Antibiotic penetration through the blood-brain barrier in rats and the effect on this process of proteolytic enzymes]

Penetration of penicillin, ampicillin, oxacillin, tetracycline, streptomycin and gentamycin through the hemato-encephalic barrier in rats and effect of proteolytic enzymes on the above process were studied comparatively. The levels of penetration to the brain were highest for ampicillin, then followed penicillin, tetracycline, oxacillin, streptomycin and gentamycin. Preliminary intramuscular administration of trypsin and chimotrypsin (10 mg/kg) to the animals had no effect on permeability of the hemato-encephalic barrier for the antibiotics tested, except penicillin. Higher levels of the antibiotics in the brain tissue may be explained by higher antibiotic blood levels under the effect of proteolytic enzymes.     

Effect of some antibiotics on semi-circular canal activity in the frog (Rana esculenta)]

We have studied the action of two ototoxic antibiotics (streptomycin and gentamycin) on the activity of the horizontal semicircular canal in comparison with those of penicillin and 7 g/1 NaCl solution, all of them being injected into the labyrinthic cavity. Only streptomycin and gentamycin have a specific action, and the one of streptomycin is much more important than the one of gentamycin.     

Sensitivity of Sherman's propionic acid bacilli to antibacterial preparations and vitamin B12 synthesis

Sherman propionic acid bacilli were sensitive to benzylpenicillin, ampicillin, ceporin, tetracyclines, oleandomycin, oletetrin, tetraolean, sigmamycin, levomycetin and furadonine. Methicillin, oxacillin, monomycin, kanamycin, polymyxin and furazolidone had an insignificant effect on the above organism. The subbacteriostatic concentrations of methicillin, oxacillin, streptomycin, monomycin, kanamycin, neomycin, tetraolean, sigmamycin, polymyxin M and ristomycin increased the biosynthesis of vitamin B12 by Sherman propionic acid bacilli, while benzylpenicillin, ampicillin, tetracyclines, oleandomycin, oletetrin, levomycetin and furadonine in the subbacteriostatic concentrations inhibited this process.     

The sensitivity to 12 antibiotics of 125 strains of Streptococcus group B isolated in a maternity home

Sensitivity of 125 strains of group B streptococci isolated from newborns, their mothers and personnel in a maternity home was studied with respect to 12 antibiotics: benzylpenicillin, ampicillin, methicillin, cephalotin, erythromycin, lincomycin, levomycetin (chloramphenicol), oxacillin, tetracycline, streptomycin, gentamicin and ristomycin. The method of serial dilutions in a solid medium was applied. All the strains were sensitive to ristomycin and erythromycin. The predominating number of the strains were sensitive to lincomycin, levomycetin and the beta-lactam antibiotics. Strains resistant or moderately resistant to benzylpenicillin, ampicillin, oxacillin, methicillin and cephalotin were detected. The majority of the strains were resistant to streptomycin, tetracycline and gentamicin. Multiple antibiotic resistance with 2-7 determinants was revealed in 11.2 per cent of the strains. The antibiotic sensitivity of the strains isolated from the newborns, their mothers and the personnel in the maternity home was on the whole similar or insignificantly differed.     

Primmorphs from seven marine sponges: formation and structure

Primmorphs were obtained from seven different marine sponges: Stylissa massa, Suberites domuncula, Pseudosuberites aff. andrewsi, Geodia cydonium, Axinella polypoides, Halichondria panicea and Haliclona oculata. The formation process and the ultra structure of primmorphs were studied. A positive correlation was found between the initial sponge-cell concentration and the size of the primmorphs. By scanning electron microscopy (SEM) it was observed that the primmorphs are very densely packed sphere-shaped aggregates with a continuous pinacoderm (skin cell layer) covered by a smooth, cuticle-like structure. In the presence of amphotericin, or a cocktail of antibiotics (kanamycin, gentamycin, tylosin and tetracyclin), no primmorphs were formed, while gentamycin or a mixture of penicillin and streptomycin did not influence the formation of primmorphs. The addition of penicillin and streptomycin was, in most cases, sufficient to prevent bacterial contamination, while fungal growth was unaffected.     

