Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MBBS IV - Junior Clerkship WCS > JC87 (Microbiology) - Medically important microbes > Flashcards

JC87 (Microbiology) - Medically important microbes Flashcards

1
Q

Outline the classification scheme for gram positive cocci

A

Gram positive rods

Gram positive cocci:

  • Catalase positive GPC in clusters - Staphylococcus sp.
  • Catalase negative GPC in chains - Streptococci and Enterococcus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

S. aureus

List types of infections

A

Infections:

  • Skin/ soft tissue
  • Abscesses
  • Native or prosthetic joint septic arthritis
  • Osteomyelitis
  • Pneumonia
  • Infective endocarditis
  • Endovascular infection
  • Surgical site infection

Toxin-mediated:

  • Food poisoning by staphylococcal enterotoxin
  • Toxic shock syndrome
  • Scalded skin syndrome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

4 subtypes of S. aureus with varying antibiotics resistance

List the antibiotics resistance

A

MSSA: Sensitive to most B-lactams

HA- MRSA: Resistant to B-lactams and others e.g. clindamycin

CA- MRSA (may carry PVL toxin for necrotizing infection): Resistant to B-lactams, less resistant to non-B-lactams e.g. clindamycin

VISA/ VRSA: Immediate or full resistance to glycopeptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Antibiotics of choice for MSSA, MRSA, VRSA

A

MSSA: Cloxacillin

HA- MRSA: Vancomycin, Linezolid, Daptomycin, Ceftaroline

CA-MRSA: Vancomycin, Linezolid, Daptomycin, Ceftaroline + any susceptible antibiotics

VISA/VRSA: Linezolid, Daptomycin, Ceftaroline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Function of coagulase test for gram positive cocci?

A

Catalase positive GPC in clusters:

  • Coagulase positive = S. aureus
  • Coagulase negative = Staphylococci spp.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Coagulase negative staphylococcus

  • Nature source of bacteria
  • Infections
  • Collection method
A

Natural skin commensals, benign

Exceptions:

  • Genuine infection of prosthesis
  • S. saprophyticus = UTI
  • S. lugdunensis = Virulent
  • S. epidermidis = prosthesis/ catheter-related infection

Collection:
Take at least two sets of blood culture if GPC in clusters
Single blood culture isolate may be contamination due to improper blood taking technique

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Alpha hemolytic streptococci

Types of infection caused by Strep. pneumoniae

A

Streptococcus pneumoniae

Pneumonia 
Meningitis 
Otitis media 
Sinusitis 
Septicaemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

List 5 medically important alpha-hemolytic streptococci

List infections these cause

A
  1. Streptococcus pneumoniae: pneumonia, meningitis, otitis media, sinusitis, speticaemia
  2. Viridans streptococci- infective endocarditis, dental carries, oral infections
  3. Streptococcus anginosus/ S. milleri - Abscess formation in abdominal, pelvic cavities
  4. Streptococcus bovis - bacteremia, IE, GI malignancies (CRC)
  5. Streptococcus suis - meningitis, bacteremia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which alpha-hemolytic streptococcus is related to colorectal cancer and IE

A

Strep. bovis

Major biotype in HK is type 2, associated with cholangitis
Biotype 1 is associated with IE and CRC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Beta-hemolytic streptococci

S. pyogenes infections

A

S. pyogenes (GAS in Lancefield grouping)

  • Local skin Infections: impetigo, cellulitis, necrotizing fasciitis
  • Respiratory: pneumonia, pharyngitis
  • Systemic infections: Toxic shock syndrome, Scarlet fever, lymphadenitis
  • Post-infectious syndrome: PSGN, acute rheumatic fever
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Outline scheme for differentiating Catalase negative GPC/ Streptococci spp.

