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A review on the origin of multidrug-resistant Salmonella and perspective of tailored phoP gene towards avirulence

Gangathraprabhu B, Kannan S, Santhanam G, Suryadevara N, Maruthamuthu M

Microb Pathog, 2020 Oct;147:104352.
PMID: 32592823 DOI: 10.1016/j.micpath.2020.104352

Salmonellosis continues to remain a health problem as the causative organism Salmonella spp. developed resistance to many of the antibiotics. As per World Health Organization (WHO), it is estimated that enteric fever, accounts for almost 16 million cases annually and over 600,000 deaths worldwide. Recent data revealed that the multi-drug resistance (MDR) rate of enteric fever was as high as 70% in Asian countries, as compared with the overall reported incidence of 50%. Emergence of MDR typhoid fever demands the use of newer antibiotics which also not offer promising effect in recent days. Effective antimicrobial therapy is required to control morbidity and prevent death from typhoid fever. The studies on PhoP/Q regulation revealed it as a best-characterized transcriptional regulation; a two-component system required for Salmonella pathogenesis which controls the expression of more than 40 genes. The PhoP DNA binding proteins possess positively charged amino acids such as arginine, lysine and histidine which present in the DNA binding site. Prevention of PhoP binding in phoP box may ultimately prevent the expression of many regulatory mechanism which plays vital role in Salmonella virulence. Deepness study of PhoP protein and various mutation swots may offer effectual controlling of MDR Salmonella.

Matched MeSH terms: Virulence
Fulltext Development of loop-mediated isothermal amplification (LAMP) for the detection of speB gene in invasive Streptococcus pyogenes clinical isolates

Azi Simon Onyema, Leslie Than Thian Lung, Suresh Kumar, Rukman Awang Hamat

Malaysian Journal of Medicine and Health Sciences, 2019;15(106):1-1.
MyJurnal

Introduction: Group A streptococcus (GAS) is responsible for high morbidity and mortality globally. Hence, the need to develop sensitive, reliable and cost- effective method of detection is crucial. In this study, we developed a visual detection method for the common virulence gene, streptococcal pyrogenic exotoxin B (speB) involved in invasive GAS diseases using loop-mediated isothermal amplification (LAMP) with fluorescent detection dye (calcein). Meth-ods: The LAMP reaction was optimized at 63°C for 35 minutes using five sets of primer designed with LAMP primer V5 software. When the dye was added prior to amplification, samples with speB DNA developed a characteristic green color after the reaction, but no color reactions were observed in samples with DNAs of non-GAS isolates. De-tection of speB by LAMP assay was done among 43 clinical isolates of blood, pus, wound, tissue and throat samples and ATCCs for controls. Our findings were further reconfirmed by subjecting the LAMP products to 0.5% gel electro-phoresis. Results: The detection limit of this LAMP assay for speB was 10-7 ng/μl of genomic DNA per reaction, which was 10,000-fold more sensitive than conventional PCR 10-3 ng/μl. All 100 % samples were positive for speB gene by LAMP, and 93% by conventional PCR method. Conclusion: LAMP assay could offer remarkably high sensitivity, specificity, repeatability, reliability, affordability, and visibility; it is appropriate for rapid detection of speB in Group A streptococci (GAS) as a point of care testing.

Matched MeSH terms: Virulence
Pathogenicity of Mycoplasma imitans in mixed infection with infectious bronchitis virus in chickens

Ganapathy K, Bradbury JM

Avian Pathol, 1999 Jun;28(3):229-37.
PMID: 26915378 DOI: 10.1080/03079459994713

Mycoplasma imitans (Mim) has been isolated from ducks, geese and partridges, and is closely related to Mycoplasma gallisepticum (Mg). The pathogenicity of Mim for chicks was investigated in single and mixed infections with infectious bronchitis virus (IBV) by giving IBV strain M41 at 1-day-old and Mim 2 days later. Single infections with IBV or Mim were also performed. No clinical signs or gross lesions were seen in chicks infected with Mim or uninfected control chicks, but they were seen in the other two groups. Clinical scores were consistently higher in birds with mixed infections than those infected with IBV alone, and were significantly higher (P < 0.05) between days 7 and 14. More birds developed sinusitis, tracheitis and airsacculitis (with greater severity) in the mixed than the single IBV infections. Mim was recovered more frequently and in greater numbers from the respiratory tract of birds with mixed than single infections. It was recovered from the lower trachea, air sacs and lungs only in mixed infections. Seroconversion to Mim occurred by day 14 in mixed infections, but not until day 21 in single infections. It appears that Mim can act synergistically with IBV in young chickens in a similar manner to Mg, although Mg may act as a primary pathogen under some circumstances.

