Recognition of beta-lactam antibiotics by rat peptide transporters, PEPT1 and PEPT2, in LLC-PK1 cells

PEPT1 and PEPT2 are H(+)-coupled peptide transporters expressed preferentially in the intestine and kidney, respectively, which mediate uphill transport of oligopeptides and peptide-like drugs such as beta-lactam antibiotics. In the present study, we have compared the recognition of beta-lactam antibiotics by LLC-PK1 cells stably transfected with PEPT1 or PEPT2 cDNA. Cyclacillin (aminopenicillin) and ceftibuten (anionic cephalosporin without an alpha-amino group) showed potent inhibitory effects on the glycylsarcosine uptake in the PEPT1-expressing cells. Other beta-lactams, such as cephalexin, cefadroxil, and cephradine (aminocephalosporins), inhibited modestly the PEPT1-mediated glycylsarcosine uptake. Except for ceftibuten, these beta-lactams showed much more potent inhibitions on the glycylsarcosine uptake via PEPT2 than via PEPT1. Comparison of the inhibition constant (Ki) values between cefadroxil and cephalexin suggested that the hydroxyl group at the NH2-terminal phenyl ring increased affinity for both PEPT1 and PEPT2. It is concluded that PEPT2 has a much higher affinity for beta-lactam antibiotics having an alpha-amino group than PEPT1 and that substituents at the NH2-terminal side chain of these drugs are involved in the recognition by both peptide transporters.

Efflux properties of basolateral peptide transporter in human intestinal cell line Caco-2

Small peptides and some pharmacologically active compounds are absorbed from the small intestine by the apical H(+)-coupled peptide transporter 1 (PEPT1) and the basolateral peptide transporter. Here we investigated the efflux properties of the basolateral peptide transporter in Caco-2 cells using two strategies, efflux measurements and a kinetic analysis of transepithelial transport of glycylsarcosine (Gly-Sar). [(14)C]Gly-Sar efflux through the basolateral membrane was not affected significantly by the external pH. Both approaches revealed that the basolateral peptide transporter was saturable in the efflux direction, and that the affinity was lower than that in the influx direction. For two peptide-like drugs, there was no difference in substrate recognition by the basolateral peptide transporter between the two sides of the membrane. Using the kinetic parameters of PEPT1 and the basolateral peptide transporter, a computational model of Gly-Sar transport in Caco-2 cells was constructed. The simulation fitted the experimental data well. Our findings suggested that substrate affinity of the basolateral peptide transporter is apparently asymmetric, but pH-dependence and substrate specificity are symmetric for the two directions of transport. The behaviour of Gly-Sar in Caco-2 cells could be predicted by a mathematical model describing the peptide transporters.

Susceptibility of anaerobic bacteria to beta-lactam antibiotics and beta-lactamase production

We examined the susceptibility of various anaerobes to four beta-lactamase susceptible (ampicillin, amoxycillin, cyclacillin, and penicillin G) and two beta-lactamase resistant (moxalactam, and N-F-thienamycin) beta-lactam antibiotics and measured beta-lactamase production. Members of the Bacteroides groups were most resistant to the six antibiotics. N-F-thienamycin was the most effective antimicrobial agent against all the test strains, moxalactam the next most effective, and penicillin G the least. Beta-lactamase production was mainly confined to Bacteroides species. Cephalosporinase was the most common beta-lactamase produced; penicillinase was detected less often. About two thirds of the penicillin-resistant isolates produced cephalosporinase. N-F-thienamycin and moxalactam were the most active agents against those anaerobes that were resistant to many beta-lactam antibiotics.

Comparative pharmacokinetics of cyclacillin and amoxicillin in infants and children

Concentrations of cyclacillin in serum over a 6-h period were similar in fasted and milk-fed infants who received 25-mg/kg doses of cyclacillin suspension. Measured by the concentration in serum after oral administration of 15-mg/kg doses, cyclacillin was absorbed more rapidly, reached larger concentrations, and was cleared more promptly than was amoxicillin.

