Carnobacterium inhibens isolated in blood culture of an immunocompromised, metastatic cancer patient: a case report and literature review.

BACKGROUND: Carnobacterium species are lactic acid-producing Gram-positive bacteria that have been approved by the US Food and Drug Administration and Health Canada for use as a food bio-preservative. The use of live bacteria as a food additive and its potential risk of infections in immunocompromised patients are not well understood. CASE PRESENTATION: An 81-year-old male with a history of metastatic prostate cancer on androgen deprivation therapy and chronic steroids presented to our hospital with a 2-week history of productive cough, dyspnea, altered mentation, and fever. Extensive computed tomography imaging revealed multifocal pneumonia without other foci of infection. He was diagnosed with pneumonia and empirically treated with ceftriaxone and vancomycin. Blood cultures from admission later returned positive for Carnobacterium inhibens. He achieved clinical recovery with step-down to oral amoxicillin/clavulanic acid for a total 7-day course of antibiotics. CONCLUSIONS: This is the fourth reported case of bacteremia with Carnobacterium spp. isolated from humans. This case highlights the need to better understand the pathogenicity and disease spectrum of bacteria used in the food industry for bio-preservation, especially in immunocompromised patients.

Genome-wide comparison of Carnobacterium maltaromaticum derived from diseased fish harbouring important virulence-related genes.

Although Carnobacterium maltaromaticum has been used as a probiotic in fish, it was reported to cause disease for the first time in Korea. The objective of this study was to understand the differences between pathogenic and non-pathogenic strains. Pathogenicity was tested by challenging rainbow trout with C. maltaromaticum ATCC35586 and 18ISCm isolated from diseased fish, and DSM20342 isolated from a dairy product. We also compared 24 genomes of C. maltaromaticum strains plus the genome of our isolate 18ISCm sequenced in this study. Only the strains from diseased fish caused high mortality with severe histopathological changes. Although all strains shared more than 90% of Ko_id, wecC and xtmA were found only in strains from diseased fish. Interestingly, only strains from diseased fish harboured two wecC paralogs involved in the production of D-mannosaminuronic acid which is a major component of a well-known virulence factor, teichuronic acid. Two wecC paralogs of 18ISCm were increased when they were co-cultured with trout blood cells, suggesting that wecC genes might play a role in virulence. The results of this study show that strains isolated from diseased fish are different from strains derived from food in terms of pathogenicity to fish and the presence of virulence-related genes.

Genomic and phenotypic analyses of Carnobacterium jeotgali strain MS3(T), a lactate-producing candidate biopreservative bacterium isolated from salt-fermented shrimp.

Carnobacterium jeotgali strain MS3(T) was isolated from traditionally fermented Korean shrimp produced with bay salt. The bacterium belongs to the family Carnobacteriaceae, produces lactic acid and contains gene clusters involved in the production of lactate, butyrate, aromatic compounds and exopolysaccharides. Carnobacterium jeotgali strain MS3(T) was characterized through extensive comparison of the virulence potential, genomic relatedness and sequence similarities of its genome with the genomes of other Carnobacteria and lactic acid bacteria. In addition, links between predicted functions of genes and phenotypic characteristics, such as antibiotic resistance and lactate and butyrate production, were extensively evaluated. Genomic and phenotypic analyses of strain MS3(T) revealed promising features, including minimal virulence genes and lactate production, which make this bacterium a desirable candidate for exploitation by the fermented food industry.

The genome sequence of the lactic acid bacterium, Carnobacterium maltaromaticum ATCC 35586 encodes potential virulence factors.

The genus Carnobacterium belongs to the lactic acid bacteria and Carnobacterium maltaromaticum is commonly found in modified atmosphere packed and vacuum packed fish and meat products as well as in live fish. This species has been described as a fish pathogenic organism but human clinical isolates have only been obtained at one occasion. To investigate the virulence potential we sequenced the entire genome of strain ATCC 35586, isolated from a diseased salmon. When comparing the translated gene products of ATCC 35586 to those of Gram positive bacterial pathogens and probiotics as well as the related Carnobacterium sp. AT7 we identified a range of putative virulence genes including genes encoding products involved in adhesion to fibronectin and collagen, capsule synthesis, cell wall modification, iron scavenging mechanisms, haemolysis, invasion and resistance to toxic compounds. Of particular interest was the presence of internalin encoding gene homologues to some of those found in Listeria spp. and Lactobacillus plantarum. Furthermore, the ATCC 35586 strain possesses a gene encoding a product similar to the central Listeria monocytogenes transcriptional regulator PrfA, that in this organism controls virulence gene expression by binding to conserved DNA binding sites. Based on the consensus DNA sequence of this binding site, we identified a total of 65 genes in the ATCC 35586 genome that in the upstream region carry a PrfA binding motif. Among these is one of the internalin encoding genes; two genes encoding products involved in capsule biosynthesis as well as various genes encoding products with metabolic functions. In contrast to L. monocytogenes, the ATCC 35586 strain did not encode other PrfA dependent virulence factors such as listeriolysin O, phospholipases A and B, ActA, listeriolysin O, zinc metallo protease and internalins A and B. In conclusion, C. maltaromaticum ATCC 35586 carries putative virulence genes that may explain its reported ability to infect fish. The findings of this study give no reason for concern regarding human health by the presence of this species in food products.