Matched MeSH terms: Virulence
Fulltext Using Population and Comparative Genomics to Understand the Genetic Basis of Effector-Driven Fungal Pathogen Evolution

Plissonneau C, Benevenuto J, Mohd-Assaad N, Fouché S, Hartmann FE, Croll D

Front Plant Sci, 2017;8:119.
PMID: 28217138 DOI: 10.3389/fpls.2017.00119

Epidemics caused by fungal plant pathogens pose a major threat to agro-ecosystems and impact global food security. High-throughput sequencing enabled major advances in understanding how pathogens cause disease on crops. Hundreds of fungal genomes are now available and analyzing these genomes highlighted the key role of effector genes in disease. Effectors are small secreted proteins that enhance infection by manipulating host metabolism. Fungal genomes carry 100s of putative effector genes, but the lack of homology among effector genes, even for closely related species, challenges evolutionary and functional analyses. Furthermore, effector genes are often found in rapidly evolving chromosome compartments which are difficult to assemble. We review how population and comparative genomics toolsets can be combined to address these challenges. We highlight studies that associated genome-scale polymorphisms with pathogen lifestyles and adaptation to different environments. We show how genome-wide association studies can be used to identify effectors and other pathogenicity-related genes underlying rapid adaptation. We also discuss how the compartmentalization of fungal genomes into core and accessory regions shapes the evolution of effector genes. We argue that an understanding of genome evolution provides important insight into the trajectory of host-pathogen co-evolution.

Matched MeSH terms: Virulence
Fulltext Pseudomonas Aeruginosa and Streptococcus Pyogenes Exposed to Malaysian Trigona Honey In Vitro Demonstrated Downregulation of Virulence Factor

A Al-Kafaween M, Mohd Hilmi AB, A Nagi Al-Jamal H, A Elsahoryi N, Jaffar N, Khairi Zahri M

Iran J Biotechnol, 2020 Oct;18(4):e2542.
PMID: 34056021 DOI: 10.30498/IJB.2020.2542

Background: Honey has been known as a traditional medicine for centuries with its antibacterial properties. It is considered one of the most enduring substances used in wound management.
Objectives: This study aimed to: (i) evaluate the effects of Malaysian Trigona honey on bacterial structure and (ii) assess the anti-virulence potential of this honey by examining their impacts on the expression of selected genes (involved in stress survival and biofilm formation) in a test organism.
Materials and Methods: Trigona honey's impacts on the bacterial structure (cell morphology) and the expression profiles of select Pseudomonas Aeruginosa and Streptococcus Pyogenes genes were examined using scanning electron microscopy (SEM) and real-time PCR (RT-qPCR) analysis, respectively.
Results: SEM showed that the decreased cell density deformed, disrupted, and damaged cells for both bacteria. RT-qPCR showed that the expression of fleN, fleQ, and fleR genes of P.aeruginosa were decreased, 4.26-fold, 3.80-fold and 2.66- fold respectively. In addition, scpA, ftsY, and emm13 of S.pyogenes were decreased, 2.87-fold, 3.24-fold, and 4.65-fold respectively.
Conclusion: Our results indicate that Trigona honey may be an effective inhibitor and virulence modulator of P. aeruginosa and S. pyogenes via multiple molecular targets. This deduction needs to be investigated in vivo.

Matched MeSH terms: Virulence
Bacterial regulatory RNAs: complexity, function, and putative drug targeting

Cheah HL, Raabe CA, Lee LP, Rozhdestvensky TS, Citartan M, Ahmed SA, et al.

Crit Rev Biochem Mol Biol, 2018 08;53(4):335-355.
PMID: 29793351 DOI: 10.1080/10409238.2018.1473330

Over the past decade, RNA-deep sequencing has uncovered copious non-protein coding RNAs (npcRNAs) in bacteria. Many of them are key players in the regulation of gene expression, taking part in various regulatory circuits, such as metabolic responses to different environmental stresses, virulence, antibiotic resistance, and host-pathogen interactions. This has contributed to the high adaptability of bacteria to changing or even hostile environments. Their mechanisms include the regulation of transcriptional termination, modulation of translation, and alteration of messenger RNA (mRNA) stability, as well as protein sequestration. Here, the mechanisms of gene expression by regulatory bacterial npcRNAs are comprehensively reviewed and supplemented with well-characterized examples. This class of molecules and their mechanisms of action might be useful targets for the development of novel antibiotics.

