Acinetobacter baumannii detected on modified charcoal-cefoperazone-deoxycholate agar in a waste stabilization pond.

Campylobacter is a recommended reference pathogen for the verification and validation of water recycling schemes in Australia and globally. In a larger study investigating the efficacy of pathogen removal in waste stabilization ponds (WSP), we cultivated bacteria from wastewater samples on modified charcoal-cefoperazone-deoxycholate agar (mCCDA) targeting the growth of Campylobacter. A high number of colonies characteristic of Campylobacter grew on this selective medium, but this did not correlate with qPCR data. Using primers targeting the 16S rRNA gene, and additional confirmatory tests to detect VS1, ompA, blaOXA-51-like, blaOXA-23-like genes, we tested 80 random colonies from 10 WSP samples. All 80 were identified as Acinetobacter baumannii. Wastewater grab samples taken three times over 6 months throughout the WSP system showed removal of A. baumannii in the WSP at rates similar to that of Escherichia coli. Our study suggests that mCCDA agar is not a suitable medium for isolating Campylobacter from environmental samples and that A. baumannii can be used as an indicator for removal of pathogens in WSPs.

In-depth analysis of the treatment effect and synergistic mechanism of TanReQing injection on clinical multi-drug resistant Pseudomonas aeruginosa.

Antibiotic resistance is a recognized and concerning public health issue. Gram-negative bacilli, such as Pseudomonas aeruginosa (P. aeruginosa), are notorious for their rapid development of drug resistance, leading to treatment failures. TanReQing injection (TRQ) was chosen to explore its pharmacological mechanisms against clinical multidrug-resistant P. aeruginosa (MDR-PA), given its antibacterial and anti-inflammatory properties. We revealed the expression of proteins and genes in P. aeruginosa after co-culture with TRQ. This study developed an assessment method to evaluate clinical resistance of P. aeruginosa using MALDI-TOF MS identification and Biotyper database searching techniques. Additionally, it combined MIC determination to investigate changes in MDR-PA treated by TRQ. TRQ effectively reduced the MICs of ceftazidime and cefoperazone and enhanced the confidence scores of MDR-PA as identified by mass spectrometry. Using this evaluation method, the fingerprints of standard P. aeruginosa and MDR-PA were compared, and the characteristic peptide sequence (Seq-PA No. 1) associated with flagellum was found. The phenotypic experiments were conducted to confirm the effect of TRQ on the motility and adhesion of P. aeruginosa. A combination of co-immunoprecipitation and proteome analysis was employed, and 16 proteins were significantly differentially expressed and identified as potential candidates for investigating the mechanism of inhibiting resistance in P. aeruginosa treated by TRQ. The candidates were verified by quantitative real-time PCR analysis, and TRQ may affect these core proteins (MexA, MexB, OprM, OprF, OTCase, IDH, and ASL) that influence resistance of P. aeruginosa. The combination of multiple methods helps elucidate the synergistic mechanism of TRQ in overcoming resistance of P. aeruginosa.IMPORTANCEPseudomonas aeruginosa is an opportunistic pathogen closely associated with various life-threatening acute and chronic infections. The presence of antimicrobial resistance and multidrug resistance in P. aeruginosa infections significantly complicates antibiotic treatment. The expression of ß-lactamase, efflux systems such as MexAB-OprM, and outer membrane permeability are considered to have the greatest impact on the sensitivity of P. aeruginosa. The study used a method to assess the clinical resistance of P. aeruginosa using matrix-assisted laser desorption ionization time of flight mass spectrometry identification and Biotyper database search techniques. TanReQing injection (TRQ) effectively reduced the MICs of ceftazidime and cefoperazone in multidrug-resistant P. aeruginosa (MDR-PA) and improved the confidence scores for co-cultured MDR-PA. The study found a characteristic peptide sequence for distinguishing whether P. aeruginosa is resistant. Through co-immunoprecipitation and proteome analysis, we explored the mechanism of TRQ overcoming resistance of P. aeruginosa.

Efficient Inhibition of Bacterial Biofilm Through Interference of Protein-Protein Interaction of Master Regulator Proteins: a Proof of Concept Study with SinR- SinI Complex of Bacillus subtilis.

