Dr operon-associated invasiveness of Escherichia coli from pregnant patients with pyelonephritis.

We used a gentamicin protection assay to assess the ability of gestational pyelonephritis isolates of Escherichia coli to invade HeLa cells. The ability to enter HeLa cells was strongly associated with the presence of Dr operons coding for Dr adhesins. In contrast, the nonivasive isolates predominantly expressed papG, coding for P fimbriae.

Rapid receptor-clustering assay to detect uropathogenic and diarrheal Escherichia coli isolates bearing adhesins of the Dr family.

Infections caused by Escherichia coli isolates expressing adhesins of the Dr family are associated with diarrhea and urinary tract infections, and these E. coli strains recognize the complement regulatory protein decay-accelerating factor (DAF) as their receptor. Clustering of the DAF receptor at the sites of bacterial adherence to epithelial cells is proposed as an alternative to PCR assay for rapid detection of Dr-positive E. coli.

Ampicillin-resistant Escherichia coli in gestational pyelonephritis: increased occurrence and association with the colonization factor Dr adhesin.

The pattern of ampicillin resistance and possible association with virulence factors of 78 Escherichia coli isolates taken from 78 pregnant women with pyelonephritis were evaluated. The current incidence of ampicillin resistance among pyelonephritis isolates (46%) was significantly higher than that reported in 1985 (22%). Resistance was found more frequently during the first (60%) and third (53%) trimesters than during the second trimester (33%). Of all dra(+) E. coli isolates, 75% were ampicillin resistant, whereas dra(+) isolates of O75 serotype E. coli accounted for 87% of ampicillin-resistant strains. The significant increase of ampicillin resistance among gestational pyelonephritis E. coli and the association with the dra gene cluster encoding colonization and invasive capacity may warrant further study involving obstetric and neonate wards, with the latter being at the higher risk for potential problems.

Kinetics of drug decomposition. Part 73. Kinetics and mechanism of vitamin K3 soluble form thermal decomposition in solid phase.

Kinetics of thermal decomposition of trihydrate of sodium salt of 1,2,3,4-tetrahydro-2-methyl-1,4-dioxo-2-naphthalenesulfonic acid (MDS, vitamin K3 soluble form) in solid state by accelerated aging method at elevated temperature has been studied. It was found that the process occurs according to Prout-Tompkins model and its rate depends on temperature, humidity and particle size of the substance. Thermodynamic parameters of the reaction (Q10(0), EA, delta H not equal to, delta S not equal to, delta G) were determined and theoretically predicted stability of MDS at room temperature is given. The reaction mechanism assumes a preliminary dehydration occurring via the successive elimination of one and a half, two and a half and finally three molecules of water. The obtained anhydrous form decomposes thermally forming free radical intermediates and yielding finally 2-methyl-1,4-naphthoquinone (vitamin K3), SO2 and NaOH.

Kinetics of drug decomposition. Part 74. Kinetics of degradation of minocycline in aqueous solution.

Under anaerobic conditions within the pH range 0.38-9.35 (at 343 K) and in the presence of air oxygen within the pH range 0.83-5.42 (at 323 K) the degradation of minocycline (MC) in aqueous solutions follows the first order kinetics. In neutral and alkaline solutions in the presence of air oxygen the autocatalytic first order reaction takes place. The degradation of MC both under anaerobic and aerobic conditions is catalyzed by buffer components of formate, acetate, phosphate and borate buffers. Under anaerobic conditions the degradation of MC is a result of water evoked spontaneous reaction. The rate of this reaction depends on the charge of MC. The specific rate constants of degradation for particular ionic species of MC under anaerobic conditions have been determined. The rate of oxidation of MC is also charge-dependent. The most susceptible to oxidation are the ionic species MC+-, MC+-- and MC--. Effects of temperature, metal ions and stabilizers on the stability of MC were also investigated.

Kinetics of drug decomposition. Part 66. Kinetics of the hydrolysis of carphecillin in aqueous solution.

The rates of hydrolysis of the beta-lactam ring in the pH range 1.77--9.22 at 294, 303, 313 and 233 K and of the ester bond in the pH range 0.43--8.78 at 273, 283, 294, 303, 313 and 323 K for carphecillin have been investigated. The rate constants were determined for the reactions catalyzed by H+ and OH- ions and moreover for the hydrolysis of the beta-lactam ring catalyzed by undissociated acids and anionic bases. The thermodynamic parameters were calculated for particular reactions. In the acidic medium carphecillin is significantly more stable than carbenicillin. In the alkaline medium the rate of inactivation of carphecillin and carbenicillin is the same because carbenicillin is formed from carphecillin as the result of the very fast hydrolysis of the ester bond.