Immunocorrecting properties of antibiotics in secondary immunodeficiency]

The study investigated immunocorrecting properties of penicillin G, streptomycin, gentamycin in cyclophosphamide--induced immunodeficiency in mice. It was determined, that antibiotics in sub-bactericidal doses possess pronounced immunocorrecting properties. This effect was observed in both humoral and cell-mediated immune response.     

Properties of Serratia marcescens strains isolated in septic diseases of newborn infants

As the result of the study of blood and liquor samples from 120 newborns, Serratia marcescens was isolated in 21 cases (17.5 %). 8 strains were isolated from the environment of these patients. Almost all strains isolated from both the patients and the environment (with the exception of one environmental strain) belonged to serotype 04. The isolated S. marcescens strains were resistant to penicillin, ampicillin, streptomycin, kanamycin, oxacillin, methicillin, ceporin and moderately sensitive to polymixin. 2 strains from the environment and 9 strains from the patients were mildly sensitive to gentamicin. In one hospital all isolated strains were found to have 2 transmissive R plasmids with the molecular weight 40 and 60 megadaltons. The presence of R plasmids with the same molecular weight in all S. marcescens strains isolated in this hospital, as well as their serological identity, suggest that in all patients infection originated from a common source.     

Determination of Antibiotic Susceptibility of Rickettsia by the Plaque Assay Technique

Plaque formation by various rickettsiae was completely inhibited by commercial antibiotic discs impregnated with tetracycline, chloramphenicol, nitrofurantoin, and erythromycin; partial inhibition was observed around discs containing nalidixic acid and sulfisoxazole, but no inhibition was seen around discs containing cephalothin, ampicillin, oxacillin, kanamycin, polymyxin B, streptomycin, or penicillin.     

Antibiotic sensitivity of the causative agents of suppurative surgical infection]

Sensitivity of 1492 strains of the causative agents of the surgical purulent infections, i. e. pathogenic Staphylococcus, Proteus, Ps. aeruginosa and E. coli to benzylpenicillin, streptomycin, levomycetin, tetracycline, erythromycin, oleandomycin, monomycin, kanamycin, novobiocin, ampicillin, oxacillin, ceporin, gentamicin and rifampicin was studied. Gentamicin was most active against all the bacterial species tested. The staphylococci were in addition sensitive in a high percentage of the cases to rifampicin, novobiocin, ceporin, monomycin and kanamycin. The isolates of E. coli were in addition sensitive to ceporin, monomycin and kanamycin. Sensitivity of the strains of Ps. aeruginosa and Proteus was low to all of the antibiotics except gentamycin. Most of the strains of the causative agents of the surgical purulent infections were multiresistant to 4 antibiotics. The number of the staphylococcal strains sensitive to benzylpenicillin, streptomycin and levomycetin increased in 1976 as compared to 1975 on the background of a limited use of these antibiotics in clinics.     

Detection of methicillin-resistance (mec-A) gene inStaphylococcus aureus strains by PCR and determination of antibiotic susceptibility

Methicillin-ResistantStaphylococcus aureus (MSRA) has become a frequent cause of serious infections. Extended hospitalization and antibiotic therapy have been identified as additional risk factors for MRSA carrier and infection. The aim of this study was to determine the incidence of MRSA infections in the hospitals affiliated to Hamedan University of Medical Sciences. SeventyS. aureus clinical strains were isolated from patients from June 2005 to June 2006 and examined by PCR and conventional microbiological tests. Then, the antibiotic susceptibility to methicillin/oxacillin and other antibiotics were performed by Disc Diffusion Agar (DDA). The results of this study showed that methicillin resistance gene was detected in 35 (50%) and 22 (31.4%) cases by PCR and DDA, respectively. The results of antibiotic susceptibility assays also showed there were high resistance MRSA strains to penicilin (100%), cloxacillin (91.4%), tetracycline (74.2%), cotrimoxazole (68.5%), erythromycin (68.5%) and less resistance to rifampin (11.4). Two MRSA also had decreased susceptibility to vancomycin. But the strains of Methicillin-SensitiveS. aureus (MSSA) showed high sensitivity to all antibiotics profiles except to penicillin (complete resistance). As a conclusion, the resistance to methicillin/oxacillin ofS. aureus in Hamedan hospitals has reached to 50% and they show multidrug resistance.     

