Low Concentrations Of Penicillin Research Articles

Threats to aquatic ecosystems caused by antibiotic-resistant isolate of Escherichia coli from sewage

Abstract The occurrence of Escherichia coli isolate resistant to penicillin and streptomycin in sewage discharged into the environment was tested. Thirty three Escherichia coli isolate were isolated from sewage samples showed different susceptibility to tested antibiotics. All tested isolate show higher resistance to penicillin than streptomycin. Twenty four tested E. coli isolate showed resistance only to low concentrations of penicillin. Five E. coli isolate showed resistance to higher concentrations of penicillin as well (120 μg·dm−3). Five E. coli isolate showed resistance to penicillin and streptomycin. Discharging sewage that contains bacteria isolate resistant to antibiotics into the aquatic environment causes their spreading and increases threats to aquatic ecosystems.

Is Penicillin Plus Gentamicin Synergistic against Clinical Group B Streptococcus isolates?: An In vitro Study.

Group B Streptococcus (GBS) is increasingly causing invasive infections in non-pregnant adults. Elderly patients and those with comorbidities are at increased risk. On the basis of previous studies focusing on neonatal infections, penicillin plus gentamicin is recommended for infective endocarditis (IE) and periprosthetic joint infections (PJI) in adults. The purpose of this study was to investigate whether a synergism with penicillin and gentamicin is present in GBS isolates that caused IE and PJI. We used 5 GBS isolates, two clinical strains and three control strains, including one displaying high-level gentamicin resistance (HLGR). The results from the checkerboard and time-kill assays (TKAs) were compared. For TKAs, antibiotic concentrations for penicillin were 0.048 and 0.2 mg/L, and for gentamicin 4 mg/L or 12.5 mg/L. In the checkerboard assay, the median fractional inhibitory concentration indices (FICIs) of all isolates indicated indifference. TKAs for all isolates failed to demonstrate synergism with penicillin 0.048 or 0.2 mg/L, irrespective of gentamicin concentrations used. Rapid killing was seen with penicillin 0.048 mg/L plus either 4 mg/L or 12.5 mg/L gentamicin, from 2 h up to 8 h hours after antibiotic exposure. TKAs with penicillin 0.2 mg/L decreased the starting inoculum below the limit of quantification within 4–6 h, irrespective of the addition of gentamicin. Fast killing was seen with penicillin 0.2 mg/L plus 12.5 mg/L gentamicin within the first 2 h. Our in vitro results indicate that the addition of gentamicin to penicillin contributes to faster killing at low penicillin concentrations, but only within the first few hours. Twenty-four hours after antibiotic exposure, PEN alone was bactericidal and synergism was not seen.

Development of the radiation-resistant strain of Moraxella osloensis and effect of penicillin G on its growth

A series of repeated exposures to γ-radiation with intervening outgrowth of survivors was used to develop radioresistant cultures of Moraxella osloensis that have been recognized as potential pathogenic microorganism. The D 10 value of the radiation-resistant strain, 5.903±0.006 kGy, was increased by four-fold compared to the parent wild-type strain, 1.637±0.004 kGy. Since most strains of M. osloensis are sensitive to penicillin, we have surveyed the sensitivity of radiation-resistant strain to this antibiotic. When the optical density was monitored after the addition of penicillin G, the radioresistant strain appeared to be more resistant to only a low concentration of penicillin G (0.5 U/ml) than the parent strain. Interestingly, however, there was no apparent difference in the number of viable cells between both strains. Scanning electron microscope data showed that the resistance cells were generally larger than the parent cells, suggesting that this increase in size may cause a higher optical density of radioresistant cells. In conclusion, radiation mutation does not affect the penicillin resistance of M. osloensis.

