Acid fastness

The ability of the tubercle bacillus and other members of the genus Mycobacterium to retain certain dyes after treatment with a dilute mineral acid.  This enables these bacteria to be detected by microscopical examination of sputum and other clinical specimens in which they are seen as red rods against a green or blue counterstain background.

Acquired drug resistance

Resistance to anti-tuberculosis drugs developing in a patient due to sub-optimal therapy (usually not completing the course of treatment).

Adherence

Whether a patient sticks to their prescribed treatment programme

AIDS

Acquired Immune Deficiency Syndrome. This is the final stage in the course of HIV disease in which profound immunosuppression predisposes to certain aids-defining’ infections and other disease of which commonest across the world is tuberculosis.

Anergy

The failure of a patient to respond immunologically to an infective challenge. This may be suggested by a negative tuberculin reaction in a patient with active tuberculosis.

Annual incidence (of tuberculosis)

The number of new cases of tuberculosis detected over the period of one year.

Antigen

A molecule in, for example, a micro-organism that induces an immune response.

Artificial pneumothorax

An operation, commonly done in the days before anti-tuberculosis therapy, to collapse a lung by introducing air into the pleural cavity.

Atypical Tuberculosis

See Environmental Mycobacteria.  Disease caused by environmental mycobacteria (mycobacteria common in the world around us) is sometimes called atypical tuberculosis, but this is an unfortunate misnomer as the two diseases are quite different in their behaviour. In particular, disease due to environmental mycobacteria is not infectious.

Autoimmune disease

Disease due to the immune system attacking parts of the host body rather than invading ‘foreign’ micro-organisms.

Bacille Calmette-Guérin (BCG)

The only vaccine currently used to prevent tuberculosis. It was developed by the French scientists Albert Calmette and Camille Guérin at the Institut Pasteur, Lille, between 1907 and 1921. It is a living, attenuated (weakened) variant of the bovine tubercle bacillus.

Bacillus (pleural – bacilli)

Literally, ‘a rod’, this refers to rod-shaped bacteria, in contrast to the circular coccus (pleural – cocci). (The term is complicated as one genus of bacteria is called Bacillus. This includes the organism causing anthrax – Bacillus anthracis.)

Bacterium

A large group of single-celled organisms which, together with the blue-green algae, are characterised by having a nucleus which is not confined by a nuclear membrane.  Most bacteria are free-living in the environment but a few cause disease in humans and animals. Bacteria are quite different from viruses.

Biopsy

Removal of a sample of tissue, by means of a fine needle, bronchoscope or other instrument, or through a small incision, for laboratory examination.

Bovine tuberculosis

Tuberculosis of cattle caused by the bovine tubercle bacillus, Mycobacterium bovis.  Disease is transmissible to humans, directly from cattle by or by drinking milk from cows with tuberculous mastitis, in countries where bovine tuberculosis has not been eliminated.

Bronchoscopy

Examination of the airways by means of a flexible or rigid tube. Modern instruments are fibre-optic and highly flexible and they enable specimens to be obtained from the lung by aspiration, washing, brushing and biopsy.

Buruli ulcer

A chronic tropical disease characterised by extensive skin ulceration. Caused by Mycobacterium ulcerans.

Butcher’s wart

Also called prosector’s wart, this is a tuberculous skin lesion acquired by accidental injury while cutting up tuberculous animal carcases or human corpses.

Cachexia

The extreme wasting seen in people with advanced tuberculosis.

Case-finding

The search for people with tuberculosis, usually by microscopical examination of sputum of ‘suspects’ with a cough of over three weeks duration.

Caseation

See Caseous necrosis (below)

Caseous necrosis

The characteristic central area of tissue necrosis seen in tuberculous lesions, most evident in post-primary lesions.  The term caseous necrosis or caseation is in allusion to the cheese-like nature of this necrotic material.

Cavity, pulmonary

A necrotic tuberculous lesion which communicates with the airways, enabling tubercle bacilli to enter the sputum and to be coughed out.