High-Level Oxacillin and Gentamycin Resistance with Reduced Susceptibility to Vancomycin in <Emphasis Type="Italic">Staphylococcus aureus-</Emphasis>Carrying <Emphasis Type="Italic">mecA</Emphasis> and <Emphasis Type="Italic">femA</Emphasis> Gene Complex

Staphylococcus aureus oxiva 10 and oxiva 14 strains clinically isolated from diabetic patients were resistant to gentamycin and oxacillin The minimal inhibitory concentrations (MICs) of oxacillin and gentamycin were 720 and >2048 μg/mL, respectively, for oxiva 10 and 680 and 400 μg/mL. respectively, for oxiva 14; both strains carry mecA and femA genetic determinants in their genomes. In addition, both are vancomycin-intermediate Staphylococcus aureus (VISA) isolates. The addition of vancomycin led to significant decreases in oxacillin resistance of both oxiva 10 and oxiva 14 strains, whereas the addition of vancomycin to gentamycin plates showed a decrease in gentamycin resistance of non-high-level gentamycin-resistant (non-HLGR) oxiva 14 and indifference in gentamycin resistance in HLGR oxiva 10. Transmission electron microscopy of representative strains unveils a remarkable increase in the thickness of the cell wall, indicating that thickening of the cell wall is a common phenotype associated with vancomycin resistance in VISA isolates. The present study reports that the rate of synergism and synergistic effect in the combination vancomycin–gentamycin vary according to the MICs of gentamycin.     

Susceptibility of Rhodobacter sphaeroides to beta-lactam antibiotics: isolation and characterization of a periplasmic beta-lactamase (cephalosporinase).

Thirteen strains of the gram-negative, facultative phototrophic bacterium Rhodobacter sphaeroides were examined fro susceptibility to beta-lactam antibiotics. All strains were sensitive to the semisynthetic penicillins ampicillin, carbenicillin, oxacillin, cloxacillin, and methicillin, but 10 of the 13 strains were resistant to penicillin G, as well as a number of cephalosporins, such as cephalothin, cephapirin, and cephalosporin C. A beta-lactamase (EC 3.5.2.6) with strong cephalosporinase activity was detected in all of the resistant strains of R. sphaeroides. With strain Y-1 as a model, it was shown that the beta-lactamase was inducible by penicillin G, cephalosporin C, cephalothin, and to some minor extent, cephapirin. The beta-lactamase was located in the periplasmic space, from which it could be extracted by osmotic shock disruption. By using this fraction, the beta-lactamase was purified 34-fold to homogeneity by steps involving batch adsorption to and elution from DEAE-Sephadex A50, chromatography on Q-Sepharose, and preparative polyacrylamide gel electrophoresis. The molecular masses of the native and denatured enzymes were determined to be 38.5 kilodaltons by gel filtration and 40.5 kilodaltons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively, indicating a monomeric structure. The isoelectric point was estimated to be at pH 4.3. In Tris hydrochloride buffer, optimum enzyme activity was measured at pH 8.5. The beta-lactamase showed high activity in the presence of the substrates cephalothin, cephapirin, cephalosporin C, and penicillin G, for which the apparent Km values were 144, 100, 65, and 110 microM, respectively. Cephalexin, cepharidine, and cephaloridine were poor substrates. The beta-lactamase was strongly inhibited by cloxacillin and oxacillin but only slightly inhibited by phenylmethylsulfonyl fluoride or thiol reagents such as iodoacetate and p-chloromercuribenzoate.     