Biofilm-associated microbial growth is a major cause of environmental, industrial, and public health concern. Therefore, there is a pressing need to discover and develop efficient antibiofilm strategies. Regulatory proteins vital for biofilm formation might be ideal targets for developing novel antibiofilm therapeutics. Their activities often depend on protein-protein interactions. Therefore, such targets present unique opportunities and challenges to drug discovery. In Bacillus subtilis, a model organism for studying biofilms, SinR acts as the master regulator of the biofilm formation cascade. Under favourable growth conditions, it represses the epsA-O and tapA-sipW-tasA operons, which encode for essential structural components of biofilms. Under unfavourable growth conditions, SinI, an agonist protein, inactivates SinR by forming a heterotrimeric complex. This results in derepression of epsA-O and tapA-sipW-tasA operons and leads to the phenotypic switch from planktonic to biofilm-associated form. We hypothesized that inhibiting SinR-SinI interaction might warrant repression of epsA-O and tapA-sipW-tasA operons and inhibit biofilm formation. To evaluate this hypothesis, we carried out a drug repurposing study for identifying potential inhibitors of SinI. Cefoperazone and itraconazole were identified as potential inhibitors with virtual screening. The stability of their interaction with SinI was assessed in extended MD performed over 100 ns. Both cefoperazone and itraconazole showed stable interaction. In in vitro studies, cefoperazone hindered the interaction of purified recombinant SinI and SinR. In the whole cell-based biofilm inhibition assays also cefoperazone was found to efficiently inhibited biofilm formation. These results provide proof of concept for targeting protein-protein interaction of master regulators as potential target for discovery and development of antibiofilm therapeutics. We propose that similar drug repurposing studies targeting key regulators of biofilm formation cascade could be an efficient approach for discovering novel anti-biofilm therapeutics against priority pathogens.

Improvement of modified charcoal-cefoperazone-deoxycholate agar by supplementation with a high concentration of polymyxin B for detection of Campylobacter jejuni and C. coli in chicken carcass rinses.

Modified charcoal-cefoperazone-deoxycholate agar (mCCDA) was improved by supplementation with a high concentration of polymyxin B. The ability of the supplemented medium to isolate Campylobacter jejuni and C. coli from chicken carcass rinses was compared to that of Campy-Cefex agar and mCCDA. Modification of mCCDA with increased polymyxin B yielded a significantly (P < 0.05) higher isolation rate and greater selectivity than those achieved using Campy-Cefex agar and mCCDA.

Isolation and characterization of Aeromonas schubertii from diseased snakehead, Channa maculata (Lacepède).

Pure bacterial cultures were isolated from diseased snakeheads, Channa maculata (Lacepède), suffering high mortality in a farm in Zhongshan, southern China. Three isolates, namely ZS20100725, ZS20100725-1 and ZS20100725-2, were identified as Aeromonas schubertii. All the isolates showed high 16S rRNA sequence similarities with A. schubertii. The isolates exhibited strong virulence to snakeheads in experimental challenges with LD(50) ranging between 1.4 × 10(4) and 6.4 × 10(6) CFU g(-1). Two of the isolates were positive for haemolysin, elastase, lipase and lecithinase by phenotypic determination, which was further confirmed by PCR amplification of the haemolysin and elastase genes. In sterile liquid medium, the best growth conditions of strain ZS20100725 were 30 °C, pH 7 and 0.5% salinity (w/v). Antibiotic susceptibility tests showed that strain ZS20100725 was susceptible to cefoxitin, cefoperazone and chloramphenicol. Furthermore, histopathology of diseased snakeheads infected with A. schubertii showed necrosis and congestion in liver, kidney and spleen and also damage to the cardiac muscle, intestine and gills.

Repurposing of FDA approved drugs and their validation against potential drug targets for Salmonella enterica through molecular dynamics simulation.

Salmonella is a widely distributed pathogen causing infection of intestinal tract, typhoid, and paratyphoid fever. Number of drugs was developed against salmonella, but in the last few decades due to the emergence of drug resistant strains, most of these drugs became dormant. As a result Salmonellosis emerges as a trivial cause of human mortality worldwide; therefore, there is an urgent need for unexploited drug targets and drugs to treat Salmonellosis. As development of new drug molecules is very time consuming and costly, drug repurposing is in consideration as a better alternative. With the aim to identify a new drug molecule against the Salmonella through repurposing approach, we utilized 14 well reported druggable targets known to play a vital role in the life cycle of pathogens. These targets were used to screen DrugBank and got 53 FDA approved drugs against them. To find the interaction between considered target proteins and screened drugs, molecular docking was performed. Fourteen docked drug-target complexes with reasonable binding affinities were subjected to Molecular Dynamics Simulation (MDS) at 150 ns, using Amber18. At the end MMPBSA and MMGBSA calculations were performed for all stable complexes and finally, got 3 precise and favourable complexes, i.e. ArcB-Cefpiramide, MrcB-Cefoperazone, and PhoQ-Carindacillin. Rigorous structural and energetic analysis for these complexes validates the potential of drug molecules to act as therapeutic drugs against Salmonella enterica. With this study we hypothesize that the drugs Cefpiramide (DB00430), Cefoperazone (DB01329) and Carindacillin (DB09319) will be the good repurposed-drugs for the treatment of Salmonellosis. Communicated by Ramaswamy H. Sarma.

