Microbiology Flashcards by Emily W

Describe the characteristics of Gram positive bacteria, and give examples.

Stain purple with gram stain.
Simpler cell wall than gram negative, but a thicker peptidoglycan layer.

2 main cell wall layers- peptidoglycan (with lipotechoic acid and techoic acid), and then an inner/cytoplasmic membrane.

Are less resistant to antibiotics.

Examples: streptococcus, staphylococcus, Bacillus, Chlostridium, Listeria

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Describe the characteristics of Gram negative bacteria, and give examples.

Stain pink with gram stain.
More complex cell wall: lipopolysaccharide, then an outer phospholipid membrane, petidoglycan then inner membrance.

More resistant to antibiotics.

Outer membrane with LPS- lipid portion is toxic and can cause fever and shock.

Examples: E.coli, Neisseria gonorrhoeae, cyanobacteria, proteobacteria, helicobacter.

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Where are lactobacilli normally found in the body?

Vagina

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Where are candida albicans normally found in the body?

Vagina, mouth, skin

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How are streptococcus bacteria arranged?

In a chain of cocci (spheres)

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How are staphylococcus bacteria arranged?

In a bunch of cocci (spheres)

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What are the 4 main components of bacteria which antibiotics target?

Cell wall- Beta lactams (Penicillins, Cephalosporins and Carbapenems) and Glycopeptides (Vancomycin and Teicoplanin)
Protein synthesis (Tetracyclines eg, Doxycycline, Aminoglycosides eg Gentamycin, Macrolides eg. Erythromycin and Streptogramins eg. Pristamycin)
Folate synthesis (Trimethoprim or Sulfonamides eg. Sulfadiazine)
DNA synthesis - Quinolones (Ciprofloxacin) or Metronidazole

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How do Beta lactam antibiotics work? Give examples. What are their common significant side effects?

Beta lactams include Penicillins eg, Amoxicillin, Cephalosporins eg. Cephalexin, and Carbapenems eg. Imipenem.

Bind transpeptidases, preventing peptidoglycan cross-linkage.

Side effects include hyposensitivity, CNS toxicity and seizures, and increased risk of GI disturbances and C. Difficile.

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How do Glycopeptides work? Give examples. What are their common significant side effects?

Glycopeptides (eg. Vancomycin and Teicoplanin) work by binding peptides in peptidoglycan, to inhibit cross-linking.

Side effects include Nephrotoxicity and Red man syndrome (an infusion related hypersensitivity reaction)

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How do Tetracyclines work? Give examples. What are their common significant side effects?

Tetracyclins (eg. Doxycycline) work by inhibiting bacterial protein synthesis, by binding to the 30S ribosome subunit.

Side effects include Binding to teeth and causing staining.

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How do Aminoglycosides work?Give examples. What are their common significant side effects?

eg Gentamycin.
Prevent bacterial protein synthesis, by binding the 30S ribosome subunit.

Side effects include being nephrotoxic and ototoxic.

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How do Quinolones work? Give examples.

Quinolones include Ciprofloxacin and Moxifloxacin.

They work by inhibiting bacterial DNA synthesis, by inhibiting bacterial DNA gyrase.

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Describe the process of gram staining.

Add Crystal violet.
Fix with iodine.
Wash with acetone.
Counterstain with neutral red.

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How do Sulfonamide antibiotics work? give examples of side effects.

Inhibit folate synthesis, by preventing addition of para-amino benzoic acid to folic acid.

Side effects include Steven-Johnson syndrome, skin rash.

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Give examples of Gram positive bacteria.

Bacilli- Aerobic = Listeria, Bacillus
Anaerobic= C.diff

Cocci- Staph eg. S.aureus, S.epidermidis
Strep- S.pneumoniae, S.pyogenes

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Give examples of Gram negative bacteria

Diplococci: Neisseria meningitidis, N. Gonorrhoea
Coccobacilli: Haem influenzae, Brucella, B.pertussis
Bacilli: Shigella, Salmonella, E.coli, Pseudomonas, Klebsiella, Enterobacter

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Name some infections of the skin epidermis.

Impetigo
Folliculitis
Furunculosis

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Name 2 infections of the skin dermis.

Carbunculosis

Erysipelas (rare)

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Name 2 infections of the subcuntaneus layer of skin.

Cellulitis

Necrotising fascitis

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What is impetigo?

Infection of epidermis
More common in children
Golden crusts on erythematous skin

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What is folliculitis?

Infected hair follicle- often the scalp and groin.

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How is folliculitis treated?

Flucloxacillin

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What is furunculosis?

Deep inflammation due to folliculitis

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What is a carbuncle?