Matched MeSH terms: Virulence
Prevalence of Fusarium Wilt Disease of Cucumber (Cucumis sativus Linn) in Peninsular Malaysia Caused by Fusarium oxysporum and F. solani

Din HM, Rashed O, Ahmad K

Trop Life Sci Res, 2020 Oct;31(3):29-45.
PMID: 33214854 DOI: 10.21315/tlsr2020.31.3.3

Fusarium wilt disease is one of the most problematic and destructive disease in cucumber production. The causative agents are Fusarium oxysporum and F. solani. These pathogens are soil borne and transmitted through infested soil and water. A field survey was conducted to study the disease prevalence in the major growing areas of cucumber in Peninsular Malaysia. Field study revealed that the disease was highly prevalence in the field with the disease incidence was in the range of 10%-60%. The morphological properties of F. oxysporum are microconidia (3.8-15.7 μm × 2.9-4.9 μm), macroconidia (14.8-38.5 μm × 2.4-5.7 μm) and number of septate was 1-4. While for F. solani are microconidia (3.39-14.63 μm × 2.36-4.44 μm), macroconidia (7.22-50.46 μm × 2.43-6.14 μm) and number of septate was 1-5. Based on molecular identification had confirmed that the disease is caused by F. oxysporum and F. solani with similarity index of 99%-100% based on internal transcribed spacer (ITS) gene sequences. The pathogenicity test showed that the symptoms of Fusarium wilt disease was firstly appeared as yellowing of old leaves. Progressively, the infected plant will be wilted and finally died. The outputs of this study are highly important to establish an effective disease management programme to reduce disease prevalence and yield loss in the field.

Matched MeSH terms: Virulence
Burkholderia pseudomallei pathogenesis and survival in different niches

Yip CH, Ghazali AK, Nathan S

Biochem Soc Trans, 2020 04 29;48(2):569-579.
PMID: 32167134 DOI: 10.1042/BST20190836

Burkholderia pseudomallei (Bp) is the causative agent of melioidosis, a disease of the tropics with high clinical mortality rates. To date, no vaccines are approved for melioidosis and current treatment relies on antibiotics. Conversely, common misdiagnosis and high pathogenicity of Bp hamper efforts to fight melioidosis. This bacterium can be isolated from a wide range of niches such as waterlogged fields, stagnant water bodies, salt water bodies and from human and animal clinical specimens. Although extensive studies have been undertaken to elucidate pathogenesis mechanisms of Bp, little is known about how a harmless soil bacterium adapts to different environmental conditions, in particular, the shift to a human host to become a highly virulent pathogen. The bacterium has a large genome encoding an armory of factors that assist the pathogen in surviving under stressful conditions and assuming its role as a deadly intracellular pathogen. This review presents an overview of what is currently known about how the pathogen adapts to different environments. With in-depth understanding of Bp adaptation and survival, more effective therapies for melioidosis can be developed by targeting related genes or proteins that play a major role in the bacteria's survival.

Matched MeSH terms: Virulence
Fulltext Detection of aerolysin and hemolysin genes in Aeromonas spp. isolated from environmental and shellfish sources by polymerase chain reaction

Yousr, A.H., Nipis, S., Rusul, G.R.A., Son, R.

International Food Research Journal, 2007;14(2):115-122.
MyJurnal

Polymerase chain reaction (PCR) technique was used to assay for the detection of specific genes in the genomes of the Aeromonas spp. isolated from environmental and shellfish sources, particularly aero and hlyA genes, responsible for aerolysin and hemolysin toxins production in this genus. The results showed that: (i) the 1500 bp amplicon of the hlyA gene was detected in 20/38 of the Aeromonas hydrophila, 13/38 of the A. caviae and 6/9 of the A. veronii biovar sobria isolates; (ii) the 690 bp amplicon of the aero gene was detected in 20/38 of A. hydrophila, 17/38 of A. caviae and 6/9 of A. veronii biovar sobria isolates; (iii) the nucleotide blast results of aerolysin gene sequences of the representative strains of A. hydrophila, A. caviae and A. veronii biovar sobria revealed a high homology of 94%, 95% and 95% with published sequences, respectively and ; (iv) the protein blast showed 97%, 94% and 96% homology when compared to the published sequences, respectively. The finding of A. hydrophila virulence genes in other members of the genus Aeromonas, may give a new perspective to the significance of these results. The method described here may be a useful detection tool to assist in further investigation of aero and hlyA genes in the genus Aeromonas, especially for food microbiologist.

