MexXY RND pump of Pseudomonas aeruginosa PA7 effluxes bi-anionic ß-lactams carbenicillin and sulbenicillin when it partners with the outer membrane factor OprA but not with OprM.

Antibiotic resistance in Pseudomonas aeruginosa is a serious concern in healthcare systems. Among the determinants of antibiotic resistance in P. aeruginosa, efflux pumps belonging to the resistance-nodulation-division (RND) family confer resistance to a broad range of antibacterial compounds. The MexXY efflux system is widely overexpressed in P. aeruginosa isolates from cystic fibrosis (CF) patients. MexXY can form functional complexes with two different outer membrane factors (OMFs), OprA and OprM. In this study, using state-of-the-art genetic tools, the substrate specificities of MexXY-OprA and MexXY-OprM complexes were determined. Our results show, for the first time, that the substrate profile of the MexXY system from P. aeruginosa PA7 can vary depending on which OM factor (OprM or OprA) it complexes with. While both MexXY-OprA and MexXY-OprM complexes are capable of effluxing aminoglycosides, the bi-anionic ß-lactam molecules carbenicillin and sulbenicillin were found to only be the substrate of MexXY-OprA. Our study therefore shows that by partnering with different OMF proteins MexY can expand its substrate profile.

Modified Penicillin Molecule with Carbapenem-Like Stereochemistry Specifically Inhibits Class C ß-Lactamases.

Bacterial ß-lactamases readily inactivate most penicillins and cephalosporins by hydrolyzing and "opening" their signature ß-lactam ring. In contrast, carbapenems resist hydrolysis by many serine-based class A, C, and D ß-lactamases due to their unique stereochemical features. To improve the resistance profile of penicillins, we synthesized a modified penicillin molecule, MPC-1, by "grafting" carbapenem-like stereochemistry onto the penicillin core. Chemical modifications include the trans conformation of hydrogen atoms at C-5 and C-6 instead of cis, and a 6-α hydroxyethyl moiety to replace the original 6-ß aminoacyl group. MPC-1 selectively inhibits class C ß-lactamases, such as P99, by forming a nonhydrolyzable acyl adduct, and its inhibitory potency is ∼2 to 5 times higher than that for clinically used ß-lactamase inhibitors clavulanate and sulbactam. The crystal structure of MPC-1 forming the acyl adduct with P99 reveals a novel binding mode for MPC-1 that resembles carbapenem bound in the active site of class A ß-lactamases. Furthermore, in this novel binding mode, the carboxyl group of MPC-1 blocks the deacylation reaction by occluding the critical catalytic water molecule and renders the acyl adduct nonhydrolyzable. Our results suggest that by incorporating carbapenem-like stereochemistry, the current collection of over 100 penicillins and cephalosporins can be modified into candidate compounds for development of novel ß-lactamase inhibitors.

Nontoxic concentration of antibiotics for intravitreal use--evaluated by human in-vitro ERG.

The effects of penicillin G (PC-G) sodium, procaine PC-G, cloxacillin sodium (MCIPC), disodium sulbenicillin (SBPC), cefazolin sodium (CEZ), gentamicin sulfate (GM) and fosfomycin sodium (FOM) on the electroretinogram (ERG) of the human in-vitro eye-cup were studied. The oscillatory potentials (OPs) were selectively and greatly suppressed by 1.0 mM PC-G sodium. The OPs and c-wave were suppressed by 0.85 mM procaine PC-G. The b-wave and OPs were slightly suppressed by 1.0 mM MCIPC. The a-wave, b-wave, OPs and c-wave were not deteriorated by 1.0 mM SBPC. The OPs appeared to be selectively suppressed by 1.0 mM CEZ. The b-wave was suppressed and the peak latencies of the OPs were delayed by 184 micrograms/ml (approximately 0.4 mM) GM. The amplitudes of the a-wave and c-wave were slightly enhanced and their peak latencies were slightly delayed by 184 micrograms/ml GM. The a-wave, b-wave, OPs and c-wave were not deteriorated by 1.0 mM FOM. The results of the present study on the human retina were comparable to those on the albino rabbit retina in our previous studies.

Electron microscopy of Pseudomonas aeruginosa treated with sulbenicillin and dibekacin.

