Download - Microbiology Revision
Microbiology Revision
Mark Eveleigh
Section Outline
1. Bacteria
2. Viruses
3. Eukaryotic organisms
4. Immunisation
Section 1: Bacteria
Bacteria
• Have no nucleus and few organelles• Thick peptidoglycan cell wall = Gram
positive• Thin cell wall = Gram negative
Groups of bacteria
• Gram positive cocci• Gram positive bacilli• Gram negative cocci• Gram negative bacilli• Obligate intracellular organisms
Gram positive cocci: Staphylococci
• S. aureus– Common commensal– MRSA– Skin and soft-tissue infections, LRTI,
meningitis, osteomyelitis, endocarditis, TSS, septicaemia
• S. epidermis– Normal commensal– Skin and soft tissue infections, prosthesis and
line infections
Gram positive cocci: Streptococci
• S. pyogenes– Pharyngitits, impetigo, erysipelas, scarlet fever,
necrotizing fascitits, TSS, septicaemia, Rheumatic fever, post-streptococcal glomerulonephritis
• S. pneumoniae– Pneumonia, otitis media, meningitis,
septicaemia, peritonitis
• S. viridans– Endocarditis
• S. mutans– Dental caries
Gram positive cocci: Enterococci
• E. faecalis– UTI, wound infections, septicaemia, SBE– VRE
• E. faecium– UTI, wound infections, septicaemia– VRE
Gram positive bacilli: Anaerobes
• Clostridium– C. botulinum
• Botulism– C. perfringens
• Gas gangrene– C. difficile
• Diarrhoea, pseudomembranous colitis– C. tetani
• tetanus
• Actinomyces israelli– Subcutaenous infections especially around the
jaw
Gram positive bacilli: Aerobes
• Bacillis anthracis– Cutaneous infection, fever, organomegaly,
systemic involvement leading to haemorrhage
• Corynebacterium diptheriae– Tonsillitis, fauces pseudomembrane,
lymphadenopathy
• Listeria monocytogenes– Pneumonia, meningoencephalitis, ataxia, rash,
stillbirth
Gram negative diplococci: Neisseria
• N. meningitidis– Only infects humans– Meningitis– Septcaemia
• N. gonorrhoeae– Urethral discharge, proctitis, pharangitis,
Reiter’s, endocarditis, ophthalmia neonatorum, infertility
Gram negative diplococci: Moraxella
• M. catarrhalis– Pneumonia, infective exacerbations of COPD,
otitis media, sinusitis, septicaemia
Gram negative bacilli: Anaerobes
• Mycobacterium– M. tuberculosis
• Pulmonary (1o), miliary, meningeal, genitourinary, bone (Pott’s), skin (lupus vulgaris), peritoneal, pericarditis
– M. bovis• Rarely TB in humans from cattle
– M. leprae• Tuberculoid (ineffective immune response)
or lepromatous (vigourous immune response)
– M. avium intracellulare• Usually only in immunocompromised
Gram negative bacilli: Anaerobes
• Helicobacter pylori– Ulcers, MALTomas, GORD
• Spirochaetes– Treponema pallidum
• Primary (chancre), secondary (systemic features e.g. condylomata lata), tertiary (gummas) and quaternary syphillis
– Leptospira interrogans• Tropical granulomatous ulcers
– Borrelia burgdorferi• Lyme disease (erythema chronicum
migrans)
Gram negative bacilli: Enterbacteriaceae
• Escheria coli– Neonatal meningitis, pneumonia, UTI,
diarrhoea (HUS in 0157 strain), osteomyelitis, endocarditis, soft-tissue infection, septic arthritis, septicaemia
• Shigella– Travellers diarrhoea
• Salmonella– Similar to E. coli– Typhoid, parathyoid, UTI, septicaemia,
aneurysm infection, osteomyelitis
Gram negative bacilli: Enterbacteriaceae
• Klebsiella– Common commensals– Pneumonia, UTI, line/prosthesis infections,,
meningitis, osteomyelitis, endocarditis
• Enterobacter– Normal commensals– Soft-tissue infections, UTIs, endocarditis
• Proteus– UTI, struvite nephrolithosis
• Yersinia– Plague (pestis), enterocolitis, mesenteric
lymphadenitis (enterocolitica)
Gram negative bacilli
• Haemophilus influenzae– Meningitis, epiglottitis, pneumonia, septic
arthritis, cellulitis
• Pseudomonas aeruginosa– Pneumonia, UTI, skin infections, bacteraemia
• Brucella– Zoonosis– Indolent infection causing malaise,
organomegaly, diarrhoea, constipation, other non-specific features
– Complications osteomyelitis, meningoencephalitis, abscesses
Gram negative bacilli
