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Infectious Disease > Bacterial Pathogens > Flashcards

Bacterial Pathogens Flashcards

1
Q

S aureus

Virulence factors

A 
Slime layer- interferes with osonophagocytosis
Coagulase : plasma clotting 
Protein A : absorbs serum IgG
Catalase: inactivates hydrogen peroxide 
Beta-lactamase : inactivates penicillin

Panton-Valentine leukocidin : increased cell permeability

Exfoliatins A & B : splits desmosome : skin separation

TSST-1 : induces production of IL-1 & TNF

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2
Q

S. Aureus food poisoning

Caused by

A

Ingestion of enterotoxin

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3
Q

Most common causes of osteomyelitis & suppurative arthritis in children

Ddx

A

S aureus

GAS
Kingella kingae

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4
Q

Dx criterion for Staph TSS

A

Major: Temp >38.8
Hypotension
Erythroderma with convalescent desquamation

Minor:
Mucous membranes involved
Vomiting, diarrhoea 
Liver enzymes 
Renal function
Muscle: CK, myalgia 
CNS
Thrombocytopenia
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5
Q

Ddx Staph TSS

A

Strep TSS
Kawasaki
Scarlet fever

Toxic epidermal necrolysis
Leptospirosis
Measles
Rocky Mountain spotted fever

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6
Q

CONS

Examples
Who affected

A

S epi
S hominis
S haemolyticus

On skin
Nosocomial infection in neonates, immunocompromised, in dwelling medical devices

S saprophyticus
UTI

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7
Q

CONS

Virulence

A

Low virulence- need another factor

Biofilm, adhesion to foreign body

Indolent in older children

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8
Q

Most common cause of nosocomial Bacteraemia

A

CoNS

Usually in association with CVL

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9
Q

CoNS

Rx

A

Most resistent to methicillin
Rx Vancomycin

S saprophyticus usually sensitive to 1st gen cephalosporin

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10
Q

Strep pneumoniae

Gram stain
Most frequent cause of
Colonisation rates
Children at increased risk

A

Gram + encapsulated diplococcus
Bacterial Meningitis, Bacteraemia, pneumonia, OM
90% 6mo to 5y colonised at some point

SCD, asplenia, deficiency in humoral immunity, deficiency in complement mediated immunity, HIV, CHD, nephrotic syn, leukaemia & lymphoma
* Influenza

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11
Q

Indication for Amoxicillin in pneumonia

A 
Previously healthy
Fully immunised
Infants & preschool children 
Uncomplicated 
CAP
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12
Q

Consider mycoplasma pneumoniae in

A 
School age child 
Insidious onset of Sx
Wheeze
Headache 
Myalgia
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13
Q

Scarlet fever

Cause
Features

A

URTI
pyrogenic exotoxin

Rash onset 24-48h after urti
Begins around neck
Diffuse, finely papular erythematous eruption
Goose pimp
Desquamation of face moving downwards (mild sunburn)

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14
Q

GAS

Rx

A

Exquisitely sensitive to penicillin

Resistent strains not documented

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15
Q

PANDAS

A

Unproven

GAS & Tics, OCD

No evidence for testing, anti-strep prophylaxis, immunomodulatory Rx

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16
Q

Chorea

Frequency
Features
Exacerbating & relieving factors

Specific signs

A

In 10-15%
Usually isolated & subtle
Emotional lability, in coordination, poor school performance, uncontrollable movements, facial grimacing

Exacerbated by stress; resolves in sleep
Unilateral

Milk maids grip
Spooning & pronation of extended arms
Wormian darting movement of protruded tongue

17
Q

Ddx arthritis ARF

A

Septic

JIA
Reactive (Shigella, salmonella, yersinia)
Serum sickness 
SCD
Malignancy 
SLE
Post-strep reactive arthritis
18
Q

Ddx chorea

A 
Huntington
Wilson 
SLE
CP
Tic
Hyperactivity
19
Q

Neonatal GBS

Intrapartum chemoprophylaxis effect

Rx Neonatal GBS disease

A

Decreased incidence of early onset sepsis

No effect on late onset disease

Penicillin G

20
Q

Late onset disease neonatal GBS

Age
Increased risk after obstetric complications 
Clinical manifestations 
Common serotype
Case fatality
A

7 - 90 days
No effect from obstetric complications
Serotype 3

Bacteraemia, meningitis, OME, septic arthritis

2.8% case fatality

21
Q

When is risk of TB disease highest

Proportion who get disease <1 y

1-2y

When are the ‘safe’ years

A

First 2 years post infection

<1y 50% get disease, 10-20% meningitis, dissemination

1-2y 15-29% get disease

5-10y ‘safe school years’

> 10, 19-20% get disease

22
Q

TB

Proportion children symptomatic with disease

Typical presentation

Infants more or less likely to be symptomatic?

A

50% children

Cough, fever, malaise, weight loss, decreased appetite, night sweats

Infants 80% symptomatic

23
Q

TB testing

Which cells release interferon gamma

Sensitivity of TST and IGRA

A

Antigen specific T cells

Both poorly sensitive

IGRA highly specific

24
Q

TB meningitis

Symptoms

Typically diagnosed how long after infection

Spread from where via where

Most common in which age group

A

6-12 mo after initial infection

Headache behaviour change
Convulsions cranial nerve palsies
Hemiplegia
Coma

Lung
Lymphohaematogenous
Miliary
CNS

25
Q

Isoniazid-

Rifampicin-

Pyrazinamide-

Ethambutol-

Which bacteria killed by which drug

A

Rapid and intermediate growing

Rifampicin all including dormant

Pyrazinamide slowly growing

Ethambutol- all, minimises drug resistance

26
Q

MAC associated infection

A

Lymphadenitis

Lung

Skeletal

Disseminated

27
Q

Persistent generalised lymphadenopathy

Infectious ddx

Non infectious ddx

A

Infectious
TB, EBV, bartonella henselae, CMV, Toxoplasmosis, syphilis, hepatitis, kawasaki, brucellosis, HIV

Noninfectious
Leukaemia, lymphoma, neuroblastoma, histiocytosis, metastatic tumours, sarcoidosis, branchial cleft cyst, dermoid, thyroglossal duct

28
Q

Bartonella

Systemic complications

Gram stain

Resolves

A

Gram neg, gradual painful, 4-6 weeks to resolve

PUO, endocarditis
Encephalitis, aseptic meningitis 
Pbeumonitis, hepatitis, osteolytic
Loss if vision
Rash
Parinaud oculoglandular syndrome
29
Q

Enlarged pectoral lymph nodes typical of what disease

A

B. Henselae

30
Q

Intensely erythematous non-tender submandibular or cervical LN typical of what

A

MACE

31
Q

Dx of NTBM adenopathy

Rx

A

Clinical- adenopathy with minimal warmth and tenderness

Induration response to mantoux

Negative CXR

Rx excision
If not possible: clarithromycin, rifampicin, ethambutol

32
Q

EBV

Most likely symptomatic in whom

Heterophil Ab in what % by end of first week

Acute infection best characterised by presence of which IgM ab

A

Adolescents and young adults

Fever pharyngitis lymphadenitis splenomegaly (50%)

75%

anti-viral capsid antigen IgM

33
Q

Mononuclear cells

A

Lymphocytes and monocytes

34
Q

Lateral neck XR in retro pharyngeal abscess

A

2x the diametre of C2

Infectious Disease (14 decks)

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