Staphylococcus aureus - Intoxications

2. INTOXICATIONS

1. Food poisoning

2. Toxic shock syndrome (TSS)

3. Staphylococcal scalded skin syndrome (SSSS)

 

1. Food poisoning: (Enterotoxin)

•Enterotoxin is responsible for manifestations of staphylococcal food poisoning

•Nine types of enterotoxin are currently known, named A, B, C1-3, D, E, H & I.

•It usually occurs when preformed toxin is ingested with contaminated food- milk and milk products, meat, fish and ice cream

•The toxin acts directly on the autonomic nervous system to cause the illness, rather than gut mucosa.

• Type A toxin commonly implicated

• Toxin very potent - Microgram amounts cause illness

•Source of infection- food handler who is a carrier.

•Incubation period- 2 to 6 hours.

•Clinical symptoms- nausea, vomiting and diarrhoea etc.

• Post-antibiotic diarrhea can be caused by enterotoxin forming Staphylococci

•The illness is usually self limited, with recovery in a day or so.

 

2) Staphylococcal Toxic shock syndrome (STSS):

•Infection by TSST (Toxic shock syndrome toxin/ (formerly known as  enterotoxin type F)) produced by S.aureus.

•It is fatal multisystem disease presenting with fever, hypotension, myalgia, vomiting, diarrhoea, mucosal hyperemia and erythematous rash which desquamates subsequently.

• Wide outbreaks in menstruating women using vaginal tampons- in 1980’s

• Tampon-related TSS now rare, but occurs in other infections of the skin., mucosa, and some surgical wounds

3) Staphylococcal scalded skin syndrome (SSSS):

•Exfoliative toxin (ET) produced by S. aureus is responsible for Staphylococcal scalded skin syndrome (SSSS)

•It is a skin disease in which outer layer of epidermis gets separated from the underlying tissues

• Severe form in newborns- Ritter’s disease; in older patients-toxic epidermal necrolysis

• Milder forms in newborns-- pemphigus neonatarum and in older patients - bullous impetigo

                                                                                                                                                  (Contd..)

Major Values of biodiversity

Values of biodiversity

Biodiversity has a fundamental value to humans because we are so dependent on it for our cultural, economic, and environmental well-being. Elements of biodiversity can contribute to cultural identity, and many ecosystem characteristics are frequently incorporated into cultural traditions.

Some of the major values of biodiversity are as follows:

1. Environmental Value 2. Social Value 3. Ecosystem Services 4. Economic Value 5. Consumptive use value 6. Productive Use Value 7. Ethical and Moral Value 8. Aesthetic Value.

(contd..)

3. Environmental Value:

The environmental value of biodiversity can be found by examining each ecosystem process and identifying the ecosystem services that result. For instance, in wetlands the vegetation captures water- carried sediment and the soil organisms break down a range of nutrients and pollutants washed into the area.

These processes provide the ecosystem service of purifying water. Wetlands also act as spawning and nursery grounds for some fish and provide a refuge for animals in times of drought. Forests regulate the amount of carbon dioxide in the air by releasing oxygen as a by-product during photosynthesis, and control rainfall and soil erosion.

 Some ecosystem services are easy to overlook until the underlying process is impaired.  For instance, sustained clearance of deep rooted perennial plants over wide areas led to dry-land salinity. Water tables have raised carrying dissolved salts which then concentrate in the soil. 

4. Social Value:

The social value of biodiversity includes aesthetic, recreational, cultural and spiritual values. To this can be added health benefits resulting from recreational and other activities. Traditional societies which had a small population and required less resources, had preserved their biodiversity as a life supporting resource. But, modern man has rapidly depleted it even to the extent of leading to the irrecoverable loss due to extinction of several species.

Thus, apart from the local use or sale of products of biodiversity there is the social aspect in which more and more resources are used by affluent societies. 

There can be marked differences in landscape and biodiversity preferences according to age, socioeconomic factors and cultural influences. The lifestyle of the ancient people was closely interwoven with their surroundings.

The life of the indigenous people in many parts of the world still revolves around the forests and environment, even in these modern times, many of them still live in the forests and meet their daily requirements from their surroundings.

The biodiversity has to a great extent been preserved by traditional societies that valued it as a resource and appreciated that its depletion would be a great loss to their society. The indigenous people always protect the forests for their own benefit. In ancient times, especially in India, the environment in totally i.e., flora, fauna, etc., were held in high esteem.

