Comparative evaluation of agar dilution and broth microdilution by commercial and in-house plates for Bacteroides fragilis group: An economical and expeditious approach for resource-limited settings.

OBJECTIVE: To compare the performance of agar dilution and broth microdilution by commercial and in-house prepared plates for the Bacteroides fragilis group. The cost analysis was performed to demonstrate that in-house prepared BMD plates were a suitable alternative to agar dilution given the high cost and low feasibility of incorporating commercial BMD plates in routine, particularly in the tertiary care institutes of many low- and middle-income countries. METHODS: Thirty B. fragilis group isolates were tested against six antibiotics, frequently used as empirical therapy for anaerobic infections including metronidazole, clindamycin, imipenem, piperacillin-tazobactam, cefoxitin, and chloramphenicol. The running consumable expenditure for all methodologies was calculated. RESULTS: The results demonstrated essential and categorical agreement of >90% for all antibiotics except cefoxitin, which showed <90% categorical agreement. No major or very major errors were observed. We observed a high agreement and strong concordance for MIC values between both methods and inter-rate reliability of >0.9 by Cohen's kappa analysis, indicating almost perfect agreement between both methods using either of the plates. In contrast to agar dilution, a 20.5 fold cost reduction was seen in BMD using in-house plates and a 5.8 fold reduction using commercial plates to test a single isolate. However, when testing 30 isolates concurrently the cost significantly increased for commercial BMD plates by 8.4 folds, and only 1.03 fold cost reduction was seen with in-house BMD plates. CONCLUSION: BMD gives comparable results to agar dilution and can be considered a method of choice to test a small number of samples. The technique is an economical option when plates are standardized in-house and could be employed for susceptibility testing of the B. fragilis group.

Comprehensive antimicrobial susceptibility testing of a large collection of clinical strains of Aggregatibacter actinomycetemcomitans does not identify resistance to amoxicillin.

AIM: The present study aims to determine the susceptibility of Aggregatibacter actinomycetemcomitans to amoxicillin by investigating a large collection of oral strains of diverse geographical origin. METHODS: Two hundred and fifty-seven A. actinomycetemcomitans strains were serotyped using a multiplex polymerase chain reaction, and minimal inhibitory concentration (MIC) values of amoxicillin were determined using the agar dilution method (range 0.25-8.0 mg/L). The plates were spot-wise inoculated with approximately 104 colony-forming units, incubated in 5% CO2 at 37 C°, and visually inspected after 24 and 48 hr. A MIC ≤ 2.00 mg/L was categorised as susceptible using EUCAST interpretative criteria for Haemophilus species. RESULTS: Amoxicillin MIC values varied from 0.25 mg/L to 2.00 mg/L, and all tested strains, including strains previously reported as resistant, were susceptible to amoxicillin. The MIC50 was 1.00 mg/L and the MIC90 was 2.00 mg/L. CONCLUSION: Meticulous investigation of strains including isolates previously reported as resistant could not confirm the emergence of resistance to ß-lactams in A. actinomycetemcomitans. Based on the present in vitro results, amoxicillin can be considered a key oral antimicrobial agent for treatment of A. actinomycetemcomitans.

Evaluation of the SLOMYCO Sensititre(®) panel for testing the antimicrobial susceptibility of Mycobacterium marinum isolates.