Matched MeSH terms: Virulence
Fulltext Mitochondrial DNA Mutations in Grade II and III Glioma Cell Lines Are Associated with Significant Mitochondrial Dysfunction and Higher Oxidative Stress

Soon BH, Abdul Murad NA, Then SM, Abu Bakar A, Fadzil F, Thanabalan J, et al.

Front Physiol, 2017;8:231.
PMID: 28484394 DOI: 10.3389/fphys.2017.00231

The role of mitochondria in tumorigenesis has regained much attention as it could dysregulate cellular energetics, oxidative stress and apoptosis. However, the role of mitochondria in different grade gliomasis still unknown. This study aimed to identify mitochondrial DNA (mtDNA) sequence variations that could possibly affect the mitochondrial functions and also the oxidative stress status. Three different grades of human glioma cell lines and a normal human astrocyte cell line were cultured in-vitro and tested for oxidative stress biomarkers. Relative oxidative stress level, mitochondria activity, and mitochondrial mass were determined by live cell imaging with confocal laser scanning microscope using CM-H2DCFDA, MitoTracker Green, and MitoTracker Orange stains. The entire mitochondrial genome was sequenced using the AffymetrixGeneChip Human Mitochondrial Resequencing Array 2.0. The mitochondrial sequence variations were subjected to phylogenetic haplogroup assessment and pathogenicity of the mutations were predicted using pMUT and PolyPhen2. The Grade II astrocytoma cells showed increased oxidative stress wherea high level of 8-OHdG and oxidative stress indicator were observed. Simultaneously, Grade II and III glioma cells showed relatively poor mitochondria functions and increased number of mutations in the coding region of the mtDNA which could be due to high levels of oxidative stress in these cells. These non-synonymous mtDNA sequence variations were predicted to be pathogenic and could possibly lead to protein dysfunction, leading to oxidative phosphorylation (OXPHOS) impairment, mitochondria dysfunction and could create a vicious cycle of oxidative stress. The Grade IV cells had no missense mutation but preserved intact mitochondria and excellent antioxidant defense mechanisms thus ensuring better survival. In conclusion, Grade II and III glioma cells demonstrated coding region mtDNA mutations, leading to mitochondrial dysfunction and higher oxidative stress.

Matched MeSH terms: Virulence
Fulltext Physicochemical characterisation and substrate specificity of purified β-1,6-glucanase from Trichoderma Longibrachiatum

Muskhazli Mustafa, Nor Azwady Abd. Aziz, Anida Kaimi, Nurul Shafiza Noor, Salifah Hasanah Ahmad Bedawi, Nalisha Ithnin

Pertanika Journal of Science & Technology, 2009;17(1):-.
MyJurnal

The β-1,6-glucanases are ubiquitous enzymes which appear to be implicated in the morphogenesis and have the ability to become virulence factor in plant-fungal symbiotic interaction. To our knowledge, no report on ß-1,6-glucanases purification from Trichoderma longibrachiatum has been made, although it has been proven to have a significant effect as a biocontrol agent for several diseases. Therefore, the aim of this study was to purify β-1,6- glucanase from T. longibrachiatum T28, with an assessment on the physicochemical properties and substrate specificity. β-1,3-glucanase enzyme, from the culture filtrate of T. longibrachiatum T28, was successively purified through precipitation with 80% acetone, followed by anionexchange chromatography on Neobar AQ and chromatofocusing on a Mono P HR 5/20 column. (One β-1,6-glucanase) band at 42kDa in size was purified, as shown by the SDS-PAGE. The physicochemical evaluation showed an optimum pH of 5 and optimum temperature of 50°C for enzyme activity with an ability to maintain 100% enzyme stability. Enzyme activity was slightly reduced by 10-20% in the presence of 20 mM of Zn2+, Ca2+, Co2+, Mg2+, Cu2+, Mn2+ and Fe2+. The highest β-1,6-glucanase hydrolysis activity was obtained on pustulan due to the similarity of β-glucosidic bonds followed by laminarin, glucan and cellulose. Therefore, it can be concluded that the characterization of ß-1,6-glucanase secreted by T. longibrachiatum in term of molecular weight, responsed to selected physicochemical factors and the substrate specificity are approximately identical to other Trichoderma sp.

