Determination of yolk contamination in liquid egg white using Raman spectroscopy.

Purified egg white is an important ingredient in a number of baked and confectionary foods because of its foaming properties. However, yolk contamination in amounts as low as 0.01% can impede the foaming ability of egg white. In this study, we used Raman spectroscopy to evaluate the hypothesis that yolk contamination in egg white could be detected based on its molecular optical properties. Yolk contaminated egg white samples (n = 115) with contamination levels ranging from 0% to 0.25% (on weight basis) were prepared. The samples were excited with a 785 nm laser and Raman spectra from 250 to 3,200 cm(-1) were recorded. The Raman spectra were baseline corrected using an optimized piecewise cubic interpolation on each spectrum and then normalized with a standard normal variate transformation. Samples were randomly divided into calibration (n = 77) and validation (n = 38) data sets. A partial least squares regression (PLSR) model was developed to predict yolk contamination levels, based on the Raman spectral fingerprint. Raman spectral peaks, in the spectral region of 1,080 and 1,666 cm(-1), had the largest influence on detecting yolk contamination in egg white. The PLSR model was able to correctly predict yolk contamination levels with an R(2) = 0.90 in the validation data set. These results demonstrate the capability of Raman spectroscopy for detection of yolk contamination at very low levels in egg white and present a strong case for development of an on-line system to be deployed in egg processing plants.

Membrane stabilizers inhibit potassium efflux from Staphylococcus aureus strain No. U2275.

The effect of different categories of membrane stabilizers on K+ loss and growth has been characterized in a culture of Staphylococcus aureus. Chlorpromazine, thiopental and tetracaine at low concentrations produced a marked inhibition of K+ loss and an equivalent increase in the K+ contents of S. aureus. Whereas the inhibitory effect of chlorpromazine on K+ loss was observed at lower than bacteriostatic concentrations of the drug, thiopental had no effect on growth in the concentration range where K+ loss was maximally inhibited. It is concluded that the bacteriostatic action of chlorpromazine is probably not related to its membrane stabilizing effect only.

In vitro susceptibility of 124 Xanthomonas maltophilia (Stenotrophomonas maltophilia) isolates: comparison of the agar dilution method with the E-test and two agar diffusion methods.

The in vitro susceptibility of 124 Xanthomonas maltophilia isolates was tested by four methods: Agar dilution (reference method), E-test, a disk diffusion and a tablet diffusion method. Trimethoprim-sulfamethoxazole had the highest activity against X. maltophilia, followed by a combination of aztreonam-clavulanic acid at different ratios, the ratio 1:1 being the most active with a susceptibility rate of 85% as compared to 2% for aztreonam alone. Addition of the beta-lactamase inhibitor tazobactam to piperacillin enhanced the rate of susceptible isolates from 31% to 53%, Relatively few isolates were susceptible to ciprofloxacin (27%) and gentamicin (9%). Generally, the disk diffusion method had a considerably higher frequency of "very major" discrepancies when compared with the agar dilution method than with the other methods. The susceptibility of X. maltophilia to trimethoprim-sulfamethoxazole and ciprofloxacin could reliably be determined by all the diffusion methods tested, but otherwise the agar dilution method is to be preferred. A standardized and reliable diffusion method for susceptibility testing of X. maltophilia remains to be found. Trimethoprim-sulfamethoxazole must be considered the drug of choice in the treatment of severe X. maltophilia infections. The combination aztreonam-clavulanic acid is promising, but must be proved in a clinical setting.

Mechanism of aminoglycoside resistance in Danish Staphylococcus aureus strains during the years 1979-1987.

A total of 49 gentamicin-resistant strains of Staphylococcus aureus isolated from blood (n = 26) or from other sites (n = 23) during the years 1979 to 1987 were evaluated for the presence of aminoglycoside-inactivating enzymes on the basis of minimum inhibitory concentrations measured by agar dilution as well as inhibition zone diameters determined by disc diffusion. Enzymatic activity was caused by AAC (6')III/APH (2") in 45 strains, and by AAC (6')III/APH (2") + APH (3') in four strains. No changes in the distribution of enzymatic activity were observed during the eight years.