• Bordetella pertussis– Whooping cough, pneumonia
• Campylobacter jejuni– Zoonosis– Enteritis– Systemic in immunocompromised
• Vibrio cholera– Epidemic diarrhoea
Obligate intracellular pathogens
• Chlamydia– C. trachomatis
• Cervicitis, salpingitis, conjunctivitis, neonatal pneumonia, PID
– C. psittaci• Pneumonia after bird exposure
– C. pneumonia• Pneumonia, URTIs
• Legionella pneumophilia– Atypical Pneumonia
• Mycoplasma pneumoniae– Atypical pneumonia
Obligate Intracellular Pathogens
• Rickettsia– Coxiella burnetti
• Q fever from cattle/sheep reservoir– Bartonella bacilliformis
• Infects RBCs from sandflies– Bartonella henselea
• Cat-scratch fever– Bartonella quintana
• Lice– Ehrlichia chaffeensis
• Tick-borne– Typhus
• Causes widespread vasculitis
Section 2: Viruses
Viruses
• Infectious sub-microscopic agent• Not really ‘life’ by most definitions• Either DNA or RNA• Replicate inside host cells: have no
capacity to replicate by themselves• Growing appreciation of role in cancers
Groups of Viruses
• DNA viruses– Single-stranded– Double-stranded
• RNA viruses– Single-stranded– Double-stranded– Retroviruses
DNA: single stranded
• Erythrovirus (formerly parvovirus)– Fifth disease– 1st phase: ‘slapped cheek’ appearance– 2nd phase: extensor morbilliform eruption– 3rd phase: rash fades to reticulate pattern– Joint involvement more common in adults
DNA: double-stranded
• Papillomavirus– Viral warts, cervical cancer
• Adenovirus– URTI/LRTI, viral meningitis
• Variola– smallpox
• Vaccinia– cowpox
• Orf– Cutaneous pustules caught from sheep
• Molluscum contagiosum– ‘pearly’ papules
DNA: double-stranded
• Human herpesviridae– HHV1: (HSV1) predominantly oral, lies latent in
neuron– HHV2: (HSV2) predominantly genital, lies latent
in neuron– HHV3: (varicella) chicken-pox and shingles, lies
latent in neuron– HHV4: (EBV) mononucleosis, Burkitt’s
lymphoma, post-transplant, hairy-leukoplakia, lies latent in B-cells
– HHV5: (CMV) retinitis– HHV6: (Sixth disease) roseola infantum– HHV8: Kaposi sarcoma-associated herpesvirus
RNA: Positive single-stranded
• Rhinovirus– Coryza
• Rubella– Usually benign but can cause arthropathy– Congenital infection causes deafness,
microcephaly, cataracts, cardiac defects
• Alphavirus– May cause encephalitis
• Flavirus– Yellow fever, hepatitis C, dengue
• Coronavirus– LRTI/URTI, SARS
RNA: Positive single-stranded
• Enterovirus– Coxsackie A
• Meningitis, gastroenteritis– Coxsackie B
• Pericarditis, Bornholm disease– Polio
• Abortive, non-paralytic or paralytic poliomyelitis
– Echovirus• Meningitis
– Hepatitis A
RNA: Negative single-stranded
• Influenza– Types A and B– Subtypes of A based on (H)aemagglutinin and
(N)euroaminidase– 4 day incubation, droplet spread– Complications bronchitis, LRTI, sinusitis, otitis
media, encephalitis, pericarditis, Reye’s syndrome
• Parainfluenza– Seasonal LRTI/URTI in children e.g. croup
RNA: Negative single-stranded
• Mumps– Parotitis, orchitits, meningoencephalitis,
deafness
• Measles– Coryza, conjunctivitis, Koplik spots– Complications otitis media, LRTI and SSPE
• Respiratory syncitial virus– Bronchiolitis
• Lassa• Lymphocytic-choriomengitis virus• Rabies
RNA: retroviruses
• HIV– 2 subtypes HIV-1 and HIV-2– Infects CD4+ T-cells– Seroconversion after 2-6 weeks– AIDS develops once CD4 count <200x106
– Complications opportunistic infection, HIV-encephalopathy, AIDS-dementia, Kaposi’s sarcoma, oral hairy leukoplakia, non-Hodgkin’s lymphoma, retinitis
• Human T-Lymphotropic virus– T-cell leukaemia/lymphoma
Section 3: Eukaryotes
Eukaryotes
• Protista• Fungi• Animalia
Protista: flagellates
• Trypanosoma– T. gambiense
• African Sleeping sickness (slow, wasting)– T. rhodesiense
• African Sleeping sickness (rapid, progressive)
– T. cruzi• Chagas disease (S. america)
• Trichomonas– Vaginitis (‘fishy’, thin discharge, STI)
• Giardia lamblia– Chronic infestation in duodenum/jejunum
Protista: flagellates