Trees like Peepal, Banyan and Tulsi are still worshipped. Ladies offering water to Tulsi daily is considered good and there are festivals when ladies tie sacred threads around Peepal and Banyan trees and pray for the welfare of their families.

5. Ecosystem Services:

These services also support human needs and activities such as intensely managed production ecosystems.

Ecosystem service includes:

a. The production of oxygen by land based plants and marine algae;

b. The maintenance of fresh water quality by vegetation slowing run off, trapping sediment and removing nutrients and by soil organisms breaking down pollutants;

c. The production and maintenance of fertile soil as a result of many interacting processes;

d. The provision of foods such as fish, pastures for cattle and sheep, timber, fire wood and harvested wildlife such as kangaroos and native cut flowers;

e. The provision of native species and genes used in industry research and development, for instance, in traditional breeding and biotechnology applications in agriculture, forestry, horticulture, mariculture, pharmacy, chemicals production and bioremediation;

f. Pollination of agricultural crops, forest trees and native flowering plants by native insects, birds and other creatures;

g. Pest control in agricultural land by beneficial native predators;

h. Flood mitigation by vegetation slowing run off and trapping sediment;

i. Breakdown of pollutants by micro-organisms in soil and aquatic ecosystems and sequestration of heavy metals in marine and fresh water sediments;

j. Greenhouse gas reduction by, for instance, sequestering atmospheric carbon in wood and marine calcium carbonate deposits;

k. Maintenance of habitats for native plants and animals; and

l. Maintenance of habitats that are attractive to humans for recreation, tourism and cultural activities and that has spiritual importance.

6. Economic Value:

The economic potential of biodiversity is immense in terms of food, fodder, medicinal, ethical and social values. Biodiversity forms the major resource for different industries, which govern the world economy.

The salient features regarding the economical potential of biodiversity are given below:

1. The major fuel sources of the world including wood and fossil fuels have their origin due to biodiversity.

2. It is the source of food for all animals and humans.

3. Many important chemicals have their origin from the diverse flora and fauna, used in various industries.

4. Diverse group of animals are used for medical research during the testing of new drugs.

7. Consumptive use value:

This is related to natural products that are used directly for food, fodder, timber, fuel wood etc. Humans use at least 40,000 species of plants and animals on a daily basis. Many people around the world still depend on wild species for most of their needs like food, shelter and clothing. The tribal people are completely dependent on the forests for their daily needs.

8. Productive Use Value:

This is assigned to products that are commercially harvested and marketed. Almost all the present date agricultural crops have originated from wild varieties. The biotechnologists continuously use the wild species of plants for developing new, better yielding and disease resistant varieties. Biodiversity represents the original stock from which new varieties are being developed.

Downstream processing - Cell harvesting, Whole-broth Treatment

1. Cell harvesting

The first step in the downstream processing of suspended cultures is a solid–liquid separation to remove the cells from the spent medium. Each fraction can then undergo further processing, depending on whether the product is intracellularly located, or has been secreted into the periplasmic space or the medium. Choice of solid–liquid separation method is influenced by the size and morphology of the microorganism (single cells, aggregates or mycelia), and the specific gravity, viscosity and rheology of the spent fermentation medium. These factors can influence the transfer of the liquid through pumps and pipes.

 

1.1  Broth conditioning

Broth conditioning techniques are mostly used in association with sedimentation and centrifugation for the separation of cells from liquid media. They alter or exploit some property of a microorganism, or other suspended material, such that it flocculates and usually precipitates. However, in certain cases it may be used to promote floatation. This uses the ability of some cells to adsorb to the gas–liquid interfaces of gas bubbles and float to the surface for collection, which occurs naturally in traditional ale and baker’s yeast fermentations.

 Certain floc precipitation methods are also used at the end of many traditional beer and wine fermentation processes, where the addition of finings (egg albumen, isinglass, etc.) may be employed to precipitate yeast cells.

Major advantages of these techniques are their low cost and ability to separate microbial cells from large volumes of medium.

Some organisms naturally flocculate, which can be enhanced by chemical, physical and biological treatments. Such treatments can also be effective with cells that would not otherwise form flocs.

Coagulation, the formation of small flocs from dispersed colloids, cells or other suspended material, can be promoted using coagulating agents (simple electrolytes, acids, bases, salts, multivalent ions and polyelectrolytes).

Subsequent accumulation of these smaller flocs into larger settleable particles, called flocculation, is done by adding inorganic salts (e.g. calcium chloride) or polyelectrolytes. These are high molecular weight, water soluble, anionic, cationic or non-ionic organic compounds, such as polyacrylamide and polystyrene sulphate.

