Ashok Rattan

Ashok Rattan
pathkind labs · Quality R & D Knowledge Forum

MBBS, MD, MAMS

About

171
Publications
20,723
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3,535
Citations
Citations since 2017
11 Research Items
1283 Citations
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2017201820192020202120222023050100150200
2017201820192020202120222023050100150200
2017201820192020202120222023050100150200

Publications

Publications (171)
Article
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This is the first study on detailed characterization of strain of Cryptococcus neoformans from cases of Cryptococcal meningitis in India
Article
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Reports of clinical isolates of Cryptococcus neoformans often lack information on their mating types, molecular types, and in vitro antimycotic susceptibilities. This study compares these and other related characteristics of fifteen strains of C. neoformans obtained from cases of meningitis in different regions of India. PCR was used to determine t...
Article
Though a decline has been seen in child mortality and morbidity over the last decades, sepsis in neonates and infants remains a major cause of death. Optimal use of antibiotics in sepsis management is a key factor which can further reduce the number of poor clinical outcomes. Selecting the right antibiotic to which the offending bacteria is suscept...
Chapter
Tuberculosis is an ancient disease which has become rampant in recent times due to it’s multidrug resistant nature. Global community is concerned about it and measures to control it are being taken in the form of Millennium Development Goals and Stop TB Strategy. These goals can be achieved by early case finding and better diagnosis. Detection of l...
Chapter
Causative organisms, pathogenesis and clinical features of sexually transmitted infections
Article
Full-text available
Background: There is emergence of resistance to the last-line antibiotics such as carbapenems in Intensive Care Units (ICUs), leaving little effective therapeutic options. Since there are no more newer antibiotics in the armamentarium in the near future, it has become imperative that we harness the interdisciplinary knowledge for the best clinical...
Article
Background: There is emergence of resistance to the last-line antibiotics such as carbapenems in Intensive Care Units (ICUs), leaving little effective therapeutic options. Since there are no more newer antibiotics in the armamentarium in the near future, it has become imperative that we harness the interdisciplinary knowledge for the best clinical...
Chapter
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In the 20th century, particularly in the 1950s and 1960s, the discovery and development of antimicrobial agents along with stringent vaccination schedule and improved hygiene led to tremendous improvements in life expectancy globally. However, in the last 20 years, it is distressing to observe that bacterial resistance has emerged as a major threat...
Article
This study reports the anti-anaerobic properties of ranbezolid, a new investigational oxazolidinone. A time-kill kinetics study against anaerobes showed that ranbezolid was superior to linezolid and killed the anaerobic pathogens at 4-8h, except for Bacteroides fragilis where killing was observed at 24h. In addition, the time-kill kinetics study sh...
Article
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To describe the misidentification of Brucella melitensis as Bergeyella zoohelcum by MicroScan WalkAway®, a commonly used bacterial identification system. A 35-year-old man was admitted to the Intensive Care Unit with sepsis syndrome. Three sets of aerobic blood culture samples were positive after 48 h of incubation. The isolated organism was identi...
Article
Antibiotic resistance, a global concern, is particularly pressing in developing nations, including India, where the burden of infectious disease is high and healthcare spending is low. The Global Antibiotic Resistance Partnership (GARP) was established to develop actionable policy recommendations specifically relevant to low- and middle-income coun...
Article
QuantiFERON-TB Gold In-Tube Test is an in vitro laboratory diagnostic test which is used as an aid in diagnosing Mycobacterium tuberculosis infection or disease. Sometimes it is associated with indeterminate results which make the diagnosis difficult for the patients. Here we sought to understand the possible reasons for indeterminate results obtai...
Article
Full-text available
We screened 194 Mycobacterium tuberculosis strains isolated from tuberculosis (TB) patients in Delhi and neighboring regions in India to identify the prevalence of extensive drug resistance (XDR) in clinical isolates. Among these, 104 isolates were found to be multidrug resistant (MDR), and 6 were identified as XDR isolates, which was later confirm...
