Lactobacillus Species: Taxonomic Complexity and Controversial Susceptibilities

Abstract

The genus Lactobacillus is a taxonomically complex and is composed of over 170 species that cannot be easily differentiated phenotypically and often require molecular identification. Although they are part of the normal human gastrointestinal and vaginal flora, they can also be occasional human pathogens. They are extensively used in a variety of commercial products including probiotics. Their antimicrobial susceptibilities are poorly defined in part because of their taxonomic complexity and are compounded by the different methods recommended by Clinical Laboratory Standards Institute and International Dairy Foundation. Their use as probiotics for prevention of Clostridium difficile infection is prevalent among consumers worldwide but raises the question of will the use of any concurrent antibiotic effect their ability to survive. Lactobacillus species are generally acid resistant and are able to survive ingestion. They are generally resistant to metronidazole, aminoglycosides and ciprofloxacin with L. acidophilus being susceptible to penicillin and vancomycin, whereas L. rhamnosus and L. casei are resistant to metronidazole and vancomycin.

Probiotic potential comparison of Lactobacillus strains isolated from Iranian traditional food products and human feces with standard probiotic strains

“…Although Lactobacilli have a long history of safe use as microbial adjunct nutrition, their safety evaluation should not be neglected, as resistant strains may become the source for the spread of antibiotic resistance genes. Resistance to streptomycin and vancomycin was expected and also reported by several studies including Goldstein et al ., and Solieri et al . Fortunately, none of the strains in our study was resistant to chloramphenicol and tetracycline while their corresponding transferable resistant genes among lactobacilli are emerging …”

In vitro Assessment of Antibiotic Resistance Pattern among Lactobacillus Strains Isolated from Goat Milk

“…Our results are in concurrence with other reports, where lactobacilli displayed susceptibility to nitrofurantoin (Bouridane et al, 2016). Similar to this study, Goldstein et al, (2015) also reported sensitivity of lactobacilli towards tigecycline and chloramphenicol. In contrary to our results, Bhuiyan et al, (2017) documented resistance pattern of goat milk lactobacilli towards tetracycline.…”

Impact of probiotics on necrotizing enterocolitis

“…92 Most lactobacilli are sensitive to erythromycin, penicillins, clindamycin and vancomycin and resistant to metronidazole and aminoglycosides, with the most notable exception that many L. rhamnosus strains are resistant to vancomycin. 93,94 …”