CombiANT: Antibiotic interaction testing made easy.

Antibiotic combination therapies are important for the efficient treatment of many types of infections, including those caused by antibiotic-resistant pathogens. Combination treatment strategies are typically used under the assumption that synergies are conserved across species and strains, even though recent results show that the combined treatment effect is determined by specific drug-strain interactions that can vary extensively and unpredictably, both between and within bacterial species. To address this problem, we present a new method in which antibiotic synergy is rapidly quantified on a case-by-case basis, allowing for improved combination therapy. The novel CombiANT methodology consists of a 3D-printed agar plate insert that produces defined diffusion landscapes of 3 antibiotics, permitting synergy quantification between all 3 antibiotic pairs with a single test. Automated image analysis yields fractional inhibitory concentration indices (FICis) with high accuracy and precision. A technical validation with 3 major pathogens, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, showed equivalent performance to checkerboard methodology, with the advantage of strongly reduced assay complexity and costs for CombiANT. A synergy screening of 10 antibiotic combinations for 12 E. coli urinary tract infection (UTI) clinical isolates illustrates the need for refined combination treatment strategies. For example, combinations of trimethoprim (TMP) + nitrofurantoin (NIT) and TMP + mecillinam (MEC) showed synergy, but only for certain individual isolates, whereas MEC + NIT combinations showed antagonistic interactions across all tested strains. These data suggest that the CombiANT methodology could allow personalized clinical synergy testing and large-scale screening. We anticipate that CombiANT will greatly facilitate clinical and basic research of antibiotic synergy.

Synergistic and bactericidal activities of mecillinam, amoxicillin and clavulanic acid combinations against extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli in 24-h time-kill experiments.

This study aimed to evaluate the potential synergistic and bactericidal effects of mecillinam in combination with amoxicillin and clavulanic acid against extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli. Eight clinical E. coli isolates with varying susceptibility to mecillinam [minimum inhibitory concentrations (MICs) of 0.125 mg/L to >256 mg/L] and high-level resistance to amoxicillin (MICs > 256 mg/L) were used. Whole-genome sequencing was performed to determine the presence of ß-lactamase genes and mutations in the cysB gene. The activities of single drugs and the combinations of two or three drugs were tested in 24-h time-kill experiments. Population analysis was performed for two strains before and after experiments. Only one strain had a mutation in the cysB gene resulting in an amino acid substitution. With the two-drug combinations, initial killing was observed both with mecillinam and amoxicillin when combined with clavulanic acid. Synergy was observed with mecillinam and clavulanic acid against one strain and with amoxicillin and clavulanic acid against three strains. However, following significant re-growth, a bactericidal effect was found only with amoxicillin and clavulanic acid against two strains. Pre-existing subpopulations with elevated mecillinam MICs were detected before experiments and were selected with mecillinam alone or in two-drug combinations. In contrast, the three-drug combination showed enhanced activity with synergy against six strains, a bactericidal effect against all eight strains, and suppression of resistance during 24-h antibiotic exposure. This combination may be of clinical interest in the treatment of urinary tract infections caused by ESBL-producing E. coli.

A combination of mecillinam and amoxicillin/clavulanate can restore susceptibility of high-level TEM-1-producing Escherichia coli to mecillinam.

Objectives: Mecillinam is recommended in France as a first-line treatment for lower urinary tract infections, due to the large increase in resistance of Escherichia coli to other oral treatments, such as co-trimoxazole or fluoroquinolones, its limited impact on faecal microbiota and its stability in the presence of numerous ß-lactamases. However, we recently identified several mecillinam-resistant E. coli isolates with a high-level expression penicillinase (HEP) phenotype that merit further study. Patients and methods: We studied two isogenic clinical isolates from one patient (one susceptible to mecillinam and one resistant to mecillinam) by WGS to determine the mechanism of mecillinam resistance and compared it with other mecillinam-resistant E. coli . We evaluated the synergistic combination of amoxicillin/clavulanate and mecillinam using a simple test, suitable for daily laboratory practice, to determine the MIC of this combination. Results: We showed that the presence of an SNP in the promoter of the plasmidic TEM-1 ß-lactamase gene is sufficient to confer resistance to mecillinam. This mechanism was present in 67% of HEP-phenotype E. coli tested. Combining mecillinam with amoxicillin/clavulanate abolished resistance, with an MIC compatible with clinical use. This association was not sensitive to the inoculum effect, in contrast to mecillinam alone. Conclusions: An HEP phenotype can confer mecillinam resistance in vitro . This resistance is abolished, regardless of the inoculum, by combining mecillinam with amoxicillin/clavulanate, and can be easily tested in the laboratory. This combination may be used as an oral relay treatment of non-complicated pyelonephritis due to multiresistant E. coli strains.

