Key Definitions - Microbiological Terms Flashcards

Question

What is the definition of enterotoxin?

Answer 1

an exotoxin with its site of action in the intestine (e.g. from *Vibrio cholerae*)

Answer 2

an outbreak covering a wide geographical area it is a pandemic if it is global

Answer 3

a small portion of a macromolecule recognised by an antibody

Answer 4

complex cells with nuclei and multiple chromosomes, mitochondria (e.g. fungi, parasites)

Answer 5

proteinaceous toxins released by intact bacteria which can act either locally at the site of infection (e.g. enterohaemorrhagic *E. coli*) or remotely, if spread haematogenously (e.g. tetanus, diphtheria)

Answer 6

description applied to micro-organisms with complex growth requirements (e.g. media, atmosphere)

Answer 7

short, proteinaceous filaments which allow attachment and adhesion of bacteria

Answer 8

long, extracellular, proteinaceous filaments which confer motility to cells by rotating

Answer 9

radiation used commercially to sterilise equipment

Answer 10

extensively used double stain to broadly characterise bacteria and make them more easily seen in microscopy Gram-positive bacteria are purple in colour Gram-negative bacteria are pink (the latter colour depends to some extent on the counterstain used in the staining technique)

Answer 11

agglutination of red cells, usually with a specific antigen pre-coated on their surface

Answer 12

a toxin which lyses erythrocytes

Answer 13

lysis of erythrocytes may be used to differentiate, e.g. streptococcal, species on blood agar

Answer 14

a technique in which an antibody with a fluorescent dye attached is used to detect either an antigen or another antibody the antibody binds to its target and the fluorescent label is visible under an ultraviolet microscope

Answer 15

historical rules (often quoted but now outdated) to decide whether a particular organism is responsible for a particular disease: 1. the organism is found in all cases of the disease 2. the organism can be cultured *in vitro* in pure culture 3. the organism can cause the disease in other susceptible hosts

Answer 16

an endotoxin lipopolysaccharides of the Gram-negative cell wall which are released on lysis of the bacteria and may cause shock

Answer 17

a single antibody produced from an in vitro cell culture a monoclonal antibody will only recognise its own particular epitope commonly used in diagnostic tests because of their specificity

Answer 18

a test that detects micro-organism nucleic acid (DNA or RNA) by nucleic amplification the most commonly used NAAT is the polymerase chain reaction (PCR)

Answer 19

hospital acquired (e.g. infection)

Answer 20

minimal agar with the addition of amino acids, nucleotides and some cofactors used for the growth of non-fastidious organisms

Answer 21

clusters of cases of the infection caused by the same organism, apparently related in time and/or geographically

Answer 22

process of heating (e.g. milk) to 65^oC for 30 minutes to kill spoiling organisms, and some pathogens

Answer 23

the ways in which micro-organisms produce disease

Answer 24

polymerase chain reaction an *in vitro* DNA amplification method for the selective amplification of a sequence of DNA from a specimen or sample used to identify the presence or type of a particular genetic sequence

Answer 25

enzymes in the cell wall which help synthesise peptidoglycan and are inhibited by proteins (penicillins which bind directly to PBPs)

Answer 26

a complex carbohydrate polymer cross-linked with amino acids it is an important constituent of cell walls B-lactam and glycopeptide antibiotics, acting at different sites, inhibit its synthesis

Answer 27

supplementary DNA molecules of bacteria which often encode antibiotic resistances and allow their transfer to other cells

Answer 28

simple cells without a nucleus and typically a single chromosome (e.g. bacteria)

Answer 29

a single high antibody level can represent previous exposure or immunisation to diagnose infection reliably, the antibody level should increase significantly between the acute sample, collected when the patient first presents, and the convalescent sample, collected 10-14 days later a fourfold difference between specimens tested simultaneously is generally accepted as a significant rising titre

Answer 30

general term for tests which infer the presence of infection by measuring the patient's antibody response to likely pathogens the presence of antibody does not always mean active infection, however, and informed interpretation of the results is vital

Answer 31

a thick-walled bacterial, or fungal, resting stage may be useful in bacterial identification (e.g. terminal spores in *Clostridium tetani*) in most cases they are highly resistant (e.g. anthrax spores on Gruinard Island)

Answer 32

enhanced effect when certain antibiotics are used in combination (e.g. gentamicin and penicillin)

Answer 33

many older serological tests (e.g. complement fixation test) involve the testing of a range of doubling dilutions of serum the highest dilution at which the test is positive gives the titire (technically the inverse of the dilution)

