Citrus bent leaf viroid (CBLVd) from genus Apscaviroid, is one of the widely distributed viroids among the seven citrus viroids. It is comprised of three variants: Citrus viroid-Ia (CVd-Ia) (327 - 329 nucleotides), Citrus viroid-Ib (CVd-Ib) (315 - 319 nucleotides) and Citrus viroid-I-low sequence similarity (CVd-I-LSS) (325 - 330 nucleotides). Virulence of CBLVd totally expressed on citrus plants. Etrog citron (Citrus medica (L.)) coinfected with CBLVd, Citrus exocortis viroid (CEVd), Citrus viroid-III (CVd-III) and Citrus viroid-V (CVd-V) showed epinasty, leaf rolling, and stunting. CBLVd has been reported to reduce the canopy proportion and fruit production of citrus trees inserted on trifoliate orange rootstock. Moreover, citrus tree infected with singly CBLVd or in combinations with CEVd, Hop stunt viroid (CVd-II) and CVd-III induced dwarfing have been associated with poor development of the root system. Reverse-transcriptase polymerase chain reaction (RT-PCR) amplification and multiplex reverse-transcriptase polymerase chain reaction (MRT-PCR) amplification have been widely used to detect citrus viroids including CBLVd. As citrus viroids are emerging threats in citrus groves, therefore, this review covers the evolution, geographical distribution and epidemiology, economic impact and symptomatology, host range and transmission, detection, and management will be helpful in formulating the integrated management strategies for CBLVd.
Background: Leptospirosis is a zoonotic disease that infects human and livestock which causes economic losses to the farmers. It has been reported as one of the causes of reproductive failure in cattle and other ruminants, determining abortions, stillbirth, weak newborns, and decrease in their growth rate and milk production.
Aim: The objectives of this study were to determine the leptospirosis seroprevalence and to identify the predominant infecting serovars among cattle.
Materials and Methods: A cross-sectional study involving 420 cattle from six randomly selected districts in Kelantan was conducted. A serological test using the microscopic agglutination test was conducted in the Institute of Medical Research with a cutoff titer for seropositivity of ≥1:100.
Results: The overall prevalence of leptospirosis seropositivity among cattle in this study was 81.7% (95% confidence interval: 63.5, 80.1). The most common reaction obtained with the sera tested was from the serovar Sarawak with 78.8%.
Conclusion: A high seroprevalence of leptospiral antibodies was found among cattle in Northeastern Malaysia. These findings urge that more studies are required to determine the reasons for the high seroprevalence among the cattle along with its transmission and pathogenicity of the local serovar Sarawak.
Multifunctionalities linked with the microbial communities associated with the millet crop rhizosphere has remained unexplored. In this study, we are analyzing microbial communities inhabiting rhizosphere of kodo millet and their associated functions and its impact over plant growth and survival. Metagenomics of Paspalum scrobiculatum L.(kodo millet) rhizopshere revealed taxonomic communities with functional capabilities linked to support growth and development of the plants under nutrient-deprived, semi-arid and dry biotic conditions. Among 65 taxonomically diverse phyla identified in the rhizobiome, Actinobacteria were the most abundant followed by the Proteobacteria. Functions identified for different genes/proteins led to revelations that multifunctional rhizobiome performs several metabolic functions including carbon fixation, nitrogen, phosphorus, sulfur, iron and aromatic compound metabolism, stress response, secondary metabolite synthesis and virulence, disease, and defense. Abundance of genes linked with N, P, S, Fe and aromatic compound metabolism and phytohormone synthesis-along with other prominent functions-clearly justifies growth, development, and survival of the plants under nutrient deprived dry environment conditions. The dominance of actinobacteria, the known antibiotic producing communities shows that the kodo rhizobiome possesses metabolic capabilities to defend themselves against biotic stresses. The study opens avenues to revisit multi-functionalities of the crop rhizosphere for establishing link between taxonomic abundance and targeted functions that help plant growth and development in stressed and nutrient deprived soil conditions. It further helps in understanding the role of rhizosphere microbiome in adaptation and survival of plants in harsh abiotic conditions.