BACKGROUND: The agar dilution method is currently considered as the reference method for Mycobacterium marinum drug susceptibility testing (DST). As it is time-consuming, alternative methods, such as the E-test, were evaluated for M. marinum DST, but without success. The SLOMYCO Sensititre(®) panel, recently commercialized by TREK Diagnostic Systems (Cleveland, OH), can be used for DST in slow-growing mycobacteria and for antimicrobial agents recommended by the Clinical and Laboratory Standards Institute (CLSI) for M. marinum DST. The main goal of this work was to evaluate the SLOMYCO Sensititre(®) panel method for DST in M. marinum isolates from human patients and fish relative to the reference agar dilution method. METHODS/RESULTS: The reproducibility of the minimum inhibitory concentration (MIC) determination (±1 log2 dilution) was very good for both the agar dilution method and SLOMYCO Sensititre(®) panel (>90 % agreement). The percentage essential agreement between methods varied, depending on the drug: between 97 and 75 % for ciprofloxacin, moxifloxacin, linezolid, isoniazid, clarithromycin, amikacin, rifabutin and rifampin, 74 % for trimethoprim, 72 % for doxycycline, 70 % for sulfamethoxazole, 59 % for streptomycin, 33 % for ethambutol and only 2.2 % for ethionamide. When the agar dilution and SLOMYCO Sensititre(®) panel results were converted into interpretive criteria, the category agreement was 100 % for amikacin, ciprofloxacin, clarithromycin, moxifloxacin, rifabutin, sulfamethoxazole and trimethoprim, 98 % for ethambutol and 96 % for rifampin and no agreement for doxycycline. CONCLUSIONS: The SLOMYCO Sensititre(®) panel method could provide a potential alternative to the reference agar dilution method, when DST in M. marinum is required, except for doxycycline.

[Antimicrobial susceptibility testing of anaerobic bacteria]. / Estudios de sensibilidad en bacterias anaerobias.

The anaerobic bacteria resistance to antibiotics is increasing, and even has appeared against the most active of those, like metronidazol and carbapenems. This fact forces to make and periodical sensibility tests -at least in the most aggressive and virulent species, in cases that they are isolated from life locations and in the absence of therapeutic response- to check the local sensibility and to establish suitable empiric therapies, all based on multicentric studies carried out in order to this or well to check the activity of new antibiotics. For the laboratory routine, the easiest sensibility method is the E-test/MIC evaluator. Another alternative is microdilution, that's only normalized for Bacteroides. There are preliminary facts that allow the use of disc diffusion method in some species of Bacteroides and Clostridium. For the temporal and multicentric studies, the procedure is dilution in agar plate, the reference method.

In vitro vancomycin susceptibility amongst methicillin resistant Staphylococcus aureus.

BACKGROUND: Vancomycin is drug of choice for treatment of Methicillin Resistant Staphylococcus aureus (MRSA) infections. S. aureus with reduced vancomycin susceptibility (SA-RVS) is on rise. Current guidelines of detection of SA-RVS are based on MIC (Minimum Inhibitory Concentration) by broth or agar dilution methods. Vancomycin MIC by E test (Epsilometer Test) is an alternative. A study was undertaken to know the prevalence of SA-RVS and compare vancomycin MIC by agar dilution and E test. METHODS: A prospective study was undertaken at tertiary care hospital; 232 clinical MRSA isolates were included. Vancomycin MIC was undertaken by agar dilution method and E test. RESULTS: All isolates were sensitive to Linezolid. Two MRSA isolates had vancomycin MIC ≥4 µg/ml; vancomycin MIC50 and MIC90 of MRSA isolates was 0.5 and 0.2 µg/ml respectively by agar dilution method. There was agreement over 93.5% isolates in vancomycin susceptibility by agar dilution and E test. E test had sensitivity and positive predictive value of 1.0 (CI - 0.34-1.0) and 0.5 (CI - 0.17-0.83) respectively compare to agar dilution method. CONCLUSIONS: MRSA isolates continues to be susceptible to vancomycin and Linezolid. E test was found equally suitable in initial screening for vancomycin susceptibility. Due to geographic variation in prevalence, there is need of ongoing surveillance of SA-RVC.

Evaluation of Neisseria gonorrhoeae Isolates Susceptibility to Antibiotics in Zhejiang Province Since 2007.

Objective: This study aimed to assess the drug susceptibility of clinical isolates of Neisseria gonorrhoeae to spectinomycin, ceftriaxone and azithromycin. Moreover, the temporal trends in the minimum inhibitory concentration (MIC) of five antibiotics from Zhejiang, China, are also in the scope of this study. Methods: A total of 1710 gonococcal clinical strains were collected between 2007 and 2021 from health-care institutions in Zhejiang. The MICs of ceftriaxone, azithromycin, spectinomycin, penicillin and ciprofloxacin were assessed by agar dilution method on 1710 Neisseria gonorrhoeae isolates. Count data were expressed as strains and rates, and MICs distribution was elucidated using descriptive statistics. Results: The total resistance rates of gonococci to azithromycin, spectinomycin, penicillin and ciprofloxacin in this study were 19.3%, 0.3%, 75.4% and 99.7%, respectively. Conclusion: The in vitro results showed a high prevalence of resistance to ciprofloxacin and penicillin. Azithromycin resistance rate has exceeded 5%, suggested a high prevalence of resistance. Ceftriaxone and spectinomycin are suggested based on this study for the treatment of Neisseria gonorrhoeae in Zhejiang.