Answer 34

degree of pathogenicity of an organism through its possession of virulence factors

Answer 35

special stain required to identify mycobacteria on microscopy once such organisms are stained, the stain is resistant to washing with concentrated acid and alcohol these organisms are called acid-alcohol fast bacilli (AAFB)

Answer 36

a family of over 40 viruses which are common causes of respiratory infections, conjunctivitis and gastroenteritis in children agents of ***spongiform encephalopathy*** abnormal proteins that accumulate in the brain to cause spongiform encephalopathy e.g. Creutzfeld-Jacob disease (CJD), new variant CJD (ncCJD), Gerstmann Sträussler Scheinker syndrome (GSS), kuru and fatal familial insomnia

Answer 37

a large nematode that causes intestinal infection and (very rarely) obstruction this worm is easily visible macroscopically, being 15-30 cm (approx) in length infection is by ingestion of embryonated eggs

Answer 38

fungi which cause * ***aspergilloma*** (fungal ball) in lung cavities * otitis externa * allergic bronchopulmonary aspergillosis * invasive aspergillosis in immunocompromised individuals the most common species encountered is ***A. fumigatus***

Answer 39

there are a large number of *Mycobacterium* spp. which are present in the environment some of these can cause disease in immunocompromised patients (*Mycobacterium avium* complex) these can sometimes cause diagnostic problems by giving false positive Ziehl-Neelsen smears e.g. in samples collected via bronchoscopes that have been washed with contaminated tap water

Answer 40

large brick-shaped aerobic Gram-positive bacilli that produce spores unidentified *Bacillus* spp. may be isolated from environmental sources (e.g. dust / clothing), but are rarely of clinical significance ***Bacillus anthracis*** is the cause of the potentially fatal disease anthrax ***Bacillus cereus*** causes an enterotoxin-mediated food poisoning, clasically as a result of germination of spores in food that has been kept warm for a prolonged period (e.g. rice)

Answer 41

group of anaerobes which are the most predominant organisms in normal large bowel flora and faeces often present in mixed intra-abdominal infections _RESISTANT_ to **penicillin** but _SENSITIVE_ to **metronidazole**

Answer 42

fastidious Gram-negative bacilli strictly aerobic and a little difficult to grow - a special perinasal swab is used to collect the sample causes **whooping cough** (pertussis) most children are immunised in their first year

Answer 43

the spirochaete that causes **Lyme disease** the organism is transmitted from rodent and ruminant hosts to man by the ***Ixodes*** **tick**, a zoonosis it characteristically presents with a skin rash (**erythema chronicum migrans**) and an arthritis as the organism is difficult to grow, diagnosis is by serology

Answer 44

fastidious Gram-negative bacilli strictly aerobic and difficult to culture so diagnosis is largely achieved by antibody detection (serology) transmitted from farm animals (zoonosis) cause of **brucellosis**

Answer 45

curved Gram-negative bacilli microaerophilic and grows at 42^oC commonest bacterial cause of **gastroenteritis** in the UK

Answer 46

yeasts that cause superficial infections in the normal host (oral and genital thrush , nappy rash) and deep infection in the immunocompromised host (e.g. oesophageal candidiasis, disseminated candidiasis) the commonest species encountered is ***C. albicans***

Answer 47

the most recently recognised species of *Chlamydia* it is a cause of **community acquired pneumonia** diagnosis is unsatisfactory at present culture is difficult and serology for antibody is the best option, though specific tests are not widely available

Answer 48

the cause of **psittacosis** and **ornithosis** a zoonosis contracted by contact with birds (especially parrots), lambs and other mammals in humans, the disease presents as a **pneumonia** pregnant women are at risk of abortion and should avoud contact with sheep during lambing diagnosis is usually serological

Answer 49

a cause of genital and opthalmic infections including: * nonspecific (non-gonococcal) urethritis * cervicitis * pelvic inflammatory disease (PID) * lymphogranuloma venereum * neonatal conjunctivitis and trachome * pneumonia in neonates & immunocompromised different serotypes are responsible for the different diseases *C. trachomatis* is the commonest cause of sub- and in-fertility in the developed world culture is laborious and time-consuming and infection is usually diagnosed by detecting chlamydia DNA by a NAAT (e.g. PCR)

Answer 50

small obligately intracellular bacteria which, like viruses, can only be grown in cell culture

Answer 51

cause of **botulism** following ingestion of contaminated food most potent neurotoxin known to man rare in the UK

