High MIC Values Research Articles

In Vitro Activity of Bedaquiline and Delamanid against Nontuberculous Mycobacteria, Including Macrolide-Resistant Clinical Isolates.

We evaluated the in vitro activities of the antimicrobial drugs bedaquiline and delamanid against the major pathogenic nontuberculous mycobacteria (NTM). Delamanid showed high MIC values for all NTM except Mycobacterium kansasii However, bedaquiline showed low MIC values for the major pathogenic NTM, including Mycobacterium avium complex, Mycobacterium abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. kansasii Bedaquiline also had low MIC values with macrolide-resistant NTM strains and warrants further investigation as a potential antibiotic for NTM treatment.

NDM-1-producing Escherichia coli isolated from pigs induces persistent infection with limited pathogenicity

NDM-1-producing Enterobacteriaceae are multidrug-resistant bacteria, also called superbacteria, that have become important global human health threats in recent years. However, data about NDM-1-producing bacteria in animals are rare. In this study, an NDM-1-producing Escherichia coli isolate (designated E120413) was obtained from pigs in Henan province, China in 2012. The susceptibility of E. coli E120413 to antimicrobial agents was determined using Kirby-Bauer disk diffusion and micro-dilution methods. Susceptibility tests indicated that E. coli E120413 was resistant to almost all common antibiotics with high MIC values obtained for most antibiotics tested. E. coli E120413 was detected in the heart, liver, spleen, lung, kidney, brain, stomach, duodenum, mesenteric lymph nodes, and fecal samples of piglets in both cohabitation and experimental groups and the bacteria persisted for more than 2 weeks. However, no obvious clinical symptoms or serious pathological lesions were observed. This is the first investigation of NDM-1-producing E. coli isolate from pigs in China. Although no significant pathological lesions were observed, NDM-1-producing E. coli was found to be highly transmissible and to cause persistent infection in pigs.

Adaptive bacterial response to low level chlorhexidine exposure and its implications for hand hygiene.

Chlorhexidine digluconate (CHG) is commonly used in healthcare, e.g. in skin antiseptics, antimicrobial soaps, alcohol-based hand rubs and oral or wound antiseptics. Aim of the literature review was to evaluate the potential of bacteria to adapt to low level CHG exposure. A maximum 4fold MIC increase to CHG was found after low level exposure in most of the 71 evaluated bacterial species. A strong adaptive mostly stable MIC change was described in strains or isolates of the healthcare-associated species E. coli, S. marcescens and P. aeruginosa (up to 500fold, 128fold or 32fold, respectively). The highest MIC values after adaptation were 2,048 mg/l (S. marcescens) and 1,024 mg/l (P. aeruginosa). A new resistance to tetracycline, gentamicin, meropeneme or triclosan was found in some adapted isolates. In E. coli horizontal gene transfer was induced (sulfonamide resistance by conjugation), pointing out an additional risk of sublethal CHG. The use of CHG in patient care - but also all other settings such as consumer products and households - should therefore be critically assessed and restricted to indications with a proven health benefit or justifiable public health benefits. Additional CHG has no health benefit when used in alcohol-based hand rubs and is not recommended by the WHO. For routine hand washing of soiled hands the use of plain soap is sufficient, CHG in soaps has no health benefit. In surgical hand antisepsis alcohol-based hand rubs should be preferred to CHG soaps. Implementation of these principles will help to reduce avoidable selection pressure.

Molecular Characterization and Antifungal Susceptibility of Clinical Fusarium Species From Brazil.