A

First: Alpha/ Gamma hemolysis or Beta hemolysis pattern

Alpha/ Gamma group:

  • Optochin susceptible and bile soluble, PYR +ve and VP -ve = Streptococcus pneumoniae
  • Optochin resistant and bile Insoluble = Viridans streptococci, Strep. bovis and Enterococci

Beta groups:
- Lancefield grouping, Bacitracin susceptibility, Biochemical reactions
GAS = Strep. pyogenes
GBS (Bacitracin resistant, CAMP _ve, Hippurate hydrolysis +ve) = Strep. agalactiae
GCS or GGS = Strep. dysgalactiae
Streptococcus anginosus group/ Strep. milleri

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Virulent mechanisms of group A strep.

A

Invasion and spread through tissue via Streptokinase, Hyaluronidase

Systemic toxin: Streptolysin O, superantigen and other Streptococcal pyrogenic exotoxins

Anti-phagocytosis and adhere to epithelial cells/ mucosa : M protein, capsule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Scarlet fever

  • Presentation
A

Rash:

  • Facial flushing with peri-oral pallor
  • Diffuse, centrifugally spreading rash over face and upper chest
  • Blanchable

Strawberry tongue

Eosinophilia

Preceding pharyngitis or any GAS infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Diagnostic criteria of Streptococcal toxic shock syndrome

Treatment options

A

Lab: Isolation of Group A Streptococcus

Clinical: 
- Hypotension 
- Multiorgan involvement with at least 2 of 
Renal impairment 
Coagulopathy 
Liver involvement 
ARDS 
Generalized, erythematous macular rash 
Soft tissue necrosis

Tx: Penicillin + Clindamycin or linezolid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Diagnostic criteria for acute rheumatic fever

A 
Jone's criteria 
Major: 
- Carditis 
- Arthritis 
- Sydenham's chorea 
- Subcutaneous nodules 
- Erythema marginatum

Minor:

  • Fever
  • Arthralgia
  • High ESR or CRP
  • Long PR interval

Supportive:

  • High Anti-streptolysin O titer (ASO)
  • Positive throat culture for GAS

Dx: 2 major or 1 major + 2 minor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Treatment of acute rheumatic fever

A

Penicillin x 10 days
Anti-inflammatory: Aspirin, Corticosteroids
Surgery for mitral valve involvement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

S. agalactiae infections

Biochemical tests

A

S. agalactiae (GBS in Lancefield grouping)&raquo_space;> Raw fish!
Major infections: Meningitis, Pneumonia, Sepsis, Skin, Septic arthritis, Osteomyelitis, Female genital tract infections

  • Neonatal sepsis, meningitis, peripartum infections , pneumonia
  • Pregnant women: UTI, genital tract infection, placenta infection, post-partum sepsis
  • Elderly/ immunocompromised: skin infection, septic arthritis, osteomyelitis, pneumonia, endocarditis, meningitis, sepsis

Bacitracin resistant
CAMP positive
Hippurate hydrolysis positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

S. dysgalactiae Infections

Biochemical tests

A

Infections: Very similar to S. agalactiae
Same as S. agalactiae: Meningitis, Pneumonia, Sepsis, Skin infection, Septic arthritis, Osteomyelitis
Add-on: Pharyngitis, PSGN, Endocarditis
No pregnancy/ female genital infections

Lancefield group C/G
Bacitracin resistant
PYR -ve
VP -ve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

S. anginosus/ S. milleri

Infections
Biochemical tests

A

Abscess formation
- Dental, brain, liver, pelvic, lung, empyema
Endocarditis
Bacteremia in neutropenic patients - ARDS, Toxic shock

Bacitracin resistant
PYR -ve 
VP +ve
Alpha/ Gamma hemolysis 
Lancefield non-groupable

(Caramel smell)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Viridans streptococci

Source of bacteria
Types of infections

A

Common oral flora

Infections:
Dental carries
Infective Endocarditis

Bacteremia in neutropenic patients
Meningitis
Pneuomonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Enterococci

Examples
Lancefield grouping and special biochemical tests, growth environment
Types of infections

