PubMed · 5923740
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1966-11-24. Bacterial interference.. https://doi.org/10.1056/nejm196611242752113
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The inhibitory effect of lactobacilli on growth of Shigella sonnei was studied. The effect was not due to pH alone, as addition of hydrochloric, lactic or acetic acids to culture media did not inhibit the normal growth of the shigellas. The degree of inhibition was measured by disc assay and showed that the inhibitory substance(s) can be extracellular and diffusible, varying the degrees of inhibition depending on the media tested. When broth was inoculated with mixed cultures of Lactobacillus and Shigella strains, the inhibition began at 6 h and the death phase at 9 h. The higher inhibition was produced by the mixture of lactobacilli (35.5 +/- 2.5% at 6 h culture, 57.4 +/- 1.9% at 9 h and 91.2 +/- 1.2% at 14 h). The degree of inhibition was higher when the relationship pathogen : lactobacilli was 1:10(3). The specific growth rate of lactobacilli and shigella was different in pure or mixed cultures. When the lactobacillus alone was grown for 12 h and the shigellas then added, the numbers of shigellas began to decrease immediately at 37 degrees C. This work shows that the Lactobacillus strains employed in fermented milk can be used to inhibit the growth of Sh. sonnei.
Anti staphylococcal activity by clinical isolates of Pseudomonas aeruginosa was tested by the reversed agar plate and the filter paper stamp methods. Almost 40% of Pseudomonas aeruginosa inhibited the growth of both Methicillin resistant Staphylococcus aureus (MRSA) and Methicillin sensitive Staphylococcus aureus (MSSA). Green pigment (Pyocyanin) produced strains showed a strong inhibitory effect against MRSA and MSSA respectively. But some other pigment (Yellow, Red) strains also showed anti staphylococcal activity. These data suggest the colonization of Pseudomonas aeruginosa with anti staphylococcal activity may not be eradicated by the anti pseudomonic antibiotics.
A total of 121 Yersinia enterocolitica O3 isolates from patients with gastroenteritis and 37 Y. enterocolitica reference strains with different O antigens were tested for bacteriocine production and sensitivity. By using cross-streaking method strains belonging to serogroups of O5; O7,8; O7,13; O11; O11,23; O13,27; O17; O19,8 and O34 produced bacteriocin-like substances. None of the Y. enterocolitica O3 strains produced bacteriocin-like material and most of them were uniformly sensitive against the bacteriocin-like material produced by strains of serogroups O7,8; O7,13; O13,27 and O19,8. By sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) significant differences were demonstrated in the whole cell protein patterns of Y. enterocolitica reference strains belonging to different serogroups in the range of 33-47 kilodalton (kDa). Out of the ten examined bacteriocin-like material producer strains only one strain harboured a plasmid of about 60 megadalton (MDa).