Anti-Infective Agents - Volume 19, Issue 5, 2021

Streptomyces species are very well known for the production of antimicrobials and enzymes. The objective of this review was to search for the novel Streptomyces isolated in 2018 along with their characteristics and possible antimicrobial properties. The literature search was done according to the PRISMA flow diagram, where 28 research papers were eligible for the review. Data entry and analyses were performed using IBM SPSS Statistics version 25, while the phylogenetic tree was constructed using Geneious Prime Software. The data on general characteristics, biochemical as well as sugar fermentation tests, 16S rRNA gene sequence similarity and DNA-DNA hybridization relatedness were extracted from the research papers and summarized in tables and figures. The biosynthesis gene cluster (BGC) was identified using ‘antibiotics and secondary metabolite analysis shell-antiSMASH’, which showed the possibility of production of new antibiotics, antifungal and antitumor substances from the 28 novel Streptomyces isolated in 2018 which would contribute to the global effort to fight against growing multidrug-resistance.

Background: Antimicrobial resistance is a global threat in the medical society. Extended- Spectrum β-lactamase (ESBL) producing bacteria are increasing worldwide, including Nepal and causing more severe infections because of their continuous mutation and multidrug resistance (MDR) nature. Objective: The objective of this study was to assess Gram-negative bacterial etiology of lower respiratory tract infections (LRTIs) and determine their antibiotic susceptibility pattern with a special focus on MDR, including ESBL production. Methods: A total of 109 sputum specimens were analyzed. The bacterial isolates were identified by standard microbiological procedures, including Analytical Profile Index (API) 20E test panels for Enterobacteriaceae and subjected to antimicrobial susceptibility testing. Screening of ESBL producers among Gram-negative isolates was done by using third-generation cephalosporins (ceftazidime and cefotaxime) and confirmed by the combined disk method as recommended by CLSI (2019). Results: Out of 109 sputum specimens, Gram-negative bacterial etiology was determined in 31(28.4%) cases. The age-wise distribution of LRTIs patients was found to be statistically significant with bacterial incidence (p<0.05). Altogether, 15(46.9%) isolates were multidrug-resistant. ESBL producers were observed only among Klebsiella spp. and Escherichia coli isolates. On the ESBL screening test of 9 isolates (3 of E. coli and 6 of Klebsiella spp.) 5(55.6%) gave a positive result, and only 3(33.3%) of them were further confirmed as ESBL producers. The majority of ESBL producers (66.7%) were Klebsiella spp. Conclusion: The present study revealed that multidrug resistance is prevalent among Gram-negative bacterial pathogens isolated from the patients with lower respiratory tract infections, requiring routine laboratory testing for MDR and ESBL production in clinical isolates for better prophylaxis and reducing the risk of ESBL transmission.

Background: Surgical site infections (SSIs) are the leading nosocomial infections and important cause of morbidity and mortality in surgical patients. Objective: The present study was conducted to investigate the bacterial etiology of SSIs and determine the antibiotic susceptibility patterns of the isolates. Methodology: A cross-sectional study was conducted between July to November 2019 on 105 patients suspected of having SSIs. Wound swabs were collected aseptically using sterile cotton swabs and processed in suitable culture media following the standard operative protocols. Antibiotic susceptibility testing was done by Kirby-Bauer disc diffusion technique following Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: Out of 105 samples collected, 69 showed growth and 77 bacterial isolates were documented altogether. The most frequently isolated bacteria were Staphylococcus aureus 46 (59.74%) followed by E. coli 9 (11.68%). The antimicrobial profile of the isolates revealed that 61.04% were MDR, 25.80% were ESBL producers and 9.68% were carbapenemase producers. Conclusion: High prevalence of antibiotic-resistant bacterial isolates associated with SSIs warrants the need for aseptic techniques during and after surgical procedures and judicious use of antibiotics.

Background: Pain and inflammation are major health problems. The adverse effect of synthetic drugs for the management of painful inflammatory conditions gives a strong motivation for researchers to develop newer drugs with lesser side effects. Mimosa rubicaulis has been traditionally used in rheumatism, fungal infection, wound, fever, etc. Objective: The objective was to evaluate the anti-inflammatory and analgesic activity of ethanolic stem extract of M. rubicaulis in Swiss albino rats. Methods: The stem of M. rubicaulis was collected, subjected to double maceration using ethanol as a solvent. Then, Swiss albino rats (n=72) were taken. An acute toxicity study was conducted using different doses of the plant extract. The anti-inflammatory activity (100 mg/kg, 250 mg/kg) was evaluated using the carrageenan-induced paw edema test, while, analgesic activity (100 mg/kg, 250 mg/kg) was evaluated using a hot plate and tail immersion method. The result was analyzed using a one-way analysis of variance and post hoc analysis with the Tukey test. Results: The acute toxicity study showed that the plant is safe for use in an animal model. The extract showed anti-inflammatory activity by a reduction in paw edema volume by 25% and 48%. Similarly, analgesic activity was shown by an increase in latency of paw licking and tail withdrawal by 41%, and 56% (hot plate method) and 39% and 54% (Tail immersion method), p<0.05. Conclusion: It can be concluded that the ethanolic extract of Mimosa rubicaulis is safe and possesses both anti-inflammatory and analgesic activity.

