Shigellosis and Development of Multiple Antimicrobial Resistance Mechanisms of Shigella spp.

Shigellosis is a serious public health issue. Millions of people suffer from this deadly food and water borne disease each year. The main manifestations of affected persons are bloody diarrhea with excessive dehydration. The causative agent of this disease is the bacteria Shigella spp. which has four serogroups. Though Shigella flexneri and Shigella dysenteriae are the dominant serogroups in developing countries, reports of other serogroups, namely Shigella boydii and Shigella sonnei, in the food contaminations are available. There are seasonal variations of Shigella infection throughout the world. In Asian subcontinent, monsoon and post monsoon times are the ideal for infection. The transmission of the bacteria in human is usually caused by feco-oral route or by contaminated food and water. There are several groups of antibiotics like foscomycin, macrolide, amiglycoside, tetracycline etc. which were used before. But they are now become useless as Shigella spp. is getting resistant against those drugs. The quinolone groups of antibiotics like ciprofloxacin, ofloxacin, norflxacin, ceftriaxone etc. are the important drugs for the cure of the disease shigellosis but prevalence of drug resistant strains of Shigella spp. against those drugs are a great concern nowadays. The occurrence of plasmid mediated quinolone resistance genes (PMQR), efflux pump proteins and effective mutations at drug binding region of gyrA etc. are the major mechanisms for the development of drug resistance.

Effect of the Histone Methyltransferase Specific Probe BRD4770 on Metabolic Profiling of the Endophytic Fungus Diaporthe longicolla

The endophytic fungus Diaporthe longicolla was isolated from the stem of Saraca asoca (Roxb.) Willd., commonly known as Ashok plant in India and Sri Lanka. Since no reports are available regarding epigenetic modulations by BRD4770 in microbial entities, D. longicolla was treated with different concentrations of BRD4770 for this purpose and evaluated for its antioxidant and antibacterial potential against five human pathogenic bacteria, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Shigella boydii, Klebsiella pneumoniae, and Escherichia coli. The crude extract obtained from cultures treated with 100 nM concentration of BRD4770 showed increased antioxidant activity and inhibition zone against S. aureus and MRSA, compared to the non-treated control. The composition of the non-treated and treated crude extract was analyzed, and induced compounds were identified with the help of Gas chromatography–mass spectrometry (GC-MS) and LC-ESI-MS/MS. LC-ESI-MS/MS analysis showed that berberine (antibacterial)-, caffeine-, and theobromine (antioxidant)-like compounds were induced in the BRD4770-treated crude extract. The presence of particular absorbance at a wavelength of 346.5 nm for berberine, 259.4 nm for caffeine, and 278.4 nm for theobromine in the reverse-phase high-performance liquid chromatography (HPLC) analysis of both BRD4770-treated crude metabolites and standard solution of the above compounds strongly supported the increased antibacterial and antioxidant activities that may be due to inducing the alterations in bioactivities of the BRD4770-treated culture.

In vitro bioassay of antibacterial and antifungal activity studies of actinomycetes from soda lakes of Ethiopia

