Coliform Bacteria Essays - Enterobacteria, Bacteria,

Coliform Bacteria Coliform bacteria are good indicator organisms for the presence of pathogenic bacteria due to their realtionship with these pathogenic bacteria, their relative ease of determination by simple methods, and by their occurrence in large quantities in human feces. The MPN method used in this experiment is one of the prescribed techniques for the determination of these coliform bacteria from the Standard Methods for the Examination of Water and Wastewater as prescribed by the EPA. It consists of three stages, each of which necessitates a positive result for the previous stage. The first stage (presumptive test) determines the gas-producing coliform characteristic during lactose-fermentation. The second stage (confirmed test), determines the gram-reaction and also the lactose fermentation abilities of the organism, while the last stage (completed test) determines the endospore presence to determine if the organisms in the sample indeed are coliforms. The number of coliforms or bacteria present is readily seen with the use of a special table and then the statistically estimated numbers are determined. The samples, however, did not produce positive results for the presence of coliforms. Enventhough there was a large MPN value for one of the samples, about 1100 MPN per 100 ml, the sample still tested negative in the last stage. It is therefore suffice to say that the samples did not present any health risks for humans. Future researchers should, however, device or perform other more specific procedures due to the fact that there might have been still coliforms present but these may have been negated by possible endospore-forming relatives. Introduction Human health has always been a hard condition to preserve and the detection and control of pathogens in the environment have been the very key to the success of the human race. Although microbial pathogens are relatively few in comparison to the total number of microorganisms, their detection have been made easy with the use of indicator organisms. Indicator organisms give researchers the benefit of making good assumptions on the presence of pathogens before the pathogens multiply in distressing numbers. For a microbe to be accepted as an indicator organism, it must be present in human feces in large amounts so much so that the presence of these bacteria in a given sample would already point to human fecal contamination. It was reasoned that the largest amount of pathogens was present in human feces, and thus, the indication of the entry of large amounts of human waste, from healthy persons or not, already indicate a great risk (NCSU). Also, indicator organisms must be present wherever and whenever the pathogen organisms are present. More importantly, these indicator organisms must be easily detectable in samples and tests for the measurement of their numbers must be simple enough (Tortora et al. 1995). Coliform bacteria fit all the requirements and are even safe to handle in the laboratory. Coliform bacteria are gram-negative and non-spore/endospore forming bacteria, which include aerobes and facultative anaerobes, and when incubated at 35?C with lactose in the media, will evolve gas (CO2) within 48 hrs, like Escherichia, Klebsiella, Citrobacter and Enterobacter (NCSU). They are also prevalent in the colon and intestinal tract (but not all groups are present) of warm-blooded mammals, including man (Anderson et al. 1998). They are also related to pathogenic bacteria in that a large number of these coliform bacteria usually imply the presence of some pathogenic bacteria (Frank). These characteristics of coliform bacteria already suffice the conditions outlined for these organisms to be classified as indicator organisms. They occur in large amounts in human feces, in fact, humans excrete billions of these coliforms (called fecal coliforms). They are present whenever and wherever the pathogen organisms are present. More importantly, their presence is easily detected as their characteristics are easily tested with the use of simple procedures like gram-staining, endospore-staining and lactose fermentation tests. These principles and procedures now form the basis and the rationale for the methods by which this experiment was conducted. Actually, the use of coliform bacteria as indicators of the presence of pathogenic bacteria is not new already. It as been established since 1880, and because of their reliability as indicator organisms, the procedures have not changed much and have only geared on specifically measuring the amount of fecal coliforms by use of special growth media and techniques. Today, the basis of the Standard Methods for the Examination of Water and Wastewater that are being used (also in this experiment) have been specified by the Environmental Protection Agency (EPA) (NCSU). There are several methods prescribed by the EPA and although the Most Probable Number (MPN) method is not the most