Cerebrospinal fluid

The fluid surrounding the brain and spinal cord.

Chemoprophylaxis

The prescription of anti-microbial agents to prevent those at risk of an infection from developing the disease.

Chemotherapy

Treatment of disease (not just cancer) by chemicals.  This includes treatment of tuberculosis by various anti-bacterial drugs.

Combination Treatment Therapy

The combination of two or more anti-tuberculosis agents in a single tablet. This avoids the possibility of patients taking a single agent which can give rise to antibiotic resistance.

Congenital tuberculosis

Tuberculosis acquired by the baby while in the uterus. An uncommon but serious form of tuberculosis.

Consumption

An old term for tuberculosis, in allusion to the wasting seen in advanced disease.

Contact tracing

The search for persons infected by a patient with open or infectious tuberculosis, principally in the patient’s household.

Contagion parameter

The number of people infected by a single infectious patient.

Corticosteroids

Anti-inflammatory hormones prescribed in some cases of tuberculosis, notably tuberculous meningitis and tuberculous pericarditis, to prevent constrictive scarring

Crohn’s disease

A chronic inflammatory disease of the human intestine, thought by some to be caused by the same mycobacterium that causes Johne’s disease in cattle, although confirmation is required.

Cryptic disseminated tuberculosis

Widespread tuberculosis occurring in those with suppressed immune function, such as those with AIDS.  The tissues contain numerous microscopic lesions teeming with tubercle bacilli. In contrast to the lesions of miliary tuberculosis these are not easily seen on radiology, hence the term cryptic.

Culture

The process whereby bacteriological specimens are grown in an incubator. In the case of tuberculosis this can take weeks.

Cytokines

From the Greek words meaning ‘cell energisers’, these are molecules released during immune responses that ‘direct’ the various cells involved in these responses.  Examples include gamma interferon and tumour necrosis factor.

Delayed type hypersensitivity

A term to encompass cell-mediated immune reactions that are detectable by skin testing.  They are termed delayed as they take longer to appear than various antibody-mediated hypersensitivity reactions characteristic of allergic conditions.  The positive tuberculin test is a typical example of a delayed hypersensitivity as it takes around 48 hours to develop.

Directly observed therapy (DOT)

Administration of anti-tuberculosis drugs under direct supervision. One of the elements of the World Health Organization DOTS strategy.

Disease ratio

The ratio of those infected with, for example, the tubercle bacillus and those actually developing the disease

DNA (deoxyribonucleic acid)

The famous ‘double helix’ forming the molecular structural basis of  genes and chromosomes.

DNA fingerprinting

A technique used to divide a species, such as Mycobacterium tuberculosis, into many variants by detecting small differences in their DNA structure.  This enables the spread of these variants in the community to be studied for epidemiological purposes.

DOTS

The ‘brand name’ of the World Health Organization strategy for the control of tuberculosis.  The components are government commitment, diagnosis principally by sputum microscopy, good quality drugs supplied free to the patients, directly observed therapy and monitoring of the efficacy of the control activities.

DOTS-Plus

A modification of the DOTS strategy to manage multi-drug resistant tuberculosis.

Drug interactions

The effect of one drug on the absorption, metabolism and activity of another.  Several important drug interactions occur between rifampicin and other drugs, especially antiretroviral drugs given to those infected with HIV.

Drug resistance

A mutational event in the bacterial cell leading to resistance to an anti-tuberculosis drug. Drug resistance is determined in the laboratory by growing isolated tubercle bacilli on media containing various concentrations of the drug.

Ehrlich, Paul

German microbiologist and pathologist, most famous for his ‘magic bullets’ against syphilis.  He discovered the characteristic ‘acid-fast’ staining property of mycobacteria and used it to visualise tubercle bacilli in sputum, including his own!

Endogenous reactivation, of tuberculosis

Tuberculosis occurring years or even decades after infection due to activation of the original infection.

