Astha Agarwal

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.

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.

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.

Effect of green tea extract (catechins) in reducing oxidative stress seen in patients of pulmonary tuberculosis on DOTS Cat I regimen.

BACKGROUND AND AIM The role played by free radicals in pathogenesis of pulmonary tuberculosis and treatment mediated toxicity is well established. Hence, the present study was undertaken to assess the effect of crude green tea catechin in reducing the oxidative stress seen in patients of AFB positive pulmonary tuberculosis. METHODS A total of 200 newly diagnosed cases of AFB positive pulmonary tuberculosis, who received CAT I regimen were enrolled consecutively from DOTS center. Out of 200 patients, 100 randomly selected patients received catechin (500 microg) with antitubercular treatment (ATT) (cases) and 100 received starch (500 microg) with ATT (control). Oxidative stress level in blood samples of cases and controls as compared at the time of enrollment and after one and four months of treatment. Oxidative stress was measured in terms of free radicals (lipid peroxidation, nitric oxide), enzymatic antioxidant (catalase, superoxide dismutase, glutathione peroxidase) and non enzymatic antioxidant (total thiol, reduced glutathione) levels. RESULTS The results showed significant difference in all the parameters among cases and controls. A significant decrease (p< or = 0.001) in LPO level was observed in cases as compare to controls during the follow up while the level of NO was significantly increased (p< or =0.001) in cases as compare to controls. Significant decrease (p< or =0.001) in catalase and GPx level was observed in cases as compare to controls while SOD levels significantly rose (p< or =0.001) in cases as compared to controls. Significant decrease (p< or =0.001) in SH level was observed in cases as compared to controls while the level of GSH was significantly increased (p< or =0.001) . CONCLUSION These findings suggest that crude catechin extract can play a definite role as adjuvant therapy in management of oxidative stress seen in pulmonary tuberculosis patients. More detailed studies are needed to document use of catechin in reducing the frequency and severity of side effects of treatment.

Randomized controlled trial of topical EMLA and vapocoolant spray for reducing pain during wDPT vaccination

BackgroundIntramuscular vaccination is among the most common source of iatrogenic pain in infants. Vapocoolant sprays are rapid-acting alternative to topical anesthetics. They provide transient anesthesia via evaporation induced skin cooling, and reduce pain due to vaccine injection in children and adults. The objective was to compare the synergistic analgesic effect of eutectic mixture of local anesthetics (EMLA) with breastfeeding (EB group) and vapocoolant spay with breastfeeding (VB group) to that of only breastfeeding (BO group) during whole cell diptheria, pertussis and tetanus (wDPT) vaccination.MethodsA double blind randomized controlled trial was done to include infants up to 3 months of age who came for their first wDPT vaccination. The primary outcome variable was the duration of cry after vaccination. Secondary outcome variables were Modified Facial Coding Score, Neonatal Infant Pain Scale and latency of onset of cry.ResultsOf the 201 eligible participants, 111 babies were excluded and remaining 90 babies were randomized into three groups of thirty each. The groups did not differ significantly in baseline characteristics. Median (interquartile range, IQR) of duration of cry was lesser [35.86 (21.07-107.75) seconds] in babies receiving EMLA cream with breast feeding (EB group) and in babies receiving vapocoolant spray with breast feeding (VB group) [32.58 (21.25-106.21) seconds] as compared to babies receiving only breast feeding (BO group) [67.5 (27.6-180) seconds] (P=0.147). Difference in median (IQR) of latency of cry was not statistically significant. Modified Facial Coding Score and Neonatal Infant Pain Scale at 1 minute and 3 minutes was significantly lower in the EB and VB group, as compared to the BO group (P<0.05).ConclusionAddition of topical EMLA application or vapocoolant spray to breastfeeding during wDPT vaccination does not reduce duration of cry in infants up to 3 months of age. However, they are able to show reduction in pain score and further studies are warranted to assess their efficacy as pain relief measures in infants and children.