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ID study > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Mechanisms of resistance (AMR) (4)

A
  1. Impermeable outer wall
  2. Efflux pumps
  3. Alter target
  4. Destroy/modify compound
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2
Q

Strategies for reducing AMR in general? (6)

A

Reduce disease
1. Improve sanitation
2. Vaccination
3. Indirect effects e.g. improving overall health –> reduce hospitalisations –> reduce hospital acquired infections/less likely to receive antibiotics
4. IPC
Reduce inappropriate use of antibiotics
5. Tackle agricultural use
6. Improve diagnostics
7. Patient/prescriber interaction

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3
Q

Plague - bacteria

A

Gram negative rod - Yersinia pestis, Yersinia enterocolitica, Yersinia pseudotuberculosis
Extracellular (can be seen on blood film with bipolar appearance i.e. the ends of the bacteria stain more intensely than the middle)
Non lactose fermenting

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4
Q

Plague - clinical forms

A

Bubonic
Septicaemia
Pneumonic

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5
Q

Plague - transmission

A
  1. Vector borne - carried by fleas (xenopsylla cheopis)
  2. Droplet contact - coughing/sneezing
  3. Direct physical contact - contact with pus including sexual and unsafe burial practices
  4. Indirect contact - e.g. soil
  5. Airborne transmission
  6. Faecal-oral
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6
Q

Plague - clinical features

A

Incubation 1-7 days
Buboes - tender, smooth, inflamed lymp nodes related to the site of the flea bite
Septicaemia - multi-organ failure, DIC, may progress to peripheral gangrene
Rapidly progressive pneumonia (2-4 days)

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7
Q

Plague - diagnosis

A

Microscopy and staining and/or culture:
1. Lymph node aspirate
2. Blood cultures - may be seen in blood smears or cultured
3. Sputum/bronchial/tracheal washings cultures
Rapid tests available for endemic areas (F1 antigen testing)

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8
Q

Plague - treatment and PrEP/PEP

A

Pneumonic/septicaemic
- Aminoglycosides, fluroquinolones
Bubonic
- Aminoglycosides, doxycycline, fluroquinolones
Meningitis
- Chloramphenicol, moxifloxacin

PrEP - Doxycycline/Co-trimoxazole 7 days
PEP - Doxycycline/co-trimoxazole

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9
Q

Meliodosis - bacteria

A

Burkholderia pseudomallei
Gram negative bacillus, oxidase positive, environmental saprophyte (likes to decay things)

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10
Q

Meliodosis - risk factors for diseases (3)

A

Diabetes, renal failure, steroids

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11
Q

Meliodosis - clinical features (9)

A
  1. CNS - encephalomyelitis, brain abscess
  2. CVS - bacteraemia, pericarditis, mycotic aneurysm
  3. Urinary tract - pyelo, kidney abscess, prostatic abscess
  4. Head & neck - Parotid abscess (common in children), lymphadenitis
  5. Respiratory system - pneumonia, pulmonary abscess, pleuritis
  6. GI - Liver abscess, splenic abscess, para-intestinal mass
  7. Skin and soft tissue - Skin ulcer, skin abscesses
  8. MSK - Septic arthritis, myositis, OM
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12
Q

Meliodosis - diagnosis

A
  1. *Culture (hazard 3 organism) - slow growing with distinctive crinkled appearance on agar
  2. Serology but issues with sens/spec (false positives an issue in endemic regions)
  3. PCR
  4. Antigen detection
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13
Q

Meliodosis - treatment

A
  1. Intensive phase > 2 weeks IV ceftazidime/carbapenem
  2. Eradication phase > 12 weeks oral co-trimoxazole
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14
Q

Scrub typhus - bacteria

A

Orientia tsutsugamushi (gram negative bacilli)

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15
Q

Scrub typhus epidemiology

A

Primarily in the “tsutsugamushi triangle” (Asia-Pacific region), including Southeast Asia, India, Northern Australia, and parts of China and Japan.

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16
Q

Scrub typhus - clinical presentation

A

Non-specific - fever, headache, lymphadenopathy, nausea and vomiting
Painless eschar often diagnostic
Complications include meningoencephalitis, ARDS and hepatitis

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17
Q

Scrub typhus -transmission

A

Bite of infected chiggers (larval stage of trombiculid mites)

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18
Q

Scrub typhus - treatment

A

Doxycycline and/or azithromycin

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19
Q

Scrub typhus - investigations

A
  1. Indirect Immunofluorescence Assay (IFA): Gold standard for diagnosis, detects Orientia tsutsugamushi-specific antibodies.
  2. Enzyme-Linked Immunosorbent Assay (ELISA): Commonly used and highly sensitive for detecting IgM antibodies.
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20
Q

Leptospirosis - definition

A

Zoonosis Leptospira - sprirochaete bacterium
Indirect or direct contact with urine from infected animals like rats

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21
Q

Leptospirosis - diagnostics

A

Gold standard: Serology - MAT/ELISA
Urine + blood - PCR
Culture - takes ages
ALT rise
AKI
Thrombocytopenia
Rhabdo