Environmental mycobacteria

In addition to the Mycobacterium tuberculosis complex and Mycobacterium leprae, there are many species of mycobacteria that live in watery environments. Some of these occasionally cause human disease, notably in those who are immunosuppressed. Environmental mycobacteria can only be distinguished from their more aggressive cousin M. tuberculosis by bacteriological culture. Clinically the presentation of pulmonary disease is similar to tuberculosis with chronic cough weight loss and malaise. Soft tissue disease particularly of the lymph glands may occur in children. On microscopic smear and by the histological changes they cause, they are indistinguishable from the tubercle bacillus.

Epidemiology

The study of the causes, distribution, frequency and control of disease in populations.

Erythema nodosum

Firm and painful red patches or nodules, usually on the lower limbs, most often seen in children with primary tuberculosis aged between 5 and 10 years. It occurs more frequently in girls and in those with fair skin. It usually clears up within two weeks although reddening of the skin may remain for several weeks.  It also occurs in other conditions, including streptococcal infections, leprosy, systemic fungal infections, sarcoidosis, leukaemia and as a reaction to certain drugs.

Ethambutol

One of the first-line anti-tuberculosis drugs, given during the first 2 months of therapy. Care is required in its use as it can cause visual disturbance (blurred and red/green colour disturbance) and irreversible eye damage.  Patients should be told that if they experience any visual disturbance they should stop taking the drug and seek medical advice.

Ethionamide  (Etionamide in the USA)

A drug used to treat cases of drug resistant tuberculosis. It is closely related to prothionamide (protionamide), a drug used for the same purpose.

Exogenous re-infection, of tuberculosis

Tuberculosis occurring in a person previously infected by tubercle bacilli but due to a new and recent re-infection.

Extra-pulmonary tuberculosis

Tuberculosis occurring outside the tissues of the lung, but including lesions within the thoracic cage.

Extra-thoracic tuberculosis

Lesions of tuberculosis occurring outside the thoracic cage.

Fish tank granuloma

See Swimming pool granuloma.

Fluoroquinolones

A class of antibiotics used to treat drug-resistant tuberculosis and some diseases caused by environmental mycobacteria. Examples include ofloxacin, ciprofloxacin and moxafloxacin.

Gamma interferon

A cytokine that is essential for protective immunity in tuberculosis by enabling macrophages to express their full ability to contain the infection.

Gastric aspiration

The removal of the gastric contents through a tube passed down the oesophagus. This is used to harvest tubercle bacilli that have ascended from the lung to the pharynx and been swallowed overnight. It is used in those patients, particularly children, who do not produce sputum.

Genus

The term used to describe the group of organisms above species. Thus the human tubercle bacillus, Mycobacterium tuberculosis, is just one of a hundred or so named species within the genus Mycobacterium. (NB. By convention, the initial letter of a generic name is capitalised and printed in italics.) See Taxonomy.

Ghon focus

The initial focus of tuberculous infection in the lung.

Gibbus

The angular ‘hunchback’ deformity characteristic of advanced spinal tuberculosis.

Granuloma

This is the basis of the tubercle, or ‘little potato’, which gives the disease its name.  Granulomas are characteristic of chronic infections and consist of a compact aggregate of active macrophages around the infecting agent. In tuberculosis, the granulomas may be of enormous size and often show central ‘caseous’ necrosis.

Haematuria

Presence of blood in the urine

Histology

HIV

Human immunodeficiency virus. The cause of HIV disease (below) and AIDS.

HIV positive

Someone who has tested positive for HIV

Hong Kong operation

A radical operation to prevent and correct deformity in cases of spinal tuberculosis.

Hydrocephalus

Accumulation of cerebrospinal fluid in chambers (ventricles) within the brain.  The pressure causes severe damage to the brain and, in infants with pliable skull bones, swelling of the head.  It is a serious complication of tuberculous meningitis and requires surgical decompression by means of a valve.

Hypersensitivity reaction

An immunological reaction that does more damage to the host than to the causative agent of the reaction.