The ever-increasing spectrum of microbial disease and emergence of life-threatening antibiotic-resistant pathogens necessitates more intensive search for microbial antagonistic agents from diverse symbionts and habitats. Based on these hypotheses the current study was initiated to investigate in vitro antibacterial and antifungal activities of both crude and pure compounds isolated from potential actinomycete isolates recovered from soda lakes of Ethiopia. Two soda lakes, Arenguade/Hora Hadho/ and Chitu were included in this study. A total of fifteen 12 water samples were collected and actinomycete cultures were isolated by serial dilution plating technique on various media. Morphological and biochemical characterization of selected isolates was done as described in the International Streptomyces Project Guidelines. Minimum inhibitory concentrations of the crude extract was determined for fungus using the protocol described in National Committee for Clinical Laboratory Standards and for the bacteria disc diffusion assay method as described in the Clinical and Laboratory Standards Institution. Ethanol extracts obtained from Solid State Fermentation a total of 36 isolates of actinomycetes were subjected to primary screening and tested for activity against the bacterial and fungal reference strain. Accordingly, the extracts from 10 isolates that were most active in the primary screen were 6 (16.66%) from Lake Chitu that were inhibited the growth of Gram-positive bacteria and fungal strain; 4 (11.11%) from Lake Arenguade that were inhibited Gram-negative bacteria and fungal. From evaluated the antibacterial and antifungal potential of two soda lakes water-derived actinomycetes; the best ones in terms of activity spectra were actinomycetes species isolated from Lake Chitu. Antibacterial and antifungal metabolite production was detected from isolates of Lake Chitu with maximum zone of inhibition within 5–6 days of incubation against Candida albicans ATCC 62376, Aspergillus niger, C. neoformans, F. oxysporum f. sp. melonis (CECT 20474), and Shigella boydii (clinical). All test microorganisms, except Staphylococcus aureus ATCC25923, E. coli ATCC 25922, and S. aureus (clinical isolate) were sensitive to the culture filtrate starting from 8–12 days of incubation. In terms of the effectiveness of the antibacterial activity, the antibacterial metabolite produced from different carbon sources were more effective on S. aureus (clinical isolate), A. niger, C. neoformans, S. aureus ATCC25923, Fusarium oxysporum f. sp. melonis (CECT 20474), Shigella boydii (clinical isolate) respectively. However, the most resistant test isolates with least activity was detected against Candida albicans ATCC 62376 and E. coli ATCC 25922.

Bioactive potential of Aphanamixis polystachya seed extracts

Aphanamixis polystachy seed extracts were examined for their in-vitro biological activities. The n-hexane and methanol extract showed significant phenolic content of 12.0 and 11.7 mg GAE/g, respectively. Antioxidant activity was exhibited by the methanol extract (IC50: 22.34 μg/mL) and moderate activity was shown by the n-hexane extract (IC50: 63.05 μg/ml) compared to BHT (tert-butyl-1- hydroxy toluene, IC50: 14.01 μg/ml) though both extracts caused moderate clot lysis of 18.84% and 23.49% compared to the positive control Streptokinase (65.16%). The n-hexane and methanol extract had shown 18.2% and 32.2% inhibition of hypnotic solution induced haemolysis respectively, while the n-hexane extract had almost no activity (2.21%) and methanol extract showed very high (70.17%) inhibition of heat induced haemolysis compared to acetyl salicylic acid (71.9%). Sensible and substantial cytotoxicity was exhibited by the n-hexane (LC50:13.45 μg/ml) and methanol extracts (LC50:1.61 μg/ml), respectively compared to vincristine sulfate (LC50: 0.45 μg/ml). The n-hexane extract showed no antimicrobial activity against the tested micro-organisms but the methanol extract showed a strong zone of inhibition (25 mm) against Staphylococcus aureus and a moderate zone of inhibition (10mm) against Shigella boydii. Both the extracts exhibited almost zero haemolysis. Bangladesh J. Sci. Ind. Res.56(2), 75-86, 2021

Phytochemical constituent and antimicrobial properties of guava extracts of east Hararghe of Oromia, Ethiopia

