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ISSN: 0975-8585
January–February 2016 RJPBCS 7(1) Page No. 590
Research Journal of Pharmaceutical, Biological and Chemical
Sciences
Molecular and Phenotypic Study of Virulence Genes in a Pathogenic Strain of
Pseudomonas aeruginosa isolated from various clinical origins by PCR:
Profiles of genes and Toxins.
Lena Fadhil
1
, Ali Hussein Al-Marzoqi
2
*, Zahraa Mohammad Al Taee
3
,
and Ammar A Shalan
4
1
College of Pharmacy, Babylon University, Iraq.
2
College of Science for Women, Babylon University, PO box 435, Al-Hillah city, Babylon, Iraq.
3
College of Science, Babylon University, Iraq.
4
College of Nursing, Babylon University, Iraq.
ABSTRACT
Most infections associated with bacteria like Pseudomonas Aeruginosa owns a variability virulence
factors elements which can increase bacterial pathogenicity and infection severity. This study was aimed to
revealed pathogenic genes which are related to bacterial virulence by PCR technique of P. aeruginosa isolated
from various clinical cases, with the aim to discover the connection of these pathogenic elements related to
special P. Aeruginosa infections. Strains of P. aeruginosa (n = 286) were gathered in time between April 2014
and April 2015 at the medical Laboratory, private clinic laboratory and burning wards at Educational Hospital
at Babil province then transport specimens for cultivating and identification. DNA (Plasmid) disjointed and
isolated using standard distinct methods. Several structural and virulence genes of Ps. aeruginosa including
(plcH, algD, rhlI, exoS, exoU, lasR, toxA, aprA, rhlAB, fliC, lecA, toxR, lasI, oprI, oprL, rhlR, nan1, lasB) were
amplified using the PCR technique by expending precise primers designed by using Primer3Plus, PCR condition
and sequencing of each primer pair. Ps. aeruginosa own genes that have the ability for encoding: plcH, algD,
rhlI, exoS, exoU, lasR, toxA, aprA, rhlAB, fliC, lecA, toxR, lasI, oprI, oprL, rhlR, nan1, lasB. Virulence genes
prevalence among P. aeruginosa isolates (n=286) were as follows: lasI 3.5%, lasR 2.0%, rhlI, 2.4%, rhlR 4.3%,
toxA 9.9%, aprA 2.1%, rhlAB 2.6%, plcH 10.5%, lasB 10.6%, fliC 2.5%, lecA 4.7%, algR 10.4%, toxR 4.7%, oprI
6.4%, oprL 7.5%, nan1 2.0%, exoS 9.4%, exoU 4.5%. Blood infections revealed the highest ratio in virulence
genes from all infection 24 (20.9 %), followed Burn infections 86 (17.4%), UTI 92 (16.6%), Wound 33 (15.5%),
LRTI 16 and URTI 35 (15%).
Keywords: Pseudomonas aeruginosa, virulence genes, PCR, Plasmid Curing.
*Corresponding author
ISSN: 0975-8585
January–February 2016 RJPBCS 7(1) Page No. 591
INTRODUCTION
Pseudomonas Aeruginosa infections deliberated as multifactorial, as proposed by the enormous
amount of extracellular virulence and cell-associated factors furthermore it consider as an opportunistic
pathogen capable of infecting virtually all tissues[1]. At the beginning Ps. aeruginosa infections colonize on the
altered epithelium. Adherence on epithelium was intervened by many factors like pili, fimbriae and flagella.
Production of numerous extracellular virulence factors occurred after colonization and these factors blamable
for dissemination, invasion bloodstream, and wide-ranging tissue damaging [2].
From these virulence factors there are many important toxins and enzymes like exotoxin A,
exoenzyme S, sialidase and elastase which are compactly controlled by cell signaling systems [3]. Exotoxin A
and exoenzyme S which secreted by a type III section system was repressed by Protein biosynthesis [4]. Las B
(zinc metalloprotease) has activity as an elastolytic on lung tissue. Sialidase which responsible for adherence to
the respiratory tract encoded by nan1 gene [5].