Immune system

The body’s defence system against outside attackers. The immune system fights off infection and retains memory cells that will protect against future attack.

Incubation period

The interval between infection and the development of clinically evident disease.

Influenza-like syndrome

A side effect of rifampicin. Paradoxically, it is more common when rifampicin is given twice or three times a week than when given daily.

Initial drug resistance

See Primary drug resistance.

Interleukins

Literally ‘between white cells’, these are cytokines that have been well characterised and allocated numbers.  Many are involved in immune responses in tuberculosis.

Isoniazid

A synthetic agent and one of the first line anti-tuberculosis drugs.  It is particularly effective against actively replicating bacilli in the lung cavities. It is also used for preventive therapy in those with latent tuberculosis.

Jaundice

Yellowing of the skin or eyes caused by excess circulating bilirubin due to some types of liver failure.   Hepatitis can be a side-effect of TB medicines and if it occurs the patient should stop taking all medicines and seek medical attention immediately.

Johne’s disease

Also called paratuberculosis or chronic hypertrophic enteritis, this is an intestinal disease of cattle and some other hoofed animals caused by Mycobacterium avium var. paratuberculosis.  It has been suggested, but not confirmed, that this organism is the (or a) cause of Crohn’s disease in humans.

King’s Evil

A term used for extrapulmonary tuberculosis, especially cervical lymphadenopathy (scrofula).  The name refers to the belief that the condition could be healed by the touch of the reigning monarch, as graphically described in Shakespeare’s Hamlet.

Koch phenomenon

A necrotic hypersensitivity reaction induced in the skin of tuberculous guinea pigs following the injection of tubercle bacilli, leading to destruction of the bacilli and local healing.  It is also induced by injection of Old Tuberculin.

Koch, Robert

The German microbiologist who discovered the tubercle bacillus in 1882.

Langhans’ giant cells

Large cells with many nuclei, often in a ‘horseshoe’ formation.  These cells are regularly seen in tuberculous lesions but also occur in granulomas due to other conditions.

Latent tuberculosis

A term applied to the status of those infected with the tubercle bacillus but remaining healthy.  It is assumed that the tubercle bacilli are in some dormant or resting ‘persister’ state, although the exact nature of this state is hotly debated

Liquid Media (Liquid Culture)

Specimens can be cultured using either solid or liquid nutrient materials (culture) for the bacteria to grow in. Liquid media are used as an alternative to solid media particularly in automated culture systems that provide results more rapidly than conventional culture techniques based on solid media.

Live Vaccine

Vaccines which contain living microbiological organisms, including BCG, measles, mumps, rubella and polio

Löwenstein-Jensen medium

The most widely used culture medium for isolation of tubercle bacilli and other mycobacteria.  Basically, it is hard boiled egg with the addition of glycerol and a few mineral salts.

Lupus vulgaris

A very chronic and disfiguring form of skin tuberculosis usually affecting the face.  The term intrigued the famous German pathologist Rudolf Virchow who traced its use back to the 10th century but not to its origin.  The word lupus is, in this context, thought to be a corruption of lepros – a term applied in the past to many skin conditions and not just to leprosy.

Lymphadenitis

Inflammation of a lymph node.  Tuberculous lymphadenitis is one of the commonest forms of extra-pulmonary tuberculosis.  The lymph nodes of the neck (cervical nodes) are the most frequent site.

Lymphadenopathy

Disease of the lymph nodes. Often used synonymously with lymphadenitis.

Macrolide

A class of antibiotics of which erythromycin is the best known example.  Some newer macrolides -  azithromycin and clarithromycin – are used to treat cases of multidrug resistant tuberculosis and disease due to certain environmental mycobacteria.

Macrophage

One of the classes of phagocytic cells and particularly involved in chronic infections such as tuberculosis.

Mantoux test

A method for performing the tuberculin test by injecting a set amount (usually 0.1 ml) of tuberculin into the skin with a hypodermic syringe.

