Detection of bacterial adherence and biofilm formation on medical surfaces
M. Loza-Correa, S. Ramlrez-Arcos
Centre for Innovation, Canadian Blood Services, Ottawa, Ontario, Canada
Biofilm formation is an important survival strategy that bacteria utilize in natural and human-made niches. The detection of adherence of pathogenic bacteria on medical surfaces is necessary to identify and prevent systemic infections related to biofilm-forming bacteria. The wide range of surfaces that bacteria can attach to and grow on includes indwelling medical devices and living tissues such as skin, bone or vascular grafts, and dental and ossicular prostheses. Biofilms were first associated with medical device infections in 1972 giving origin to the term “polymeric-associated infections” (Percival et al., 2015). The ability of bacteria to colonize medical surfaces indicates a significant risk of microbial dissemination within the patient and increases the risk of systemic infections. In public health settings, biofilms have become a significant concern. These structured bacterial communities embedded in an amorphous matrix display high resistance to environmental stresses, antibiotics (Hoiby et al., 2010), disinfectants (Taha et al., 2014) and the host immune system, causing chronic infections (Burmolle et al., 2010).
It is estimated that at least 50% of nosocomial infections are associated with medical devices (Harris and Richards, 2006; Richards et al., 1999; Vincent, 2003; Safdar et al., 2001). Medical device-related infections are much more severe in high-risk populations, such as neonates, the elderly, and patients in critical care, and can lead to longer hospital stays, prolonged disability, additional burden for health systems, and increase morbidity and mortality (Guggenbichler et al., 2011). Four categories of infections account for three-quarters of healthcare-associated infections (Percival et al., 2015; Safdar et al., 2001; Richards et al., 1999; Vincent, 2003; Collignon, 1994; Lorente et al., 2005): (1) surgical-site infection, (2) ventilator-associated pneumonia, (3) central line blood stream infections, and (4) catheter-associated urinary track. As bacteria attached to medical devices are a major risk factor in these types of infections, it is important to use sensitive, rapid, and accurate methods to identify the presence of surface-attached bacteria on medical devices in order to provide prompt diagnosis and treatment.
Bacteria attached to medical devices may originate from the environment, the skin of the patient and/or healthcare personnel (Percival et al., 2015; Fux et al., 2005). The predominant pathogen associated with device-associated infections is the Gram-positive bacterium Staphylococcus epidermidis, comprising about 80% of
Biofilms and Implantable Medical Devices. http://dx.doi.org/10.1016/B978-0-08-100382-4.00008-3
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reported cases (Percival et al., 2015; Wang et al., 2011; Paredes et al., 2014). This bacterium is a common commensal inhabitant of the human skin and mucosa, making it difficult to determine its clinical significance. Other Gram-positive bacteria commonly isolated from infected implanted devices are Staphylococcus aureus and Enterococcus faecalis. Gram-negative bacteria associated with infected devices include Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, and Pseudomonas aeruginosa (Percival et al., 2015; Donlan, 2001). Yeast, in particular Candida albicans, has also been implicated in device-associated infections (Percival et al., 2015). Importantly, since mid-1990s, the incidence of healthcare-associated infections has increased due to the appearance of multidrug-resistant microorganisms (Cosgrove, 2006). Methi- cillin-resistant Staphylococcus aureus is one of the bacteria causing a significant increase in mortality rates of bacteremic patients (Cosgrove et al., 2003, 2005). Other multidrug-resistant bacteria related with nosocomial infections (bacteremia, urinary tract infections, pneumonia, central venous catheter-associated infection, and posttransplant infections) include Enterococcus spp. and Clostridium difficile (Percival et al., 2015; Raad et al., 2005; Stone et al., 2003; Kyne et al., 2002; Safdar and Maki, 2002; Bui et al., 2014)-
Factors that influence bacterial adherence on the surface of medical devices include physical and chemical properties of the medical material, fluids to which the device is exposed, nutrient availability, and temperature (Percival et al., 2015; Donlan, 2001). Accurate diagnosis of nosocomial infections is essential for their proper management and successful treatment. Although there are routine microbiological testing techniques to diagnose nosocomial infections, there is not an ideal standard strategy available that provides information on the presence of biofilms in clinical settings (Percival et al., 2015). When an infectious process related with an indwelling medical device is identified, the best strategy to avoid complications and ensure a good outcome is to remove the infected device (Stewart, 2003) and then determine the infectious agent through different strategies, commonly using culture methods.