Maintenance of infective Borrelia burgdorferi Sh-2-82 in 4% oxygen – 5% carbon dioxide in vitro

Abstract

The infectivity of Borrelia burgdorferi depends on the number of passages in Barbour-Stoenner-Kelly (BSK-II) medium in ambient air. In this study the parameters of medium formulation or O2-CO2 atmosphere were altered to define conditions that would retain borrelial infectivity upon serial passage. The infective strain Sh-2-82 was passaged 20 times in BSK-II and BSK-A (a modified BSK-II medium) in ambient O2-CO2 and BSK-II in 4% O2 - 5% CO2 - 91% N2. Spirochetes of every fifth passage were inoculated intraperitoneally into neonatal Lewis rats. Infectivity was lost after 15 passages in media in ambient O2-CO2. However, infectivity was maintained through all 20 passages in BSK-II in 4% O2 - 5% CO2 - 91% N2. There were no pH differences, but the dissolved O2 concentration in ambient O2-CO2 was approximately twice that in 4% O2 - 5% CO2 - 91% N2. Therefore, differences in infectivity were due to culturing under a constant environment of decreased O2 and increased CO2. This environment may place a selective pressure on the borreliae for retention of the infective phenotype. The results suggest that the levels of O2 and CO2 in the environment influence infectivity by preventing the loss of genetic information or inducing the expression of virulence determinants in B. burgdorferi.

Characterization of secA-sod operon in Borrellia burgdorferi.

“…Lactic acid is the primary metabolic end product. This metabolic pathway is consistent with the lack of tricarboxylic acid (TCA) cycle enzymes (Fraser et al, 1997) and the microaerophilic nature of the organism (Austin, 1993). In addition, genes encoding electron transport components are absent in the genome (Fraser et al, 1997); therefore, ATP production occurs exclusively by substrate-level phosphorylation.…”

“…This strain had been isolated from Ixodes scapularis ticks and passaged fewer than 10 times in vitro. Infectivity of Sh-2-82 in neonatal Lewis rats has been described previously (Austin, 1993). A clone of Sh-2-82…”

“…Infectivity of B. burgdorferi depends on the number of serial passages in a low O2 environment. Austin (1993) demonstrated that the infective strain Sh-2-82 was able to retain its infective phenotype after 20 passages in 4% O2…”

“…burgdorferi results in the loss of some plasmids (Norris et al, 1992;Purser and Norris, 2000;Schwan et al, 1988;Xu and Johnson, 1995), changes in protein expression profiles Barbour et al, 1984;Xu et al, 1996) and a loss in the ability of the organism to infect laboratory animals (Austin, 1993;Simpson et al, 1990;Xu et al, 1996) suggesting that plasmids encode important proteins involved in virulence. In a recent study (Purser and Norris, 2000), the presence or absence of specific plasmids was examined and correlated with infectivity phenotype.…”

Borrelioses, agentes e vetores

“…Entretanto, dentro de uma única espécie pode ocorrer pleomorfismo (Bennett 1995). Estes agentes se reproduzem por fissão binária transversal, são microaerófilos (Austin 1993), o que os distingue dos demais gêneros, pois a maioria é aeróbico. Coram-se facilmente pelos corantes derivados da anilina e do Romanovski, são gram negativas, crescem à temperatura de 33°C em meios artificiais e podem ser visualizadas através de microscopia de campo escuro, de contraste de fase ou ainda em tecidos, quando por colorações à base de prata (Barbour & Hayes 1986, Quinn et al 1994.…”