Miliary tuberculosis

A form of disseminated tuberculosis occurring in patients with relatively good immune responses.  The lesions are millet-seed sized granulomas (Latin: milium – a millet seed) that are easily seen on chest radiographs and, sometimes, on the retina by use of an ophthalmoscope.  Miliary lesions differ from those of cryptogenic disseminated tuberculosis.

Multi-drug resistant tuberculosis (MDR-TB)

By definition, tuberculosis resistant to rifampicin and isoniazid (with or without resistance to other drugs).  With care, most patients can be cured by use of alternative drugs but at a high financial cost.

Mycobacterium

The name of the genus of bacteria which includes the tubercle and leprosy bacilli and the environmental mycobacteria.  The name means ‘fungus bacteria’, in allusion to the mould-like pellicles they form on liquid culture media.

Mycobacterium tuberculosis complex

A group of very closely related species that cause tuberculosis in humans and other mammals.  These are Mycobacterium tuberculosis, M. bovis, M. africanum and M. microti – the vole tubercle bacillus.

Negative Pressure

An isolation room used for infectious patients from which the air is constantly being extracted to result in slight negative pressure in the room compared with the outside corridor. Any bacteria coughed by the patient will then be extracted through a filter system rather then blowing into the corridor.

Notification (denotification)

The process of informing the officer for public health ( Consultant in Communicable Disease) that a patient has a notifiable infection. This is usually done by filling out an official form.

A patient may be found to have been diagnosed incorrectly so that “denotification” is required. There is no official form for this so it is usually done by letter or telephone.

Old tuberculin

A heat-concentrated filtrate of the medium in which tubercle bacilli had been grown.  It was produced by Robert Koch in 1891 who, on the basis of the Koch phenomenon, claimed that it would be an effective treatment for tuberculosis.  After safety tests on Hedwig Freiberg, a 17 year old art student (who later became Mrs Robert Koch), it was introduced into clinical practice but soon abandoned owing to disappointing results and a few fatalities due to ‘tuberculin shock’.  It was, however, used as the basis for the tuberculin test by the Austrian physician Clemens von Pirquet in 1907.

Open tuberculosis

Infectious tuberculosis with microscopically detectable acid-fast bacilli in the sputum.

Outcome (treatment/episode)

There are a number of outcomes as a result of treatment. These can be divided into 1. Cure 2. Satisfactory completion of treatment. 3. Death. 4. Failure to cure. 5. Relapse 6. Transfer out (to another treatment centre) 7. Default (the patient is lost to follow up before treatment is completed.

Para-amino salicylic acid (PAS)

One of the earliest anti-tuberculosis drugs, it is still occasionally used for treating multi-drug resistant tuberculosis.

Paediatric TB

TB in children

Pathogen

A micro-organism able to cause disease. There are two types – obligate and facultative (or opportunist). 

PCR

See Polymerase Chain Reaction

Percutaneous

The route of administration through or via the skin

Pericarditis

Inflammation or infection of the pericardium – the bag in which the heart lies.  Tuberculous pericarditis is an uncommon and serious condition as scarring can interfere with the normal beating of the heart (constrictive pericarditis). For unknown reasons, it is particularly common in the Transkei where it was termed ‘Transkei heart’.

Peripheral neuropathy

Pins and needles in the fingers or toes

Persister

See Latent tuberculosis

Phagocytosis

The ‘eating and digestion’ of micro-organisms by specialised cells of the immune system.  Some pathogens, including the tubercle bacillus, are resistant to digestion and thrive within these phagocytic cells. They are thus referred to as intracellular pathogens.

Phlyctenular conjunctivitis

Inflammation of the eye with itching or pain, excessive production of tears and sensitivity to light. It is most frequently seen in children with primary tuberculosis aged between 5 and 10 years and occurs more frequently in girls than in boys. Usually just one eye is affected. Small grey nodules are seen near the edge of the cornea and the adjacent area of the eye is reddened due to dilatation of blood vessels.  It usually clears up within a few days although it may recur.

