V. Anil Kumar

Antibiotic resistance in Pseudomonas aeruginosa and alternative therapeutic options

Pseudomonas aeruginosa is a leading cause of nosocomial infections and is responsible for ∼10% of all hospital-acquired infections worldwide. It continues to pose a therapeutic challenge because of the high rate of morbidity and mortality associated with it and the possibility of development of drug resistance during therapy. Standard antibiotic regimes against P. aeruginosa are increasingly becoming ineffective due to the rise in drug resistance. With the scope for developing new antibiotics being limited, alternative treatment options are gaining more and more attention. A number of recent studies reported complementary and alternative treatment options to combat P. aeruginosa infections. Quorum sensing inhibitors, phages, probiotics, anti-microbial peptides, vaccine antigens and antimicrobial nanoparticles have the potential to act against drug resistant strains. Unfortunately, most studies considering alternative treatment options are still confined in the pre-clinical stages, although some of these findings have tremendous potential to be turned into valuable therapeutics. This review is intended to raise awareness of several novel approaches that can be considered further for combating drug resistant P. aeruginosa infections.

Detection of Oxacillin-Susceptible mecA-Positive Staphylococcus aureus Isolates by Use of Chromogenic Medium MRSA ID

ABSTRACT Reports of oxacillin-susceptible mecA-positive Staphylococcus aureus strains are on the rise. Because of their susceptibility to oxacillin and cefoxitin, it is very difficult to detect them by using routine phenotypic methods. We describe two such isolates that were detected by chromogenic medium and confirmed by characterization of the mecA gene element.

Comparative efficacy of chloramphenicol loaded chondroitin sulfate and dextran sulfate nanoparticles to treat intracellular Salmonella infections

Salmonella Paratyphi A is a food-borne Gram-negative pathogen and a major public health challenge in the developing world. Upon reaching the intestine, S. Paratyphi A penetrates the intestinal epithelial barrier; and infects phagocytes such as macrophages and dendritic cells. S. Paratyphi A surviving within macrophages is protected from the lethal action of antibiotics due to their poor penetration into the intracellular compartments. Hence we have developed chloramphenicol loaded chondroitin sulfate (CS-Cm Nps) and dextran sulfate (DS-Cm Nps) nanoparticles through ionotropic-gelation method for the intracellular delivery of chloramphenicol. The size of these nanoparticles ranged between 100 and 200 nm in diameter. The encapsulation efficiency of both the nanoparticles was found to be around 65%. Both the nanoparticles are found to be non-hemolytic and non-toxic to fibroblast and epithelial cells. The prepared nanoparticles exhibited sustained release of the drug of up to 40% at pH 5 and 20-25% at pH 7.0 after 168 h. The anti-microbial activities of both nanoparticles were tested under in vitro and ex vivo conditions. The delivery of DS-Cm Nps into the intracellular compartments of the macrophages was 4 fold more compared to the CS-Cm Nps which lead to the enhanced intracellular antimicrobial activity of Ds-Cm Nps. Enhanced anti-microbial activity of Ds-Cm Nps was further confirmed in an ex vivo chicken intestine infection model. Our results showed that Cm loaded DS Nps can be used to treat intracellular Salmonella infections.

Clinical Profile of Patients Admitted with Swine-Origin Influenza A (H1N1) Virus Infection: An Experience from A Tertiary Care Hospital.