Answer 52

cause of **pseudomembranous colitis** and **antibiotic-associated diarrhoea** produces toxins and spreads easily in hospital due to spore formation treated with **oral metronidazole** or **vancomycin**

Answer 53

formerly called *C. welchii* present in normal faeces, but toxigenic strains can cause **food poisoning** it is also the main cause of **"gas gangrene"**, but this is now rare and most isolates from wounds represent faecal contamination serious infection is treated with **penicillin and/or metronidazole**

Answer 54

cause of tetanus due to toxin acting on the central nervous system infected wound is often insignificant and the organism may not be cultured toxoid (modified toxin) is used for immunisation

Answer 55

a cause of the **common cold** a new form of coronavirus is responsible for the new described infection SARS (severe acute respiratory syndrome)

Answer 56

an aerobic Gram-positive bacillus that is the cause of the toxin-mediated disease, **diphtheria** only strains of the bacterium that are infected with a bacteriophage produce toxin the usual site of infection is the throat, and the target organs for the diphteria toxin are the heart and CNS if fatal, death is caused by respiratory obstruction, heart failure and/or respiratory paralysis diphtheria is treated with antibiotics and antitoxin most strains of *C. diphtheriae* that are isolated are non-toxigenic, and therefore not capable of causing diphtheria

Answer 57

cause a wide range of infections ***coxsackie A viruses (1-24)*** associated especially with **herpangina** (mouth blisters) and **hand foot & mouth disease** and ***coxsackie B viruses (1-6)*** associated with **Bornholm disease** (pleurodynia)

Answer 58

a yeast that causes **meningitis** in immunosuppressed patients, predominantly those with AIDS this organism is easily cultured and there is a good antigen detection test which works on serum or CSF the polysaccharide capsule gives a **characteristic halo** when examined microscopically in a suspension of **India Ink**

Answer 59

a protozoan first recognised as a cause of **severe diarrhoea** in AIDS patients it is now known to be a common cause of self-limiting diarrhoea in children cysts are frequently found in water supplies and lead to outbreaks diagnosis is by microscopy for cysts in stools and there is no available treatment

Answer 60

a herpesvirus primary post-natal infection in 0.3% of births though only a minority are affected in adults subclinical infection is common but CMV may cause **glandular fever** **retinitis** and **colitis** are common in AIDS patients

Answer 61

caused by four mosquito-borne viruses cause rash, fever and viral haemorrhagic fever (VHF) recent change in epidemiology with new areas affected (e.g. Carribbean) no anti-viral treatment or prophylaxis is available

Answer 62

filamentous fungi that cause **infections of the skin** (ringworm, tinea pedis) and **nails** (onychomycosis) the commonest are ***Tricophyton*** **spp.** and ***Microsporum canis***

Answer 63

a viral haemorrhagic fever with high mortality , restricted to central and western africa

Answer 64

a genus of helminth that causes **hydatid** **disease** the commonest species is ***E. granulosus***, a tapeworm of dogs, whose life cycle includes the small intestine of dogs (foxes, wolves, etc.) and the internal organs of ruminants (e.g. sheep, goats) if humans ingest the tapeworm ova, the worms hatch out and migrate to distant tissues (most commonly lungs / liver) and form large fluid-filled cysts because the lifecycle does not progress in human infection, the human is considered to be an "accidental" or "dead-end" host

Answer 65

viruses which cause a wide range of infections (e.g. fever, non-vesicular rashes, meningitis)

Answer 66

an amoeba that causes severe diarrhoea (**amoebic dysentery**)and, occasionally, fluid-filled lesions in the liver (**"amoebic abscess"**) infection is by the faecal-oral route, and is acquired in areas of poor sanitation diagnosis is by direct detection of amoebic cysts (and more rarely motile trophozoites) in stool samples amoebic abscesses may be diagnosed by serology

Answer 67

often colloquially called *"***coliforms**" they are inhabitants of the human gut Gram-negative rods that ferment glucose and are oxidase negative includes: * *Escherichia coli* * *Klebsiella* spp. * *Proteus* spp. * *Salmonella* spp. * *Shigella* spp. * *Yersinia* spp.

