Propionibacterium Infections Workup

Updated: Oct 07, 2015
  • Author: Sajeev Handa, MBBCh, BAO, LRCSI, LRCPI; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
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Workup

Laboratory Studies

A hormonal workup may be appropriate in adult female acne patients with signs of androgen excess, such as virilization. Hormonal workup may also be appropriate in preadolescent patients presenting with acne to evaluate for precocious puberty.

In some high-risk patients, Propionibacterium species are capable of causing significant infections, and efforts should be made to obtain specimens free of contamination by the normal flora of the mucous membranes and skin, where they reside. In addition, strict anaerobic technique should be followed to ensure isolation in suspected cases of Propionibacterium infection. The generation time of P acnes is 5.1 hours compared with the approximate 24-minute generation time of Staphylococcus aureus. [17]

In prosthetic joint infections, prolonged incubation beyond 13 days of aspirates and or of blood cultures is recommended to optimize the recovery of P acnes. [17]

CNS shunt infections require evaluation of cerebrospinal fluid (CSF) and blood cultures, particularly in cases of suspected ventriculoatrial shunt infections, in which case the yield may be higher. In the review performed by Conen et al, infection was defined by the first positive culture of CSF, wound swab, or shunt tip specimen; the initiation of an appropriate antimicrobial treatment for shunt-associated infection; or surgery at the site of the shunt (whichever occurred first). [9]

In cases of P acnes infectious keratitis, cultures were positive for P acnes using thioglycolate broth. None became positive before 7 days of growth, and the recommendation is to monitor the culture for at least 10 days to ensure isolation of this fastidious organism. [18]

In chronic pseudophakic-related endophthalmitis, culture of a vitreous biopsy sample may be positive for P acnes. If the artificial lens is removed, Gram stain and electron microscopy of the capsule may demonstrate gram-positive rods.

In transfusion-transmitted bacterial infection, blood should be collected from the opposite arm; aside from appropriate hematologic tests, this blood should be sent for culture. Following reporting, the blood-product bag should be sent to the microbiology laboratory for Gram stain and culture.

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Imaging Studies

In cardiovascular device–related infections, P acnes can be difficult to recover in cultures of clinical specimens unless anaerobic cultures are obtained and held for extended periods. CT scanning, ultrasonography, and MRI are useful in demonstrating fluid collection around a device, which can suggest infection. Percutaneous aspirate of the fluid with ultrasound or CT guidance may confirm device infection. Transesophageal echocardiography is required to visualize a vegetation in prosthetic valve endocarditis. [19]

In CNS shunt infections, neuroimaging studies may be used to look for evidence of ventriculitis or CSF obstruction. CT scanning or ultrasonography may be helpful in evaluating loculations at the distal end of a ventriculoperitoneal shunt.

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