A new micro-agar dilution method to determine the minimum inhibitory concentration of essential oils against microorganisms.

Essential oils (EOs) from plants have attracted wide attention due to their unique flavors and antimicrobial, insecticidal, antioxidant, and anti-inflammatory properties. Antimicrobial activity, the main reason for their widespread use in the food industry, can be determined in vitro by the minimum inhibitory concentration (MIC), which is a key step to evaluate the antimicrobial potential of EOs. However, EOs are lipophilic and insoluble, resulting in the difficulty of accurately measuring their MIC values. In this study, in addition to analyzing the problems in the MIC determination of EOs using the common micro-broth dilution method or the agar method, a new solution called micro-agar dilution method was proposed. As the miniaturization of agar dilution method, this novel method could reduce the dosage of EOs by 16.3 times and medium/PBS by 3.3 times, respectively, and showed better reliability and accuracy than the typical methods. Additionally, the limit of solvents should be evaluated before use if used. Notably, this research could also provide a guide for the MIC determination of other insoluble antibacterial substances.

Reliability of E-Tests and the Phoenix Automated Method in Assessing Susceptibility to IV Fosfomycin-Comparative Studies Relative to the Reference Method.

The agar dilution method (ADM) recommended for IV fosfomycin (IV FOS) is complex and labor-intensive. Keeping in mind the reality of everyday laboratory work, we have evaluated the agreement of IV FOS susceptibility results obtained using the E-test and the Phoenix system with the results obtained using the ADM. MATERIALS AND METHODS: The tests were performed on 860 strains. To evaluate susceptibility to IV FOS, BioMerieux E-tests (bioMerieux, Warsaw, Poland), BD Phoenix panels (BD Phoenix, Sparks, MD, USA), and the ADM were used. Clinical interpretation was performed in accordance with EUCAST Guidance (v12.0, 2021). The significance of the E-test and the Phoenix was analyzed in relation to the ADM by defining categorical agreement (CA), major error (ME), and very major error (VME). Essential agreement (EA) has also been defined for the E-test. A method was considered reliable, in accordance with ISO 20776-2:2007, when CA and EA were above 89.9% and VME was <3%. RESULTS: A categorical agreement of >98.9% was demonstrated between the E-test and the ADM for overall strains and for Echerichia coli, ESBL-producing Enterobacterales, and Staphylococcus aureus, while between the Phoenix and the ADM, a CA of >98.9% was shown only for Escherichia coli, Staphylococcus aureus, and Proteus spp. A very major error rate of <3% was obtained only for Staphylococcus aureus and MBL-producing Pseudomonas evaluated by both the E-test and the Phoenix. An essential agreement of >98.9% between the E-test and the ADM has not been demonstrated for any of the tested groups of strains. The Phoenix yielded more VMEs than the E-test (50 and 46, respectively). The highest VME rate was demonstrated using the Phoenix method for Enterobacter spp. (53.83%). CONCLUSIONS: Both the E-test and the Phoenix have turned out to be reliable in assessing IV FOS susceptibility only for Staphylococcus aureus (CA > 89.9% and VME < 3%). For the remaining tested groups of strains and genera, the simultaneous high CA rate and low VME rate required by ISO were not achieved. Both methods fared particularly badly in detecting strains resistant to IV.

Green synthesis of silver nanoparticles through reduction with Solanum xanthocarpum L. berry extract: characterization, antimicrobial and urease inhibitory activities against Helicobacter pylori.