Fowl adenovirus (FAdV) is the causative agent of inclusion body hepatitis (IBH) in chickens with significant economic losses due to high mortality and poor production. It was objectives of the study to attenuate and determine the molecular characteristic of FAdV isolate (UPM1137) of Malaysia passages in primary chicken embryo liver (CEL) cells. The cytopathic effect (CPE) was recorded and the present of the virus was detected by polymerase chain reaction (PCR). Nucleotide and amino acid changes were determined and a phylogenetic tree was constructed. The pathogenicity and immunogenicity of the virus at passage 35 (CEL35) with virus titre of 106.7TCID50/mL was determined in day old specific pathogen free (SPF) chicks via oral or subcutaneous route of inoculation. The study demonstrated that the FAdV isolate was successfully propagated and attenuated in CEL cells up to 35th consecutive passages (CEL35) with delayed of CPE formation within 48 to 72 post inoculation (pi) from CEL20 onwards. The virus caused typical CPE with basophilic intranuclear inclusion bodies, refractile and clumping of cells. The virus is belong to serotype 8b with substitution of amino acid at position 44, 133 and 185 in L1 loop of hexon gene and in knob of fiber gene at position 348 and 360 at CEL35. It is non-pathogenic, but immunogenic in SPF chickens. It was concluded that the FAdV isolate was successfully attenuated in CEL cells with molecular changes in major capsid proteins which affect its infectivity in cell culture and SPF chickens.
Dendrobium (Dendrobium candidum Wall. ex Lindl.) is a perennial herb in the Orchidaceae family. It has been used as traditional medicinal plant in China, Malaysia, Laos, and Thailand (2). Fungal disease is one of the most important factors affecting the development of Dendrobium production. During summer 2012, chocolate brown spots were observed on leaves of 2-year-old Dendrobium seedlings in a greenhouse in Hangzhou, Zhejiang Province, China, situated at 30.26°N and 120.19°E. Approximately 80% of the plants in each greenhouse were symptomatic. Diseased leaves exhibited irregular, chocolate brown, and necrotic lesions with a chlorotic halo, reaching 0.8 to 3.2 cm in diameter. Affected leaves began to senesce and withered in autumn, and all leaves of diseased plants fell off in the following spring. Symptomatic leaf tissues were cut into small pieces (4 to 5 mm long), surface-sterilized (immersed in 75% ethanol for 30 s, and then 1% sodium hypochlorite for 60 s), rinsed three times in sterilized distilled water, and then cultured on potato dextrose agar (PDA) amended with 30 mg/liter of kanamycin sulfate (dissolved in ddH2O). Petri plates were incubated in darkness at 25 ± 0.5°C, and a grey mycelium with a white border developed after 4 days. Fast-growing white mycelia were isolated from symptomatic leaf samples, and the mycelia became gray-brown with the onset of sporulation after 5 days. Conidia were unicellular, black, elliptical, and 11.4 to 14.3 μm (average 13.1 μm) in diameter. Based on these morphological and pathogenic characteristics, the isolates were tentatively identified as Nigrospora oryzae (1). Genomic DNA was extracted from a representative isolate F12-F, and a ~600-bp fragment was amplified and sequenced using the primers ITS1 and ITS4 (4). BLAST analysis showed that F12-F ITS sequence (Accession No. KF516962) had 99% similarity with the ITS sequence of an N. oryzae isolate (JQ863242.1). Healthy Dendrobium seedlings (4 months old) were used in pathogenicity tests under greenhouse conditions. Leaves were inoculated with mycelial plugs (5 mm in diameter) from a 5-day-old culture of strain F12-F, and sterile PDA plugs served as controls. Seedlings were covered with plastic bags for 5 days and maintained at 25 ± 0.5°C and 80 ± 5% relative humidity. Eight seedlings were used in each experiment, which was repeated three times. After 5 days, typical chocolate brown spots and black lesions were observed on inoculated leaves, whereas no symptoms developed on controls, which fulfilled Koch's postulates. This shows that N. oryzae can cause leaf spot of D. candidum. N. oryzae is a known pathogen for several hosts but has not been previously reported on any species of Dendrobium in China (3). To our knowledge, on the basis of literature, this is the first report of leaf spot of D. candidum caused by N. oryzae in China. References: (1) H. J. Hudson. Trans. Br. Mycol. Soc. 46:355, 1963. (2) Q. Jin et al. PLoS One. 8(4):e62352, 2013. (3) P. Sharma et al. J. Phytopathol. 161:439, 2013. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.
