No abstract

A predictable 6- to 7-day course of a fatal Leptospira interrogans serovar bataviae infection in experimentally infected mature 110- to 150-g hamsters was used to evaluate the therapeutic efficacy of conventionally used and newer antibiotics. Active drugs were ampicillin, bacampicillin, cyclacillin, piperacillin, mezlocillin, doxycycline, chlortetracycline, cefotaxime, and moxalactam. Cephalexin, cefadroxil, cefamandole, and cefoperazone showed little or no activity in preliminary studies. In delayed treatment studies, all nine active drugs prevented death of hamsters even when treatment was delayed until 1 to 2.5 days before expected time of death. Leptospires in kidneys of surviving animals could be demonstrated in one or more hamsters treated with doxycycline, chlortetracycline, cyclacillin, and piperacillin, but in none of the animals treated with ampicillin, bacampicillin, mezlocillin, cefotaxime, and moxalactam. The potential usefulness of newer penicillins and cephalosporins, as well as ampicillin, chlortetracycline, and doxycycline, for treatment of severe leptospirosis is reported.

The mechanism of reduced sensitivity to the small isometric-headed bacteriophage skl encoded on a 19-kilobase (kb) HpaII fragment subcloned from pKR223 of Lactococcus lactis subsp. lactis KR2 was examined. The reduced sensitivity to phage skl was due to a modest restriction/modification (R/M) system that was not active against prolate-headed phage c2. The genetic loci for the R/M system against skl and the abortive phage infection (Abi) mechanism effective against phage c2 were then localized by restriction mapping, subcloning, and deletion analysis. The restriction gene was localized to a region of a 2.7-kb EcoRV fragment and included an EcoRI site within that fragment. The modification gene was found to be physically separable from the restriction gene and was present on a 1.75-kb BstEII-XbaI fragment. The genetic locus for the Abi phenotype against phage c2 was localized to a region containing a 1.3-kb EcoRI fragment. Attempts to clone the c2 Abi mechanism independent of the skl R/M system were unsuccessful, suggesting that expression of the abi genes required sequences upstream of the modification gene. Some pGBK17 (vector pGB301 plus a 19-kb HpaII insert fragment) transformants exhibited the R/M system against phage skl but lost the Abi mechanism against phage c2. These transformants contained a 1.2to 1.3-kb insertion in the Abi region. The data identified genetic loci on a cloned 19-kb HpaII fragment responsible for restriction activity and for modification activity against a small isometric-headed phage and for Abi activity against prolate-headed phage c2. A putative insertion element was also found to inactivate the abi gene(s).

An albumin polysorbate semisolid medium (Ellinghausen McCullough Johnson Harris medium) gelled with gellan gum (Geirite; Kelco Div., Merck & Co., Inc.) compared favorably with conventional agar media for the cultivation of both pathogenic and saprophytic leptospires. The gellan gum medium supported the growth of all 18 leptospiral strains studied which included an array of serovars with various fastidious growth characteristics. Gellan gum medium was also used advantageously as a long-term maintenance medium; 9-to 12-month-old cultures still contained viable organisms. The colonial growth in gellan gum plating medium of six representative strains was consistent with previously described colonial growth on agar plating media. In addition, gellan gum medium appeared to be an excellent medium for the recovery of leptospires from the blood, liver, and kidneys of hamsters experimentally infected with a virulent Leptospira interrogans serovar bataviae strain. As few as 1 to 10 organisms in the infective tissue could be recovered in semisolid Ellinghausen McCullough Johnson Harris-gellan gum medium. The antigenicity did not appear to be affected by growth in gellan gum medium. The hamster-virulent strain of L. interrogans serovar bataviae isolated from a moribund hamster maintained its virulence after 10 sequential passages in gellan gum medium. Gellan gum medium can be a valuable adjunct to currently used cultural procedures.

Capacitance monitoring is commonly used as an efficient means to gen-