Gram film interpretation Flashcards by Adam Iqbal

What colour will gram positive organisms stain?

Purple

How well did you know this?

Not at all

Perfectly

What colour will gram negative organisms stain?

Red/pink

How well did you know this?

Not at all

Perfectly

What are the bacterial morphologies (shapes of the bacteria)?

Cocci (singular: coccus) = circle shaped

Bacilli (singular: bacillus) = rod shaped

Vibrio = curved C shape

Coryneform = club-shaped

Spirochete = spiral

Coccobacillus = rod and circle shaped

How well did you know this?

Not at all

Perfectly

How are bacteria named?

Based on how they grow in relation to each other:

Growing in pairs = diplococci
Growing in clusters = staphylococci
Growing in a chain = streptococci

How well did you know this?

Not at all

Perfectly

Features of gram positive cocci in clusters?

Examples
Staphylococcus
e.g.
Staph aureus

Disease presentation
-Cellulitis
-Endocarditis
-Osteomyelitis
-Iatrogenic (from cannula/central line insertion)

Other examples
*Staph epidermidis
- Can cause endocarditis in prosthetic heart valves

How well did you know this?

Not at all

Perfectly

Features of gram positive diplococci?

Examples
Strep pneumoniae

Disease presentation
-Pneumonia
-Meningitis
-Otitis media

Other examples
*Enterocci
e.g. enterococcus faecium, enteroccocus
*faecalis
Can cause UTIs, intra-abdominal infections

How well did you know this?

Not at all

Perfectly

Features of gram positive cocci in chains?

Examples
- Strep pyogenes (aka Group A strep)

Disease presentation
- Tonsilitis
- Scarlet fever
- Rheumatic fever
- Cellulitis

Other examples
- Strep agalactiae (aka Group B strep)
- Causes neonatal sepsis

How well did you know this?

Not at all

Perfectly

How is streptococci grouped?

Grouped initially on whether they are able to haemolyse (breakdown blood) within the blood agar.

Beta haemolysis: complete haemolysis

Alpha haemolysis: incomplete haemolysis

Gamma haemolysis: no haemolysis

How well did you know this?

Not at all

Perfectly

What is the lancefield grouping system?

The Lancefield grouping system primarily focuses on classifying different strains of streptococcal bacteria based on the presence of specific antigens in their cell walls.

These antigens are designated by letters such as A, B, C, D, etc.

For example, Streptococcus pyogenes, which causes strep throat and other infections, is classified as Group A streptococcus (GAS), while Streptococcus agalactiae, associated with infections in newborns and pregnant women, is classified as Group B streptococcus (GBS).

How well did you know this?

Not at all

Perfectly

Why is the lancefield grouping system useful in microbiology?

The Lancefield grouping system is important in microbiology for identifying and characterizing different bacterial strains, which can be useful in diagnosing infections, understanding epidemiology, and developing vaccines and treatments.

How well did you know this?

Not at all

Perfectly

Features of gram positive bacilli?

Examples
- Clostridium perfringens

Disease presentation
- Gas gangrene
- Cholecystitis
- Gastroenteritis

Other examples
- Clostridiodes difficile – gastroenteritis
- Clostridium tetani – tetanus
- Listeria monocytogenes – meningitis,
gastroenteritis, neonatal sepsis

How well did you know this?

Not at all

Perfectly

Features of gram negative diplococci?

Examples
- Neisseria meningitidis

Disease presentation
- Meningitis

Other examples
- Moraxella catarrhalis
- Causes pneumonia, otitis media, sinusitis

How well did you know this?

Not at all

Perfectly

Features of gram negative coccobacilli?

Examples
- Haemophilus influenzae

Disease presentation
- Pneumonia
- Meningitis

Other examples
- Bordetella pertussis which causes whooping cough

Acinetobacter which causes hospital-acquired infections

How well did you know this?

Not at all

Perfectly

Features of gram negative bacilli?

Examples
- E.Coli
- Proteus
- Klebsiella

Disease presentation
- UTI
- Pyelonephritis
- Cholecystitis
- Cholangitis
- Intra-abdominal infections

How well did you know this?

Not at all

Perfectly

Features of vibrios?

Examples
- Vibrio cholerae

Disease presentation
- Cholera

Other examples
- Vibrio vulnificus
- Causes cellulitis, diarrhoea

Vibrio parahaemolyticus which causes gastroenteritis

How well did you know this?

Not at all

Perfectly

Features of spirochetes?

Examples
- Treponema pallidum

Disease presentation
- Syphilis

Other examples
- Borrelia burgdorferi which causes Lyme disease

How well did you know this?

Not at all

Perfectly

Examples of bacteria that do not gram stain?

Examples
- Mycobacteria e.g. mycobacteria tuberculosis

Mycobacteria tuberculosis causes TB

Other examples
Chlamydia
Mycoplasma

How well did you know this?

Not at all

Perfectly

Structural and chemical differences between gram positive and gram negative bacteria?

Study These Flashcards

Gram-positive bacteria have cell walls consisting of thick layers of peptidoglycan, while Gram-negative bacteria have cell walls with a thin layer of peptidoglycan.