During March 2011 to June 2012, 50 banana plants of cultivar Musa × paradisiaca 'Horn' with Moko disease symptoms were randomly sampled in 12 different locations of 5 outbreak states in Peninsular Malaysia comprising Kedah, Selangor, Pahang, Negeri Sembilan, and Johor, with disease incidence exceeding 90% in some severely affected plantations. The disease symptoms observed in the infected plants included yellowing and wilting of the oldest leaves, which became necrotic, and eventually led to their dieback or collapse. The pulp of banana fruits also became discolored and exuded bacterial ooze. Vascular tissues in pseudostems were discolored. Fragments from symptomatic plant samples were excised and cultured on Kelman's-tetrazolium salt (TZC) medium. Twenty positive samples produced fluidal colonies that were either entirely white or white with pink centers after incubation for 24 to 48 h at 28°C on Kelman's-TZC medium and appeared as gram-negative rods after Gram staining. They were also positive for potassium hydroxide (KOH), Kovacs oxidase, and catalase tests, but negative for utilization of disaccharides and hexose alcohols, which are characteristics of biovar 1 Ralstonia solanacearum. For the pathogenicity test, 30 μl of 108 CFU/ml bacterial suspension of three selected virulent strains were injected into banana (Musa × paradisiaca 'Horn') leaves explants grown in plastic pots of 1,440 cm3 volume in a greenhouse, with temperature range from 26 to 35°C. Leaves that were infiltrated with sterile distilled water served as a negative control. Inoculations with all isolates were performed in three replications, as well as the uninoculated control leaves explants. The inoculated plants produced the same symptoms as observed on naturally diseased samples, whereas control plants remained asymptomatic. Strain cultures were re-isolated and possessed the morphological and biochemical characteristics as previously described. PCR amplification using race 2 R. solanacearum primers ISRso19-F (5'-TGGGAGAGGATGGCGGCTTT-3') and ISRso19-R (5'-TGACCCGCCTTTCGGTGTTT-3') (3) produced a 1,900-bp product from DNA of all bacterial strains. BLAST searches resulted that the sequences were 95 to 98% identical to published R. solanacearum strain race 2 insertion sequence ISRso19 (GenBank Accession No. AF450275). These genes were later deposited in GenBank (KC812051, KC812052, and KC812053). Phylotype-specific multiplex PCR (Pmx-PCR) and Musa-specific multiplex PCR (Mmx-PCR) were performed to identify the phylotype and sequevar of all isolates (4). Pmx-PCR showed that all isolates belonged to phylotype II, whereas Mmx-PCR showed that they belonged to phylotype II sequevar 4 displaying 351-bp amplicon. Although there were previously extensive studies on R. solanacearum associated with bacterial wilt disease of banana crops in Malaysia, none related to Moko disease has been reported (1,2). The result has a great importance to better understand and document R. solanacearum race 2 biovar 1, since banana has been identified as the second most important commercial fruit crop with a high economic value in Malaysia. References: (1) R. Khakvar et al. Plant Pathol. J. 7:162, 2008. (2) R. Khakvar et al. Am. J. Agri. Biol. Sci. 3:490, 2008. (3) Y. A. Lee and C. N. Khor. Plant Pathol. Bull. 12:57, 2003. (4) P. Prior et al. Pages 405-414 in: Bacterial Wilt Disease and the Ralstonia solanacearum Species Complex. The American Phytopathological Society, St. Paul, MN, 2005.
