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Table 2 Diagnostic tests for important bacterial pathogens that may cause persistent digestive disorders

From: Persistent digestive disorders in the tropics: causative infectious pathogens and reference diagnostic tests

Infectious pathogen

Diagnostic method

 

Microscopy

Stool culture

Immunology

Molecular biology (PCR)

Reference(s)

Aeromonas spp.

-a

Culture on cefsulodin-irgasan-novobiocin (CIN) or selective Aeromonas agar

-

(Experimental, not validated)

[31]

Campylobacter jejuni, C. coli

Darkfield microscopy: motile, curved or S-shaped rods (suggestive of Campylobacter spp.)

Culture on selective medium b (42°C, microaerophilic conditions)

· Faecal antigen enzyme immunoassay: Campylobacter -specific antigen (SA)

hipO gene (C. jejuni), glyA gene (C. coli)

[32]

· Serology (important for diagnosis of postinfectious immunological diseases)

Clostridium difficile

-c

Culture on selective medium, e.g. cycloserin-cefoxitin-fructose agar (CCF) + toxigenic culture

· 2-step algorithm:

Toxin genes (increasingly being used in clinical routine)

[33–35]

1) Screening: EIA for glutamate dehydrogenase (GDH)

2) ELISA for detection of toxin A and B

· Cell cytotoxicity assay for detection of toxin A and B

Escherichia coli

Enteroaggregative

-a

HEp-2 cell adherence assay (following incubation in Luria broth)

· Serology: antibody response against Plasmid-encoded toxin (Pet)

AggR, CVD432, EAST1 (most common virulence factors, not always present)

[36]

E. coli (EAEC)

· ELISA: secretory immunoglobulin A response to EAEC

Enteropathogenic E. coli (EPEC)

-a

Culture on MacConkey (MAC) agar

-

eae gene

[37]

Enteroinvasive E. coli (EIEC)

-a

Culture on MAC agar

ELISA: detection of the ipaC gene

ipaH , ipaB genes

[38]

Enterohaemorrhagic

-a

Culture on sorbitol-MAC agar (most O157:H7 strains form sorbitol-negative colonies)

· O157 latex agglutination test

STEC: stx1 , stx2 genes

[39, 40]

E. coli (EHEC including STEC)

· Shiga toxins 1 & 2 (ELISA)

EHEC: stx1/stx2 + eae gene

Enterotoxigenic E. coli (ETEC)

-a

Culture on MAC agar

Several immunoassays for toxin detection

stla/stlb and lt genes

[41]

Diffusely adherent E. coli (DAEC)

-a

HEp-2 cell adherence assay (following incubation in Luria broth)

-

daaD gene

[42]

Mycobacterium tuberculosis and atypical mycobacteria

- Histopathological examination of intestinal biopsies

Culture of biopsy material

· Interferon-gamma-release assay (IGRA) on heparinised blood samples

Nucleic acid amplification tests (lacks sensitivity for diagnosis of extrapulmonary tuberculosis)

[43, 44]

- Acid-fast stain (e.g. Ziehl-Neelsen, Kinyoun, Auramin)

· Tuberculin skin test

Plesiomonas shigelloides

-a

Culture on CIN agar

-

-

 

Salmonella enterica (typhoidal and non- typhoidal serovars)

-a

· Culture d from blood and/or bone marrow (enteric fever)

· Serotyping of isolates (Vi antigen)

(Mainly for research purpose)

[45–47]

· Cultured from stool or duodenal aspirate (typhoidal and non-typhoidal salmonellosis)

· ELISA: detection of S. typhi antigens (blood)

· Widal agglutination test (commonly used in Africa)

Shigella dysenteriae, S. flexneri, S. boydii, S. sonnei

-a

Culture on MAC, XLD, HE or Leifson agar

Agglutination tests to detect serogroup and serotype

ipaH, ipl genes

[48]

Tropheryma whipplei

Histopathological examination of PAS-stained intestinal biopsies: sickleform particle-containing cells

(Only in highly specialised laboratories)

Immunohistochemistry on PAS-positive biopsy material

whip1, whip2 genes

[49]

Vibrio spp.

Darkfield microscopy: comma-shaped, motile bacteria (highly suggestive of Vibrio spp.)

Culture on TCBS agar

-

PCR for species differentiation (V. cholerae, V. parahaemolyticus, V. vulnificus)

[50, 51]

Yersinia enterocolitica, Y. pseudotuberculosis

-a

Culture on CIN agar

Serology (important for diagnosis of postinfectious immunological diseases)

PCR (reference laboratories and research purposes)

[52]

  1. The laboratory techniques are divided into different categories and recommended tests for each pathogen are highlighted.
  2. a Gram staining of stool samples can be useful to evaluate the presence of leucocytes, but is not helpful to differentiate between pathogenic bacteria and apathogenic microbial flora.
  3. b Commonly employed selective media for detection of Campylobacter spp. include charcoal-cefoperazone-deoxycholate agar, Campylobacter blood agar plate, and cefoperazone-vancomycin-amphotericin agar [53].
  4. c Detection of C. difficile in the Gram stain is not adequate to differentiate between clinical infection and simple colonisation with C. difficile[54].
  5. d Commonly employed selective media for growth of S. enterica are MAC, XLD, HE, Leifson agar or other chromogenic media.
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BMC Infectious Diseases

ISSN: 1471-2334

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