Fusarium is widely distributed in the environment and is involved with plant and animal diseases. In humans, several species and species complexes (SC) are related to fusariosis, i.e., F. solani SC, F. oxysporum SC, F. fujikuroi SC, F. dimerum, F. chlamydosporum, F. incarnatum-equiseti, and F. sporotrichoides. We aimed to investigate the susceptibility of Fusarium clinical isolates to antifungals and azole fungicides and identify the species. Forty-three clinical Fusarium isolates were identified by sequencing translation elongation factor 1-alpha (TEF1α) gene. Antifungal susceptibility testing was performed to the antifungals amphotericin B, itraconazole, voriconazole, posaconazole, and isavuconazole, and the azole fungicides difenoconazole, tebuconazole, and propiconazole. The isolates were recovered from patients with median age of 36 years (range 2–78 years) of which 21 were female. Disseminated fusariosis was the most frequent clinical form (n = 16, 37.2%) and acute lymphoblastic leukemia (n = 7; 16.3%) was the most commonly underlying condition. A few species described in Fusarium solani SC have recently been renamed in the genus Neocosmospora, but consistent naming is yet not possible. Fusarium keratoplasticum FSSC 2 (n = 12) was the prevalent species, followed by F. petroliphilum FSSC 1 (n = 10), N. gamsii FSSC 7 (n = 5), N. suttoniana FSSC 20 (n = 3), F. solani sensu stricto FSSC 5 (n = 2), Fusarium sp. FSSC 25 (n = 2), Fusarium sp. FSSC 35 (n = 1), Fusarium sp. FSSC18 (n = 1), F. falciforme FSSC 3+4 (n = 1), F. pseudensiforme (n = 1), and F. solani f. xanthoxyli (n = 1). Amphotericin B had activity against most isolates although MICs ranged from 0.5 to 32 μg mL-1. Fusarium keratoplasticum showed high MIC values (8–>32 μg mL-1) for itraconazole, voriconazole, posaconazole, and isavuconazole. Among agricultural fungicides, difenoconazole had the lowest activity against FSSC with MICs of >32 μg mL-1 for all isolates.

Epidemiology and susceptibility profile to classic antifungals and over-the-counter products of Malassezia clinical isolates from a Portuguese University Hospital: a prospective study.

Clinical epidemiological data about the distinct Malassezia species remain scarce. The recurrence of Malassezia-related skin diseases, despite long-term use of antifungals, raises concern about the hypothetical emergence of antifungal resistance. We aimed to assess the distribution of Malassezia species among patients from a University Hospital with pityriasis versicolor, seborrheic dermatitis and healthy volunteers, and to evaluate the susceptibility profile to classic antifungals and over-the-counter compounds, searching for clinical associations. The enrollment of volunteers was conducted at the Dermatology Department of a University Hospital over a 3 year period. Malassezia culture isolates were identified to the species-level by sequencing. The drug susceptibility profile was assessed according to a broth microdilution assay, as recommended by the Clinical Laboratory Standards Institute. A total of 86 Malassezia isolates were recovered from 182 volunteers. Malassezia sympodialis was the most frequent isolated species. We found high MIC values and a wide MIC range in the case of tested azoles, and very low terbinafine MIC values against most isolates. Previous topical corticosteroid therapy was associated with a significant increase of MIC values of fluconazole and of terbinafine. Conversely to other European studies, M. sympodialis was the most common isolated species, which might be related to geographic reasons. The impact of previous topical corticotherapy upon the antifungal susceptibility profile was hereby demonstrated. In vitro susceptibility test results suggest that terbinafine might be a valid alternative for Malassezia-related skin diseases nonresponsive to azoles.

Genetic polymorphisms of ABCB1 (P-glycoprotein) as a covariate influencing daptomycin pharmacokinetics: a population analysis in patients with bone and joint infection.

Daptomycin has been recognized as a therapeutic option for the treatment of bone and joint infection (BJI). Gene polymorphism of ABCB1, the gene encoding P-glycoprotein (P-gp), may influence daptomycin pharmacokinetics (PK). We aimed to examine population PK of daptomycin and its determinants, including genetic factors, in patients with BJI. We analysed data from patients who received daptomycin for BJI between 2012 and 2016 in our regional reference centre and who had measured daptomycin concentrations and P-gp genotyping. A population approach was used to analyse PK data. In covariate analysis, we examined the influence of three single nucleotide variations (SNVs) of ABCB1 (3435C > T, 2677G > T/A and 1236C > T) and that of the corresponding haplotype on daptomycin PK parameters. Simulations performed with the final model examined the influence of covariates on the probability to achieve pharmacodynamic (PD) targets. Data from 81 patients were analysed. Daptomycin body CL (CLDAP) correlated with CLCR and was 23% greater in males than in females. Daptomycin central V (V1) was allometrically scaled to body weight and was 25% lower in patients with homozygous CGC ABCB1 haplotype than in patients with any other genotype. Simulations performed with the model showed that sex and P-gp haplotype may influence the PTA for high MIC values and that a dosage of 10 mg/kg/24 h would optimize efficacy. Daptomycin dosages higher than currently recommended should be evaluated in patients with BJI. Gender and P-gp gene polymorphism should be further examined as determinants of dosage requirements.