Mecillinam against genital Chlamydia trachomatis infection: a small-scale proof-of-concept study shows a low cure rate.

OBJECTIVES: Mecillinam is highly active in vitro against Chlamydia spp. We aimed to determine whether mecillinam should be evaluated further as treatment for genital Chlamydia trachomatis infection. PATIENTS AND METHODS: The study was conducted at an open-access clinic for sexually transmitted infections in Oslo, Norway. We planned to include 50 patients. Participants were asymptomatic, heterosexual male patients with a first-void urine sample found to be positive for C. trachomatis by PCR. Treatment consisted of 400 mg of pivmecillinam hydrochloride three times a day for 7 days. A test-of-cure sample, a medication diary and a questionnaire were returned by the participants, and they were used to evaluate treatment outcome, compliance, risk of reinfection and theoretical percentage of time above MIC (t/MIC %). The study was registered in Eudra-CT (no. 2013-002379-179) and clinicaltrals.gov (NCT02083276). RESULTS: The study was discontinued after including 20 patients, due to a high failure rate. Only two of the 17 participants who delivered a test-of-cure sample were cured. Three participants reported condomless sex before the follow-up sample. When the average or most favourable pharmacokinetics (PK)/pharmacodynamics (PD) reported from other studies were applied in a theoretical model, the estimated t/MIC % was above 50% for all of the 15 participants returning a medication diary. Using the least favourable PK/PD, no participant had t/MIC % of >36%. The mean dose interval was 8 h 36 min (standard deviation 3 h 12 min). CONCLUSIONS: A low cure rate combined with uncertainty about intracellular availability and attained t/MIC % makes mecillinam an unattractive candidate for further evaluation as treatment for genital C. trachomatis infection.

Urinary concentrations and urine ex-vivo effect of mecillinam and sulphamethizole.

Healthy adult volunteers received 1 g of sulphamethizole orally (n = 10) and later 400 mg of pivmecillinam (274 mg of mecillinam) (n = 9). All urine was collected in defined periods over 24 h, and the drug concentrations in urine were determined. For sulphamethizole, the maximum urine concentration for seven subjects was reached in 0-3 h, and for the remaining three in 3-6 h. For mecillinam, eight of the nine subjects attained a maximum urine concentration in 0-3 h, after which the concentration declined rapidly for six subjects in 3-6 h. Strains of Escherichia coli with different MICs for sulphamethizole and mecillinam were exposed to collected urine for 2.5 h and 5 h. The results indicated that a sensitive E. coli population should be suppressed by sulphamethizole in urine for two-thirds of the time (with 1 g twice-daily) and by mecillinam in urine throughout the 24-h period (with 400 mg three times a day). There was a slight but significant correlation between the ex-vivo effect (Delta log10 CFU/mL) and the log10 concentration/MIC ratio after exposure to sulphamethizole for 5 h (r2 = 0.27, p < 0.0001), and a significant correlation between the variables with mecillinam (r2 = 0.66, p < 0.0001).

[Antibiotic resistance of E coli isolated from healthy persons]. / Antibiotikaresistens hos E. coli isoleret fra raske normalpersoner.

INTRODUCTION: The aim of the study was to determine the antibiotic susceptibility of E. coli isolates in stools from healthy Danes. METHODS: Sixty-nine persons from Copenhagen participated in the study. Three faecal samples from each participant were examined by culture for each of three periods. E. coli was isolated selectively and tested for sensitivity against sulfamethizole, trimethoprim, the combination of sulfamethizole and trimethoprim, ampicillin, mecillinam, cefuroxime, nitrofurantoin, and ciprofloxacin. RESULTS: Altogether, 184 strains of E. coli were isolated from 66 of the 69 persons. Fifty-eight (31.5%) of the strains isolated from 30 persons (43.5%) were resistant to sulfamethizole, 32 (17.4%) strains isolated from 18 persons (26.1%) were resistant to trimethoprim, 31 (16.8%) strains isolated from 17 persons (24.6%) were resistant to trimethoprim + sulfamethizole, 57 (31%) strains from 31 persons (44.9%) were resistant to ampicillin, 29 (15.8%) of the strains from 24 persons (34.8%) were resistant to nitrofurantoin, two (1.1%) strains from two persons (2.9%) were resistant to cefuroxime, whereas none of the strains was resistant to mecillinam and ciprofloxacin. DISCUSSION: The high prevalence of resistance to sulfamethizole, ampicillin, trimethoprim, and nitrofurantoin is surprising, as none of the persons had been treated with antibiotics, but it may reflect the widespread use of antibiotics in animals for food production. The consequences of the results for empiric antibiotic treatment of, for instance, urinary tract infection are discussed.

