Long-term in vitro cultivation of Borrelia burgdorferi sensu lato strains: influence on plasmid patterns, genome stability and expression of proteins

Low (7th) and high (298th/304th) in vitro passages (cultivated over a period of 3 years) of two human Borrelia burgdorferi sensu lato strains, PKo (B. afzelii) and PBi (B. garinii) were compared by pulse-field gel electrophoresis, Southern blot, sequencing of the ospA gene, SDS-PAGE and Western blot. Digestion of genomic DNA with ApaI, BssHII, KspI, MluI, SmaI and XhoI did not reveal any differences between low and high passages. The loss of two linear plasmids with sizes of 6 and 31 kbp was detected in strain PKo between passages 34-50 and 101-304, respectively, whereas the ospA-carrying plasmid remained unchanged. In contrast, analysis of linear plasmid profiles obtained from low and high passages of B. garinii strain PBi showed no differences. Sequence analysis of the ospA gene demonstrated no difference in the strain PBi and one nucleotide exchange in the strain PKo when low and high passages were compared. The observed transition (G-A) in the third codon position did not alter the amino acid sequence. However, the rate of expression of the outer surface proteins OspA, OspB and OspC of strain PKo during low and high stages of cultivation varied significantly. In summary, our data suggest that the B. burgdorferi sensu lato genome is stable during long-term in vitro cultivation.

Three species of Borrelia burgdorferi sensu lato (B. burgdorferi sensu stricto, B afzelii, and B. garinii) identified from cerebrospinal fluid isolates by pulsed-field gel electrophoresis and PCR

A total of 36 European Borrelia burgdorferi sensu lato cerebrospinal fluid isolates (mainly from southern Germany) were analyzed by pulsed-field gel electrophoresis (PFGE) for large restriction fragment pattern (LRFP) and linear plasmid profiles. Analyzing this large panel of isolates, we detected all three species of B. burgdorferi sensu lato pathogenic for humans in cerebrospinal fluid from patients with Lyme neuroborreliosis by PFGE typing after MluI digestion: 21 B. garinii (58%), 10 B. afzelii (28%), and 4 B. burgdorferi sensu stricto (11%) strains as well as 1 isolate with bands characteristic of both B. afzelii and B. garinii. Species classification by PFGE typing was confirmed by 16S rRNA-specific PCR. Eighteen isolates (11 B. garinii, 6 B. afzelii, and 1 B. burgdorferi sensu stricto isolate) were further characterized by LRFP with four different restriction enzymes (ApaI, KspI, SmaI, and XhoI). All B. afzelii isolates showed identical patterns for each restriction enzyme group. Considerable heterogeneity was demonstrated within the B. garinii group. Subsequent analysis of plasmid profiles revealed only marginal differences for B. afzelii strains but different patterns for B. garinii isolates. In one B. afzelii strain we found a linear plasmid of about 110 kbp not described before. LRFP analysis by PFGE is a suitable tool for the molecular characterization of B. burgdorferi sensu lato strains and allows determination not only of the species but also of the subtypes within B. garinii.

Borrelia burgdorferi sensu lato strains isolated from cutaneous Lyme borreliosis biopsies differentiated by pulsed-field gel electrophoresis

25 skin biopsy isolates of Borrelia burgdorferi sensu lato, mainly from German patients with erythema migrans [EM], borrelial lymphocytoma [BL] and acrodermatitis chronica atrophicans [ACA], were species-differentiated using pulsed-field gel electrophoresis (PFGE). The isolates revealed 15 B. afzelii, 8 B. garinii and 2 B. burgdorferi sensu stricto species according to Miu I digestion. All 6 ACA isolates were identified as B. afzelii species, whereas the 2 borrelial lymphocytoma isolates were grouped into B. garinii species. 12 B. afzelii strains, including 4 ACA isolates, were further investigated by digestion with 5 restriction enzymes. Most of the strains revealed an individual pattern. No specific characteristically large restriction fragment pattern (LRFP) could be detected within the ACA and/or EM group. The ACA isolates could not be clearly differentiated from the EM isolates according to the LRFP patterns. PFGE is thus a highly effective method for detecting differences among B. afzelii isolates.