Antibiotic interaction with proteolytic enzymes]

The effect of penicillin, tetracycline, aminoglucozide antibiotics and streptomycin on BAEE-esterase activity of trypsin was studied. It was found that benzylpenicillin in amounts of 50, 100 and 300 mg, ampicillin in an amount of 25 mg, methicillin in an amount of 12 mg and tetracycline in an amount of 2.5 mg as calculated per 1 mg of trypsin had no effect in vitro on the esterase activity of the enzyme. Neomycin, kanamycin and streptomycin in amounts of 5, 10, 100 or 300 mg per 1 mg of trypsin catalyzed splitting of BAEE by trypsin. When the antibiotics were added to the bile, its esterase activity increased. Preliminary intramuscular administration of trypsin and kanamycin to the rats had no effect on the ampicillin levels in the blood serum and brain and did not affect the permeability of the hemato-encephalic barrier as compared to the use of trypsin alone.     

Drug Resistance as Influenced by Inactivated Sensitivity Discs

Reports of staphylococci resistant to the semisynthetic penicillins stimulated a study of the factors influencing the stability of the drugs in discs. The behavior of penicillin G, methicillin, oxacillin, cloxacillin, and cephalothin discs under different humidity and temperature conditions is described. Humidity was found to be the most significant factor in drug inactivation. Storage of discs in a vacuum desiccator at -20 C provides maximal antibiotic stability.     

Sensitivity of Shigella to antibiotics]

Three hundred and twenty two Shigella cultures isolated from dysentery patients within 1986-1989 were tested with the use of standard paper disks for their sensitivity to levomycetin, streptomycin, tetracycline, monomycin, neomycin, kanamycin, erythromycin, gentamicin, carbenicillin, ampicillin, oxacillin, methicillin and doxycycline. The number of the cultures belonging to Shigella sonnei amounted to 85.1 per cent of the total number of the strains studied. 91.9, 89.5, 87.3, 87.3, 80.1 and 80.1 per cent of the cultures were sensitive to gentamicin, kanamycin, carbenicillin, neomycin, levomycetin and ampicillin, respectively. 99.4 per cent of the isolates were resistant to streptomycin and 97.2 per cent were resistant to tetracycline. The sensitivity to erythromycin remained rather high (70.2 per cent). The overwhelming majority of the Shigella sonnei isolates had multiple resistance.     

New Combination of Antibiotics for Treatment of Contaminated Specimens for Viral Studies

A study of a new combination of antibiotics (sodium oxacillin, colistin sulfate, and amphotericin B) has shown that 30 μg/ml of each in tissue culture maintenance medium can inhibit a group of the commonest bacterial and fungal contaminants while causing no observable cytopathology in rhesus monkey kidney, HeLa, or human amnion tissue cells. In addition, there was no inhibition of the titers of poliovirus, echovirus, coxsackievirus, and adenovirus in the three cell lines. Ten duplicate fecal samples, which remained contaminated with fungal or Pseudomonas organisms after treatment with penicillin and streptomycin, were treated with the new antibiotic combination. Contaminants were controlled in each, and a variety of viruses was recovered.     

