Haematology - Neutropenic fever Flashcards

1
Q

Host immune defense in skin and mucosa?

A

Physicochemical barrier:
 Skin: pH, sIgA, normal flora, osmotic pressure

 Mucosa: pH, sIgA, normal flora, bile, digestiveenzymes, lysozyme, flushing/ peristalsis, lactoferrin, peroxidase

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2
Q

Immune defense against microbes in local tissues

A

Cellular arm of the innate immune response

 Infiltration by phagocytes (neutrophil, macrophages, Langhan cells)
 Exudation
 Local inflammatory response (LIRS)

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3
Q

Examples of 4 pathogens that are not virulent but cause disease in immunocompromised host

A
Opportunistic: 
Candida albicans
Bacillus cereus
Staphylococcus epidermidis
Cytomegalovirus (CMV)
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4
Q

Define immunocompromised host

Examples of immunocompromised state

A

Compromised host:

  • Has >1 significant alterations in body’s natural defense mechanisms (innate & adaptive immunity)
  • As a result of underlying diseases & their therapy
  • Which predispose the host to severe infections / neoplasia

E.g.:
o Leukaemia, lymphoma
o Organ/ bone marrow transplant, use of immunosuppressives (e.g. steroid, anti-TNF)
o Severe burn, massive trauma
o Alcoholism, under-nutrition & intravenous drug abuse

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5
Q

Examples of acquired immunocompromised state

A

Most common = HIV

From most to least severe:
 BMT
 Solid organ transplant (heart and lung > liver > kidneys)
 Cancers (hematological (leukemia, lymphoma) are more suppressed than the solid tumour)
 Autoimmune disorder
 Chronic diseases/ major organ failure (e.g. liver/ kidney failure)
 Splenectomy
 Malnutrition

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6
Q

Major mechanisms in compromising host immunity **

14

A
  1. Granulocytopenia (neutropenia = commonest, e.g. chemotherapy-induced)
  2. Cellular immune dysfunction (low CD4 T lymphocytes, e.g. AIDS, immunosuppressives)
  3. Humoral immune dysfunction (related to antibody, B lymphocytes)
  4. Anatomic-barrier damage involving the mucosa/ skin
    - Severe burn/ massive trauma
    - Chemotherapy-/ radiotherapy-induced mucositis Neutropenic fever most common
  5. Complement deficiency
  6. Autoantibody against cytokines (e.g. IFN-γ, IL-6, GM-CSF)
  7. Medical/surgical procedures, indwelling devices, implant devices
  8. Antimicrobial therapy: Suppress normal flora
  9. Gastric hypochlorhydria
  10. Therapeutic biologics
  11. Obstruction of conducting systems
    - draining from a normally sterile anatomical site to a non-sterile one
  12. Central nervous system dysfunction e.g. aspiration pneumonia
  13. Major organ dysfunction
  14. Others:
    o Thrombocytopenia
    o Malnutrition
    o Chronic blood transfusion/ poorly controlled diabetes mellitus
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7
Q

Pathogenesis of chemo-/ radiotherapy induced mucositis and subsequent infection

A

Cytoreductive chemotherapy acts on rapidly replicating cells
(e.g. blood cells, epithelial cells in GIT), e.g. chemotherapy mucositis affecting GI tract

> > Damage to mucosa throughout the alimentary system

> > endogenous bacterial/ fungal flora (or transient flora acquired from hospital environment) translocates across the mucosa

> > seeds the bloodstream and causes the majority of neutropenic fever cases

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8
Q

Clinical presentation of chemo/ radiotherapy induced mucositis

A
  1. Oral mucositis (sore throat; erythema, ulceration)
  2. Oesophagitis (retrosternal pain on swallowing)
  3. Enterocolitis (watery diarrhea)
  4. Narrowest part of GI tract which undergo frequent distension: cricopharyngeal junction, oesophagogastric junction, ileocecal junction, anus
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9
Q