Comparison of Minimum Inhibitory Concentration (MIC) value of statin drugs: A Systematic Review

Background: Microbial infection and its resistance to clinically approved drugs create a huge threat to human health. Emerging reports have indicated the potential of statin drugs in the treatment of various types of microbial infections. However, it is still unclear, how much concentration of statin is effective against microbial infections. In literature, Minimum Inhibitory Concentration (MIC) values of statin drugs vary according to strain, species, and the type of statins. Thus, the main aim of the current study is to compare the MIC values of various types of statins against various types of micro-organisms. The data related to statin and microbial infection has been extracted from Pub Med (from September 1 Methodology: 987 to October 2017). A total of 662 studies have been published from 1987 -2017 regarding statin and microbial infections. After inclusion and exclusion criteria, finally, 28 studies have been selected for comparative analysis of MIC values. Results: All the statin drugs have shown a significant effect on various types of microbial infections. Among all the tested statin drugs, Simvastatin has lower MIC value in almost all types of microorganisms as compared to other statin drugs. However, on S. pneumoniae and aspergillus, Fluvastatin has the lowest MIC values as compared to Simvastatin. Atorvastatin was found to be the most potent against almost all strains of gram-negative bacteria. However, Rosuvastatin and Pravastatin have high MIC value against all types of microorganisms. Further, FICI value indicated the synergetic effect of Simvastatin with Amphotericin B, Itraconazole, and Fluconazole against various strains of Cryptococcus. Conclusion: In conclusion, Simvastatin, Atorvastatin, and Fluvastatin could be developed as potential antimicrobial agents. However, further studies are required to understand its complete safety and efficacy profile..

Synthesis, In Vitro Biological Evaluation and In Silico Studies of Some New Heterocyclic Schiff Bases

Abstract2‐Hydroxy‐naphthaldehyde based heterocyclic Schiff base derivatives (1 a‐1 h) were prepared and characterized by multi‐spectroscopic techniques and elemental analysis. Antibacterial activity of all the compounds was tested against Streptococcus pneumoniae, Enterococcus faecalis, Pseudomonas aeruginosa, Salmonella enterica, Klebsiella pneumoniae and Escherichia coli bacterial strains. The antifungal potential of the synthesized compounds was also tested against three Candida strains (Candida albicans, Candida glabrata and Candida tropicalis). In the antibacterial activity, the compounds showed high MIC values and thus found less potent against all the tested bacterial strains. Interestingly, compounds 1 b and 1 c exhibited significant activity with MIC 125 μg/ml against all the tested fungal strains. Hemolytic assay against human RBCs revealed that compounds 1 b and 1 c showed less toxicity than the standard drug fluconazole at each tested concentration (25‐1000 μg/ml). In growth kinetics studies, compounds 1 b and 1 c significantly inhibited the growth of Candida cells at 2MIC and MIC concentrations. The interaction ability of lead compounds (1 b and 1 c) with Ct–DNA was carried out by absorption, fluorescence, hydrodynamic, cyclic voltammetery measurements and circular dichroism. Results suggested that compound 1 b and 1 c bind to Ct–DNA via an intercalative mode supported by molecular docking studies. The antioxidant potential of heterocyclic derivatives 1 b and 1 c was estimated by DPPH free radical and hydrogen peroxide assay which confirm that compounds exhibited significant antioxidant activity.

