Characterization of a bacterial strain Lactobacillus paracasei LP10266 recovered from an endocarditis patient in Shandong, China

Abstract

Background Lactobacilli are often recognized as beneficial partners in human microbial environments. However, lactobacilli also cause diseases in human, e.g. infective endocarditis (IE), septicaemia, rheumatic vascular disease, and dental caries. Therefore, the identification of potential pathogenic traits associated with lactobacilli will facilitate the prevention and treatment of the diseases caused by lactobacilli. Herein, we investigated the genomic traits and pathogenic potential of a novel bacterial strain Lactobacillus paracasei LP10266 which has caused a case of IE. We isolated L. paracasei LP10266 from an IE patient’s blood to perform high-throughput sequencing and compared the genome of strain LP10266 with those of closely related lactobacilli to determine genes associated with its infectivity. We performed the antimicrobial susceptibility testing on strain LP10266. We assessed its virulence by mouse lethality and serum bactericidal assays as well as its serum complement- and platelet-activating ability. The biofilm formation and adherence of strain LP10266 were also studied. Results Phylogenetic analysis revealed that strain LP10266 was allied with L. casei and L. paracasei. Genomic studies revealed two spaCBA pilus clusters and one novel exopolysaccharides (EPS) cluster in strain LP10266, which was sensitive to ampicillin, penicillin, levofloxacin, and imipenem, but resistant to cefuroxime, cefazolin, cefotaxime, meropenem, and vancomycin. Strain LP10266 was nonfatal and sensitive to serum, capable of activating complement 3a and terminal complement complex C5b-9 (TCC). Strain LP10266 could not induce platelet aggregation but displayed a stronger biofilm formation ability and adherence to human vascular endothelial cells (HUVECs) compared to the standard control strain L. paracasei ATCC25302. Conclusion The genome of a novel bacterial strain L. paracasei LP10266 was sequenced. Our results based on various types of assays consistently revealed that L. paracasei LP10266 was a potential pathogen to patients with a history of cardiac disease and inguinal hernia repair. Strain LP10266 showed strong biofilm formation ability and adherence, enhancing the awareness of L. paracasei infections.

Lactobacilli Infection Case Reports in the Last Three Years and Safety Implications

“…The role of the biofilm formation capacity in virulence was confirmed by Tang et al [ 30 ]. They observed that L. paracasei LP10266, isolated from blood and marrow samples of a patient with endocarditis, did not induce platelet aggregation and induced complement activation.…”

“…To date lactobacilli involved in infections have been little characterized at genome level but from the studies reviewed here it emerged that the ability to behave as a pathogen is inherent to the strain or clone, besides depending on patient’s underlying conditions and risk factors. Studies on isolate characterization indicated the capacity to form biofilm as the most relevant virulence factor [ 30 , 62 ]. Strikingly, this trait varied between clones of the same probiotic L. rhamnosus GG, indicating that the genetic stability of probiotic strains must be checked to avoid use of variants with newly acquired hazardous traits.…”

“…Lactobacilli were isolated from blood [ 15 , 16 , 17 , 18 , 20 , 21 , 22 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 49 , 52 , 55 , 56 , 57 ], diseased valve tissue [ 23 ], abscess fluids [ 48 , 51 , 52 , 54 , 57 , 58 ], cerebrospinal fluid (CSF) [ 46 ], marrow [ 30 ], arthrocentesis aspiration fluid [ 53 ] in anaerobiosis and, in some cases, also in aerobiosis [ 15 , 34 ]. Use of automated microbial detection system, i.e., BACT/ALERT 3D or the BACTEC systems (BioMérieux) with incubation at 35 °C were mentioned in some reports [ 23 , 31 , 34 ].…”

“…Susceptibility to β-lactams, including amoxicillin, amoxicillin/clavulanic acid, ampicillin, ampicillin-sulbactam, benzylpenicillin, penicillin G, piperacillin/tazobactam, and meropenem IV was reported in most cases. These antibiotics were used singly or in association with gentamicin, clindamycin, and clarithromycin [ 16 , 17 , 20 , 21 , 22 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 35 , 36 , 37 , 38 , 39 , 40 , 43 , 44 , 45 , 46 , 48 , 49 , 51 , 53 , 54 , 55 , 56 , 57 , 58 ].…”

“…Most of the cases of endocarditis had a deceitful and slow onset, with or without fever, with symptoms varying among patients and including weight loss, fatigue, dyspnea, cough, chills, sweats, abdominal pain with nausea and vomiting, lumbar pain, syncope, with valvular vegetations becoming detectable after many days or even months from the beginning of symptoms [ 14 , 15 , 16 , 17 , 18 , 20 , 22 , 23 , 27 , 29 , 30 , 31 , 32 , 34 ]. In many cases replacement of the aortic valve [ 15 , 16 , 17 , 18 , 20 , 21 , 26 , 28 , 30 , 35 ], in one case replacement of the mitral valve [ 25 ], and in another case replacement of both aortic and mitral valves [ 23 ] were necessary.…”