Sources of bacteria causing chemo/radiotherapy-induced mucositis

A
o Feces (bacteremia)
o Skin (e.g. Hickman catheter exit site)
o Air (pulmonary aspergillosis)
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10
Q

Post-chemotherapy neutropenia

  • Explain why neutropenic fever must occur if neutropenia is not corrected after weeks
  • What determines the recovery of neutrophil count
A

Neutrophil half-life is only 8 hours
Neutrophil count is maintained by bone marrow reserves for up to 2 weeks
If WBC does not return to normal, then mucositis and infection will occur during neutropenic state

Determinants of neutrophil recovery:
- Intensity of chemotherapy
- Hematopoietic stem cell function and proliferation rate to re-populate BM
- Type of chemotherapy affects quality (function) of neutrophils: O2-dependent
microbicidal activity, complement receptor, adhesiveness, motility,
chemotaxis, loss of sialic acid…

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11
Q

Neutropenic fever

  • Define absolute neutrophil counts for severities of neutropenia
A

Absolute neutrophil count (ANC):
 ANC<1.5:
neutropenia (abnormal)

 ANC<0.5 (<500/μL):
severe neutropenia – rate of infections start to increase

 ANC<0.1 (<100/μL):
profound neutropenia – when most bacteraemia occurr

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12
Q

First-line investigations for neutropenic fever

A

Full Hx & P/E (daily): Focus on SKIN, GIT, RESPIRATORY tract
Skin, perianal skin (fungal cellulitis/ abscess: pain on defecation), surgical site infections S/S
 Oral, abdomen exam (ask for mucositis, esophagitis, enterocolitis, bowel habits)
 Lung, sinus (Respiratory S/S, Sinusitis S/S e.g. fungal sinusitis from inspiration)

Ix:
 General (CBP, LFT, RFT)
 Blood cultures from central venous catheter through 2 different ports

Abdomen:
 Abdomen CT scan
 stool culture: Add-on Clostridium difficile cytotoxin & culture

Lungs:
 CXR (low risk); CT thorax (high risk)
 BAL for sampling, culture

Others:
 Urine, skin, sputum culture

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13
Q

Neutropenic fever causes and predisposing conditions

A

conditions that decrease neutrophil production or increase neutrophil destruction:
- severe active infections such as sepsis, hepatitis, or tuberculosis
- bone marrow disorders like aplastic anemia or myelofibrosis;
- autoimmune diseases like systemic lupus erythematosus or rheumatoid arthritis.
- cancer treatments such as chemotherapy, radiation therapy, and hematopoietic stem cell transplant (HSCT)

Predisposing conditions:
o Chemotherapy induced mucositis
o Indwelling vascular catheter

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14
Q

Neutropenic fever presentation

A

Fever may be only symptom

Other S/S:
abdominal pain, mucositis of the gastrointestinal tract, and perirectal pain.
complications such as severe sepsis or septic shock

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15
Q

Treatment of neutropenic fever

A

Oral: Ciprofloxacin + Augmentin

IV:
- Piperacillin/Tazobactam
- Meropenem
+/- Glycopeptide, FLuoroquinolone

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16
Q

Explain how antimicrobial therapy can compromise host immunity and predispose nosocomial infection

A

Antimicrobial therapy:
o Suppress normal flora (anaerobes, relatively non-invasive)&raquo_space; flora fails to resist colonization by the more virulent and antibiotic-resistant hospital-acquired organisms (e.g. Pseudomonas aeruginosa, Corynebacterium jeikium, yeasts)

Hospital-acquired organisms: introduced into the patient during hospitalization by:
 Hands of medical personnel
 Various diagnostic/therapeutic procedures (e.g. endoscopy, surgery, nursing activities)

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17
Q

Explain how biologics can compromise host immunity and predispose opportunistic infections

A

Biologics: treat autoimmune diseases, e.g. inflammatory bowel disease, rheumatoid arthritis

MoA:
 Monoclonal antibodies against cytokine, chemokine (e.g. anti-TNF [infliximab], anti-IL-2, anti-IL-6 receptor, anti-IL-12/IL-23)
 Kinase inhibitors of the JAK-STAT signaling pathway (Ruxolitinib, Tofacitinib)

