Corynebacterium urealyticum: Detection and Clinical Significance

Corynebacterium urealyticum is a Gram-positive pleomorphic rod belonging to the genus Corynebacterium. It is non-spore-forming and non-motile. One of its most important biological features is strong urease positivity, which distinguishes it from many other coryneform bacteria and plays a central role in its pathogenicity.

In addition to urease activity, the organism is catalase positive and capable of fermenting glucose. Its ability to produce large amounts of ammonia through urea hydrolysis promotes alkaline conditions in the urinary tract, favoring crystal deposition, tissue irritation, and persistent infection.

A notable clinical concern is its broad intrinsic resistance to multiple commonly used antibiotics, including many beta-lactams such as penicillins and cephalosporins, as well as macrolides such as erythromycin.

Corynebacterium urealyticum is part of the normal flora of human skin and the periurethral region, but it is also commonly encountered in hospital environments. Under appropriate conditions, it can transition from colonizer to pathogen.

Transmission is often associated with healthcare settings, especially among patients exposed to invasive urinary procedures or prolonged hospitalization. Long-term catheterization, broad-spectrum antibiotic exposure, and impaired host defenses can facilitate colonization and subsequent infection.

Its tendency to persist on medical devices and surfaces is further enhanced by its biofilm-forming capacity, making it a clinically relevant cause of device-associated and nosocomial infections.

Corynebacterium urealyticum is most strongly associated with urinary tract disease. A characteristic condition linked to this organism is alkaline encrusted cystitis, often accompanied by urinary pH greater than 7 and a strong ammonia odor. It may also cause pyelonephritis, urinary calculi, and persistent urinary tract infections.

Outside the urinary tract, the bacterium can cause wound infections, particularly after surgery or in patients with implanted medical devices. Its clinical impact is especially significant in high-risk groups such as patients with long-term urinary catheters, diabetes mellitus, organ transplantation, or prolonged prior exposure to broad-spectrum antibiotics.

Because the organism is sometimes dismissed as a contaminant, diagnosis may be delayed, allowing infection to progress and become more difficult to eradicate.

Laboratory diagnosis of Corynebacterium urealyticum begins with direct microscopy and culture. Gram staining may reveal pleomorphic Gram-positive rods. Culture is typically performed on blood agar or chocolate agar under aerobic conditions at 35–37°C, but the organism may require 48–72 hours for visible growth.

Colonies are usually small, approximately 0.5–1 mm in diameter, gray-white, opaque, dry, and rough, without hemolysis. Due to strong urease activity, surrounding medium may turn pink, providing an important phenotypic clue.

Definitive identification can be achieved by MALDI-TOF MS or 16S rRNA gene sequencing. In addition, PCR and real-time qPCR assays offer sensitive and specific molecular detection of Corynebacterium urealyticum, supporting rapid identification in clinical specimens and improving recognition of infections that might otherwise be overlooked.

Treatment of Corynebacterium urealyticum infection is complicated by its multidrug resistance profile. The organism is generally susceptible to vancomycin, linezolid, and tigecycline. Intravenous vancomycin or teicoplanin is commonly considered first-line therapy, while rifampin may be added in more complicated or persistent cases.

Because this pathogen can form biofilms and cause chronic device-associated infection, management should be guided by antimicrobial susceptibility testing whenever possible. Removal or replacement of contaminated devices may also be necessary to achieve full clinical resolution.

In laboratory and environmental settings, inactivation can be achieved using chlorine-based disinfectants at 1000 mg/L available chlorine for 10 minutes, 70% ethanol, or 2% glutaraldehyde. Physical inactivation methods include autoclaving at 121°C for 15 minutes or dry heat sterilization at 160°C for 1 hour.