Commercial importance and ability to live in a wide range of salinities have made the common mussel, Mytilus trossulus, a relevant model to study modulation of larval growth and development. We investigated the effects of various salinities combined with neomycin and ampicillin application on Mytilus larvae survival and growth. Both neomycin and ampicillin enhanced trochophore and veliger survival under condition of low salinity. The average veliger size was increasing in accordance with the increase of salinity. In case of neomycin treatment 3.6% of the larvae reached the pediveliger stage. No abnormalities of larval morphology of the FMRFamide and 5-HT systems occurred after 7 days of culturing with both antibiotics.
The role of transient larval FMRFa-ergic neurons of the freshwater snails,
, in osmoregulation and neurodifferentiation was investigated. It was shown that: (i) FMRFa and an FMRFa antibody do not reach their targets when injected into the egg capsule; (ii) long-term incubations of the embryos in neomycin and hyperosmotic solutions of sea water, NaCl and sucrose during the definite developmental stages lead to a special malformation-hydropia; (iii) hydropia coincides with an extensive larval FMRFa-ergic nervous system; (iv) the increased level of FMRFa causes earlier serotonin synthesis by the neurons of the visceral loop ganglia.
Forty-one Salmonella strains, isolated from food samples collected from different parts of Turkey were characterized by various biochemical and genotypic tests. Among 41 isolates, 10 strains harboured at least one plasmid, sizes ranging from 3 kb to 400 kb. The antibiotic resistance profiles of Salmonella isolates were studied against 16 commonly used antibiotics. The highest level of resistance was observed against sulfonamide and neomycin, respectively. Moreover, resistance to multiple antibiotics (5) was also observed among 59% of isolates. Each isolate was also screened for the presence of class 1 integrons and nearly 88% of strains contained class 1 integron with different variable regions (VRs). Further examination of the Salmonella isolates was carried out by testing their clonal relation by RAPD-PCR analyses. With the amplification of primer P1254 the isolates classified into 15 groups and with primer P1283, they classified into 8 groups, on the basis of statistical analyses.
Some Staphylococcus species are frequently recognized as etiological agents of many animal and human opportunistic infections. This is the first report testing the antibiotic resistance-modifying activity of Eugenia jambolanum and Eugenia uniflora against methicillin-resistant Staphylococcus aureus — MRSA strain. In this study, the ethanol extracts of Eugenia jambolanum L., Eugenia uniflora L. and chlorpromazine were tested for their antimicrobial activity alone or in combination with aminoglycosides against an MRSA strain using microdilution method. Synergism between both extracts and all aminoglycosides assayed was demonstrated, except E. jambolanum and tobramycin. In the same form, synergism was observed between chlorpromazine and kanamicin, neomycin and tobramicin, indicating the involvement of an efflux system in the resistance to these aminoglycosides. It is therefore suggested that extracts from E. uniflora L. and E. jambolanum L. could be used as a source of plant derived natural products to modify antibiotic activity of aminoglycosides.
Pasteurella multocida is responsible for economically important diseases in sheep and pigs. Antimicrobial susceptibility studies are essential for initiating rational and effective empirical therapy of P. multocida infections. In this study we investigated the antimicrobial susceptibility to 18 antimicrobial agents of 156 clinical isolates of P. multocida from sheep (n = 87) and pigs (n = 69) using the microdilution method. Both sheep and pig isolates exhibited low levels of resistance (≤ 15%) to ceftiofur, gentamicin, neomycin, spectinomycin, chlortetracycline, tulathromycin, florfenicol, danofloxacin, and enrofloxacin and trimethoprim/sulphamethoxazole, high resistance rates (> 15% up to 50%) to oxytetracycline, tilmicosin, and tiamulin, and very high resistance rates (> 50%) to tylosin tartrate, clindamycin, and sulphadimethoxine. However, sheep isolates exhibited significantly lower percentages of resistance and lower MIC90 values (P < 0.05) than pig isolates for most of the antimicrobials tested. In addition, sheep isolates exhibited also significantly lower phenotypic antimicrobial resistance diversity (8 resistotypes vs. 30 resistotypes). LAC-LIN-SUL-MAC was the resistotype most frequently detected in sheep (39.1%) and LIN-SUL-MAC in pig isolates (26.1%). The differences in susceptibility patterns could be influenced by the lower use of antimicrobials in the small ruminant industry compared with the pig farming industry.