The link between quorum sensing in Vibrio campbellii and its virulence towards tiger grouper (Epinephelus fuscoguttatus) was investigated using V. campbellii wild type and quorum-sensing mutants with inactive quorum sensing or constitutively maximal quorum-sensing activity, and signal molecule synthase mutants. The results showed that wild-type V. campbellii is pathogenic to grouper larvae, causing more than 50% mortality after 4 days of challenge. Furthermore, the mortality of larvae challenged with the mutant with maximally active quorum sensing was significantly higher than that of larvae challenged with the wild type, whereas a higher survival was observed in the larvae challenged to the mutant with a completely inactive quorum-sensing system. Grouper larvae challenged with either the signal molecule synthase triple mutant, the harveyi autoinducer-1 (HAI-1) synthase mutant and the autoinducer-2 (AI-2) synthase mutant showed higher survival than larvae challenged with the wild type. In contrast, larvae challenged with the cholerae autoinducer-1 (CAI-1) synthase mutant showed high mortality. This indicates that HAI-1 and AI-2, but not CAI-1, are required for full virulence of V. campbellii towards grouper larvae. Our data suggest that quorum-sensing inhibition could be an effective strategy to control V. campbellii infections in tiger grouper.
In June 2011, tomatoes (Solanum lycopersicum) in major growing areas of the Cameron Highlands and the Johor state in Malaysia were affected by a leaf spot disease. Disease incidence exceeded 80% in some severely infected regions. Symptoms on 50 observed plants initially appeared on leaves as small, brownish black specks, which later became grayish brown, angular lesions surrounded by a yellow border. As the lesions matured, the affected leaves dried up and became brittle and later developed cracks in the center of the lesions. A survey was performed in these growing areas and 27 isolates of the pathogen were isolated from the tomato leaves on potato carrot agar (PCA). The isolates were purified by the single spore technique and were transferred onto PCA and V8 agar media for conidiophore and conidia production under alternating light (8 hours per day) and darkness (16 hours per day) (4). Colonies on PCA and V8 agar exhibited grey mycelium and numerous conidia were formed at the terminal end of conidiophores. The conidiophores were up to 240 μm long. Conidia were oblong with 2 to 11 transverse and 1 to 6 longitudinal septa and were 24 to 69.6 μm long × 9.6 to 14.4 μm wide. The pathogen was identified as Stemphylium solani on the basis of morphological criteria (2). In addition, DNA was extracted and the internal transcribed spacer region (ITS) was amplified by universal primers ITS5 and ITS4 (1). The PCR product was purified by the commercial PCR purification kit and the purified PCR product sequenced. The resulting sequences were 100% identical to published S. solani sequences (GenBank Accestion Nos. AF203451 and HQ840713). The amplified ITS region was deposited with NCBI GenBank under Accession No. JQ657726. A representative isolate of the pathogen was inoculated on detached 45-day-old tomato leaves of Malaysian cultivar 152177-A for pathogenicity testing. One wounded and two nonwounded leaflets per leaf were used in this experiment. The leaves were wounded by applying pressure to leaf blades with the serrated edge of a forceps. A 20-μl drop of conidial suspension containing 105 conidia/ml was used to inoculate these leaves (3). The inoculated leaves were placed on moist filter paper in petri dishes and incubated for 48 h at 25°C. Control leaves were inoculated with sterilized distilled water. After 7 days, typical symptoms for S. solani similar to those observed in the farmers' fields developed on both wounded and nonwounded inoculated leaves, but not on noninoculated controls, and S. solani was consistently reisolated. To our knowledge, this is the first report of S. solani causing gray leaf spot of tomato in Malaysia. References: (1) M. P. S. Camara et al. Mycologia 94:660, 2002. (2) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) E. G. Simmons. CBS Biodiversity Series 6:775, 2007.