Boil in the dermis, extending into subcutaneous layer

Abscess forms

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What is cellulitis and where does it appear?

``` Inflammation of dermis/ subcutaneous layer Often lower limbs, unilateral Red, hot, swollen, painful No necrosis May be red halo around a joint ```

How is cellulitis treated?

Penicillin V AND Flucloxacillin

Which bacteria usually causes cellulitis?

S. Aurues | Occaisionally S. pyogenes

What results may be found on a blood test of a patient with cellulitis?

Raised WCC and CRP

What is erysipelas and where might it be found?

Rare Infection of dermis/subcutaneous layer or face/legs Clear border, raised orange peel appearance

Which Bacteria usually causes Erysipelas?

Group A Strep

How is Erysipelas treated?

Penicillin

What are the 3 stages of necrotising fascitis?

1. Acute- trauma and pain disproportionate to injury. Flu like symptoms 2. Advanced- purple swelling 3. Critical- toxic shock, drop in BP, unconscious

Which bacteria usually cause necrotising fascitis?

Group A Strep

Which bacteria causes gas gangrene?

Chlostridium perfringens

Which bacteria usually cause Septic arthritis?

S. aureus Strep N. Gonorrhoea Gram negative bacilli

What are the risk factors for septic arthritis?

Joint disease Immunosuppression Recent joint surgery Diabetes, CKD

Which joint is most commonly affected by septic arthritis?

Knee

How is septic arthritis treated?

IV Flucloxacillin | May need debridement

What is osteomyelitis?

Bone infection | Often in long bones of legs, arms or back

How is osteomyelitis treated?

Flucloxacillin

What is a dermatophyte infection?

Fungal infection of skin also known as tinea

How are dermatophyte infections treated?

Antifungals eg. Nystatin, Canestan If drug resistant or invasive use Fluconazole

What are the 2 most common causes of soft tissue infections?

S. Aureus | S. Pyogenes

Treponema pallidum causes which STI?

Syphillis

What type of bacteria is Gonorrhoea?

Gram neg diplococci

How is a gonorrhoea infection treated?

Penicillin If allergic: Cephalosporin or Ciprofloxacin

What type of bacteria is Chlamydia?

Gram negative Obligate intracellular so cant grow on culture media Has elementary body and reticulate body

How is chlamydia treated?

Tetracyclines eg. Doxycycline

What type of organism is Trichomonas vaginalis?

Protozoa with flagella

How is Trichomonas vaginalis treated?

Metronidazole

What type of organism is Candida albicans and how is it treated?

Yeast Fluconazole

What is a chancre?

Syphilis sore Firm painless not itchy Disappears after 4 weeks but bacteria remain

Which organisms most commonly cause a UTI?

E coli Pseudomonas aeruginosa in complicated patients

Proteus mirabilis is often associated with __________

Kidney stones

Which antibiotics are recommended for UTIs?

NItrofurantoin (has low resistance risk) BD for 3 days Trimethoprim BD for 3 days

Which antibiotics are recommended for acute pyelonephritis?

Cefalexin (Cephalosporin) Co-Amoxiclav

What is diagnostic of a UTI?

Pyuria | >10^% CFU/ml

What type of virus is Hep A and how is it spread?

ssRNA | Faeco oral, contaminated food and water and shellfish

Where Hep A virus is endemic how is it spread?

Person to person contact | Usually younger patients (asymptomatic)

How can Hep A be diagnosed on blood test?

HAV IgM raised from day 25 HAV IgG raised for life AST and ALT raised

What are the risk factors for Hep A?

Travel MSM IVDU

Which types of Hepatitis are vaccines available for?

``` Hep A Hep B (indirectly Hep D) ```

How is Hep B spread?

``` Blood IVDU Sex Direct conact Vertical transmission ```

Where Hep B is endemic it leads to ___________ infection.

Chronic

Where Hep B is sporadic it leads to ____________ infection.

Acute

How can Hep B be diagnosed on a blood test?

``` HbsAg (Hep B surface antigen) HbeAg (Hep B e antigen- determines infectivity) Anti Hbs Anti Hbe IgM (acute) IgG (chronic) ``` Raised LFTs

Hep B infection can lead to ___________

Cirrhosis | Hepatocellular carcinoma

What will be the blood results in ACUTE Hep B infection?

Raised LFTs HbsAg positive HbeAg positive Anti Hbe may be present IgM and IgG

What will be the blood results in PAST Hep B infection?

Normal LFTs HbsAg positive HbeAg may be positive Anti Hbs IgG

What type of virus is Hep B?

dsDNA enveloped

Which Hepatitis viruses are ssRNA viruses?

Hep A Hep C Hep D Hep E

Which Hepatitis viruses have envelopes?

Hep B Hep C Hep D (uses Hep B)

How can Hep B be treated?

Interferons | Lamivudine

What type of vaccine is the Hep B vaccine?

Recombinant Booster needed every 5 years Aim for antibodies >100

How is Hepatitis C spread?

Blood, IVDU, Sex, Vertical

85% of people infected wtih Hepatitis C develop ____________

Chronic silent infection | 25% then develop cirrhosis (4% develop cancer)

How can Hep C be diagnosed on blood test?

