Uma Chaudhary

Emergence of a new antibiotic resistance mechanism in India, Pakistan, and the UK: a molecular, biological, and epidemiological study.

Summary Background Gram-negative Enterobacteriaceae with resistance to carbapenem conferred by New Delhi metallo-β-lactamase 1 (NDM-1) are potentially a major global health problem. We investigated the prevalence of NDM-1, in multidrug-resistant Enterobacteriaceae in India, Pakistan, and the UK. Methods Enterobacteriaceae isolates were studied from two major centres in India—Chennai (south India), Haryana (north India)—and those referred to the UKs national reference laboratory. Antibiotic susceptibilities were assessed, and the presence of the carbapenem resistance gene blaNDM-1 was established by PCR. Isolates were typed by pulsed-field gel electrophoresis of XbaI-restricted genomic DNA. Plasmids were analysed by S1 nuclease digestion and PCR typing. Case data for UK patients were reviewed for evidence of travel and recent admission to hospitals in India or Pakistan. Findings We identified 44 isolates with NDM-1 in Chennai, 26 in Haryana, 37 in the UK, and 73 in other sites in India and Pakistan. NDM-1 was mostly found among Escherichia coli (36) and Klebsiella pneumoniae (111), which were highly resistant to all antibiotics except to tigecycline and colistin. K pneumoniae isolates from Haryana were clonal but NDM-1 producers from the UK and Chennai were clonally diverse. Most isolates carried the NDM-1 gene on plasmids: those from UK and Chennai were readily transferable whereas those from Haryana were not conjugative. Many of the UK NDM-1 positive patients had travelled to India or Pakistan within the past year, or had links with these countries. Interpretation The potential of NDM-1 to be a worldwide public health problem is great, and co-ordinated international surveillance is needed. Funding European Union, Wellcome Trust, and Wyeth.

Quorum sensing and Bacterial Pathogenicity: From Molecules to Disease.

Quorum sensing in prokaryotic biology refers to the ability of a bacterium to sense information from other cells in the population when they reach a critical concentration (i.e. a Quorum) and communicate with them. The “language” used for this intercellular communication is based on small, self-generated signal molecules called as autoinducers. Quorum sensing is thought to afford pathogenic bacteriaa mechanism to minimize host immune responses by delaying theproduction of tissue-damaging virulence factors until sufficientbacteria have amassed and are prepared to overwhelm host defensemechanisms and establish infection. Quorum sensing systems are studied in a large number of gram-negative bacterial species belonging to α, β, and γ subclasses of proteobacteria. Among the pathogenic bacteria, Pseudomonas aeruginosa is perhaps the best understood in terms of the virulence factors regulated and the role the Quorum sensing plays in pathogenicity. Presently, Quorum sensing is considered as a potential novel target for antimicrobial therapy to control multi/all drug-resistant infections. This paper reviews Quorum sensing in gram positive and gram negative bacteria and its role in biofilm formation.

Antibacterial Activity of Synthesized Silver Nanoparticles from Tinospora cordifolia against Multi Drug Resistant Strains of Pseudomonasaeruginosa Isolated from Burn Patients

In the present study, antibacterial activity of silver nanoparticles synthesized from stem of Tinospora cordifolia were analysed against multidrug-resistant strains of Pseudomonas aeruginosa isolated from burn patients. As Pseudomonas aeruginosa is a scourge of hospital burn units and its emergence as multidrug-resistant strains is a major problem in the control of nosocomial infections. Therefore, we tried to establish a combination of medicinal values of Tinospora cordifolia and nanotechnology possibly with the field of medicine for the development of antibacterial agents against these MDR strains.The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, Energy Dispersive Spectroscopy and Fourier Transform Infrared Spectroscopy. Transmission Electron Microscopy and X-Ray Diffraction have revealed the size of silver nanoparticles 9 ± 36 nm and 12.49 nm respectively. Further antibacterial activity of silver nanoparticles prepared from Tinospora cordifolia against multidrug resistant strains was determined by agar well diffusion assay and Minimum Inhibitory Concentration (MIC) was estimated by qualitative experimentation by resazurin based micro broth dilution method. All experiments were done in triplicate. The silver nanoparticles of stem of Tinospora cordifolia showed the zone of inhibition ranges from 10 ± 0.58 to 21 ± 0.25mm. The MIC of AgNPs from stem extract was found to be 6.25 to 200 μg/ml against Pseudomonas aeruginosa strains. Silver nanoparticles from Tinospora cordifolia possess very good antibacterial activity which makes them a potent source of antibacterial agent.