In vitro interactions of crocin with fluconazole against Candida isolates.

Background and Purpose:The incidence of invasive fungal infections has been increased in recent years. The growing use of azole drugs for prophylactic and therapeutic purposes has resulted in the gradual emergence of azole-resistant species. Accordingly, the introduction of a new strategy to improve the management of Candida infections is an urgent need. Regarding this, the present study was performed to evaluate the antifungal activities of crocin (Cro) alone and in combination with fluconazole.Materials and Methods: This study was conducted on 50 clinical isolates of four different Candida species. The identity of the isolates was confirmed using the internal transcribed spacer identification system. The interactions of Cro with fluconazole were investigated using a microdilution checkerboard method based on the Clinical and Laboratory Standards Institute reference technique with 96-well microtiter plates. Furthermore, the assessment of the interaction of drug combinations was accomplished using the fractional inhibitory concentration index (FICI) based on the Loewe additivity theory. Results:According to the results, Cro alone showed a relatively high MIC50 value (1 g/ml) against Candida species. Our results demonstrated indifferent interactions between Cro and fluconazole with a FICI range of 0.5-4 against Candida strains.Conclusion:The high MIC value for Cro against Candida species indicated its failure to show appropriate antifungal activity against this species. The MIC of this agent was not significantly reduced even by the addition of fluconazole. Therefore, other mechanisms which are not related to the mechanism of azole drugs are involved at high concentration of Cro.

Role of MIC levels of resistance to clarithromycin and metronidazole in Helicobacter pylori eradication.

Antimicrobial resistance to clarithromycin and metronidazole significantly affects the cure rate of standard therapies for Helicobacter pylori infection. We tested whether different MIC levels of resistance to these antibiotics play a role in therapeutic efficacy. This was a post hoc analysis of data from a therapeutic trial in which patients with antibiotic susceptibility testing (Etest) received first-line sequential therapy. The level of antibiotic resistance was classified according to MIC values into low (MIC from >0.5 to ≤8 for clarithromycin, and from >8 to ≤32 for metronidazole) and high (MIC from >8 to 256 mg/L for clarithromycin, and from >32 to 256 mg/L for metronidazole). Data from 1006 patients were included. There were 520 (51.7%) patients with susceptible strains, 136 (13.5%) with clarithromycin-resistant strains, 144 (14.3%) with metronidazole-resistant strains and 206 (20.5%) with clarithromycin-resistant and metronidazole-resistant strains. In the presence of double resistance, the cure rate was still high (38/41, 92.7%) when MIC levels were low and it was reduced (94/112, 83.9%) only when MIC levels of both antibiotics were high. The cure rates did not significantly differ between patients with single antibiotic-resistant strains, irrespective of MIC values, and those with susceptible strains. We found that MIC levels of resistance to either clarithromycin or metronidazole play a role in H. pylori therapy outcome and that bacterial resistance becomes relevant in vivo when clarithromycin-resistant and metronidazole-resistant strains have high MIC values for at least one of these antibiotics.

EmrR-Dependent Upregulation of the Efflux Pump EmrCAB Contributes to Antibiotic Resistance in Chromobacterium violaceum.