Microbial nature of the hydrogen-oxidizing agent in hydrogen-treated soil

Experiments have shown that legume soil can promote non-legume plant growth. Although generally attributed to N fertilization of the soil, there are other factors that are additionally responsible. Work has been done in an attempt to characterize this response; fungal agents have been implicated. Other studies have shown H2 to be responsible for plant growth promotion. This work attempts to understand the nature of the H2 uptake agent in soil. The H2 uptake ability of H2-treated soil disappeared when the soil was autoclaved or when glucose was added, suggesting the biotic nature of the H2 uptake agent. Physical disturbance reduced the H2 uptake ability of the soil, indicating the special colonial or long filamentous structure of the H2 uptake agent in soil. The fact that the addition of fungicides did not, in most cases, significantly affect the H2 uptake ability of the soil excluded the fungi as the H2 uptake microorganisms in soil. Addition of antibiotics significantly affected the H2 uptake ability of the soil suggesting the H2 uptake agent in soil is bacterial. The H2 uptake ability of soil was greatly reduced by extremely high concentrations of benomyl and a low concentration of penicillin, indicating that actinomycetes might be the active H2 uptake bacteria in H2-treated soils.

Continuous extraction of penicillin G by emulsion liquid membranes with optimal surfactant compositions

In order to find optimal surfactant compositions of a membrane phase for volume ratios of internal aqueous phase to membrane phase ( w/ o ratios) suitable for continuous extraction of penicillin G, batch extraction by an emulsion liquid membrane (ELM) was studied by varying the volume percentages of Span 80 in a binary surfactant mixture in the membrane phase. The optimal volume percent of Span 80 for each w/ o ratio was 5 or 10% (v/v) of total volume of the binary surfactant mixture. The continuous extraction was investigated using a column of the Oldshue–Rushton type. Total flow rate, w/ o ratio and flow rate of a dispersed emulsion phase were considered as the operational variables for the continuous extraction. In most of the runs, actual degrees of extraction at the bottom of the column were higher than 95%. However, the highest concentration of penicillin G in the internal phase of the emulsion effluent from the column was about 2.4 times higher than that in the influent continuous phase. The low concentration of penicillin G resulted from dilution of the internal phase due to swelling of the emulsion phase. In addition, strategies for reduction of the swelling were investigated.

Enzyme immobilisation on planar and porous silicon substrates for biosensor applications

Two methods for the immobilisation of enzymes on silicon-based so-called electrolyte–insulator–semiconductor (EIS) structures are suggested. These EIS structures are used as a basis for potentiometric biosensors. In the first method, heterobifunctional cross-linker molecules are employed to covalently bind enzymes to these capacitive layer structures which possess a planar surface that contains amine groups. Porous EIS sensors which, in comparison to planar sensors, exhibit an enlarged surface area, are used in the second method. For the first time, pH-sensitive Si 3N 4 was deposited on the walls and bottoms of the SiO 2-covered pores. Here, a large amount of enzyme molecules can adsorptively be bound inside the porous structure. Penicillinase is used as a model enzyme. Capacitance–Voltage and Constant Capacitance measurements are performed in order to examine the respective penicillin sensor responses and thus to validate both immobilisation methods. Whereas the sensitivity of the sensors prepared by both methods is nearly identical for low penicillin concentrations up to around 0.25 mM, a difference of the calibration curves in the higher concentration range indicates a larger amount of immobilised enzyme in the case of the porous structures.

Low concentrations of penicillin partially suppress CA3 hippocampal IPSPs in vitro

Low concentrations of penicillin (50–300 IU/ml) produce a pro-convulsant state in CA3 hippocampus characterized by low amplitude, low frequency (2–3 Hz) spontaneous field potential oscillations. Evoked field potentials were used to demonstrate that this distinct, coordinated behavior of the hippocampal neuronal network which is intermediate between normal activity and fully synchronized epileptiform bursting is the result of partial blockade of GABA A-mediated IPSPs. A new method for estimating the degree of IPSP block relative to convulsant doses of penicillin (2,000 IU/ml) indicates that the half-maximal effect occurs at 300 IU/ml. Fully synchronized bursts may require almost complete IPSP block.

Penicillin treatment accelerates middle ear inflammation in experimental pneumococcal otitis media.

