid extraction kit (Geneaid Biotech, Taiwan) according to manufacturer’s instructions. Plasmid DNA was used to detect efflux genes.
Chromosomal and plasmid DNAs obtained were used as templates for all PCR experiments. The PCR reactions were carried out in a thermal cycler (Clever, UK). Before PCR assay, and to quantify the DNA concentration (ng/µL), the quantification of DNA samples was carried out by means of a spectrophotometric reading using 1 µL aliquots of genomic DNA with a NanoDrop™ spectrometer (NanoDrop Technologies, Inc., USA), adopting the manufacturer’s recommendations. The concentration of DNA was estimated from absorbance at 260 nm. DNA profiles were performed using bacterial DNA and loading buffer according to the manufacturer’s instructions (Bioneer, Korea).
Polymerase chain reaction protocols The DNA extracts of A. hydrophila isolates were subjected to different genes by PCR. The protocols used were according to manufacturer’s instructions. Different resistance primers of efflux protein genes (tet A, tet B, tet C, tet D, tet E), (tet G and tet L), and ribosomal protection protein genes tet (M) and tet (O) were used. In addition, specific primer (16S rRNA) was used for bacterial identification of A. hydrophila. Stock solution of these primers was prepared according to the information of manufactured company listed with primers. Primer types and sequences are shown in Table 1.
Five microliters of DNA was added to Master Mix, and then 10 µl of primer (3 µl for up and downstream, 4 µl free distal water) was added to the mix information labeled with Master Mix. The compassions were mixed
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AlCharrakh and AlShalah: Tetracyclineresistant A. hydrophila from diarrheic patients
24 BLDE University Journal of Health Sciences Volume 2, Issue 1, JanuaryJune 2017
carefully and then placed in a thermocycler (after incubation at 94°C for 5 min) and running according to conditions of each primer mentioned above. The following temperature profiles for PCR amplification of tetracyclineresistant gene fragments were applied over 40 cycles [Table 2].
After PCR, the profiles of amplification products were detected by gel electrophoresis according to the procedure of Sambrook and Russel.[12] Five microliters of the total reaction mixture was loaded on a 1.2% agarose gel and electrophoresed at 100 V at 70 mA for 60 min. The amplified DNA fragments were visualized by ultraviolet illumination after agarose gel electrophoresis and Ecodye (and ethidium bromide) staining by standard procedures.
Results
Results of the present study revealed that the following tet genes were detected: efflux (tet A, B, C, D, E, G, and L) genes and ribosomal protection protein (tet M and O) genes. Results found that all tetracyclineresistant isolates carried at least one of the tet genes examined [Table 3].
Regarding efflux genes, tet A was most commonly observed in A. hydrophila isolates (8), found in 6 (75%) [Figures 1 and 2], followed by tet B and tet C [Figures 1, 3, and 4]. Tet E efflux gene was found in two isolates [Figure 6] and tet L [Figure 8] in one isolate. However, efflux pump genes, tet D and G, were not detected in any of the A. hydrophila isolates tested [Figures 5 and 7].
Regarding ribosomal protection protein, tet O was detected in five isolates (62.5%) [Figure 9] and tet M [Figure 10] was detected in only one isolate (12.5%).