Matched MeSH terms: Virulence Factors
Fulltext Survivability of Acanthamoeba strains isolated from clinical and environmental specimens during axenization

Nurul Farhana Jufri, Anisah Nordin, Mohamed Kamel Abd Ghani, Yusof Suboh, Noraina Abd Rahim

Jurnal Sains Kesihatan Malaysia, 2011;9(1):1-3.
MyJurnal

Acanthamoeba is a free living protozoa that can cause keratitis and granulomatous amoebic encephalitis. Physiological characteristics of this amoeba are found to have a medical importance in which it can be related to the pathogenicity potential of the organism. This study was carried out to investigate the physiological characteristics of survivability during axenization. Six Acanthamoeba strains from three clinical isolates (HSB 1, HKL 48 and HKL 95) and three environmental isolates (PHS 2, PHS 11 and PHS 15) were used in this study. Axenization test was done by treating cysts with hydrochloric acid (3%) and Page saline containing Gentamicin (100 µg/ml). Cysts were then cultured into PYG enrich media, incubated at 30oC and the presence and proliferation of trophozoites of Acanthamoeba were observed. This study showed that PHS 15, HSB 1, HKL 48 and HKL 95 could be axenized but they have poor proliferation rate in PYG enrich media. The result showed that the difference between both clinical and environmental isolates was observed in two strains; PHS 2 and PHS 11. This indicates that there is a possibility that the physiological traits of strains from both isolates are the same and strains from the environment are able to show the pathogenic potential and capable of causing infection to human.

Matched MeSH terms: Virulence
Fulltext Ability of Acanthamoeba cyst to excyst at different temperatures

Nurul Fariza Rossle, Mohamed Kamel Abd Ghani, Anisah Nordin, Yusof Suboh, Noraina Ab Rahim

Jurnal Sains Kesihatan Malaysia, 2011;9(1):41-43.
MyJurnal

This study was carried out to observe thermotolerance ability of Acanthamoeba spp. A total of 32 Acanthamoeba spp. isolates obtained from water taps, sinks, swimming pools and sea water were used. Trophozoites of Acanthamoeba spp. were inoculated onto non-nutrient agar (NNA) seeded with heat-killed Escherichia coli using aseptic technique and incubated for 14 days at 30°C to obtain the cyst. The cysts were subcultured onto new agar plates for thermotolerance test at 37°C and 42°C. The plates were observed until 96 hours after incubation for excystation of Acanthamoeba before being declared negative. Overall, 81.25% of samples were able to excyst at 37°C while 37.5% were able to excyst at 42°C. Thermotolerant Acanthamoeba is associated with high pathogenicity potential.

Matched MeSH terms: Virulence
Fulltext Antibiotic susceptibility study of metal-gentamicin complexes against Staphylococcus Aureus Biofilms

Intan Azura Shahdan, Fatimah Zahrah Mohd Sobr, Mohammad Faiz Hizzuan Hanap, Hanani Ahmad Yusof, How, Fiona N.F.

International Medical Journal Malaysia, 2017;16(21):4-4.
MyJurnal

Dental plaque is a structurally and functionally organized biofilm. Modern molecular
biological techniques have identified about 1000 different bacterial species in the dental biofilm,
twice as many as can be cultured. Inherent resistance of biofilm bacteria to conventional
antibiotics is alarming. It induces antibiotic resistance to an order of three or more in magnitude
greater than those displayed by planktonic bacteria. Staphylococcus aureus is the most dominant
bacterial species isolated from the saliva and dental plaques. One of the reasons for its
pathogenicity is its ability to form biofilms. In this study, the resistance of S. aureus biofilms
against a eries of metal-antibiotics, an alternative to the conventional antibiotics, was
investigated. (Copied from article).