Guiding systems prepare Pseudomonas to manufacture their virulence elements in a coordinated, cell
mass reliant on style that can permit Ps. Aeruginosa to beat the mechanisms of host defense. Intervention
through all these virulence elements assembly in need the system in these cells called cell signaling which is an
auspicious therapeutic methodology to reducing the percentage of mortality and morbidity that triggered by
Ps. Aeruginosa [6, 7].
Colonization with mucoid P. aeruginosa on pulmonary tract was a main cause of infection cases in
patients with cystic fibrosis [8]. Ps. Aeruginosa infections mainly distress in many patients with chronic
illnesses, catheterization and burn in addition to many other infections [9]. Fast recognition of isolates of
causative agents is actually essential for subsequent treatment choice for patients. Polymerase Chain Reaction
“PCR” was essential for recognizing etiological genus quickly by magnification the unique series of nucleotide
(sequence) to a specific being [10]. Lipoproteins“I, L” are external proteins forming membrane of Ps.
Aeruginosa which is blamable for resistance of Pseudomonas to antibiotics. Because of these proteins are
originate merely in this bacteria, it can be useful and dependable aspect for fast identification of P. Aeruginosa
[11, 12].
The aim of our study was to estimate prospective relations concerning the incidence all alleged genes
which correlated and vital for virulence mechanism and the consequence of toxicities affected by bacteria in
addition to that it was attempt to distinguish the molecular indications of virulence for Ps. aeruginosa strains
that isolated from different medicalorigins [7].
METHODS
P. aeruginosaisolate and identification
Strains of Ps. aeruginosa(n = 286) were gathered in time between April 2014 and April 2015 at the
medical Laboratory, private clinic laboratory and burning wards at Educational Hospital at Babil province then
transport specimens for cultivating and identification. Totally isolates were confirmed cultural procedures in
addition to detect soluble virulence factors produced by Ps. aeruginosa strains like; Hemolysins, DNase
Lecithinase , Amylase and Lipase and then using vitek 2 compact for microbiological revealing (BioMérieux,
France) which circling more than 30 biochemical tests using fluorescent technique, containing manytests
basically depending on enzymatic reaction for oxidases and amino peptidases. The source of the isolates was
from different systemic infection sites of clinically ill patients of mentioned Hospital. All these strains were
analyzed for virulence gene content and for the correlation of certain genes or gene combinations with known
chromosomal genes.
Preparation of Plasmid DNA
DNA (Plasmid) disjointed and isolated using standard distinct previously [13]. Plasmid profiling were
built by combination of many strains which having the similar molecular and quantity of a profile organizing a
main profile.
ISSN: 0975-8585
January–February 2016 RJPBCS 7(1) Page No. 592
DNA extraction
A total of 286 isolates of Ps. aeruginosa that cultivate aerobically in brain heart broth and incubated
for 18–24 hour at 37°C and 1200 rpm in a shaker incubator, the bacterial DNA extracted using commercial DNA
extraction kit it was performed using Invitrogen DNA extraction kit (USA) and then the genomic DNA was
conserved at -80°C in deep freezer.
Curing of Plasmid
By using technique for curing of the resistant plasmids from medical isolates belong to Ps. aeruginosa
we acquisition the pure and highly quantitative / qualitative plasmid [14]. The extraction of plasmid done by
using Gene aid Kit and follow the manufacture procedure.
Virulence Genes Detection
Several structural and virulence genes of Ps. aeruginosa including (plcH, algD, rhlI, exoS, exoU, lasR,
toxA, aprA, rhlAB, fliC, lecA, toxR, lasI, oprI, oprL, rhlR, nan1, lasB)were amplified using the PCR technique by
expending precise primers designed by using Primer3Plus, PCR condition and sequencing of each primer pair
was showed in Table 1.