Background: There are many coronaviruses, which can cause diseases in humans and animals. The new 2019 coronavirus is highly prevalent and contagious, infecting many people in almost all countries of the world. There are many problems involved in the treatment of COVID-19 that must be discussed and examined. Methods: A double-blinded review was conducted on double-blinded studies found on online databases, such as Google Scholar, PubMed, Science Direct, Medline, Highwire, MD Consult, and Scopus, by Internet-based search. Results: Many deaths attributing to COVID-19 are actually caused by mistakes made in the prescription of medications, leading to the deterioration of the conditions of the patients, the most serious of which is the prescription of corticoids. Additionally, it has not been properly researched whether some drugs, such as NSAIDs, are indicated for use in COVID-19 or not. Conclusion: On the other hand, the application of some valuable medicinal herbs, such as peppermint and chamomile, in the treatment of this disease has not received enough attention, despite the fact that they may have valuable and remarkable effects in the treatment of this disease.

Background: Nanotechnology is an emerging research field on nanoparticles. Nanoparticles are 1-100 nm in one dimension and are important in biomedical science, medical chemistry, atomic physics, and most other known fields. They are used because of their small size, orientation, and physical properties. Objectives: This study was designed to synthesize silver nanoparticles (AgNPs) using Azadirachta indica (Neem) leaf extract and evaluate their biomedical application. Methods: An aqueous extract of Azadirachta indica was used to synthesize AgNPs. 1 ml of the extract was added drop by drop to 30-60 ml of a 1mM solution of silver nitrate. The AgNPs were characterized by UV-Visible Spectroscopy, Fourier Transform Infrared Spectroscopy, Dynamic Light Scattering Spectroscopy, X-ray Diffraction, Transmission Electron Microscopy, and antibacterial activity studies. The biological synthesis of AgNPs was performed using the aqueous solution of Azadirachta indica leaf extract and AgNO3. A fixed ratio of plant extract to metal ion was used to prepare AgNPs and the formation of the nanoparticles was confirmed through the color change. The nanoparticles were characterized by UV-vis spectrophotometer, FTIR, DLS, XRD and TEM, and were found to range in size from 30-60 nm. Results: The biosynthesized AgNPs had a bactericidal effect against the antibiotic resistant pathogenic microorganisms Bacillus subtilis, Pseudomonas aeruginosa, and Bacillus cereus. Conclusion: Silver nanoparticles were synthesized from Azadirachta indica leaf extract and can be used as a therapeutic candidate for biomedical applications.

Introduction: Today, people around the world have resorted to herbal medicine, due to the increase in antibiotic resistance and the side effects of synthetic drugs. Methods: Our research focused on the in vivo antifungal activity of three ointments formulated on the basis of methanolic extract of Citrus aurantium peel, ethanolic extract of the aerial part of Artemisia herba alba asso, and essential oil of Artemisia herba alba asso. Wistar rats were made immunosuppressed by Dexamethazone and Tetracycline. Three strains of Candida albicans, S1, S2 and S3 were inoculated. The fungal load of the area tested, the weight of the rats, as well as the macroscopic and microscopic appearance of the skins, were determined. Results: Cutaneous candidiasis was manifested as red, thick, scabbed lesions, mostly located on the infected area of t he animals. Microscopic observation of histological skin sections of animals infected and treated with the ointments, P1, P2 and P3 showed a well-preserved architecture of the skin. Erythema, edema, ulceration, erosion were seen in the skin of animals receiving placebo or Nystatin. The P3 ointment exerted a very powerful antifungal effect against especially the strain S1 compared to the other ointments (log 3.07±0.006 CFU/ml). The weight was regained significantly in the groups of animals receiving the ointments, and regression of growth was observed in the untreated animals and those treated by Nystatin and placebo. Conclusion: The EAH and MCP ointment and the essential oil of Artemisia developed, allowed to retain their significant antifungal activity against Candida.