Plumeria spp., native to tropical America, are popular small trees grown widely in tropical areas of the world and as potted plants elsewhere. P. rubra and P. obtusa cultivars and hybrids are most common. A rust disease of a Plumeria sp. (likely P. rubra based on pointed leaf tips, leaves more than 18 cm (7 inches) long, and high rust susceptibility) was observed in November 2008 and again in June 2009 on homeowner plants in Baton Rouge, LA. A survey of five Baton Rouge retail nurseries in September 2009 revealed that 87% (90 of 103) of the plumeria plants were heavily infected with rust. Early symptoms included numerous 1-mm chlorotic spots on adaxial leaf surfaces followed by leaf chlorosis, necrosis, and abscission. Uredinia were numerous, mostly hypophyllous and yellowish orange. Urediniospores were catenulate, orange en masse, verrucose, globose, ovoid, ellipsoidal or angular, and measured 21.8 to 41.9 × 16.4 to 32.8 μm (average 29.4 × 22.6 μm). The rust was identified as Coleosporium plumeriae Pat. (= C. plumierae) (3). Teliospores were not found during this study. Pathogenicity tests were performed by spraying urediniospores (20,000/ml of deionized water) on three healthy Thai hybrid plumeria plants. Five leaves of each plant were misted with water and covered with plastic bags and three to five leaves were inoculated. Plants were held at 27°C for 27 h in a dew chamber and then moved outdoors. Typical rust symptoms and uredinia with urediniospores developed in 10 days on all inoculated leaves while noninoculated leaves remained healthy. Characteristics and spore measurements matched those of the rust from original infected plants. Additional plumeria rust inoculations were made to other Apocynaceae family members that included Allamanda cathartica, Catheranthus roseus (Madagascar periwinkle), Mandevilla splendens, Nerium oleander, and Vinca major. Catheranthus roseus was very susceptible to C. plumeriae with chlorotic leaf spots developing on the six inoculated plants after 8 days and uredinia with urediniospores appearing after 11 days. None of the other plant genera were susceptible to the rust. Plumeria rust was also observed on plumeria trees in urban landscapes in peninsular (Penang) and Bornean (Kota Kinabalu, Sabah) Malaysia in December 2007. To confirm identity, ~1,000 bp of nuclear rDNA 28S subunit from each (Lousiana, Penang, and Kota Kinabalu) was sequenced with rust-specific primers (1) and shared 100% identity (GenBank No. GU145555-6). Plumeria rust was first found on the island of Guadeloupe (3) and then spread to Central and South America. It has been known from Florida since 1960 under the synonym C. domingense (2), but has not been reported elsewhere in the continental United States. In more recent years, plumeria rust has spread to Hawaii, many Pacific islands, India, China, Taiwan, Thailand, Australia, and Nigeria (4). To our knowledge, this is the first report of plumeria rust from Louisiana and Malaysia and of susceptibility of another member of the Apocynaceae, Madagascar periwinkle, to C. plumeriae. Voucher material from Louisiana and Malaysia has been deposited in the Mycology Herbarium of Louisiana State University (LSUM). References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) Anonymous. Index of Plant Diseases in the United States. U.S. Dept. Agric. Handb. No. 165. Washington, D.C., 1960. (3) N. Patouillard. Bull. Soc. Mycol. Fr. 18:171, 1902. (4) C. To-Anun et al. Nat. Hist. J. Chulalongkorn Univ. 4:41, 2004.
Bacteria play an important roles in the soil ecosystem and in the rhizosphere, they are intricately linked to nutrient content
and its accessibility to plants, plant protection and sometimes pathogenicity. Banana grows well in the tropics and it is
popularly grown in Orang Asli (OA) (indigenous people) settlements. Banana is also grown in commercial plantations.
In traditional planting practices, the OA do not add pesticide nor fertilizer to their crops which are planted for selfsustenance
mainly. On the other hand, fertilizer and pesticide are added to commercial banana plantations to maximise
yield. Rhizosphere bacteria from the banana plant, Pisang Nipah, grown in OA fields and commercial plantations were
identified by clone library construction of the 16S rRNA gene. This was to determine whether farming practices influenced
the bacterial community in the banana plant rhizosphere. Acidobacteria, Proteobacteria and Actinobacteria were found in
all the soil. Other common phyla found in some soil (but not all) were Nitrospirae, Firmicutes, Bacteroidetes, Chloroflexi,
Verrumicrobia, Gemmatimonadetes and Cyanobacteria. The bacterial diversity was a little more diverse in the OA fields
than the commercial plantations. The latter had higher contents of nitrogen, phosphorus and potassium. These could
have exerted selective pressure to reduce the bacterial diversity in the commercial plantations.