Restoring the selectivity of Bolton broth during enrichment for Campylobacter spp. from raw chicken.

AIMS: When isolating Campylobacter spp. from retail raw chicken using BS EN ISO 10272-1:2006, contaminants frequently cause overgrowth on mCCDA plates. Therefore, these organisms proliferate in the enrichment medium, Bolton broth, indicating a lack of selectivity in this medium. This study sought to characterize the contaminant flora and to devise a modified Bolton broth to inhibit their growth. METHODS AND RESULTS: Contaminants (n=30) from separate samples were identified and antibiotic resistances determined. Most (93%) were extended spectrum ß-lactamase (ESBL) producing Escherichia coli, able to hydrolyse the cefoperazone present in Bolton broth and mCCDA. To inhibit these organisms, original formulation Bolton broth was supplemented with potassium clavulanate, at three concentrations, and recoveries of campylobacters from raw chicken were determined. Using standard Bolton broth, only 49% of samples (n=104) yielded campylobacters, but supplementation with 2 mg l(-1) potassium clavulanate increased this significantly (P<0.05), with 91% of samples positive. CONCLUSIONS: Potassium clavulanate can restore the selectivity of Bolton broth when isolating Campylobacter spp. from raw chicken. SIGNIFICANCE AND IMPACT OF THE STUDY: Raw chicken is often contaminated with the pathogen Campylobacter, but the ISO methodology for its detection is becoming compromised by the increasing presence of antibiotic-resistant bacteria. A simple modification ensures effective detection of this pathogen.

Peptidomimetic-based identification of FDA-approved compounds inhibiting IRE1 activity.

Inositol-requiring enzyme 1 (IRE1) is a bifunctional serine/threonine kinase and endoribonuclease that is a major mediator of the unfolded protein response (UPR) during endoplasmic reticulum (ER) stress. Tumour cells experience ER stress due to adverse environmental cues such as hypoxia or nutrient shortage and high metabolic/protein-folding demand. To cope with those stresses, cancer cells utilise IRE1 signalling as an adaptive mechanism. Here, we report the discovery of the FDA-approved compounds methotrexate, cefoperazone, folinic acid and fludarabine phosphate as IRE1 inhibitors. These were identified through a structural exploration of the IRE1 kinase domain using IRE1 peptide fragment docking and further optimisation and pharmacophore development. The inhibitors were verified to have an impact on IRE1 activity in vitro and were tested for their ability to sensitise human cell models of glioblastoma multiforme (GBM) to chemotherapy. We show that all molecules identified sensitise glioblastoma cells to the standard-of-care chemotherapy temozolomide (TMZ).

[The reaction mechanism between cefoperazone and human serum albumin].

The reaction mechanism between cefoperazone and human serum albumin (HSA) and the affinity between cefoperazone and beta-lactamase were investigated by spectrometry and spectrofluorimetry. The interaction dissociation constants of human serum albumin and cefoperazone have been determined from a double reciprocal Lineweaver-Burk plot. The binding distance and the transfer efficiency between cefoperazone and HSA were also obtained according to the theory of Förster' non-radiation energy transfer. The result suggested that the main binding force between cefoperazone and HSA is electrostatic force interaction. The high beta-lactamase stability of cefoperazone may be correlative with its molecular structure. The antibiotic activity and valency connect with transfer efficiency and dissociation constant. The effect of cefoperazone on the conformation of HSA was also analyzed using synchronous fluorescence spectrometry.

Development of a Novel Chromogenic Medium for Improved Campylobacter Detection from Poultry Samples.

