Asepsis
Microorganisms are the tiny microscopic structures that cannot be seen with naked eyes. They are present on all the living things and also in the environment. Some of these microorganisms are non pathogenic that is they do not cause any disease. However, many of the microorganisms are pathogenic in nature. The pathogenic microorganisms can cause disease or infections. Absence of these pathogenic microorganisms is known as asepsis.
Importance of asepsis
Asepsis is usually carried out in the laboratory mostly while dealing with microorganisms. The techniques used to carry out asepsis are known as aseptic techniques. If aseptic conditions are not maintained in the laboratory, it may lead to transmission of diseases in humans and may later pass to other animals and plants. Asepsis is also important to prevent contamination of the pure cultures in the laboratory. This helps in maintaining pure culture characteristics. Maintaining aseptic conditions is important in other fields too other than laboratory.
Examples of asepsis outside laboratory
Medical and surgical applications
Medical asepsis, also called as clean technique, involves techniques used in daily activities like hand hygiene, changing patient’s bed linen. Surgical asepsis, also known as sterile technique, is used in surgical wounds, invasive procedure and surgery. It involves destroying all the microorganisms and their spores while medical asepsis involves only inhibiting the growth and the spread of the pathogenic microorganisms.
In a health care facility, any patient is at the risk of communicating a disease. The risk is more for the patients with the lowered resistance. It is important to practice medical asepsis to prevent the contamination to the bedside materials and equipments. This prevents the spread of the disease from one patient to the other and also protects the nurses and the doctors. Asepsis of surgical instruments, urinary catheters ensures that any pathogenic microorganism from one patient or from the environment is not introduced in the other patient undergoing the surgery. All this prevents spread of the disease within and ultimately outside the hospital. There are different methods to maintain asepsis.
Hand hygiene. It is one of the most important techniques in prevention of cross contamination. The standard method for hand hygiene is to wash hands using antiseptic soap for 15-30 seconds, running hands under water.
Gloves and gowns. All healthcare workers can maintain asepsis by wearing single-use sterile latex or neoprene gloves. These gloves should not be reused to avoid infection to other patients and should be disposed properly in the “red bag”.
Safe handling of sharps. Sharp injury like needle stick injury is one of the most common causes of infection in healthcare facility. Sharp containers should be made available at the point of use. While transporting a used syringe, the needle should be removed and a blind hub should be attached. Avoid disposing sharps with other clinical wastes (Kockrow, 2009).
Food preservation
Food has its own natural flora. In some cases, these microorganisms have no deteriorating effect on the food quality. However, in some cases, the microorganisms can deteriorate the food quality causing food spoilage, food borne illness or unwanted fermentation. This can lead to economic losses. There is a possibility of an outbreak of a disease or even shortage of food supply. Thus, the food quality has to be maintained by ensuring asepsis using different methods.
Pasteurization. This is a heat treatment used for preservation of milk. In low-temperature-long-time (LTLT) method, milk is heated for 30 minutes at 62.8 degree Celsius and in high-temperature-short-time (HTST) method, heating is done for 15 seconds at 71.7 degree Celsius.
Packaging foods. Food is preserved in a wide variety of artificial coverings like loose carton or wrapped in hermetically sealed containers. Vacuum packing is done by evacuating all the air before sealing by inserting a vacuum probe into the neck of the package (Gupta, 2007).
Major groups of microorganisms
The major groups of microorganisms are the bacteria, algae, protozoa, fungi and viruses.
Advantages to humans and environment
Bacteria. Probiotics are live microorganisms used a feed supplement which is beneficial to the humans by improving the intestinal microflora. Lactic acid bacteria and bifidobacteria are the groups of bacteria used as probiotics. Bacteria is used in the production of acetic acid, various amino acids, enzymes, antibiotics like streptomycin, erythromycin and also in the production of cheese, yogurt. Bacteria can also be used to remove environmental pollutants like petroleum hydrocarbons, chlorinated compounds.
Algae. They are used as nutraceuticals. They also find use pharmaceutical industries. They contain concentrated levels of to trace minerals, iodine and selenium, important for healthy body functioning. They are used to cure folate deficiency that causes macrocytic anemia. They also have the potential for biodieesel production.