Ampicillin plus mecillinam vs. cefotaxime/cefadroxil treatment of patients with severe pneumonia or pyelonephritis: a double-blind multicentre study evaluated by intention-to-treat analysis.

In this double-blind multicentre study, using the intention-to-treat approach, a total of 293 patients with fever (> or = 38.5 degrees C), symptoms of sepsis and signs of pneumonia or pyelonephritis were randomly assigned to treatment with ampicillin and mecillinam (A+M) or cefotaxime followed by cefadroxil. In the febrile phase, treatment was given intravenously twice daily, either with 1,200 mg ampicillin together with 600 mg mecillinam or with 2 g cefotaxime alone. When the patients stayed afebrile, the intravenous administration was replaced by oral treatment twice daily for 14 days, either with 500 mg pivampicillin and 400 mg pivmecillinam or 1 g cefadroxil. In the A+M group, 33% (48/144) of the patients did not complete the full course of treatment as compared with 32% (47/149) in the cephalosporin group, the reasons being treatment failure in 27 and 29, respectively, or adverse effects (n = 16 in both groups). The median duration of fever was 47 h in the A + M group and 50 h in the cephalosporin group. Of 135 patients with pneumonia, 68% were completely cured in the A + M group, and 65% in the cephalosporin group, the main reasons for treatment failure being Mycoplasma pneumonia or ornithosis. Of 136 patients with pyelonephritis, 63% were cured in each group. The main reason for failure was bacteriological relapse. Side-effects were reported by 32 patients (22%) of the A+M group, as compared with 41 (28%) of the cephalosporin group. Epigastric complaints were equally frequent in both groups, but there was a tendency for a higher frequency of exanthema in the A+M group, and for antibiotic-associated diarrhoea and fungal superinfections in the cephalosporin group.

The pharmacokinetics of mecillinam and pivmecillinam in pregnant and non-pregnant women.

1. The pharmacokinetics of parenteral mecillinam (n = 27) and oral pivmecillinam (n = 12) were studied in pregnant (n = 27) and non-pregnant (n = 12) subjects. 2. In early pregnancy (9-14 weeks of gestation) the mean peak plasma drug concentration (Cmax = 19 +/- 9 micrograms ml-1) after an intravenous injection of 200 mg mecillinam was significantly lower (P less than 0.05) and the volume of distribution (V = 49 +/- 20.1) significantly larger (P less than 0.05) than in non-pregnant subjects (Cmax = 35 +/- 18 micrograms ml-1, V = 29 +/- 12.1). In late pregnancy (39-40 weeks of gestation) the plasma mean peak concentration (Cmax = (29 +/- 14 micrograms ml-1) after parenteral administration of 200 mg mecillinam was slightly lower and the volume of distribution (V = 65 +/- 29.1, V = 0.9 +/- 0.4 l kg-1) significantly larger than that in non-pregnant subjects (V = 0.4 +/- 0.3 l kg-1). Also after oral administration of 200 mg pivmecillinam, equimolar to 136.5 mg mecillinam, the mean peak plasma concentration in pregnant subjects (Cmax = 1.8 +/- 1.2 micrograms ml-1) was slightly lower than that in non-pregnant subjects (Cmax = 1.7 +/- 1.2 micrograms ml-1). 3. The mean half-life of elimination after parenteral administration of mecillinam was significantly longer during both early (t1/2,Z = 133 +/- 38 min, P less than 0.05) and late pregnancy (t1/2,Z = 107 +/- 41 min, P less than 0.05) as compared with the non-pregnant state (t1/2,Z = 75 +/- 21 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Ceftazidime combined with mecillinam: serum bactericidal titres compared with in-vitro synergy against gram-negative bacilli.