Cyclacillin: microbiological and pharmacological properties and use in chemotherapy of infection - a critical appraisal

The pharmacological and microbiological properties of cyclacillin were discussed and its usefulness in the management of a variety of infections was reviewed. The antibacterial spectrum and clinical utility of this agent generally parallels that of ampicillin, but there are minor differences in specificity with regard to individual microorganisms. The in vitro activity of cyclacillin against gram-negative pathogens varies greatly, the results fluctuating in accordance with the composition of the assay medium of method. The drug has demonstrated excellent therapeutic effectiveness against experimental infections produced by both gram-positive and gram-negative pathogens, thus making questionable a prediction of therapeutic effectiveness from in vitro susceptibility tests alone. Cyclacillin is more resistant to beta-lactamase hydrolysis than ampicillin, is much better absorbed when given by mouth and, as a result, the levels reached in the blood and in the urine are considerably higher than those obtained with the same dose of ampicillin. Cyclacillin produces fewer and milder side-effects than ampicillin.

Effect of cyclacillin and ampicillin on the gut flora of mice

The oral administration of cyclacillin, a semisynthetic aminoalicyclic penicillin, results in the elimination of the lactobacilli from the gastrointestinal tract of mice. Although cyclacillin has a broad spectrum of activity similar to that of ampicillin, it does not, like ampicillin, affect the other flora of the gastrointestinal tract. Cyclacillin, unlike ampicillin, is rapidly absorbed from the stomach and upper small intestine, so that only small amounts reach the large bowel. Study of the dynamics of the lactobacillus population in the gut shows that in the mouse the prime site of localization and multiplication of lactobacilli is the stomach. The lactobacilli are transient in the small and large intestine, arriving there only after having been shed from the stomach.

Comparative studies of the activity of ciclacillin and dicloxacillin

The penicillins ciclacillin and dicloxacillin demonstrate marked similarities in biological activity but, as far as can be determined, differ substantially in respect to the degree of protein binding, which is relatively low for ciclacillin and relatively high for dicloxacillin. In mice infected with Staphylococcus aureus Smith, ciclacillin is considerably more active than dicloxacillin, although both drugs are similarly effective in vitro and similarly absorbed and eliminated in vivo. The high degree of protein binding exhibited by dicloxacillin could therefore very probably explain its relatively low chemotherapeutic activity. Moreover, the in vitro and in vivo findings of the study are inconsistent with the tenets of the tau/2 thesis.

Cyclacillin-induced potentiation of Escherichia coli immunogenicity in vivo and in vitro

The efficacy of cyclacillin as an antimicrobial agent against Escherichia coli was assessed in vivo in mice infected with low numbers of bacteria and compared to the relative effectiveness of the antibiotic against the same organisms in vitro. Treatment of mice with cyclacillin resulted in a rapid clearance of E. coli from the blood and their greater killing in the spleen and liver. Furthermore, a significantly higher antibody plaque response against E. coli developed in cyclacillin-treated mice than in untreated mice or in those given ampicillin. The increased immunogenicity of the E. coli in the antibiotic-treated mice appeared to be due to high levels of cyclacillin in the animals and rapid killing of the bacteria in vivo. In vitro experiments showed that injection of normal mouse peritoneal exudate macrophages which had been incubated with E. coli together with cyclacillin resulted in a greater immunogenicity of the bacteria than when the injection mixture was composed of E. coli which had been incubated alone or only with macrophages. These results suggest that the in vivo effectiveness of an antibiotic such as cyclacillin against a gram-negative organism such as E. coli may be due in part to an effect on the immunogenicity of the bacteria.

Pharmacological and in vitro evaluation of cyclacillin: assessment as potential single-dose therapy for treatment of Neisseria gonorrhoeae infection

The pharmacokinetic properties of cyclacillin administered as a 3.0-g oral dose, with and without progenecid, have been studied and correlated with in vitro activity of the drug against 109 isolates of Neisseria gonorrhoeae. By 8 h after dosage, levels of cyclacillin in serum declined below the minimal inhibitory concentration and the inferior antibacterial activity of cyclacillin (compared with that of amipicillin) suggest that cyclacillin is not a promising alternative to ampicillin for single-dose treatment of gonorrhea.

Cyclacillin: in vitro activity against aerobic and anaerobic bacteria

Cyclacillin at 50 microgram/ml inhibited streptococci (100%), shigella (72%), and Bacteroides (B) fragilis ss fragilis (84%). At 100 microgram/ml it inhibited proteus (75%), B. fragilis (86%), and E. coli (50%). Cyclacillin was more effective than ampicillin against beta-lactamase-producing H. influenzae. The activity of cyclacillin was found to be more enhanced when tested in nutrient agar and Mueller-Hinton agar than in brain heart infusion agar.