Green silver nanoparticles of Phyllanthus amarus: as an antibacterial agent against multi drug resistant clinical isolates of Pseudomonas aeruginosa

BackgroundPseudomonas aeruginosa infection is a leading cause of morbidity and mortality in burn and immune-compromised patients. In recent studies, researchers have drawn their attention towards ecofriendly synthesis of nanoparticles and their activity against multidrug resistant microbes. In this study, silver nanoparticles were synthesized from aqueous extract of Phyllanthus amarus. The synthesized nanoparticles were explored as a potent source of nanomedicine against MDR burn isolates of P. aeruginosa.ResultsSilver nanoparticles were successfully synthesized using P. amarus extract and the nature of synthesized nanoparticles was analyzed by UV-Vis spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, dynamic light scattering, zeta potential, X- ray diffraction and fourier transform infra-red spectroscopy. The average size of synthesized nanoparticles was 15.7, 24±8 and 29.78 nm by XRD, TEM and DLS respectively. The antibacterial activity of AgNPs was investigated against fifteen MDR strains of P. aeruginosa tested at different concentration. The zone of inhibition was measured in the range of 10±0.53 to 21±0.11mm with silver nanoparticles concentration of 12.5 to 100 µg/ml. The zone of inhibition increased with increase in the concentration of silver nanoparticles. The MIC values of synthesized silver nanoparticles were found in the range of 6.25 to12.5 µg/ml. The MIC values are comparable to the standard antibiotics.ConclusionThe present study suggests that silver nanoparticles from P. amarus extract exhibited excellent antibacterial potential against multidrug resistant strains of P. aeruginosa from burn patients and gives insight of their potential applicability as an alternative antibacterial in the health care system to reduce the burden of multidrug resistance.

Detection of extended-spectrum β-lactamase in Pseudomonas aeruginosa

Purpose: The present study was designed to detect the extended-spectrum β-lactamase (ESBL) production in Pseudomonas aeruginosa and to evaluate the susceptibility pattern. Materials and Methods: One hundred forty-eight isolates of P. aeruginosa were analyzed for the presence of ESBL enzyme by double disc synergy test. Antibiotic sensitivity pattern of ESBL-positive P. aeruginosa was determined. Results: Of the 148 isolates tested, 30 (20.27%) were found to be positive. Maximum ESBL production was found in sputum and tracheostomy swabs (28.57%), followed by pus (24.13%), urine (19.04%), cerebrospinal fluid (CSF) and other sterile body fluids (15.38%) and blood (7.14%). All the ESBL-producing P. aeruginosa isolates were multi-drug-resistant. Isolates were 100% sensitive to imipenem. Ofloxacin was the second most (70%) effective drug. Conclusion: From this study, we conclude the presence of ESBL-positive P. aeruginosa in our hospital. This has important implications as carbapenems remain the only choice of treatment for infections caused by these organisms. The control measures include judicious use of antibiotics and implementation of appropriate infection control measures to control the spread of these strains in the hospital

Bacteraemia in children.

Objectives : (i)To know the etiology of bacteraemia in children, (ii) To learn the antibiotic sensitivity pattern of the isolates.Method : Over the period of thirteen months 4368 blood samples (for blood culture) were collected from children in the age group of 0 day-14 years, suspected of having fever and sepsis. Blood samples were collected for blood culture from each case. Organisms were isolated and identified by conventional methods. Antibiotic susceptibility for each isolate was determined by using modified Stokes method.Result : 1001 cases (22.9%) were culture positive. Incidence of bacteraemia in neonates was 521(33.94%). Gram negative organisms were the most predominant isolates (88.8%). Commonest wasKlebsiella 471 (47.1%) followed bySalmonella sp. 162 (16.2%) andPseudomonas 80 (8%) whereas in gram positive,Staphylococcus aureus 76 (7.6%) was the most common. Maximum sensitivity was seen by sulbactum/cefaperazone combination-969 (98.2%) by all isolates. Linezolid 97 (99.0%) was the most sensitive drug for gram positive isolates.Conclusion. Gram negative multidrug resistant organisms were the main cause of septicemia in all the age groups. Therefore great caution is required in selection of antibiotic therapy.