A

Example: E. faecium and E. faecalis

Lancefield group D
Grows in 6.5% NaCl and 40% bile salt (similar to gut environment)
PYR +ve, Hydrolyzes bile esculin

Normal gut flora, causes mainly opportunistic infections

-Catheter-associated UTI, Line sepsis
-Endocarditis
- Component of polymicrobial intra-abdominal/ biliary infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Outline the classification scheme for gram positive rods

A

Aerobic GPR: BCLNM

  • Bacillus
  • Corynebacterium
  • Listeria monocytogenes
  • Norcardia, Rhodococcus
  • Mycobacteria: MTB complex and non-tuberculosis mycobacteria

Anaerobic GPR:

  • Spore forming: Clostridium spp.
  • Non-spore forming
23
Q

Bacillus spp.

List examples and types of infection
Source of bacteria

A

Widely distributed in environment

B. anthracis = anthrax
B. cereus = Food poisoning (rice products)

Bacillus in blood culture is most likely contamination

24
Q

Listeria monocytogenes

Source of bacteria
Types of infections
Antibiotic resistance
Tx

A

Source: Milk, Chicken and poultry products

Infections:

  • Neonatal meningitis and pregnancy infections
  • CNS infections in elderly/ immunocompromised
  • Resistant to cephalosporins, sensitive to ampicillin

Tx: Ampicillin, (ceftriaxone)

25
Q

Corynebacterium

Example
Type of infection
Presentation
Source of bacteria

A

Respiratory and cutaneous diphtheria infection

Sore throat with grey pseudo-membrane in oropharynx
Cervical lymphadenopathy, toxin-mediated cardiac and neurological complications

Source: Skin, oral mucosal commensals, mostly cause opportunistic infections

26
Q

Nocardia and Rhodococcus

  • Type of infection
  • Biochemical test
A

Infection: Opportunistic infection, chronic in immunocompromised pt.

Test: Weakly/ Modified acid-fast

Nocardia: Pulmonary abscess, CNS abscess and cutaneous nocardiosis
(Lung and brain abscess > think Nocardia)

Rhodococcus: Pneumonia, lymphadenopathy, wound infections
(Zoonotic)

27
Q

List anaerobic gram positive rods and related infections

A

Spore-forming; Clostridium spp.

  • C. perfringens: gas gangrene, food poisoning, biliary sepsis
  • C. tetani: tetanus
  • C. botulinum: Botulism
  • C. difficile: Pseudomembranous colitis, Antibiotics associated diarrhea

Non-spore forming: Actinomyces

  • GI and genital tract colonizer
  • Pelvic (IUCD use), abdominal, cervicofacial actinomycosis
  • Infection across tissue planes, invasive
28
Q

Outline classification scheme for Gram negative bacteria

A

Gram negative rods
- Anaerobes: oral flora - Fusobacterium; Gut flora - bacteroides
- Aerobes/ facultative anaerobes: Enterobacteriaceae, Vibrionaceae, Non-fermenters
- Other Aerobes: e.g. H.influenzae, Legionella pneumophilia, Campylobacter, H. pylori, HACEK group, brucella