Matched MeSH terms: Virulence
Fulltext Distinct Biological Potential of Streptococcus gordonii and Streptococcus sanguinis Revealed by Comparative Genome Analysis

Zheng W, Tan MF, Old LA, Paterson IC, Jakubovics NS, Choo SW

Sci Rep, 2017 06 07;7(1):2949.
PMID: 28592797 DOI: 10.1038/s41598-017-02399-4

Streptococcus gordonii and Streptococcus sanguinis are pioneer colonizers of dental plaque and important agents of bacterial infective endocarditis (IE). To gain a greater understanding of these two closely related species, we performed comparative analyses on 14 new S. gordonii and 5 S. sanguinis strains using various bioinformatics approaches. We revealed S. gordonii and S. sanguinis harbor open pan-genomes and share generally high sequence homology and number of core genes including virulence genes. However, we observed subtle differences in genomic islands and prophages between the species. Comparative pathogenomics analysis identified S. sanguinis strains have genes encoding IgA proteases, mitogenic factor deoxyribonucleases, nickel/cobalt uptake and cobalamin biosynthesis. On the contrary, genomic islands of S. gordonii strains contain additional copies of comCDE quorum-sensing system components involved in genetic competence. Two distinct polysaccharide locus architectures were identified, one of which was exclusively present in S. gordonii strains. The first evidence of genes encoding the CylA and CylB system by the α-haemolytic S. gordonii is presented. This study provides new insights into the genetic distinctions between S. gordonii and S. sanguinis, which yields understanding of tooth surfaces colonization and contributions to dental plaque formation, as well as their potential roles in the pathogenesis of IE.

Matched MeSH terms: Virulence
Fulltext CsoR metalloregulatory protein: function, mechanism and relevance

Mangavelu, Ashwaani, Yahaya M. Normi, Leow, Adam Thean Chor, Mohd Shukuri Mohammad Ali, Raja Noor Zaliha Raja Abd. Rahman

The Pertanika Journal of Scholarly Research Reviews, 2017;3(1):24-31.
MyJurnal

Transition metals are required constituent in bacterial metabolism to assist in some enzymatic reactions. However, intracellular accumulations of these metal ions are harmful to the bacteria as it can trigger unnecessary redox reactions. To overcome this condition, metalloregulatory proteins assist organisms to adapt to sudden elevated and deprived metal ion concentration in the environment via metal homeostasis. CsoR protein is a copper(I) [Cu(I)] sensing operon repressor that is found to be present in all major classes of eubacteria. This metalloregulatory protein binds to the operator region in its apo state under Cu(I) limiting condition and detaches off from the regulatory region when it binds to the excess cytosolic Cu(I) ion, thus derepressing the expression of genes involved in Cu(I) homeostasis. CsoR proteins exist in dimeric and tetrameric states and form certain coordination geometries upon attachment with Cu(I). Certain CsoR proteins have also been found to possess the ability to bind to other types of metals with various binding affinities in some Gram positive bacteria. The role of this metalloregulatory protein in host pathogen interaction and its relation to bacterial virulence are also discussed.

Matched MeSH terms: Virulence
Diversity of fusarium species associated with post-harvest fruit rot disease of tomato

Abu Bakar A, Nur Ain Izzati M, Umi Kalsom Y

Sains Malaysiana, 2013;42:911-920.

Fusarium species is one of the common pathogens of post-harvest disease to cause rot on tomato and other perishable vegetable fruits. The objectives of this study were to determine the diversity of Fusarium isolated species from post-harvest diseases of tomato fruit, to identify the causal organisms by using phenotype characteristics and to verify the pathogens of Fusarium fruit of tomato based on pathogenicity test. Carnation leaf-piece agar (CLA) and potato dextrose agar (PDA) media were used for phenotype-based identification of the Fusarium isolates with emphasis for characterizations of the shapes and sizes of the macroconidia and microconidia, colony features, growth rates, conidiogenous cells and chlamydospores. A total of 180 Fusarium isolates were obtained from 13 locations throughout Selangor. Fusarium solani was most abundantly isolated (34%) followed by F. semitectum (31%) and F. oxysporum (31%), F. subglutinans (3%) while the least was F. equiseti (1%). Twenty seven isolates were tested for pathogenicity test by injecting 1 mL of the conidial suspension onto healthy tomatoes. All the tested Fusarium isolates were pathogenic on tomato with different severity levels. The non-inoculated controls showed no symptoms of fruit rot. The most virulent was F. oxysporum isolate B711T with DSI 93.75%, while the least were isolates of F. solani (B647T) and F. oxysporum (B727T) with DSI 37.5%. Majority of the isolated Fusarium species can potentially produce mycotoxins as their secondary metabolites. The potential production of mycotoxins by pathogenic isolates of Fusarium species in contaminated tomato fruits could pose health hazards when consumed.