BACKGROUND Pandemic influenza A (H1N1) 2009 has posed a serious public health challenge world-wide. H1N1 critical illness mostly affects young patients and is often fatal. OBJECTIVE Primary objective was to study clinical profile of the patients admitted with confirmed H1N1 swine flu infection. Secondary objective was to observe the risk factors associated with complications like need of mechanical ventilation and or death among H1N1 infected patients. MATERIAL AND METHODS A prospective observational study was conducted in a tertiary care teaching hospital from June 2009, to December, 2011. H1N1 infection was confirmed by reverse transcriptase PCR. Statistical analysis was done by SPSS, version 11. Binary logistic regression was used to find out independent risk factors for morbidity. RESULTS Total 495 patients were tested for H1N1 infection. Among them, 115 (23%) were positive and 88(76%) required admission. Median age of cohort was 29 years and 87% of the patients were below 54 years of age. Most common presenting symptoms were fever (98%), followed by cough (86%) and sore throat (54%). Out of 88 patients, 14 (16%) required mechanical ventilation and 6(6.8%) died. Lymphopaenia (Lymphocytes <10%) and presence of patchy infiltrates on chest X-ray (CXR) the time of presentation were independent risk factors associated with need of mechanical ventilation or death in H1N1 infected patients by multivariate analysis. CONCLUSION Present study showed that H1N1 swine flu mainly affected people who were < 54 years of age. Majority of patients improved with antiviral treatment. Lymphopaenia and CXR which showed bilateral pneumonia at time of presentation were found to be independent risk factors associated with requirement of mechanical ventilation and/or death in H1N1 infection. Pregnant females with flu constituted 33% of total mortality. High priority should be given to such patients. Further community based studies are required to analyze the actual impact of H1N1 infection in the community.

Risk factors for mortality in Acinetobacter calcoaceticus-baumannii bacteraemia

Article history: Objective: To determine the risk factors associated with mortality in Acinetobacter calcoaceticus- baumannii (Acb) complex blood stream infection. Methods: This was an observational study conducted in tertiary care hospital of South India. All patients with blood culture positive for Acb complex from January 2008 to December 2009 were included and a standardized abstraction form was used to abstract data. P value was calculated by Chi square test. Univariate analysis was done by using 2x2 tables and the variables with P value of <0.1 were further subjected to multivariate analysis. Multivariate analysis was done by logistic regression method. Results: After excluding the polymicrobial infections and duplicate isolates from the same patients, 81 cases were included in our study. Out of 81 patients, 20 (24.6%) patients had positive isolate from body secretion other than blood for Acb complex, majority were hospitalized in intensive care unit (74%), had indwelling vascular catheters (68%) and were mechanically ventilated (61%). Multi drug resistant phenotypes were seen in 56 (69.1%) isolates and among them 13 (16%) were resistant to carbapenems. Univariate analysis showed renal disease, diabetes mellitus, use of mechanical ventilation and absence of appropriate antibiotic therapy, leucopenia, thrombocytopenia and raised prothrombin time were related to increased mortality in Acb complex bacteraemia. However, in multivariate analysis independent risk factors for mortality in Acb complex bacteraemia were platelets of less than 1.5 lacks and inappropriate empirical antibiotics. Conclusions: Thrombocytopenia and absence of appropriate antibiotics were risk factors associated with mortality in Acb bacteraemia. Patients with blood culture showing Acb complex bacteraemia with above findings should be attended with aggressive management. Clinician of hospitals with high incidence of Acb complex bacteraemia, should predict the chances of such infection even prior to blood culture reports are available, and should initiate appropriate antibiotics according to their institution antibiogram.

Preparation, Characterization and Efficacy of Lysostaphin-chitosan Gel Against Staphylococcus Aureus

Lysostaphin (LST) is a bacteriocin that cleaves within the pentaglycine cross bridge of Staphylococcus aureus peptidoglycan. Previous studies have reported the high efficiency of LST even against multi drug resistant S. aureus including methicillin resistant S. aureus (MRSA). In this study, we have developed a new chitosan based hydrogel formulation of LST to exploit its anti-staphylococcal activity. The atomic interactions of LST with chitosan were studied by molecular docking studies. The rheology and the antibacterial properties of the developed LSTC gel were evaluated. The developed LST containing chitosan hydrogel (LSTC gel) was flexible, flows smoothly and remains stable at physiological temperature. The in vitro studies by agar well diffusion and ex vivo studies in porcine skin model exhibited a reduction in S. aureus survival by ∼3 Log10CFU/mL in the presence of LSTC gel. The cytocompatibility of the gel was tested in vitro using macrophage RAW 264.7 cell line and in vivo in Drosophila melanogaster. A gradual disruption of S. aureus biofilms with the increase of LST concentrations in the LSTC gel was observed which was confirmed by SEM analysis. We conclude that LSTC gel could be highly effectual and advantageous over antibiotics in treating staphylococcal-topical and biofilm infections.

