Genetic Diversity and Streptomycin Sensitivity in <i>Xanthomonas axonopodis</i> pv. <i>punicae</i> Causing Oily Spot Disease in Pomegranates

Xanthomonas axonopodis pv. punicae (Xap) causes bacterial blight disease in pomegranates, often leading to 60–80% economic loss. In absence of a suitable Xap-resistant variety, the near-monoculture of the susceptible variety, Bhagwa, has aggravated the problem further. In recent times, Xap has spread to different geographical regions, indicating the wide adaptability of the pathogen. Moreover, lower sensitivity of Xap towards streptocycline containing streptomycin sulphate and tetracycline sulphate (9:1) under field conditions is frequently reported. Therefore, the current study was undertaken to assess the genetic variability of Xap isolates using SSR markers, their in vitro sensitivity towards streptomycin was evaluated, and the probable molecular basis of acquired resistance was studied. Two highly diverse isolates showed extreme differences in their pathogenicity, indicating the highly evolving nature of the pathogen. Moreover, all the isolates showed less than 50% growth inhibition on media containing 1500 µg/mL streptomycin, indicating a lower level of antibiotic sensitivity. On the molecular level, 90% of the isolates showed the presence of strA-strB genes involved in streptomycin metabolism. Additionally, G to A transitions were observed in the rpsL gene in some of the isolates. The molecular data suggest that horizontal gene transfer (strAB) and/or spontaneous gene mutation (in rpsL) could be responsible for the observed lower sensitivity of Xap towards streptomycin

Genetic Diversity and Streptomycin Sensitivity in Xanthomonas axonopodis pv. punicae Causing Oily Spot Disease in Pomegranates

Xanthomonas axonopodis pv. punicae (Xap) causes bacterial blight disease in pomegranates, often leading to 60&ndash;80% economic loss. In absence of a suitable Xap-resistant variety, the near-monoculture of the susceptible variety, Bhagwa, has aggravated the problem further. In recent times, Xap has spread to different geographical regions, indicating the wide adaptability of the pathogen. Moreover, lower sensitivity of Xap towards streptocycline containing streptomycin sulphate and tetracycline sulphate (9:1) under field conditions is frequently reported. Therefore, the current study was undertaken to assess the genetic variability of Xap isolates using SSR markers, their in vitro sensitivity towards streptomycin was evaluated, and the probable molecular basis of acquired resistance was studied. Two highly diverse isolates showed extreme differences in their pathogenicity, indicating the highly evolving nature of the pathogen. Moreover, all the isolates showed less than 50% growth inhibition on media containing 1500 &micro;g/mL streptomycin, indicating a lower level of antibiotic sensitivity. On the molecular level, 90% of the isolates showed the presence of strA-strB genes involved in streptomycin metabolism. Additionally, G to A transitions were observed in the rpsL gene in some of the isolates. The molecular data suggest that horizontal gene transfer (strAB) and/or spontaneous gene mutation (in rpsL) could be responsible for the observed lower sensitivity of Xap towards streptomycin

Characterization of <i>Alternaria</i> and <i>Colletotrichum</i> Species Associated with Pomegranate (<i>Punica</i> <i>granatum</i> L.) in Maharashtra State of India

Fungal pathogens are a major constraint affecting the quality of pomegranate production around the world. Among them, Alternaria and Colletotrichum species cause leaf spot, fruit spot or heart rot (black rot), and fruit rot (anthracnose) or calyx end rot, respectively. Accurate identification of disease-causing fungal species is essential for developing suitable management practices. Therefore, characterization of Alternaria and Colletotrichum isolates representing different geographical regions, predominantly Maharashtra—the Indian hub of pomegranate production and export—was carried out. Fungal isolates could not be identified based on morphological characteristics alone, hence were subjected to multi-gene phylogeny for their accurate identification. Based on a maximum likelihood phylogenetic tree, Alternaria isolates were identified as within the A. alternata species complex and as A. burnsii, while Colletotrichum isolates showed genetic closeness to various species within the C. gloeosporioides species complex. Thus, the current study reports for the first time that, in India, the fruit rots of pomegranate are caused by multiple species and not a single species of Alternaria and Colletotrichum alone. Since different species have different epidemiology and sensitivity toward the commercially available and routinely applied fungicides, the precise knowledge of the diverse species infecting pomegranate, as provided by the current study, is the first step towards devising better management strategies

Pharmacokinetics-pharmacodynamics analysis of bicyclic 4-nitroimidazole analogs in a murine model of tuberculosis