 

Whole-broth Treatment

In some fermentations such as the acetone-butanol fermentation, the whole unseparated broth is stripped of its content of the required product. In the antibiotic fermentations, resins are used to directly absorb the antibiotics streptomycin (using cationic-exchange resin) and novobiocin (anionic resin.) The antibiotics are eluted from the resins and then crystallized. This process saves the capital and recurrent expense of the initial separation of solids from the broth.

Water Analysis- Membrane Filter Method

2. Membrane Filter Method

The membrane filtration method is a direct method of determining the presence and numbers of bacteria.  It makes use of a filtration apparatus which separates bacteria from the water. The bacteria collected on the surface of a removable membrane filter are placed on an appropriate medium and incubated. Colonies have a distinctive appearance and are counted. This method is suitable for low-turbidity waters that do not clog the filter and have relatively few  bacteria that would interfere with the results. 

The membrane filter technique involves filtering a known volume (100 ml for drinking water samples) of water through a special sterile filter. These filters are made of nitrocellulose acetate or polycarbonate and have 0.45 µm diameter pores. A grid pattern is typically printed on these filter disks to facilitate colony counting. When the water sample is filtered, bacteria (larger than 0.45 µm) in the sample are trapped on the surface of the filter. The filter is then carefully removed, placed in a sterile petri plate (on a pad saturated with a liquid or agar-based medium,) containing appropriate medium and incubated for 24 hours at 35-37°C.

 Each bacterium trapped on the filter will grow into a separate colony. By counting the colonies one can directly determine the number of bacteria in the water sample that was filtered. 

Advantages

  §  Simplicity

  § shorter time needed to complete the test (1 day vs. 3 to 4 days in MPN)

  § direct test; not statistical - higher accuracy in counting

Disadvantages

  §  Particulate samples (containing silt or other organic matter) quickly clog the filter

  § Metals and phenols can stick to the filter inhibiting growth of microrganisms (filtration concentrates them on the filter)

Specific Coliform Count:

   Using specific media - EMB/Endo agar for coliforms

     (contd..)

                                                                                    

Staphylococcus aureus - Pathogenicity

Pathogenicity 

Staphylococcus aureus produces- Infections & Intoxications

Infections- Cocci gain access to damaged skin, mucosal or tissue site -Colonize by adhering to cells or extracellular matrix -Evade the host defense mechanisms and multiply - Liberating toxins, – Stimulate inflammation - Cause tissue damage

Intoxications-The diseases are caused by bacterial toxins – produced either in the host or preformed in vitro

1.    STAPHYLOCOCCAL INFECTIONS

§  Most common of bacterial infections- range from trivial to fatal

§  Characterised by localized pyrogenic lesions (not spreading like streptococcal lesions)

§  Common Staphylococcal infections are:

a)  Skin and soft tissue infection

 Folliculitis – Furuncle (boil) – Abscess (breast abscess)- Carbuncle – Impetigo – Paronychia- less often, cellulitis- Wound infection

·         Folliculitis - It is inflammation of the hair follicles; A small red bump or pimple develops at infection sites of hair follicle

·         Sty: A sty is folliculitis affecting one or more hair follicles on the edge of the upper or lower eyelid.

·         Furuncle/boils: If infection extends from follicle to neighbour tissue, Furuncle. Thus it is deep seated infection, originating from folliculitis; Causes redness, swelling, severe pain- Commonly found on the neck, armpit and groin regions- common name- "boils"

·         Carbuncle: Carbuncle is an aggregation of infected furuncles; Carbuncles may form large abscesses; It is a large area of redness, swelling and pain, with pus.

·         Impetigo:  superficial skin infection, usually produces blisters or sores on the face, neck, hands, and diaper area - initially watery, then pus containing and finally honey coloured crust

b) Musculoskeletal infection

·         Osteomyelitis – inflammation of bone

·         Septic arthritis – knee, shoulder, hip

·         Pyomyositis – skeletal muscle infection

·         Bursitis (bursa- fluid filled sacs in the joints)

c) Respiratory

·         Tonsilitis

·         Pharyngitis

·         Sinusitis

·         Otitis – ear infection

·         Bronchopneumonia

·         Lung abscess

·         Empyema – pus in pleural cavity (lungs)

d) Central nervous system

·         Abscess

·         Meningitis

·         Intracranial thrombophlebitis – blood clot in cerebral vein

e) Endovascular

·         Bacteremia – bacteria in blood

·         Septicemia – blood stream infection

·         Pyemia – pus forming bacteria in blood stream (from an abscess)

·         Endocarditis – inflammation of heart valve

f) Urinary

·         Urinary tract infection – routine infections, also in association with local instrumentation, implants or diabetes

(contd..)