The presence of expanded-spectrum ß-lactamase (ESBL)-producing Escherichia coli is a common problem in the isolation of Campylobacter from poultry samples using conventional cefoperazone-based selective media. A novel chromogenic medium (CM-HT), based on modified charcoal cefoperazone deoxycholate agar (mCCDA), has been developed as a solution for improved Campylobacter detection from poultry samples. Although the basic components of CM-HT are the same as mCCDA, CM-HT uses both granular charcoal and sodium cefoxitin to enhance viewability and inhibit ESBL-producing bacteria. All tested Campylobacter jejuni (n = 31) and Campylobacter coli (n = 6) strains grew and formed purple-colored colonies on CM-HT. In contrast, the growth of all other tested microorganisms, including ESBL-producing E. coli strains, was suppressed by this medium. Additionally, 84 poultry samples were examined for the presence of Campylobacter using the ISO 10272-1 method (enrichment with Bolton broth) and the NIHSJ-02 method (enrichment with Preston broth) with mCCDA and CM-HT media for the isolation. The numbers of samples from which Camplylobacter was detected on CM-HT using Preston and Bolton broth were 22 and 18, whereas the numbers on mCCDA were 22 and 13, respectively. Only Campylobacter was detected on CM-HT using both enrichment broths; however, there were 5 and 19 samples from which ESBL-producing E. coli was detected on mCCDA using Preston and Bolton broth, respectively. Thus, there was a significant difference between CM-HT and mCCDA in selectivity for ESBL-producing E. coli regardless of which enrichment broth was used. The results obtained demonstrated that CM-HT is a possible solution for the improved isolation of Campylobacter from poultry samples.

Diffusibility of the newer cephalosporins into human interstitial fluids.

A skin window technique was used to investigate the ability of three of the newer cephalosporins, moxalactam, cefoperazone, and ceftriaxone, to enter the interstitial fluid of normal, healthy volunteers. Intravenous and intramuscular routes of delivery were compared. The method of delivery did not greatly affect diffusibility with moxalactam and ceftriaxone. Intravenous infusion resulted in greater diffusibility with cefoperazone than did intramuscular injection. Cefoperazone demonstrated the lowest diffusibility of the three test drugs. Ceftriaxone, administered at one-half the dose of cefoperazone and moxalactam, demonstrated the greatest ability to diffuse into interstitial fluid despite its high level of binding to plasma protein. The better diffusibility of ceftriaxone may be explained by a persistently high concentration gradient provided by its long serum half-life. Overall, the results support the concept of the concentration gradient as an important determinant of antibiotic activity.

Cefoperazone for empiric therapy in patients with impaired renal function.

Thirty-five patients with serious infections and impaired renal function were treated empirically with 2 to 8 g of cefoperazone per day. Infections included sepsis in 14, nonbacteremic urinary infections in nine, pneumonia in five, intra-abdominal infection in five, fasciitis in one, and malignant otitis externa in one. The average age of this group was 64.3 years, 25 had ultimately fatal underlying diseases, and their average serum creatinine level was 5.2 mg/dl. Infections were caused by Enterobacteriaceae in 23 patients, Streptococcus faecalis in five, Pseudomonas aeruginosa in four, Staphylococcus aureus in four, Hemophilus influenzae in three, and Staphylococcus epidermidis, Streptococcus pneumoniae, and Clostridium sordelli in one each. Overall, 32 patients had clinical and microbiologic cures, two had improvement, and one had failure. Hypoprothrombinemia occurred in 18 of 28 patients not given vitamin K for prophylaxis and occurred more often in those with serum albumin concentrations below 3.5 g/dl. Prothrombin times returned to normal within 36 hours of treatment with vitamin K, although two patients experienced mild hematemesis. In anicteric patients with liver function abnormalities, 2 g every 12 hours produced peak and trough serum concentrations that averaged 254 and 125 micrograms/ml, respectively, compared with 179.5 and 19.5 micrograms/ml, respectively, in five with normal liver function test results. In jaundiced patients treated with 1 g every 12 hours, trough concentrations were comparably elevated. Serum concentrations did not correlate with hypoprothrombinemia, but high levels throughout the dosing interval may have contributed to the excellent cure rate in this study.

In vitro activity of cefotaxime against clinically significant pathogens.