Table 1: Pseudomonas Aeruginosa Primers set of virulence genes used in this study
Gene
Forward
Reverse
Tm
bp.
lasI
5’ CGTGCTCAAGTGTTCAAGG 3’
5’ TACAGTCGGAAAAGCCCAG 3’
66
295
lasR
5’ AAGTGGAAAATTGGAGTGGAG 3’
5’ GTAGTTGCCGACGACGATGAAG 3’
66
130
rhlI
5’ TTCATCCTCCTTTAGTCTTCCC 3’
5’ TTCCAGCGATTCAGAGAGC 3’
60
155
rhlR
5’ TCAGGGCGCACGAGAGCAACGAGA 3’
5’ CACTTCCTTTTCCAGGACG 3’
59
133
toxA
5’ GGAGCGCAACTATCCCACT 3’
5’ GACAGCCGCGCCGCCAGGTAGAGG 3’
66
454
aprA
5’ GTCGACCAGGCGGCGGAGCAGATA 3’
5’ GCCGAGGCCGCCGTAGAGGATGTC 3’
62
994
rhlAB
5’ TCATGGAATTGTCACAACCGC 3’
5’ ATACGGCAAAATCATGGCAAC 3’
61
151
plcH
5’ GAAGCCATGGGCTACTTCAA 3’
5’ AGAGTGACGAGGAGCGGTAG 3’
66
307
lasB
5’ TTCTACCCGAAGGACTGATAC 3’
5’ AACACCCATGATCGCAAC 3’
65
153
fliC
5’ GGCAGCTGGTTNGCCTG 3’
5’ GGCCTGCAGATCNCCAA 3’
60
1025
lecA
5’CGATGTCATTACCATCGTCG3’
5’TGATTGCACCCTGGACATTA3’
65
215
algD
5’AGGGCAACTGGACGGCTATC3’
5’TGTGGTCGGCAATGAAGAAGA3’
63
437
toxR
5’ATGGCATCTATGCGAGGAAC3’
5’GCAGGGGAATGAAGTTCTTG3’
65
207
oprI
5’ATGAACAACGTTCTGAAATTCTCTGCT3’
5’ CTTGCGGCTGGCTTTTTCCAG3’
57
249
oprL
5’ATGGAAATGCTGAAATTCGGC3’
5’ CTTCTTCAGCTCGACGCGACG3’
57
504
nan1
5’AGGATGAATACTTATTTTGAT3’
5’ TCACTAAATCCATCTCTGACCCGATA3’
55
1316
exoS
5’ CTTGAAGGGACTCGACAAGG3’
5’TTCAGGTCCGCGTAGTGAAT3’
54
504
exoU
5’GGG AAT ACT TTC CGG GAA GTT3’
5’CGA TCT CGC TGC TAA TGT GTT3’
60
428
Set up of PCR mixture reaction
The PCR was performed in 20μl reaction mixtures inclosing DNA template (bacterial DNA) of 1.2μl, 1μl
of 25 mM MgCl2, 5μl of 5x reaction buffer, 0.5 μl concentration of each (dNTP) deoxynucleotide triphosphate,
1.5μl of each forward primer and reverse primer and 0.15μl DNA polymerase along with its amplification
buffer. Gene magnifications done using convention Veriti gradient thermal cycler from applied biosystems
(USA).
Antibiogram Test
Disk diffusion (Kirby-Bauer method) achieved to determine bacterial susceptibility and sensitivity.
Antibiotics tested were tested against Ps. aeruginosa Amikacin, Amoxicillin, Amoxicillin + Clavulanic acid,
Azithromycin, , B \Bacitracin, Carbenicillin, Cefodizime, Cefoxitin, Ceftizoxime, Cephalexin, Chloromphenicol,
Clarithromycin, Clindamycin, Erythromycin, Gentamycin, Kanamycin, Lincomycin, Methicillin, Nitrofurantoin,
Norfloxacin, Ofloxacin, Oxacillin, Oxytetracyclin, Penicillin G, Piperacillin, Rifampim. Results were recited in
agreement with Clinical and Laboratory Standards Institute (CLSI, 2009). Results was revealed in figure 3.