During the gram staining procedure, a gram-positive cell retains the purple-coloured stain, while gram-negative bacteria stain pink.

Gram-positive bacteria produce exotoxins, whereas gram-negative bacteria produce endotoxins.

Gram-negative bacteria cause many infections in humans.

What bacteria is the most common gram negative within the body?

Study These Flashcards

E.coli

How is infection diagnosed?

Study These Flashcards

History (hypothesise differential diagnoses)

Examination (review differential diagnoses)

Investigations (radiology, biochemistry, immunology etc) refine differential diagnoses even further

Microbiology: Blood, stool, urine, wound, tissue cultures
- Microscopy: stool, urine, CSF, sputum.
- Serology
- Antigen detection
- PCR/ molecular studies

What are the 3 classification topics for bacteria?

Study These Flashcards

Shape
- Bacilli
- Cocci
- Spirilla

Gram stain
- Gram +ve
- Gram -ve

Oxygen demand
- Aerobic
- Anaerobic

Gram negative bacteria examples?

Study These Flashcards

E.coli
Vibrio.cholera
Salmonella
Pseudomonas
Periodontal disease bacteria

Acetic acid bacteria from vinegar
Xanthomonas from xanthan gum
Zymomonas from tequila

Gram positive bacteria examples?

Study These Flashcards

Staph.aureus
Mycobacterium.tuberculosis
Enterococci
Strep.pneumoniae
Clostridium.botulinum
Haemolytic bacteria

Lactic acid bacteria from yogurt

What are some examples of bacteria that are spirochetes (spiral shaped)?

Study These Flashcards

Borrelia burgdorferi (causative agent of Lyme disease) and Treponema pallidum (causative agent of syphilis)

What is the mean inhibitory concentration (MIC)?

Concentration of drug required for kill of 99.9% of organisms during 18 to 24 hours The concentration of drug that allows a tube (or well) containing the pathogen to remain clear by visual examination after 18 to 24 hours.

What bacteria type is c.difficile?

Gram-positive, anaerobic, spore-forming, toxin-producing bacilli

How does c.difficile mainly spread?

Spores are spread by the faecal-oral route from person to person but also from the environment

Main clinical features of c.difficile infection?

Watery diarrhoea Fever Abdominal pain

Risk factors for c.difficile infection?

Antibiotic use Hospitalisation Gastric acid suppression Age >65 Co-morbidities

What are the investigations and treatment components of sepsis 6?

Investigations: - Lactate - Urine output - Blood cultures Treatments: - Oxygen - IV fluids - IV antibiotics

What is the first line antibiotic used for c.difficile in all cases?

Oral vancomycin

IV vancomycin is also useful for c.difficile infections. True/false?

False IV vancomycin is not effective

Further management of c.difficile infection after administration of oral vancomycin?

NG or PR route if oral administration is not feasible Isolate in single room with contact precautions Soap and water for hand hygiene – spores resistant to alcohol gel

What are some non-infective causes of diarrhoea?

Common non-infective causes include medication, overflow, IBD.

What are the hallmarks of infections for shiga toxin producing E.coli?

painful, bloody diarrhoea with or without fever

What is haemolytic uraemic syndrome?

Haemolytic uremic syndrome (HUS) is a rare but serious medical condition characterized by the destruction of red blood cells, acute kidney failure, and a low platelet count. It is most commonly caused by infection with certain strains of bacteria, particularly a strain of Escherichia coli (E. coli) known as O157:H7

What is the underlying pathology of haemolytic uraemic syndrome?

HUS occurs when toxins produced by certain bacteria, particularly E. coli, enter the bloodstream and cause damage to the lining of blood vessels, leading to the destruction of red blood cells, kidney damage, and a decrease in platelet count.

Management of haemolytic uraemic syndrome (HUS)?

Typically involves supportive care to manage symptoms and complications, such as maintaining hydration and electrolyte balance, managing blood pressure, and in some cases, dialysis may be necessary for kidney failure.

Are antibiotics used for treating HUS caused by E.coli infection?

No Antibiotics are generally not recommended for treating HUS caused by E. coli infection, as they can potentially worsen the condition by releasing more toxins.

What is staph aureus bacteraemia?

Staph aureus bacteremia, or Staphylococcus aureus bacteremia, is a serious bloodstream infection caused by the bacterium Staphylococcus aureus.

How does staph aureus bacteraemia occur?

Staph aureus bacteremia occurs when these bacteria get into the bloodstream, usually through a wound, surgical site, or a catheter, and spread throughout the body.

Clinical features of staph aureus bacteraemia?

Fever, chills, rapid heartbeat, and low blood pressure. Must be treated promptly to avoid complications i.e. infective endocarditis or sepsis.

Gold standard treatment for staph aureus bacteraemia?

IV flucloxacillin 2g QDS is the gold standard

What is the next best antibiotic for staph aureus bacteraemia after IV flucloxacillin if patient is penicillin allergic?

In true penicillin allergy, IV vancomycin is next best alternative - Requires TDM (drug monitoring) to ensure levels 15-20 - Higher mortality compared to flucloxacillin

Gram film interpretation Flashcards

(44 cards)