From the Guidelines
Hafnia is the common genus of Hafneae, which is a group of gram-negative bacteria in the family Enterobacteriaceae. The most well-known species is Hafnia alvei, which is commonly found in the environment, particularly in soil, water, and the gastrointestinal tract of humans and animals 1. These bacteria are facultative anaerobes, meaning they can grow with or without oxygen. While Hafnia is generally considered an opportunistic pathogen, it can occasionally cause infections in humans, particularly in immunocompromised individuals. These infections may include gastroenteritis, urinary tract infections, and bacteremia. Some key characteristics of Hafnia bacteria include:
- Rod-shaped
- Ability to ferment various carbohydrates
- Typically motile due to the presence of flagella
- Can be identified in laboratory settings through biochemical tests Understanding this genus is important in clinical microbiology for proper identification and treatment of potential infections, as seen in the guidelines for the use of antimicrobial agents in neutropenic patients with cancer 1.
From the Research
Common Genus of Hafniae
- The genus Hafnia is a member of the family Enterobacteriaceae, consisting of gram-negative bacteria that are occasionally implicated in both intestinal and extraintestinal infections in humans 2.
- The genus currently contains only a single species, H. alvei, but more extensive phylogenetic depth is apparent based upon DNA relatedness and 16S rRNA gene sequencing studies 2.
- However, a study in 2019 found that the Hafnia genus can be divided into two distant species: alvei and paralvei, based on comparative genomic analysis 3.
- Another study in 2002 characterized 73 Hafnia alvei isolates and found that they could be divided into four distinct biotypes based on phenotypic and genotypic properties 4.
- The genus Hafnia is heterogeneous, and there is no clear evidence linking these organisms to gastro-enteritis 4.
Species of Hafnia
- H. alvei is the most well-known species of the genus Hafnia, and it has been implicated in various infections, including septicemia, pneumonia, and urinary tract infections 2, 5.
- H. paralvei is another species of the genus Hafnia, which was identified through comparative genomic analysis 3.
- The two species, alvei and paralvei, have distinct genomic profiles and may have different pathogenicity factors 3.
Pathogenicity of Hafnia
- Hafnia alvei has been shown to produce virulence factors, such as haemagglutinins, serum resistance, and siderophore synthesis, which may contribute to its pathogenicity 6.
- However, the low pathogenicity of H. alvei isolates may be due to their low frequency of expression of virulence factors compared to other clinically significant species 6.
- The genus Hafnia has undergone massive gene rearrangements, and the presence of numerous mobile genetic elements may contribute to its pathogenicity 3.