A green synthesis route for the production of silver nanoparticles using methanol extract from Solanum xanthocarpum berry (SXE) is reported in the present investigation. Silver nanoparticles (AgNps), having a surface plasmon resonance (SPR) band centered at 406 nm, were synthesized by reacting SXE (as capping as well as reducing agent) with AgNO(3) during a 25 min process at 45 °C. The synthesized AgNps were characterized using UV-Visible spectrophotometry, powdered X-ray diffraction, and transmission electron microscopy (TEM). The results showed that the time of reaction, temperature and volume ratio of SXE to AgNO(3) could accelerate the reduction rate of Ag(+) and affect the AgNps size and shape. The nanoparticles were found to be about 10 nm in size, mono-dispersed in nature, and spherical in shape. In vitro anti-Helicobacter pylori activity of synthesized AgNps was tested against 34 clinical isolates and two reference strains of Helicobacter pylori by the agar dilution method and compared with AgNO(3) and four standard drugs, namely amoxicillin (AMX), clarithromycin (CLA), metronidazole (MNZ) and tetracycline (TET), being used in anti-H. pylori therapy. Typical AgNps sample (S1) effectively inhibited the growth of H. pylori, indicating a stronger anti-H. pylori activity than that of AgNO(3) or MNZ, being almost equally potent to TET and less potent than AMX and CLA. AgNps under study were found to be equally efficient against the antibiotic-resistant and antibiotic-susceptible strains of H. pylori. Besides, in the H. pylori urease inhibitory assay, S1 also exhibited a significant inhibition. Lineweaver-Burk plots revealed that the mechanism of inhibition was noncompetitive.

Antimicrobial Susceptibility Profile of Rare Anaerobic Bacteria.

Anaerobes play an important role in clinically relevant infections and resistance is increasing worldwide. We tested 120 rare anaerobic isolates belonging to 16 genera for antimicrobial resistance using the agar dilution method and compared those results to the time-saving E-test method. The susceptibility data for 12 antimicrobial substances (benzylpenicillin, ampicillin/sulbactam, piperacillin/tazobactam, imipenem, meropenem, cefoxitin, metronidazole, moxifloxacin, clindamycin, doxycycline, tigecycline, eravacycline) were collected. Susceptibility testing showed low resistance to ß-lactam/ß-lactamase inhibitor combinations and no resistance to carbapenems and tigecycline. We observed moderate to high rates of resistance to moxifloxacin and clindamycin which differed depending on the methodology used. The essential and categorical agreement was over 90% for ampicillin/sulbactam, meropenem, moxifloxacin, and tigecycline. For metronidazole and clindamycin, the essential agreement was below 90% but the categorical agreement was near or above 90%. Penicillin presented with the lowest categorical agreement of 86.7% and a very high very major error rate of 13.3%. The resistance rates reported in this study are concerning and show the importance of routine susceptibility testing. Further investigations are necessary to determine the reason for high error rates and how to improve susceptibility testing of fastidious anaerobes.

Impact of Alternative Growth Supplements on Antimicrobial Susceptibility Testing of Neisseria gonorrhoeae.

Purpose: The accurate detection of antibiotic susceptibility of Neisseria gonorrhoeae (N. gonorrhoeae) is of great importance for the treatment of patients with gonorrhea as well as to hinder the progress of drug resistance. To promote the application of gonococcal antibiotic susceptibility monitoring in primary hospitals and remote medical institutions, this study evaluated the effect of alternative growth supplements on the antibiotic susceptibility testing of N. gonorrhoeae isolates. Methods: We divided the antimicrobial-containing media into three groups by adding different growth supplements (sterile defibrinated sheep blood, bovine hemoglobin, and Vitox). We tested the antimicrobial susceptibility of 80 N. gonorrhoeae isolates in different groups against eight antibiotics. Nonparametric signed-rank tests were utilized to compare the minimum inhibitory concentration (MIC) results of each group. Taking the MIC results of Vitox group as expected, the essential agreement (EA) and category agreement (CA) of the other two groups were calculated. Results: For the group using sheep blood as growth supplements, the EA values and CA values of each antibiotic were above 90.00% and minor error rates were less than 7.00%. No very major error and major error were observed. For the group using hemoglobin as growth supplements, the EA values of the susceptibility results of zoliflodacin, penicillin, and ceftriaxone were lower than 90.00%. The overall MIC results of using hemoglobin as a growth supplement were higher than those of sheep blood and Vitox in the susceptibility testing of these three antibiotics. Conclusion: Compared with the expected results, sheep blood may be considered for the use as an alternative material for N. gonorrhoeae antibiotics susceptibility surveillance, while hemoglobin may not be suitable for supplement to antimicrobial-containing medium.