Chromobacterium violaceum is an environmental Gram-negative bacterium that causes infections in humans. Treatment of C. violaceum infections is difficult and little is known about the mechanisms of antibiotic resistance in this bacterium. In this work, we identified mutations in the MarR family transcription factor EmrR and in the protein GyrA as key determinants of quinolone resistance in C. violaceum, and we defined EmrR as a repressor of the MFS-type efflux pump EmrCAB. Null deletion of emrR caused increased resistance to nalidixic acid, but not to other quinolones or antibiotics of different classes. Moreover, the ΔemrR mutant showed decreased production of the purple pigment violacein. Importantly, we isolated C. violaceum spontaneous nalidixic acid-resistant mutants with a point mutation in the DNA-binding domain of EmrR (R92H), with antibiotic resistance profile similar to that of the ΔemrR mutant. Other spontaneous mutants with high MIC values for nalidixic acid and increased resistance to fluoroquinolones presented point mutations in the gene gyrA. Using DNA microarray, Northern blot and EMSA assays, we demonstrated that EmrR represses directly a few dozen genes, including the emrCAB operon and other genes related to transport, oxidative stress and virulence. This EmrR repression on emrCAB was relieved by salicylate. Although mutation of the C. violaceum emrCAB operon had no effect in antibiotic susceptibility or violacein production, deletion of emrCAB in an emrR mutant background restored antibiotic susceptibility and violacein production in the ΔemrR mutant. Using a biosensor reporter strain, we demonstrated that the lack of pigment production in ΔemrR correlates with the accumulation of quorum-sensing molecules in the cell supernatant of this mutant strain. Therefore, our data revealed that overexpression of the efflux pump EmrCAB via mutation and/or derepression of EmrR confers quinolone resistance and alters quorum-sensing signaling in C. violaceum, and that point mutation in emrR can contribute to emergence of antibiotic resistance in bacteria.

Echinocandin-Induced Microevolution of Candida parapsilosis Influences Virulence and Abiotic Stress Tolerance.

Candida species are a major cause of life-threatening bloodstream infections worldwide. Although Candida albicans is responsible for the vast majority of infections, the clinical relevance of other Candida species has also emerged over the last twenty years. This shift might be due in part to changes in clinical guidelines, as echinocandins became the first line of therapeutics for the treatment. Candida parapsilosis is an emerging non-albicans Candida species that exhibits lower susceptibility levels to these drugs. Candida species frequently display resistance to echinocandins, and the mechanism for this is well-known in C. albicans and Candida glabrata, where it is mediated by amino acid substitutions at defined locations of the β-1,3-glucan synthase, Fks1p. In C. parapsilosis isolates, Fks1p harbors an intrinsic amino acid change at position 660 of the hot spot 1 (HS1) region, which is thought to be responsible for the high MIC values. Less is known about acquired substitutions in this species. In this study, we used directed evolution experiments to generate C. parapsilosis strains with acquired resistance to caspofungin, anidulafungin, and micafungin. We showed that cross-resistance was dependent on the type of echinocandin used to generate the evolved strains. During their characterization, all mutant strains showed attenuated virulence in vivo and also displayed alterations in the exposure of inner cell wall components. The evolved strains harbored 251 amino acid changes, including three in the HS1, HS2, and HS3 regions of Fks1p. Altogether, our results demonstrate a direct connection between acquired antifungal resistance and virulence of C. parapsilosisIMPORTANCECandida parapsilosis is an opportunistic fungal pathogen with the ability to cause infections in immunocompromised patients. Echinocandins are the currently recommended first line of treatment for all Candida species. Resistance of Candida albicans to this drug type is well characterized. C. parapsilosis strains have the lowest in vitro susceptibility to echinocandins; however, patients with such infections typically respond well to echinocandin therapy. There is little knowledge of acquired resistance in C. parapsilosis and its consequences on other characteristics such as virulence properties. In this study, we aimed to dissect how acquired echinocandin resistance influences the pathogenicity of C. parapsilosis and to develop explanations for why echinocandins are clinically effective in the setting of acquired resistance.

In vitro activity of ceftaroline and ceftobiprole against methicillin-resistant Staphylococcus aureus with decreased susceptibility to vancomycin isolated in paediatric patients

Minimal inhibitory concentrations (MIC, mg/l) of ceftaroline and ceftobiprole were evaluated over 70 methicillin-resistant Staphylococcus aureus (MRSA) strains with vancomycin MIC ≥1 isolated in a paediatric hospital. The proportion of non-wild-type strains (MIC > epidemiological cut off) was 18% for ceftobiprole and 64% for ceftaroline. Only 1.4% of strains was resistant to ceftobiprole, and none to ceftaroline. These results are worrisome, since show the presence of non-negligible proportions of MRSA strains with high MIC values for ceftaroline and ceftobiprole in a setting where both drugs were never used.

