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Corynebacterium amycolatum: An Unexpected Pathogen in the Ear.

ABSTRACT: Non-diphtheritic Corynebacteria are now being increasingly recognised as the causative agents of various infections. Among these organisms, Corynebacterium amycolatum is the most frequently isolated one. It has been isolated from urine, pus, catheter tips, blood, prostatic secretion, cerebrospinal fluid and sputum. However, to the best of our knowledge, there are no reports on its role in ear infections. Here, we present 12 cases of ear infection with C.amycolatum. A high index of suspicion is necessary for identification of these gram positive bacilli as they resemble other Corynebacterium species on gram stain. They have metachromatic granules which can be demonstrated by Albert's stain and form characteristic dry, flat colonies on blood agar. These organisms are frequently resistant to ceftriaxone and imipenem. In our study, among the 12 isolates, eight isolates were resistant to ceftriaxone and four to imipenem and two were intermediately susceptible to ceftriaxone although all the 12 strains were uniformly susceptible to vancomycin. All the isolates were negative for toxA and toxB genes by PCR. Genomic sequencing of two isolates confirmed them as C.amycolatum. C.amycolatum is a relatively rare cause of pyogenic ear infections. As it demonstrates more antibiotic resistance than other similar organisms, careful identification with antibiotic susceptibility testing is required in managing these infections.

SUBMITTER: Sengupta M

PROVIDER: S-EPMC4717710 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Corynebacterium pseudotuberculosis (CPS) is an important bacterial animal pathogen. CPS causes chronic, debilitating and currently incurable infectious diseases affecting a wide range of livestock and wild herbivores including camelids worldwide. Belonging to the Corynebacterium diphtheriae complex, this pathogen can also infect humans. The classical characterization of CPS is typically based on the testing of nitrate reductase activity, separating the two biovars Equi and Ovis. However, more refined resolutions are required to unravel routes of infection. This was realized in our study by generating and analyzing whole genome sequencing (WGS) data. Using newly created core genome multilocus sequence typing (cgMLST) profiles we were the first to discover isolates grouping in a cluster adjacent to clusters formed by CPS biovar Equi isolates. This novel cluster includes CPS isolates from alpacas, llamas, camels and dromedaries, which are characterized by a lack of nitrate reductase activity as encountered in biovar Ovis. This is of special interest for molecular epidemiology. Nevertheless, these isolates bear the genes of the nitrate locus, which are characteristic of biovar Equi isolates. However, sequence analysis of the genes narG and narH of the nitrate locus revealed indels leading to frameshifts and inactivity of the enzymes involved in nitrate reduction. Interestingly, one CPS isolate originating from another lama with an insertion in the MFS transporter (narT) is adjacent to a cluster formed by ovine CPS isolates biovar Equi. Based on this knowledge, the combination of biochemical and PCR based molecular biological nitrate reductase detection can be used for a fast and uncomplicated classification of isolates in routine diagnostics in order to check the origin of camelid CPS isolates. Further analysis revealed that partial sequencing of the ABC transporter substrate binding protein (CP258_RS07935) is a powerful tool to assign the biovars and the novel genomovar.

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Corynebacterium amycolatum: An Unexpected Pathogen in the Ear.

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