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microbiology > Medically Important Gram Positive Bacteria And Mycobacteria > Flashcards

Medically Important Gram Positive Bacteria And Mycobacteria Flashcards

1
Q

Name three examples of gram positive cocci and gram positive bacilli

A

Staphylococcus
Streptococcus
Enterococci

Clostridium species
Listeria
Corynebacterium

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2
Q

Staph appears in what form and strep appears in what form

A

Staph- clusters

Strep- chains

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3
Q

What test is used to differentiate between staph and strep

A

Catalase test

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4
Q

What test is used to differentiate between streptococci

A

Blood agar haemolysis

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5
Q

How is the catalase test done

A

It uses 3percent hydrogen peroxide
Staph are catalase positive and strep is catalase negative
If it is staph, bubbles are formed

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6
Q

A major virulence factor is staph is toxins. Name three toxins produced by staph aureus and their clinical relevance

A

Enterotoxin- induces git distress
Hemolysins- lyse red blood cells
Toxic shock syndrome toxin- induces fever, vomiting, shock,system organ damage
Exfoliating toxin- separates the epidermis from the dermis

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7
Q

Name four diseases caused by staph aureus

A

Boils
Sepsis, osteomyelitis
Food intoxication - by ingestion of enterotoxins
Staphylococcal scalded skin syndrome-toxin induces blisters then desquammation of epidermis
Toxic shock syndrome toxin(TSST)-toxemia leading to shock

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8
Q

Methicillin resistant staph aureus is not resistant to most antibiotics true or false

A

False. It is

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9
Q

Where is MSRA usually spread

A

In the hospital and it easily spreads

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10
Q

Importance of Coagulase test

A

It singles out staph aureus

If it is staph aureus, in the slide method, there is clumping

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11
Q

Samples taken to check for staph aureus

A

Blood in sepsis

Pus or fluid from boils

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12
Q

How to get check for staph aureus

A

Example
Blood sample is taken and cultured
The culture when it grows, a lab test (gram staining is done). And it’ll be Gram positive. To confirm it is a staph you do a catalase test and if it is staph, you’ll see a Gram positive cocci in clusters . If strept it’ll be Gram positive cocci in clusters . and to check what kind of staph it is you do a coagulase test to see if it is staph aureus

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13
Q

Name two types of coagulase test

A

Slide coagulase test and tube coagulase test
Slide- detects bound coagulase
Tube- detects free coagulase

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14
Q

Name some beta hemolytic organisms

A

Staph aureus and strept pyogenes
Strept agalactiae
And E coli

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15
Q

What test is used to differentiate streptococcus

A

Hemolytic pattern on blood agar

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16
Q

Strept pneumoniae is what kind of hemolytic

A

Alpha hemolytic (partial hemolysis)

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17
Q

Apart from blood agar, which other way can strept be grouped

A

Lancefield serological classification

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18
Q

According to lancefield serological grouping and blood agar, strept pyogenes is ?

A

Group A Beta Hemolytic

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19
Q

What are supparative diseases and name four supparative diseases associated with strept pyogenes

A

Supparative diseases are not complicated diseases

Examples
Sore throat (pharyngitis)
Impetigo-rashes( as opposed to boils for staph aureus)
Cellulitis
Necrotizing fasciitis
Scarlet fever is based on a toxin produced by streptococcus

20
Q

How to check for strept pyogenes

A

Do Gram staining to see if org is Positive or negative
Itll be positive
Do catalase test to check for the strept
It’ll catalase negative
Then to check for what type of strept it is, use hemolytic pattern on blood agar
To check the type of strept. If it is Beta hemolytic it is strept pyogenes
Then according to the lancefield serological classification, it is Group A

21
Q

What are Non supparative diseases with regards to strept and give two examples

A

They are complicated diseases that occur due to strept

Acute rheumatic fever- a complication related to heart diseases (carditis) . It occurs in some people who don’t take antibiotics after getting pharyngitis
Acute glomerulonephritis- a complication related to kidney diseases ( hematuria, proteinuria,high bp)

22
Q

Strept pneumoniae although isa strept and so should be in chains. That is not so, it is Rather in what form?

A

Gram positive diplococci and is capsulated.

It’s cocci are in pairs in short chains not long chains like the other strept

23
Q

Where is strept pneumoniae usually (normally )found

A

In the upper respiratory tract and when it goes down to the lungs or anywhere else apart from the upper resp tract and that’s where it causes diseases

24
Q

Name two diseases that occur when strept goes to other places apart from the upper respiratory tract and four complications that can can result

A 
Runny nose
Pneumonia causing bloody sputum 
Cold
CN cause upper resp congestion
Complications- 
Meningitis 
Bacteremia 
Sinusitis 
Otitis media
25
Q

Listeria which is a bacilli has flagella therefore it is motile true or false

A

True

26
Q

Which kind of people are usually affected by Listeria monocytogenes and name three problems caused by it

A

It causes problems in pregnant women and it is the baby that is affected

Problems- intra-uterine death( baby dies in the womb)
Early onset neonatal infection( when baby comes out and after two days has a fever)
Intermediate onset(3-5) days and gets an infection
Late onset(7-5 days and septicemia or meningitis occurs)
27
Q

How does it occur in pregnant women?

A

The women present with cold like symptoms or influenza like symptoms . When this happens, give the person antibiotics in case the woman has been infect with listeria monocytogenes so that the baby will not be affected

28
Q

How to check for listeria

A

Inoculate the test organism into the central glass tube
● Incubate at room temperature for 18-24h
● Subculture from the outer section of the medium
•Positive result: Organism can be recovered from the outer section of the medium
•Negative result: Organism remains in the inner tube

29
Q

Corynebacterium diphtheriae causes which diseases.