Identification and antibiotic susceptibility of lactobacilli isolated from turkeys

BackgroundThe aim of this study was to identify Lactobacillus isolates derived from turkeys from six Polish farms and to characterize their phenotypic and genotypic antibiotic resistance profiles.ResultsAmong 62 isolates identified by MALDI-TOF mass spectrometry and restriction analysis of 16S rDNA, the dominant species was L. salivarius (35%), followed by L. crispatus (21%), L. ingluviei (14.5%) and L. johnsonii (10%). A high prevalence of resistance to tetracycline (68% resistant isolates), lincomycin (64.5%) and enrofloxacin (60%) among the lactobacilli tested was observed. Fewer than 50% isolates were resistant to ampicillin (47%), erythromycin (45%), streptomycin (31%), chloramphenicol (29%) and gentamicin (10%). As many as 64,5% of the isolates showed multidrug resistance. High MIC values for ampicillin (≥64 μg/ml) were usually accompanied by elevated MICs for cephalosporins (≥16 μg/ml) and high MICs for tiamulin, i.e. ≥32 μg/ml, were noted in most of the turkey lactobacilli (61%). The occurrence of resistance genes was associated with phenotypic resistance, with the exception of five phenotypically susceptible isolates that contained the tetM, tetL, ermC, ermB or cat genes. The most frequently identified were ermB (45% isolates), tetL (40%), tetW (37%) and tetM (29%), and the occurrence of lnuA (18%), cat (10%), ermC (6%), ant(6)-Ia (5%) and aadE (5%) was less frequent. The mechanism of ampicillin resistance has not been elucidated, but the results of nitrocefin test confirmed that it is not involved in the production of beta-lactamases.ConclusionsThe high rate of antibiotic resistance observed in this study indicates the need to implement the principles of rational use of antibiotics in poultry. The presence of transmissible resistant genes in lactobacilli may contribute to the development of antibiotic resistant pathogenic strains that pose a threat to both poultry and consumers. The results of these studies may be useful for committees providing guidance on antibiotic susceptibility of microorganisms in order to revise and supplement current microbiological cut-offs values within the genus Lactobacillus.

English

Tuberculosis is a contagious airborne infection that mostly affects the lungs. The causative agent of tuberculosis in human is Mycobacterium tuberculosis. The emergence and dissemination of M. tuberculosis isolates that are resistant to multiple antimicrobial drugs represent a growing public health threat. Fractions from Alafia barteri, Chasmanthera dependence, Chrysophyllum albidum, Emilia coccinea, Mezoneuron benthamianum, Phyllanthus muellerianus, Secamoni afzeli, Senna alata, Xylopia aethiopica and Acalypha fimbriata were screened for activity against drug susceptible M. tuberculosis H37Rv and the local isolates using proportion and nitrate reduction methods. The organisms used were M. tuberculosis H37Rv strain and the local isolates from TB patients. The standard antitubercular drugs used were isoniazid and rifampicin. No fractions from A. barterii, C. dependens, E. coccinea, S. afzeli, S. alata and X. aethiopica showed sensitivity against the M. tuberculosis strains. The hexane fraction of C. albidum, butanol fraction of M. benthamianum, ethyl acetate fraction of P. muellerianus and ethyl acetate fraction of A. fimbriata showed sensitivity with minimum inhibition concentration of 0.5 mg/ml. The ethylacetate and hexane fractions of M. benthamianum together with hexane fraction of P. muellerianus showed sensitivity with MIC value of 1.25 mg/ml. The highest MIC value of 2.5 mg/ml was obtained from hexane fraction of A. fimbriata. Thus, C. albidum, M. benthamianum, P. muellerianus and A. fimbriata possessed antimycobacterium tuberculosis activity and further research work would be required to assess possible antitubercular agents present in the four medicinal plants. Key words: Tuberculosis, anti-mycobacterium, fractions, sensitivity and inhibition.

Antifungal activity of 3-acetylbenzamide produced by actinomycete WA23-4-4 from the intestinal tract of Periplaneta americana.