Toxoplasma gondii, a ubiquitous pathogen that infects nearly all warm-blooded animals and humans, can cause severe complications to the infected people and animals as well as serious economic losses and social problems. Here, one local strain (TgPIG-WH1) was isolated from an aborted pig fetus, and the genotype of this strain was identified as ToxoDB #3 by the PCR RFLP typing method using 10 molecular markers (SAG1, SAG2, alternative SAG2, SAG3, BTUB, GRA6, L358, PK1, C22-8, C29-2 and Apico). A comparison of the virulence of this isolate with other strains in both mice and piglets showed that TgPIG-WH1 was less virulent than type 1 strain RH and type 2 strain ME49 in mice, and caused similar symptoms to those of ME49 such as fever in piglets. Additionally, in piglet infection with both strains, the TgPIG-WH1 caused a higher IgG response and more severe pathological damages than ME49. Furthermore, TgPIG-WH1 caused one death in the 5 infected piglets, whereas ME49 did not, suggesting the higher virulence of TgPIG-WH1 than ME49 during piglet infection. Experimental infections indicate that the virulence of TgPIG-WH1 relative to ME49 is weaker in mice, but higher in pigs. This is probably the first report regarding a ToxoDB #3 strain from pigs in Hubei, China. These data will facilitate the understanding of genetic diversity of Toxoplasma strains in China as well as the prevention and control of porcine toxoplasmosis in the local region.
The sand fly Phlebotomus papatasi is an important disease-bearing vector. Five entomopathogenic nematodes (EPNs) - Steinernema carpocapsae DD136, Steinernema sp. (SII), S. carpocapsae all, S. abbasi, and Heterorhabditis bacteriophora HP88 - were applied as biocontrol agents against the late third instar larvae of P. papatasi. In addition, the effect of toxin complexes (TCs) of Xenorhabdus nematophila and Photorhabdus luminescens laumondii bacteria was evaluated. Results revealed that S. carpocapsae DD136 was the most virulent species followed by Steinernema sp. (SII) and S. carpocapsae all where LC50 were 472, 565, 962 IJs/ml, respectively. Also, the crude TCs were slightly more active and toxic than their fractionated protein. Histopathological examination of infected larvae with H. bacteriophora HP88 showed negative effect on their midgut cells. In conclusion, EPNs with their symbiotic bacteria are more effective as biocontrol agents than the crude or fractionated TCs against sand fly larvae.
Giardiasis is the major water-borne diarrheal disease present worldwide caused by the common intestinal parasite, Giardia duodenalis. This work aims to investigate the effect of G. duodenalis infection pathogenicity in immunosuppressed animals through histopathological examination. A total of 45 BALB/c mice were divided into four groups; G1 (negative control), G2 (healthy animals exposed to Giardia); G3 (immunosuppressed animals exposed to Giardia), and G4 (non-exposed immunosuppressed animals). Our study revealed that G3 was the most affected group with an infection rate of 100%. The animals showed general weakness, soft stool, and high death rate with severe histopathological changes in the duodenum and mild degenerative changes in hepatic tissues. In G2, the maximal lesions in both duodenum and liver were on the 11th day. We spotted damage in the villi, edema in the central core, and submucosa, in addition to increased cellular infiltration with inflammation in lamina propria. The presence of the parasites within the villi and the lumen was clear. Most of the hepatocytes revealed hydropic and fatty changes, also dilated congested central veins and edema were observed. G3 changes were more intense than G2 with massive Giardia trophozoites between the intestinal villi, lumen, and extensive fatty liver degeneration. Immune suppression plays a significant role in the severity of injury with the Giardia parasites in duodenum and liver cells.