Matched MeSH terms: Virulence
Incidence of escherichia coli O157:H7 in Thailand

Pharanai Sukhumungoon

Sains Malaysiana, 2015;44:261-267.

Enterohemorrhagic Escherichia coli (EHEC) especially serotype O157:H7 is one of the important food-borne pathogens because it is able to produce crucial toxins Shiga. However, the outbreak of this organism in Thailand has not been reported. Antibody to O157 antigen was detected in some Thai populations and Shiga toxin-producing E. coli were detected in low numbers of clinical specimens. Interestingly, some E. coli that showed positive to O157 fimbriae probe and lack of virulence gene were isolated from certain patients and one isolate of E. coli O157:H7 which possessed stx1, stx2v was detected in a normal child. In addition, the incidence of E. coli O157:H7 strains were monitored by the samples from cattle and retail beef in Thailand although their inability to produce toxins or produce in a low concentration was demonstrated. This review discusses the incidences of E. coli O157 in clinical and environmental samples of Thailand including the transmission possibility of this bacterium across the Thai border through food trade.

Matched MeSH terms: Virulence
First Report of Rubber Tree Stem Rot Caused by Fusarium oxysporum in China

Li BX, Shi T, Liu XB, Lin CH, Huang GX

Plant Dis, 2014 Jul;98(7):1008.
PMID: 30708897 DOI: 10.1094/PDIS-01-14-0004-PDN

Rubber tree (Hevea brasiliensis) is an important crop in tropical regions of China. In October 2013, a new stem rot disease was found on cv. Yunyan77-4 at a rubber tree plantation in Hekou, Yunnan Province. There were about 100 plants, and diseased rubber trees accounted for 30% or less. Initially, brown-punctuate secretion appeared on the stem, which was 5 to 6 cm above the ground. Eventually, the secretion became black and no latex produced from the rubber tree bark. After removing the secretion, the diseased bark was brown putrescence, but the circumambient bark was normal. Upon peeling the surface bark, the inner bark and xylem had brown rot and was musty. The junction between health and disease was undulate. On the two most serious plants, parts of leaves on the crown were yellow, and the root near the diseased stem was dry and puce. The pathogen was isolated and designated HbFO01; the pathogenicity was established by following Koch's postulates. The pathogen was cultivated on a potato dextrose agar (PDA) plate at 28°C for 4 days. Ten plants of rubber tree cv. Yunyan77-4 were selected from a disease-free plantation in Haikou, Hainan Province, and the stem diameter was about 7 cm. The bark of five plants was peeled, and one mycelium disk with a diameter of 1 cm was inserted into the cut and covered again with the bark. The other five plants were treated with agar disks as controls. The inoculation site was kept moist for 2 days, and then the mycelium and agar disk were removed. On eighth day, symptoms similar to the original stem lesions were observed on stems of inoculated plants, while only scars formed on stems of control plants. The pathogen was re-isolated from the lesions of inoculated plants. On PDA plates, the pathogen colony was circular and white with tidy edges and rich aerial hyphae. Microscopic examination showed microconidia and chlamydospores were produced abundantly on PDA medium. The falciform macroconidia were only produced on lesions and were slightly curved, with a curved apical cell and foot shaped to pointed basal cell, usually 3-septate, 16.2 to 24.2 × 3.2 to 4.0 μm. Microconidia were produced in false heads, oval, 0-septate, 6.2 to 8.2 × 3.3 to 3.8 μm, and the phialide was cylindrical. Chlamydospores were oval, 6.4 to 7.2 × 3.1 to 3.8 μm, alone produced in hypha. Morphological characteristics of the specimen were similar to the descriptions for Fusarium oxysporum (2). Genomic DNA of this isolate was extracted with a CTAB protocol (4) from mycelium and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA with primer pair ITS1/ITS4 (1). The full length of this sequence is 503 nt (GenBank Accession No. KJ009335), which exactly matched several sequences (e.g., JF807394.1, JX897002.1, and HQ451888.1) of F. oxysporum. Williams and Liu had listed F. oxysporum as the economically important pathogen of Hevea in Asia (3), while this is, to our knowledge, the first report of stem rot caused by F. oxysporum on rubber tree in China. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual, 2006. (3) T. H. Williams and P. S. W. Liu. A host list of plant diseases in Sabah, Malaysia, 1976. (4) J. R. Xu et al. Genetics 143:175, 1996.

