Microbiology and Pathogens

Teacher - Peter MitchellBSc (Anatomy & Histology) Dip Health Science (Massage Therapy)BSc (Anatomy & Histology). Dip Health Science (Massage Therapy)

Microbiology is the study of organisms not gy y gvisible to the naked eye.

Thus requiring the use of a microscope to seeThus requiring the use of a microscope to see them.

Microscopic organisms are sometimes calledMicroscopic organisms are sometimes called microbes

The biomass of the microbial kingdom outweighs that of the animal kingdom!

Not all microbes are harmful to humansNot all microbes are harmful to humans

“ Despite the fact that the microbial biomass outweighs the total “ Despite the fact that the microbial biomass outweighs the total animal biomass by a factor of 100 most of us sail through lifeanimal biomass by a factor of 100 most of us sail through lifeanimal biomass by a factor of 100, most of us sail through life animal biomass by a factor of 100, most of us sail through life unbothered by the microbial ocean. They are the host; we the unbothered by the microbial ocean. They are the host; we the

pampered and tolerated guest.pampered and tolerated guest. ””

William Boyd (Pathologist)William Boyd (Pathologist)

There are many examples of microbes being y p gbeneficial to humans

• Some bacteria live in our gut and help digest food

• Some yeasts and bacteria are used in baking, brewing and cheese makingand cheese making

What are Germs?

Micro organisms are found in abundance throughout the environment.

Germs are micro organisms that are likely to cause disease.disease.

Only a very small number of microbes are pathogenic, i e capable of causing diseasei.e. capable of causing disease

Bacteria are just one type of micro-organism,Bacteria are just one type of micro organism, alongside viruses, fungi and protozoa and parasites

Direct damage (lysis of cells by intracellular Direct damage (lysis of cells by intracellular organisms)

Toxin production (vomiting, diarrhea, paralysis, haemolysis, necrosis)g p y y

Damage through inflammation and immune g gresponse

The presence of pathogens does not t ti ll i l diautomatically imply disease.

Context is important e.g.:p gE-coli is normally found in the gut and is not harmful in normal concentrations, however if e-coli numbers increase problems can arise.

ORIf sufficient numbers of e-coli enter the blood via non-intact skin or mucous membranes, serious disease can occur.

VirusesSmallestSmallest

BacteriaBacteria

Fungi

Protozoa & Parasites

Largest

Wh t i i ?What is a virus?

It is very small typically 0 1umIt is very small, typically 0.1um

It is not a true cell

It is not an independently living organism. It must be inside a living cell to replicate

They have genetic material but lack cell membranes, cytoplasm and machinery

The virus uses the host’s cell's machinery and enzymes to generate virus parts which are later

bl d i t i ti l hi h l thassembled into new virus particles which leave the cell to infect other cells

It can infect bacteria, fungi, plants, animals and man

It may remain viable for long time, even in dry conditions

It can survive but does not grow in food

Nearly 1000 different types of viruses are known to infectNearly 1000 different types of viruses are known to infect humans and it has been estimated that they account for approx. 60% of human infections. The young, elderly and immuno-compromised are particularly at risk from virusimmuno-compromised are particularly at risk from virus infections

Many viral diseases are well known and easily identified:from colds and flu to chicken pox and measles

from mumps and herpes to polio, hepatitis and HIV

From the ‘Clinic Hygiene’ point of view, we are mainly concerned with virus infections relating to poor personal or surface hygiene and arevirus infections relating to poor personal or surface hygiene, and are thus preventable

Gastrointestinal infectionsGastrointestinal infectionsGastroenteritisGastroenteritisGastroenteritisGastroenteritisDiarrhoeaDiarrhoeaInfectious intestinal diseaseInfectious intestinal disease

Respiratory infections Respiratory infections FlFlFluFluCommon coldCommon coldBronchitisBronchitis

Skin presenting conditionsSkin presenting conditionsS p ese t g co d t o sS p ese t g co d t o sPapillomaPapilloma

Herpes Herpes –– simplex & simplex & ZoosterZooster

Chicken pox (Chicken pox (PoxivirusPoxivirus))Chicken pox (Chicken pox (PoxivirusPoxivirus))

Papilloma Virus Herpes simplex

Herpes zoster Poxivirus - Chicken pox

Bacteria are prokaryotes (membrane and cell wall) and p y ( )have a characteristic cellular organisation.

They are simple small unicellular organismsThey are simple, small, unicellular organisms

varying in size between 1-20 um long

Damage tissue directly

Also damage tissue by releasing toxins

Bacteria can be classified by shape

Spherical (coccus)e.g. Staphylococcusaureus

Spiral/helicale.g. Treponema

Rod (bacilli)e.g Escherichia coli

Sphere shapedSphere shapedDiplococci- bacterial pneumoniaStaphylococcus aureus- wound infections, boils and infected acne.acne. Streptococci- common culprits in throat infections

Rod shaped- bacilliRod shaped bacillitetanus tuberculosis

Spiralsyphilissyphilis

Typical Growth Curve for a Bacteria PopulationLag Phasegrowth is slow whilst they become used to their new environment and nutrients

Log Phaseonce the metabolic machinery is running, they start multiplying exponentially, doubling in number every few minutes

