Prasanta Kumar Maiti

EVALUATION OF THE ROLE OF SUBSTRATE AND ALBUMIN ON PSEUDOMONAS AERUGINOSA BIOFILM MORPHOLOGY THROUGH FESEM AND FTIR STUDIES ON POLYMERIC BIOMATERIALS

Bacterial biofilms pose the greatest challenge to implant surgeries leading to device-related infections and implant failure. Our present study aims at monitoring the variation in the biofilm architecture of a clinically isolated strain and ATCC 27853 strain of Pseudomonas aeruginosa on two polymeric biomaterials, used in implants. The perspective of our study is to recognize the potential of these two biomaterials to create biofilm infections and develop the understanding regarding their limitations of use and handle patients with this deeper insight. The final goal, however, is an accurate interpretation of substrate-microbe interactions in the two biomaterials, which will provide us the knowledge of possible surface modifications to develop of an efficacious anti-biofilm therapy for deterring implant infections. The reference strain ATCC 27853 and a clinical isolate of P. aeruginosa collected from urinary catheters of patients suffering from urinary tract infections, have been used as microbes while clinical grades of polypropylene and high density polyethylene, have been used as ‘substrates’ for biofilm growth. The variation in the nature of the ‘substrate’ and ‘conditioning layer’ of BSA have been found to affect the biofilm architecture as well as the physiology of the biofilm-forming bacteria, accompanied by an alteration in the nature and volume of EPS (extracellular polysaccharide) matrices.Graphical Abstract

Comparative evaluation of loop-mediated isothermal amplification and conventional methods to diagnose extrapulmonary tuberculosis

Background: Extra-pulmonary tuberculosis is difficult to diagnose by conventional methods, because they are less sensitive and more time consuming. Loop-mediated Isothermal Amplification (LAMP) is a novel gene amplification method that has been developed to diagnose Mycobacterium tuberculosis complex in pulmonary and paucibacillary extrapulmonary specimens even in resource poor settings. Aims and Objectives: To evaluate the sensitivity and specificity of LAMP to detect Mycobacterium tuberculosis complex in paucibacillary extra-pulmonary specimens and to compare the results with other conventional methods in extrapulmonary specimens. Materials and Methods: 45 specimens from suspected extrapulmonary tuberculosis patients were collected and tested by LAMP method after DNA extraction. Simultaneously, these specimens were tested by smear microscopy, solid and liquid culture methods. Culture positivity, either in solid or liquid culture, was considered as a confirmed case of extrapulmonary tuberculosis. Results: Sensitivity of LAMP was 95.6% whereas for liquid culture, solid culture and smear microscopy were 69.6%, 65.2% and 17.4% respectively. Specificity for LAMP was 95.4% and for other 3 conventional methods were 100%. Positive predictive values, negative predictive values and likelihood ratios were also evaluated. Turn-around time (TAT) for LAMP was 8 hours only whereas for liquid culture was 2-4 weeks, and for solid culture it was 4-8 weeks. Conclusion: LAMP was a simple, rapid and cost-effective procedure with good sensitivity and specificity. It was found to be better than conventional methods to diagnose extrapulmonary tuberculosis.

Does the Benefit of Salvage Amputation Always Outweigh Disability in Drug­ Failure Mycetoma?: A Tale of Two Cases

It is popularly believed that eumycetoma cases should be dealt with using surgical amputation for a better chance of cure especially when chemotherapy has failed. However, amputation leads to disability on one hand and on the other it may also fail to be curative. We present two cases with contrasting treatment options and outcome. In the eumycetoma case reported here, a 40-year-old male presented with right foot swelling for 16 years, from which Scedosporium apiospermum was isolated. He responded poorly to antifungal therapy and refused below-knee amputation 12 years ago. With counseling and wound care his condition improved, and Foot and Ankle Ability Measure (FAAM) score remained almost stable at 90% for 16 years, which is much better than the average functional outcome after amputation. Another 46-year-old female underwent below-knee amputation after receiving incomplete courses of antibiotics and antifungals for mycetoma of unknown etiology. She presented to us after recurrence of mycetoma on an amputated stump and was successfully treated by proper courses of antibiotics after detecting the causal agent, Actinomadura madurae. Her post-amputation disability and depression could have been avoided if the hasty decision of amputation had not been taken. In our opinion, living with drug-non-responsive mycetoma, supported by symptomatic management, may be a better option than amputation and its associated morbidities. So before taking the path of salvage amputation, we must consider many aspects, including patients livelihood, psychological aspects and chances of recurrence even after the procedure.

An unusual case of chronic nonhealing periorbital ulceration due to a new species of Corynebacterium sp. strain UCL557

Nondiphtherial Corynebacterium (diphtheroids) has been related to blood and wound infections but are an uncommon cause for soft tissue infection. We report a case of periorbital soft tissue infection with ulceration caused by multidrug-resistant Corynebacterium spp. in a 9-year-old girl who is apparently immunocompetant. Computed tomography scan showed soft tissue involvement of right periorbital region with no bony destructions or focal calcifications. Vision remained unaffected. Patient was treated by debridement and skin grafting, but condition did not improve. Pus collected from the periorbital ulcerated area was cultured in blood agar and Corynebacterium spp. was isolated from the pure culture, which was identified as a new species Corynebacterium sp. strain UCL557 using 16S rDNA- based molecular technique based on nucleotide homology and phylogenetic analysis. Antibiogram showed multiresistance pattern with sensitivity to ceftriaxone-sulbactum vancomycin and linezolid. After initiation of treatment with vancomycin infusion and oral linezolid, the patient responded well and lesion started to heal. To the best of our knowledge, this is the first ever case report of periorbital ulceration by new species of Corynebacterium sp. strain UCL557.

Rethink on recommended concentrations of disinfectants in the light of biofilm, based on in vitro study

Background: Some medical devices are reused after treatment with disinfectants at manufacturer′s recommended concentrations (RCs), based on experimental evaluation studies of their bactericidal, sporicidal, and mycobactericidal concentrations. However, this may not be sufficient to eliminate all colonized highly drug-resistant biofilms on medical devices, resulting possibility in iatrogenic infections by recolonization of highly resistant persisters. The objective of this study is to evaluate the antibacterial efficacy of different concentrations of novel and conventional disinfectants on in vitro grown biofilm of multidrug-resistant nosocomial bacterial isolates and a reference strain. Materials and Methods: Multidrug-resistant and strong biofilm producers Pseudomonas aeruginosa (n = 4) and Escherichia coli (n = 5) nosocomial isolates and one reference strain, P. aeruginosa PAO-1, were selected after testing their biofilm status by modified Christensen′s method and Stepanovic′s interpretative criteria. The activity of three different groups of new disinfectants, Novacide, Virkon, Silvicide and two conventional disinfectants, phenol and glutaraldehyde, were assessed on their in vitro grown biofilms as percentage of total surviving bacteria within biofilm matrix after challenge at different concentrations in terms of multiples of RC and different contact time. Results: Modified RCs for Virkon, phenol, and Silvicide, as pointed out by in vitro study, were 4, 8, and 10 times higher than the one suggested by the manufacturer. Novacide was least effective, whereas glutaraldehyde at its available concentration was also not effective in removal of biofilm bioburden. Conclusions: RC was not sufficient to eliminate the in vitro biofilms tested in this study. Further studies using medical devices materials should be performed for clarification. However, this study points out possible relevant limitations of currently used hospital disinfectants and concentrations against biofilms. Additional measures to prevent reinfections related to their use of medical devices are mandatory, and this study suggests that optimization of disinfectants concentrations may be highly relevant.