Most Streptococcus pneumoniae strains are killed by very low concentrations of penicillin and other beta-lactam antibiotics, yet middle ear inflammation and effusion persist for days to weeks after treatment in most cases of pneumococcal otitis media. To study the effect of beta-lactam antibiotic treatment on pneumococci and the middle ear inflammatory response during pneumococcal otitis media, we measured concentrations of pneumococci, inflammatory cells, and lysozyme in middle ear fluid (MEF) by using the chinchilla model. Procaine penicillin G given intramuscularly 12 and 36 h after inoculation of pneumococci into the middle ear caused a significant acceleration in the MEF inflammatory cell concentration compared with that in untreated controls, with a significant peak in the inflammatory cell concentration 24 h after pneumococcal inoculation. The lysozyme concentration in MEF also increased more rapidly in treated than in control animals. Viable pneumococci were not detected in MEF after the second dose of penicillin, but the total pneumococcal cell concentration remained unchanged for at least 45 days. Therefore, penicillin treatment accelerated middle ear inflammation while killing pneumococci, but treatment did not accelerate clearance of the nonviable pneumococcal cells from MEF. Further studies will need to define the contribution of these responses to acute and chronic tissue injury.

In vitro response to bactericidal activity of cell wall-active antibiotics does not support the general opinion that enterococci are naturally tolerant to these antibiotics

The incidence of tolerance and paradoxical response to bactericidal activity of penicillin was investigated in 50 clinical isolates of Enterococcus faecalis. Of the isolates tested, 86% exhibited the paradoxical phenomenon whereby there were more survivors at high than at low concentrations above the MIC. Low penicillin concentrations caused decreases equal to or higher than 99.9% in 11 strains, from 99.9 to 99.5% in 23 strains, and lower than 99.5% in 9 strains. Of the total strains, 14% were killed to the same extent by all concentrations above the MIC. The bactericidal activities of other beta-lactams (ampicillin and piperacillin) and other cell wall inhibitors (vancomycin and daptomycin) were also tested against some of these strains. In general, beta-lactams exhibited the best bactericidal activity at 2 x MIC. Piperacillin was the most active, as at 2 x MIC it reduced the original inoculum by 99.9% or more in most of the strains. No concentration of vancomycin above the MIC caused 99.9% killing of the strains, whereas daptomycin was bactericidal at 8 x MIC in most cases. Paradoxical response to bactericidal activity of beta-lactams was abolished by incubation of the inoculum with 2 x MIC before exposure to higher antibiotic concentrations. These findings suggest that enterococci are not always tolerant to cell wall-active antibiotics and that accurate in vitro bactericidal tests may be useful for the choice of appropriate therapy for infections caused by these microorganisms.

Auxotypes, Penicillin Susceptibility, and Serogroups of Neisseria gonorrhoeae from Disseminated and Uncomplicated Infections

We examined auxotypes, penicillin susceptibility, and outer membrane serogroups of 137 strains of Neisseria gonorrhoeae isolated from patients with disseminated gonococcal infection (DGI) and 137 control strains from patients with uncomplicated gonorrhea. We analyzed separately the data for strains isolated from systemic sites in patients with DGI and for strains from local sites in patients with the clinical syndrome of DGI (SDGI) who had negative systemic cultures. We found the nutritional requirement for arginine, hypoxanthine, and uracil (AHU auxotype) significantly more often among DGI strains than among SDGI strains. By using commercially available serogrouping reagents to detect outer membrane protein antigens, we found that regardless of strain auxotype, dissemination correlated best with the presence of protein IA antigens. We did not find that gonococci isolated from DGI are highly susceptible to penicillin. Susceptibility to low concentrations of penicillin correlated only with the AHU requirement, not with serogroup or isolation from a patient with DGI or SDGI.

Helical macrofiber formation in Bacillus subtilis: inhibition by penicillin G.

The folding process required for helical macrofiber formation after the outgrowth of Bacillus subtilis spores was found to be blocked by very low concentrations of penicillin G (1 to 3 ng/ml). Under such conditions, growth and septation without cell separation resulted in characteristic disorganized multicellular structures. Higher concentrations (4 and 10 ng/ml) were needed to inhibit spore outgrowth and vegetative growth, respectively.

Penicillin recovery from aqueous solutions by continuous foam flotation

Penicillin G recovery is investigated in a continuous flotation column in the presence of different collectors which form a complex with penicillin. The performance of the penicillin recovery was investigated as a function of the mole ratio (ϕ) of collector-to-penicillin and the aliphatic chain length of the collector. At ϕ=1 and low penicillin concentrations (e.g., 20 mg·1-1), high foam liquid concentrations (680 mg·l-1), low residue concentrations (12 mg·l-1) and high penicillin separation (56) can be attained. At ϕ=4 the separation increases to 150, and 95% of the penicillin can be recovered.