Phthisis

Meaning wasting, an old term for tuberculosis.

Pleura

The membranes forming a sac or cavity in which the lungs lie.

Pleural effusion

Fluid accumulating in the pleural cavity.

Pleurisy

Inflammation of the pleura. 

Point prevalence

The number of cases of a disease in a community at a given point in time.

Polymerase chain reaction

A technique for amplifying a few specific fragments of DNA in a clinical specimen to millions of fragments that are easily detectable. This method has the potential to detect tubercle bacilli in specimens within hours rather than weeks. Initial problems of sensitivity have been resolved but cost factors prevent its universal use.

Poncet’s disease

A form of arthritis, thought to be due to immune reactions, occurring in a small minority of patients with active tuberculosis.  It usually resolves when the underlying tuberculosis is successfully treated.

Post-primary tuberculosis

Tuberculosis occurring after a period of latency following initial infection (usually appearing three or more years after initial infection).  The usual site, irrespective of the site of the initial infection, is the apex of the lung and tissue necrosis leading to cavity formation is evident.

Pott’s disease

Spinal tuberculosis. Named after Sir Percival Pott, a surgeon at St. Bartholomew’s Hospital, London.

Preventive therapy

Anti-tuberculosis drugs given to a person with latent tuberculosis, (usually indicated by a positive tuberculin reaction) to prevent the development of active disease. Therapy is usually based on isoniazid alone.

Primary complex, tuberculous

The initial lesion of tuberculosis, consisting of a lesion at the site of implantation of the bacilli (usually the lung but occasionally other sites) and in the lymph nodes draining that site.

Primary tuberculosis

Active tuberculosis following initial infection by the tubercle bacillus.

Primary drug resistance

Resistance as a result of infection of a patient by a strain of tubercle bacillus already resistant to one or more drugs.

Pulmonary tuberculosis

Tuberculosis of the lung. The most common form of tuberculosis.

Purified Protein Derivative (PPD)

A derivative of tuberculin prepared by harvesting precipitated proteins. It is less likely to give non-specific reactions than unpurified tuberculin.

Pyrazinamide

One of the first-line anti-tuberculosis drugs. 

Pyridoxine

Vitamin B6.  This is often prescribed with anti-tuberculous drugs to prevent certain side effects of isoniazid on the nervous system.

Radiology

The study of X-rays to diagnose a disease

Rifater

A combination of three medicines (Rifampicin, Isoniazid and Pyrazinamide) in one tablet.  A particular side-effect of Rifater, which should not be cause for concern is that is causes bodily secretions (urine, saliva, semen, vaginal fluids) to be orangey-red.  It may also discolour contact lenses.  Rifater may also affect the efficiency of the contraceptive pill.

Rifinah

A combination of two medicines (Rifampicin, and Isoniazid)

Scrofula

An old name for tuberculosis of the cervical (neck) lymph nodes, formerly often the result of drinking cows’ milk containing Mycobacterium bovis.  The word means ‘little sow’, but why this was applied to this disease remains a matter for speculation.

Short-course chemotherapy (for tuberculosis)

So called to distinguish it from the older anti-tuberculosis regimens of 18 months duration, short-course therapy (SCC) refers to the standard six-month course of drugs for the treatment of tuberculosis.  Most SCC regimens are divided into an initial 2-month intensive phase of four drugs (usually isoniazid, rifampicin, pyrazinamide and ethambutol), followed by a 4-month continuation phase of  isoniazid and rifampicin. 

Side-effects

All medicines can cause side-effects and the most common side-effects from TB medicines are:  Stomach upsets such as nausea (feeling sick), vomiting and diarrhoea; flu-like symptoms such as chills fever, dizziness, joint and muscle aches; Jaundice (yellowing of the skin or eyes); skin rashes and itchiness.  A patient should be advised to stop taking all medicines and seek medical attention immediately if Jaundice is suspected.