We assessed the possible link between endothelin receptor mediated phosphoinositide breakdown and NO/cGMP signaling pathways in rat arcuate nucleus-median eminence fragments (AN-ME), brain structures known to contain a rich plexus of nitric oxide synthase (NOS)-containing neurons and fibers, together with densely arranged endothelin ETB-receptors-like immunoreactive fibres. Our data show that ET-1, ET-3 and the ETB-receptors agonist, IRL 1620, increased inositol monophosphate (InsP
) accumulation, NOS activity and cGMP formation, in a similar degree. The stimulatory effect of ETs on InsP
accumulation and cGMP formation was inhibited by the phospholipase C (PLC) inhibitor, neomycin, and the absence of extracellular calcium, suggesting that calcium is involved in endothelin receptor-induced PLC activation. The L-arginine analog, L-NAME, inhibited ET-1 or IRL1620-stimulated cGMP formation. The ETA receptor antagonists BQ 123, did not alter, while the ETB receptor antagonists BQ788 inhibited ETs-induced increase in the PI metabolism. NOS activity and cGMP generation. Our data indicate that in AN-ME, ETB receptor signals through receptor-mediated calcium dependent-stimulation of phosphoinositide breakdown and activation of NOS/cGMP signaling pathway.
Enterococci are opportunistic bacteria that cause severe infections in animals and humans, capable to acquire, express, and transfer antimicrobial resistance. Susceptibility to 21 antimicrobial agents was tested by the disk diffusion method in 222 Enterococcus spp. strains isolated from the fecal samples of 287 healthy domestic dogs. Vancomycin and ampicillin minimum inhibitory concentrations (MICs) and high-level aminoglycoside resistance (HLAR) tests were also performed. Isolates showed resistance mainly to streptomycin (88.7%), neomycin (80.6%), and tetracycline (69.4%). Forty-two (18.9%) isolates showed an HLAR to streptomycin and 15 (6.7%) to gentamicin. Vancomycin and ampicillin MIC values showed 1 and 18 resistant strains, respectively. One hundred and thirty-six (61.2%) strains were classified as multidrug resistant and six (2.7%) strains as possibly extensively drug-resistant bacteria. Enterococcus faecium and Enterococcus faecalis were the most prevalent antimicrobial resistant species. Companion animals, which often live in close contact with their owners and share the same environment, represent a serious source of enterococci resistant to several antibiotics; for this reason, they may be a hazard for public health by providing a conduit for the entrance of resistance genes into the community.
Colletotrichum falcatum Went, the
causal agent of red rot of sugarcane produces a specialized infection structure
called appressorium, for penetrating the host. Environmental cues like surface
hydrophobicity and hardness tend to break the dormancy of the conidia and
initiate conidial germination. Conidial attachment is generally stronger on
hydrophobic surfaces, while hydrophilic surfaces do not permit conidial
attachment of C. falcatum. In vitro studies on conidial germination and
appressorium development were made to examine whether the Ca2+/calmodulin
dependent pathways are involved in appressorium formation in C. falcatum.
Effects of calcium chelator (EGTA), calcium channel blocker (methoxy
verampamil), calmodulin antagonists (chloropromazine, phenoxy benzamine and
W-7) and phospholipase C inhibitor (neomycin) were also examined to see whether
they can impair conidial germination and appressorium development. All these
chemicals were found to inhibit conidial germination and or appressorium
formation in C. falcatum. Chloropromazine and W-7 specifically inhibited
appressorium formation at the µM level. Exogenous addition of Ca2+
was found to restore the inhibition of conidial germination and appressorium
development by EGTA. These results suggest that the Ca2+/calmodulin signal
transduction pathway play an important role in the conidial morphogenesis and
appressorium development in C. falcatum.