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22
Q

Leptospirosis - clinical presentation

A

Acute: Fever, rigors, myalgia, headache, conjunctival suffusion

Immune phase: Aseptic meningitis, jaundice, renal failure, pulmonary haemorrhage

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23
Q

Leptospirosis - Treatment

A

PO doxycycline or azithromycin
Severe: IV penicillin or ceftriaxone

N.B jarish-herxheimer reaction to antibiotics

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24
Q

Acute rheumatic fever

A

Acute multisystem, inflammatory process occuring 2-3 weeks after infection with group A strep

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25
Q

Group A strep - bacteria

A

Streptococcus pyogenes - beta haemolytic cocci in chains

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26
Q

Acute rheumatic fever - clinical symptoms

A

Joint pain (not deforming, responds to NSAIDs)
Carditis (MV –> AV)
Chorea
Erythema marginatum
Fever
SC nodules

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27
Q

Acute rheumatic fever - management

A

Suppressive abx
NSAIDs/analgesia

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28
Q

Tetanus - organism

A

Clostridium tetani - anaerobic gram positive bacilli (drumstick appearance)
Toxins are Tetanolysin and tetanospasmin

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29
Q

Tetanus - pathophysiology

A

Toxins bind to receptors on inhibitory interneurons like GABA, therefore toxin causes sustained muscle spasms

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30
Q

Tetanus - clinical features

A

Muscle stiffness, spasms, autonomic dysfunction
Cardiovascular instability, fever, voice change

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31
Q

Tetanus - treatment including supportive care (8)

A
  1. Toxin removal - wound debridement
  2. Antibiotics - metronidazole
  3. Antitoxin (intrathecal or IM, human or equine)
  4. Control muscle spasms - Mg and benzodiazepines
  5. Airway support - tracheostomy and secretion management
  6. Mechanical ventilation
  7. Autonomic support - Mg and cooling
  8. Cardiovascular support
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32
Q

Enteric fever - definition

A

Salmonella typhi and paratyphi
Gram negative bacilli

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33
Q

Enteric fever - transmission

A

Faecal oral

34
Q

Enteric fever - clinical presentation

A

Fever, abdo pain, headache, cough, myalgia
Constipation –> diarrhoea
Hepatosplenomegaly
Relative bradycardia

35
Q

Enteric fever - diagnostics

A

Blood culture
Stool culture
Bone marrow to be considered in severe disease and diagnostic uncertainty

36
Q

Enteric fever - complications

A

Sepsis, perforation, bleeding, typhoid spine, cholangiocarcinoma

37
Q

Enteric fever - management (including considering resistance patterns)

A

MDR ACT (Ampicillin, Chloramphenicol, co-Trim)
Treatment: Ciprofloxacin/ceftriaxone

FDR FACT (fluoroquinolone R)

XDR (quinolones, 3rd gen cephalosporins)
Treatment: Macrolide + carbapenems

38
Q

Enteric fever resistance patterns

A

MDR is ACT
Ampicillin, Chloramphenicol, co-Trimoxazole

FDR is FACT Fluoroquinolones and ACT

XDR e.g. Pakistan
Quinolones, 3rd gen cephalosporins and FACT

39
Q

AMR Intrinsic resistance

A

Lacks antibiotic target - transmitted by the organism

40
Q

Acquired resistance

A

Point mutations: altered target, random errors during replication
Acquisition of resistance gene through plasmid, bacteriophage or transposons

41
Q

Cholera - pathogen

A

Vibrio cholerae
Gram negative facultative aerobe rod
Toxin mediated

Serotype O1: all recent outbreaks but also O139

42
Q

Cholera treatment and prevention

A

Rehydration sachets
Zinc for <5 years
Can give doxycycline in severe cases

Vaccination (oral) in two doses

43
Q

Bartonella - organism

A

Gram negative intracellular bacteria

44
Q

Carrion’s disease - organism and vector and geographical distribution

A

Bartonella bacilliformis
Sandfly
Andes

45
Q

Bartonella bacilliformis (Carrion’s disease) clinical presentation

A

Acute phase:
Haemolytic anaemia
Fever
Bacteraemia
Risk of superinfections like Toxo, salmonella and histoplasma

Chronic phase:
Blood filled nodiles
Verrucas or peruvian warts
Miliar

46
Q

Bartonella henselae - disease

A

Cat scratch disease

47
Q

Bartonella henselae - clinical features

A

Immunocompetent: Lymphadenopathy and fever

Immunocompromised: Bacillar angiomatosis (vascular lesions), parinaud’s oculoglandular syndrome

48
Q

Bartonella henselae - treatment

A

Azithromycin 5 days
Alternatives clari/rif

49
Q

Trench fever - organism

A

Bartonella quintana

50
Q

Batonella quintana - vector

A

Human body louse

51
Q

Bartonella quintana - risk factors

A

Homeless
HIV
IVDU
Alcohol abuse

52
Q

Bartonella quintana - treatment

A

Doxycycline

Prolonged doxycycline in bacillary angiomatosis and endocarditis

53
Q

Rickettsial infection - organism

A

Gram negative intraceullar coccobacilli bacteria

Does not culture
Does not gram stain
See on a giemsa stain

54
Q

Rickettsial infections - generalised key clinical symptoms

A
  1. Incubation 6-14 days
  2. Fever + eschar + rash

Severe cases: vasculitis end organ damage - particularly renal failure. DIC.