Article
We report a case of primary pulmonary cryptococcosis in a post-renal transplant patient. A 65-year-old male renal transplant patient was admitted to the hospital with a low grade fever of 1 month, radiologically mimicking tuberculosis (TB). Broncho-alveolar fluid (BAL) shows capsulated yeast, and Cryptococcus neoformans was grown on culture support...
Article
A number of 5-substituted derivatives of Ranbezolid, a novel oxazolidinone were synthesized. Antibacterial activity of the compounds against a number of sensitive and resistant bacteria showed promising results.
Article
Full-text available
Oxazolidinones are known to inhibit protein biosynthesis and act against a wide spectrum of gram-positive bacteria. A new investigational oxazolidinone, ranbezolid, inhibited bacterial protein synthesis in Staphylococcus aureus and Staphylococcus epidermidis. In S. epidermidis, ranbezolid showed inhibition of cell wall and lipid synthesis and a dos...
Article
The recent increase in the number of multidrug-resistant clinical isolates of M. tuberculosis. has created an urgent need for the discovery and development of new antituberculosis leads. Natural products form one avenue in the search for new antitubercular agents. Cyanobacteria (blue-green algae) are a diverse group of photosynthetic, prokaryotic m...
Article
Adhesion to biomaterial is assumed to be a crucial step in the pathogenesis of foreign body infection. Slime producing Staphylococcus epidermidis and Staphylococcus aureus have emerged as a preeminent cause of nosocomial bacteremia and infections of prosthetic medical devices. We evaluated the time-dependent anti-adhesive effect of RBx 7644 (ranbez...
Article
PROBLEM: Recent reports indicate high incidence of genital infections, most of which are sexually transmitted. Although specific drugs and antibiotics are available for some, a safe spermicidal formulation with wide spectrum antimicrobial action would be a desirable addition to the presently available spermicides. METHODS: Formulations at different...
Article
Several potent oxazolidinone antibacterial agents were obtained by systematic modification of the linker between the five-membered heterocycle and the piperazinyl ring of RBx 7644 (Ranbezolid, 1) and its thienyl analogue 2, leading to the identification of an expanded spectrum compound RBx 8700 (6b).
Article
Full-text available
Decreased susceptibility of Neisseria meningitidis isolates to ciprofloxacin emerged from an outbreak in Delhi, India. Results of antimicrobial susceptibility testing of the meningococcal isolates to ciprofloxacin and further sequencing of DNA gyrase A quinolone-resistance-determining region confirmed the emergence of ciprofloxacin resistance in th...
Data
Full-text available
Antimicrobial susceptibility pattern of Neisseria meningitidis isolates from the outbreak during April-July 2005 Delhi, India*
Article
Novel oxazolidinone derivatives of the lead compound RBx 8700, containing methylene oxygen- and methylene sulfur-linked substituents at the C5-position, were synthesized. Antibacterial screening of these compounds against a panel of resistant and susceptible Gram-positive and fastidious Gram-negative bacteria gave compounds 2 and 4 as new antibacte...
Article
Full-text available
Disulfiram, an alcohol antagonistic drug has been on the market since 1949 with 80% bioavailability and an established safety profile. Recently it has been reported as a P-glycoprotein efflux pump modulator. Herein we report its antifungal potential. The MIC50 and MIC90 of disulfiram for yeast isolates is 4 and 8 microg/ml, respectively, and the MI...
Article
Oxazolidinones are a new class of totally synthetic antibacterial agents with wide spectrum of activity against a variety of clinically significant susceptible and resistant bacteria. These compounds have been shown to inhibit translation at the initiation phase of protein synthesis. DuP-721, the first oxazolidinone showed good activity against M....
Article
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In resource-constrained laboratories of developing countries determination of antifungal susceptibility testing by NCCLS/CLSI method is not always feasible. We describe herein a simple yet comparable method for antifungal susceptibility testing. Reference MICs of 72 fungal isolates including two quality control strains were determined by NCCLS/CLSI...