Trichloroethylene: effects on body and organ weights in mice, rats and gerbils.

The influence of continuous inhalation of 150 ppm trichloroethylene (TCE) on body, liver, spleen, and kidney weights in rats, mice, and mongolian gerbils was tested. An age dependent decrease in body weight gain was observed in female rats exposed to TCE. All 3 species showed liver enlargement caused by the exposure. The effect was much more pronounced in mice, in which the increase was 60--80%, than in rats and gerbils where it was only 20--30%. After the end of the TCE-exposure the liver weights of the mice decreased rapidly. After 5 days of rehabilitation the weight was only 10--20% higher than that of the controls. This difference persisted for at least 25 days. The spleen weight appeared unaffected or somewhat smaller in TCE-exposed animals of all species. An increased kidney weight (15%) was observe din TCE-exposed gerbils. This effect was less pronounced in mice and rats. Effects on the liver have earlier been seen only after exposure to concentrations much higher than that used in the present study. This difference in results is proposed to be due to the different schedules used for the exposure.

Combined effect of benzylpenicillin and gentamicin/netilmicin on Streptococcus faecalis.

The 50% inhibitory concentrations (IC50) of gentamicin and netilmicin were determined for 55 clinical isolates of Streptococcus faecalis, approximately half of which were recovered by culture of blood samples from patients with endocarditis. The IC50 for gentamicin was less than 5 micrograms/ml for 22 strains and less than 40 micrograms/ml for all strains, and for netilmicin the IC50 was less than 5 micrograms/ml for 51 strains and less than 40 micrograms/ml for all strains. Eight out of the 55 strains were found to have IC50 values greater than 10(4) micrograms/ml for streptomycin (3). The bacterial effect of combinations of benzylpenicillin and gentamicin or netilmicin was studied in 19 strains of S. faecalis which represented different levels of resistance to streptomycin. Netilmicin was as effective as gentamicin in combination with benzylpenicillin against all strains.

Antibiotic susceptibility of invasive Haemophilus influenzae type b isolates in Denmark in 1988 and 1989.

A system for surveillance of invasive Haemophilus influenzae type b infections in Denmark yielded 135 strains isolated from blood or cerebrospinal fluid from August 1988 through December 1989. The susceptibility of the strains to 7 antibiotics was investigated by an agar dilution method. Ceftriaxone was found to be the most active drug followed by cefotaxime, ceftazidime, rifampicin, ampicillin, cefuroxime, and chloramphenicol. Except for ampicillin the MICs for the individual antibiotics were similar. Seven strains (5.2%), which all produced beta-lactamase, were resistant to ampicillin. Since H. influenzae type b meningitis in otherwise healthy individuals almost exclusively occurs in children aged 2 months to 4 years, a third generation cephalosporin such as ceftriaxone or cefotaxime may be considered the drug of choice for initial therapy of meningitis in this age group.

Antibacterial effect of four phenothiazines.

Various types of phenothiazines were examined for antibacterial effect on 61 Gram-positive and Gram-negative bacterial strains in vitro. The investigated phenothiazines were two neuroleptic drugs, fluphenazine and chlorpromazine, and two antihistaminic drugs, alimemazine and promethazine. All four drugs have antibacterial effects in vitro, the phenothiazines being more potent against the Gram-positive microorganisms. The antibacterial potency of the drugs was measured as IC50: Fluphenazine 29 microM (15 micrograms/ml), alimemzaine 49 microM (37 micrograms/ml), promethazine 88 microM (28 micrograms/ml) and chlorpromazine 92 microM (29 micrograms/ml). The antibacterial potency of the drugs was linked neither to the neuroleptic nor the antihistaminic potency of the drugs, which is in agreement with results of earlier stereoisomeric investigations. Thus, the known phenothiazines may represent a pool of potentially new antimicrobial drugs. A therapeutic application of these results, however, requires additional in vitro an in vivo testing in an animal model. The bacterial model might be of value as a model system in the study of the interaction of neuropharmacological agents and other membrane active compounds on biological membranes.