Answer 68

pin worm, threadworm a very common helminth infection, transmitted by ingestion of ova from the faeces of infected individuals diagnosis is by detection of ova in stool or from anal samples when diagnosed, this infection is usually treated with an anti-helminthic agent but many cases remain undiagnosed

Answer 69

inhabitants of the human gut Gram-positive cocci that were formerly classified as Streptococci

Answer 70

a gut commensal, which can cause a **urinary tract infection** **vancomicin resistant enterococci** (VRE) are an increasing problem in some hospitals

Answer 71

a major cause of outbreaks of **acute haemorrhagic conjunctivitis** while enterovirus 71 causes outbreaks of hand, foot & mouth disease, meningitis and encephalitis

Answer 72

this group includes: * polio * coxsackie * echo and entero viruses all can cause **non-specific febrile illnesses**, and **aseptic meningitis** despite the name, enteroviruses generally DO NOT cause gastrointestinal disease

Answer 73

this herpesvirus is a cause of **glandular fever** (infectious mononucleosis) EBV is associated with several tumours: particularly **Burkitt's lymphoma** and **nasopharyngeal carcinoma**

Answer 74

a lactose fermenting coliform and commensal of the GI tract most common cause of **urinary tract infection** also causes **neonatal meningitis** and some strains cause **diarrhoea** different serotypes tend to cause different diseases, with *E. coli* 0157 the best known as a cause of **bloody diarrhoea & haemolytic-uraemic syndrome**

Answer 75

a protozoan found as trophozoites in the upper small intestine or as cysts in faeces it is a major cause of **diarrhoea** worldwide and can cause **failure to thrive** due to malabsorption in children diagnosis is by microscopy of stools for cysts or of duodenal aspirates or duodenal biopsies for trophozoites treatment is with **metronidazole**

Answer 76

fastidious Gram-negative coccobacilli capsulated strains type b (Hib) cause **childhood meningitis** and **epiglottitis**, but all children are now offered immunisation non-capsulated strains cause exacerbations of **CGAD**, **sinusitis** and **otitis media**

Answer 77

curved Gram-negative bacilli it is microaerophilic and strongly urease positive it causes **gastritis** and **peptic ulceration**

Answer 78

term for **_parasitic worms_** these are further divided into: * nematodes (roundworms) * cestodes (tapeworms) * trematodes (flukes) parasitic worms have life cycles which include, but are not restricted to, the human host the host in which sexual reproduction takes place is known as the **definitive host**

Answer 79

spread by the faecal-oral route, hepatitis due to HAV is often subclinical in children in adults, although symptoms may be prolonged, fulminant infection and death are very rare and a carrier state does not develop active and passive immunisation are available

Answer 80

spread perinatally or by sexual contact, in blood or bodily fluids symptoms and outcome of infection are related to age and immune competence acute infection is subclinical in most neonates and the immunosuppressed and the risk of chronic infection is high a person who is positive for hepatitis B surface antigen for more than 6 months is considered to have a chronic infection chronic infection is associated with increased risk of **cirrhosis** and **hepatoma** (primary liver cancer, hepatocellular carcinoma) and of extra-hepatic manifestations (e.g. **polyarteritis nodosa** and **glomerulonephritis**) active and passive immunisation are available

Answer 81

spread mainly in blood or bodily fluids acute infection is often subclinical, but chronic infection (HCV RNA positive \> 6 months) follows 80% of acute infections chronic infection is associated with increased risk of **cirrhosis** and **hepatoma** the success of antiviral treatment is genotype-dependent and there are neither active nor passive immunisations available

Answer 82

this defective virus, also known as **delta agent**, can only infect in the presence of hepatitis B either by co-infection at the same time or by super-infection of a hepatitis B carrier it is preventable by preventing hepatitis B

Answer 83

a cause of **enterically transmitted hepatitis** in many developing countries no carrier state develops mortality is high in pregnant women there is no active or passive immunisation availble

Answer 84

a monkey herpes virus which is a rare cause of **severe encephalitis** in man

Answer 85

infections particularly important in the immunosuppressed specific antivirals are available **_Type 1_** is the common cause of **oropharyngeal disease** (gingivostomatitis and recurrent cold sores) **_Type 2_** is the common cause of **genital herpes simplex** **Keratoconjunctivitis** is a common and **encephalitis** is a rare HSV complication

Answer 86

large family of viruses including: * herpes simplex * varicella zoster * cytomegalovirus * Epstein Barr virus * human herpes viruses 6, 7 and 8 * herpes B they remain latent in cells of the host after primary infection and may reactivate later

Answer 87

a retrovirus human immunodeficiency virus **type 1** is a global infection **type 2** is largely restricted to western africa or contacts with west africa several subtypes of HIV1 recognised with differing epidemiology both viruses cause **AIDS**