Kinetics of drug decomposition. Part 69: Effect of excipients on the thermal decomposition of the mixture of aminophenazone allobarbital and adiphenine hydrochloride in the solid.

By the method of accelerated testing at elevated temperature, the thermal decomposition rate of the mixture of aminophenazone (AP), allobarbital (AB) and adiphenine hydrochloride (AD) and its individual components in the presence of the excipients starch (potato), agar, talcum, kaolin and magnesium stearate is studied. The individual and joint effect of the excipients on the components of the mixture AP + AB + AD as well as on the mixture as a whole is determined and compared. The theoretically predicted stability of the components is discussed and compared with the results of "self-life" tests in the presence and absence of the excipients.

Kinetics of drug decomposition. Part 67. Kinetics of degradation of dicloxacillin in aqueous solution.

The rates of hydrolysis of beta-lactam ring of dicloxacillin (DC) in the pH range 1.10-9.65 at 293, 303 and 313 K were determined. Specific rate constants were calculated for: H degree ions, undissociated phosphoric acid and H2PO4- ions catalysis of hydrolysis of undissociated DC molecule; for H+, OH-, HPO4(-2) and CH3COO- ions and undissociated phosphoric and acetic acids catalysis of hydrolysis of dissociated DC species and spontaneous hydrolysis of dissociated DC species. For each process the thermodynamic parameters were determined.

Kinetics of drug decomposition. Part 60. Thermal decomposition of the mixture of aminophenazone, allobarbital and adiphenine hydrochloride in the solid state.

Kinetics of decomposition of a mixture of aminophenazone, allobarbital and adiphenine hydrochloride has been examined using accelerated testing at elevated temperatures (333-353 K). The reaction order, rate constants and activation parameters (Q10 degrees, EA, delta H#, delta S#, delta G) have been determined and compared for each component, in the presence of each component of the mixture and in the presence of two components of the mixture. The effect of individual components of the mixture on the rate of decomposition of the other components has been observed, the value of this effect has been determined using the rate constants obtained. The rate constants and times t10% for room temperature were calculated. The "shelf-life time" (t10%) was calculated from accelerated testing data at elevated temperature and compared with that obtained for Vegantalgin ragées in the mixture studied at 293 K.

Kinetics of drug decomposition. Part 61. Kinetics of various ampicillin forms degradation in solid phase.

Ampicillin sodium salt degradation in solid state relies on a sequential reaction consisting of three pseudo first-order processes. The above salt is much more susceptible to degradation than acidic forms of ampicillin. The anhydrous acidic form of ampicillin is very stable in solid phase. Therefore, it can be recomended to be formulated in peroral ampicillin pharmaceutical preparations. Ampicillin trihydrate, now used in pharmaceutical formulations, is less stable than the last mentioned compound. It degrades according to Prout-Tompkins' model.

Kinetics of drug decomposition. Part 62. Kinetics of penicillin G potassium salt (PGP) thermal degradation in solid phase.

The kinetics of degradation of penicillin G K salt (PGP) in solid phase in the temperature range 70-140 degrees C were investigated. The obtained sigmoidal curves were interpreted in terms of the Prout-Tompkins kinetics. The appropriate mathematical equations were derived for the induction and acceleration periods which enable to calculate the degradation half-time, t0.1 value and the induction time (t'). The Arrhenius plot shows the isokinetic point where the rates of reaction for both periods are identical.

Chemical characterization of decomposition products of drugs. Part 6. Mass spectrometry of some perazine derivatives.

Mass spectra of perazine, prochlorperazine, tiethylperazine, trifluperazine, butaperazine and thioproperazine were obtained. All possible fragmentation routes were discussed. The mechanism of fragmentations, their similarities and differences within the investigated group of compounds were established. The Hammett type relationship was found between the intensities of some ions and the kind of substituents at the C2 position. The utility of mass spectra for the prediction of drug stability was demonstrated.

Kinetics of drug degradation. Part 58: a method of preparation and the stability of 3% aqueous indometacin solution.

A method was worked out which allows one to obtain 3% aqueous indometacin solution. The above can be done by solubilization of indometacin by means of ethyl carbamate and ethylurea in the concentration of 30% each and boiling the mixture for 30 s. The stability of indometacin in the above solution was checked with respect to elevated temperatures and exaggerated UV light conditions and compared with the stability of the same solution but without the solubilizing agents. It appears that the solubilizing agents diminish both the hydrolytic as well as the photochemical degradation processes of indometacin. 3% aqueous indometacin solution is stable for 25 months at 20 degrees C, and it is practically non-susceptible to the effects of diffused light for many years. The indometacin solution proposed shows low acidity (pH = 6.95). It is believed that the above solution can be introduced to everyday medical treatment.