Background There is a need for the screening more effective, affordable and readily available antimicrobial substances from local medicinal plants or herbs as the pathogenic bacteria are developing the resistance to common antibiotics. Guava (Psidium guajava L.) has antimicrobial activities and it is easily accessible to local populace in tropical region. Antimicrobial properties of guava extracts are attributed to the presence of different phytochemical constituents. The fact that phytochemicals’ constituents vary as a result of geographical locations and literatures about Ethiopian guava with respect to phytochemicals’ composition and content, and antimicrobial activities are hardly available, there is a need to analyze phytochemicals and antimicrobial properties of the Ethiopian guava from Oromia Regional State, Babile and Gursum Districts against Salmonella Typhi, Shigella boydii, Staphylococcus aureus and Enterococcus faecalis. Methods Extraction was done by maceration. Qualitative analysis of phytochemicals was carried out using standard protocol and quantitative phytochemical determination was conducted using spectrophotometric and gravimetric methods. Antimicrobial activities were determined by disc diffusion and broth dilution method. Results Qualitative phytochemical analysis revealed the presence of alkaloids, saponin, steroids and tannin, but the absence of flavonoid and phlobatannin in all Babile and Gursum leaf and bark extracts. Gravimetric measurement showed the highest terpenoid content of 105.00 ± 8.66 mg extract/g of powder in Gursum leaf extract. Similarly, spectrophotometric measurement showed the highest total phenol content of 0.205 ± 0.01 mg/g of the extracts as Tannic Acid Equivalent in Gursum leaf extract. Antimicrobial activity tests revealed that Babile leaf extract showed the highest 13.0 ± 6.79 mm zone of inhibition against Shigella boydii compared to that of other guava extracts. Babile leaf extract showed the lowest 2.375 ± 0.177 mg/ml minimum inhibitory concentration against Shigella boydii, while Gursum leaf extract showed the lowest 1.875 ± 0.884 mg/ml MIC against Salmonella Typhi. Phytochemical analysis showed the presence of alkaloids, saponins, steroids and tannins in the all extracts, but the absence of flavonoids and phlobatannins in the all extracts and terpenoids in Babile extracts. The highest content of alkaloid and terpenoid (98.67 ± 14.43, 93.33 ± 8.82 mg extract/g of powder, respectively) were found in Babile leaf and Gursum bark extracts, respectively. Antimicrobial activity tests revealed that Babile leaf extracts showed higher zone of inhibition against all clinical isolates than that of Gursum leaf extracts, but Babile bark extracts showed lower zone of inhibition against all clinical isolates than that of Gursum bark extracts. Babile leaf extracts showed the highest zone of inhibition (13.0 ± 6.79 mm) against S. boydii, and Babile bark extracts showed the lowest Minimum Inhibitory Concentration (1.250 ± 0.001 mg/ml) against S. Typhi. Conclusion Guava extracts from different location could be source of natural antimicrobial agents with different composition and content. In vivo antimicrobial activity, and isolation, identification and synergy of specific active compound that responsible for the antibacterial activity should be evaluated.

Bacterial enteropathogens causing acute diarrhoea in children in a tertiary care hospital, Imphal

Background: Diarrhoeal diseases are responsible for causing 3 million deaths worldwide every year especially among the children and also the commonest cause of morbidity and mortality in developing countries like India. Infective diarrhoea could be either bacterial, viral, parasitic or occasionally a combination of these.Methods: A cross-sectional study was carried out in children below 12 years with acute diarrhoea in theMicrobiology Department, RIMS, Imphal for a period of 2 years. Stool samples were subjected to routine microbiological examination, followed by culture and sensitivity. Data were collected in a predesigned data collection sheet.Results: Majority of the diarrhoeal cases were seen among the age group of 1-3 years (44.3%), predominantly among the male children (66.2%) and mostly in summer. Out of 210 culture positive stool samples, Escherichia coli(83.3%) was the predominant enteropathogen with followed by Shigella spp.(12.9%), Klebsiella spp. (2.9%) and Salmonella spp. (1%). Serotyping revealed thirty five enteropathogenic E. coli, eighteen Shigella flexneri, seven Shigellasonnei, two Shigella boydii and two Salmonella typhimurium. Majority of the isolates showed high resistance to amoxicillin, ampicillin, ciprofloxacin, ofloxacin and cotrimoxazole.Conclusions: Bacterial enteropathogens are an important cause of acute diarrhoea among children. Rehydration therapy remains the initial treatment. Though it is usually self-limiting, empirical and specific antimicrobial therapy can be considered in certain situations. Awareness of improving hygiene and infectious diseases may help reduce the burden of infection.