Human Skin Storage Techniques

The nude mouse model is an excellent technique for studying the viability of stored human skin. In this study Roswell Park Memorial Institute (RPMI) tissue culture medium provided reliable storage of viable human skin for 20 days. Antibiotic concentration plays a role in stored skin viability with low concentrations of penicillin and streptomycin providing adequate bacterial control and improved viability when compared to identical media with high concentrations of the same antibiotics. Addition of fetal calf serum to the storage medium did not improve human skin viability in this experiment.

Effects of low penicillin concentrations on cell morphology and on peptidoglycan and protein synthesis in a tolerant Streptococcus strain.

Rates of protein and peptidoglycan synthesis were determined by pulse-labeling techniques before and after treatment of exponentially growing cultures of Streptococcus mutans FA-1 with a number of concentrations of penicillin G (0.05, 0.1, 0.3, and 0.4 mug/ml). These penicillin concentrations were all less than that required to saturate the specific penicillin-binding sites present on the surface of this organism (0.5 mug/ml), but were all greater than and, in fact, were multiples of the minimum inhibitory concentration (0.02 mug/ml). Low concentrations of penicillin G (2.5x the minimum inhibitory concentration) immediately halted the exponential increase in the rate of peptidoglycan synthesis normally expected as the result of cell multiplication, but allowed the rate of peptidoglycan synthesis occurring at the time of penicillin addition to be maintained for almost 1 h. An increased penicillin concentration (5x the minimum inhibitory concentration) allowed the rate of peptidoglycan synthesis occurring at the time of penicillin addition to be maintained for a shorter length of time (~0.67 h). Still greater penicillin concentrations caused an immediate inhibition of the peptidoglycan synthetic rate. The effect of penicillin on the rate of protein synthesis was similar, although less pronounced. Samples were taken for scanning electron microscopy immediately before and after 3 h of treatment with a low (2.5x the minimum inhibitory concentration) concentration of penicillin. The surface areas and volumes of the cells in these samples were calculated from the electron micrographs by using computer reconstruction techniques. From the frequency distributions of surface area, the plots of surface area to volume ratio as a function of surface area, and the pulse-labeling data mentioned previously, low, growth-inhibitory concentrations (2.5x the minimum inhibitory concentration) of penicillin are proposed (i) to inhibit the constriction of the division septum, (ii) to prevent the establishment or maturation of new envelope growth sites, and (iii) to have no immediate effects on the synthesis of cell wall peptidoglycan already in progress at the time of penicillin addition.

Events leading to cell death and lysis of Neisseria meningitidis in low concentrations of penicillin G.

Neisseria meningitidis SD1C exhibited a low tolerance to penicillin G (0.03 microgram/ml). Loss of viability in the absence of polyvinylpyrrolidone-40 and horse serum was independent of the concentration of antibiotic above the minimum inhibitory concentration, whereas the rate of bacteriolysis was concentration dependent. Penicillin-induced lysis was a secondary event in this organism. At low levels of penicillin G, growth characteristics, i.e., absorbancy changes, respiratory rate, and uptake of Mg2+, appeared normal during the first 90 min in penicillin; however, viability dropped dramatically. Additionally, total cell numbers remained constant while cell mass continued to increase at a rate normal for the population. The increase in cellular mass in the absence of cell division could be observed microscopically. Only one ultrastructural change induced by penicillin correlated with the loss in viability: the loss in continuity of the outer membrane with the peptidoglycan but only at the site of septum formation. This lesion did not occur when cells were grown in media supplemented with the protective agents polyvinylpyrrolidone-40 and horse serum. Under these conditions of growth and with relatively high levels of penicillin, constant viability was maintained, but cell division no longer occurred. Cell populations treated with penicillin in the presence of the protective agents became increasingly more dependent on the presence of these agents for total viability even in the absence of penicillin in the culture.