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RESULTS AND DISSCUSION
Amplification of bacterial genome done by using adequate assays by PCR technique toreveal Ps.
aeruginosa virulence genes, it was many and that associated with their pathogenicity. Some of virulence
factors assistance bacterial establishment and colonization on the surface of the host, while others expedite
invasion numerous tissue. Many factors influence bacterial colonization such as flagella, fimbriae,
polysaccharides surface and type IV pili all these elements considered essential for attachment mechanism. Ps.
Aeruginosa have the ability to invade tissues with assistance toxins and enzymes that disruption fleshly
barriers by disturbing membranes of the cells and defeating the host, besides the fighting against phagocytosis
and immune shield of the host.
The invasion by Ps. aeruginosa is endorsed by manufacture many virulence proteins like; leucocidin,
hemolysins and proteases. Ps. aeruginosa have the ability to produce numerous proteases like alkaline
protease LasB and protease IV LasA which caused complement system disruption in addition to degradation of
surfactant [15].
Innate immunity can be disrupted by Ps. aeruginosa proteins through inactivation TNF and cleavage
antibodies [15]. Elastin was the major component of lung tissue which in charge for lung enlargement and
reduction and lying blood vessels, which play a role in their elasticity. The concentrated action of protease
(LasB and LasA) is accountable for many pathogenic activity such as demolition of elastin and elastolytic action
on human [16].
virulence genes frequency that code for Transcriptional regulator (lasR), Exotoxin A (toxA), elastase
(lasB), alkaline metalloproteinase (aprA), Transcriptional regulator (rhlR), rhamnolipid (rhlAB), LecA protein,
auto inducer synthesis protein (rhlI), alginate (algD), hemolytic phospholipase C (plcH), flagellar filament
structural protein (fliC), auto inducer synthesis protein (lasI), , transcriptional regulator (toxR), outer
membrane lipoprotein (oprI), peptidoglycan-associated lipoprotein (oprL), exoenzyme S (exoS) was
resoluteusing PCR technique.
Pseudomonas aeruginosa possess a number of genes as virulence elements which used it for
attachment, colonization, terminate, and extent through host organs and tissue. This study confirmed that all
studied Ps. aeruginosa strains have numerous virulence elements, several of these elements which are
terminated, accountable for the many medical cases and accelerate processes of infection which induced
through infectious mediators. Ps. aeruginosa own genes that have the ability for encoding: plcH, algD, rhlI,
exoS, exoU, lasR, toxA, aprA, rhlAB, fliC, lecA, toxR, lasI, oprI, oprL, rhlR, nan1, lasB.
Virulence genes prevalence among P. aeruginosa isolates (n=286) were as follows: lasI3.5%, lasR2.0%,
rhlI, 2.4%, rhlR 4.3%, toxA9.9%, aprA2.1%, rhlAB2.6%, plcH10.5%, lasB10.6%, fliC2.5%, lecA4.7%, algR10.4%,
toxR4.7%, oprI6.4%, oprL7.5%, nan12.0%, exoS9.4%, exoU4.5% as showed in figure 2.
Blood infections revealed the highest ratio in virulence genes from all infection 24 (20.9 %), followed
Burn infections 86 (17.4%), UTI 92 (16.6%), Wound 33 (15.5%), LRTI 16 and URTI 35 (15%) as showed in figure
1.
ISSN: 0975-8585
January–February 2016 RJPBCS 7(1) Page No. 594
Pathogenicity of bacteria can be induced by the existence of several virulence elements which
encoded through sets of genes existent on pathogenicity islands inside bacterial chromosome following
cooperate various mixtures [17, 18, 19]. Our study display that entirely virulence genes existing in all isolates
and custom part of genome of P. aeruginosa. That results agreed with other studies which proposed that the
virulence genes sheltered in all strains of Pseudomonas individually from the positions of clinical sample [20,
21].
