Amita Jain

Biofilm production, a marker of pathogenic potential of colonizing and commensal staphylococci.

Biofilm is one of the known virulence factors of staphylococci, a human and animal pathogen and commensal. Some of the strains become invasive under favorable conditions while others do not cause disease. Early detection and management of potentially pathogenic staphylococci is the essential step to prevent device-associated infections. There is also a need to evaluate one simple method for the detection of potential pathogens. Hence this study was planned to study the difference in potential of commensal, colonizing and invasive strains of staphylococci to produce biofilm. We used one qualitative (Congo red agar) and one quantitative (microtiter plate) method for detection of biofilm production and evaluated the sensitivity and specificity of Congo red agar method by using microtiter plate method as a gold standard. We consecutively enrolled staphylococcal strains isolated from peripheral intravenous device (IVD), venous blood, site of IVD insertion and nasal mucosa of patients admitted to pediatric ward with peripheral intravenous devices in place for more than 48 h. Total 100 invasive, 50 colonizing and 50 commensal isolates were studied. Of 100 invasive isolates 74% (74/100) were biofilm positive while only 68% (34/50) colonizing and 32% (16/50) commensal isolates were biofilm positive. The difference in biofilm production by commensal, colonizing and invasive strains was statistically significant (p<0.0001). Sensitivity and specificity of Congo red agar test for detection of biofilm producers were 90.63% and 90.79% for Staphylococcus aureus and 75.86% and 96.88% respectively for coagulase negative staphylococci. CRA is a method that could be used to determine whether an isolate has the potential for biofilm production or not.

Extensively drug-resistant tuberculosis: current challenges and threats.

Extensively drug-resistant tuberculosis (XDR-TB) is defined as tuberculosis caused by a Mycobacterium tuberculosis strain that is resistant to at least rifampicin and isoniazid among the first-line antitubercular drugs (multidrug-resistant tuberculosis; MDR-TB) in addition to resistance to any fluroquinolones and at least one of three injectable second-line drugs, namely amikacin, kanamycin and/or capreomycin. Recent studies have described XDR-TB strains from all continents. Worldwide prevalence of XDR-TB is estimated to be c. 6.6% in all the studied countries among multidrug-resistant M. tuberculosis strains. The emergence of XDR-TB strains is a reflection of poor tuberculosis management, and controlling its emergence constitutes an urgent global health reality and a challenge to tuberculosis control activities in all parts of the world, especially in developing countries and those lacking resources and as well as in countries with increasing prevalence of HIV/AIDS.

Multidrug resistant to extensively drug resistant tuberculosis: What is next?

Drug resistant tuberculosis is a man made problem. While tuberculosis is hundred percent curable, multidrug resistant tuberculosis (MDR-TB) is difficult to treat. Inadequate and incomplete treatment and poor treatment adherence has led to a newer form of drug resistance known as extensively drug resistant tuberculosis (XDR-TB). XDR-TB is defined as tuberculosis caused by Mycobacterium tuberculosis strain, which is resistant to at least rifampicin and isoniazid among the first line anti tubercular drugs (MDR-TB) in addition to resistance to any fluroquinolones and at least one of three injectable second line anti tubercular drugs i.e. amikacin, kanamycin and/or capreomycin. Mismanagement of tuberculosis paves the way to drug resistant tuberculosis. Emergence of XDR-TB is reported world wide. Reported prevalence rates of XDR-TB of total MDR cases are; 6.6% overall worldwide, 6.5% in industrialized countries, 13.6% in Russia and Eastern Europe, 1.5% in Asia, 0.6% in Africa and Middle East and 15.4% in Republic of Korea. Better management and control of tuberculosis specially drug resistant TB by experienced and qualified doctors, access to standard microbiology laboratory, co-morbitidy of HIV and tuberculosis, new anti-TB drug regimens, better diagnostic tests, international standards for second line drugs (SLD)-susceptibility testing, invention of newer antitubercular molecules and vaccines and knowing the real magnitude of XDR-TB are some of the important issues to be addressed for effective prevention and management of XDR-TB.