Result: interfere with the immune response (immunosuppression) – especially intracellular pathogens related to T cell immunity

18
Q

Types of ductal obstruction that lead to infection

A
o Urinary (ureter)
o Respiratory (e.g. bronchogenic carcinoma partially obstructing a bronchus > stasis of secretions > pneumonia)
o Biliary tree
19
Q

Types of organ failure that lead to infection

A

cirrhosis (liver failure), uraemia (renal failure), heart failure, chronic obstructive pulmonary disease, Splenectomy

20
Q

Conditions that lead to iron overload

Why does iron overload increase susceptibility to infection

A

Chronic blood transfusion/ poorly controlled diabetes mellitus

Siderophilic bacteria infection:
Klebsiella, Yersinia enterocolitica, Salmonella & Rhizopus infections

21
Q

5 unique features of infection in immunocompromised host vs normal host

A
  1. The spectrum of pathogens involved is highly predictable from the specific immune defect
  2. Unusual pathogens:
    o Ubiquitous organisms (environmental/ normal commensals)
    o Reactivation of latent organisms (e.g. Herpes viruses, Toxoplasma, Mycobacterium tuberculosis)
  3. Unusual/ non-specific clinical presentation:
    o Absence/ marked blunting of characteristic inflammatory symptoms & signs (subtle presentation)
    o Unusual sites are involved (e.g. perirectal cellulitis in neutropenic patients)
  4. Polymicrobial infections in severe immunity defects (e.g. bone marrow transplant patients)
  5. Oncogenic viruses may develop virus associated cancer
22
Q

3 virus associated cancers

A

o EBV-related post-transplant lymphoproliferative diseases;
o HHV8-related Kaposi’s sarcoma; or
o HPV-related ano-genital cancers

23
Q

7 principles in management of immunocompromised host infection

A
  1. Recognize specific immune defects
  2. High clinical suspicion of minimal symptoms (e.g. low grade fever, mental dullness)
  3. Always sample clinical specimen for microbiological tests
  4. Early, aggressive empirical antimicrobials before culture results
  5. Monitor drug therapy for efficacy and side effects
  6. Monitor paradoxical deterioration during recovery of immune defects
  7. Consult clinical microbiologist always
24
Q

Fever

  • Temperature definition
  • Pathophysiology
  • Importance of fever in immunocompromised host
A
Fever:
Definition:
 Oral temperature >37.6oC >once within a day; or
 (Single oral temperature >38.3oC; or
 (Sustained 38oC >1 hr)

Due to release of pro-inflammatory cytokines from endothelial cells/macrophages (IL1, TNF, IL4,6)

Often the only manifestation of infection in immunosuppressed host (e.g. may not have sore throat, diarrhea)

Blunted by steroid, chemotherapy, NSAID

25
Q

List types of sampling and biopsy for Ix of infection in immunocompromised host

A
clinical specimens for:
o Cultures (blood culture = minimal)
- Blood cultures from central venous catheter
- Urine, skin, sputum
- BAL
- Stool

o Direct microscopy/ visualization (e.g. gram staining, Z-N staining)

o Antigen detection (e.g. latex agglutination test for Clostridium difficile, Cryptococcus neoformans)

26
Q

Which conditions can present with paradoxical deterioration during recovery of immune defct

A

Paradoxical deterioration: e.g. fever, new inflammatory focus, progression of a
preexisting inflammatory focus

Immune Reconstitution Inflammatory Syndrome (IRIS): recovery of CD4
lymphocyte count after antiretroviral treatment)

Myeloid Reconstitution Syndrome: recovery of ANC after chemotherapy

27
Q

Prevention measures against infections in immunocompromised host

A
  1. Avoid unecessary invasive procedures and antimicrobial therapies
  2. Treat potential/ established infections before immunosuppressive therapy e.g. dental carries, anal fissures, chronic sinusitis and lung infections…
  3. Serological screening for latent infections before transplant (e.g. HSV, CMV, HIV, HBV, Toxoplasma)
  4. Total parenteral nutrition for chemotherapy-induced severe mucositis
28
Q