Assessment of the Susceptibility of Clinical Gram-Negative and Gram-Positive Bacterial Strains to Fosfomycin and Significance of This Antibiotic in Infection Treatment.

Multidrug resistance of bacteria has prompted intensive development work on new medicines, but also the search for effective options among the oldest antibiotics. Although intravenous fosfomycin (IVFOS) seems to be an interesting proposal, the recommended agar dilution method for susceptibility determination poses a major problem in routine diagnostic testing. As a consequence, there is a lack of comprehensive data on the frequency of isolation of susceptible or resistant strains. This fact triggered the disposition of EUCAST concerning the revision of IVFOS breakpoints (BPs), including withdrawal of BPs for Enterobacterales (excluding E. coli) and coagulase-negative staphylococci. Therefore, the aim of this study was to assess the activity of fosfomycin against numerous clinical strains using recommended methods. Materials and methods: A total of 997 bacterial strains were tested from the following genera: Enterobacterales, Pseudomonas spp., Staphylococcus spp., Acinetobacter spp., and Enterococcus spp., for which there are currently no BPs. The strains were isolated from various clinical materials from patients hospitalized in five hospitals. During the investigation, the recommended agar dilution method was used. Susceptibility to other antibiotics and resistance mechanisms were determined using an automatic method (Phoenix) the disk diffusion method, and E-tests. MIC values of fosfomycin were estimated for all strains and for susceptible and multidrug-resistant (MDR) strains individually. Results: Except for Acinetobacter and Enterococcus, 83% of the strains were susceptible to IVFOS, including the largest percentage of S. aureus and E. coli. Klebsiella spp. turned out to be the least susceptible strains (66%). The highest proportion of susceptibility to fosfomycin was found among strains that were sensitive to other antibiotics (80.9%), and the lowest was found among Gram-negative carbapenemase-producing bacteria (55.6%) and ESBL+ bacteria (61.6%). The MIC evaluation revealed the lowest MIC50 and MIC90 values for S. aureus (0.5 mg/L and 1 mg/L, respectively) and E. coli (4 mg/L and 32 mg/L, respectively). The highest values of MIC50 were found for Acinetobacter spp. (256 mg/L), while the highest values of MIC90 were found for Acinetobacter spp. and Klebsiella spp. (256 mg/L and 512 mg/L, respectively). Conclusions: IVFOS appears to be suitable for the treatment of many infections, including the empirical treatment of polymicrobial infections and those caused by MDR strains, since the sensitivity of the studied strains to this antibiotic in different groups ranged from 66% to as much as 99%. Sensitivity to fosfomycin was also demonstrated by 60% of carbapenem-resistant strains; therefore, IVFOS is one of the few therapeutic options that can be effective against the most resistant Gram-negative rods. In light of the general consultation posted by EUCAST, obtaining data such as IVFOS MIC value distributions may be vital for the decision of implementing fosfomycin into breakpoint tables.

In Vitro Activity of Omadacycline and Five Comparators against Contemporary Ribotypes of Clostridioides difficile in Stockholm, Sweden.

Clostridioides difficile infection represents a growing clinical challenge. The new compound omadacycline is a potential treatment alternative, as many antibiotics have limited activity or are rarely used due to costs and side effects. The activity of omadacycline and five comparators was assessed with agar dilution on a 2015-to-2018 collection of 65 C. difficile isolates from Sweden. Omadacycline demonstrated in vitro activity against the contemporary ribotypes of C. difficile, and further clinical investigation is needed. IMPORTANCE Evaluating the activity of novel antimicrobials like omadacycline is of great interest, as a reliable and efficient antimicrobial treatment for Clostridioides difficile infections is in demand.

Disk-Diffusion Testing Is an Inappropriate Screening Tool for Cephalosporin-Resistant Gonorrhoea Strains in Clinical Practice in China.