Interaction of Bacteriophage Infection and Low Penicillin Concentrations on the Performance of Yogurt Cultures

Bacteriophage infection of a mixed-strain Streptococcus thermophilus culture, one strain of which is phage sensitive and the other phage resistant, may induce lysis of both strains. Experiments were carried out with three different phage-resistant strains. One such strain lysed in penicillin-free growth medium and another needed penicillin G (0.005 IU/ml) for lysis, while the third strain continued to grow in the presence of this concentration of antibiotic. Growth of the latter strain was inhibited when the medium contained a relatively high concentration of phage lysin. The different penicillin concentrations required to induce "lysis from without" of these phage-resistant strains correlated with their individual sensitivities to the antibiotic. The apparent relationship between the sensitivities of these strains to penicillin and to phage lysin could be explained by a difference in the degree of polymerization of the cell wall peptidoglycan.

Penicillin effects on iontophoretic responses in Aplysia californica

The effect of penicillin on neurons of Aplysia californica was studied using drug concentrations which would be convulsant in mammalian nervous systems. Iontophoretic responses were elicited by the application of acetylcholine, dopamine, gammaaminobutyric acid and serotonin. Low concentrations of penicillin (2m M) consistently and reversibly reduced the chloride-dependent hyperpolarizing responses by approximately 70%, regardless of the transmitter required to evoke them. The short depolarizing responses which are sodium sensitive are slightly reduced by a much higher (10m M) concentration. The extent of the reduction of the excitatory response varied with the transmitter. The slow sodium-dependent depolarizations and the slow potassium-dependent hyperpolarizations were unaffected by the concentrations of penicillin used. The possibility that the convulsant effect of penicillin is due to interference with membrane conductance to chloride is discussed.

Unusual Effects of Penicillin G and Chloramphenicol on the Growth of Moraxella osloensis

Growth of exponential-phase liquid cultures of Moraxella osloensis was inhibited by 0.5 U of penicillin G per ml. For this organism, low concentrations of penicillin acted primarily in a bacteriostatic rather than in a bactericidal manner. At higher concentrations of penicillin some killing did take place, but the rate of killing was rather slow and appeared to be independent of penicillin concentration. Microscopic observation of cells from penicillin-treated cultures showed little or no cellular swelling or lysis. The total cell count did not decrease significantly during 6 h of incubation in 5,000 U of penicillin per ml. The rates of respiration, nucleic acid synthesis, and protein synthesis were not affected by the presence of penicillin. Attempts to counteract the bactericidal action of high concentrations of penicillin with growth inhibitory concentrations of chloramphenicol were unsuccessful, since chloramphenicol itself was more bactericidal than penicillin for M. osloensis.

A Collaborative Study of the Delvotest-P Method to Detect Low Concentrations of Penicillin in Milk

During a collaborative study at a large number of milk-receiving stations from a dairy industry in the Netherlands, in which penicillin was added in various concentrations of 0, 4, 5, 6, 7, 8 and 10 IU/1 to milk samples, the Delvotest-P method gave reliable results in almost all instances. Of the 22 milk samples that were tested, both undiluted and dilluted 1:1, by up to 17 control stations in seven experiments, a total of 518 readings were obtained. There were no negative readings among the 249 samples that contained 4 or more IU penicillin per liter and only one doubtful reading among 186 samples that were free of penicillin. In some instances the test was found a little more sensitive than one might conclude from the instructions.

Penetration of penicillin into human phagocytes containing Neisseria gonorrhoeae: intracellular survival and growth at optimum concentrations of antibiotic.

Phagocytes obtained from fresh human buffy coat (predominantly polymorphonuclear phagocytes) or from human buffy coat which had been incubated on a glass surface for 1 to 3 days (predominantly mononuclear phagocytes) were allowed to ingest gonococci, and then incubated with penicillin. More intracellular gonococci were killed at high than at low penicillin concentrations, indicating that penicillin penetrated the phagocytes. This was supported by autoradiography experiments with radiolabelled penicillin. A pilated, small-colony-forming gonococcal strain survived and multiplied for at least 15 h in polymorphonuclear phagocytes which were incubated with penicillin at the optimum concentration for killing the extracellular bacteria but not the intracellular ones; whereas a non-pilated, large-colony-forming strain survived for only 10 h. The former strain survived for at least 6 h in similar experiments with mononuclear phagocytes. Intracellular survival and in growth may be an important facet of the pathogenicity of gonococci.