Leaf spot diseases are mainly caused by fungi including Fusarium. In the present study several species of Fusarium were isolated from the leaf spot lesion of mango (Mangifera indica L.) Based on morphological characteristics, TEF-1α sequences and phylogenetic analysis, five species were identified as F. proliferatum, F. semitectum, F. mangiferae, F. solani and F. chlamydosporum. Pathogenicity test indicated that representative isolates of F. proliferatum, F. semitectum and F. chlamydosporum were pathogenic on mango leaves causing leaf spot with low to moderate virulence. Nevertheless, abundance of spots on the leaf can disrupt photosynthesis which in turn reduced growth, and lead to susceptibility to infection by opportunistic pathogens due to weakening of the plant. Fusarium solani and F. mangiferae were non-pathogenic and it is possible that both species are saprophyte which associated with nutrient availability on the surface of the leaf through decaying leave tissues. The occurrence of Fusarium spp. on the leaf spot lesion and the effect from the disease needs to be considered when developing disease management method of mango cultivation as numerous spot on the leaves could effect the photosynthesis process and finally giving low yield and less quality of mango.
The occasional influenza pandemics and the seasonal influenza epidemics have destroyed millions of lives since
the last century. It is therefore necessary to understand the virus replication patterns as this provides essential
information on the virus infectivity, pathogenicity and spread patterns. This study aimed to investigate the replication
of avian influenza A virus H5N1 (A/Chicken/Malaysia/5858/2004) in MDCK cells. In this study, the TCID50 (50% tissue
culture infectious dose) of AIV H5N1 was first determined. The MDCK cells were then infected with AIV H5N1 at TCID50
for 0-48 h. The CPE (cytopathic effect) was observed and cell death was determined hourly. The virus-infected cells
and media were subsequently collected for gene analysis. The results showed that the TCID50 of AIV H5N1 was 10-9
dilution. The CPE percentage showed a strong and positive correlation with the infection period (r = 1.0, n = 9, p <
0.01). The amount of a highly conserved influenza viral gene, M2 gene amplified from infected media (r = 0.471, n =
9, p= > 0.05) and infected cell (r = 0.73, n = 9, p < 0.05) were also positively correlated with the infection period. In
conclusion, although CPE started to be observed in the early time points of infection, however, the M2 gene was only
amplified from the infected media and cells after 48 h and 24 h, respectively. This signifies that AIV H5N1 used in this
study is pathogenic and it is able to cause severe cytopathology to host cells even at low virus load.
Physiological constituents in airway surface liquids (ASL) appear to impact the adherence and invasion potentials of Burkholderia pseudomallei contributing to recrudescent melioidosis. Here, we investigated the factors present in ASL that is likely to influence bacterial adhesion and invasion leading to improved understanding of bacterial pathogenesis. Six B. pseudomallei clinical isolates from different origins were used to investigate the ability of the bacteria to adhere and invade A549 human lung epithelial cells using a system that mimics the physiological ASL with different pH, NaCl, KCl, CaCl2 and glucose concentrations. These parameters resulted in markedly differential adherence and invasion abilities of B. pseudomallei to the lung epithelial cells. The concentration of 20 mM glucose dramatically increased adherence and invasion by increasing the rate of pili formation in depiliated bacteria. Glucose significantly increased adherence and invasion of B. pseudomallei to A549 cells, and presence of NaCl, KCl and CaCl2 markedly ablated the effect despite the presence of glucose. Our data established a link between glucose, enhanced adhesion and invasion potentials of B. pseudomallei, hinting increased susceptibility of individuals with diabetes mellitus to clinical melioidosis.
Nutritional immunity describes mechanisms for withholding essential transition metals as well as directing the toxicity of these metals against infectious agents. Zinc is one of these transition elements that are essential for both humans and microbial pathogens. At the same time, Zn can be toxic both for man and microbes if its concentration is higher than the tolerance limit. Therefore a "delicate" balance of Zn must be maintained to keep the immune cells surveilling while making the level of Zn either to starve or to intoxicate the pathogens. On the other hand, the invading pathogens will exploit the host Zn pool for its survival and replication. Apparently, different sets of protein in human and bacteria are involved to maintain their Zn need. Metallothionein (MT)-a group of low molecular weight proteins, is well known for its Zn-binding ability and is expected to play an important role in that Zn balance at the time of active infection. However, the differences in structural, functional, and molecular control of biosynthesis between human and bacterial MT might play an important role to determine the proper use of Zn and the winning side. The current review explains the possible involvement of human and bacterial MT at the time of infection to control and exploit Zn for their need.
