The Lactobacillus genus

Lactobacilli are Gram positive rods belonging to the Lactic Acid Bacteria (LAB) group. Their phenotypic traits, such as each species' obligate/
facultative, homo/heterofermentation abilities play a crucial role in souring raw milk and in the production of fermented dairy products such as
cheese, yoghurt and fermented milk (including probiotics). An up to date safety analysis of these lactobacilli is needed to ensure consumer safety.
Lactobacillus genus is a heterogeneous microbial group containing some 135 species and 27 subspecies, whose classification is constantly being
reshuffled. With the recent use of advanced molecular methods it has been suggested that the extreme diversity of the Lactobacillus genomes
would justify recognition of new subgeneric divisions. A combination of genotypic and phenotypic tests, for example DNA-based techniques and
conventional carbohydrate tests, is required to determine species. Pulsed-Field gel Electrophoresis (PFGE) has been successfully applied to strains
of dairy origin and is the most discriminatory and reproducible method for differentiating Lactobacillus strains. The bibliographical data support
the hypothesis that the ingestion of Lactobacillus is not at all hazardous since lactobacillemia induced by food, particularly fermented dairy
products, is extremely rare and only occurs in predisposed patients. Some metabolic features such as the possible production of biogenic amines in
fermented products could generate undesirable adverse effects. A minority of starter and adjunct cultures and probiotic Lactobacillus strains may
exceptionally show transferable antibiotic resistance. However, this may be underestimated as transferability studies are not systematic. We
consider that transferable antibiotic resistance is the only relevant cause for caution and justifies performing antibiotic-susceptibility assays as
these strains have the potential to serve as hosts of antibiotic-resistance genes, with the risk of transferring these genes to other bacteria. However,
as a general rule, lactobacilli have a high natural resistance to many antibiotics, especially vancomycin, that is not transferable. Safety assessment
requirements for Lactobacillus strains of technological interest should be limited to an antibiotic profile and a study to determine whether any
antibiotic resistance(s) of medical interest detected is (or are) transferable. This agrees with the recent EFSA proposal suggesting attribution of a
QPS status for 32 selected species of lactobacilli.


Lactobacilli colonize the gastrointestinal and urinary tracts of humans, making them an integral part of the microbial flora.
However, in certain circumstances, they can cause disease. Although lactobacilli are often misidentified as streptococci, it is
highly likely that these infections will be attributed to them due to current improvements in laboratory techniques. A recent resurgence
in interesting natural products has caused an increased focus on the use of probiotics. Many of these probiotic formulations
contain Lactobacillus species. Although there have been reports of lactobacilli providing benefit in infectious diarrhea, the use of
these probiotic products in immunosuppressed or critically ill patients is not advised, since these populations are at increased risk
of developing infections due to lactobacilli.
附件：Propionibacterium and Bifidobacterium.pdf
附件：The Lactobacillus genus.pdf
附件：Lactobacillus- a Review.pdf