Article
RBx 8700, an investigational oxazolidinone, has excellent activity against respiratory pathogens. We evaluated the in vitro minimum inhibitory concentration (MIC) and bactericidal activity of RBx 8700 against Mycobacterium tuberculosis and Mycobacterium avium complex (MAC) isolates. RBx 8700 had an MIC of 1 gLg/ml against M. tuberculosis isolates r...
Article
Blue green microalgae have been identified as one of the promising groups of organism from which biochemically active natural products have been isolated. Aqueous and organic extracts of nine blue green microalgae strains were screened against in vitro generated vancomycin intermediate resistant Staphylococcus aureus (VISA) strains. Aqueous extract...
Article
Vancomycin has been the drug of choice for 30 years for the treatment of methicillin-resistant Staphylococcus aureus (MRSA). Emergence of decreased vancomycin susceptibility in MRSA strains presents a significant clinical problem with few therapeutic options. This study was performed to generate and characterise S. aureus strains with reduced susce...
Article
The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-posi...
Article
Purpose: The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. Methods: For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. Results: Of the 152 Staphylococcus spp. 88(57.8...
Article
Full-text available
Adhesion to biomaterial is assumed to be a crucial step in the development of staphylococcal foreign body infections. Production of extracellular slime has major implications for the development and implementation of therapeutic strategies. The effect of extracted slime was investigated on the activity of vancomycin, teicoplanin, linezolid, quinupr...
Article
Novel oxazolidinones were synthesized containing a number of substituted five-membered heterocycles attached to the 'piperazinyl-phenyl-oxazolidinone' core of eperezolid. Further, the piperazine ring of the core was replaced by other diamino-heterocycles. These modifications led to several compounds with potent activity against a spectrum of resist...
Article
Full-text available
Eales’ disease is most frequently found linked with tuberculosis. Hence, the present prospectiverandomized study was conducted to evaluate the role of anti-tuberculosis therapy in Eales’disease,by carrying out physical, neurological, ophthalmological examination and laboratory tests. The resultsof present study reveals that there is no rationale fo...
Article
The decision to develop a new chemical entity should not only be based on its ability to inhibit multidrug-resistant tuberculosis (MDR-TB) strains but also on its ability to enter macrophages and be active against intracellular bacteria. RBx 7644 and RBx 8700, two novel extended spectrum oxazolidinones, were investigated for their activity against...
Patent
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Azole derivatives as antifungal agents
Article
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The purpose of this study was to simultaneously screen for Extended-spectrum beta-lactamases (ESBL) and AmpC beta-lactamases in gram negative clinical isolates from four tertiary care hospitals and further to compare two detection methods three-dimensional extraction method and AmpC disk test for AmpC beta-lactamases. A total of 272 isolates were s...
Patent
Full-text available
Compostos De Azol E Seu Uso Como Agentes Antifúngicos,
Patent
Full-text available
Azole Derivatives as Antifungal Agents,
Article
The purpose of this study was to simultaneously screen for Extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases in gram negative clinical isolates from four tertiary care hospitals and further to compare two detection methods three-dimensional extraction method and AmpC disk test for AmpC β-lactamases. A total of 272 isolates were screened f...
Article
Full-text available
A novel synthesis of thiazolidine-2-thione and thiazolidin-2-one derivatives is described with the iodo-cyclothiocarbamation reaction as the key step for the heterocyclic ring formation. This new method has been applied to the synthesis of thiazolidinones as bioisosteric analogs of Linezolid 2. Antimicrobial properties of two new thiazole derivativ...
Patent
Full-text available
Derivatives of 2,2,4-Trisubstituted Tetrahydrofuran as Antifungal Agents,
Article
The objective of this study was to investigate screening methodologies, to detect Staphylococcus aureus strains with decreased susceptibility to vancomycin. Three methods were used to screen 160 Staphylococcus aureus clinical isolates along with ATCC quality control strains. Subsequently, MIC of all these 160 strains were determined by NCCLS method...