Polymerase Chain Reaction vs. Conventional Diagnosis in Fine Needle Aspirates of Tuberculous Lymph Nodes

OBJECTIVE To compare four conventional methods of diagnosing tuberculous lymphadenophathy (TL)--namely fine needle aspiration cytology (FNAC), Zeihl-Neelsen staining of smears for acid-fast bacilli (AFB), culture for Mycobacterium tuberculosis (MTB) and lymph node biopsies--with the polymerase chain reaction (PCR) in order to assess the practicability and advantage of its use in routine diagnosis in a developing country. STUDY DESIGN Fine needle aspirates from 142 consecutive patients presenting with lymphadenopathy (mainly cervical) without any known systemic involvement underwent cytomorphologic diagnosis, AFB smears, culture for MTB, confirmatory biopsy and PCR for MTB. The aspirates from cases other than TL served as controls for PCR. RESULTS Correct diagnosis of tuberculosis could be made in 94.87% of cases by a combination of the four methods. PCR was done in 52 cases, 39 confirmed TL and 13 controls. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value of PCR were 94.44%, 38.23%, 44.73% and 92.85%, respectively, when culture alone was considered the gold standard. However, specificity (38.23-92.30%) and PPV (44.73-97.36%) of PCR increased remarkably when response to treatment was taken as the final arbiter. CONCLUSION The four conventional tests were found to be the methods of choice for the diagnosis of TL in developing countries. PCR should be reserved for problem cases.

High nasopharyngeal carriage of drug resistant Streptococcus pneumoniae and Haemophilus influenzae in north Indian schoolchildren

Objectives  To determine the carriage rate of Streptococcus pneumoniae and Haemophilus influenzae in healthy Indian schoolchildren. The prevalence of antibiotic resistant strains in the community may be used to assess the trends of antibiotic resistance in invasive strains. Prevalence of resistance to various antimicrobial drugs among S. pneumoniae and H. influenzae was estimated.

Medical significance and management of staphylococcal biofilm

Biofilm is one of the important virulence factors of staphylococci that plays a role in many device-related infections such as native valve endocarditis, otitis media, urinary tract infections, cystic fibrosis, acute septic arthritis, etc. Biofilm is a microbially derived sessile community of microorganisms, developed either from single or multiple microorganisms. Formation of biofilm is a two-step process: adherence of cells to a surface and accumulation of cells to form multilayered cell clusters. A trademark of biofilm formation in staphylococci is the production of polysaccharide intercellular adhesin. In the formation and regulation of biofilm, some biosynthetic genes (icaADBC) and some regulatory genes (icaR, sar, agr, rbf, sigma(B)) are involved. In this article, we reviewed the structure and formation of staphylococcal biofilm and its role in medical infections.

Dengue in infants: an overview

Abstract Dengue virus (DV) infection causes either a benign syndrome, dengue fever, or a severe syndrome, dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS), that is characterized by systemic capillary leakage, thrombocytopaenia and hypovolaemic shock. DHF/DSS occur mainly due to secondary infection by a heterotype DV infection in children and adults but in infants even primary infection by DV causes DHF/DSS. Clinical manifestations of DHF/DSS are more significantly associated with death in infants compared with older children. Vertical transmission of DV and anti-DV IgG has been well reported and is responsible for the pathogenesis of DV disease and its manifestations in infants. The complex pathogenesis of DHF/DSS during primary dengue in infants, with multiple age-related confounding factors, offers unique challenges to investigators. Dengue in infants is not often studied in detail due to practical limitations, but looking at the magnitude of DHF/DSS in infants and the unique opportunities this model provides, there is a need to focus on this problem. This paper reviews existing knowledge on this aspect of DV infection and the challenges it provides.

Dynamics of influenza seasonality at sub-regional levels in India and implications for vaccination timing.