Protozoa. They play an important role in maintaining the fertility of soil. They maintain bacteria in an active growing phase and enhance the rate at which they decompose organic matter. Protozoans excrete phosphorus and nitrogen, enhancing plant growth.
Fungi. They are used in the production of alcoholic beverages, vinegars, cheese and Asian food like soy sauce, miso. Fungal degradation of lignin, cellulose and the release of carbon dioxide have a profound effect on the carbon cycle. Thus, they play an important role in the ecosystem (Buckley, 2008).
Virus. They are used as vectors for gene delivery in tissue engineering. Retrovirus, adenovirus, herpes virus are the examples of such vector system. Viral delivery system has been used in many clinical trials.
Disadvantages to humans and environment
Bacteria. They cause common plant diseases like blights, soft rot and wilt. This causes economic losses. Bacteria can also cause human diseases like cholera by Vibrio cholerae, tuberculosis by Mycobacterium tuberculosis, pneumonia and typhoid.
Algae. Certain blue-green algal species dominate the algal population, becoming a single species bloom, called “algal bloom”. Toxins are released from these algae into the water, thus killing animals drinking this water (Burtle G., 2013).
Protozoa. Cryptosporidium, Giardia, Cyclospora and Toxoplasma are the human enteric parasites and transmit infection through water.
Fungi. Candida species C. albicans, C. tropicalis cause systemic infections, Aspergillus fumigatus infects the lungs, while dermatophytes cause athlete’s foot. Humans are also affected with vaginal infections and other conditions like asthma and allergies (Buckley, 2008).
Virus. Viral diseases like AIDS and other sexually transmitted diseases are still on a large in many countries.
Understanding the relationship between microbes and disease
John Snow (1813 - 1858)
John Snow, a famous anesthesiologist, proposed that cholera reproduced in human body and that it spreads through contaminated water. He is considered as one of the founding fathers of modern epidemiology.
During the September 1854, cholera epidemic at Soho, London, Snow mapped the 13 wells around Soho. He observed spatial clustering of cases around one particular water pump. After examining the water samples from various wells, he confirmed the presence of ‘white, flocculent particles’ in the Broad street sample. Despite the strong opposition from the locals, the pump handle was removed and the spread of disease dramatically reduced and ultimately stopped. He also observed that none of the brewery workers at the brewery one block east of the Broad Street contracted cholera. This is because the fermented beer killed the bacteria. To prove his theory, Snow used proto-GIS methods. By drawing Thiessen polygons around the wells, he defined the straight-line least-distance service areas for each. A large majority of the cholera deaths fell within the Thiessen polygon surrounding the Broad Street pump, and a large proportion of the remaining deaths were on the Broad Street side of the polygon surrounding the Carnaby Street well. Later, Snow redrew the service area polygons, using a pencil and string, those reflected shortest routes along streets to wells - an even larger proportion of the cholera deaths fell within the shortest-travel-distance area around the Broad Street pump. Snow, however, failed to identify the pathogen that caused cholera.
Robert Koch (1843 - 1910)
German scientist Robert Koch introduced new techniques and means of cultivating, manipulating and characterizing microorganisms. Thus, he improved the pure culture technique, based on Pasteur’s concept. Liquid medium was easily contaminated byother organisms. He started the use of solid media giving isolated colonies. With the help of bacterial staining, he discovered many bacteria responsible for different diseases, such as Bacillus anthracis and Mycobacterium tuberculosis. Koch with the help of his colleagues performed many post-mortems and found a bacillus in the intestinal mucosa that was present only in the corpses of persons who died of cholera. He theorized that the bacillus was related to the cholera process, but he was not sure whether it was causal or consequential.
On 7 January 1884, he announced the successful isolation of the bacillus in pure culture and described the bacillus as ‘a little bent, like a comma. On 2 February 1884, Koch reported from Calcutta to the German Secretary of State for the Interior. He reasoned that the vibrion found in the intestines and stools of cholera victims was the causal agent of the disease (Gotuzzo & Lippi, 2013).