Article
Full-text available
The objective of this study was to investigate screening methodologies, to detect Staphylococcus aureus strains with decreased susceptibility to vancomycin. Three methods were used to screen 160 Staphylococcus aureus clinical isolates along with ATCC quality control strains. Subsequently, MIC of all these 160 strains were determined by NCCLS method...
Article
Biofilm associated infections are becoming more common. Treatment outcome of device related infections cannot be predicted by the results of a standard susceptibility test such as the MIC. Microorganisms involved in device related infections have a slow growth rate and adhere to surfaces. Activity against glass adherent bacteria has been shown to b...
Article
Antibiotic resistance is a global problem. In the community, resistance can result from nosocomial acquisition of resistant bacteria, emergence of resistance consequent upon its use in the community or acquisition of resistant pathogens as a result of travel. Resistance can also occur as a result of using antimicrobial agents as 'growth promoters'...
Article
In cryptococcosis, fluconazole is a standard prophylactic, therapeutic and maintenance option, particularly in the expanding HIV/AIDS group. However, its excessive use may lead to resistance in Cryptococcus neoformans. Variations in clinical response to fluconazole have already been noted elsewhere, and cases of post-therapy relapse are not uncommo...
Poster
RBx 7445 and RBx 7635: novel triazoles with potent broad-spectrum antifungal activity,
Article
Full-text available
The activity of ranbezolid (RBX 7644), a new oxazolidinone, against 306 anaerobes was compared with those of 11 other agents. The MICs at which 50% of the isolates tested are inhibited and those at which 90% of the isolates tested are inhibited (in micrograms per milliliter) were as follows: ranbezolid, 0.03 and 0.5; linezolid, 2 and 4; vancomycin,...
Article
Full-text available
For 260 pneumococcal and 266 staphylococcal strains, ranbezolid MICs ranged from ≤0.06 to 4 μg/ml. The MICs for pneumococci were similar irrespective of the strains' β-lactam, macrolide, or quinolone susceptibilities, and ranbezolid MICs for coagulase-negative staphylococci were lower than those for Staphylococcus aureus. Ranbezolid was bacteriosta...
Poster
Full-text available
Thiotriazolones: A new class of potent antifungal agents
Article
Full-text available
The present study tracks the development of low-level azole resistance in in vitro fluconazole-adapted strains of Candida albicans, which were obtained by serially passaging a fluconazole-susceptible dose-dependent strain, YO1-16 (fluconazole MIC, 16 μg ml−1) in increasing concentrations of fluconazole, resulting in strains YO1-32 (fluconazole MIC,...
Article
Recent reports indicate high incidence of genital infections, most of which are sexually transmitted. Although specific drugs and antibiotics are available for some, a safe spermicidal formulation with wide spectrum antimicrobial action would be a desirable addition to the presently available spermicides. Formulations at different dilutions were te...
Article
In this study, we report a modified procedure for extraction of high-quality genomic DNA that is rapid, simple, biologically nonhazardous, and generally applicable to pathogenic bacteria. Bacterial cells were pretreated with 70% ethanol prior to enzymatic digestion with lysozyme. Exposure of bacterial cells to 70% ethanol sterilized the cultures, m...
Article
Fluoroquinolones have some of the properties of an 'ideal' anti-microbial agent. Because of their potent broad spectrum activity and absence of transferable mechanism of resistance or inactivating enzymes, it was hoped that clinical resistance to this useful group of drugs would not occur. However, over the years, due to intense selective pressure...
Article
The present study was aimed at assessing the predictive utility of anti-Cag A antibodies in differentiating patients of duodenal ulcer (DU) and non ulcer dyspepsia (NUD) from asymptomatic controls in a developing country. Sera from 120 subjects were tested for antibodies to Cag A using the immunodominant portion of a recombinant 37.5 kDa fusion pro...
Article
Full-text available
A total of 116 isolates from patients attending the out-patient department at the All India Institute of Medical Sciences, New Delhi and the New Delhi Tuberculosis Centre, New Delhi, India were collected. They were analyzed for resistance to drugs prescribed in the treatment for tuberculosis. The drug resistance was initially determined by microbio...