Background Influenza surveillance is an important tool to identify emerging/reemerging strains, and defining seasonality. We describe the distinct patterns of circulating strains of the virus in different areas in India from 2009 to 2013. Methods Patients in ten cities presenting with influenza like illness in out-patient departments of dispensaries/hospitals and hospitalized patients with severe acute respiratory infections were enrolled. Nasopharangeal swabs were tested for influenza viruses by real-time RT-PCR, and subtyping; antigenic and genetic analysis were carried out using standard assays. Results Of the 44,127 ILI/SARI cases, 6,193 (14.0%) were positive for influenza virus. Peaks of influenza were observed during July-September coinciding with monsoon in cities Delhi and Lucknow (north), Pune (west), Allaphuza (southwest), Nagpur (central), Kolkata (east) and Dibrugarh (northeast), whereas Chennai and Vellore (southeast) revealed peaks in October-November, coinciding with the monsoon months in these cities. In Srinagar (Northern most city at 34°N latitude) influenza circulation peaked in January-March in winter months. The patterns of circulating strains varied over the years: whereas A/H1N1pdm09 and type B co-circulated in 2009 and 2010, H3N2 was the predominant circulating strain in 2011, followed by circulation of A/H1N1pdm09 and influenza B in 2012 and return of A/H3N2 in 2013. Antigenic analysis revealed that most circulating viruses were close to vaccine selected viral strains. Conclusions Our data shows that India, though physically located in northern hemisphere, has distinct seasonality that might be related to latitude and environmental factors. While cities with temperate seasonality will benefit from vaccination in September-October, cities with peaks in the monsoon season in July-September will benefit from vaccination in April-May. Continued surveillance is critical to understand regional differences in influenza seasonality at regional and sub-regional level, especially in countries with large latitude span.

Evaluation of nitrate reduction assay, resazurin microtiter assay and microscopic observation drug susceptibility assay for first line antitubercular drug susceptibility testing of clinical isolates of M. tuberculosis.

BACKGROUND Drug resistant tuberculosis (TB) is a growing concern worldwide. Early detection of multidrug-resistant Mycobacterium tuberculosis is of primary importance for both patient management and infection control. Optimal method for identifying drug-resistant M. tuberculosis in a timely and affordable way in resource-limited settings is not yet available. AIM This study evaluated; nitrate reductase assay (NRA), resazurin microtiter assay (REMA) and microscopic observation drug susceptibility assay (MODS) against the conventional 1% proportion method (PM) for the detection of resistance to first line antitubercular drugs, in M. tuberculosis clinical isolates. METHODS A total of one hundred and five clinical isolates of M. tuberculosis; 50 pan sensitive and 55 pan resistant were tested with NRA, REMA and MODS. The 1% proportion method on Lowenstein-Jensen medium was used as reference test. RESULTS Of all three methods which were tested NRA was found to be most sensitive and specific. Sensitivity for rifampicin resistance detection was 100%, 94.55% and 92.73% by NRA, REMA and MODS respectively. NRA and REMA were found to be 100% specific, while the MODS was 98% specific for detection of rifampicin resistance. Test results with all these methods were obtained within 8-14 days. CONCLUSION Rapid non-conventional and inexpensive methods may serve as a replacement for 1% proportion method in resource limited settings.

Cefoxitin disc diffusion test for detection of meticillin-resistant staphylococci

Staphylococci are the main causative agents of nosocomial diseases. Over the last few years, the increase in the number of meticillin-resistant (MR) staphylococci has become a major clinical problem. Accuracy and promptness in the detection of meticillin resistance are of key importance in ensuring the correct antibiotic treatment in infected patients and control of MR staphylococci in the hospital environment. This study evaluated the accuracy of a cefoxitin disc diffusion (DD) test for the detection of meticillin resistance in staphylococci. A total of 144 clinical isolates [97 Staphylococcus aureus and 47 coagulase-negative staphylococci (CoNS)] were tested using a mecA gene PCR, a DD test (oxacillin, 1 mug disc; cefoxitin, 30 mug disc), determination of oxacillin MIC by agar dilution (AD), and an oxacillin screen agar test at oxacillin concentrations of 4 and 6 mug ml(-1). Of the 97 S. aureus and 47 CoNS isolates, 73 (75.26 %) and 30 (63.83 %), respectively, were mecA-positive. The sensitivity and specificity of the cefoxitin DD test were 94.44 and 95.83 %, respectively, for S. aureus and 80 and 100 %, respectively, for CoNS. The oxacillin DD method was 100 % sensitive and 58.33 % specific for S. aureus, and 86.67 % sensitive and 70.59 % specific for CoNS. The AD test was highly sensitive (98.63 %) and specific (98.53 %) for S. aureus and CoNS (83.33 % sensitive and 94.12 % specific). The cefoxitin DD test for meticillin-resistance detection was more specific but less sensitive than the oxacillin DD test. Use of DD tests for both cefoxitin and oxacillin can help in more accurate prediction of meticillin resistance. Centres that are not equipped to carry out PCR can use AD methods for confirmation of meticillin resistance, especially in oxacillin-resistant and cefoxitin-sensitive cases.