Increase of antibiotic resistance in pathogens has directly impacted healthcare industry. With only a few novel discoveries in the field of antibiotics since last two decades, often referred to as the discovery void, drug-resistance in pathogens has increased. Previously, infections that were easily treatable have now become fatal. Infections caused by antibiotic-resistant pathogens can occur anywhere, but, it is observed to take maximum effect in healthcare settings such as hospitals and nursing homes. The pathogens adhere to surfaces such as linens, counter tops, drapes monitory equipment, sanitary ware and so on. Adherence of pathogens such as bacteria, viruses and fungi on various surfaces leads to subsequent transmission to new hosts and significantly contributes towards their proliferation as they can stay dormant on surfaces for long periods of time, typically days. This is seen especially in case of antibiotic-resistant pathogens, causing a major threat to human health. Moreover, patients in hospitals are easily affected due to decreased immunity. According to a report by Center for Disease Control and Prevention (CDC), 1 out of every 20 hospital patients is affected by nosocomial infections subsequently resulting in 100000 deaths in the United States of America. Out of these, 23000 deaths on an average are attributed to drug-resistant pathogens such as methicillin resistant
Staphylococcus aureus and
vancomycin-resistant Enterococcus faecium. In addition to this, $9.8 billion are invested in treatment of such infections. The conventional routes of treatments are proving to be inconsequential and a major part of tackling such infections is use of antibiotics. But, with the increase in drug-resistant strains it is only a matter of time when all the treatment methods fail. Although several methods such as chemical disinfectants, ionizing radiation, ultra-violet treatments are used in addition to antibiotics but, they are not effective due to various reasons. Chemical disinfectants and ionizing radiation are not FDA approved. Moreover, radiation techniques are cost intensive and ultra-violet radiation is harmful to healthy cells. So, alternative techniques must be investigated that can be utilized to prevent the loss due to hospital acquired infections (HAIs). Consequently, alternative techniques for surface disinfection must be investigated for their application as preventive techniques instead of looking for a cure. One such method that has recently come into light in the last two decades is photodynamic therapy (PDT). Commercial photosensitizers (PSs) such as Photofrin and Protoporphyrin IX have been used in Photodynamic therapy (PDT) for treating initial stages of skin cancer, acne and psoriasis. It involves three components: a photosensitizer, a visible light source and cytotoxic singlet oxygen. Initially, the PS is applied to the area affected by the cancer cells. After the PS is absorbed into the cells, the target area is illuminated by red colored light, thus, activating the PS. Activated PS can exchange energy with oxygen that diffuses through the cells, converting it into singlet oxygen (
1O
2).
1O
2 being highly energetic readily reacts with various components in the cell, ultimately leading to cell death. The idea of this study is to incorporate such photosensitizers into polymeric matrices that can be applied as surfaces that provide non-specific preventive measures, rather than as specific cures.
In this study, 1% (w/w) photosensitizer of porphyrin class has been physically incorporated in an Olefinic Block Copolymer (OBC) by solvent casting. Subsequently, the solvent was evaporated and the resulting cake was melt-pressed into films. Inactivation studies were performed on five bacterial strains (Gram-positive -Staphylococcus aureus and vancomycin-resistant Enterococcus faecium at 65 ± 5 mW/cm2; Gram-negative - Acinetobacter baumannii, Klebsiella pneumoniae and Escheria coli at 80 ± 5 mW/cm2). Furthermore, time based illumination studies were conducted at various illumination intensities with Staphylococcus aureus (5 - 80 mW/cm2, 5 – 60 min illumination time). Both the gram-positive bacteria showed ~ 6 log units reduction (~ 99.9999% killing) at the end of 60 minutes whereas all the three gram-negative bacteria showed at least ~3 log units reduction (~ 99.9% killing). Antiviral efficacy of films was determined against Vesicular stomatitis virus (VSV) (~ 99.9998 % inactivation) and Human adenovirus-5 (~ 99.9596 % inactivation).