Background: Mangroves are globally known for their ecological importance and are found to be extensively used in traditional medicine. Avicennia marina, commonly known as grey mangroves, exhibit strong antimicrobial properties and are also considered to be a promising drug candidate in neutralizing pathogens. Objective: In our present study, the leaf extract from Avicennia marina was isolated using organic solvents of ascensive polarity to evaluate binding and abrasive properties in Escherichia coli K12 DNA. Methods: Samples of the pulverized leaves were used for sequential extraction using ethyl acetate, chloroform and acetone. The minimum inhibitory concentration of isolates from ethyl acetate, chloroform, and acetone were quantified to be 0.125 gL^-1, 0.0625 gL^-1, and 0.125 gL^-1, respectively. These values were further utilized to calculate the binding constant between Escherichia coli DNA and isolates. In addition, the mutagenicity of the isolates was assessed using Ames test in which the Escherichia coli K12 (strain AB1157) bacteria was cultured in minimal glucose media supplemented with isolates for assessing their DNA modifying ability. Further, DNA abrasion potential was assessed for all the isolates using Comet assay. Results: Results of Ames test showed that the isolates have DNA modifying ability, whereas the Comet assay demonstrated that isolates have not exhibited DNA degrading potential. Conclusion: In conclusion, the mechanism by which the isolates degrade the bacterial cell must be contrary to its DNA degrading potential. Experiments paved the way for further quantification and examination using bioinformatics tools to find the best drug candidate and run clinical trials.

Background: Nanotechnology brings a massive revolution in the domain of medical biotechnology. Plants possess thousands of antimicrobial compounds; these compounds can be extracted and utilized in the production of medicines. Objective: The aim of this research is to design an economical method for the formation of nanoparticles from plants and explore their antibacterial activity. Methods: In the present study, we used the plants Aloe barbadensis, Azadirachta indica, Carica papaya, Mentha arvensis and Catharanthus roseus. Ethanolic, methanolic and aqueous extracts of the above mentioned plants were used to prepare silver nanoparticles. Antimicrobial activities of the nanoparticles of extracts were determined against pathogenic strains of bacteria. Results: Results showed that silver nanoparticles are formed from the ethanolic and methanolic extracts of Azadirachta indica, Carica papaya, Mentha arvensis and Catharanthus roseus and from the aqueous extracts of Aloe barbadensis and Mentha arvensis. It was observed that nanonoparticles of ethanolic extracts of Azadirachta indica, Carica papaya, Mentha arvensis and Catharanthus roseus exhibited the highest antibacterial activity against Pseudomonas specie, E.coli, Pseudomonas specie and S.typhi, respectively. On the other hand, the nanoparticles of methanolic extracts of Carica papaya, Mentha arvensis and Catharanthus roseus showed the highest inhibition against E.coli, whereas, maximum zone of inhibition of Pseudomonas was observed by the action of methanolic extract of Azadirachta indica. It is also found that nanoparticles of the aqueous extracts of Aloe barbadensis and Mentha arvensis inhibited the pathogenic strains and showed maximum activity against Pseudomonas and E.coli, respectively. Conclusion: The above results indicate that the nanoparticles formed from the extracts of the tested plants have high antimicrobial potential and could be utilized in the preparation of medicines to treat various disorders.

Background: Our goal was to compare the in vitro activities of ceftazidime/avibactam (CZA) to those observed in response to other drugs used to treat carbapenem-resistant Enterobacteriaceae (CRE). Methods: Bacterial isolates collected from intensive care unit patients with hospital-acquired infections were identified using the VITEK 2TMCompact 15. Susceptibility testing for Escherichia coli and Klebsiella spp. was performed using Kirby- Bauer disk diffusion and the VITEK2 system. Minimum inhibitory concentration (MIC) E-test strips were used to examine susceptibility to fosfomycin, colistin, and CZA. Detection of carbapenemase in isolates of Enterobacteriaceae was performed using the modified carbapenem inactivation method (mCIM) and multiplex polymerase chain reaction. Results: A full 62.5% of the Enterobacteriaceae isolates were CRE. The sensitivity and specificity of mCIM were 98.3% and 100%, respectively, with positive predictive and negative predictive values and accuracy at 100%, 97.3%, and 98.96%, respectively. The most prevalent of the carbapenemase genes was blaKPC which was detected in 46.7% of all isolates and in 83.3% of those identified as Klebsiella pneumoniae. CRE were most sensitive to colistin (96.7%), CZA (80%) and tigecycline (71.7%) (p<0.001). The MIC50 for CZA (≤0.016 μg/mL) was the lowest of all the drugs evaluated, followed by colistin (1 μg/mL) and tigecycline (2 μg/mL). All metallo-ß-lactamase-negative isolates were sensitive to CZA. Conclusions: mCIM is sensitive, specific, inexpensive and easy to perform; as such, it an ideal method for identification of carbapenem-resistant strains. Our results suggest that CZA may be a good choice for treating infections with CRE if therapeutic options are limited.