Incidence of Staphylococcus aureus isolated from patients treated at the Clinical Center of Skopje, Macedonia, with special attention to MRSA

The distribution of 3497 Staphylococcus aureus strains according to methicillin resistance, specimens, departmental profession and antibiotic resistance patterns was analysed. The strains were cultured from the patients of the Clinical Center of Skopje, Macedonia, between 1 January 2002 and 31 December 2004. The majority of the isolates was obtained from suppurated wounds (28.5%), nares (21%), intratracheal tubes (13%) and blood cultures (11.8%). Overall 1100 (31.4%) of the isolates was methicillin-resistant with 1 microg oxacillin disc. Of these 35.5%, 30.5% and 10.4% were cultured from wounds, intratracheal tubes and blood samples, respectively. The prevalence of MRSA strains was 78.6%, 75%, 44.2% and 37.3% in specimens of ICU, Coma Center, General Surgery and Haematology patients. There were extremely big differences in the frequency of MRSA between departments with particular specialisation. The 2397 MSSA isolates belonged to practically one antibiotic resistance pattern characterised with penicillin resistance and susceptibility to other antistaphylococcal drugs. The 1100 MRSA isolates distributed to four antibiotic resistance patterns on the basis of their resistance to oxacillin, penicillin, amoxicillin+clavulanic acid, azithromycin, clindamycin, amikacin, gentamicin, ciprofloxacin, trimethoprim+sulphamethoxasole, vancomycin and teicoplanin. All the MRSA isolates were multidrug resistant but sensitive to glycopeptides.     

Increase in cell size and acid tolerance response in a stepwise-adapted methicillin resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> mutant

A methicillin-susceptible strain of Staphylococcus aureus (MSSA) showed stepwise adaptation when grown in increasing concentrations of oxacillin, eventually reaching a maximum of 35 μg/ml. The resultant oxacillin resistant mutant strain was stable and did not revert to susceptibility on frequent subculturing. The response of the cells to different concentrations of oxacillin was examined by scanning electron microscopy, which showed that the size of the bacterium increased with increasing concentrations of oxacillin. These changes in cell size were dependent on the concentration of oxacillin and occurred only after addition of non-lethal concentrations. In the presence of lethal concentrations (≥35 μg/ml) that completely inhibited cell growth, the cell sizes were smaller than those of wild-type cells and irregular in shape. This stepwise-adapted methicillin (oxacillin) resistant S. aureus (MRSA) mutant showed a greater acid tolerance response (ATR) to lactic and citric acids than the parent susceptible strain. These data indicates that methicillin resistance alters the morphology and ATR in stepwise-adapted MRSA mutant cells.     

Antibiotic sensitivity of beta-hemolytic Streptococcus group A on a new nutrient medium for the cultivation of streptococci

Sensitivity of 167 strains of beta-hemolytic streptococci of group A was studied with the method of serial dilutions on a solid agar medium for cultivation of streptococci. The medium was developed at the I. I. Mechnikov Research Institute of Vaccines and Sera. It does not require addition of blood or serum. The strains were found to be highly sensitive to penicillin, cephalothin and erythromycin. The number of the strains resistant to tetracycline, streptomycin, gentamycin, levomycetin (chloramphenicol) and ristomycin amounted to 51, 36, 23, 1.8 and 1.8 per cent, respectively. One of the strains (0.6 per cent) was resistant to lincomycin. Strains with multiple resistance were isolated. The necessity of regular control of distribution of antibiotic resistance among staphylococci is indicated.     

Susceptibility of various purple and green sulfur bacteria to different antimicrobial agents

Abstract Several purple and green sulfur bacteria (genera Chromatium, Thiocapsa and Chlorobium ) were tested for their sensitivity to different antimicrobial agents by a disc diffusion assay, using thioacetamide as a source of hydrogen sulfide for plate growth. Chlorobium limicola strains were more sensitive to amoxicillin, erythromycin and nalidixic acid, whereas gentamicin and netilmicin were more active against the purple bacteria tested. None of the organisms were sensitive to oxacillin and trimethoprim + sulfamethoxazole. The critical concentrations at the edge of the inhibition zone were also calculated for three organisms and the antimicrobials colistin, mitomycin C, penicillin G, rifampicin, and streptomycin. The results obtained suggest that colistin, mitomycin C, penicillin G would provide selective conditions against the growth of Chlorobium limicola strains, while streptomycin and other aminoglycoside antibiotics would select against purple bacteria.