Turicella on blood agar showing donut colony and Its Details

Turicella on Blood Agar Showing Donut Colony and Its Details

Turicella on Blood Agar Showing Donut Colony

Turicella otitidis on blood agar showing donut colony as shown above image and its was described originally in 1994 by Funke et al. It is a coryneform Gram-positive bacterium first isolated from patients with otitis media.

Scientific Classification

Domain: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Subclass: Actinobacteridae
Order: Actinomycetales
Suborder: Corynebacterineae
Family: Corynebacteriaceae
Genus: Turicella
Species: Turicella otitidis

Introduction

Turicella otitidis is long, unbranching Gram-positive bacilli that form 2-mm, non-hemolytic colonies after incubation for 24 hours on blood agar, with a creamy appearance, which may resemble small colonies of CoNS ( coagulase-negative staphylococci). The addition of Tween-80 to the medium does not stimulate the growth of the organism, thereby demonstrating its non-lipophilic nature.

Biochemical Reactions

It has the following features-

Catalase test: Negative
Non-motile
alkaline phosphatase test: Negative
Pirazinamidase test: positive
nitrate Reduction: Negative
urease test: Negative
It shows an oxidative metabolism for carbohydrates.

The numerical profile in the API (Analytical Profile Index) Coryne system is almost invariably 210004, a code shared with Corynebacterium auris and C. afermentans. Although final identification requires complex tests not employed habitually in the clinical laboratory, a distinction between T. otitidis and the above microorganisms may be made on the basis of relatively simple morphological and metabolical characteristics such as Gram’s stain Colony appearance, cAMP test, leucine arilamidase, Sensitivity to Penicillin and Erythromycin.

Pathogenicity

Otitis media is due to T. otitidis still debatable although the literature contains a number of reports of middle ear pathology and concomitant isolation of this organism. Most cases involve children aged below 3 years, and the organism is isolated in both pure or mixed cultures. Other reports of infections have involved several conditions like a cervical abscess, a mastoiditis, an auricular abscess with repeated episodes of otitis media, and a case of bacteremia in a patient with malign haemopathy.

Treatment

According to reports, most of these are cases of spontaneous drainage following a recurrence of otitis media after antimicrobial therapy that is ineffective against T. otitidis. The MICs of penicillin, levofloxacin, linezolid, and vancomycin were very low for all the isolates studied, but most isolates displayed high resistance to macrolides and lincosamides.

Keynotes

Similar organisms to Turicella otitidis are Corynebacterium afermentans subsp. afermentans and Corynebacterium auris.
T. otitidis can be differentiated from Corynebacterium afermentans subsp. afermentans and Corynebacterium auris on the following features-Gram’s stain, colony appearance, cAMP test, leucine arilamidase, sensitivity to penicillin, and erythromycin.
T. otitidis is long unbranching Gram-positive bacilli, arranged irregularly.
Antimicrobial sensitivity testing (AST) is determined with E-tests (AB Biodisk, Solna, Sweden) with an inoculum of 0.5 McFarland standard on plates of Mueller-Hinton agar (MHA) supplemented with sheep blood 5% v/v.
Identification of the organisms obtained is done with the API Coryne, API Zym, and API 50 CH systems (bioMérieux, Marcy l’Etoile, France), together with standard morphological and phenotypic tests.
This type of organism isolation in the laboratory by conventional method is cumbersome and hence use of API, MALDI-TOF mass spectrometry and PCR makes it easier to identify.

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