laboratory diagnosis of infections in immunocompromised ... · syndromic approach- fevers fuo...

Laboratory Diagnosis of Infections in Immunocompromised patients: A syndromic

approach

DrAr%KapilProfessor,DepartmentofMicrobiology

AIIMS,NewDelhi

Challenges in Specific Diagnosis

•  Typical presentation with localization is not present •  Multiple simultaneous infections can occur •  Non infectious etiology presenting like infections •  Wide differential diagnosis •  Causes range from all community acquired to opportunistic

•  Low threshold of diagnostic suspicion is needed •  Laboratory strategies broad based – prioritize based on common agent in

the clinical setting

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Clinical Information

Underlying factors •  Type of immunocompromised state •  Associated risk factors •  Duration of immunocompromised state Localization •  Respiratory involvement •  Neurological symptoms •  Skins and soft tissue infection •  diarrhoea


Focusofinfec+on %ofPa+entPulmonary 39.02Gastrointes+nal 18.29Infec+onsofunknownorigin 30.49Bone 1.22Centralnervoussystem 2.44Intravenoussite 1.22Skin 1.22Urinarytractinfec+ons 1.22

Respiratoryandgastrointes+nal 3.66Skin 1.22

Focus of infection documented in Febrile Neutropenia patients

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Syndromic approach

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Syndromic approach- FEVERS

FUO commonly Febrile neutropenia •  GNB,GPC and fungal infections

Sepsis •  Central line associated blood stream infections •  Mucositis and secondary bacteremias


Approach to lab diagnosis -specimen

Blood for culture •  Volume of blood remains the most important variable •  Media to cover Bacterial and fungal •  Collection under all ascetic techniques •  Central line and peripheral collections

•  Automated methods help in early detection •  Time to culture positivity for CLABSI or CRBSI •  Antimicrobial susceptibility testing


Pulmonary syndromes

Fever and new pulmonary infiltrates

•  Conventional respiratory pathogens •  nosocomial respiratory pathogens •  “Atypical” organisms- Mycobacteria, fungi, viruses, parasites

•  Radiological investigations are most important



Respiratory – BAL most appropriate •  Induced sputum or expectorated sputum next best choice

•  Direct microscopy , KOH, gram stain, calcofluor white, ZN staining, IFA

•  Culture for fungi and Mycobacteria •  Quantitative cultures for bacteria •  PCR based tests for viruses – CMV


KOH Preparation

Septatehyphae

Broadaseptatehyphae

Calcofluor stain

Broadnonseptatehyphae

Buddingyeastcells

Pseudohyphae

P.jeroveciiwithcalcofluorwhite

Fromaptwithdyspaneawheezinghemoptysis,nausea,vomi%ngDiarrhoea,gramnega%vesepsisEDGandBAL–Strongyloidesstercoralis

Considerscreeiningwithserologicaltestsforstrongyloidesin“atrisk“fromendemicarea


Stronglyloidosis


Characteris+csofthemainserologicaltestsforstrongyloidiasis

Requena-MéndezA,ChiodiniP,BisoffiZ,BuonfrateD,GotuzzoE,etal.(2013)TheLaboratoryDiagnosisandFollowUpofStrongyloidiasis:ASystema%cReview.PLoSNeglTropDis7(1):e2002.doi:10.1371/journal.pntd.0002002hdp://journals.plos.org/plosntds/ar%cle?id=info:doi/10.1371/journal.pntd.0002002

Gastrointestinal syndromes

Stomatitis •  Candida, HSV and chemotherapy induced

Diarrhoea •  Conventional infections ( dd GVHD) •  CDI colitis

Liver function derangements •  CMV and toxoplasmosis



Stool specimen •  Parasitic ova and cysts – esp coccidian parasites and microsporidia •  Cryptosporidium, Giardia •  Strongyloides

•  Bacterial cultures – Salmonella , Shigella , campylobacter

•  CDI toxin assay


Parasi%ccystsinstool20

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Skin and soft tissue infections

•  Infections in devitalized tissues •  Undrained fluid collections •  Cutaneous manifestations of fungal infections

Biopsy or tissue •  Histopathology and microscopy •  Culture – Bacterial, Mycobacterial, fungal


Prolongedgranulocytopenia-Fusarium


Acute Neurological syndromes

Meningoencephalitis •  conventional bacterial pathogens •  Tuberculosis, HSV •  Fungi – cryptococcus and candida Space occupying lesion type •  Toxoplasma, aspergillus and nocardia CSF •  Direct microscopy for bacteria and fungi •  Bacterial, fungal or viral culture •  Antigen detection - cryptococcal or bacterial or viral


Urinary tract Infections

•  Community acquired infections •  Catheter associated Urine •  Bacterial culture •  CMV inclusions - Microscopy •  Cryptococcal or legionella antigen •  Lipoarabinomannan assay for TB


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Biomarkers

•  Procalcitonin – Bacterial spesis •  Galactomannan – Invasive aspergillosis •  β D Glucan – Invasive fungal infections •  Lipoarabinomannan - tuberculsosis


Variables OR (at 95%CI) Sensit ivity%

Specif ic ity% PPV% NPV%

PCT ≥ 0.25 1.15 (0.33 - 4.03) 73.3 29.4 18.6 83.3

CRP ≥ 110 0.52 (0.10 - 2.61) 13.3 77.2 13.3 77.2

Procalcitonin (PCT) in febrile neutropenic episodes of children undergoing treatment for childhood cancers

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Diagnosis of Tuberculosis

TST •  >5mm in HIV or immunocompromised host

Interferon–Gamma Release Assays (IGRAs) •  QuantiFERON®-TB Gold-in-Tube test (QFT-GIT)- amount of IFN-γ released •  T-SPOT® TB test - number of cells that release IFN-γ

Unaffected by BCG and most environmental mycobacteria.

Limited data exist on use in immunocompromised persons and those who need serial testing.

•  All in addition to X ray, smear and culture and clinical findings



CMV Diagnosis

Summary of tests used for CMV diagnosis


Tests before Transplant - recipient

All patients •  CMV , HSV, VZV, EBV, HIV, HBV*, HCV (quantitative assays) •  VDRL , urine culture, •  Mantoux, chest X ray •  Toxoplasma * HBSAg, Anti HBS, Anti HBc ( core ag)

Pt in endemic areas/ exposure history •  Strongyloides, Leishmania, Coccidian parasites •  Histoplasma, Cryptococcus


Screening of donors

•  Any acute infection •  HIV •  Rabies •  Hepatitis viruses


Thank you.

All India Institute of Medical Sciences, New Delhi, India!

laboratory diagnosis of infections in immunocompromised ... · syndromic approach- fevers fuo...

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