Answer 88

two species of helminths - ***Ankylostoma duodenale*** and ***Necator americanus*** hookworms live attached to the small intestine, from where they release ova into the gastrointestinal tract on excretion, ova hatch into free-living larvae the larvae penetrate the skin of the foot and migrate to the lungs, from which they make their way to the small intestine (the site of infection) the volume of blood lost as a result of hookworm infection may result in an **iron-deficiency anaemia**

Answer 89

retroviruses HTLV1 is the cause of **adult T-cell leukaemia / lymphoma** and **tropical spastic paraparesis** no diseases are associated with HTLV2 yet

Answer 90

HHV6 is the cause of **exanthem subitum** (roseola infantum) this is a common disease in babies and infants that causes a high fever followed by a rash

Answer 91

no disease associations yet

Answer 92

also known as Kaposi's sarcoma associated herpesvirus (KSHV) it has recently shown to be the cause of **Kaposi's sarcoma**

Answer 93

* Types A and B cause a wide range of respiratory illness, including **influenza** * Type C causes mild respiratory infection annual epidemics due to types A or B occur and pandemics due to type A occur at unpredictable frequency infection is more severe in those with chronic heart and lung disease and the immunocompromised, for whom annual immunisation is recommended chemoprophylaxis and antiviral therapy are available but little used in the UK

Answer 94

gram negative bacilli and a lactose fermenting coliform cause **urinary tract infections** and hospital acquired infections (rarely pneumonia) may become resistant to commonly used antibiotics

Answer 95

a genus of Gram-positive cocci that constitutes the majority of the normal flora of the post-pubertal vagina rarely implicated in disease also forms a component of "probiotic" foods (e.g. *L. acidophilus*)

Answer 96

a highly infectious viral haemorrhagic fever of Western Africa

Answer 97

the cause of **Legionnaire's Disease** and **Pontiac Fever** lives in water supplies, cooling towers, etc. and infection usually results from exposure to a fine aerosolised spray diagnosis by culture (extended incubation on specialised media) is possible, and the organism can be detected by direct immunofluorescence in both cases, bronchial lavage gives a better yield than sputum serology for *Legionella* antibody may be used, but the appearance of the antibody may be considerably delayed more commonly the diagnosis is made by detection of *Legionella* antigen in urine samples

Answer 98

the spirochaete responsible for **leptospirosis** (Weil's disease) approximately 200 serovars of *L. interrogans* have been recognised, each associated with a specific mammilian host, including: * canicola (dogs) * icterohaemorrhagiae (rats) * hardjo (cattle) the organism is excreted in urine, hence the risk of contracting the disease through exposure to contaminated water (e.g. sewage, water sports) although the organism can be cultured from blood, urine and CSF, this is difficult and diagnosis is made by serology for antibody

Answer 99

gram-positive rod found in animal (e.g. unpasterurised cheese) and vegetable (e.g. salads) products and may be ingested causes **meningitis** in neonates and the elderly and **bacteraemia** in pregnancy

Answer 100

small wingless blood-sucking insects three species of lice infect humans: * the **body louse** - *Pediculus humanus* * the **head louse** - *Pediculus capitis* * the **pubic (crab) louse** - *Phthirus pubis* of these, only the body louse is a disease vector responsible for transmission of infections such as **rickettsial diseases** and **relapsing fever** head and pubic lice spend their lives attached to hairs, predominantly in the regions suggested by their names conversely, body lice tend to occupy clothing,to which they return after taking blood meals the eggs of head lice are attached to scalp hairs, whereas body lice lay their eggs in clothing

Answer 101

a group of dimorphic fungi that cause the skin conditions **seborrhoeic dermatitis** and **pityriasis versicolor**

Answer 102

increased severity in those with impaired cell-mediated immunity who are at risk of life-threatening illness without any rash incidence greatly reduced by active immunisation (MMR) of children passive immunisation available for contacts at risk of severe disease

Answer 103

a form of dermatophyte

Answer 104

formerly classified as *Streptococcus milleri* a group of usually non-haemolytic streptococci that includes, among others, ***S. constellatus*** and ***S. anginosus*** Milleri-group streptococci are normally found in the gastrointestinal tract they are common causes of **deep abscesses** e.g. in the liver, brain or lung

Answer 105

has undergone successive name changes from *Neisseria catarrhalis* to *Branhamella catarrhalis* it is a respiratory pathogen, causing exacerbations of **chronic bronchitis** also causes **otitis media** in children third commonest cause of both after *Streptococcus pneumoniae* and *Haemophilus influenzae* 80% or more strains contain **beta-lactamase**

Key Definitions - Microbiological Terms Flashcards

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