Table 1: Sequence and concentration of primers used in the study Target Primer Oligo sequence (5′→3′) Product (bp) References 16sRNA Forward CCA GCA GCC GCG GTA ATA CG 300 Nawaz et al.[10]
Reverse TAC CAG GGT ATC TAA TCC Tet A Forward GCT ACA TCC TGC TTG CCT TC 211
Reverse GCA TAG ATC GCC GTG AAG AG Tet B Forward TCA TTG CCG ATA CCA CCT CAG 391
Reverse CCAACCATCATGCTATTCCATCC Tet C Forward CTGCTCGCTTCGCTACTTG 897
Reverse GCCTACAATCCATGCCAACC Tet D Reverse TGTGCTGTGGATGTTGTATCTC 844
Forward CAGTGCCGTGCCAATCAG Tet E Reverse ATGAACCGCACTGTGATGATG 744
Forward ACCGACCATTACGCCATCC Tet G Reverse CGGCCAAGTGCCTGCGAGCCCTATGGGTC 241 Dorsch, 2007[11]
Forward CGGGAACACCATCCATCCCTGCGTGGC Tet L Reverse GGAACACATGAGTGTGTATTAGTTTTCTGG 311
Forward CCTACAATTGCTAATACCCTGTTCCCTCTG Tet M Reverse CCTAACATGTCATTTATATGGAGAAGACC 305
Forward CGAAAATCTGCTGGCGAGTACTGAACAGGGC Tet O Reverse CCGCCAAATCCTTTCTGGGCTTCTGTCGG 354
Forward CGCCCGTGAGAGATATTCCTGCGGTGC
Table 2: Polymerase chain reaction conditions for efflux protein genes and ribosomal protection genes Target Primer
denaturation Primer
annealing Primer
extension 16sRNA 94°C for 30 s 52°C for 30 s 72°C for 30 s Tet A 94°C for 30 s 63°C for 30 s 72°C for 30 s Tet B 94°C for 30 s 58°C for 30 s 72°C for 30 s Tet C 94°C for 45 s 65°C for 45 s 72°C for 10 s Tet D 94°C for 30 s 64°C for 30 s 72°C for 40 s Tet E 94°C for 45 s 65°C for 45 s 72°C for 10 s Tet G 94°C for 30 s 63°C for 30 s 72°C for 30 s Tet L 94°C for 30 s 52°C for 30 s 72°C for 30 s Tet M 94°C for 30 s 52°C for 30 s 72°C for 30 s Tet O 94°C for 30 s 62°C for 30 s 72°C for 30 s
Table 3: Genetic profile of efflux pump tet gene and ribosomal protection protein genes in Aeromonas hydrophila isolates Tet gene Aeromonas hydrophila isolate number
1 2 3 4 5 6 7 8 Tet A + + + + + − + − Tet B + + − + + + − − Tet C + + + − + − − + Tet D − − − − − − − − Tet E − − + − − − − + Tet G − − − − − − − − Tet L − − − + − − − Tet M − − − − + − − − Tet O + + + − − + + − +=Present, −=Absent
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AlCharrakh and AlShalah: Tetracyclineresistant A. hydrophila from diarrheic patients
BLDE University Journal of Health Sciences Volume 2, Issue 1, JanuaryJune 2017 25
Results revealed that tet O ribosomal protection protein gene was detected in 5 isolates (62.5%) of A. hydrophila [Figure 1]. To to our knowledge, this result is
the first record in Iraq and in many other neighboring countries.
Although few studies are available concerning tetracyclineresistant A. hydrophila isolated from human samples, results of this study revealed the prevalence of tetracyclineresistant A. hydrophila recovered from
Figure 1: Percentages of efflux pump genes and ribosomal protection genes of Aeromonas hydrophila
Figure 2: Ecodyestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas hydrophila isolates
and amplified with primer of tet A gene (211 bp)
Figure 3: Ecodyestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas hydrophila isolates
and amplified with primer of tet B gene (391 bp)
Figure 4: Ecodyestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas hydrophila isolates
and amplified with primer of tet C gene (897 bp)
Figure 5: Ethidium bromidestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas
hydrophila isolates and amplified with primer of tet D gene (844 bp)
Figure 6: Ethidium bromidestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas
hydrophila isolates and amplified with primer of tet E gene (744 bp)
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26 BLDE University Journal of Health Sciences Volume 2, Issue 1, JanuaryJune 2017
the clinical sources. The result of this study is the first record in Iraq.
Discussion
Using phenotypic methods, all A. hydrophila isolates (8) were determined previously as tetracycline resistant.[9] Regarding prevalence of tetracyclineresistant A. hydrophila recovered from the clinical sources, few studies are available concerning tetracyclineresistant A. hydrophila isolated from human samples. Results found that all tetracyclineresistant A. hydrophila isolates carried at least one of the tet genes examined. The result of this study is the first record in Iraq.
Most of the studies focused on tet genes of A. hydrophila in fish because the widespread nature of aeromonades is a result of their adaptation toward a different aqua medium including lakes, rivers, and drinking water.[13,14]
Furushita et al.[15] suggested that tet genes from fish farm bacteria have the same origins as those from clinical strains. They also found that sequence analysis indicated the identity in tet genes between the fish farm bacteria and clinical bacteria: 99.3%–99.9% for tet B, 98.2%–100% for tet C, 99.7%–100% for tet D, 92.0%–96.2% for tet G, and 97.1%–100% for tet Y.