Actinomycetes are well-known for producing numerous bioactive secondary metabolites. In this study, primary screening by antifungal activity assay found one actinomycete strain WA23-4-4 isolated from the intestinal tract of Periplaneta americana that exhibited broad spectrum antifungal activity. 16S rDNA gene analysis of strain WA23-4-4 revealed close similarity to Streptomyces nogalater (AB045886) with 86.6% sequence similarity. Strain WA23-4-4 was considered as a novel Streptomyces and the 16s rDNA sequence has been submitted to GenBank (accession no. KX291006). The maximum antifungal activity of WA23-4-4 was achieved when culture conditions were optimized to pH 8.0, with 12% inoculum concentration and 210 ml ISP2 medium, which remained stable between the 5th and the 9th day. 3-Acetyl benzoyl amide was isolated by ethyl acetate extraction of WA23-4-4 fermentation broth, and its molecular formula was determined as C9H9NO2 based on MS, IR, 1H, and 13C NMR analyses. The compound showed significant antifungal activity against Candida albicans ATCC 10231 (MIC: 31.25 μg/ml) and Aspergillus niger ATCC 16404 (MIC: 31.25 μg/ml). However, the compound had higher MIC values against Trichophyton rubrum ATCC 60836 (MIC: 500 μg/ml) and Aspergillus fumigatus ATCC 96918 (MIC: 1,000 μg/ml). SEM analysis showed damage to the cell membrane of Candida albicans ATCC 10231 and to the mycelium of Aspergillus niger ATCC 16404 after being treatment with 3-acetyl benzoyl amide. In conclusion, this is the first time that 3-acetyl benzoyl amide has been identified from an actinomycete and this compound exhibited antifungal activity against Candida albicans ATCC 10231 and Aspergillus niger ATCC 16404.

Pharmacokinetics of florfenicol and its metabolite florfenicol amine in crucian carp (Carassius auratus) at three temperatures after one single intramuscular injection

The pharmacokinetic profiles of florfenicol (FF) or florfenicol amine (FFA) in crucian carp were compared at different water temperatures after single intramuscular administration of FF at 10mg/kg bodyweight. The concentrations of FF and FFA were determined by a high-performance liquid chromatography method, and then, the concentration versus time data were subjected to compartmental analysis using a one-compartment open model. At the water temperatures of 10, 20, and 25°C, the peak concentrations (Cmax s) of FF were 2.28, 2.29, and 2.34μg/ml, respectively, while those of FFA were 0.42, 0.71, and 0.82μg/ml, respectively. And the absorption half-life (t1/2ka ) of FF was 0.21, 0.19, and 0.21hr, while the elimination half-life (t1/2kel ) was 31.66, 24.77, and 21.48hr, respectively. For FFA, the formation half-life (t1/2kf ) was 3.85, 8.97, and 12.43hr, while the t1/2kel was 58.34, 30.27, and 21.22hr, respectively. The results presented here demonstrated that the water temperature had effects on the elimination of both FF and FFA and the formation of FFA. Based on the T>MIC values calculated here, to treat the infections of bacterial with MIC value≤0.5μg/ml, FF intramuscularly given at 10mg/kg bodyweight with a 72-hr interval is sufficient at the water temperature of 10°C, while the intervals of 60 and 48hr were needed at 20 and 25°C, respectively. But to treat bacterial with higher MIC values, more FF or FF at 10mg/kg BW but with shorter intervals should be intramuscularly given to the infected fish.

Distribution of biocide resistant genes and biocides susceptibility in multidrug-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii - A first report from the Kingdom of Saudi Arabia.