A possible mechanism responsible for the combined effects of sulbenicillin and dibekacin on Pseudomonas aeruginosa IAM 1007 was investigated. The bactericidal activity of the above two drugs in combination was very strong. The regrowth of test strains after removal of the drugs was suppressed markedly, even when they were exposed to sulbenicillin plus dibekacin at a subinhibitory concentration of individual drugs. Sulbenicillin caused elongation of the bacterial cells. At the early stage of elongation, no demonstrable changes of ultrastructure of the cell wall were observed. At the late stage, lysis of the peptidoglycan layer occurred and spheroplast was formed. However, most of the outer membrane of the cell wall remained intact. Sulbenicillin acts upon the peptidoglycan layer, but not on the outer membrane. Thus it is difficult for sulbenicillin alone to cause cell lysis. On the other hand, dibekacin caused destruction of ribosomes and lysis of the outer membrane of the cell wall. Both sulbenicillin and dibekacin act on the cell wall, the former on the peptidoglycan layer (the inner membrane) and the latter on the outer membrane. The combined use of sulbenicillin and dibekacin caused elongation of bacilli and severe destruction of the inner and outer membranes of the cell wall. These morphological changes occurred even when the concentration of the individual drug was lower than its minimum inhibitory concentration (MIC). Furthermore, the cells elongated by sulbenicillin were ruptured easily when treated with dibekacin subsequently. The bacilli treated with dibekacin at a concentration lower than MIC and then treated with sulbenicillin at a concentration lower than MIC showed a marked elongation of the cells, which indicated that the effects of sulbenicillin was enhanced by dibekacin. These findings suggested strongly that sulbenicillin and dibekacin act on cell wall constituents and that their effects were complementary and synergistic.

Evaluation of the minimal bactericidal time (MBT) of sulbenicillin against multiresistant pathogens.

The in vitro antibacterial activity of sulbenicillin was evaluated against multiresistant strains isolated from in-patients and compared with that of carbenicillin and piperacillin. Sulbenicillin resulted in being as active as the other drugs against the strains tested, both at different pH, and at different bacterial inocula. In the time-kill tests sulbenicillin demonstrated bactericidal activity similar to that of piperacillin, and a higher killing rate when compared with that of carbenicillin.

Studies on 6 alpha-substituted penicillins. II. Synthesis and structure-activity relationships of 6 beta-(2-aryl-2-sulfoacetamido)-6 alpha-methoxy penicillanic acids.

The synthesis and antibacterial activity of 6 alpha-methoxysulbenicillin analogues (2) are described. Structure-activity studies of these derivatives bearing hydrophilic substituents in the phenyl ring led to the identification of disodium 6 beta-[D-2-(3,4-dihydroxyphenyl)-2-sulfoacetamido]-6 alpha-methoxypenicillanate (2m) as a compound with potent activity against Pseudomonas aeruginosa including beta-lactamase producing strains. Additional substitution of 2m gave derivatives 2p, 2q, 2r, with a further improvement in activity against Gram-negative bacteria.

[Bactericidal and potent antiadhesive activity of sulbenicillin]. / Studio dell'attivita battericida di sulbenicillina e del suo potere antiaderente.

Sulbenicillin, a wide broad spectrum penicillin, is active against a lot of gram positive and gram negative bacteria. The AA. studied the activity of this molecule against urinary infections causing germs, by evaluating two parameters: his antiadhesive capability and the Killing curves, in comparison with mezlocillin and piperacillin. An inhibition in adhesive capability of test-germs, due to sulbenicillin was obtained. Furthermore, resulting Killing curves showed more rapidity in action for sulbenicillin than for the two others molecules, versus resistant germs, like P. aeruginosa and S. faecalis.

Aminoglycoside antibiotics and lysosomal enzymes of human tears.

We examined biochemically the effect of six aminoglycoside antibiotics on the activity of lysozyme, acid phosphatase, and N-acetyl-beta-D-glucosaminidase in human tears. All six antibiotics strongly inhibited lysozyme activity, the degree of inhibition depending on the dose administered. Except for bekanamycin, antibiotics had little effect on the activity of acid phosphatase or N-acetyl-beta-D-glucosaminidase. The nature of the inhibition was competitive. Other kinds of antibiotics, such as sulbenicillin or erythromycin, had no inhibitory effect on lysozyme, acid phosphatase, or N-acetyl-beta-D-glucosaminidase. These results suggested that the inhibition of lysozyme by aminoglycosides is specific and that the decreased effectiveness of a protective system against bacterial infection in the eye is highly possible when aminoglycoside antibiotics are used without prior sensitivity testing.

[Comparative clinical study of aspoxicillin and sulbenicillin in postoperative wound infections].

A well-controlled comparative study was performed to evaluate efficacy, safety and utility of aspoxicillin (ASPC) as compared with sulbenicillin (SBPC) in the treatment of postoperative wound infections. Either 2 g of ASPC or 2 g of SBPC was administered to patients by intravenous drip infusion twice a day for 7 days. The following results were obtained: Overall clinical effectiveness rates were 82.5% (66/80) in ASPC group and 77.0% (57/74) in SBPC group, with no statistically significant difference between 2 groups. Final overall clinical improvement rates were 83.8% (67/80) in ASPC group and 81.1% (60/74) in SBPC group, with no statistically significant difference between 2 groups. As to bacteriological effectiveness, eradication rates of clinical isolates were 70.4% (38/54) in ASPC group and 74.4% (32/43) in SBPC group. There was no statistically significant difference in 2 groups. Side effects and abnormal laboratory findings were observed in 6 cases (6.7%) and 11 cases (12.4%) in ASPC group (89 cases) respectively, and 4 cases (4.4%) and 7 cases (7.8%) in SBPC group (90 cases) respectively. Especially severe adverse reactions were not observed, and there was no significant difference in the incidences of side effects and abnormal laboratory findings between 2 groups. As to overall clinical utility, utility rates were 77.5% (62/80) in ASPC group and 70.3% (52/74) in SBPC group. There was no statistically significant difference between 2 groups. These results may be indicated that ASPC is as useful as SBPC in the treatment of postoperative wound infections.