Igbinosa and Okoh[16] assessed the prevalence of antibioticresistant Aeromonas species isolated from Alice and Fort Beaufort wastewater treatment plant in the Eastern Cape Province of South Africa and they found that tet C was not detected in any of the Aeromonas isolates. Balassiano et al.[17] analyzed the involvement of tet A and tet E genes in the tetracycline resistance of 16 strains of genus Aeromonas, isolated from clinical and food sources. PCR revealed that 37.5% of the samples were positive for tet A and also
Figure 7: Ecodyestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas hydrophila isolates
and amplified with primer of tet G gene (241 bp) Figure 8: Ethidium bromidestained agarose gel electrophoresis (1.2%) of
polymerase chain reactionamplified products from extracted DNA of Aeromonas hydrophila isolates and amplified with primer of tet L gene (311 bp)
Figure 9: Ethidium bromidestained agarose gel electrophoresis (1.2%) of polymerase chain reactionamplified products from extracted DNA of Aeromonas
hydrophila isolates and amplified with primer of tet O gene (354 bp) Figure 10: Ethidium bromidestained agarose gel electrophoresis (1.2%) of
polymerase chain reactionamplified products from extracted DNA of Aeromonas hydrophila isolates and amplified with primer of tet M gene (305 bp)
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BLDE University Journal of Health Sciences Volume 2, Issue 1, JanuaryJune 2017 27
37.5% were tet E positive. One isolate was positive for both genes.
The prevalence of efflux gene (tet A) (75%) of A. hydrophila was also reported by several authors. Jacobs and Chenia[18] isolated Aeromonas spp. from South African aquaculture systems and they reported the prevalence of tet A and tet E genes. They reported that single and multiple class A family tet determinants were observed in 27% and 48.7% of isolates, respectively, with tet A being the most prevalent tet determinant type. Hedayatianfard et al.[19] showed that the most widely distributed resistance gene was gene tet A and at the least known resistance gene was tet M among the studied bacteria of the genus Aeromonas. On the other hand, Andersen and Sandaa[20] reported that tet A determinant was detected in only 5% of the isolates and tet D was detected in 4% of the isolates. While they found that tet E was found in 63% of isolates and it was the most widespread determinant in bacterial isolates obtained from polluted and unpolluted marine sediments in Norway and Denmark.
Results of this study found that efflux pump genes (tet D and tet G) were not detected in any of the A. hydrophila isolates. In contrast, several authors reported the prevalence of efflux tet gene (tet D) in A. hydrophila isolated from fish pathogens.[21] In conclusion, the data from other studies showed that bacterial isolates from aquaculture sources in Australia harbor a variety of tetracyclineresistant genes; tet A, tet D, tet E, and tet M genes were found in Aeromonas spp., while no tet B, tet C, or tet Y determinants were detected.[22]
Interestingly, one of our isolates also contained both tet A and tet E genes. Therefore, it is evident that tetracyclineresistant determinants such as tet E, tet A, and tet D (in that order) are also present in aquaculture in Australia, just as in other geographical regions. However, the widespread occurrence of tet M in this isolates is not surprising because this class of tetracyclineresistant determinant has been recently described in aquaculture.[23]
Furushita et al.[15] in a study of 66 tetresistant strains isolated from fishes collected at three different fish farms located in the southern part of Japan reported a prevalence of tet B in 31 of tetresistant bacteria, and then tet Y in six, and tet C and tet D in four strains.
Jacobs and Chenia[18] reported the occurrence of more than one tetresistant genes with the majority of isolates possessing two tet determinants with the tet A and tet E as well as tet B and tet D/tet H combination being observed. Three tet genes (tet D, tet E, and tet M) were found in two strains of Aeromonas spp.
Conclusions
The prevalence of tetracyclineresistant A. hydrophila recovered from the clinical sources in this study is the first record in Iraq. Very few studies are available concerning tetracycline resistance in A. hydrophila isolated from human samples. Furthermore, it can be concluded that the prevalence of tet O chromosomal protection protein among A. hydrophila isolates in the present study was first recorded in Iraq and in many other neighboring countries.
Financial support and sponsorship Nil.
Conflicts of interest There are no conflicts of interest.
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