Table 8.

Laboratory Diagnosis of Focal Parenchymal Brain Infections

Etiologic Agents	Diagnostic Procedures	Optimum Specimens	Transport Issues and Optimal Transport Time
Bacterial
Aerobes: Streptococcus,  Staphylococcus, Enterobacteriaceae, Pseudomonas, Haemophilus, Listeria spp  Anaerobes: Bacteroides, Fusobacterium, Prevotella, Actinomyces, Clostridium, Propionibacterium spp	Gram stain Aerobic and anaerobic bacterial culture	Aspirate of abscess contents, tissue	Sterile anaerobic container, RT, immediately
Nocardia spp	Gram stain, modified acid-fast stain Aerobic bacterial culture (hold 7 d; add buffered charcoal yeast extract agar)	Aspirate of abscess contents, tissue	Sterile container, RT, immediately
	Histology (GMS, Gram stain)	Tissue	Closed container, RT, 2 h
Mycobacterium tuberculosis	AFB smear AFB culture	Aspirate of abscess contents (no swabs), tissue	Sterile container, RT, 2 h
	Histology (AFB stain)	Tissue	Closed container, RT, 2 h
	M. tuberculosis NAATa	Aspirate, tissue	Sterile container, RT, 2 h
Fungal
Candida spp  Cryptococcus spp  Aspergillus spp  Zygomycetes (Rhizopus, Mucor spp)  Scedosporium apiospermum  Trichosporon spp  Trichoderma spp  Dematiaceous molds   (Cladophialophora bantiana, Bipolaris spp, Exophiala spp  Endemic dimorphic fungi	Calcofluor stain Fungal culture	Aspirate of abscess contents, tissue	Sterile container, RT, 2 h
	Histology (GMS stain) Mucicarmine stain for Cryptococcus	Tissue	Closed container, RT, 2 h
Parasitic
Toxoplasma gondii	Toxoplasma NAAT	Aspirate of abscess contents, tissue	Sterile container, RT, 2 h
	Toxoplasma antibodies, IgM and IgGb	Serum	Clot tube, RT, 2 h
	Giemsa stain Histology	Aspirate of abscess contents, tissue	Closed container, RT, 2 h Formalin, indefinite
Taenia solium (neurocysticercosis)	T. solium antibodies, IgG, ELISA, confirmatory Western blotc	Serum	Clot tube, RT, 2 h
	Histologyd	Brain tissue	Closed container, RT, 2 h Formalin, indefinite
Acanthamoeba spp	Microscopic wet mount Giemsa stain	Aspirate of abscess contents, tissue	Closed container, RT, 2 h
	Histology (trichrome stain)	Aspirate of abscess contents, tissue	Closed container, RT, 2 h
	Culture	Aspirate of abscess contents, tissue	Sterile container, RT, 2 h
	Acanthamoeba antibody, IFAe	Serum	Clot tube, RT, 2 h
	Acanthamoeba IIF staininge	Brain tissue	Closed container, RT, 2 h
	Giemsa	Aspirate of abscess contents, tissue	Closed container, RT, 2 h
Balamuthia mandrillaris	Histology (trichrome stain)	Brain tissue	Closed container, RT, 2 h Formalin, indefinite
	Balamuthia antibody, IFAe	Serum	Clot tube, RT, 2 h
	Balamuthia IIF staininge	Brain tissue	Closed container, RT, 2 h

Abbreviations: AFB, acid-fast bacilli; ELISA, enzyme-linked immunosorbent assay; GMS, Gomori methenamine silver; IFA, indirect fluorescent antibody; IgG, immunoglobulin G; IgM, immunoglobulin M; IIF, indirect immunofluorescent antibody; NAAT, nucleic acid amplification test; RT, room temperature.

^aA negative result does not rule out Mycobacterium tuberculosis.

^bRefer positive IgM to Toxoplasma Serology Laboratory in Palo Alto, California, for confirmatory testing (http://www.pamf.org/serology/). The absence of IgM or IgG does not exclude Toxoplasma infection [33].

^cOnly 50% sensitivity if patient has solitary parenchymal lesion [34]; potential for false-positive ELISA results due to cross-reactivity with Echinococcus.

^dDiagnosis usually on basis of clinical presentation, neuroimaging, and serology. Only occasionally are invasive procedures (brain biopsy) required.

^eAvailable at the California State Department of Health Services and the Centers for Disease Control and Prevention [31].