In a study of the possible interaction between mecillinam and ceftazidime against Gram-negative bacilli, ten volunteers received on separate days: ceftazidime 20 mg/kg iv in 15 min, mecillinam 10 mg/kg iv in 15 min, or the combination. Blood samples were obtained before and 1 and 6 h after the end of the infusion. Ten strains each of Klebsiella pneumoniae, Serratia marcescens, Citrobacter freundii, Salmonella spp. and Yersinia spp. and nine strains each of Acinetobacter spp., and Pseudomonas aeruginosa were selected. Most of the strains were resistant to ampicillin and cefazolin. Serum levels of ceftazidime and mecillinam were measured by bioassay. Serum bacteriostatic (SBS) and bactericidal (SBA) titration was done in microtitre plates in cation supplemented Mueller-Hinton broth and 50% human serum. Chequerboard titration was also studied to assess in-vitro synergy between ceftazidime and mecillinam in Mueller-Hinton broth with or without 50% serum. The mean serum concentrations (SD) were for mecillinam: 6.1 (1.7) at 1 h, and less than 0.3 at 6 h and for ceftazidime: 36.3 (5.5) at 1 h and less than 5 at 6 h. Identical concentrations were measured for the combination. By chequerboard titration, no synergy occurred for Acinetobacter spp. and Ps. aeruginosa, whereas it was observed in 37/60 (FIC) and 33/60 (FBC) of the strains of other species in Mueller-Hinton; from the strains showing synergy, 28/37 (FIC) and 30/33 (FBC) showed also synergy in Mueller-Hinton with 50% human serum. In SBS and SBA, on the other hand, the combination of mecillinam with ceftazidime showed an additive effect against most Enterobacteriaceae tested, synergy being shown for only 10-35% of tests.(ABSTRACT TRUNCATED AT 250 WORDS)

One or three weeks' treatment of acute pyelonephritis? A double-blind comparison, using a fixed combination of pivampicillin plus pivmecillinam.

The clinical and bacteriological effects of 1 and 3 weeks' pivampicillin plus pivmecillinam treatment were compared in a double-blind, randomized study of patients with acute pyelonephritis. Three weeks after the end of active treatment, clinical success was seen in 29 (91%) of the 32 patients on 1-week treatment, compared with 28 (97%) of the 29 patients treated for 3 weeks. Bacteriological success was seen in only nine (28%) patients in the 1-week group vs. 20 (69%) in the 3-week group (p = 0.004). This difference was mainly due to a large number of relapses of lower urinary tract infection in the 1-week group. Even in uncomplicated cases, the bacteriological result of the 1-week treatment was unsatisfactory. Side-effects were more common in the 3-week treatment group. In conclusion, 1-week treatment of patients with acute pyelonephritis is too short. Three weeks' treatment is effective in uncomplicated cases, but even longer treatment or low-dose prophylaxis is indicated in certain patients with predisposing factors.

[Studies on the drug permeability of vesical walls. The permeability of mecillinam from the bladder].

When a drug is instilled into the bladder provided with experimental cystitis, the drug could be transferred into the serum. We studied the transfer of mecillinam into the serum, and found that the extent of transfer varied with the method to cause experimental cystitis and also occurred even in the normal bladder. It was suspected that in the inflamed bladder, a part of mecillinam excreted into the urine would possibly be transferred again into the serum through bladder wall.

Pharmacokinetics of mecillinam after a single intravenous dose in patients with impaired renal function.

Twelve male patients with impaired renal function and six healthy male volunteers were given a single i.v. dose of mecillinam (400 mg). Serum concentrations of mecillinam were determined by a microbiological assay. The pharmacokinetic parameters were obtained using an open, two-compartment model. Results showed that the median elimination t 1/2 (beta) of mecillinam was longer in patients (5 h) than in volunteers (3.4 h) (p less than 0.1). The median AUC0----infinity was greater in patients (72.44 micrograms ml-1.) than in volunteers (32.96 micrograms ml-1 X h) (p less than 0.001). Moreover, the median clearance was decreased in patients (5.5 L h-1) as compared with volunteers (12.17 L h-1) (p less than 0.001). Thus the study showed prolonged half-life and decreased elimination of mecillinam in patients with impaired renal function.

Pharmacokinetics of intravenous amdinocillin in healthy subjects and patients with renal insufficiency.

Five healthy volunteers and 31 patients with various degrees of renal impairment received a 10-mg/kg intravenous dose of amdinocillin by infusion over 15 min to establish the disposition profile of the drug in plasma and urine. Both clearance from plasma and elimination rate constant showed a linear relationship with creatinine clearance. It was noted that in subjects with creatinine clearances of greater than 50 ml/min, the elimination half-life remained relatively constant; however, as the creatinine clearance decreased from 50 to 5 ml/min, there was a progressive rise in the elimination half-life. Despite the removal of the drug by hemodialysis (32 to 72% of the dose), concentrations of amdinocillin in plasma remained in the therapeutic range. In patients undergoing peritoneal dialysis, less than 4.0% of the infused dose was removed by dialysis during the hourly exchanges over a 14- to 18-h period. Although the clearance from plasma and the half-life of amdinocillin were altered up to fourfold in patients with creatinine clearances of less than 15 ml/min, the amdinocillin dosage per se may not need to be reduced for these patients if the frequency of dosing is reduced from six to three or four times daily. This is based on drug accumulation estimates of 56% from a regimen of 10 mg/kg every 8 h in these patients as compared with less than 10% from a regimen of 10 mg/kg every 4 h in subjects with normal renal function. In addition, supplemental doses may not be necessary during or at the end of hemodialysis for patients undergoing hemodialysis.