Infectious diseases
Malaria
It is considered as one of the most common life-threatening disease. The causative agent of malaria is the blood parasite Plasmodium. The transmission of the parasite into the host occurs through infected female Anopheles mosquito bites that breed in water. Humans can be infected by 5 species: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae and Plasmodium knowlesi. Malaria parasite has two stages – ookinete and the sporozoite. The development of ookinete occurs from the zygote in the midgut lumen of the mosquito. This is an invasive step which is followed by the reduction step. The surviving ookinete develop into the oocysts and these oocyts result in the formation of sporozoite. The sporozoites later enter the body cavity of the mosquito and invade the salivary glands. In the subsequent mosquito bite, sporozoites are transmitted thus initiating the liver infection in the host. The transmission occasionally occurs through blood transfusion and may also depend on climatic conditions.
Prevention. Malaria can be prevented by use of insecticide-treated mosquito nets. This reduces the number of mosquito bites, thus providing community protection. It is also necessary to maintain hygiene at both public and individual level. The dug pits should be filled; the damp areas should be cleaned. Deforestation and the mining projects should be decreased. Care should be taken to prevent the spread of disease through travelers. At personal level, body repellant and mosquito coils can be used. Curtains should be used on windows and doors (United Nations Children’s Fund [UNICEF], 2000).
Public health significance of malaria. As per the estimates, about 207 million cases of malaria were reported in 2012 and there was an estimated death of about 627000 people. Globally, there is a decrease in the mortality rates by 45% since 2000 and in the South-African region, it was an estimated 49% decrease. Young children, non immune pregnant women, people with HIV/AIDS and the travelers are at the risk of developing malaria. More than 90% of the world’s deaths are reported in Africa (World Health Organisation [WHO], 2013).
Bacterial meningitis
According to Massachusetts Department of public health (2011), Neisseria meningitides, Haemophilus influenza and Streptococcus pneumoniae are the causative agents of bacterial meningitis that results in inflammation of the meninges. Less cases of meningitis are observed due to other bacteria. Neisseria meningitides is a common bacteria that normally colonizes in the human nasopharynx. In few cases, it can also cross the epithelial barrier, thus entering the blood stream. After the entry, it may bind and cross the blood-cerebrospinal fluid (B-CSF) barrier making its way to the sub arachnoidal space.
The transmission of Neisseria meningitides occurs among humans through droplets or secretions of the upper respiratory tract. It spreads through saliva during kissing, sharing food, drinks or even cigarettes
Prevention. On exposure to the saliva of someone suffering from meningitis, it is recommended to use antibiotic to prevent the disease. These antibiotics include Haemophilus influenzae (Hib) vaccine, Pneumococcal conjugate vaccine 13-valent (PCV13), Pneumococcal polysaccharide vaccine 23-valent (PPV23), Meningococcal polysaccharide vaccine and Meningococcal conjugate vaccine. The spread of the disease can be prevented by frequent handwashing using soap and water and by avoiding sharing of the food, drinks and cigarettes with other people.
Public health significance of meningitis. Neisseria meningitides is capable of causing both endemic and epidemic infection. Moreover, it can also infect people of all age group. Infection spreads rapidly within a short span of time. In United States, the second leading cause of meningitis is Neisseria meningitides. The worst of this epidemic is observed in less well developed areas of the world. However, in regions of United States and Europe where there is high standard of living, cases of meningitis are reported. In the 2009 epidemic season, 14 African countries implementing enhanced surveillance. They reported 88 199 suspected cases, including 5352 deaths, the largest number since a 1996 epidemic.
References
American academy of microbiology. (2008).The fungal kingdom diverse and essential roles in earth’s ecosystem. Washington, DC: Buckley
Gupta, K.R. (2007). Food and industrial microbiology
Kockrow,O.E.(2009). Medical-Surgical Asepsis and Infection Prevention and Control.
Lippi.D, Gotuzzo.E. (2013). The greatest steps towards the discovery of Vibrio cholera. Clinical Microbiology and Infection, 1-5. doi: 10.1111/1469-0691.12390
Massachusetts Department of public health. (2011). Meningitis. Jamaica plain
The \University of Georgia co-operative extension. (2012). Managing Algal Blooms and the Potential for Algal Toxins in Pond Water: Gary Burtle