The prevalence of extracellular genes that responsible for encoding many virulence elements like lasB
(elastase), aprA (alkaline protease), TCF (protease IV) and many other genes could be revealed using PCR
technique as golden standard also other soluble proteins complicated in invasion factor of Ps. aeruginosa are
characterized by phospholipases C and rhamno lipid additionally to other virulence elements. All these factors
could turn together to interruption tissue components like; phospholipids, in addition associate invasion using
their effects (cytotoxic) on WBC especially on lymphocytes, neutrophils and other cells[22].The percentage of
P. aeruginosa isolates producing the virulence factors from different clinical sources was showed in figure 4.
Many of these proteins which play as virulence factors play essential role in host immunity. For
example, Protease consider as essential virulence element in P. Aeruginosa pathogenesis because their role in
prompted bacterial keratitis [23]. Protease IV virulence role in pathogenicity was recognized by their role in
host proteins destruction, moreover destroys of structural proteins helping microbial attachment then causing
infection. Also Elastin is a main component of many essential organs in human like blood vessels and lung
which in control for lung expansion and contraction and resilience vessels. The intensive action of LasB and
LasA protease is elastolytic activity which associated destruction of elastin in tissue and the when invasive by
Ps. aeruginosa. Elastase like Zinc metallo protease (LasB) that related to gene operon of lasB, which
responsible of many disturbance effects like collagen, elastin and fibrin breakdown [24].
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January–February 2016 RJPBCS 7(1) Page No. 595
The anibiograms study of P. Aeruginosa strains from different clinical origins is revealed in figure 3.
Selected strains of P. Aeruginosa bared sensitivity to Erythromycin, Amikacin and Penicillin where as presented
resistance to Ofloxacin, Kanamycin, Penicillin, Clindamycin, Rifampim, Lincomycin, Oxytetracyclin G,
Carbenicillin, Piperacillin, erythromycin, Ceftizoxime, Oxacillin, Nitrofurantoin, Norfloxacin, Amoxicillin,
Cephalexin, Methicillin, Chloromphenicol, Amoxicillin/Clavulanic acid, Azithromycin, Norfloxacin, Bacitracin,
Cefodizime, Cefoxitin, Clarithromycin and Gentamycin.
Figures from A – Ewas Ethidium bromide-stained Agarose Gel Electrophoresis of PCR-amplified products from
extracted (1.5%) patterns showing typical PCR amplification products in multiplex PCRs for all figures including
plcH, algD, rhlI, exoS, exoU, lasR, toxA, aprA, rhlAB, fliC, lecA, toxR, lasI, oprI, oprL, rhlR, nan1andlasB genes.
Lane L, was DNA ladder (bioneer 25/100 Mixed DNA ladder and 100 DNA ladder)
Figure A: showed exoU gene (428 bp.) and lasI gene (295 bp.) at the right side of Ladder and in the left side
of Ladder it was fliC gene (1025 bp.) and oprL gene (504 bp.) with 100 DNA ladder.
A
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Figure B: showed aprA gene (994 bp.) and oprL gene (249 bp.) at the right side of Ladder and in the left side
of Ladder it was nan1 gene (1316 bp.) and exoS gene (504 bp.) with 100 DNA ladder.
Figure C: showed rhlAB gene (151 bp.) and rhlR gene (133 bp.) at the right side of Ladder and in the left side
of Ladder it was rhlI gene (155 bp.) and lsaR gene (130 bp.) with 100 DNA ladder.
B
C
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January–February 2016 RJPBCS 7(1) Page No. 597
Figure D: showed toxA gene (454 bp.) and lecA gene (215 bp) with with 100 DNA ladder.
Figure E: showed algD gene (437 bp.) and toxR gene (207 bp.) at the right side of Ladder and in the left side
of Ladder it was plcH gene (307 bp.) and lasB gene (153 bp.)with 25/100 Mixed DNA ladder.
Aggregate conflict to many antibiotics like fluroquinolone which occurs in several hospitals, that
realistic usage is both expelled and limited to get the emerging resistance under control [25, 26]. Resistance to
Cefodizime was described as 18%, in this study it was more than 90%. High standards of resistance which
detected comparable to other study that reports resistance value was 75% [27, 28, 29]. The improved
occurrence of resistant to ceftazidime is associated to the high use of antibiotics with beta lactam like
amoxicillin.
D
E
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