10.1371/journal.pone.0105222PLoS ONE98e10522

In Vitro and In Planta Antagonistic Effect of Endophytic Bacteria on Blight Causing <i>Xanthomonas axonopodis</i> pv. <i>punicae</i>: A Destructive Pathogen of Pomegranate

Pomegranate bacterial blight caused by Xanthomonas axonopodis pv. punicae (Xap) is a highly destructive disease. In the absence of host resistance to the disease, we aimed to evaluate the biocontrol potential of endophytic bacteria against Xap. Thus, in this study, we isolated endophytes from pomegranate plants, identified them on the basis of 16S rDNA sequencing, tested them against Xap, and estimated the endophyte-mediated host defense response. The population of isolated endophytes ranged from 3 × 106 to 8 × 107 CFU/g tissue. Furthermore, 26 isolates were evaluated for their biocontrol activity against Xap, and all the tested isolates significantly reduced the in vitro growth of Xap (15.65% ± 1.25% to 56.35% ± 2.66%) as compared to control. These isolates could reduce fuscan, an uncharacterized factor of Xap involved in its aggressiveness. Lower blight incidence (11.6%) and severity (6.1%) were recorded in plants sprayed with endophytes 8 days ahead of Xap spray (Set-III) as compared to control plants which were not exposed to endophytes (77.33 and 50%, respectively%) during in vivo evaluation. Moreover, significantly high phenolic and chlorophyll contents were estimated in endophyte-treated plants as compared to control. The promising isolates mostly belonged to the genera Bacillus, Burkholderia, and Lysinibacillus, and they were deposited to the National Agriculturally Important Microbial Culture Collection, India

Pharmacokinetics-Pharmacodynamics Analysis of Bicyclic 4-Nitroimidazole Analogs in a Murine Model of Tuberculosis

<div><p>PA-824 is a bicyclic 4-nitroimidazole, currently in phase II clinical trials for the treatment of tuberculosis. Dose fractionation pharmacokinetic-pharmacodynamic studies in mice indicated that the driver of PA-824 <i>in</i><i>vivo</i> efficacy is the time during which the free drug concentrations in plasma are above the MIC (<i>fT_>MIC</i>). In this study, a panel of closely related potent bicyclic 4-nitroimidazoles was profiled in both <i>in</i><i>vivo</i> PK and efficacy studies. In an established murine TB model, the efficacy of diverse nitroimidazole analogs ranged between 0.5 and 2.3 log CFU reduction compared to untreated controls. Further, a retrospective analysis was performed for a set of seven nitroimidazole analogs to identify the PK parameters that correlate with <i>in</i><i>vivo</i> efficacy. Our findings show that the <i>in</i><i>vivo</i> efficacy of bicyclic 4-nitroimidazoles correlated better with lung PK than with plasma PK. Further, nitroimidazole analogs with moderate-to-high volume of distribution and Lung to plasma ratios of >2 showed good efficacy. Among all the PK-PD indices, total lung <i>T_>MIC</i> correlated the best with <i>in</i><i>vivo</i> efficacy (<i>r_s</i> = 0.88) followed by lung C_max/MIC and AUC/MIC. Thus, lung drug distribution studies could potentially be exploited to guide the selection of compounds for efficacy studies, thereby accelerating the drug discovery efforts in finding new nitroimidazole analogs.</p></div

Correlation of PK parameters (C_max, AUC) with <i>in vivo</i> efficacy in mice for bicyclic 4-nitroimidazole analogs in total plasma concentration (A), free plasma concentration (B) and total lung concentration (C).

<p>Each data point represents Δ mean log lung CFU reduction compared to untreated controls (mean value ± SEM from 5 animals). <i>r_s</i> is the Spearman’s rank correlations coefficient.</p

Correlation of PK-PD indices (C_max/MIC, AUC/MIC and <i>T_>MIC</i>) with <i>in vivo</i> efficacy in mice for bicyclic 4-nitroimidazole analogs in total plasma concentration (A), free plasma concentration (B) and total lung concentration (C).

<p>Each data point represents Δ Mean log lung CFU reduction compared to untreated controls (mean value ± SEM from 5 animals). <i>r_s</i> is the Spearman’s rank correlations coefficient.</p

Correlation of volume of distribution with <i>in vivo</i> efficacy in mice for bicyclic 4-nitroimidazole analogs.

<p>Each data point represents Δ Mean log lung CFU reduction compared to untreated controls (mean value ± SEM from 5 animals). <i>r_s</i> is the Spearman’s rank correlations coefficient.</p

Chemical structures of bicyclic 4-nitroimidazole analogs used in this study.

<p>Chemical structures of bicyclic 4-nitroimidazole analogs used in this study.</p