Diffusion Inhibition Zone Research Articles

Enhancing anti‐biofouling property by incorporating graphene oxide‐silver nanocomposite into polycaprolactone membrane for ultrafiltration application

AbstractBACKGROUNDThe control of biofouling is crucial in the membrane separation process. In the present study, graphene oxide‐silver (GO‐Ag) nanocomposite was fabricated and incorporated into polycaprolactone (PCL) membrane for the first time to increase its antibacterial properties and reduce its biofouling. Characterization of GO‐Ag nanocomposite was done by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier‐transform infrared (FTIR) spectroscopy. The PCL/GO‐Ag membranes were also characterized by XRD, attenuated total reflectance Fourier‐transform infrared (ATR‐FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), porosity determination, water contact angle measurement, and tensile test. Furthermore, pure water flux (PWF) and bovine serum albumin (BSA) rejection of the membranes were evaluated. Finally, the antibacterial activity of membranes was investigated by diffusion inhibition zone test and plate count of colony‐forming units.RESULTSThe results demonstrated that Ag nanoparticles were formed on the GO surfaces. In addition, membranes incorporated with the GO‐Ag nanocomposite were more hydrophilic, more porous, and more permeable to pure water while showing a lower protein rejection in the filtration of a BSA solution. Adding the GO‐Ag nanocomposite to the PCL membrane increased the inhibition effect against bacteria. The colony counting method confirmed that PCL/GO‐Ag membranes had higher antibacterial properties than the pure PCL membrane, and the PCL/1.8% GO‐Ag membrane represented the maximum antibacterial efficiency of 90% and 98% against P. aeruginosa and S. aureus, respectively.CONCLUSIONOverall, by the incorporation of GO‐Ag nanocomposite into the PCL membrane, PWF and antibacterial property were augmented, while protein rejection dropped. © 2023 Society of Chemical Industry.

Silver-Modified β-Cyclodextrin Polymer for Water Treatment: A Balanced Adsorption and Antibacterial Performance

Water pollution caused by organic pollutants and pathogenic microorganism is a critical issue. In this study, we reported a silver-modified β-cyclodextrin polymer (CD-CA/PDA-Ag) used for the removal of dyes and the suppression of microorganisms from water. In order to avoid silver nanoparticles agglomeration, the material was first coated with polydopamine (PDA) on β-cyclodextrin matrix, whose reducing catechol groups subsequently immobilized silver ions in situ to form uniformly dispersed silver nanoparticles. CD-CA/PDA-0.5Ag displayed a high adsorption capacity of methylene blue (535.93 mg/g), which is mainly attributed to electrostatic interactions, host-guest inclusions and π-π bond stacking effects. Furthermore, both diffusion inhibition zone tests and colony formation unit tests were investigated, which showed excellent antimicrobial capability on Escherichia coli (E. coli) and Staphylococcus aureus (S. auerus). Overall, CD-CA/PDA-Ag proved to have an excellent adsorption capacity and antibacterial performance, which provides a great potential in water purification.

Antibacterial thin film nanocomposite forward osmosis membranes produced by in-situ reduction of selenium nanoparticles

In this study, we present a facile method for the in-situ reduction of selenium nanoparticles (Se NPs) on a thin-film composite forward osmosis (FO) membrane. As an essential nutrient, Se is superior in terms of both low off-target toxicity and application potential. Given the superiority of Se, this study explored the application of Se NPs in the field of FO membrane separation and water treatment. In this study, Se NPs were evenly distributed on the polyamide layer of thin film nanocomposite (TFN) FO membranes and were found to significantly improve the hydrophilicity of the membrane surface and reduce the zeta potential value. Moreover, the water flux increased from 14.0 L m−2 h -1 (TFC FO) to 16.6 L m−2 h -1 (1 wt% Se TFN FO), while a slight increase in the reverse salt flux was observed. The diffusion inhibition zone tests revealed distinct antibacterial effects, and the bacteriostatic rate (BR) and live and dead cell staining tests showed a high BR (100 % of 1.5 wt% Se) of the Se NP-modified membranes on both gram-negative (Escherichia coli) and gram-positive bacteria (Staphylococcus aureus). Thus, Se NPs as antibacterial agents offer a new option for membrane functionalization and water treatment.

Proposal of Epidemiological Cutoff Values for Apramycin 15 μg and Florfenicol 30 μg Disks Applicable to Staphylococcus aureus.

Apramycin and florfenicol are two antimicrobial agents exclusively used in veterinary medicine. Resistance determinants to these antimicrobial agents have been described in several staphylococci, yet no inhibition zone-based epidemiological cutoff (ECOFF) values are available to detect populations harboring resistance mechanisms. In this study, we propose disk diffusion inhibition zone ECOFF values of Staphylococcus aureus for apramycin and florfenicol. The susceptibility to apramycin and florfenicol was evaluated by disk diffusion of five S. aureus collections, comprising 352 isolates of animal (n = 265) and human (n = 87) origin. The aggregated distributions of inhibition zone diameters were analyzed by the normalized resistance interpretation method to obtain normalized wild-type (WT) population distributions and corresponding ECOFF values. The putative WT populations of S. aureus were characterized by an inhibition zone ≥15 mm (ECOFF = 15 mm) for apramycin and ≥21 mm for florfenicol (ECOFF = 21 mm). Five nonwild-type (NWT) isolates were detected for apramycin, all without inhibition zone and harboring the apmA gene, whereas five NWT isolates were identified for florfenicol, all carrying the fexA gene. The proposed ECOFF values for apramycin and florfenicol may be a valuable tool in future antimicrobial resistance monitoring and surveillance studies to identify S. aureus NWT populations toward these antimicrobial agents.

Engineering a dual-functional sulfonated polyelectrolyte-silver nanoparticle complex on a polyamide reverse osmosis membrane for robust biofouling mitigation

Reverse osmosis (RO) is considered a promising technology for addressing global water scarcity problems. However, biofouling is still a significant obstacle in the operation of RO membranes. In this study, a sulfonated polyelectrolyte-silver nanoparticle architecture was employed to endow polyamide RO membranes with robust repelling-and-killing bacterial abilities. The RO membrane surface was first functionalized by poly (3-sulfopropyl methacrylate potassium salt) (pSM) via atom transfer radical polymerization (ATRP), followed by in situ immobilization of silver nanoparticles (AgNPs). Static bacterial adhesion and diffusion inhibition zone tests revealed that hydrophilic and electronegative pSM brushes repelled bacterial attachment on the membrane surface while AgNPs can inactivate bacterial cells. In addition, the presence of pSM-AgNPs complex on the RO membrane surface exhibited the best anti-biofouling properties, maintaining ~90% water flux in long-term dynamic biofouling filtration. Moreover, good trap of pSM brushes for AgNPs could guarantee the long-term stability of repelling-and-killing bacterial abilities.

In situ synthesizing silver nanoparticels by bio-derived gallic acid to enhance antimicrobial performance of PVDF membrane

Modifying membranes with nanoparticles is a promising approach to mitigate biofouling in membrane preparation processes. However, high costs of the modification agents limit the practical applications of this approach. In this work, we developed a cost-effective and ecofriendly method to provide polyvinylidene fluoride membrane with a strong antimicrobial activity by loading silver nanoparticles (AgNPs). In this approach, gallic acid (GA) was used as a capturing and reducing agent to in situ synthesize AgNPs on membrane surface. The resulting AgNPs-functionalized membrane exhibited a 3.5-fold higher pure water flux and enhanced antifouling capacity compared to the control membrane. Specifically, AgNPs endowed the membrane a compelling antimicrobial activity on both Gram-positive and Gram-negative bacteria, evidenced by diffusion inhibition zone and bacterial proliferation test results. More importantly, pomegranate peel extracts rich in GA was effectively used in such a membrane functionalization approach. Taken together, this work demonstrates the robust in situ fabrication of antimicrobial AgNPs-functionalized membranes through bio-derived GA and provides a promising alternative for their potential practical applications.

Bioprospecting and LED-based spectral enhancement of antimicrobial activity of microalgae isolated from the west of Ireland

Antimicrobial screening programmes have shown that microalgae constitute a rich source of secondary metabolites exhibiting antimicrobial activity against human and aquaculture pathogens. In this study, extracts from 80 newly isolated marine and freshwater microalgae strains were tested for antimicrobial activity against 6 pathogens (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus and Candida albicans). Principal Component Analysis and Hierarchical Clustering analyses (PCA-HC) of 4320 disc diffusion inhibition zones defined three main groups comprising strains with polar fractions inhibiting gram-positive bacteria, strains which exhibited broad spectrum activity and strains with non-polar fractions inhibiting gram-positive bacteria and C. albicans. Minimum Inhibitory Concentration (MIC) values were determined for 23 promising strains, which returned an activity threshold ≥15mm inhibition zone diameter by disc diffusion method for at least one pathogen. The relationship between spectral quality and antimicrobial activity was further investigated for 5 promising strains (diatom Stauroneis sp. LACW_24, haptophyte Prymnesium sp. DMGCW_41, and chlorophytes cf. Chlorococcum sp. DMGCW_43, cf. Micractinium sp. LACW_01 and Tetraselmis sp. LACW_06), indicating a significantly higher bioactivity under blue light for the chlorophytes and red light for the diatom Stauroneis sp. LACW_24. Polar fractions from cf. Chlorococcum sp. DMGCW_43 and Stauroneis sp. LACW_24 possessed broad spectrum antibacterial activity with MIC values of 157μg/mL and 875μg/mL against P. aeruginosa, 157μg/mL and 1000μg/mL against E. coli, 438μg/mL and 875μg/mL against B. subtilis and E. faecalis, 110μg/mL and 219μg/mL, against S. aureus, respectively. This screening programme has led to the identification of several strains with promising antimicrobial activity. In addition, the manipulation of LED-based spectral quality to enhance the bioactivity of antimicrobial components within several candidate strains is described for the first time.

A simple and universal strategy to deposit Ag/polypyrrole on various substrates for enhanced interfacial solar evaporation and antibacterial activity

Solar-driven distillation is now considered as a rising technology for the supply of fresh water in the rare areas. As the crucial part of solar distillation, photothermal materials have been flourished investigated. Herein, we report a universal and facile method to construct a photothermal layer on various substrates to enhance the interfacial water evaporation via polypyrrole (PPy) polymerization and silver nanoparticles (Ag NPs) deposition. The photothermal Ag/PPy layer was firmly coated on six different substrates with an average solar absorption of 95.4% and Ag loading of 94.3 mg/L. One of the optimized resultant membranes (substrate is cellulose fibers) presents the ultrahigh solar evaporation rate of 1.55 kg m−2h−1 and a corresponding light-to-vapor efficiency of 92.6% with a silver loading of 74 μg cm−2. Bacterial diffusion inhibition zone experiments revealed clear antibacterial effects of the Ag/PPy membrane on bacteria. Furthermore, the Ag NPs deposited membrane had a rechargeability for multiple times upon their depletion, indicating sustainable anti-bacteria potential. Hence, our facial fabricated photothermal Ag/PPy layer can apply to substrates with different types for enhanced photothermal and anti-biocorrosion capacity, and may pave a new way to the long-term practical sustainable technique for the clean water production application.

Direct filtration procedure to attain antibacterial TFC membrane: A facile developing route of membrane surface properties and fouling resistance

In order to address a global issue in regard to the shortage of drinking water resources, reverse osmosis (RO) processes have been considerably attended to provide people with high-quality fresh water. In spite of many efforts carried out for preparation of efficient RO membranes, fouling/biofouling remains as a significant challenge. In this study, anti-bacterial polyamide thin film composite (PA-TFC) decorated with hydrophilic polyrhodanine (PRh) nanoparticles was fabricated through a novel route of direct filtration method. This method is a facile technique for modification of the membrane surface, in particular, for recovery of the membrane antibacterial agent which is lost during the process. The synthesized membranes were studied for morphology, surface functional groups, hydrophilicity, and surface roughness via FESEM, FTIR, contact angle, and AFM analysis. Both diffusion inhibition zone and colony formation unit tests exhibited excellent biocidal activity of the PRh loaded membranes against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus strains. Moreover, the best fouling resistance was assigned to PA-TFC membrane decorated with 0.5%wt. PRh, and PA-TFC membrane modified with 0.75%wt. PRh revealed the best salt rejection ability.

The prevalence and clinical significance of microcolonies when tested according to contemporary interpretive breakpoints for fluconazole against Candida species using E-test.

Changes in the interpretive-breakpoints for antifungals against various Candida species have raised the need to examine the significance of the phenomenon of the growth of microcolonies in agar diffusion inhibition zones, which has generally been considered negligible. The objective was to determine the incidence of cases in which microcolonies demonstrate fluconazole resistance according to current interpretive-breakpoints and whether their growth is associated with therapeutic failure. The fluconazole minimum inhibitory concentrations (MICs) of 100 blood culture isolates of Candida were performed by E-test on Roswell Park Memorial Institute (RPMI) agar and examined for the appearance of microcolonies. Fluconazole MICs of microcolonies were then determined over three generations. The significance of the phenomenon of microcolonies was determined according to clinical data retrieved from electronic files. Microcolonies were a common phenomenon among Candida isolates following incubation on RPMI agar, with a higher frequency among C. albicans isolates as compared to non-albicans Candida across generations (57-93% vs 31-93%, respectively) and a similar fluconazole susceptibility rate over three generations. The rate of microcolonies was similar in both patients with successful and unsuccessful outcome (41%vs 42%, respectively). Microcolonies are a common phenomenon. No increase in MIC was demonstrated throughout three generations of microcolony inoculation on RPMI, and no difference in clinical outcome was observed.

2068. Evaluation of Ceftazidime-Avibactam Disks from Different Commercial Manufacturers for Susceptibility Testing against Meropenem Nonsusceptible Enterobacteriaceae

BackgroundCeftazidime and avibactam (CAZ-AVI) diffusion disks have been widely used in hospitals and clinical laboratories in the United States for susceptibility testing of infections caused by Enterobacteriaceae and Pseudomonas aeruginosa. A few cases of high error rates and overcalling of resistance in some carbapenem-resistant Enterobacteriaceae (CRE) isolates have been reported. The purpose of this study was to evaluate the performance of CAZ-AVI diffusion disks made by two manufacturers in comparison with that of the standard broth microdilution (BMD) method for susceptibility testing against a large collection of CRE.MethodsA panel of 110 meropenem nonsusceptible Enterobacteriaceae clinical isolates, including 98 Klebsiella pneumoniae, eight Enterobacter cloacae, and four Escherichia coli were tested using CAZ-AVI (30/20 µg) diffusion disks manufactured by Hardy Diagnostics (Hardy) and BD Biosciences (BD). These isolates harbored various carbapenemase genes including KPC-2, KPC-3, VIM, NDM, OXA, ESBL, and altered OmpK35 and OmpK36. The same isolates were tested for susceptibility to CAZ-AVI by BMD using a custom-made Trek panel. Correlation between minimal inhibitory concentration (MIC) and disk diffusion inhibition zones was assessed based on Clinical and Laboratory Standards Institute (CLSI) breakpoints and error rate analysis.ResultsOverall disk diffusion inhibition zones correlated well with MIC for disks manufactured by both Hardy and BD according to CLSI CAZ-AVI breakpoints (susceptible/resistant): MIC ≤8/4/≥16/4 µg/mL, disk diffusion ≥21/≤20 mm. Error rates were low for the Hardy disks grown on Hardy and BD Mueller–Hinton agar (MHA) with 0.9% very major errors (VME)/1.8% major errors (ME) and 1.8% VME/5.5% ME, respectively. The error rates for BD disks grown on Hardy and BD MHA plates were 1.8% VME/0% ME and 1.8% VME/6.4 ME, respectively. ME rates appeared to be lower when Hardy MHA plates were used for both Hardy and BD disks.ConclusionCAZ-AVI (30/20 µg) disks manufactured by Hardy and BD performed well in susceptibility testing against a challenging set of CRE isolates. These data showed good categorical agreement between disk diffusion and BMD methods. Error rates were lowest when Hardy MHA plates were used for both Hardy and BD disks.Disclosures L. Y. Lin, Allergan: Employee, Salary. I. A. Critchley, Allergan (at time of study): Employee, Salary.

Antibiotic release and antibacterial efficacy in cement spacers and cement beads impregnated with different techniques: In vitro study.

This study aims to compare the antibiotic release and biological effectiveness of bead type and articulating spacers of different cement types with antibiotics added at alternative phases of cement preparation. Four gram vancomycin was added into two types of antibiotic-free cement (Simplex®, Biomet®) with similar viscosity and also gentamycin-containing cement (Refobacin®). Prepared specimens were used to create cement beads and articulating hip spacers, making a total of six different groups. Two alternative groups were formed by adding the Vancomycin while the cement was in dough phase. Antibiotic release and biological activity were evaluated with immunoassay techniques and agar-disk diffusion methods. All groups showed initial antibiotics surge in the first week, which was 2 to 4 times more evident in the beads group. Antibiotic release and change in release rate were significantly different between Simplex-alternative and Simplex, Biomet, Refobacin-beads, and between Biomet-spacer and Refobacin-beads groups (p<0.05). Elution of antibiotics was not different between mobile spacers prepared with conventional or alternative methods (p>0.05). Biomet cement showed larger diffusion inhibition zone in agar. There was no difference between biological activity of the bead and mobile designs of the Biomet brand (p>0.05). Inhibition zone analyses of agar and disk diffusion tests revealed significant differences between several groups (p<0.05). Cement beads provide superior antibiotic release regardless of cement type or preparation method. Simplex P® cement has lower anti-bacterial efficiency than Biomet®. Different methods for cement and antibiotics mixing and addition of extra vancomycin into the commercially drug loaded cement do not have any effect on the results.

In Vitro Susceptibility of Clinical Staphylococcus aureus Small-Colony Variants to β-Lactam and Non-β-Lactam Antibiotics.

The Staphylococcus aureus small-colony variant (SCV) phenotype has been associated with relapsing and antibiotic-refractory infections. However, little is known about the activities of antibiotics on clinical SCVs. Here, we demonstrated that SCVs without detectable auxotrophies were at least as susceptible to most β-lactam and non-β-lactam antibiotics in vitro as their corresponding clonally identical strains with a normal phenotype. After prolonged incubation, a regrowth phenomenon has been observed in gradient diffusion inhibition zones irrespective of the strains' phenotype.

Enhancing the antimicrobial activity of ginseng against Bacillus cereus and Staphylococcus aureus by heat treatment.

This study evaluated the antimicrobial activities [diffusion inhibition zone, minimum inhibitory concentration (MIC), and minimum bactericidal concentration], of heated ginseng extracts (ethanol and methanol). The extract yields, ginsenoside compositions, growth inhibitory effects against Bacillus cereus and Staphylococcus aureus and bacterial cell membrane potential changes, were also investigated. Methanol extracts of heated ginseng, showed higher antimicrobial activity than ethanol extracts. B. cereus was more easily inhibited than S. aureus. Ginseng heated at 100°C for 2 and 16h, showed maximum antimicrobial activity against B. cereus and S. aureus, respectively. In the growth inhibitory test, S. aureus and B. cereus were completely inhibited after 2 and 8h culture at the MIC. The cell membrane potential decreased with increasing concentration of extract, indicating cell metabolism disruption. Ginsenosides Rg3, a potent antibacterial substance, which were absent in non-heated ginseng, were produced by heating ginseng at 100°C for 4 and 8h, respectively.

Novel class 1 Integrons and sequence types in VIM-2 and VIM-11-producing clinical strains of Enterobacter cloacae

All VIM-producing Enterobacteriaceae (six Enterobacter cloacae) submitted to the Argentinian Reference Laboratory in Antimicrobial Resistance in the period 2008–13 were characterized. The isolates were referred from 6 nosocomial institutions located in 5 different cities across the country. All isolates showed carbapenem disk diffusion inhibition zones ≤22mm and synergism between a carbapenem disk and EDTA/SMA. The six isolates were PCR positive for blaVIM. Imipenem MICs were ≤1 to 8μg/ml. Typing by PFGE and MLST distinguished six pulsotypes and sequence types with blaVIM located on novel class 1 integron arrays: ECL-1: ST182, In883; ECL-2, ST90, In885; ECL-3, ST88, In346 with blaVIM-11; ECL-4, ST184, In900; ECL-5, ST749-new, In900; ECL-6, ST91 and uncharacterized In. Only ECL-2 was able to transfer blaVIM-2 to E. coli J53 by biparental conjugation. blaVIM was located in plasmids of 53–82Kb and in the chromosome (ECL-1 and ECL-5). The diversity of clones, class 1 integrons, plasmids and location of blaVIM, reveals the plasticity of the genetic elements described and highlights the importance of surveillance programs as tools to identify the transmission of these highly resistant metallo-β-lactamase-producing Enterobacteriaceae.

In Situ Reduction of Silver by Polydopamine: A Novel Antimicrobial Modification of a Thin-Film Composite Polyamide Membrane.

We report a facile method for the antimicrobial modification of a thin-film composite polyamide reverse osmosis (RO) membrane. The membrane surface was first coated with polydopamine (PDA), whose reducing catechol groups subsequently immobilized silver ions in situ to form uniformly dispersed silver nanoparticles (AgNPs) inside the coating layer. Agglomeration of AgNPs was not observed despite a high silver loading of 13.3 ± 0.3 μg/cm(2) (corresponding to a surface coverage of 18.5% by the nanoparticles). Both diffusion inhibition zone tests and colony formation unit tests showed clear antimicrobial effects of the silver loaded membranes on model bacteria Bacillus subtilis and Escherichia coli. Furthermore, the silver immobilized membrane had significantly enhanced salt rejection compared to the control PDA coated membrane, which is attributed to the preferential formation of AgNPs at defect sides within the PDA layer. This self-healing mechanism can be used to prepare antimicrobial RO membranes with improved salt rejection without scarifying the membrane permeability, which provides a new dimension for membrane surface modification.

Surface modification of thin film composite RO membrane for enhanced anti-biofouling performance

Anti-adhesion and antimicrobial coatings were prepared and applied on commercial thin-film-composite (TFC) polyamide (PA) membrane to enhance anti-biofouling performance. Polyvinyl alcohol (PVA) coating was modified with cationic polyhexamethylene guanidine hydrochloride (PHMG) polymer to obtain antimicrobial performance. ATR-FTIR, SEM and AFM investigated the surface chemistry and morphology of the coated membranes. The contact angle measurement was used to determine hydrophilicity and surface energy. All coated membranes revealed more hydrophilic and lower surface roughness compared to uncoated membrane. Lower number of adhered Pseudomonas aeruginosa (P. aeruginosa) bacteria was detected on coated membranes, indicating anti-adhesion performance. The colony forming unit (CFU) and diffusion inhibition zone (DIZ) tests determined antimicrobial activity of the coated membranes against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), showing the antimicrobial performance of PHMG. The results suggested that an optimal anti-fouling surface could be obtained applying a coating, which combines anti-adhesion and antimicrobial performance.

A rapid method of improving the criteria being used to interpret disc diffusion antimicrobial susceptibility test data for bacteria associated with fish diseases

This work presents an analysis of the consequence of using data sets containing small numbers of disc diffusion inhibition zones to calculate epidemiological cut-off values. Twenty replicate data sets that contained 10, 20, 40, 60, 80 and 100 zone size measurements were obtained by randomly sampling a previously published data set that consisted of inhibition zone measurements for discs containing 30 µg florfenicol, 30 µg oxytetracycline and 2 µg oxolinic acid against 217 isolates of Aeromonas salmonicida. Application of normalised resistance interpretation allowed epidemiological cut-off values to be estimated from all of these 360 data sets. The precision associated with the replicate cut-off values was a linear function of the log of the number of data points used to generate them. The frequency with which false sensitive and false resistance errors would have resulted from the application of the cut-off values generated from small data sets using normalised resistance interpretation were compared with those that would have resulted from the application of the breakpoints that have been reported as being currently in use. This comparison demonstrated that most laboratories could improve their interpretation of the disc diffusion data they obtain for any species by performing normalised resistance interpretation of their own data for that species. This would be true even if they possessed inhibition zone data for as few as ten members of that species.

Evaluation of the mastascanelite image analysis system for measuring zones of inhibition in disc diffusion susceptibility tests

In this evaluation a mastascanelite image analysis system is compared with manual measurement of disc diffusion inhibition zones. Data for 213 diverse organisms and a total of 1679 organism/antibiotic combinations gave an overall correlation coefficient of 0.988. The mean difference between readings was +0.425 mm, with 95% confidence limits of ±2.94 mm, and the majority of scanned zones (97.51%) fell within ±3 mm of the manual measurement. The mastascanelite system forms part of a laboratory suite and was found to be objective, accurate and rapid, reading and interpreting each plate in less than a second. Interfacing to the laboratory computer system facilitated data handling and performance control.

Comparative study of antibacterial activity of cefazolin sodium and of its crystalline modifications

Antibacterial activity of four crystalline modifications (ground, solvated and two desolvated) of cefazolin sodium (CZS) have been studied. Their antibacterial properties have been determined by means of minimal inhibitory concentrations (MIC 50 and MIC 90) and of disk diffusion inhibition zone values. The above-mentioned crystalline modifications (Mod.) of CZS-I, II, III and IV, respectively, have been shown to have differences in their antibacterial properties in comparison with the trade CZS as well as between themselves. Mod. I has higher or the same activity as CZS. The obtained results we have explained with the formation of different intermolecular H-bonds in the modifications could be due to the rotation about C α– C′ and C–N bonds in the amide groups in their molecules.