The antibacterial activity of the psychopharmacological agent clopenthixol and its two main metabolites.

The antibacterial effect of the stereo-isomeric compounds cis(Z)- and trans(E)-clopenthixol and the two main metabolites of clopenthixol in man, N-dealkyl-clopenthixol and clopenthixol sulfoxide, was examined in 24 Gram-positive and 37 Gram-negative bacterial strains in vitro. The antibacterial potency of the drugs towards the Gram-positive strains, measured as IC50, was: N-dealkyl-clopenthixol, 6.2 microM (3.7 micrograms/ml), trans(E)-clopenthixol, 16 microM (7.6 micrograms/ml) and cis(Z)-clopenthixol, 37 microM (17.5 micrograms/ml), and clopenthixol sulfoxide was inactive in the investigated area. Against the Gram-negative strains the drugs are less potent. A therapeutic application of these results, especially in the case of trans(E)-clopenthixol, which possesses no neuroleptic activity, requires in vivo testing in an animal model. However, the in vitro model employed might also be useful in the study of such agents and other membrane-active compounds with regard to their interaction with biological membranes.

Experimental endocarditis in rabbits. 5. Results of long-term penicillin or streptomycin treatment of streptococcus faecalis endocarditis and the effect of long-term exposure of healthy rabbits to the same drugs.

A previously described model of experimental Streptococcus faecalis endocarditis in rabbits without an indwelling catheter during the infectious processes was used to study the effect of long-term treatment with antibiotics. Groups of animals infected with six different strains were treated for four weeks and the following parameters were determined: survival rate, bacterial concentration in blood and vegetations, signs at autopsy indicating congestive heart failure. Before the therapeutic experiments, the tolerance of the rabbit to long-term exposure of the drugs penicillin and streptomycin was considered in a group of non-infected animals. Two out of 20 rabbits died with enteritis during the penicillin exposure, and a general weight reduction was observed. Streptomycin was apparently completely harmless. There was no therapeutic effect of streptomycin on S. faecalis endocarditis due to strains all designated resistant to streptomycin by MIC, except in rabbits infected with a strain, which showed partial susceptibility to the drug by IC50. Regardless of the therapeutic effect, evidence was obtained for rapid development of increased resistance of the infecting strains towards streptomycin. After long-term treatment with penicillin in either low or high dose some of the animals survived and the valves were sterilized in 37% of the animals after low-dose and in 39% after high-dose. It was observed that congestive heart failure occurred with the greatest frequency and intensity after infection with proteolytic strains.

Stereo-isomeric dissociation of the antibacterial and the neuroleptic effect of clopenthixol.

Measurement of the IC50 of cis(Z)-clopenthixol and trans(E)-clopenthixol on 188 bacterial strains from human clinical specimens shows that the antibacterial activity of clopenthixol is exerted by both isomerical components and trans(E)-clopenthixol is the most active antibiotic of the two drugs against the sensitive strains. It is known that the trans(E)-clopenthixol isomere is without neuroleptic effect. The possibility of creating new antibiotics by e.g. steric alteration of neuroleptical agents is stressed. These drugs have different antibiotic patterns from those of classical antibiotics. It seems particularly promising that Pseudomonas aeruginosa is sensitive to these drugs.

The antibiotic effect of the anti-depressive drug femoxetine and its stereo-isomeric analogs on diarrhoea producing enterobacteriaceae.

The present investigation has been undertaken to illustrate the antibacterial effect on 20 diarrhoea producing enterobacteriaceae of an anti-depressive drug available as femoxetine and its three analogs. It has been shown that the stereo-isomeric trans forms of femoxetine are more than twice as active as the cis forms and inhibited all the strains below 400 microgram/ml (1.2 mM). The two cis compounds only inhibited 11 and 9 of the 20 strains respectively in the investigated area 100 microgram/ml - 800 microgram/ml (0.3 mM - 2.4 mM). Our investigations point out that the bacterial cell has a target for psychopharmacologically active agents. Thus the known psychopharmaca and their stereo-isomeric analogs may represent a pool of potentially new antimicrobial drugs. Furthermore the bacterial model may be useful as a model system in the study of the interaction of neuropharmacological agents and other membrane active compounds with biological membranes.

