PubMed · 14469215
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
I MANDL, S KELLER, B COHEN. 1962. Microbial elastases. A comparative study.. https://doi.org/10.3181/00379727-109-27379
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Binding isotherms and heats of interaction have been determined at 15, 25, and 40 degrees C for a coaggregating and a non-coaggregating oral bacterial pair. Heats of interaction were measured upon three consecutive injections of streptococci into an actinomyces suspension using isothermal titration calorimetry. After each injection, the number of streptococci injected remaining free in suspension was quantified microscopically and the degree of binding between the two bacterial strains was established. The coaggregating pair shows positive cooperative binding. The highest cooperativity, at 25 degrees C, correlates with a strong, macroscopically visible coaggregation. The non-coaggregating pair shows low cooperativity and lacks macroscopically visible coaggregation. Interactions between the coaggregating partners seem to be mainly due to specific, enthalpically saturable and favorable binding sites. Even though the enthalpic part of the interaction is saturated, cooperativity increases with consecutive injections, implying that the coaggregation phenomenon is driven by entropy gain. The change in heat capacity (DeltaC(p)) is positive for the non-coaggregating pair from 15-40 degrees C as well as for the coaggregating pair beyond 25 degrees C. At lower temperatures the coaggregating pair causes a negative DeltaC(p). The decrease in heat capacity together with an increase in entropy is considered to be indicative of hydrophobic interactions playing an important role in the formation of large coaggregates as observed for the coaggregating pair at 25 degrees C.
[reaction: see text] Primary metabolic precursors for K-26, a naturally occurring tripeptide phosphonic acid from Actinomyces sp. K-26, are investigated by heavy-atom isotope labeled substrate incorporation experiments. A highly sensitive selected reaction monitoring (SRM)-based method for isotopic incorporation estimation in natural products is reported. The incorporation of heavy-atom isotope labeled tyrosine compounds into the (R)-1-amino-2-(4-hydroxyphenyl)-ethylphosphonic acid moiety of compound K-26 suggests a new mechanism of biosynthesis of phosphonate functionality in natural products.
OBJECTIVE: This study was conducted to assess the susceptibility of human clinical isolates of Actinomyces species to 12 antimicrobial agents. METHODS: Human clinical isolates of Actinomyces spp. were collected from stored collections held at the Microbiology Department, Edinburgh University, Anaerobe Reference Laboratory, Cardiff, Glasgow Dental Hospital and Glasgow Royal Infirmary. Each isolate was identified by restriction analysis of amplified 16S ribosomal DNA. MICs of 12 antibiotics comprising benzyl penicillin, amoxicillin, ceftriaxone, linezolid, tetracycline, deoxycycline, clindamycin, erythromycin, clarithromycin, ciprofloxacin, meropenem and piperacillin/tazobactam for 87 strains of Actinomyces species were obtained by Etest methodology. RESULTS: The Actinomyces species identified for this study comprised: Actinomyces israelii, Actinomyces gerencseriae, Actinomyces turicensis, Actinomyces funkei, Actinomyces graevenitzii and Actinomyces europaeus. All isolates were susceptible to penicillin and amoxicillin. All but one strain of A. turicensis was susceptible to linezolid. A number of A. europaeus and A. graevenitzii isolates were resistant to ceftriaxone and piperacillin/tazobactam. A number of isolates of A. turicensis and A. europaeus also demonstrated resistance to erythromycin. All Actinomyces species tested appeared resistant to ciprofloxacin. CONCLUSIONS: Actinomyces species appear to be susceptible to a wide range of beta-lactam agents and these, when combined with beta-lactamase inhibitors, should be regarded as agents of first choice. Ciprofloxacin performed poorly. Tetracyclines also demonstrated poor performance. This is the first study of antimicrobial susceptibilities for a number of accurately identified clinical isolates of Actinomyces spp. There are a number of species differences in susceptibility profiles to the antimicrobials tested, suggesting that accurate identification and speciation may have an impact on clinical outcome.