Neutropenic fever

Causative organisms

A

0-30 days after transplant – pathogens from mucosa with high microbial count (e.g. alimentary tract, skin, airway):

(Think about quantitative neutrophil defect. Always GPC, GNR, Fungal)

Pyogenic bacterial infection  bacteremia:
Gram-positive cocci:
 Staphylococcus epidermidis, S. aureus
 Viridans streptococci (esp. S. mitis) (dental plaque)
 Enterococcus spp.

Gram-negative bacilli:
 Gut flora (large intestine): Escherichia coli, Klebsiella pneumoniae
 Pseudomonas aeruginosa

Fungi:
o Yeasts: Candida spp., Trichosporon spp., Torulopsis spp.
o Moulds/ filamentous: Aspergillus, Fusarium spp, Zygomycetes, Mucoraceae

Virus:
o D0-14: HSV 1&2
o D20-27: HHV 6&7

29
Q

Special preventative measures against neutropenic fever

A
  1. Oral prophylactic antibiotics:
     E.g. fluoroquinolones, septrin for pneumocystis jerovecii
  2. Prophylactic antifungal: Azoles
     Fluconazole for Candida species
     Voriconazole/ posaconazole for yeasts and molds
  3. Granulocyte colony stimulating factor (G-CSF) to speed up the quantitative
    and functional recovery of these phagocytes

High risk (e.g. bone marrow transplant):
To prevent aspergillosis:
Protective isolation rooms (e.g. high efficiency particulate air (HEPA) filter
Low-microbe food
 Passive immunisation – intravenous immunoglobulin (IVIG)

30
Q

Cellular immune dysfunction
(CD4 helper T lymphocyte related) –quantitative and/or qualitative defect

Causes

A

Hodgkin’s disease

AIDS

childhood acute lymphoblasticleukaemia (ALL)

Solid organ transplant, engrafted bone marrow transplants recipients

Treatment with steroid, cyclosporin & other cytotoxic (e.g. chlorambucil for CLL)

Auto-antibody against INF-γ

31
Q

Cellular immune dysfunction
(CD4 helper T lymphocyte related)

Pathophysiology of Th cell dysfunction

A

Helper T lymphocytes fail to activate the macrophage/monocyte by IFN-γ to kill the ingested intracellular pathogens:

  • Herpes viruses
  • Toxoplasma gondii
  • Mycobacterium abscessus

Cannot activate CD8+ cytotoxic T lymphocytes/ natural killer cells to kill off virus-infected host cells

32
Q

Cellular immune dysfunction
(CD4 helper T lymphocyte related)

Types of pathogens causing infection

A

Viruses:
- CMV, HSV, VZV, HHV6,7, EBV, respiratory viurses, HPV

Intracellular bacteria: Mainly aerobic Gram-positive rods:

  • Listeria monocytogenes
  • Nocardia, Rhodococcus
  • Mycobacterium (both TB, MOTT)

Gram-negative rods:

  • Salmonella spp.,
  • Burkholderia pseudomallei,
  • Legionella

Fungi:
Yeast: Pneumocystis jirovecii (carinii; PCP), Cryptococcus neoformans (meningitis), Microsporidia
Mould: Aspergillus species
Dimorphic fungi: Penicillium marneffei, Histoplasma, Coccidioides

Parasites Protozoa: Toxoplasma gondii, Cryptosporidum, Cyclospora, Isospora

Helminth: Strongyloides, stercoralis

33
Q

Cellular immune dysfunction
(CD4 helper T lymphocyte related)

Preventative measures against infection

A

Prophylactic antiviral:
 Acyclovir for HSV
 Ganciclovir for CMV
 Entecavir for HBV

Prophylactic antifungal:
 Voriconazole/ posaconazole for yeasts and molds
 Septrin for PCP