Distribution of novel Og-types in Shiga toxin-producing Escherichia coli isolated from healthy cattle

Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen. Although most cases of STEC infection in humans are due to O157 and non-O157 serogroups, there are also reports of infection with STEC strains that cannot be serologically classified into any O-serogroup (O-serogroup untypeable, OUT). Recently, it has become clear that even OUT strains can be subclassified based on the diversity of O-antigen biosynthesis gene cluster (O-AGC) sequences. Cattle are thought to be a major reservoir of STEC strains belonging to various serotypes; however, the internal composition of OUT STEC strains in cattle remains unknown. In this study, we screened 366 STEC strains isolated from healthy cattle by using multiplex PCR kits including primers that targeted novel O-AGC types (Og-types) found in OUT E. coli and Shigella strains in previous studies. Interestingly, 94 (25.7%) of these strains could be classified into 13 novel Og-types. Genomic analysis revealed that the results of the in silico serotyping of novel Og-type strains were perfectly consistent with those of the PCR experiment. In addition, it was revealed that a dual Og8+OgSB17-type strain carried two types of O-AGCs from E. coli O8 and Shigella boydii type 17 tandemly inserted at the locus, with both antigens expressed on the cell surface. The results of this comprehensive analysis of cattle-derived STEC strains may help improve our understanding of the strains circulating in the environment. Additionally, the DNA-based serotyping systems used in this study could be used in future epidemiological studies and risk assessments of other STEC strains.

Phytochemical and Biological Studies of Bark Extract of Miliusa velutina (Dunal) Hook. f. & Thomson

The main objective of the current research was phytochemical and biological studies of the stem bark of Miliusa velutina (Dunal) Hook. f. & Thomson (Annonaceae). Four purified compounds i.e., friedelin, lupeol, β- sitosterone and caffeic acid were isolated by repeated chromatographic separation and purification of M. velutina. The compounds were identified by analysis of NMR spectral data. The crude dichloromethane extract of stem bark of M. velutina (DEMV) along with its Kupchan partitionates i.e., petroleum ether (PESF), ethyl acetate (EASF), chloroform (CSF) and aqueous (AQSF) soluble fraction were screened for antioxidant, cytotoxic, thrombolytic and antibacterial activities. During the antioxidant activity assay, the AQSF revealed maximum activity with IC50 value of 71.67 μg/ml. The cytotoxicity of plant samples was determined by brine shrimp lethality bioassay, where the maximum cytotoxic activity has been observed for EASF (LC90 = 9.01 μg/ml). In the thrombolytic activity test, the crude dichloromethane extract demonstrated significant efficacy with 46.27% inhibition of clot lysis. In antibacterial screening, the CSF exhibited noticeable inhibitory activity against Shigella boydii with the zone of inhibition 15 mm compared to the standard ciprofloxacin (zone of inhibition = 47 mm). Dhaka Univ. J. Pharm. Sci. 19(2): 125-131, 2020 (December)

Phytochemical and Biological Activity Studies of Tinospora crispa Stem

Three compounds namely, tinosporol A, 8-methoxy palmatine and callecdysterol C were isolated from the methanol extract of the stem of Tinospora crispa. Biological activities of different partitionates of the parent extract was also evaluated. Antimicrobial screening of different partitionates was carried out against sixteen different microorganisms and only n-hexane fraction exhibited significant zone of inhibition against Staphylococcus aureus (9 mm), Shigella boydii (9 mm), Shigella dysenteriae (9 mm), Candida albicans (10 mm) and Aspergillus niger (10 mm).The crude methanol extract showed the highest general toxicity with LC50 values of 57.14 μg/mL against brine shrimp lethality bioassay.The total antioxidant capacity of aqueous fraction was found to be 61.61 mg as ascorbic acid equivalentper gram of plant extract.The antioxidant activity of DCM fraction revealed the highest activity having IC50 values 54.74 μg/mL. No significant cytotoxicity was observed on both HeLa and Vero cell lines. Dhaka Univ. J. Sci. 68(2): 167-170, 2020 (July)

Genome Sequences of Four Shigella boydii Strains Representative of the Major S. boydii Clades

ABSTRACT There are four bacterial species in the genus Shigella that cause shigellosis or dysentery. Shigella boydii is one of the least studied Shigella species but has been shown to be separated into three phylogenomic clades. Here, we report four complete reference sequences of the S. boydii phylogenomic clades.