Water analysis - General Methods

    Water-borne diseases are caused by many pathogenic bacteria, viruses, protozoa etc. Among the bacterial infections that are spread by water are cholera, enteric fevers, dysentery. Among the viruses, Hepatitis A, poliovirus cause infections after drinking contaminated water. Among the protozoa Amoebic dysentery caused by the protozoan Entamoeba histolytica and those caused by Giardia lamblia, Balantidium coli and Cryptosporidium species which is spread either by drinking contaminated water or by eating food such as fresh fruit, salad or raw vegetables that have been washed in contaminated water. Among the helminthes are Schistosomiasis caused by worms of the genus Schistosoma.

Since it is impossible to test for every pathogenic microorganism, we test for the presence of indicators to decide the potability of drinking water. 

WHO standards say that 

1) potable (drinking) water should have no fecal coliform per 100 ml 

2) potable (drinking) water should have no more than 4 coliforms per 100 ml. 

If more than these are observed, appropriate treatment method should be undertaken.

General Rules of Sampling

1) Wash your hands thoroughly before and after collecting samples.

2) Collect microbiological samples in sterile bottles.

3) Take care to avoid contaminating the sample container and water sample.

4) Label the bottle before sampling.

5) Take a minimum of three samples of each and from different areas of water body.      

6) Perform the analysis immediately and if any delay is there, store the samples at 4 degree C. 

Water Analysis

In short, the different methods of water analysis are

(1) General Methods

1. Total Count/ Heterotrophic Plate Count (HPC)/Colony  Count/Plate count

2. Membrane Filter Method

(2) Specific Methods

1. Coliforms

1. MPN 

2. Colilert defined substrate test 

3. Differential Coliform Test

4. IMViC 

2. Fecal Streptococci  

1. Azide-dextrose/ Glucose azide broth

3. Clostridium perfringens      

1. Litmus Milk Test

4. Pathogenic bacteria  

Specific Methods, if need arises

 

General Methods:

1. Total Count/Heterotrophic Plate Count/Colony Count/SPC-Simple/Standard Plate Count

Small volume of diluted sample pipetted on to surface of the medium and pour plate performed. Incubation at 20-22^oC for 3 days (saprophytes) and/or 37^oC for 24 h (potential pathogens). Count the plate with dilutions which give between 30 - 300 colonies.

Used for general purposes like: 

 Idea about heterotrophic bacterial content of water

 Test the efficiency of water treatment processes

(Pour plate - 1 ml of appropriately diluted inoculum is added to 15 ml of molten agar and poured on petridish. After incubation, Colonies appear throughout the depth of medium. Used to estimate viable count.)

 

                                                                        

                                                                                                                       (Contd..)

Values of biodiversity

Biodiversity

Biodiversity deals with the degree of nature’s variety in the biosphere. The great variety of life on earth has provided for man’s needs over thousands of years. This diversity of living creatures forms a support system which has been used by each civilization for its growth and development.

Biological diversity or nature’s variety in the biosphere can be observed at three levels; the genetic variability within a species, the variety of species within a community, and the organization of species in an area into distinctive plant and animal communities constitutes ecosystem diversity.

Types of Biodiversity:

Genetic Diversity:

Each member of any animal or plant species differs widely from other individuals in its genetic makeup because of the large number of combinations possible in the genes that give every individual specific characteristic. Thus, for example, each human being is very different from all others.

This genetic variability is essential for a healthy breeding population of a species. If the number of breeding individuals is reduced, the dissimilarity of genetic makeup is reduced and in-breeding occurs. The diversity in wild species forms the ‘gene pool’ from which our crops and domestic animals have been developed over thousands of years.

Modern biotechnology manipulates genes for developing better types of medicines and a variety of industrial products and also to create new varieties of more productive crops and to breed better domestic animals.

Species Diversity:

Species is a basic unit of classification and is defined as a group of similar organisms that mate and produce offspring’s with one another and thus, share a common lineage.

