Factors Affecting Microbial Growth The key to a productive staff is creating and maintaining a safe and healthy work environment. These laboratories are equipped with directional airflow, meaning that clean air is pulled through the laboratory from clean areas to potentially contaminated areas. C. respiratory masks Stronger antimicrobial agents are going to have a greater effect on microbes than agents that are more dilute. The operating room (OR) of the hospital is a special unit that requires a relatively clean environment. Compare effectiveness of moist heat (autoclaving, pasteurization) vs .dry heat. BSL-1 agents are those that generally do not cause infection in healthy human adults. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Feel free to learn more about bacteria with the lesson called Factors Influencing Success of Microbial Control. There are several factors which directly or indirectly influence the growth and development of an organism. Explain how radiation kills cells. D. completely eliminate a microbial population. In addition to the standard PPE already mentioned, laboratory personnel in BSL-3 laboratories must also wear a respirator and work with microbes and infectious agents in a biological safety cabinet at all times. According to the CDC, the BSL is determined by the agent’s infectivity, ease of transmission, and potential disease severity, as well as the type of work being done with the agent.1. Because of the serious nature of the infections caused by BSL-3 agents, laboratories working with them require restricted access. Nina Parker, (Shenandoah University), Mark Schneegurt (Wichita State University), Anh-Hue Thi Tu (Georgia Southwestern State University), Philip Lister (Central New Mexico Community College), and Brian M. Forster (Saint Joseph’s University) with many contributing authors. These are examples of biofilms—microorganisms embedded in thin layers of matrix material (Figure 1). Because C. botulinum can produce endospores that can survive harsh conditions, extreme temperatures and pressures must be used to eliminate the endospores. Microbial growth on meat products, as well as other foods, is affected, not only by the type and level of initial contamination but also by various factors associated with the product (intrinsic) or its environment (extrinsic). We'll also take a look at how the number and type of microorganisms present can affect microbial control. For example, higher temperatures and higher concentrations of disinfectants kill microbes more quickly and effectively. Several factors contribute to the effectiveness of a disinfecting agent or microbial control protocol. This air cannot be recirculated, so a constant supply of clean air is required. A shorter treatment time (measured in multiples of the D-value) is needed when starting with a smaller number of organisms. Death curves are often plotted as semilog plots just like microbial growth curves because the reduction in microorganisms is typically logarithmic (Figure \(\PageIndex{4}\)). pH: pH affects the ionic properties of bacterial cell so it affects the growth of bacteria. - Disinfectant - A chemical used to remove or destroy vegetative pathogens on inanimate objects. Have you ever tried to clean that scummy layer from your bathtub? Thus its migration kinetics is a controlling factor for the effective microbial … Any solution below pH 7 is considered acidic, and any pH above 7 is considered basic. Describe a practical application involving the use of UV light/radiation. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Sterilization can be accomplished through either physical means, such as exposure to high heat, pressure, or filtration through an appropriate filter, or by chemical means. Increased temperatures change the structure of biological molecules in a process called denaturation. The bacteria that grows in our showers and tubs are notoriously hard to clean. 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Population size of micrroorganisms (m.o). Factors such as temperature of storage, relative humidity, age of eggs, and level of surface contamination will influence internalization. Therefore, many antimicrobial treatments aim to change the pH of the surrounding environment, which like heat, disrupts the chemical structure of biological molecules in the organism. Visit the UExcel Microbiology: Study Guide & Test Prep page to learn more. More microorganisms make microbial control more difficult. Based on these symptoms, the physician diagnosed a urinary tract infection (UTI). Original content via Openstax (CC BY 4.0; Access for free at https://openstax.org/books/microbiology/pages/1-introduction). Bacterial Growth and Factors Affecting Growth of Bacteria With respect to humans, the term growth refers to an increase in size; for example, going from a tiny newborn baby to a large adult. In the 1800s, scientists began experimenting with a variety of chemicals for disinfection. Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. Pasteurization is a form of microbial control for food that uses heat but does not render the food sterile. Articles may be sterilized by either dry heat, applied hot air oven or by moist heat, provided by steam. Growth of bacterial cultures, growth curve and measurement of microbial growth; Influence of Environmental factors on microbial growth D. blood pressure cuffs. Ideally, disinfectants should be fast acting, stable, easy to prepare, inexpensive, and easy to use. ... Several factors contribute to the effectiveness of a disinfecting agent or microbial control protocol. Each curve has an optimal pH and extreme pH values at which growth is much reduced. Sterile fields are created according to protocols requiring the use of sterilized materials, such as packaging and drapings, and strict procedures for washing and application of sterilants. For example, invasive applications that require insertion into the human body require a much higher level of cleanliness than applications that do not. Intrinsic factors 2.1. Several factors contribute to the effectiveness of a disinfecting agent or microbial control protocol. Temperature. The method of choice depends on the material to be treated, the requirement for cell death vs. inhibition of growth, Number of microbes 2. Learning objectives. For example, low- and medium-acid foods are heated to 121 °C for a minimum of 2.52 minutes, which is the time it would take to reduce a population of 1012 endospores per can down to 1 endospore at this temperature. When choosing a microbial control protocol, factors to consider include the length of exposure time, the type of microbe targeted, its susceptibility to the protocol, the intensity of the treatment, the presence of organics that may interfere with the protocol, and the environmental conditions that may alter the effectiveness of the protocol. If wearing a suit, the air pressure within the suit must be higher than that outside the suit, so that if a leak in the suit occurs, laboratory air that may be contaminated cannot be drawn into the suit (Figure \(\PageIndex{1}\)). ... especially by Listeria monocytogenes, and the control of microbial growth, especially by modified-atmosphere ... Ahvenainen, R., Skyttä, E. and Kivikataja, R.-L. (1989) Factors affecting the shelf-life of gas- and … Anti-microbial constituents; Biological structure; 1. pH Value. How Long Does a Tax Lien Stay on Your Credit Report? Microbial control is all about limiting the growth of unwanted microbes. The … Under ideal circumstances the methods used for microbial control should be inexpensive and fast-acting. For example, heat, chemical agents, or radiation are all more effective when the time of exposure is increased. The microbial concentration of an indoor OR extrinsically influences surgical site infection rates. Start studying Microorganisms 7: Environmental Influences and Control of Microbial Growth. The spores can stay alive inside canned goods and eventually cause disease in humans. J.N. Thus, various methods of processing and preservation are being applied to inactivate or inhibit microbial growth in order to extend product shelf-life, while maintaining palatability and safety. Be able: to use terminology of microbial control. Chapter 5 Control of Microbial Growth . Typical disinfection does not lead to sterilization because endospores tend to survive even when all vegetative cells have been killed. Other species aggressively attach to the surfaces they live on to avoid microbial control. Every organism has a minimal, maximal and optimal pH for growth.Some organism can grow better at low pH or acidic pH, some can grow in alkaline pH and while other grow at somewhat neutral pH.pH influence both the growth rate and types of organism that will predominant the food. The control of the moisture content in foods is one of the oldest exploited preservation strategies. Semicritical items do not typically need to be sterilized but do require a high level of disinfection. A. bacteriostatic For example, conditions such as high humidity and wet and dirty shells, along with a drop in the storage temperature will increase the likelihood for entry of bacteria. Inanimate items that may harbor microbes and aid in their transmission are called, The CDC and the NIH have established four, Medical procedures with a risk for contamination should be carried out in a, Sterilization is necessary for some medical applications as well as in the food industry, where endospores of, Physical or chemical methods to control microbial growth that result in death of the microbe are indicated by the suffixes. What are some characteristics of microbes and infectious agents that would require handling in a BSL-3 laboratory? The amount of time it takes for a specific protocol to produce a one order-of-magnitude decrease in the number of organisms, or the death of 90% of the population, is called the decimal reduction time (DRT) or D-value. Longer exposure times kill more microbes. It was clear that Lister's techniques were effective in increasing the rates of surviving surgery, but his theories were controversial because many 19th century surgeons were unwilling to accept something they could not see. Radiation . ... Methods of Control of Bacterial Growth (physical) (high temp) : Moist Heat - boiling (100 degrees celsius) - not considered sterilization - kills most pathogens but exceptions are common … In this unit we will concentrate on the chemical control of microbial growth with a special emphasis on the antibiotics and chemotherapeutic antimicrobial chemicals used in treating bacterial infections. The physician also prescribed a course of the antibiotic ciprofloxacin, confident that it would clear Roberta’s infection. MICP has been found to be able to improve soil strength, stiffness, liquefaction resistance, erosion resistance, while maintaining a good permeability simultaneously. 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