Stationary Phaseas more and more bacteria are competing for nutrients which are decreasing, growth stops and the number of bacteria stabilises

Death Phasetoxic waste products build up, nutrients have run out and the bacteria begin to die

ImpetigoImpetigo

Staphylococcus Aureus “Golden Staph”

AcneStreptococcus Pneumoniae “meningitis”

Fungi are eukaryotic and exist in different growth g y gforms in different environments. They range from small single cells such as yeasts (~5um) to large complex structuressuch as mushrooms ( 5cm)such as mushrooms (~5cm)

The high humidity and temperatures often found in bathrooms and kitchens are conducive to fungal ggrowth. Mould, or mildew as it is sometimes referred, likes warmth and moderateto high humidity

Fungi responsible for human disease can be dividedFungi responsible for human disease can be divided into two distinct morphological forms

YeastsYeastswhich grow as oval or spherical single cells like bacteria and multiply by budding and division

Filamentous fungimore commonly known as moulds, consist of long, branching hyphae forming a mycelium Asexualbranching hyphae forming a mycelium. Asexual reproduction results in formation of spores

The can be responsible for infectionsThey can be responsible for infections

They can cause an allergic response

Fungi cause discolouration and deterioration of household surfaces giving the characteristic blackening of walls tile grouting plaster and aroundblackening of walls, tile grouting, plaster and around window frames

Can cause unpleasant odours which are difficult toCan cause unpleasant odours which are difficult to disguise. Fungi such as Aspergillus, Penicillium, and Alternata have been found to produce volatile organic

dcompounds

N f i h b f d t d l tilNumerous fungi have been found to produce volatile organic compounds (VOC) and it has been suggested that these affect the health of persons living in mouldy houses. Symptoms include headache, eye, nose and throat irritation and fatigue

VOC’s have been implicated in health issues relating to sick building syndrome

Spores of toxigenic fungi contain mycotoxins (toxic secondary metabolites). Many fungal spores are smallsecondary metabolites). Many fungal spores are small enough to reach the alveoli in the lungs. The mycotoxins may be transported via the blood from the lung to other body sites possibly causing other effectslung to other body sites, possibly causing other effects e.g. skin lesions

Fungi cause 2 types of infection:

Superficial mycoses

Deep mycoses

Fungus grows on the body surface in skin, hair and nailsFungus grows on the body surface in skin, hair and nails

Spread by direct contactSpread by direct contact

Highly contagious and easily spread

E.g.Candida albicans (thrush and nappy rash)( ppy )Athlete’s footRing worm

Involve internal organs, usually life-threatening

Rare except in immunocompromised people

Caused by opportunistic fungi (e.g. Aspergillus)

Acquired by inhalation of spores or by entry throughAcquired by inhalation of spores or by entry through wounds

Some are part of the normal body flora and are harmlessSome are part of the normal body flora and are harmless unless the body’s defences are compromised in some way (e.g. Candida)

Almost all microbial allergens are fungal in origin

Allergic rhinitis (hay fever)BronchitisAsthmaExtrinsic allergic alveolitis

Asthma can be initiated and provoked by allergens commonly encountered in the general environment, for example pollens (trees grass) house dust mitesfor example pollens (trees, grass), house dust mites and moulds.

Tinea Pedis

Ti C ied s

Tinea Corporis

Tinea VersicolorTinea Cruris

Protozoa are single-celled eukaryotesProtozoa are single-celled eukaryotes

Live in water or moist places or other organisms as parasitesorganisms as parasites

Have a resistant transmissible cyst stagestage

Transmission to humans via insect bite or accidental ingestion of infectiveor accidental ingestion of infective stages

Cryptosporidium spp. infects the intestines causing Cryptosporidiosis Large outbreaksinfects the intestines causing Cryptosporidiosis. Large outbreaks are associated with contaminated water or treatment deficiency of water supplies

Gi di l bliGiardia lambliacauses giardiasis, an infection of the small intestine, spread via contaminated food and water and by direct person-to-person contact. Ingestion of one or more cysts may cause diseasecontact. Ingestion of one or more cysts may cause disease

Entamoeba histolyticaan amoeba infecting the large intestine, causes di h /d t d i t i t d t f ddiarrhoea/dysentery, spread via contaminated water or food

Toxoplasma gondiicauses toxoplasmosis, a very severe disease that can produce p , y pcentral nervous system disorders

Parasites are larger and more complex than protozoa.

Common examples of parasites are:

Tape wormsHook wormsPiPin worms

Worms are very contagious and are transmissible viaWorms are very contagious and are transmissible via the faecal – oral route.

That is; the worm eggs are normally ingested due to poor hand hygiene and cross contamination of inanimate objects

Micro-organisms are introduced continually into the clinic via: people food water insects air Wet sites such as sinks toiletspeople, food, water, insects, air. Wet sites such as sinks, toilets, dishcloths and facecloths can also support microbial growth and themselves become reservoirs of potentially hazardous micro-organisms.T l hi b k t tTowels, washing basket etc

Many organisms occurring in the clinic are of little consequence.Some organisms have the potential to cause infectious disease

Some people carry highly pathogenic organisms without themselves being affected - other family members unaware of hazard

Hands, and a whole range of food and hand contact surfaces,combine to provide transfer routes that can move pathogens around the home and ultimately into the body producing infectiony y g