Hep C RNA | Anti HCV

What are the risk factors for the likelihood that Hep C will progress to cirrhosis or cancer?

Alcohol Co-infection with Hep B or HIV Older age Male

How can Hep C be treated?

Interferon Ribavirin Direct acting antivirals

What type of virus is Hep D?

ssRNA with no envelope | Uses Hep B envelope

How is Hep D transmitted?

Blood, IVDU, Sex

What is the difference between Hep D co-infection and superinfection?

Co-infection: Hep B and D together; severe acute disease, low chronic risk Super infection: Hep B carrier then Hep D infection; chronic Hep D, high risk of chronic liver disease

How is Hep E spread?

Faeco-oral route. associated with pigs

How many genotypes of Hep E virus are there?

4 1,2 and 4 in endemic areas 3 in non-endemic areas

How can Hep E be treated?

Ribavirin

What type of virus is HIV?

``` Group 6 retrovirus 2 species (1 high virulence, 2 low virulence) ```

How can HIV be transmitted?

1. Sexual 2. Parenteral- blood and needles 3. Vertical

What are the 3 stages of HIV?

1. Seroconversion- acute, flu, rash, 2-4 weeks post infection 2. Asymptomatic- slow decline in CD4 cells 3. AIDS- CD4 count below 200, susceptible to virulent infections then opportunistic infections

What percentage of people with HIV in the UK are undiagnosed?

12%

What are the AIDs defining conditions?

1. Tuberculosis 2. Kaposi's sarcoma 3. Pneumocystis (fungi) 4. Cryptosporidiosis (parasite) 5. Cerebral toxoplasmosis (protozoa)

What are the signs and symptoms of endocarditis?

``` Fever, night sweats, weight loss New murmur Osler's nodes Janeway lesions Splinter haemorrhages Anaemia Splenomegaly ```

Which organisms most commonly cause endocarditis?

Strep (alpha haemolytic) Staph Enterococci

What is sepsis?

Life threatening organ dysfunction | Caused by disregulated host response to infection

What is septic shock?

Sepsis with 1. Lactate >2 despite adequate fluids or 2. Vasopressors needed to maintain MAP >65

How should sepsis be treated?

1. Broad spectrum antibiotics eg. Meropenem, Cephalosporin 2. Fluids 3. Oxygen

What are the innate causes of immunodeficiency?

1. Neutrophil defect eg. Chronic granulomatous disease 2. NK defect 3. Complement defect 4. Cytokine defect 5. Splenectomy

What are the adaptive causes of immunodeficiency?

1. B cell/antibody defect | 2. T cell defect eg. Di George syndrome

What are secondary causes of immunodeficiency?

1. Splenectomy 2. Chemotherapy 3. AIDS 4. Neutropenia

Which infections do patients who have had a splenectomy usually present with?

Pneumococcus Meningococcus Malaria (encapsulated bacteria)

How do neutropenic patients present?

Bacterial or fungal infections without pus Fever Aplastic anaemia

What is the chance of obtaining Hep C from a needle stick injury?

What type of bacteria is Salmonella?

Gram negative bacilli

What type of bacteria is Enterococci?

Gram positive cocci

What type of bacteria is Listeria?

Gram positive bacilli

What type of bacteria is Neisseria?

Gram negative diplococci

What type of organism is pneumocystis carinni?

Fungi The most common infection in AIDs

What is the most common species of malaria?

Plasmodum falciparum

What is the treatment for malaria?

Quinine | Artesunate

What is the incubation period for dengue fever?

7-14 days

What is a Rickettsial infection?

Gram negative bacteria Transmitted by ticks and fleas Causes Typhus, Pox, African tick bite fever

How is Rickettsial infection treated?

Doxycycline

What is Histoplasmosis?

Infection caused by breathing in fungal spores from bird or bat droppings

What is Schistosomiasis?

Parasitic flatworm Lives in freshwater Causes urinary and bowel infections

What type of antibiotic is Doxycycline?

Tetracycline Inhibits protein synthesis Used for COPD, Chlamydia, malaria

What type of antibiotic is Flucloxacillin?

Penicillin

What type of antibiotic is Gentamicin?

Aminoglycoside

What type of antibiotic is Erythromycin/Clarithromycin?

Macrolide

What type of antibiotic is Metronidazole?

Quinolone

What type of antibiotic is Trimethoprim?

Folate synthesis inhibitor

Cephalosporins and Carbapenems are _________ spectrum antibiotics.

Broad

Give examples of Glycopeptide antibiotics. What can they be used for?

Teicoplanin Vancomycin MRSA, Complicated gram positive infections

When should PEP be taken?

Ideally within 24 hours of potential exposure Within 72 hours Taken for 28 days

Which drugs does PEP contain?

1. Truvada (Emtricitbabine and Tenofovir) | 2. Raltegravir

Quinine and artesunate are used to treat which infection?

Malaria