Varibaculum cambriense was first characterized in 2003 based on isolates obtained from human vaginal and abscess samples. However, the precise prevalence and incidence of V. cambriense infections remain unclear, likely due to its rare occurrence and potential underdiagnosis.

Reports suggest that infections caused by V. cambriense have been documented in diverse anatomical sites, including the umbilical scar, groin, buttock, breast, neck, and peritoneum. Nevertheless, the number of confirmed cases is limited, primarily reported in Europe and Asia, contributing to the overall understanding of its epidemiology.  

Understanding potential risk factors associated with Varibaculum cambriense infection is crucial. Individuals with compromised immunity or those experiencing immunosuppression are at a higher risk. Risk factors like diabetes mellitus, trauma, prior surgery, or foreign body implantation may predispose individuals to V. cambriense infections. 

Classification and Structure: 

Kingdom: Bacteria 

Phylum: Actinomycetota 

Class: Actinomycetia 

Order: Actinomycetales 

Family: Actinomycetaceae 

Genus: Varibaculum 

Species: V. cambriense  

Varibaculum cambriense is a gram-positive anaerobic bacterium characterized by its rod-shaped morphology and the formation of irregular colonies when cultivated on agar plates.  

The fatty acid profile of this bacterium predominantly comprises 16:0, 18:1 9c, and 18:2 6,9c/18:0 ANTE as its major components.  

Regarding genetic composition, V. cambriense boasts a DNA G+C content of 64.3 mol%, reflecting its genomic stability.  

The bacterium’s genome measures approximately 3.08 Mb in size and contains 2,848 protein-coding genes, underlining the complexity and diversity of its genetic makeup.  

Varibaculum cambriense, with the type strain CCUG 44998 isolated from a human postauricular abscess in Wales, UK, in 2003, is a critical reference point for understanding its characteristics. Notably, strains such as CIP 107344, DSM 15806, and R12359 share an incredibly high 16S rRNA gene sequence similarity of 99.9% with the type strain. This underlines the genetic consistency among various isolates of V. cambriense from clinical human sources, emphasizing the uniformity in their genetic makeup.  

Moreover, Varibaculum cambriense has been found to possess virulence factors contributing to its pathogenicity. The production of hemolysin, capable of lysing red blood cells and causing tissue damage, represents a significant virulence trait. Additionally, the production of lipase, which can hydrolyze lipids, potentially inducing inflammation, further underscores its pathogenic potential.  

The pathogenesis of Varibaculum cambriense in humans still needs to be adequately elucidated, primarily attributed to its capacity to produce a range of enzymes, including lipase, esterase, and beta-galactosidase.

These enzymes potentially play a role in tissue degradation within the host and evasive maneuvers against the immune system. Moreover, V. cambriense can form biofilms, further complicating its pathogenic mechanisms.   

In human hosts, Varibaculum cambriense is believed to contribute to developing skin and soft tissue infections, particularly abscesses. Abscesses represent localized accumulations of pus enveloped by inflamed tissue. This suggests a potential pathogenicity of V. cambriense in initiating and exacerbating these confined, inflammatory lesions within the affected tissues. 

Varibaculum cambriense may trigger the innate immune system through pattern recognition receptors (PRRs) like toll-like receptors (TLRs), instigating inflammatory and antimicrobial responses. However, the specific PRRs and ligands responsible for recognizing V. cambriense remain unidentified.

The bacterium is known to produce virulence factors such as hemolysin and lipase, potentially causing harm to host cells and tissues. Furthermore, plasmids harboring antibiotic-resistance genes or other virulence elements may bolster the pathogenicity and survival of V. cambriense within the host. 

Infections involving V. cambriense often manifest as polymicrobial, engaging co-infecting bacteria like Peptostreptococcus spp., Bacteroides spp., Escherichia coli, or Staphylococcus aureus, which can modulate the host immune response either synergistically or antagonistically.

These infections are typically associated with predisposing factors such as previous surgery, trauma, foreign body presence, diabetes mellitus, or immunosuppression, potentially compromising the host’s immune response and rendering it more susceptible to severe infections.

Despite these insights, the specifics of the adaptive immune response to Varibaculum cambriense, including its antigenicity, immunogenicity, and potential for eliciting specific antibody or T-cell responses in the host, remain elusive. 

Varibaculum cambriense is a versatile bacterium known to be isolated from various clinical conditions, including breast abscess, brain abscess, cheek abscess, submandibular abscess, and ischiorectal abscess.   

The primary clinical manifestations associated with V. cambriense infections primarily involve skin and soft tissue complications, such as abscess formation, cysts, and wound infections.

Nevertheless, this bacterium is not confined to these regions alone; it can also be responsible for infections in other body parts, such as the ovaries, brain, cheeks, submandibular region, and ischiorectal fossa. 

Culture test: In diagnosing Varibaculum cambriense, a selective culture medium is utilized to foster its growth while inhibiting other bacterial species. A commonly employed medium is Columbia blood agar supplemented with antibiotics like vancomycin, nalidixic acid, and colistin. After incubation, V. cambriense typically presents as small, pinpoint, round, gray-white colonies on the agar. Microscopic observation reveals gram-positive cocci arranged in clusters or chains. Further identification involves biochemical tests to confirm the presence of critical enzymes such as lipase, esterase, and beta-galactosidase, aligning with the bacterial profile associated with Varibaculum cambriense.   

Gram Staining: Gram staining is an initial and expedient diagnostic test offering insights into the morphology and gram reaction of Varibaculum cambriense. This bacterium exhibits a Gram-positive and curved bacillus structure, often resembling Actinomyces spp. or Corynebacterium spp. This rapid assessment provides valuable preliminary information about the bacterial sample.   

Biochemical Testing: Positive results for specific enzymes like leucine arylamidase, hippurate hydrolysis, alpha-glucosidase, and specific acid productions from glucose and sucrose aid in identifying Varibaculum cambriense, while negative results for other indicators further refine the diagnosis.   

Commercial Systems: Certain commercial systems, including the analytical profile index (API) Rapid ID 32 Strep and Coryne kits by bioMerieux, are valuable tools for V. cambriense identification. These systems provide biochemical profiles crucial for accurate diagnosis. However, it’s important to note that these commercial databases might not always include Varibaculum cambriense, potentially leading to misidentifications, such as categorizing it as Corynebacterium spp., Actinomyces spp., or Arcanobacterium spp. Despite this limitation, these commercial systems enhance diagnostic efficiency and accuracy when available.   

Molecular Testing: Molecular testing proves to be the most accurate and reliable method for Varibaculum cambriense identification. This method involves identifying the bacterium’s unique genetic material, particularly its 16S rRNA gene sequence. Utilizing polymerase chain reaction (PCR), the 16S rRNA gene sequence is amplified and can be sequenced or compared with databases, effectively differentiating V. cambriense from other related bacteria. 

• Ensure good personal hygiene practices and avoid contact with contaminated objects or surfaces, such as intrauterine devices, surgical instruments, or wounds, to reduce the risk of Varibaculum cambriense infection. 

• Refrain from sharing personal items like razors, towels, or clothing with individuals with Varibaculum cambriense infection, reducing the likelihood of transmission through contaminated items. 

• Seek immediate medical assistance upon experiencing skin and soft tissue infection symptoms, such as pain, swelling, redness, or pus formation, to facilitate timely diagnosis and appropriate treatment for Varibaculum cambriense. 

Varibaculum massiliense sp. nov., a new bacterium isolated from human urine with culturomics – PubMed (nih.gov)  

Varibaculum cambriense infections: Topics by Science.gov