In vitro comparison of gentamicin and netilmicin including a regression line for netilmicin.

The results of two different in vitro investigations are presented: a comparison between gentamicin and netilmicin and a presentation of a regression line for netilmicin. The first investigation comprises 335 bacterial strains. The method used is a plate dilution technique and the susceptibility of the strains is given as IC50 values, i.e. 50% inhibiting concentrations. The conclusion of the study is that netilmicin offers no advantage over gentamicin. In the second investigation a regression line is presented giving the relation between IC50 values for netilmicin and the size of the inhibition zone, based upon 109 bacterial strains. For the disc diffusion method a 20-hour prediffusion technique is used. The disc content is 15 micrograms netilmicin base. The results are discussed and a grouping as to susceptibility is proposed based on the IC50 values found and the blood level obtained after scheduled dose of netilmicin.

Effect of combinations of penicillin and aminoglycosides on Streptococcus faecalis: a comparative study of seven aminoglycoside antibiotics.

The 50% inhibitory concentrations (IC50) of benzylpenicillin, streptomycin, sisomicin, gentamicin, tobramycin, kanamycin, amikacin, and butirosin were determined for 58 clinical isolates of Streptococcus faecalis, 28 of which were recovered from cultures of blood samples from patients with endocarditis. The IC50 of streptomycin was less than 100 microng/ml for 42 strains, 192-10,000 microng/ml for eight, and larger than or equal to 10,000 micron/ml for eight. One isolate that was highly resistant to streptomycin was also highly resistant to kanamycin and butirosin. Extraordinarily high resistance to the other aminoglycosides was not observed. The bactericidal effects of combinations of penicillin and aminoglycosides were studied in 20 strains of S. faecalis that represented different levels of resistance to streptomycin. Significant enhancement of the effect of the combination of penicillin and streptomycin was found only in strains with an IC50 of smaller than or equal to 190 microng/ml. Combinations of penicillin and sisomicin, gentamicin, or tobramycin were effective even against strains that were highly resistant to streptomycin and kanamycin.

The antibacterial effect of some neuroleptics on strains isolated from patients with meningitis.

Eighty-two strains of bacteria (Neisseria meningitidis, Haemophilus influenzae, Enterobacteriaceae, Streptococcus pneumoniae, group B streptococci and Listeria monocytogenes) were examined for their in vitro susceptibility to eight drugs, seven neuroleptics (perphenazine, fluphenazine, cis(Z)-clopenthixol, haloperidol, clozapine, clebopride and SCH 23390), and the neuroleptically inactive trans(E)-clopenthixol. The phenothiazines and the thioxanthenes were, on the whole, the most active drugs when measured, the IC50(50) for each group of bacteria being 7.4 to 84 mg/l (with the exception of the activity against the enterobacteriaceae). The antibacterial potency of clozapine, which has an atypical neuroleptic profile, was between 50 and 140 mg/l. Haloperidol also showed an antibacterial activity in the concentration range 35-140 mg/l. The selective D1 antagonist, SCH 23390 and the selective D2 antagonist, clebopride, inhibited only few of the bacteria in the concentration range investigated.

In-vitro activity and beta-lactamase stability of methicillin, isoxazolyl penicillins and cephalothin against coagulase-negative staphylococci.

Forty-nine clinical strains of coagulase-negative staphylococci were investigated for susceptibility to methicillin, oxacillin, cloxacillin, dicloxacillin, flucloxacillin and cephalothin. The highest level of resistance was found to methicillin and the lowest to cephalothin. The resistance-level of the isoxazolyl penicillins showed a high degree of uniformity. However more strains were resistant to cloxacillin and oxacillin than to dicloxacillin and flucloxacillin. Only a weak correlation was found between beta-lactamase production, and resistance to the six antibiotics. Methicillin was the most stable. The inactivation of cephalothin differed from that of the other antibiotics.