[In vitro examination on antibacterial activity of ciclacillin (ACPC) against clinically isolated strains (author's transl)]

(1) The antibacterial acivity of ciclacillin (ACPC) with inoculum size of 10(6) cells/ml was four times less potent than that of ampicillin (ABPC) and 4 approximately 8 times less potent than that of AMPC, but was 4 approximately 8 times more potent than that of CEX against Streptococcus pyogenes. For Streptococcus pneumoniae, ACPC was 2 approximately 4 times less active than ABPC and AMPC, but 16 approximately 32 times more active than CEX. Staphylococcus aureus was 4 approximately 8 times less susceptible to ACPC than to ABPC and AMPC, but 1 approximately 2 times more susceptible than to CEX. Against E. coli, ACPC was as active as CEX, 2 approximately 4 times less active than ABPC, and 4 approximately 8 times less active than AMPC. (2) It was suposed that ACPC was more resistant to penicillinase and more antibacterial with inoculum size of 10(6) cells/ml cells/ml than with 10(6) cells/ml. ACPC was 4 approximately 8 times less active than ABPC, and AMPC against Staphylococcus aureus with 10(8) cells/ml, while with 10(6) cells/ml, it was 2 times less active than ABPC and AMPC. (3) ACPC-resistant strains (greater than or equal to 3.13 microng/ml) of Streptococcus pyogenes and Streptococcus pneumoniae were not found. (4) A difference was noted in MIC of three semi-synthetic penicillins, ACPC, ABPC and AMPC, against Staphylococcus aureus, and E. coli between the sources from which their strains were isolated. (5) There were many strains resistant to erythromycin (EM) and josamycin (JM) (greater than 60%, respectively to both antibiotics) in Stretpococcus pyogenes and pus-isolated Staphylococcus aureus. No strains of Streptococcus pyogenes, were found resistant to EM and JM.

[Distribution and changes of antibiotic susceptibility of genus Haemophilus (author's transl)]

We studied on the distribution and changes of antibiotic susceptibility of H. influenzae, H. parainfluenzae and H. parahaemolyticus isolated from clinical materials, mainly from sputum and pharyngeal swabs. In this study we used 132 strains of H. influenzae, 89 strains of H. parainfluenzae and 43 strains of H. parahaemolyticus isolated during January and June of 1975, and estimated the susceptibility for the following eighteen antibiotics by the agar plate dilution method: ampicillin, amoxicillin, ciclacillin, sulbenicillin, carbenicillin, cephalothin, cefazolin, ceftezole, cephalexin, streptomycin, kanamycin, gentamicin, dibekacin, tetracycline, doxycycline, chloramphenicol, thiamphenicol and colistin. We compared these with previously reported results and observed the changes of antibiotic susceptibility. Ampicillin has the strongest antibiotic activity on three species of Haemophilus and the activity of four cephalosporins was weakest. Among three species H. parahaemolyticus was most susceptible and H. influenzae least susceptible to cephalosporins. Antibiotic activity of cyclacillin was rather weak. Other twelve antibiotics have good activity on Haemophilus. We could not find any ampicillin-resistant strain, but found five (3.8%) streptomycin-resistant, one (0.8%) kanamycin-resistant, eleven (8.3%) tetracycline-resistant, and seven (5.3%) chloramphenicol-resistant strains of H. influenzae. Six years ago we found five (9.6%) streptomycin-resistant and one (1.9%) tetracycline-resistant strains, but no resistant strain to other antibiotics. Tetracycline- and chloramphenicol-resistant strains are supposed to have a tendency to increase. There were very few strains which were resistant to more than two antibiotics among H. influenzae. We found a few strains resistant to tetracycline or chloramphenicol among H. parainfluenzae and H. parahaemolyticus, and one strain of H. parainfluenzae was less susceptible to ampicillin.

[Synthesis and antibacterial activity in vitro of some penicillins containing the phenylcyclohexanie residue]

Some penicillins with structures similar to that of ampicillin and cyclacillin bearing the phenylcyclohexane grouping were prepared. In vitro tests of antibacterial activity showed that the introduction of this residue led to reduced activity in comparison with that of the parent compound.