Gram negative cocci
- Neisseria
- Moraxella catarrhalis

29
Q

Enterobacterales

List examples under this group

A

Think inflammatory gastroenteritis:
E. coli
Klebsiella
Proteus
Enterobacter
Citrobacter
Morganella
Serratia
Salmonella
Shigella
Yersinia
~~~

30
Q

Enterobacterales

Types of infections

A

UTI
Inflammatory Diarrhoea syndromes: E.coli, Non-typhoidal salmonella, shigella
Specific syndromes: Bacillary dysentry (Shigella), Typhoid fever (Salmonella typhi/ paratyphi)

31
Q

Enterobacterales

Antibiotics resistant subtypes

A

ESBL-producers = resistant to B-lactams except carbapenems, so use carbepenems!

CPE (Carbapenemase-producing Enterobacteriaceae) = Resistant to carbapenems

32
Q

Vibrionaceae

Examples and related infections
Biochemical tests

A

Vibrio:

  • V. cholerae: Cholera epidemics (O1, O139); Watery diarrhea (Non-O1, Non-O139)
  • V. vulnificus: Necrotizing fasciitis
  • V. parahaemolyticus: Food poisoning

Aeromonas
Plesiomonas

Tests: Glucose fermenters, oxidase positive

33
Q

List non-fermenters and related infections

A

Most are environmental

- Pseudomonas aeruginosa
- Acinetobacter baumannii
- Stenotrophomonas maltophilia
- Burkholderia cepacia complex

Nosocomial infections: pneumonia, wound infections, prosthesis-related

Chronic infection e.g. P. aeruginosa, Burkholderia spp. in cystic fibrosis pt.

Burkholderia pseudomallei = cause of severe community-acquired pneumonia and bacteremia

34
Q

Anaerobic gram negative rods

Source of bacteria
Type of infection
2 examples

A

Normal flora in oral cavity and GIT
Causes polymicrobial infections and abscess

  • Fusobacterium spp.: Lemierre’s disease (IJV thrombophlebitis; - high fever with acute neck pain), Brain abscess
  • Bacteroides fragilis: GI colonizer, complicated intra-abdominal infections
35
Q

Gram negative cocci

Examples and related infections

A
36
Q

List bacteria that are unculturable/ unstainable by gram smear

A
  1. Spirochaetes:
    - Treponema pallidum (Syphilis)
    - Borrelia recurrentis (recurring fever)
    - Borrelia burgdorferi (Lyme disease)
    - Leptospira (Leptospirosis)
  2. Mycoplasma and Ureaplasma
  3. Chlamydia and Chlamydophilia (STD)
  4. Coxiella burnetii (Q fever)
  5. Bartonella quintana (Trench fever) and B. henselae (Cat-scratch disease)
  6. Rickettsia spp. and Orientia tsutsugamushi: Typhus, spotted mountain fever
37
Q

Fungi

Classification and examples

A

Yeast - unicellular

  • Candida
  • Cryptococcus
  • Trichophyton
  • Malassezia

Mould - Pro-mycelial

  • Dermatophytes
  • Aspergillus
  • Zygomycetes
  • Fusarium

Dimorphic fungi

Pneumocystis jiroveci

38
Q

Candida spp

Type of infection
Examples according to sensitivity to Azoles

A

Mucosal candidiasis, Thrush, systemic infection in immunocompromised and ICU pt.

Azole sensitive:

  • C. albicans
  • C. parapsilosis

Azole resistant:

  • C. krusei
  • C. glabrata
  • C. auris
39
Q

Types of infection caused by crytococcus, trichosporon, malassezia

A

All yeasts cause opportunistic infections in immunocompromised

Cryptococcus: opportunistic meningitis, opportunistic pneumonia, systemic infections in immunocompromised

Trichosporon spp: piedra, systemic infection in immunocompromised

Malassezia: pityriasis versicolor, systemic infection

40
Q

Moulds

List examples and types of infection

A

Dermatophytes: Tinea pedis, Tinea cruris, Tinea corporis, Onychomycosis

  • Trichophyton spp.
  • Microsporum spp.
  • Epidermophyton floccosum

Severe systemic infections in immunocompromised:
Aspergillus:
- A. fumigatus
- A. falvus
- A. niger
