Detection and Characterization of Staphylococcal Pathogens in the Environment: A Community Approach
Under conditions of compromised immunity, certain pathogenic strains of staphylococci can cause severe infections in humans and animals. Of the ca. 31 species of staphylococci currently recognized, 15 are potentially pathogenic to humans. Resistance to a variety of antibiotics has given certain members of the staphylococci a prominent place among emerging and re-emerging pathogens. Staphylococcus spp are ubiquitously distributed in a variety of hosts, multiple routes of transmission between hosts and between hosts and their environment have contributed to the spread of staphylococci beyond the boundaries of health care facilities and into the community.
Environmental and community reservoirs (e.g. shared surfaces and natural environment) of staphylococci, including S. aureus and coagulase-negative staphylococci CNS, have not been thoroughly identified. Furthermore, studies related to the contamination of surfaces (clinical or environmental) with staphylococci have historically focused on one or several species that were considered clinically important (e.g. methicillin-resistant S. aureus, MRSA).
To address this void in our knowledge of an important group of potentially pathogenic bacteria, research was designed to:
i- identify public surfaces that harbor antibiotic-resistant bacteria communities, including several members of the staphylococci,
ii- show that mecA (an important genetic determinate that confers resistance to several popular, therapeutic antibiotics) is widely distributed in nonstaphylococcal pathogens inhabiting a secondary environment, and;
iii- demonstrate a newly developed methodology that allows the simultaneous detection and species identification of most of the clinically important staphylococci, and apply the method to investigate the contamination of clinical surfaces with staphylococci.
In the first study, multiplex-PCR techniques were developed to detect and identify staphylococci, including methicillin-resistant staphylococci, on computer keyboard surfaces used by students and staff in a metropolitan university. The results of this study showed that computer keyboards were reservoirs for clinically important staphylococci, including methicillin-resistant S. aureus (MRSA), methicillin-resistant S. epidermidis (MRSE) and S. hominis (MRSH). Consequently, this study identified public computer keyboards and similar tactile surfaces that are ubiquitous not only in the community but also in the healthcare facilities as an important reservoir for staphylococci and potential source of infection. Additionally, evidence was provided to warrant further studies to identify contaminated surfaces in the community.
In the second study, fresh recreational waters that were impacted by fecal pollution and consequently important in spreading infections in swimmers were investigated for the presence of staphylococci. The role of fresh water as a potential reservoir was not previously investigated. While antibiotic-resistant staphylococci were not isolated from the fresh water tested in this study, other antibiotic-resistant bacteria were isolated, including P. vulgaris, M. morganii, and E. faecalis all of which are known human pathogens. These pathogens were multi-antibiotic resistant and carried mecA, a gene conferring resistance to a wide range of ß-lactam antibiotics, which was previously associated only with staphylococci. The results of this study showed that mecA is widespread in the environment than previously thought (previous studies associated a mecA homologue to naturally occurring non-aureus staphylococci). The isolation of bacteria that were resistant to multiple clinically important antibiotics, including vancomycin and methicillin, and carried the mecA from a secondary environment was of particular significance, as these species (especially E. faecalis) are more commonly associated with a clinical environment.
In the third study, a community fingerprinting method (DGGE) was customized to allow the specific and sensitive detection and characterization of assemblages of Staphylococcus species that contaminated surfaces in the clinical environment. DGGE analysis showed that most surfaces in an isolation room housing a patient were contaminated with single or multiple species of clinically important staphylococci, including S. aureus, S. epidermidis, S. simulans, S. hominis, and S. lugdunesis. DGGE analysis was not only successful in detecting the contaminating species, but also highlighted the prevalence and identity of these species in the clinical environment. Furthermore, DGGE analysis showed that daily room cleaning procedures were not sufficient to eradicate all staphylococci. This is an important finding, as now healthcare staff have a tool with which they can assess prevalence of contamination in their facilities and the efficiency of contamination management, allowing for a healthier patient environment.
Finally, this thesis represented studies concerned with i- aspects of public health microbiology, ii- attempts to develop methodologies to identify pathogen reservoirs in environmental and clinical matrices, and iii- achieving a better understanding of contamination with staphylococci. The methods and findings reported in this thesis can be used to further expand future studies of contamination with staphylococci in both environmental and clinical settings.
School:University of Toledo
School Location:USA - Ohio
Source Type:Doctoral Dissertation
Embargo Type:Entire Document
Keywords:staphylococcus spp mrsa meca clinical surfaces environment dgge
Date of Publication:06/16/2009