A

Diphtheria
Sore throat ( lymph nodes get swollen(bull neck ) ) this shows the difference between sore throat caused by this organism and sore throat caused by streptococcus pneumoniae
How to show if the organism has progressed is that the tissues in the throat will be white or black (if black it shows tissue is dead. If white the tissue is dying.A toxin is produced to destroy the cells in the throat)
Non toxin doesn’t destroy the cells but just causes the sore throat(pharyngitis)

Complications- if organism progresses into the heart it causes myocarditis and into the nerves it causes neuritis

30
Q

C diphtheriae is a vaccine preventable condition. True or false

A

True

31
Q

Which bacilli bacteria is anaerobic and spore forming(spore forms terminally )

A

Clostridium

32
Q

Clostridium tetani causes what and is found where

A

Tetanus and Is found as spores in the environment and is vaccine preventable

It is characterized as a locked jaw or difficulty in moving the jaw.
If you get knife wounds or metal wounds or car accident wounds patient on your hands clean the wound very well having tetanus in mind and if it is possible not to suture then don’t
Even if you suture , make sure you give proper antibiotics

33
Q

Diff between anti tetanus serum and tetanus vaccine

A

Anti-tetanus immunoglobulin, also known as tetanus immune globulin (TIG) and tetanus antitoxin, is a medication made up of antibodies against the tetanus toxin. (Provides passive immunity as the body doesn’t produce the antibodies)
But the tetanus vaccine will make your body immune against the tetanus so whenever it tries to enter your body it can’t enter

34
Q

Clostridium perfringens causes ?

A

Necrotizing enteritis

35
Q

How is clostridium classified as?

A

A Gram positive bacilli that is anaerobic and it’s spores are formed terminally

36
Q

Clostridium difficile causes what disease?

A

Abuse of antibiotics or antibiotics associated diarrhea

37
Q

How are bacillus species classified

A

They are Gram positive bacilli and their spores are oval shaped and centrally located)

38
Q

Which bacillus species is used for bioterrorism

A

Bacillus anthracis

39
Q

Apart from staph aureus, which other Gram positive bacteria causes food poisoning

A

Bacillus cereus

40
Q

What infections are caused by bacillus anthracis

A

Pulmonary anthrax- by inhalation of spores

Intestinal anthrax

41
Q

Name three mycobacterium diseases

A

Tuberculosis
Leprosy
Buruli ulcer

42
Q

Why doesn’t Gram staining work well on mycobacterium

A

It has modified peptidoglycan layer and has lots of layer steroids in the cell wall

43
Q

TB is not caused by only M tuberculosis but caused by each organism in the mycobacterium tuberculosis complex true or false

A

True but TB is mainly caused by M tuberculosis

44
Q

TB Is divided into two. Name them and explain

A

Pulmonary tuberculosis : bloody sputum from the lungs

Extra pulmonary tuberculosis : when it affects anywhere else apart from the lungs example spine or brain

45
Q

How is pulmonary TB diagnosed

A
  1. Molecular techniques
    Using Gene Xpert . Sputum is the sample used
    Advantages of Gene Xpert- High sensitivity
    It takes 2 hours. It shows if the Sputum sample is drug resistant or not
    Does not put health worker at risk
    It requires one sputum sample

Limitation- it works only on sputum sample so you cannot test for TB if you suspect Extra Pulmonary TB cuz the sample for EPTB is not sputum
If the person has a lot of blood in the sputum , Gene Xpert will read the sample as invalid
Gene Xpert cartridge does not last for so long
It detects only M tuberculosis and not the other pathogens in the M tuberculosis complex

  1. Microscopy
    Acid fastness: Ziehl -Nielsen , Auramine staining (fluorescent microscope which has a dark background )
    Auramine is better cuz it is easier to identify the pathogens if present due to the dark background while the pathogens are illuminated

Disadvantages- A lot of training is needed to process it so it puts the health worker at risk
There is low sensitivity - cuz the microscope may not be good enough to see the pathogens , your eyes may not be good enough to see the pathogens so you can easily get a negative result even when the pathogens are present
It takes longer

  1. Culture: not everyone needs the culture . It is needed when Gene Xpert is not able to detect the pathogen causing the TB because the pathogen causing the TB is not M tuberculosis . So when the result comes out as negative but the person has all the symptoms of TB then you do culture to be extra sure
    Culture allows the organism to grow so whichever species of TB is there grows in numbers and is identified. It has high sensitivity. Also if the TB is drug resistant a culture is used to different TB medications to check which the sample is resistant to or sensitive to
    It takes a very long time
    It puts the healthworker at risk

Immunological test: example mantoux test or Heaf test
Mantoux test: everyone that has taken TB vaccine , the result will come out as positive
So I’m a setting like this, immunological test cannot be used
But if getting samples is problematic then Mantoux test is used to support your diagnosis or suspicions. Example- cervical TB you can’t take sputum sample
Procedure: inject purified protein derivatives into the skin and check for the appearance of induration. Everyone vaccinated w TB there will be an induration formed but the size won’t be big as that if someone with TB
The size of the induration will show if it is TB or not

46
Q

M ulcerans causes buruli ulcer. How are the wounds managed?

A

It is managed surgically
In a very short time the wound becomes very big like three days
The infected place must be scraped off if the infection has not crossed joints
Wound can be covered after surgical debridement by grafting from the thigh

microbiology (9 decks)

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