PURPOSE: Injectable ceftriaxone and oral cefixime are the last agents effective against Neisseria gonorrhoeae. In vitro antimicrobial-susceptibility testing (AST) is done to identify the most efficacious antibiotic needed to combat the infection in that particular individual. The objective of this study was to evaluate whether Kirby-Bauer (KB) disk-diffusion tests can detect N. gonorrhoeae isolates that have decreased susceptibility to ceftriaxone and cefixime for appropriate clinical management. METHODS: A total of 1,633 consecutive clinical isolates of N. gonorrhoeae were collected from January 1, 2013 to December 31, 2017 from seven dermatology clinics located in five provinces in China. Consistency between KB disk-diffusion tests and the agar-dilution method, as well as sensitivity of the KB test for detecting N. gonorrhoeae isolates with decreased susceptibility to ceftriaxone and cefixime, were determined using 1,306 clinical isolates that had been recovered to complete agar-dilution AST. RESULTS: The prevalence of isolates with decreased susceptibility to ceftriaxone and cefixime was 12.1% (198 of 1,633) and 12.7% (208 of 1,633), respectively, using KB disk-diffusion tests. The prevalence of isolates with decreased susceptibility was 9.9% (129 of 1,306) for ceftriaxone and 9.9% (129 of 1,305) for cefixime using agar-dilution AST. The categorical agreement of these two methods was 80.9% for both ceftriaxone and cefixime. Compared to agar-dilution AST, the sensitivity of the KB test for detecting N. gonorrhoeae isolates with decreased susceptibility was 22.5% (29 of 129) for ceftriaxone and 29.5% (38 of 129) for cefixime, and its specificity 87.3% (1,028 of 1,177) for ceftriaxone and 86.7% (1,018 of 1,176) for cefixime. CONCLUSION: Although KB tests are easy to carry out in clinical practice, their ability to detect cephalosporin-resistant gonorrhoea strains is limited. This method is not an appropriate selection for screening cephalosporin-resistant gonorrhoea strains in clinical practice in China.

Activity of five antimicrobial peptides against periodontal as well as non-periodontal pathogenic strains.

Background: Due to the increasing emergence of multi-resistant bacteria the search for alternative antimicrobial substances is of high interest. Promising agents are antimicrobial peptides which are host defense molecules of the innate immune system in a wide range of different species. Objectives: The aim of this study was to assess the activity of nisin, melittin, lactoferrin, parasin-1 and LL-37 against 35 oral bacteria and Candida albicans employing the gold standard method for anaerobic susceptibility testing. Methods: The activity of the peptides was determined by an agar dilution method under anaerobic and aerobic conditions. The test media contained final peptide concentrations between 0.125 µg/ml and 8 µg/ml (melittin, lactoferrin, parasin-1, LL-37) and between 0.125 µg/ml and 128 µg/ml (nisin). Results: Nisin completely inhibited the growth of Megasphaera sp., Bifidobacterium longum, Parvimonas micra, Actinomyces israelii, Actinomyces naeslundii, Actinomyces odontolyticus, Prevotella intermedia, Streptococcus anginosus, Streptococcus constellatus and Staphylococcus aureus. Melittin and lactoferrin reduced the growth of Megasphaera sp., P. micra, B. longum (melittin) and Selenomonas flueggei (lactoferrin). Parasin-1 and LL-37 showed no activity. Conclusion: AMPs, especially nisin and to a smaller degree lactoferrin, might be promising alternatives to antibiotics because of their antimicrobial activity, high resistance to environmental conditions and partially low costs.

Antimycobacterial screening of selected medicinal plants against Mycobacterium tuberculosis H37Rv using agar dilution method and the microplate resazurin assay.