Matched MeSH terms: Virulence
First Report of Anthracnose Disease on Young Stems of Bawanghua (Hylocereus undatus) Caused by Colletotrichum gloeosporioides in China

Ma WJ, Yang X, Wang XR, Zeng YS, Liao MD, Chen CJ, et al.

Plant Dis, 2014 Jul;98(7):991.
PMID: 30708879 DOI: 10.1094/PDIS-06-13-0609-PDN

Hylocereus undatus widely grows in southern China. Some varieties are planted for their fruits, known as dragon fruits or Pitaya, while some varieties for their flowers known as Bawanghua. Fresh or dried flowers of Bawanghua are used as routine Chinese medicinal food. Since 2008, a serious anthracnose disease has led to great losses on Bawanghua flower production farms in the Baiyun district of Guangzhou city in China. Anthracnose symptoms on young stems of Bawanghua are reddish-brown, sunken lesions with pink masses of spores in the center. The lesions expand rapidly in the field or in storage, and may coalesce in the warm and wet environment in spring and summer in Guangzhou. Fewer flowers develop on infected stems than on healthy ones. The fungus overwinters in infected debris in the soil. The disease caused a loss of up to 50% on Bawanghua. Putative pathogenic fungi with whitish-orange colonies were isolated from a small piece of tissue (3 × 3 mm) cut from a lesion margin and cultured on potato dextrose agar in a growth chamber at 25°C, 80% RH. Dark colonies with acervuli bearing pinkish conidial masses formed 14 days later. Single celled conidia were 11 to 18 × 4 to 6 μm. Based on these morphological characteristics, the fungi were identified as Colletotrichum gloeosporioides (Penz.) Penz. & Sacc (2). To confirm this, DNA was extracted from isolate BWH1 and multilocus analyses were completed with DNA sequence data generated from partial ITS region of nrDNA, actin (ACT) and glutamine synthetase (GS) nucleotide sequences by PCR, with C. gloeosporioides specific primers as ITS4 (5'-TCCTCCGCTTATTGATATGC-3') / CgInt (5'-GGCCTCCCGCCTCCGGGCGG-3'), GS-F (5'-ATGGCCGAGTACATCTGG-3') / GS-R (5'-GAACCGTCGAAGTTCCAC-3') and actin-R (5'-ATGTGCAAGGCCGGTTTCGC-3') / actin-F (5'-TACGAGTCCTTCTGGCCCAT-3'). The sequence alignment results indicated that the obtained partial ITS sequence of 468 bp (GenBank Accession No. KF051997), actin sequence of 282 bp (KF712382), and GS sequence of 1,021 bp (KF719176) are 99%, 96%, and 95% identical to JQ676185.1 for partial ITS, FJ907430 for ACT, and FJ972589 for GS of C. gloeosporioides previously deposited, respectively. For testing its pathogenicity, 20 μl of conidia suspension (1 × 106 conidia/ml) using sterile distilled water (SDW) was inoculated into artificial wounds on six healthy young stems of Bawanghua using sterile fine-syringe needle. Meanwhile, 20 μl of SDW was inoculated on six healthy stems as a control. The inoculated stems were kept at 25°C, about 90% relative humidity. Three independent experiments were carried out. Reddish-brown lesions formed after 10 days, on 100% stems (18 in total) inoculated by C. gloeosporioides, while no lesion formed on any control. The pathogen was successfully re-isolated from the inoculated stem lesions on Bawanghua. Thus, Koch's postulates were fulfilled. Colletotrichum anthracnose has been reported on Pitaya in Japan (3), Malaysia (1) and in Brazil (4). To our knowledge, this is the first report of anthracnose disease caused by C. gloeosporioides on young stems of Bawanghua (H. undatus) in China. References: (1) M. Masyahit et al. Am. J. Appl. Sci. 6:902, 2009. (2) B. C. Sutton. Page 402 in: Colletotrichum Biology, Pathology and Control. J. A. Bailey and M. J. Jeger, eds. CAB International, Wallingford, UK, 1992. (3) S. Taba et al. Jpn. J. Phytopathol. 72:25, 2006. (4) L. M. Takahashi et al. Australas. Plant Dis. Notes 3:96, 2008.

Matched MeSH terms: Virulence

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