The numbers of species of plants and animals that are present in a region constitutes its species diversity. This diversity is seen both in natural ecosystems and in agricultural ecosystems. Some areas are richer in species than others. Natural undisturbed tropical forests have much greater species richness than plantations. A natural forest ecosystem provides a large number of non-wood products that local people depend on such as fruit, fuel wood, fodder, fiber, gum, resin and medicines.

At present conservation scientists have been able to identify and categorize about 1.75 million species on earth. However, many new species are being identified, especially in the flowering plants and insects.

 Areas that are rich in species diversity are called ‘hotspots’ of diversity.

India is among the world’s 15 nations that are exceptionally rich in species diversity.

Ecosystem or Community Diversity:

There are a large variety of different ecosystems on earth, which have their own complement of distinctive inter linked species based on the differences in the habitat. Ecosystem diversity can be described for a specific geographical region, or a political entity such as a country, a state or a village.

Distinctive ecosystems include landscapes such as forests, grasslands, deserts, mountains, etc., as well as aquatic ecosystems such as rivers, lakes, and the sea. Ecosystems are most natural in wilderness areas.

India is exceptionally rich in ecosystem diversity.

If natural ecosystems are overused or misused their productivity eventually decreases and they are then said to be degraded.

Biodiversity is the most precious gift of nature mankind is blessed with. As all the organisms in an ecosystem are interlinked and interdependent, the value of biodiversity in the life of all the organisms including humans is enormous. The role of biodiversity in providing ecosystem services is twofold.

Firstly, biodiversity is directly used as a source for food, fibre, fuel and other extractable resources. Secondly, biodiversity plays an important role in ecosystem processes providing the regulating, cultural and supporting services.

For example, vegetation cover protects the soil from erosion by binding soil particles and minimizing the effects of water runoff. Likewise, cultivation of crops is to a large extent dependent on the availability of pollinating insects.

Values of biodiversity

Biodiversity has a fundamental value to humans because we are so dependent on it for our cultural, economic, and environmental well-being. Elements of biodiversity can contribute to cultural identity, and many ecosystem characteristics are frequently incorporated into cultural traditions.

Some of the major values of biodiversity are as follows:

1. Environmental Value 2. Social Value 3. Ecosystem Services 4. Economic Value 5. Consumptive use value 6. Productive Use Value 7. Ethical and Moral Value 8. Aesthetic Value.

Biodiversity has proven to hold enormous value when adapted for use in health, agricultural, or industrial applications. In the field of medicine alone, approximately 50% of current prescription medicines are derived from or modelled on natural substances. The health and diversity of ecosystems can have a significant effect on the overall stability of nearby communities.

Many arguments to increase efforts to conserve diversity emphasize the value of the riches that is yet to be discovered, including potential sources of new foods, medicines, and energy which can further fuel economic activity, as well as a healthier population.

1. Ethical and Moral Value:

It is based on the principle of ‘live and let others live’. Ethical values related to biodiversity conservation are based on the importance of protecting all forms of life Man is only a small part of the Earth’s great family of species. All forms of life have the right to exist on earth. Morality and ethics teach us to preserve all forms of life and not to harm any organism unnecessarily.

Some people take pleasure in the hunting of animals. People also sometimes degrade and pollute the environment by their unethical actions. Through proper education and awareness, the people’s conscience against such practices must be raised.

Every species has its moral right to exist on earth. Every human culture, religion and society has its own ethical values. There are several cultural, moral and ethical values, which are associated with the conservation of biodiversity. We have in our country a large number of sacred grooves preserved by tribal people in several States. These sacred groves around ancient sacred sites and temples act as gene banks for wild plants.

Each species is unique and has a right to exist. Each species is worthy of respect regardless of its worth to human beings. This point of view was recognized in the World Charter for Nature, adopted by the United Nations in 1982. 

2. Aesthetic Value:

The beauty of our planet is because of biodiversity, which otherwise would have resembled other barren planets around the universe. Biological diversity adds to the quality of life and provides some of the most beautiful aspects of our existence.

Biodiversity is responsible for the beauty of a landscape. Each species and ecosystem adds to the richness and beauty of life on Earth. Once a species be­comes extinct, it is gone forever. A natural eco­system once destroyed is impossible to recreate. The value people attribute to the aesthetic func­tion of nature is partly reflected in the number of people who visit areas of natural beauty.

People go far off places to enjoy the natural surroundings and wildlife. This type of tourism is referred to as eco-tourism is now become a major source of income in many countries. In many societies, the diversity of flora and fauna has become a part of the traditions and culture of the region and has added to the aesthetic values of the place.

(contd..)