Background: Tuberculosis (TB), has been serious disease to the global human population causing millions of deaths worldwide. The recent increase in the number of multi-drug resistant clinical isolates of Mycobacterium tuberculosis has created an urgent need for the discovery and development of new anti-TB drugs. Medicinal plants have had a great influence on the daily lives of people living in developing countries, particularly in India. Medicinal plants were selected, and they were evaluated for its anti-TB activity against the pathogenic strain of M. tuberculosis H37Rv. Methods: Eleven medicinal plants were selected on the basis of its literature survey, and three different extracts were prepared. Antimycobacterial activities were screened using two in vitro assays, namely agar dilution assay and microplate resazurin assay against M. tuberculosis H37Rv at different concentrations of prepared extracts. We analyzed minimal inhibition concentrations and percentage of inhibition of the used strain of Mycobacteria. Isoniazid was used as a standard anti-TB drug. Results: The results of this study showed that aqueous extracts four selected medicinal plants Ocimum sanctum, Adhatoda vasica, Leptadenia reticulata, and Cocculus hirsutus having minimum inhibitory concentration at 500 µg/ml, 500 µg/ml, 250 µg/ml, and 250 µg/ml, respectively, and O. sanctum (60.24%), A. vasica (62.89%), L. reticulata (74.26%), and C. hirsutus (81.67%) showed significant anti-TB activity against M. tuberculosis. Conclusion: This study helps society to found new anti-TB agents having better anti-TB activity with lesser or no side effects.

Gentamicin susceptibility of Neisseria gonorrhoeae isolates from 7 provinces in China.

PURPOSE: Gentamicin is a promising antimicrobial for the treatment of gonorrhea. The study aimed to evaluate gentamicin minimum inhibitory concentrations (MICs) of Neisseria gonorrhoeae isolates in China. METHODS: In this study, the agar dilution method was used to determine the MICs of 470 isolates collected in 2016 to four effective antimicrobials (gentamicin, azithromycin, ceftriaxone, and spectinomycin). RESULTS: Gentamicin MICs ranged from 1 to 8 mg/L. No isolate was resistant to gentamicin. Of seven isolates simultaneously resistant to azithromycin and ceftriaxone, 6 isolates demonstrated MICs of 4 mg/L or less to gentamicin. No cross relationships were found between MICs of gentamicinand susceptibility profiles of azithromycin, ceftriaxone, and spectinomycin. CONCLUSION: The in vitro results suggest that gentamicin can be a promising treatment option for gonococcal infections in China. Clinical trials to evaluate the therapeutic efficacy of gentamicin are required.

Comparison of in vitro activities of meropenem productions on Klebsiella pneumoniae isolated from hospitalized patients.

PURPOSE: Antimicrobial activities of meropenem products on Klebsiella pneumoniae isolates were determined. METHODS: 212 non-duplicated Klebsiella pneumoniae isolates were examined for in vitro meropenem susceptibility test by using the following disks, which were made from Meronem (AstraZeneca, UK), Exipenem (Exir, Iran) and Meroxan (DAANA, Iran) powders. MIC50 and MIC90 for meropenem antibiotics were determined. RESULTS: Meronem had good activities against most isolates of Klebsiella pneumoniae, and only a few strains had a rather high MIC. Exipenem and Meroxan showed a similar activity with Meronem. CONCLUSION: Regarding the comparison of two internal generic meropenem products with the external Meronem product have shown that they are equivalents in terms of microbiological activity, as measured using the disk diffusion and MIC. In developing countries, we suggested preparing disks with antibiotic powders that can be an equivalent function in microbiological activity with standard disks. In addition, since it demonstrated significant antimicrobial activity against the Klebsiella pneumoniae. For use of Exipenem and Meroxan in vivo, it would be better to perform additional testing (activity against different species, stability etc.).

Evaluation of antimicrobial activity of the methanol extracts from 8 traditional medicinal plants.

The methanol extract of 12 medicinal plants were evaluated for its antibacterial activity against Gram-positive (5 strains) and Gram-negative bacteria (10 strains) by assay for minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) . The antibacterial activity was determined by an agar dilution method (according to the guidelines of Clinical and Laboratory Standard Institute) . All the compounds (12 extracts) of the 8 medicinal plants (leaf or root) were active against both Gram-negative and Gram-positive bacteria. Gram-negative showed a more potent action than Gram positive bacteria. The MIC concentrations were various ranged from 0.6 µg/ml to 5000 µg/ml. The lowest MIC (0.6 µg/ml) and MBC (1.22 µg/ml) values were obtained with extract on 4 and 3 of the 15 microorganisms tested, respectively.