Impregnation of Catheters with Anacardic Acid from Cashew Nut Shell Prevents Staphylococcus aureus Biofilm Development.

The effect of anacardic acid impregnation on catheter surfaces for the prevention of Staphylococcus aureus attachments and biofilm formations were evaluated.

Salmonella Typhimurium pneumonia in a patient with multiple myeloma.

Pneumonia due to non-typhoidal Salmonella is a rarely reported entity. A fatal case of Salmonella pneumonia is reported here where Salmonella Typhimurium was isolated from the endotracheal aspirate and blood culture.

Defining multidrug resistance in Gram-negative bacilli

Sir, We read with interest the article by Shenoy and colleagues1 on blandm-1 gene in multidrug resistant (MDR) Gram-negative bacilli. In a country with 60-80 per cent prevalence of extended spectrum beta-lactamase (ESBL) among hospital Gram-negative isolates with co-resistance to other classes of antimicrobials as high as 44 per cent to co-trimoxazole, 76 per cent to gentamicin, 88 per cent to tetracycline and 90 per cent to fluoroquinolones, the authors’ report of only 1.48 per cent MDR Gram-negative bacilli in a tertiary care centre is surprising2,3. There are certain points which need to be clarified: The definition of MDR is very vague and without any reference in the article1. MDR, in literal terms means ‘resistant to more than one antimicrobial agent’, but a standardized definition for MDR has not yet been agreed upon by the medical community. There are many definitions that are currently being used to characterize patterns. The most practical definition used for Gram-positive and Gram-negative bacteria is ‘resistant to three or more antimicrobial classes’4. Selecting Gram-negative isolates resistant to 1st and 2nd line antibiotics by standard disk diffusion test was very difficult as isolates were from different sites which had different antibiotics in their 1st and 2nd line of treatment. It is important for the authors to clearly define their criteria for MDR Gram-negative isolates as they have reported a low percentage of MDR Gram-negative isolates, and also that 93.24 per cent of these were phenotypically MBL producers, which is very alarming. The authors did not define how the carbapenamase producers were initially screened. Only imipenem (IPM) was tested by disk diffusion method. So how did the authors determine “variable carbapenem resistance”?. It will be interesting to see what type of variable carbapenem resistance was seen. They also need to mention all the carbapenems tested in their study and their MIC (minimum inhibitory concentration) at least as generated by Vitek 2 Compact 60. What the authors have described in the Material & Methods section is combined-disk test, not the double disk synergy test (DDST). In the DDST, an IPM (10 µg) disk is placed 20 mm (center to center) from a blank disk containing 10 µl of 0.1 M (292 µg) EDTA. Enhancement of the zone of inhibition in the area between the two disks is considered positive for an MBL5. Table II: Denominators used for calculating percentages are misleading, e.g: while the table may be interpreted as 5.7 per cent of isolates of Acinetobacter baumannii were blandm-1 positive; the actual percentage is 20 per cent. The authors mentioned that 14.7 per cent of Escherichia coli isolates were NDM-1 positive in their study but the Table showed that 50 per cent (5/10) of the MDR E.coli were NDM-1 positive. We are unable to understand what the authors wish to convey through the current percentages in Table II? What does 115.38 per cent of tracheal aspirate mean; as well as 105 per cent of total isolates? Tigecycline resistant isolates need to be identified as Pseudomonas, Providencia and Burkholderia isolates are known to have higher MICs for tigecycline6.

MDP bone scan in the early identification of polyarticular aspergillosis

Figure 1. (A) 20 millicurie of Tc-MDP was injected intravenously and 3 h later whole body anterior and posterior images were acquired on a dual-head variable-angle gamma camera. Images show hot spots in the right sacroiliac, hip, and right knee joints (arrows). (B) Magnetic resonance image of the pelvis (T2-STIR: ‘short TI inversion recovery’ is an inversion recovery pulse sequence with specific timing so as to suppress the signal from fat, for better soft tissue visualization) was later done, and showed a hyper-intense signal in the right sacroiliac joint and hip joint with post-contrast enhancement.