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Microbiology Flashcards

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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 CNS commonly (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

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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
Group A strep - bacteria
Streptococcus pyogenes - beta haemolytic cocci in chains
26
Acute rheumatic fever - clinical symptoms
Joint pain (not deforming, responds to NSAIDs) Carditis (MV --> AV) Chorea Erythema marginatum Fever SC nodules
27
Acute rheumatic fever - management
Suppressive abx NSAIDs/analgesia
28
Tetanus - organism
Clostridium tetani - anaerobic gram positive bacilli (drumstick appearance) Toxins are Tetanolysin and tetanospasmin
29
Tetanus - pathophysiology
Toxins bind to receptors on inhibitory interneurons like GABA, therefore toxin causes sustained muscle spasms
30
Tetanus - clinical features
Muscle stiffness, spasms, autonomic dysfunction Cardiovascular instability, fever, voice change
31
Tetanus - treatment including supportive care (8)
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
32
Enteric fever - definition
Salmonella typhi and paratyphi Gram negative bacilli
33
Enteric fever - transmission
Faecal oral
34
Enteric fever - clinical presentation
Fever, abdo pain, headache, cough, myalgia Constipation --> diarrhoea Hepatosplenomegaly Relative bradycardia
35
Enteric fever - diagnostics
Blood culture Stool culture Bone marrow to be considered in severe disease and diagnostic uncertainty
36
Enteric fever - complications
Sepsis, perforation, bleeding, typhoid spine, cholangiocarcinoma
37
Enteric fever - management (including considering resistance patterns)
MDR ACT (Ampicillin, Chloramphenicol, co-Trim) Treatment: Ciprofloxacin/ceftriaxone FDR FACT (fluoroquinolone R) XDR (quinolones, 3rd gen cephalosporins) Treatment: Macrolide + carbapenems
38
Enteric fever resistance patterns
MDR is ACT Ampicillin, Chloramphenicol, co-Trimoxazole FDR is FACT Fluoroquinolones and ACT XDR e.g. Pakistan Quinolones, 3rd gen cephalosporins and FACT
39
AMR Intrinsic resistance
Lacks antibiotic target - transmitted by the organism
40
Acquired resistance
Point mutations: altered target, random errors during replication Acquisition of resistance gene through plasmid, bacteriophage or transposons
41
Cholera - pathogen
Vibrio cholerae Gram negative facultative aerobe rod Toxin mediated Serotype O1: all recent outbreaks but also O139
42
Cholera treatment and prevention
Rehydration sachets Zinc for <5 years Can give doxycycline in severe cases Vaccination (oral) in two doses
43
Bartonella - organism
Gram negative intracellular bacteria
44
Carrion's disease - organism and vector and geographical distribution
Bartonella bacilliformis Sandfly Andes
45
Bartonella bacilliformis (Carrion's disease) clinical presentation
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
Bartonella henselae - disease
Cat scratch disease
47
Bartonella henselae - clinical features
Immunocompetent: Lymphadenopathy and fever Immunocompromised: Bacillar angiomatosis (vascular lesions), parinaud's oculoglandular syndrome
48
Bartonella henselae - treatment
Azithromycin 5 days Alternatives clari/rif
49
Trench fever - organism
Bartonella quintana
50
Batonella quintana - vector
Human body louse
51
Bartonella quintana - risk factors
Homeless HIV IVDU Alcohol abuse
52
Bartonella quintana - treatment
Doxycycline Prolonged doxycycline in bacillary angiomatosis and endocarditis
53
Rickettsial infection - organism
Gram negative intraceullar coccobacilli bacteria Does not culture Does not gram stain See on a giemsa stain
54
Rickettsial infections - generalised key clinical symptoms
1. Incubation 6-14 days 2. Fever + eschar + rash Severe cases: vasculitis end organ damage - particularly renal failure. DIC.
55
Rickettsial diseases - diagnostics
Gold standard is serology - indirect immunofluorescence IgG on paired serum samples
56
Rickettsial diseases - treatment
Doxycycline Alternatives - macrolides, chloramphenicol, fluoroquinolones
57
Scrub typhus - organism, epidemiology and vector
Orientia tsutsugamushi Triangle Trombiculid mite
58
Epidemic typhus - organism, epidemiology and vector
Rickettsia prowazekii Worldwide Louse faeces
59
Murine typhus- organism, epidemiology and vector
Rickettsia typhi Worldwife Flea faeces
60
Rocky mountain spotted fever- organism, epidemiology and vector
Rickettsia rickettsii USA Tick - dermacentor variabilis, american dog tick
61
African tick bite fever- organism, epidemiology and vector
Rickettsia africae Africa + caribbean Tick - ambylomma
62
Rickettsia pox- organism, epidemiology and vector
Rickettsia akari Worldwide Mite - liponssoides sanguines
63
Mediterranean spotted fever- organism, epidemiology and vector
Rickettsia conorii Europe, Africa, Asia Tick Rhipicephalus
64
Name two rickettsial conditions that have mites as vectors
Orientia tsutsugamushi (scrub typhus) Rickettsia akari (rickettsia pox)
65
Name a rickettsial condition that has louse as vector
Rickettsia prowazekii (epidemic typhus)
66
Name a rickettsial condition that has flea as vector
Rickettsia typhi (murine typhus)
67
Name three rickettsial conditions that have ticks as vectors
Rickettsia rickttsii (Rocky mountain spotted fever) Rickettsia africae (African tick bite fever) Rickettsia conorii (Mediterranean spotted fever)
68
Which three rickettsial diseases are most severe?
1. Scrub typhus (orientia tsutsugamushi) 2. Epidemic typhus (rickettsia prowazekii) 3. Rocky mountain spotted fever (rickettsia rickettsii)
69
Which rickettsial disese can relapse?
Endemic typhus (rickettsia prowazekii) - note also has a sustained fever (not swinging)
70
Which rickettsial disease can mimic a pox virus?
Rickettsial pox (rickettsia akari)
71
72
Q fever summary
Gram negative bacilli Spread from cattle/sheep/goats to humans High fevers, sweats, headaches, muscle and joint pain and IE Treat with doxycycyline
73
Brucellosis
Most common zoonosis globally Infection through inhalation of aerosols or consumption of unpasteurised milk Bacteraemia Splenomegaly Hepatomegaly OM Orchitis Sacroilitis Dx Blood culture and PCR Mx: Doxcycyline 45 days + IV aminoglycoside
74
Cryptosporidium
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
Toxoplasma gondii life cycle
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
Toxoplasma gondii - clinical features
Asymptomatic in immunocompetent Ocular Congenital Cerebral
77
Toxoplasma investigations
Serology PCR from blood, CSF, amniotic fluid Neuroimaging (multiple ring-enhancing lesions)
78
Bacillary angiomatosis
Bartonella henselae/quintana Vascular skin lesions
79
Bartonella IE - what is it, who gets it
Bartonella henselae (cat scratch) Bartonella quintana (human body louse) In severe immunosuppresison Often culture negative Doxycycline + rifampicin
80
Bartonella diagnostics
Serology (moderate sensivitiy), PCR (high sensitivity) Culture (low sensivity) Biopsy and staining in bacillary angiomatosis for vascular lesions
81
Bacillus anthracis
Anthrax Gram positive rod Exposed to infected animals Cutaneous (95%), GI, inhalational disease Painless ulcer which becomes odoematous
82
Neonatal tetanus prevention
- Maternal immunisation in 3rd trimester
83

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