The present in vitro antibacterial activities of cefotaxime and 8 other cephalosporins (cefoperazone, cefmenoxime, cefpiramide, latamoxef, cefamandole, cefmetazole, cefotiam and cephazolin) were evaluated simultaneously in 384 strains of Gram-positive cocci, 595 strains of Enterobacteriaceae, 240 strains of non-fermenters and 143 strains of anaerobes and miscellaneous organisms. The results were expressed as minimum inhibitory concentration (MIC) range, MIC50 and MIC90. Of the beta-lactams, cefotaxime and latamoxef exhibited the highest activity against a wide variety of Gram-positive and Gram-negative bacteria. MIC90 of cefotaxime, however, for species of Pseudomonas aeruginosa, Xanthomonas maltophilia, enterococci, Bacteroides sp. and Clostridium difficile were more than 100 mg/L. Cefpiramide and cefoperazone were generally less active than these 2 agents. All strains were tested for beta-lactamase production by the cefinase disc method and the relationship of susceptibility to beta-lactams was evaluated in each species. The need was demonstrated for periodic susceptibility testing to be performed to better guide empirical antimicrobial therapy.

Beta-lactamase stability of cefoxitin in comparison with other beta-lactam compounds.

The beta-lactamase stability of cefoxitin, the second-generation cephamycin compound, was compared with that of cefamandole, cefoperazone, cefotaxime, moxalactam, carbenicillin, and piperacillin. Unlike cefamandole, cefoperazone, carbenicillin, and piperacillin, cefoxitin was not hydrolyzed by the common plasmid beta-lactamases, TEM-1, TEM-2, OXA-2, and SHV-1. Cefoxitin and moxalactam were the only agents stable to all chromosomal beta-lactamases, whereas cefamandole, cefoperazone, cefotaxime, carbenicillin, and piperacillin were destroyed by cephalosporinases of Proteus vulgaris and Bacteroides fragilis.

Antimicrobial activity, beta-lactamase stability and beta-lactamase inhibition of cefotetan and other 7-alpha-methoxy beta-lactam antimicrobials.

The antimicrobial activity of three 7-alpha-methoxy beta-lactams were compared to cefoperazone and ceftriaxone. All had a similar spectrum of activity against the Enterobacteriaceae, except cefoxitin. Cefotetan was only slightly less active than moxalactam against the Enterobacter spp. Ceftriaxone was most effective on Neisserias, Haemophilus spp, nonenterococcal Streptococcus spp, and Acinetobacter spp. Cefoperazone generally inhibited more pseudomonads while all of the "cephamycins" showed activity against Bacteroides fragilis and B. thetaiotaomicron. Beta-lactamase hydrolysis studies of six substrates having pharmacologic serum half lives of greater than or equal to 2 hrs were performed by bioassay and automated procedures. Excellent correlations were found between methods up to 24 hrs. A "lag-phase" was observed for several drug/enzyme combinations before initiation of significant substrate hydrolysis. The 7-alpha-methoxy beta-lactams were routinely more stable to the six representative enzymes (Richmond-Sykes types I-V) than other "stable" cephalosporins. Substrate hydrolysis rates resulting in greater than 50% drug loss in less than or equal to 1 hr generally produced resistant in vitro test results. Cefotetan, cefoxitin, moxalactam, ceftriaxone, and dicloxacillin were potent inhibitors of Type I (P99) beta-lactamases. Moxalactam demonstrated significant inhibition and affinity for the Type V enzyme while cefoperazone uniquely possesses affinity (so-called inhibition) for all tested beta-lactamases. Cefotetan appears to be a promising, beta-lactam compound with some in vitro characteristics comparable to the 1-oxa-beta-lactams and alpha-methoxyimino cephalosporins.

Transfer of cefoperazone into human skin fluid.

The transfer of cefoperazone into exudates from excoriated skin wounds was studied in 13 adolescent and adult patients. Subjects were given an intravenous bolus injection of 50 mg/kg of body weight. Concentrations of cefoperazone in serum and in exudate fluids were determined by bioassay using Escherichia coli as the test organism. Mean (+/- SD) cefoperazone concentration in serum reached 333.3 +/- 103.3 micrograms/ml 30 minutes after the injection and decreased to 16.4 +/- 5.7 micrograms/ml eight hours after the injection. In exudate fluids, the peak value was 52.7 +/- 22.1 micrograms/ml at one hour. Eight hours after the injection, the mean concentration in the exudate was 10.7 +/- 7.2 micrograms/ml, which was considerably above the minimum inhibitory concentrations for important pathogens.

Pharmacokinetic studies on the concomitant administration of piperacillin and cefazolin, and piperacillin and cefoperazone in rabbits.

The pharmacokinetics of each drug on the concomitant administration of piperacillin (PIPC) and cefazolin (CEZ) or cefoperazone (CPZ) were studied in rabbits. When rabbits received the consecutive drip infusion administration of CEZ (0.71 mg/kg/minute) and PIPC (1.38 mg/kg/minute) and likewise of CPZ (0.72 mg/kg/minute) and PIPC (1.54 mg/kg/minute) for 1 hour, respectively, the serum half-lives of CEZ and CPZ were respectively prolonged about 1.8 and 1.6 times during drip infusion of PIPC than administered alone. However, when the sequence of administration were reversed, the serum levels of PIPC were not affected by the consecutive drip infusion administration of CEZ and CPZ. To study these findings in detail, the single intravenous dose of 20 mg/kg of CEZ and CPZ were administered under drip infusion of PIPC (2.65-2.93 mg/kg/minute). The serum half-lives of CEZ and CPZ were also prolonged about 5.4 and 1.9 times, respectively, whereas urinary excretion of CEZ, and urinary and biliary excretion of CPZ were reduced by PIPC. Moreover, when the single intravenous dose of 20 mg/kg of PIPC were administered under drip infusion administration of CEZ (0.96-2.60 2.60 mg/kg/minute), the pharmacokinetics of PIPC was not affected by the presence of CEZ. However, under drip infusion administration of CPZ (2.60-2.70 mg/kg/minute), the PIPC serum half-life was prolonged about 1.4 times, and biliary excretion of PIPC was reduced but urinary excretion was not. From the results of renal clearance experiments, tubular secretion appeared to be the predominant mechanism of renal elimination for these three drugs. These results indicate that PIPC influences the pharmacokinetics of both drugs by the competitively inhibiting tubular secretion in CEZ, and tubular secretion and hepatic transport system in CPZ. Therefore, in this respect PIPC seems to have probenecid-like action.

First and second derivative spectrophotometric determination of cefoperazone and sulbactam in injections.

A simple, spectrophotometric assay to measure the concentrations of cefoperazone and sulbactam in injectable formulations is described. Since zero-order spectra are subject to interference, derivative spectrophotometry was used to enhance the spectral details. A linear relationship between derivative amplitudes and the concentrations of the compounds was found. Beer's law is obeyed up to 75 and 80 micrograms ml-1 of cefoperazone in the first and second derivative modes, respectively, and up to 75 micrograms ml-1 of sulbactam in the second derivative mode. Detection limits were 0.64 and 0.88 microgram ml-1, respectively for cefoperazone in the first and second derivative modes and 0.30 micrograms ml-1 for sulbactam in the second derivative mode. The method is rapid, simple, does not require a separation step and has successfully been applied to the assay of commercial injections containing cefoperazone and sulbactam.

NMR study of whole rat bile: the biliary excretion of cefoperazone and benzyl chloride by an isolated perfused rat liver.

1H NMR spectroscopy at 400 MHz has been applied to the analysis of whole bile samples produced by the isolated perfused rat liver. Using relatively simple NMR experiments biliary excretory products of cefoperazone and benzyl chloride were identified as cefoperazone itself and a benzyl-glutathione conjugate, respectively. Our use of 13C isotopic labelling demonstrates how 1H/13C heteronuclear NMR techniques can be used to produce uncrowded and informative spectra from whole bile. From the use of a HMQC-COSY experiment the structure of a benzyl-glutathione conjugate contained in whole bile was confirmed.

Pharmacokinetics of cefoperazone after single and multiple doses.

The pharmacokinetics of cefoperazone was determined following single and multiple intravenous and intramuscular administrations in man. Ten subjects at each dose level were given eleven successive doses, at 12 h intervals of 500 and 1000 mg i.m. and i.v.. Serum concentrations and urinary excretion were determined in all subjects after the first, fifth and eleventh doses. The first i.m. doses yielded mean peak serum levels of 37 micrograms/ml and 76 micrograms/ml at 1.0 h after injection. The first i.v. doses yielded mean serum levels of 93 and 180 micrograms/ml at 5 min after the injection. No tendency toward drug accumulation was observed on multiple dosage. The pharmacokinetics could be described by a linear, open, two-compartment model of drug distribution. The terminal serum half-life (2.1-2.4 h after i.v. doses and 2.6-2.8 h after i.m. doses) remained essentially constant over the period of the study by dose levels. The no-significant differences of areas under the curve between the two routes, at two doses, show the absolute bioavailability of cefoperazone was about 95% following i.m. administration. The high binding to serum proteins (90%) influences favourably the pharmacokinetic parameters of cefoperazone. It yielded high and prolonged serum concentrations and has very useful distribution properties. These favourable properties, together with its good antibacterial activity, suggest that cefoperazone will be effective in treating bacterial infections in human beings.