[Absorption, distribution, metabolism and excretion of bacmecillinam. I. Absorption, distribution, metabolism and excretion of 14C-bacmecillinam following oral administration to rats].

The pharmacokinetics of bacmecillinam (KW-1100), a new semisynthetic penicillin, was studied. Plasma levels, tissue distribution, metabolites and urinary and biliary excretion of mecillinam after oral administration of KW-1100 were studied in rats given a dose of 20 mg/kg (as mecillinam). The absorption of 14C-KW-1100 was so rapid that the level in blood was found to reach the peak 30 minutes after administration. 14C-KW-1100 was distributed widely into various tissues and relatively high distribution was noted in liver, kidney, adrenal gland and spleen. No accumulation of 14C-KW-1100 in any tissue was found. It was excreted rapidly from each tissue. Within 24 hours after administration of KW-1100, approximately 86% of the given dose was excreted. And within 72 hours, approximately 97% of the dose was excreted. Excretions in urine and feces within 72 hours after KW-1100 administration were 39.5 and 57.4% of the given dose, respectively. Biliary excretion was 2.0% of the given dose within 24 hours after administration of KW-1100. The major metabolite in the plasma at peak time (30 minutes) was mecillinam (50.5%). The major metabolite in the urine (0 approximately 8 hours) was mecillinam (52.2%), too. The minor metabolites were 5,5-dimethyl-2-(1'-formamidomethyl)-thiazolidine-1',4-dicarboxylat e(M-1), 6-beta-[(hexahydro-1H-azepin-1-yl)-methyleneamino]-penicilloic acid (M-6) and M-4.

[Absorption, distribution, metabolism and excretion of bacmecillinam. III. Absorption, metabolism and excretion of 14C-bacmecillinam following oral administration to dogs].

The pharmacokinetics (i.e., blood level, biological half-lives and excretion) of bacmecillinam (KW-1100) was investigated. KW-1100 was orally administered to dogs at the dose of 20 mg/kg (as mecillinam). Biological half-lives (radioactivity) of 14C-KW-1100 in plasma were 1.2 hours (T1/2 alpha) and 52 hours (T1/2 beta). The Cmax and Tmax were 8.4 micrograms/ml and 2 hours. The biological half-life (microbiological activity) of KW-1100 in plasma was 0.9 hour. The Cmax and Tmax were 5.6 micrograms/ml and 1 hour. The urinary and fecal excretion of 14C-KW-1100 were approximately 46% and 49% (0 approximately 72 hours), respectively. The major metabolites in the urine (0 approximately 8 hours) were mecillinam, 5,5-dimethyl-2-(1'-formamidomethyl)-thiazolidine-1',4-dicarboxy lat e (M-1) and 6-beta-[(hexahydro-1 H-azepin-1-yl)-methyleneamino]penicilloic acid (M-6), each distribution ratio of which was 57.2, 24.2 and 12.0% of the total radioactivity in the sample, respectively. The major metabolite in the plasma at peak time (2 hours) was mecillinam (56.2%).

[Absorption, distribution, metabolism and excretion of bacmecillinam. IV. Metabolites of bacmecillinam in human urine].

Bacmecillinam (KW-1100) metabolites and their excretion in human urine were investigated in the 3 male volunteers. After administration of KW-1100 capsules containing 80 mg (2 X 40 mg) as mecillinam to men, the urine samples up to 8 hours were collected for every 2 hours and analysed by high performance liquid chromatography and gas chromatography. The major metabolites in the human urine were mecillinam and 6-beta-[(hexahydro-1H-azepin-1-yl)-methyleneamino]-penicilloic acid (M-6), and minor quantities of M-4 and M-1 were also detected as the metabolites. Total recoveries of administered dose for the 3 volunteers were approximately 62, 81 and 73%, respectively. And M-1 excretion rate was lower than that in the case of rats and dogs. Hexamethyleneimine (HMI) as metabolite from the side chain was detected.