• Leishmania– L. major and L. tropica
• Cutaneous leishmaniasis causing ulcer at site of sandfly bite
– L. brasiliensis• Mucocutaneous leishmaniasis
– L. donovani, L. chagasi and L. infantum• Visceral leishmaniasis or kala-azar• dry, warty, hyperpigmented skin lesions• Hypersplenism and lymphadenopathy• High untreated mortality
Protista: Amoeboids
• Entamoeba histolytica– Dysentery, liver abscess, invasive disease
• Cryptosporidium– Uncomplicated diarrhoea– Severe resistant form in immunocompromised
Protista: Sporozoa
• Plasmodium– P. falciparum
• Severe malaria• Complications cerebral malaria, metabolic
acidosis, anaemia, hypoglycaemia, pulmonary oedema, hyperparasitaemia
– P. malaria• Benign, but may cause glomerulonephritis
– P. vivax and P. ovale• Benign, but can lie dormant in liver
• Toxoplasma– Cat host– Congenital defects in pregnancy
Fungi
• Dermatophytes– Trichophyton, Microsporum and Dermatophyton
• Superficial skin and nail infections
• Histoplasma capsulatum– LRTI, retinitis, disseminated disease
• Malassezia furfur– Pityriasis versicolor (macular ‘tan’ rash)
• Cryptococcus neoformans– Meningitis, LRTI in immunocompromised
• Pneumocystis jiroveci– Pneumonia in immunocompromised
Fungi
• Aspergillus– A. fumigatus
• Asthma, ABPA, aspergilloma, invasive aspergillosis
– A. flavus• ABPA, aspergillosis, HCC
– A. clavatus• EAA in association with malt
• Candida albicans– Oral and vaginal thrush, systemic infection in
immunocompromised
Animalia: helminths
• Nematodes– Necator americanus and Ankylostoma
duodenale• Iron deficiency anaemia in Asia, Africa and
Americas– Stongyloides stercoralis
• Cutaenous larva migrans in subtropics– Toxocara canis
• Visceral larva migrans and blindness– Enterobius vermicularis
• Anal itch common in temperate climates– Ascaris lumbricoides
• Migrates to biliary tree
Animalia: helminths
• Cestodes– Taenia
• T. solium– From pork
• T. saginata– From beef
– Neurocysticerosis• Seizures, hemiplegia, hydrocephalus
– Diphyllobothrium latum• Fish tapeworm
– Echinococcus granulosus• Caused by ingesting eggs of parasite (dog)
Animalia: helminths
• Trematodes– Schistosoma
• S. mansoni and S. japonicum– From water-snail vectors– Inflammation and scarring due to type
IV hypersensitivity to eggs– Fasciola hepatica
• Hepatic fibrosis from sheep, snails and water
– Paragonimus westermani• Pulmonary infestation from crabs/ crayfish
– Clonorchis and Opisthorchis• Cholangi -tis/-iocarcinoma, cholecystitis
Section 4: Immunisation
Immunisation
• Active stimulates the body’s own immune system to respond
• Passive is the provision of pre-formed antibodies
• Vaccines may be live, attenuated, dead or toxins
• Adjuvants are often added to stimulate an immune response, often aluminium or bacterial cell-wall compounds
UK immunisation scheduleAge Vaccine
2 months Diptheria, tetanus, pertussis, polio, Hib, pneumococcus
3 months Diptheria, tetanus, pertussis, polio, Hib, meningitis C
4 months Diptheria, tetanus, pertussis, polio, Hib, pneumococcus, meningitis C
12 months Hib, meningitis C
13 months MMR, pneumococcus
3 years Diptheria, tetanus, pertussis, polio, MMR
12 years (♀ only) HPV 16+18
18 years Diptheria, tetanus, polio
*Non-standard vaccinations include hepatitis B and TB (BCG) if specific need identified
UK immunisations
• For travellers• Yellow fever, typhoid, tetanus, polio, rabies
(pre-exposure), meningococcus, Japanese encephalitis, tick-borne encephalitis, hepatitis A and hepatitis B
• Exact vaccines will depend on location, activity and perceived risk pertaining to travel
Live versus inactivatedLive vaccines Inactivated vaccines
Measles Diptheria (toxoid)
Mumps Tetanus (toxoid)
Rubella Pertussis
Polio (oral) Polio (injection)
Typhoid (oral) Meningococcus C
TB (BCG) Haemophilus influenzae B
Yellow fever Pneumococcus
HPV (Cervarix)
Hepatitis A
Hepatitis B
Typhoid (injection)
Influenza
Japanese encephalitis
Tick-borne encephalitis
Rabies