Zygomycetes: Rhizopus spp. Mucor
Fusarium: F. solani, F. oxysporum

41
Q

Examples of dimorphic fungi

A

Sporothrix schenckii

Blastomyces dermatitidis

Histoplasma capsulatum

Penicillium marneffei

42
Q

Examples of fungal disease according to skin layers

A

Superficial mycoses: Tinea, Onychomycosis (thrush), Cutaneous candidiasis, Pityriasis verisolor

Subcutaneous mycoses: mycetoma (gardener)

Deep mycoses

43
Q

3 classes of parasites and examples

A
44
Q

List viruses with high propensity to cause lower respiratory tract illness

A

Decreasing propensity to cause LRTI

Rhinovirus/ Enterovirus
Coronavirus
Parainfluenza (CROUP or bronchoiolitis)

45
Q

List viruses that cause URTI

A 
Bocavirus 
Adenovirus 
Influenza A,B (URTI or bronchiolitis)
Enterovirus D68
Rhinovirus
46
Q

Viruses that cause hepatitis

A

Hepatitis A virus, HBV, HCV, HDV, HEV

cytomegalovirus (immunocompromised), primary EBV (also causes infectious mononucleosis),
primary HHV-6 (human herpesvirus), adenovirus,
enterovirus

47
Q

Viruses that cause gastroenteritis

A

Rotavirus (children, vaccine-preventable), Norovirus (any age group), Sapovirus, Adenovirus, Astrovirus

Others:
Hepatitis A virus, CMV, Coronavirus, HIV, Influenza, Torovirus, Aichi virus, Picobirnavirus, Bocavirus

48
Q

Viruses that cause meningoencephalitis/ encephalopathy

A

Herpes simplex virus (HSV) and Other herpesviruses: Primary EBV, Primary CMV, Primary HHV-6

Varicella zoster virus (VZV)

Exanthematous disease viruses: Measles (but mainly cough, rash), rubella, parvovirus B19

Japanese encephalitis (JE), Animal contact: Rabies, Herpes B, LCMV, Hendra, Nipah

Enterovirus

Influenza-associated encephalopathy: Influenza, adenoviruses

49
Q

First-line investigation for viral meningoencephalitis

A 
 Brain scans (CT/MRI)
 Lumbar puncture
 PCR for specific viral pathogens
 Antibodies against specific viral pathogens
 Electroencephalogram
50
Q

Viruses that cause myocarditis

A 
 Adenovirus
 Enterovirus
 HSV/ VZV
 Cytomegalovirus
 Influenza
51
Q

4 viral rashes

A

Chickenpox:
 Varicella zoster virus: reactivation as herpes zoester/ shingles

Measles

Rubella

Enterovirus

Parvovirus B19: ‘slapped cheek rash’, ‘fifth disease’

HHV-6: Roseola infantum

52
Q

Arboviruses

Examples and related infections

A

 Japanese encephalitis (JE): meningoencephalitis

 Dengue (登革熱): hemorrhagic fever if severe

 Zika (Zika infection during pregnancy - microcephaly)

 West Nile virus: meningoencephalitis

 Yellow Fever virus

53
Q

Major cancers associated with viral infections

A

Nasopharyngeal carcinoma, lymphoma: Epstein-Barr virus (EBV)

Hepatocellular carcinoma: Hepatitis B virus (HBV), HCV

Cervical cancer, anal cancer, oropharyngeal cancer: 
Human papillomavirus (HPV), high-risk genotypes (16, 18)
54
Q

Transmissible spongiform encephalopathies

Pathogenesis
Causative pathogen
Types

A

proteinaceous infectious particle (no DNA or RNA):
 Autocatalytic conversion of normal prion protein to abnormally folded prion protein: Chain reaction: PrPC&raquo_space; PrPSc
 Accumulation of abnormal prion protein causes spongiform changes and vacuolation in the
brain (looks like cheese)&raquo_space; fatal, no effective treatment

Types of TSE:
- Sporadic CJD (sCJD)
- Variant CJD (vCJD):Transmission of BSE (bovine spongiform encephalopathy) agent from cows to
humans (consumption of beef)
- Iatrogenic CJD (iCJD): prion exposure due to surgical procedures and blood transfusion
(vCJD)
- Genetic CJD (gCJD)

MBBS IV - Junior Clerkship WCS (131 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions