Disk Diffusion Susceptibility Testing Research Articles

Antibacterial activity of sustainable composites derived from epoxidized natural rubber/silver-substituted zeolite/poly(lactic acid) blends

Sustainable composites derived from epoxidized natural rubber (ENR)/silver-substituted zeolite (AgZ)/poly(lactic acid) (PLA) blends possessing antibacterial activity were reported. ENR, herein, acted as an antibacterial promoter providing more hydrophilicity to the composites and facilitating water diffusion. Two methodologies were used to prepare composites, including solution casting (S) as well as solution casting followed by roll milling (SR). Both composites were compared in terms of morphology, AgZ dispersion, water absorption, and antibacterial activity. The shift of Tg and tan δ toward lower temperature of PLA composites consistently confirmed the compatibility between ENR and PLA by DSC and DMA results, respectively. The good AgZ distribution was observed in composites-SR, as confirmed by SEM/EDX. The results of agar disk diffusion susceptibility test showed that PLA, AgZ/PLA, and even ENR/AgZ/PLA composites-S showed no or less inhibition zone; meanwhile, ENR/AgZ/PLA composites-SR showed the significant inhibition zone against both Escherichia coli and Staphylococcus aureus. Besides, the antibacterial activity of the composites was required at least 5 wt% of AgZ. More than 98% inhibition of S. aureus growth by the composites-SR was observed during 2–24 h of cultivation, whereas AgZ/PLA provided the highest inhibition of only 75% at 24 h of cultivation. Hence, the incorporation of ENR enhances the bactericidal activity of the composites. In terms of mechanical properties, incorporating ENR into the composites decreased tensile modulus and strength, but increased the impact strength significantly. Therefore, the developed composites could be promising materials in food and biomedical fields in which antibacterial and impact resistance properties are required.

Evaluation of antimicrobial prophylaxis use and rate of surgical site infection in surgical ward of Wachemo University Nigist Eleni Mohammed Memorial Hospital, Southern Ethiopia: prospective cohort study

BackgroundSurgical site infection (SSI) is the foremost infection in the overall patient population, affecting up to 66% of operated patients and with a frequency up to nine times more than in developed countries. This study aimed to determine the rate, associated factors of surgical site infection, and identification of causative agents and their antimicrobial susceptibility in surgical ward of Wachemo University Nigist Eleni Mohamed Memorial Hospital (WUNEMMH), Southern Ethiopia.MethodProspective cohort study involving 255 patients who underwent surgical procedure in WUNEMMH from January 1 to September 1, 2017. We extracted data from medical chart, operational and anesthesia note by direct observation and interviewer administered semi-structured questionnaire which was validated. We collected wound specimens and processed it based on standard operating procedure, and disc-diffusion antibiotic susceptibility test was done. Data analysis was done using SPSS version 22.0. Factors significantly associated were identified using logistic regression model at P-value < 0.05 and 95%CI.ResultForty-two patients (16.5%) developed SSIs. The most causative organism of surgical site infection was Klebsiella pneumoniae (60%).Ciprofloxacin and ceftriaxone were sensitive antibiotics. Surgery waiting time more than 7 days [ARR = 2.48 (95%CI(1.28–4.79),P = 0.007], Operation time more than 1 h.[ARR = 2.13(95%CI(1.18–3.86),P = 0.012], and administering antibiotic before 1 h of operation [ARR = 5.05(95%CI(1.79–14.21),P = 0.002], smoking [ARR = 8.01 (95% CI (2.15 29.84),P = 0.002] were independently associated with surgical site infections.ConclusionThe rate of SSI was relatively high. Klebsiella pneumoniae was found to be the most causative agent for SSI. Organisms causing SSI were sensitive to commonly used antimicrobial agents in WUNEMMH.

Antibacterial and cytotoxic activities of the Syzygium polyanthum leaf extract from Malaysia.

Background and Aim:The increasing prevalence of drug resistance eventually leads scientist to discover new drugs that could solve the problem. Since ancient immemorial times, medicinal plants generally known as herbs were widely used in every culture throughout the world. In fact, currently up to 70,000 plant species have been screened for biological activities and about 70% ends up for commercialization. Therefore, this study was aimed to evaluate the potential cytotoxic and antibacterial effect of Syzygium polyanthum leaves which are local Malaysia plants, against 4T1 and MCF-7 mammary carcinoma cells, respectively, and also against bacteria causing mastitis in cows.Materials and Methods:The cytotoxic effect of hydromethanolic extract of S. polyanthum against 4T1 and MCF-7 mammary carcinoma cells was evaluated using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The cells were treated with the concentration of extracts ranging from 15.63 µg/mL to 1000 µg/ml for 72 h, and the percentage of cell survivability was determined based on minimum concentration that was able to allow at least 50% growth of cancer cells (IC50) after 72 h. The antibacterial activity was tested against common bacteria causing mastitis in cow. The bacteria were isolated from milk samples. The antibacterial activity of the extract was determined by disk diffusion method and susceptibility test based on minimum inhibitory concentration (MIC).Results:Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus intermedius were isolated from the milk samples that positive for mastitis. The MIC values range from 7.12 mm to 13.5 mm. The extract exhibits the widest zone of inhibition (13.5±0.20 mm) at 1000 mg/ml of concentrations. The extract relatively has low cytotoxicity effect against 4T1 and MCF-7 cells with IC50 values ranging from 672.57±59.42 and 126.05±50.89 µg/ml, respectively.Conclusion:S. polyanthum exerts weak antibacterial activity and cytotoxic effect to mammary carcinoma cells. The extract does not toxic to cells. However, further study is recommended, especially, this plant should be tested for in vivo.

Determination of minimum inhibitory concentrations for silver sulfadiazine and other topical antimicrobial agents against strains of Pseudomonas aeruginosa isolated from canine otitis externa.

Otitis externa is a common presenting complaint in practice. Ear infections by Pseudomonas aeruginosa are particularly problematic due to the organism's high level of resistance and ability to damage the tympanum. Treatment should be based on susceptibility testing although minimum inhibitory concentrations (MICs) are not available for all treatment options. Silver sulfadiazine has been used in cases of recurrent P.aeruginosa otitis, although a MIC for silver sulfadiazine as a single agent has not been established. To describe susceptibility patterns of P.aeruginosa isolated from canine otitis externa and determine the MIC for silver sulfadiazine and other topical antimicrobials. Thirty-six P.aeruginosa isolates were collected from client-owned dogs, suffering from otitis externa. Susceptibility patterns were established using disc diffusion susceptibility testing against 17 antimicrobial agents. For determination of the MIC, selected strains were tested against increasing concentrations of marbofloxacin, enrofloxacin, gentamicin, polymyxin B and silver sulfadiazine using broth microdilution. For nine of 17 antimicrobial agents, complete resistance was seen in all isolates tested via disk diffusion susceptibility testing. Approximately 94% and 96% of isolates were susceptible to gentamicin and imipenem, respectively. These findings were consistent with broth dilution, where all strains were susceptible to gentamicin. Resistance was higher against polymyxin B and the fluoroquinolones. Silver sulfadiazine was effective invitro with a MIC ranging from 1 to 64μg/mL. As the MIC of silver sulfadiazine was lower than the concentration in a 1% preparation, such a product potentially represents a treatment option for dogs with P.aeruginosa otitis.

Expression of Lanosterol 14-Demethylase (ERG11) Gene of Three-Drug Combinations in Candida albicans

Patients with impaired immunity are at particular risk of infections with Candida albicans. Antifungal drugs such as azoles commonly used for candidiasis treatment, but drug resistance is one of the most common problems for public health. The aim of this study was to evaluate the expression of lanosterol 14-demethylase (ERG11) gene for three-drug combinations in C. albicans. Disk diffusion and broth microdilution susceptibility tests were employed to evaluate the synergic effects of amphotericin B, fluconazole, voriconazole, ketoconazole and itraconazole. Quantification of ERG11 gene expression was carried out in C. albicans treated with three-drug combinations of fluconazole/ ketoconazole/ voriconazole and fluconazole/ ketoconazole/ itraconazole. Three-drug combinations revealed synergistic and partial synergistic effect for all tested isolates (FIC index range of 0.27-0.77). The expression levels of ERG11 were down-regulated by three-drug combination of fluconazole/ ketoconazole/ voriconazole treatment. Fluconazole synergizes with ketoconazole and voriconazole in three-drug combination against C. albicans by targeting of the ERG11 gene.

Outbreaks of antimicrobial resistant Salmonella Choleraesuis in wild boars piglets from central-western Spain.

Salmonella enterica serovar Choleraesuis is the aetiological agent of swine paratyphoid being a highly invasive zoonotic pathogen. Wild boar natural populations are experiencing a demographical expansion as well as some farms are breeding this species to release for hunting with management sometimes identical to that of domestic pigs, including supplementation, grouping, and antibiotic treatments. This situation increases the chance of contact between wild boars and livestock, and potentially induces stress, with different sanitary consequences. The present work aims to describe the clinical features of recent outbreaks caused by S. Choleraesuis in wild boar from central‐western Spain, as well as the antimicrobial resistance and phylogenetic relationships of isolates involved. 28 strains of S. Choleraesuis were isolated from 28 different wild boars belonging to 10 different game states located in central western Spain and submitted to the Clinical Veterinary Hospital (CVH) of the University of Extremadura. Samples were taken from different organs and cultured according to the ISO 6579:2002 procedure. Suspicious colonies were identified by PCR and antimicrobial resistance was evaluated by disc diffusion susceptibility test and the presence of the main resistance genes as well as 18 plasmid replicons frequently found among the Enterobacteriaceae was verified by PCR. Pulsed field gel electrophoresis was applied to determine the genetic relationship between isolates. The outbreaks under study were characterized by high mortality (35%–84%) and a septicaemic presentation. S. Choleraesuis was isolated from all the wild boars analysed, and 26 of the 28 isolates presented resistance to at least one antibiotic. The predominant resistances found were against sulphonamide, streptomycin, tetracycline, and doxicicline and sul1, strA‐strB, and tetA were the most prevalent resistance genes among isolates. 10 strains carried FIIA, FIB+H/1 or FIIA+H/1 plasmids. PFGE classified the isolates into four different profiles, grouped into two clusters. This results show that prevention against S. Choleraesuis must be considered in the sanitary programs of the wild boar breeders.

Do plastics serve as a possible vector for the spread of antibiotic resistance? First insights from bacteria associated to a polystyrene piece from King George Island (Antarctica).

The retrieval of a polystyrene macro-plastic piece stranded on the shores in King George Island (South Shetlands, Antarctica) gave the opportunity to explore the associated bacterial flora. A total of 27 bacterial isolates were identified by molecular 16s rRNA gene sequencing and 7 strains were selected and screened for their ability to produce biofilm and antibiotic susceptibility profiles. All the bacterial isolates were able to produce biofilm. The Kirby-Bauer disk diffusion susceptibility test to 34 antibiotics showed multiple antibiotic resistances against the molecules cefuroxime and cefazolin (belonging to cephalosporins), cinoxacin (belonging to quinolones) and ampicillin, amoxicillin+clavulanic acid, carbenicillin and mezlocillin (belonging to beta-lactams). The obtained results suggest that plastics can serve as vectors for the spread of multiple resistances to antibiotics across Antarctic marine environments and underline the relevance of future studies on this topic.

Application of tuf gene sequence analysis for the identification of species of coagulase-negative staphylococci in clinical samples and evaluation of their antimicrobial resistance pattern.

IntroductionCoagulase-negative staphylococci (CoNS) are normal inhabitants of human skin and mucous membranes. However, CoNS represent one of the major nosocomial pathogens, especially in immunocompromised patients. The increasing incidence of CoNS and mainly methicillin-resistant strains underlines the need for an accurate identification of Staphylococcus isolates at the species level. Analysis of the tuf gene proved to be an accurate tool for the species identification of CoNS. The aims of this study were to identify the CoNS species by tuf gene-based polymerase chain reaction method and sequencing, and to determine the frequency of CoNS clinical isolates resistant to methicillin (MRCoNS) and other antibiotics.MethodsA total of 200 staphylococci isolates were collected from various clinical samples. Phenotyping methods were used for initial identification followed by polymerase chain reaction amplification of tuf gene with subsequent sequencing. The phylogenetic relationships among species were analyzed using the neighbor-joining method based on the partial gene sequence of tuf. Microbroth dilution test was used for screening methicillin resistance, and disk diffusion susceptibility testing was performed for evaluation of antibiotic resistance among the isolates.ResultsIn the present study, 125 isolates were identified as CoNS; among them, Staphylococcus epidermidis 54(43.2%) and Staphylococcus haemolyticus 50 (40.0%) were demonstrated as the most prevalent species. Resistance to methicillin was detected in 54.4% of the CoNS based on microbroth dilution method. In disk diffusion susceptibility testing, the greatest resistance of CoNS was demonstrated for cefoxitin (65.4%), cotrimethoxazole (54.4%), and clindamycin (49.6%), while daptomycin (87.2%) and linezolid (83.2%) showed the greatest effectiveness for CoNS isolates.ConclusionOur results confirmed the predominance of S. epidermidis and S. haemolyticus among CoNS isolates. The high prevalence of MRCoNS strains is a serious concern and strongly suggests the need for control program measures in our hospitals in order to reduce MRCoNS infections, especially in immunocompromised patients.

Characteristics of Shiga toxin producing- and enteropathogenic Escherichia coli of the emerging serotype O80:H2 isolated from humans and diarrhoeic calves in Belgium

ObjectivesRecently a highly virulent Escherichia coli O80:H2 pathotype carrying Shiga toxin genes, the intimin subtype eaeξ, and genes associated with the extraintestinal pathogenic E. coli (ExPEC) pS88 plasmid was described in France. In this study we examine the relatedness of Belgian E. coli O80:H2 isolated from humans and diarrhoeic calves as well their similarities with the French pathotype. MethodsEighteen Belgian E. coli O80:H2 strains (nine human Shiga toxin-producing E. coli (STEC) (2008–2016), two bovine STEC (1987) and seven bovine atypical enteropathogenic E. coli (aEPEC) (2009–2015)) were characterized with conventional PCR, disc diffusion susceptibility testing and whole genome sequencing. ResultsOnly nine sporadic human STEC O80:H2 cases have been detected in Belgium. All patients were female, just two of them suffered from haemolytic uremic syndrome. All studied strains had the eaeξ subtype, belonged to the multi-locus sequence type ST-301, and carried virulence genes associated with the type III secretion system and effectors not encoded by the locus of enterocyte effacement (LEE). Multiple genes of the pS88 plasmid were detected in all but two strains (one human and one calf STEC). The Shiga toxin subtypes stx1a (n = 3; one human, two calf), stx2a (n = 2) and stx2d (n = 6) were detected. All strains were multidrug resistant, two were extended-spectrum β-lactamase positive. Core genome MLST revealed that some human and calf E. coli differed by only 22 loci. ConclusionsThe STEC/ExPEC O80:H2 pathotype was present in calves in Belgium as early as 1987, but human infections have been rare and mostly mild. The human STEC and bovine aEPEC cluster together and have the potential to be as virulent as the French isolates, as shown by their similar gene content.

Frequencies and Antimicrobial Susceptibility of Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from Horses in South Korea

Background:Methicillin-ResistantStaphylococcus Aureus(MRSA) has become one of the most prevalent pathogens in animals and humans giving rise to various diseases. MRSA infection in horses and transmission between horses and humans have dramatically increased recently.Objective:This study investigated the isolation frequency and antimicrobial susceptibility of MRSA isolated from horses in South Korea.Method:Screening of the MRSA isolates was conducted by conventional methods and multiplex Polymerase Chain Reaction (PCR). Minimum Inhibitory Concentration (MIC) of oxacillin was determined by the broth microdilution test method. Overall antibiogram was obtained by disk diffusion susceptibility test. All antimicrobial tests were conducted in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines.Results:S. aureuswas isolated from 116 (19.46%) of 596 horses tested. Of the 116S. aureusisolates, 52 (8.72%) strains were identified as MRSA by multiplex PCR. Among the 52 MRSA strains, 24 (46.15%) and 28 (53.85%) were oxacillin-resistant MRSA (OR-MRSA) and oxacillin-susceptible MRSA (OS-MRSA), respectively. OR-MRSA showed the highest susceptibility to florfenicol (100.00%), followed by doxycycline (95.83%), cefepime (91.67%), tetracycline (75.00%), and trimethoprim/sulphamethoxazole (70.83%). OS-MRSA showed the highest susceptibility to florfenicol (100.00%) and trimethoprim/sulphamethoxazole (100.00%), followed by cefoxitin (96.43%), ciprofloxacin (92.86%), enrofloxacin (92.86%), lincomycin + spectinomycin (89.29%), cefuroxime (89.29%), and cefonicid (89.29%).Conclusion:This study may facilitate treatment and prevention of MRSA infections and further benefit not only horses, but also people related with horse farms, horse riding clubs and animal hospitals.

Identification of bacteria and fungi sampled from the conjunctival surface of normal horses in South-East Queensland, Australia.

To identify bacteria and fungi found on the conjunctival surface of normal horse eyes; to investigate potential risk factors for these microflora; and to determine their susceptibility to common topical ophthalmic antimicrobials. A total of 95 client-owned horses were studied. Horses within sub-tropical Australia (South-East Queensland) were sampled once between April 2012 and March 2013. A conjunctival swab was taken from each eye and cultured for aerobic bacteria and fungi. Organisms were identified by colony morphology and phenotype. Antimicrobial disk diffusion susceptibility testing for commonly used antimicrobials was performed. Positive bacterial cultures were returned from 187/190 (98.4%) eyes from 94/95 (98.9%) horses. The most common species included Staphylococcus spp. (25.2% of total bacterial isolates), Bacillus cereus (17.4%), Bacillus spp. (14.1%), and Corynebacterium spp. (8.9%). Most bacterial isolates were susceptible to neomycin and fluoroquinolones. Positive fungal cultures were returned from 111/190 (58.4%) eyes from 73 (76.8%) horses. The most common species identified included: Penicillium spp. (16.7% of fungal isolates), Aspergillus spp. (15.4%), and Scopulariopsis spp. (10.3%). Most (≥90%) molds were susceptible to ketoconazole, voriconazole, itraconazole, and miconazole. Yeasts were most susceptible to ketoconazole. There was no significant effect of breed, age, sex, purpose, or housing of the horse or climatic conditions on bacterial or fungal culture status. Bacteria and fungi were commonly isolated from the eyes of healthy horses. The antibiotic and antifungal susceptibilities identified can be used as a guide for empirical therapy after cytology in the treatment of corneal ulceration in horses.

In Vitro Antimicrobial Combinations for Pan-Drug Resistant Acinetobacter Species

Background: Pandrug resistant Gram-negative organisms (PDRGNs) have emerged, as a major threat to hospitalized patients. They have been associated with mortality rates ranging from 30 to 70%. Because of the high morbidity and mortality rates of severe pandrug resistant acinetobacter spp infections, combination therapies, as opposed to monotherapy, are suggested. A synergistic effect may be developed when antibiotics are used in combination. Through this synergistic effect, treatment efficacy can be improved and resistance can be prevented. Aim of the work: To investigate the use of in vitro antibiotic synergy test (checkerboard) for pandrug resistant acinetobacter species with a clinical feedback on the most synergistic antimicrobial combination. Materials and Methods: During this study, one hundred isolates of drug resistant acinetobacter species identified by routine culture and sensitivity using disc diffusion susceptibility test, were collected from critically ill patients admitted to Ain Shams University Internal Medicine Intensive Care Units. The isolates were subjected to: (i) Determination of MIC using Vitek 2 automated system to confirm resistance of acinetobacter species to all commercially available antibiotics, (ii) Broth micro-dilution method (BMD) for determination of tigecycline susceptibility, and (iii) Determination of antimicrobial synergy by broth micodilution (Checkerboard method). Results: Vitek 2 system results showed that, all of the 100 isolates were resistant to all antibiotics included in the study. On the other hand, 100% of the isolates were sensitive (S) to Colistin. As regards the results by Broth microdilution antibiotic susceptibility method, all 100 isolates (100%) were resistant to ampicillin/sulbactam, meropenem and ciprofloxacin, whereas 95 isolates (95%) were resistant to amikacin, whereas all 100 isolates (100%) tested were sensitive to tigecycline. The results of the antibiotic combinations were as follows; the activity of ampicillin/sulbactam in combination with amikacin showed synergy in (48%), addition in (42%) and indifference in (10%). The activity of ampicillin/sulbactam in combination with ciprofloxacin showed, synergy in (36%), addition in (52%) and indifference in (12%). The activity of meropenem in combination with amikacin showed, synergy in (26%), addition in (53%) and indifference in (21%). No antagonistic activity was detected between any of the antibiotic combinations used. Conclusion: The prevalence of XDR/PDR resistant Acinetobacter spp. was highest in blood samples (43%) followed by sputum samples (35%) recovered from critically ill patients admitted to Ain Shams University Internal Medicine Intensive Care Units. Vitek 2 system showed that, all of the 100 isolates were resistant to all antibiotics included in the study. On the other hand, 100% of the isolates were sensitive (S) to colistin. Broth microdilution antibiotic susceptibility method showed that, all 100 isolates (100%) were resistant to ampicillin/sulbactam, meropenem and ciprofloxacin, whereas 95 isolates (95%) were resistant to amikacin, whereas all 100 isolates (100%) tested were sensitive to tigecycline, indicating that acinetobacter spp. did not attain resistance to tigecycline yet. The broth microdilution antibiotic synergy test (Checkerboard method), being the reference method for assessing antimicrobial synergy, showed that the highest synergic activity belongs to ampicillin/sulbactam and amkacin (48%), and the lowest synergic activity belongs to meropenem and amikacin (26%).

Antibacterial activities of tannic acid against isolated ruminal bacteria from sheep

This present study was conducted to evaluate the antimicrobial effects of tannic acid (TA) against isolated ruminal bacteria from adult sheep. Rumen samples were collected from two (2) adults sheep, and a total of nine (9) ruminal bacteria were isolated from the sample. The sensitivity of the ruminal bacteria isolates to 0.63, 1.25, 2.50, 5.00 and 10.00 mg TA/mL of growth medium was determined using clearance zone (CZ) of Kirby-Bauer disc diffusion susceptibility test. There was observable increase in the sensitivity of all bacterial isolates as the level of TA increases. Not all bacterial isolates have the capacity to tolerate more than 1.25 mg TA/mL. The result shows that only 20% of the bacterial isolates had the capacity to tolerate 0.63 and 1.25 mg of tannic acid per liter. This concentration of tannic acid would be equivalent to 2% tannin in the diet of ruminant. Our findings shows that increase in concentration of tannic acid completely inhibited the ruminal bacteria from the sheep rumen.

An epidemiologic study of antimicrobial resistance of Staphylococcus species isolated from equine samples submitted to a diagnostic laboratory

BackgroundAntimicrobial resistance limits traditional treatment options and increases costs. It is therefore important to estimate the magnitude of the problem so as to provide empirical data to guide control efforts. The aim of this study was to investigate the burden and patterns of antimicrobial resistance (AMR) among equine Staphylococcus samples submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) from 1993 to 2009. Retrospective data of 1711 equine Staphylococcus samples submitted to the UKVDL during the time period 1993 to 2009 were included in the study. Antimicrobial susceptibility testing, that included 16 drugs, were performed using cultures followed by the Kirby-Bauer disk diffusion susceptibility test. The proportion of resistant isolates by animal breed, species of organism, sample source, and time period were computed. Chi-square and Cochran-Armitage trend tests were used to identify significant associations and temporal trends, respectively. Logistic regression models were used to investigate predictors of AMR and multidrug resistance (MDR).ResultsA total of 66.3% of the isolates were resistant to at least one antimicrobial, most of which were Staphylococcus aureus (77.1%), while 25.0% were MDR. The highest level of resistance was to penicillins (52.9%). Among drug classes, isolates had the highest rate of AMR to at least one type of β-lactams (49.2%), followed by aminoglycosides (30.2%). Significant (p < 0.05) associations were observed between odds of AMR and horse breed, species of organism and year. Similarly, significant (p < 0.05) associations were identified between odds of MDR and breed and age. While some isolates had resistance to up to 12 antimicrobials, AMR profiles featuring single antimicrobials such as penicillin were more common than those with multiple antimicrobials.ConclusionDemographic factors were significant predictors of AMR and MDR. The fact that some isolates had resistance to up to 12 of the 16 antimicrobials assessed is quite concerning. To address the high levels of AMR and MDR observed in this study, future studies will need to focus on antimicrobial prescription practices and education of both practitioners and animal owners on judicious use of antimicrobials to slow down the development of resistance.

Antibacterial Effect of Silver Diamine Fluoride on Cariogenic Organisms

To screen the possible antimicrobial activity of a range of clinically used, silver-based compounds on cariogenic organisms: silver diammine fluoride (SDF), silver fluoride, and silver nitrate. Preliminary screening disk-diffusion susceptibility tests were conducted on Mueller-Hinton agar plates inoculated with Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces naeslundii, organisms known to be cariogenic. In order to identify which component of the silver compounds was responsible for any antibacterial (AB) effect, and to provide controls, the following were also investigated at high and low concentrations: sodium fluoride, ammonium fluoride, ammonium chloride, sodium fluoride, sodium chloride, and sodium nitrate, as well as deionized water as control. A volume of 10 pL of a test solution was dispensed onto a paper disk resting on the inoculated agar surface, and the plate incubated anaerobically at 37°C for 48 hours. The zones of inhibition were then measured. Silver diammine fluoride, silver fluoride, silver nitrate, and ammonium fluoride had significant AB effect (p < 0.05) on all three test organisms, although ammonium fluoride had no effect at low concentration; the remaining other compounds had no effect. Silver ions appear to be the principal AB agent at both high and low concentration; fluoride ions only have an AB effect at high concentration, while ammonium, nitrate, chloride and sodium ions have none. The anticaries effect of topical silver solutions appears restricted to that of the silver ions. Silver compounds, such as SDF, silver fluoride, and silver nitrate have AB effect against cariogenic organisms and these may have clinical impact in arresting or preventing dental decay. Sodium fluoride did not have AB effect under the conditions tested.

Antifungal Activities of Copper Surfactants Derived from Neem (Azadirecta indica) and Karanj (Pongamiapinnata) Oils: A Pharmaceutical Application

Different methods were applied on Neem and Karanj oils; their Copper (II) soaps and also their Copper (II) soaps benzothiazole complexes to study their comparative fungicidal study. To find the biological activity different methods were used i.e. Antifungal Disk Diffusion Susceptibility Testing of Yeasts; approved Guideline (M 44-A, NCCLS, USA) and antifungal testing of Alternaria alternata suggested by Booth and Hawks worth. The testing was done on two species of Candida i.e. C.albicans and C.krusei. Antimicrobial disks used were Fluconazole, Amphotericin, Clotrimazole and Ketoconazole. These antimicrobial disks were used as standard, as the strains of Candida albicans and Candida krusei are susceptible to them. The diameter of zones of testing disks was compared with the zone diameter of these standards antimicrobial agents.

The influence of silver and copper ions on the antibacterial activity and local electrical properties of single sepiolite fiber: A conductive atomic force microscopy (C-AFM) study

This is a study to analyze antibacterial and electrically-conductive sepiolite, and to evaluate its potential usage as biomaterials, medical products, sensors and electronics. Silver and copper ions were used to modify the properties of sepiolite through a multi-step procedure. During the modification of the sepiolite fibers, the most significant adsorption rates were obtained at metal uptake concentrations of 50mg/g for Ag+ and 80mg/g for Cu2+. This was found to fit the Langmuir isotherm model, thereby indicating the formation of a monolayer on the sepiolite surfaces by silver and copper ions. The effects of adsorbed silver and copper ions at the optimum metal uptake concentrations were then compared in terms of their antibacterial activity and electrical conductivity.Serial broth dilution and Kirby-Bauer disk diffusion susceptibility tests on Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923) were both utilized in this study. Metal ions that neutralized bacteria, and their minimum inhibitory concentrations (MIC), were measured at 50mg/L for Ag+ and 100mg/L for Cu2+. Additionally, the current distributions of metal ions over a single sepiolite fiber could also be characterized through the use of C-AFM. Interestingly, for the first time, local electric current variations and the potential gradients of Ag+ and Cu2+ sorped sepiolite fiber surfaces were detected. Their C-AFM generated current image and line scans showed that silver electrons transfer much more rapidly than those of copper; however, raw sepiolite demonstrates no antibacterial or current properties. Therefore, the fibrous clay mineral used in this study might be a good candidate for highly effective and innovative clay-based applications.

Can Ceftazidime-Avibactam and Aztreonam Overcome β-Lactam Resistance Conferred by Metallo-β-Lactamases in Enterobacteriaceae?

Based upon knowledge of the hydrolytic profile of major β-lactamases found in Gram-negative bacteria, we tested the efficacy of the combination of ceftazidime-avibactam (CAZ-AVI) with aztreonam (ATM) against carbapenem-resistant enteric bacteria possessing metallo-β-lactamases (MBLs). Disk diffusion and agar-based antimicrobial susceptibility testing were initially performed to determine the in vitro efficacy of a unique combination of CAZ-AVI and ATM against 21 representative Enterobacteriaceae isolates with a complex molecular background that included blaIMP, blaNDM, blaOXA-48, blaCTX-M, blaAmpC, and combinations thereof. Time-kill assays were conducted, and the in vivo efficacy of this combination was assessed in a murine neutropenic thigh infection model. By disk diffusion assay, all 21 isolates were resistant to CAZ-AVI alone, and 19/21 were resistant to ATM. The in vitro activity of CAZ-AVI in combination with ATM against diverse Enterobacteriaceae possessing MBLs was demonstrated in 17/21 isolates, where the zone of inhibition was ≥21 mm. All isolates demonstrated a reduction in CAZ-AVI agar dilution MICs with the addition of ATM. At 2 h, time-kill assays demonstrated a ≥4-log10-CFU decrease for all groups that had CAZ-AVI with ATM (8 μg/ml) added, compared to the group treated with CAZ-AVI alone. In the murine neutropenic thigh infection model, an almost 4-log10-CFU reduction was noted at 24 h for CAZ-AVI (32 mg/kg every 8 h [q8h]) plus ATM (32 mg/kg q8h) versus CAZ-AVI (32 mg/kg q8h) alone. The data presented herein require us to carefully consider this new therapeutic combination to treat infections caused by MBL-producing Enterobacteriaceae.

Clinical Epidemiology and Antibiogram of UTI Patients Attended Different Hospital in Khartoum, Sudan

Urinary tract infections are the most common bacterial infections in humans, both as community-acquired and healthcare-associated infections. The present study was aimed to determine the distribution and antimicrobial susceptibility of strains isolated from urinary tract infections. A hospital cross-sectional based study includes 150 clinically suspected cases of urinary tract infections attended different hospital in Khartoum. Midstream urine samples were collected and pure isolates of pathogenic microorganisms were characterized by colony morphology, gram-stain and standard biochemical procedures. A standard method of agar disc diffusion susceptibility testing method was used to determine susceptibility patterns of the isolates. The most common pathogens isolated were E. coli (57.3%), K. pneumonia (16.7%), P. aeruginosa (14%), E. feacalis (4%). C. albicans (8%). For all UTI isolates, least resistance was observed, E. coli and Klebsiella pneumoniae showed the highest percentage of resistance to ampicillin, Cefepime, Amikacin and Ciprofloxacin, followed by Gentamycin and Imipenem. Significant bacteriuria has been observed. Majority of the isolates were resistant to the commonly prescribed antibiotics. Identifying the pathogen, choosing correct antibiotics, limiting their excess use, improving resistance surveillance systems will help controlling this global problem.

Epidemiological profile of uropathogenic enterobacteria producing extended spectrum beta-lactamases

RésuméLes infections urinaires à entérobactéries productrices de bêtalactamases à spectre élargi (E-BLSE) constituent un risque infectieux, un enjeu thérapeutique de taille et peuvent même conduire dans certains cas à des impasses du fait de leur multi-résistance aux antibiotiques. Le but de ce travail est de préciser le profil épidémiologique des (E-BLSE) uropathogènes et décrire leur niveau actuel de résistance aux antibiotiques pour une meilleure prise en charge des patients selon les données locales. Il s'agit d'une étude rétrospective sur une période de trois ans (du 1er janvier 2013 au 31 décembre 2015) concernant toutes les souches d'E-BLSE isolées de tous les ECBU traités au laboratoire de microbiologie de à l'Hôpital Militaire Moulay Ismail de Meknès. La culture a été faite selon les techniques usuelles, et l'antibiogramme a été réalisé par méthode de disque diffusion sous gélose Muller-Hinton selon les recommandations du Comité de l'antibiogramme de la Société française de microbiologie CA-SFM 2013/2014. Cette étude a permis de noter une importante prévalence globale d'isolement des E-BLSE (12.2%), particulièrement chez les patients hospitalisés (54.8%) dont la plus grande prévalence (72%) a été enregistrée dans le service d'urologie. Parmi ces E-BLSE Escherichia coli constitue la majorité (61%) des isolats, cependant au sein de la même espèce Klebsiella pneumoniae est le plus producteur de BLSE (25.8%). L'étude de l'antibioresistance des E-BLSE durant ces trois ans a mis en évidence des co-résistances à la ciprofloxacine (92.5%), au sulfametoxazole-trimethoprime (88,4%), à la gentamycine (67,2%). Globalement nos résultats sont en accord avec les données des autres pays méditerranéens exception faite pour l'amikacine dont la résistance est très basse (6.1%) dans notre étude. Cette étude a montré que la prévalence des E-BLSE en milieu hospitalier est importante et que sa diffusion en milieu communautaire est un fait préoccupant. Ces E-BLSE sont généralement résistantes aux antibiotiques, notamment des aux molécules utiles en urologie.