The aim of the present study was to investigate the prevalence of Salmonella spp., Salmonella Enteritidis and Salmonella Typhimurium in retail beef from different retail markets of Selangor area, as well as, to assess their pathogenic potential and antimicrobial resistance. A total of 240 retail beef meat samples (chuck = 60; rib = 60; round = 60; sirloin = 60) were randomly collected. The multiplex polymerase chain reaction (mPCR) in combination with the most probable number (MPN) method was employed to detect Salmonella spp., S. Enteritidis and S. Typhimurium in the meat samples. The prevalence of Salmonella spp., S. Enteritidis and S. Typhimurium in 240 beef meat samples were 7.50, 1.25, and 0.83%, respectively. The microbial loads of total Salmonella was found in the range of <3 to 15 MPN/g. Eight different serovars of Salmonella were identified among the 23 isolates, and S. Agona was the predominant serovar (26.09%). Interestingly, all the Salmonella isolates were resistant to penicillin, erythromycin and vancomycin, but the sensitivity was observed for tetracycline, gentamicin and amoxicillin/clavulanic acid. All 23 isolates were resistant to at least three antibiotics. Two S. Typhimurium isolates (8.70%) exhibited the highest multiple antibiotic resistance (MAR) index value of 0.56 which shown resistance to nine antibiotics. PCR analysis of virulence genes showed that all Salmonella isolates (100%) were positive for the invA gene. Meanwhile, pefA was only identified in S. Enteritidis and S. Typhimurium. The findings in this study indicate that retail beef products tested were widely contaminated with multi-drug resistant (MDR) Salmonella and various virulence genes are present among the isolated Salmonella serovars.
Candida bloodstream infections remain the most frequent life-threatening fungal disease, with Candida albicans accounting for 70% to 80% of the Candida isolates recovered from infected patients. In nature, Candida species are part of the normal commensal flora in mammalian hosts. However, they can transform into pathogens once the host immune system is weakened or breached. More recently, mortality attributed to Candida infections has continued to increase due to both inherent and acquired drug resistance in Candida, the inefficacy of the available antifungal drugs, tedious diagnostic procedures, and a rising number of immunocompromised patients. Adoption of animal models, viz. minihosts, mice, and zebrafish, has brought us closer to unraveling the pathogenesis and complexity of Candida infection in human hosts, leading towards the discovery of biomarkers and identification of potential therapeutic agents. In addition, the advancement of omics technologies offers a holistic view of the Candida-host interaction in a non-targeted and non-biased manner. Hence, in this review, we seek to summarize past and present milestone findings on C. albicans virulence, adoption of animal models in the study of C. albicans infection, and the application of omics technologies in the study of Candida-host interaction. A profound understanding of the interaction between host defense and pathogenesis is imperative for better design of novel immunotherapeutic strategies in future.
Enterococcus faecalis ranks as one of the leading causes of nosocomial infections. A strong epidemiological link has been reported between E. faecalis inhabiting animals and environmental sources. This study investigates the genetic diversity, antibiotic resistance and virulence determinants in E. faecalis from three sources in Malaysia. A total of 250 E. faecalis isolates were obtained consisting of 120 isolates from farm animals, 100 isolates from water sources and 30 isolates from hospitalized patients. Pulse-field gel electrophoresis-typing yielded 63 pulsotypes, with high diversity observed in all sources (D=≥0.901). No pulsotype was common to all the three sources. Each patient room had its own unique PFGE pattern which persisted after six months. Minimum inhibitory concentrations of Vancomycin, Gentamicin, Penicillin, Tetracycline, Nitrofurantoin, Levofloxacin, Ciprofloxacin and Fosfomycin were evaluated. Resistance to Tetracycline was most prevalent in isolates from farm animals (62%) and water sources (49%). Water isolates (86%) had a higher prevalence of the asa1 gene, which encodes for aggregation substance, whereas clinical (78%) and farm animal isolates (87%) had a higher prevalence of the esp gene, encoding a surface exposed protein. This study generates knowledge on the genetic diversity of E. faecalis with antibiotic resistance and virulence characteristics from various sources in Malaysia.