The aim of this study was to determine the frequency of biocide resistant genes, qacA, qacE and cepA in multidrug resistant (MDR) bacteria: Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii and to correlate the presence or absence of resistant genes with biocides susceptibility. The study included 44 MDR K. pneumoniae, P. aeruginosa and A. baumannii microorganisms. The bacteria were screened for the presence of biocide resistant genes by the polymerase chain reaction (PCR) method. The test organisms were isolated from various clinical specimens in the Qassim region, Saudi Arabia. The in vitro susceptibility tests of the three biocides (benzalkonium chloride, cetrimide and chlorhexidine gluconate) were studied against the test isolates by broth microdilution method following Clinical and Laboratory Standards Institute guidelines. With the distribution of biocide resistant genes in K. pneumoniae, all 9 isolates (100%) possessed cepA; 4 (44.4%) and 1 (11.1%) isolate contained qacA and qacE genes respectively. Among 24 isolates of A. baumannii tested, cepA, qacA and qacE genes were found in 54.2%, 16.7% and 33.3% of isolates respectively. Among 11 P. aeruginosa isolates, 63.6% contained cepA gene, 18.2% contained qacE genes, and none of the isolates harboured qacA gene. There was no significant correlation between presence or absence of biocide resistant genes and high MIC values of the test isolates (p≥0.2). Our observations imply that there was no significant correlation between presence or absence of biocide resistant genes and MICs observed in MDR K. pneumoniae, P. aeruginosa and A. baumannii. Further studies are required to find to confirm the trend of reduced susceptibility to biocides of problematic nosocomial pathogens.

Role of Disputed Mutations in the rpoB Gene in Interpretation of Automated Liquid MGIT Culture Results for Rifampin Susceptibility Testing of Mycobacterium tuberculosis.

Low-level rifampin resistance associated with specific rpoB mutations (referred as "disputed") in Mycobacterium tuberculosis is easily missed by some phenotypic methods. To understand the mechanism by which some mutations are systematically missed by MGIT phenotypic testing, we performed an in silico analysis of their effect on the structural interaction between the RpoB protein and rifampin. We also characterized 24 representative clinical isolates by determining MICs on 7H10 agar and testing them by an extended MGIT protocol. We analyzed 2,097 line probe assays, and 156 (7.4%) cases showed a hybridization pattern referred to here as "no wild type + no mutation." Isolates harboring "disputed" mutations (L430P, D435Y, H445C/L/N/S, and L452P) tested susceptible in MGIT, with prevalence ranging from 15 to 57% (overall, 16 out of 55 isolates [29%]). Our in silico analysis did not highlight any difference between "disputed" and "undisputed" substitutions, indicating that all rpoB missense mutations affect the rifampin binding site. MIC testing showed that "undisputed" mutations are associated with higher MIC values (≥20 mg/liter) compared to "disputed" mutations (4 to >20 mg/liter). Whereas "undisputed" mutations didn't show any delay (Δ) in time to positivity of the test tube compared to the control tube on extended MGIT protocol, "disputed" mutations showed a mean Δ of 7.2 days (95% confidence interval [CI], 4.2 to 10.2 days; P < 0.05), providing evidence that mutations conferring low-level resistance are associated with a delay in growth on MGIT. Considering the proved relevance of L430P, D435Y, H445C/L/N, and L452P mutations in determining clinical resistance, genotypic drug susceptibility testing (DST) should be used to replace phenotypic results (MGIT) when such mutations are found.

Effect of amino acid substitution in New Delhi metallo-β-lactamase on carbapenem susceptibility.

The aim of this work was investigation of clinically important amino acid substitutions of NDM-1 variants. A blaNDM-1 gene was cloned into expression vector pET100/D-TOPO. The sequence of NDM-1 variants with substituted amino acids was determined by ClustalW program. A pET100/D-TOPO + blaNDM-1 was used to generate the alanine mutations at different positions, such as NDM-2 (P28A), NDM-3 (D95A), NDM-4 (M154A), NDM-5 (V88A), NDM-7 (D130A), and NDM-9 (E152A). The mutant variants were transformed into Escherichia coli DH5α. Changes in the activities of alanine mutation variants were determined by E-test. All samples had 32μg/ml MIC values against ampicillin. The 28th amino acid mutation sample had the highest MIC value against ceftazidime, whereas decreased MIC value for piperacillin. It was observed that the resistance to imipenem was increased in mutant variants D95A, M154A, D130A, and E152A, comparing with P28A and V88A. It was found that NDM-1 has 0.64μg/ml and the 130th amino acid mutation sample has 0.75μg/ml meropenem MIC value.