Smear-positive/smear-negative

Smear positive means that bacteria can be seen when a sample of sputum is specially stained and examined under a microscope. It usually indicates an infectious patient. Smear negative means that the bacteria could not been seen in a specimen. It may mean that disease is absent or that bacteria are too few to be seen.

Sputum

Phlegm

Steroids

See Corticosteroids.

Stevens-Johnson syndrome

A very serious and often fatal skin eruption occasionally caused by anti-tuberculosis drugs, notably thiacetazone in HIV positive persons.

Streptomycin

The first effective anti-tuberculosis drug, discovered by Albert Schatz and Selman Waksman in 1944.  It is still used, especially in retreatment regimens, but must be given by injection.

Swimming pool granuloma

Also called fish tank granuloma, this is chronic warty skin lesion, resembling lupus vulgaris (qv) and caused by Mycobacterium marinum.  It occurs particularly in those acquiring superficial injuries in swimming pools and in keepers of aquaria.

Symptoms

Symptoms are experienced and reported by a patient (as opposed to Signs, which are discovered by physically examining a patient). The typical symptoms of TB are a cough, which lasts for weeks; coughing up blood; fever (high temperature); sweating (especially at night); unexplained weight loss; fatigue (lack of energy); swollen glands.  Not everyone with TB will have all of the symptoms.

Symptomatic

Illness accompanied by symptoms

Taxonomy

The science of classification of life forms.  Bacteria are divided into genera, e.g. Mycobacterium, which are then divided into various species, e.g. Mycobacterium tuberculosis, Mycobacterium avium.

TB Meningitis

Tuberculosis of the meninges, which cover the brain and spinal chord. Often fatal in children, and frequently associated with severe neurological damage in those who survive

Thiacetazone

A weak anti-tuberculosis drug with the dubious advantage of cheapness but the distinct disadvantage of causing serious and sometimes fatal skin reactions, especially in HIV positive persons. The World Health Organization recommend that it should never be used.

Thoracoplasty

A major operation once used to collapse parts of the lung, thereby closing tuberculous cavities, by excision of segments of the chest wall.

Tine test

A technique for performing the tuberculin test by means of a single-use device with four prongs (tines) coated with dried tuberculin.

Tuberculides

Small necrotic skin lesions, usually multiple, occasionally seen in patients with tuberculosis, especially in the tropics.  They are thought to be hypersensitivity reactions to circulating tubercle bacilli, or fragments thereof, which lodge in the skin.

Tuberculin

See Old Tuberculin

Tuberculin reaction

The indurated swelling in the skin induced by injection of tuberculin.  A positive reaction may indicate active tuberculosis, past infection, past BCG vaccination or, in some cases, infection or disease due to environmental mycobacteria.

Tuberculin skin test

The skin test that elicits the tuberculin reaction.  The methods used today are the Mantoux, Heaf and tine tests.

Tuberculoma

A tuberculous lesion appearing as a tumour-like mass on radiology.

Tuberculosis

A chronic infectious disease caused by the closely related species Mycobacterium tuberculosis, M. bovis and M. africanum.

Vaccination

Derived from the Latin Vacca – a cow – this originally referred to immunization with cowpox to protect against smallpox, but now refers to immunization against any infectious agent.

Virulence

A measure of the ‘power’ of a micro-organism to cause disease.

Virus

A very small infectious particle containing either RNA or DNA, but never both, and only able to replicate within living cells.  Despite the widespread belief of journalists, tuberculosis is NOT caused by a virus but by a bacterium.

Vole tubercle bacillus

Officially known as Mycobacterium microti, it causes disease in voles and other small mammals but rarely in humans.  It was evaluated as a vaccine alongside BGC in England in the 1950s and found equally protective, but was not used subsequently as some of those vaccinated developed skin tuberculosis at the injection site.

Ziehl-Neelsen staining

The name given to the most widely used technique for acid-fast staining of mycobacteria. A modification of Ehrlich’s method.