Antibacterial activity in vitro of sulbenicillin against mucoid and non-mucoid strains of Pseudomonas aeruginosa.

The in vitro antibacterial activity of sulbenicillin against a number of mucoid and non-mucoid strains of Pseudomonas aeruginosa was investigated and compared with that of some other beta-lactam antibiotics. From the data reported it is evident that sulbenicillin showed better anti-microbial activity than carbenicillin in almost all the tests run. Sulbenicillin appears to have a somewhat lower activity than piperacillin and cefotaxime; however, cefotaxime and particularly piperacillin are highly conditioned by the inoculum size and have a less favourable MBC to MIC ratio.

Sulbenicillin-induced kaliuresis in man.

The mechanism of kaliuresis induced by massive antibiotic administration was studied using alpha-sulfobenzyl penicillin (SBPC). In experimental group (n = 8), urinary electrolytes excretion were compared between following the infusion of 10 g SBPC in 200 ml water at a constant rate and following the infusion of 48 mmol of NaCl (equal to that contained in 10 g SBPC) in 200 ml water. For the control group, 96 mmol NaCl in 400 ml water was infused (n = 5). In the experimental group, urinary Na (UNaV) and urinary K excretion (UKV) increased relative to the control period. In the control group, UKV was not increased although UNaV was increased (p less than 0.05). UKV following SBPC infusion was correlated with UNaV (p less than 0.05) and urinary SBPC excretion (p less than 0.05). The ratio of urinary anion gap to urinary cation [1-(urinary Cl concentration/(urinary Na concentration + urinary K concentration))] was significantly increased following SBPC infusion (p less than 0.005) but not in the control group. This increase in anion gap is possibly due to urinary SBPC, which will be ionized over 90% as nonreabsorbable anion in maximally acidic urine. We conclude that the kaliuresis induced by massive SBPC administration in man is probably caused by the nonreabsorbable anion effect of SBPC itself.

A turbidimetric study of the responses of selected strains of Pseudomonas aeruginosa to eight antipseudomonal beta-lactam antibiotics.

Turbidimetric and morphologic responses to eight antipseudomonal beta-lactam antibiotics were compared for selected strains of Pseudomonas aeruginosa with different susceptibilities to carbenicillin. In conventional minimal inhibitory concentration tests, all of the newer antibiotics appeared more active than carbenicillin, and apalcillin and cefsulodin had the greatest overall activity. However, in turbidimetric tests the activity of apalcillin and three other N-acyl penicillins (azlocillin, mezlocillin, and piperacillin) was inferior to that of carbenicillin and the other agents. The N-acyl penicillins were also all susceptible to intrinsic pseudomonal beta-lactamase, so that dense bacterial populations inactivated these antibiotics in concentrations of greater 128 micrograms/ml during overnight incubation. Against carbenicillin-resistant strains, carbenicillin, ticarcillin, and sulbenicillin were the least active antibiotics, and cefsulodin had the best overall activity. Turbidimetric monitoring highlights the problems of interpreting the results of conventional minimal inhibitory concentration tests, particularly when large inocula are involved.

Factors affecting the quality of boar semen stored by means of dialysis.

The effects of dialysis fluids containing blood serum, serum albumin or activated charcoal on the storage of boar serum were examined. The effects of antibiotics were also tested by including them in the dialysis fluids and semen samples. Undiluted semen was stored for 7 days at 15 degrees C by means of dialysis across a cellulose membrane. A combination of sulbenicillin and streptomycin was superior to that of penicillin and streptomycin in reducing bacteria and maintaining sperm motility and normal acrosomes. Serum albumin exerted a beneficial effect on the stored spermatozoa which may be due to its capacity to adsorb the metabolic products from bacteria and spermatozoa; it could be replaced with activated charcoal.

[Comparison of the antibacterial activity of ticarcillin with other antibacterial agents (author's transl)].

Antibacterial activity of ticarcillin was determined in comparison with that of sulbenicillin, amoxicillin, cefuroxime, clindamycin and metronidazole against anaerobic bacteria which have been isolated from various clinical materials in this hospital. Growth of more than 90% of Gram-negative anaerobic rod bacteria was inhibited by ticarcillin at its concentration of 100 micrograms/ml. Strains resistant to ticarcillin showed cross resistance against both sulbenicillin and amoxicillin. Antibacterial activity of ticarcillin against Gram-positive anaerobic bacteria was found almost equal to sulbenicillin but slightly inferior to amoxicillin. Cefuroxime was found most inferior among the tested six antibiotics when an inoculation level of 10(8)/ml was utilized, but it showed similar activity to ticarcillin when they were tested with 10(6)/ml inoculation. Approximately 10% of bacteroides strains was resistant to clindamycin while all the strains were sensitive to metronidazole.