55
Q

Rickettsial diseases - diagnostics

A

Gold standard is serology - indirect immunofluorescence IgG on paired serum samples

56
Q

Rickettsial diseases - treatment

A

Doxycycline

Alternatives - macrolides, chloramphenicol, fluoroquinolones

57
Q

Scrub typhus - organism, epidemiology and vector

A

Orientia tsutsugamushi
Worldwide
Trombiculid mite

58
Q

Epidemic typhus - organism, epidemiology and vector

A

Rickettsia prowazekii
Worldwide
Louse faeces

59
Q

Murine typhus- organism, epidemiology and vector

A

Rickettsia typhi
Worldwife
Flea faeces

60
Q

Rocky mountain spotted fever- organism, epidemiology and vector

A

Rickettsia rickettsii
USA
Tick - dermacentor variabilis, american dog tick

61
Q

African tick bite fever- organism, epidemiology and vector

A

Rickettsia africae
Africa + caribbean
Tick - ambylomma

62
Q

Rickettsia pox- organism, epidemiology and vector

A

Rickettsia akari
Worldwide
Mite - liponssoides sanguines

63
Q

Mediterranean spotted fever- organism, epidemiology and vector

A

Rickettsia conorii
Europe, Africa, Asia
Tick Rhipicephalus

64
Q

Name two rickettsial conditions that have mites as vectors

A

Orientia tsutsugamushi (scrub typhus)
Rickettsia akari (rickettsia pox)

65
Q

Name a rickettsial condition that has louse as vector

A

Rickettsia prowazekii (epidemic typhus)

66
Q

Name a rickettsial condition that has flea as vector

A

Rickettsia typhi (murine typhus)

67
Q

Name three rickettsial conditions that have ticks as vectors

A

Rickettsia rickttsii (Rocky mountain spotted fever)
Rickettsia africae (African tick bite fever)
Rickettsia conorii (Mediterranean spotted fever)

68
Q

Which three rickettsial diseases are most severe?

A
  1. Scrub typhus (orientia tsutsugamushi)
  2. Epidemic typhus (rickettsia prowazekii)
  3. Rocky mountain spotted fever (rickettsia rickettsii)
69
Q

Which rickettsial disese can relapse?

A

Endemic typhus (rickettsia prowazekii) - note also has a sustained fever (not swinging)

70
Q

Which rickettsial disease can mimic a pox virus?

A

Rickettsial pox (rickettsia akari)

71
Q
A
72
Q

Q fever summary

A

Gram negative bacilli
Spread from cattle/sheep/goats to humans
High fevers, sweats, headaches, muscle and joint pain and IE
Treat with doxycycyline

73
Q

Brucellosis

A

Most common zoonosis globally
From cattle, sheep, goats and pigs
Infection through inhalation of aerosols (e.g. in slaughterhouses) or consumption of unpasteurised milk. Other forms of transmission like breast milk, sex, skin penetration is more unusual

Bacteraemia
Splenomegaly
Hepatomegaly
OM
Orchitis
Sacroilitis

Dx
Blood culture and PCR

Mx: Doxcycyline 45 days + IV aminoglycoside

74
Q

Cryptosporidium

A

Common cause of infant diarrhoea in LMIC
High risk in immunocompromised

Transmission: water-borne, food-borne, Direct contact
Watery diarrhoea

Usually self-resolves but may not in immunocompromised

Diagnosis is Stool Ziehl-Neelsen staining bright red 5-5.5 microns

Main treatment is ART, nitazoxanide

75
Q

Toxoplasma gondii life cycle

A
  1. Ingestion of oocysts or tissue cysts from contaminated food, water etc OR tissue cysts from undercooked meat
  2. Oocytes release sporozoites which convert into tachyzoites
    OR
    tissue cysts release bradyzoites which convert into tachyzoites
  3. Cat is the definitive host (sexual reproduction occurs in the intestinal lining)
76
Q

Toxoplasma gondii - clinical features

A

Asymptomatic in immunocompetent

Ocular
Congenital
Cerebral

77
Q

Toxoplasma investigations

A

Serology
PCR from blood, CSF, amniotic fluid
Neuroimaging (multiple ring-enhancing lesions)

78
Q

Bacillary angiomatosis

A

Bartonella henselae/quintana
Vascular skin lesions

79
Q

Bartonella IE - what is it, who gets it

A

Bartonella henselae (cat scratch)
Bartonella quintana (human body louse)

In severe immunosuppresison
Often culture negative

Doxycycline + rifampicin

80
Q

Bartonella diagnostics

A

Serology (moderate sensivitiy), PCR (high sensitivity)
Culture (low sensivity)
Biopsy and staining in bacillary angiomatosis for vascular lesions

81
Q

Bacillus anthracis

A

Anthrax
Gram positive rod
Exposed to infected animals
Cutaneous (95%), GI, inhalational disease
Painless ulcer which becomes odoematous

ID study (22 decks)

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