Changing trend of antimicrobial resistance among gram-negative bacilli isolated from lower respiratory tract of ICU patients: A 5-year study

Background: Lower respiratory tract infections (LRTIs) are the most frequent infections among patients in intensive care units (ICUs). Aim: To track the resistance rate among the causative agents causing LRTI in the ICU patients. Design and Settings: This is a retrospective study done in a tertiary care hospital. Materials and Methods: Transtracheal or bronchial aspirates from 2776 patients admitted to the ICU were cultured and identified, and antibiotic sensitivity was performed by standard methods. Results: Of 2776 specimens, 1233 (44.41%) isolates were recovered, of which 1123 (91.07%) were gram-negative bacilli (GNB) and 110 (8.92%) were gram-positive organisms. From 2004 to 2009, Pseudomonas aeruginosa remained the most common pathogen. In phase I, high level of resistance (79–98%) was observed against all GNB. During phase II increasing trend in resistance to cephalosporins and declining trend in resistance to aminoglycosides against most GNB were observed. Multidrug resistance (resistance to three or more than three drugs) was observed in 83% of total isolates. Conclusions: Gram-negative organisms are the predominant pathogens causing LRTI in ICU. The increasing trend of resistance to cephalosporins and carbapenems in gram-negative organisms is very disturbing. Judicious use of antimicrobial agents is essential to prevent the emergence of multidrug-resistant bacteria in the ICU.

Detection of extended spectrum β-lactamase production among uropathogens

Background: Detection of extended spectrum β-lactamase (ESBL) production among uropathogens is an important marker of endemicity. Aim: Intervention of this endemic transmission is important for the control of initial outbreak of ESBL producing organisms in a hospital or specialized unit of hospital. Materials and Methods: During the study period of one and a half months, 1,551 urine samples were processed for significant bacteriuria. Two hundred gram negative bacterial isolates were tested for ESBL production. Antimicrobial sensitivity pattern was ascertained for ESBL producing isolates. Results: ESBL production was seen in 36% of isolates. All the isolates were multidrug resistant with uniform sensitivity to imipenem. Conclusion: This study reveals the significant prevalence of ESBL producing organisms in this north Indian tertiary care hospital. Constant revision of antibiotic policies with infection control interventions is suggested.

Emergence of Nonalbicans Candida in neonatal septicemia and antifungal susceptibility: Experience from a tertiary care center

Aims: To know the distribution and antifungal susceptibility pattern of Candida species in neonatal septicemia cases. Materials and Methods: In a prospective analysis blood samples from 825 clinically suspected cases of neonatal septicemia, collected aseptically, were cultured to look for the role of Candida spp. in septicemia. Candida isolates were speciated by germ tube test, Hi-CHROME agar, sugar fermentation, and sugar assimilation tests using standard protocol. All the Candida isolates were tested for antifungal susceptibility to fluconazole by the Disk Diffusion (DD) method and broth micro dilution-minimum inhibitory concentration (BMD-MIC) method using NCCLS guidelines. Results: Isolation rate of Candida from neonatal septicemia cases was 8.1%. Most common isolate was C. tropicalis (61.19%), followed by C. albicans (19.40%), C. glabrata (11.94%), C. parapsilosis (5.97%) and C. guillermondii (1.49%). Low birth weight and previous antibiotic prophylaxis was found in 100% cases. Crude mortality rate was 50.1%. By DD method, 95.53% of the Candida isolates were sensitive to fluconazole. A discrepancy between DD method and BMD-MIC method was noted in 4.47% strains. One isolates each of C. tropicalis, C. albicans, and C. glabrata showed discrepancy. Conclusion: Nonalbicans Candida has emerged as an important cause of neonatal septicemia. Routine susceptibility testing of Candida isolates by DD method should be confirmed by BMD-MIC method. Fluconazole can be used as empirical therapy for neonatal candidemia at our center.

Biofilm and multidrug resistance in uropathogenic Escherichia coli

Abstract Context: Escherichia coli is known as causative agent of urinary tract infections (UTIs) tends to form microcolonies in mucosa lining of urinary bladder known as biofilm. These biofilms make the organism to resist the host immune response, more virulent and lead to the evolution of antibacterial drug resistance by enclosing them in an extracellular biochemical matrix. Aims: This study was done to know the association of various virulence factors and biofilm production in uropathogenic E. coli (UPEC) and antibiotic susceptibility pattern. Settings and design: This study was conducted in Pt. B.D. Sharma PGIMS, Rohtak, Haryana during a period of 1 year from January 2011 to December 2011. Methods and material: Biofilm was detected by microtiter plate (MTP) method, and various virulence factors like hemolysin, hemagglutination, gelatinase, siderophore production, serum resistance, and hydrophobicity were detected. The antibiotic susceptibility testing was done by modified Kirby-Bauer disk diffusion and the disk diffusion method was used to confirm the ESBL, AmpC, MBL production by the UPEC statistical analysis used: The data were analyzed by using SPSS version 17.0. A two-sided P-value of less than or equal to 0·05 was considered to be significant. Results: Biofilm production was found in 18 (13·5%) isolates, more commonly in females (two times). These isolates were found to be resistant to antibiotics common in use and were 100% MDR. Conclusions: Biofilm production makes the organism to be more resistant to antibiotics and virulent as compared to non-biofilm producers.