Prophylactic antiparasitic:
 Septrin for Toxoplasma gondii

Some bone marrow transplant patients:
Passive immunisation – intravenous immunoglobulin (IVIG)
 Adoptive transfer of virus specific ex-vivo expanded T lymphocytes for preventing or treating PTLD/
resistant CMV/ adenovirus
infections

34
Q

Cellular immune dysfunction
(CD4 helper T lymphocyte related)

Preventative measures against infection

A

Prophylactic antiviral:
 Acyclovir for HSV
 Ganciclovir for CMV
 Entecavir for HBV

Prophylactic antifungal:
 Voriconazole/ posaconazole for yeasts and molds
 Septrin for PCP

Prophylactic antiparasitic:
 Septrin for Toxoplasma gondii

Some bone marrow transplant patients:
 Passive immunisation – intravenous immunoglobulin (IVIG)
 Adoptive transfer of virus specific ex-vivo expanded T lymphocytes for preventing or treating PTLD/
resistant CMV/ adenovirus
infections

35
Q

Humoral immune dysfunction

Causes
Pathophysiology of increased susceptibility to infections

A
 Chronic lymphocytic leukaemia
 Multiple myeloma
 Rituximab
 Agammaglobulinaemia
 Splenectomized patients (including functional asplenia)

 Decreased opsonising antibody
production; or
 Clearing of immune complexes (Note: B cells need activation by CD4 helper T
cells, hence mixed immunodysfunction are common)

36
Q

Humoral immune dysfunction

Pathogens causing infections

A
Increased risk of sepsis from:
 Encapsulated bacteria:
o Streptococcus pneumoniae
o Haemophilus influenzae type b
o Neisseria meningitidis
o Capnocytophaga canimorsus (e.g. children, licked by dogs)

 Other bacteria: Salmonella
 Protozoa: Babesia microti (children)
 Plasmodium

37
Q

Humoral immune dysfunction

Methods for prevention of infection

A

Chronic lymphocytic leukaemia: passive immunisation – intravenous immunoglobulin (IVIG)

38
Q

Post-splenectomy/ hyposplenism

Pathophysiology of increased susceptibility to infection

Types of pathogens causing infection

Prevention methods

A

(Spleen is critical in clearing/ filtering bacteraemic organisms which an individual has no prior contact and is non-immune)

 Cannot clear encapsulated bacteria
 Cannot produce opsonizing antibody (IgM), opsonins (tuftsin, properdin)

Increased risk of sepsis from:
 Encapsulated bacteria:
o Streptococcus pneumoniae
o Haemophilus influenzae type b
o Neisseria meningitidis
o Capnocytophaga canimorsus (e.g. children, licked by dogs)
 Other bacteria: Salmonella
 Protozoa: Babesia microti (children)
 Plasmodium

Prevention: With/before splenectomy:
active immunisation – pneumococcal vaccine
(especially children)

39
Q

Complement deficiency

Increased susceptibility to which infections

A

Encapsulated bacteria (S. pneumoniae, H. influenzae), esp. Neisseria meningitidis

40
Q

Name 3 indwelling devices that increase risk of opportunistic infections

A

a) Implanted vascular catheters (e.g. Hickman)
 Exit site infections (erythema, dirty granuloma)
 Tunnel infections
 Catheter-related bacteraemia/ fungaemia

b) Foley’s catheter - Urinary tract infection

c) Endotracheal tube
 Pneumonia
 Sinusitis

41
Q

Pathogens related to indwelling device infections

A
a) Implanted vascular catheters (e.g. Hickman)
 S. epidermidis
 S. aureus
 Bacillus spp.
 Candida spp.

b) Foley’s catheter UTI
 Aerobic Gram-negative bacilli: Enterobacteriaceae, Vibrionaceae and other genera, non-fermenters, etc.
 Enterococcus

c) Endotracheal tube
 Aerobic Gram-negative bacilli: Enterobacteriaceae, Vibrionaceae and other
genera, non-fermenters, etc.