Background Actinobacteria are famous for the production of unique secondary metabolites that help in controlling the continuously emerging drug resistance all over the globe. This study aimed at the investigation of an extreme environment the Cholistan desert, located in southern Punjab, Pakistan, for actinobacterial diversity and their activity against methicillin resistant Staphylococcus aureus (MRSA). The Cholistan desert is a sub-tropical and arid ecosystem with harsh environment, limited rainfall and low humidity. The 20 soil and sand samples were collected from different locations in the desert and the actinobacterial strains were selectively isolated. The isolated strains were identified using a polyphasic taxonomic approach including morphological, biochemical, physiological characterization, scanning electron microscopy (SEM) and by 16S rRNA gene sequencing. Results A total of 110 desert actinobacterial strains were recovered, which were found to be belonging to 3 different families of the order Actinomycetales , including the family Streptomycetaceae , family Pseudonocardiaceae and the family Micrococcaceae . The most frequently isolated genus was Streptomyces along with the genera Pseudonocardia and Arthrobacter . The isolated strains exhibited promising antimicrobial activity against methicillin resistant Staphylococcus aureus (MRSA) with zone of inhibition in the range of 9–32 mm in antimicrobial screening assays. The chemical profiling by thin layer chromatography, HPLC-UV/Vis and LC-MS analysis depicted the presence of different structural classes of antibiotics. Conclusion The study revealed that Cholistan desert harbors immense actinobacterial diversity and most of the strains produce structurally diverse bioactive secondary metabolites, which are a promising source of novel antimicrobial drug candidates. Electronic supplementary material The online version of this article (10.1186/s12866-019-1414-x) contains supplementary material, which is available to authorized users.

Purpose: To investigate the actinomycetes from an extreme environment for their inhibitory potential against methicillin-resistant Staphylococcus aureus (MRSA), and the metabolic fingerprinting of the active strains. Methods: A total of 80 actinomycetes strains were recovered from Cholistan desert, Pakistan. The isolated strains were identified by morphological, biochemical and physiological characterization and by 16S rRNA gene sequencing. The antimicrobial activity of the selected actinomycetes strains against MRSA was determined by agar well and disc diffusion assays. All the strains were screened against MRSA for the identification of potent antimicrobial producers. Further, validation of MRSA, strains was carried out using a portion of mec-A gene (533bp) of five strains including A1, A6, A7, A8 and A9, amplified and sequenced. Results: The desert actinomycetes strains exhibited promising antimicrobial activity against MRSA with zone of inhibition of up to 25 mm recorded in agar diffusion and disc diffusion assays. The MRSA strains also showed maximum genetic similarity with methicillin-resistant Staphylococcus aureus in GenBank. Most of the actinobacterial strains exhibited 99 % genetic similarity with the genus Streptomyces, including strains AFD6, AFD12, AFD23, AFD25, and AFD26 while isolate AFD18 has 100 % similarity with a Pseudonocardia, named Saccharothrix xinjiangensis. Conclusion: The results reveal that actinomycetes from the desert ecosystem studied are significant producers of useful antimicrobial agents, and should be explored further for novel drug candidates against MRSA.

Background: The objective of this study was to determine the incidence of MRSA with their antibiotic susceptibility pattern and molecular characterization of these strains. Study Design: Cross sectional study. Setting: Microbiology section of Citilab and Research Centre, Lahore. Period: March 2014 to June 2016. Materials and Methods: Bacterial isolates were retrieved from different specimens of pus/wound, blood and other body fluids. These were characterized using conventional (catalase, DNase, coagulase etc), phenotypic and molecular techniques (oxacillin and cefoxitin susceptibility, 16S rRNA gene sequencing and mec-A gene) methods of identification. Antibiotic sensitivity pattern was also detected by applying standard Kirby Bauer disc diffusion method. Results: Out of all the isolated strains, the frequency of MSSA (methicillin sensitive Staphylococcu saureus) was more than the MRSA and it was found that the male patients were more affected than the female patients. All of the isolates were resistant to cefoxitin and oxacillin while most of them showed positive band of mec-A gene. All of the MRSA isolates showed resistant to penicillin followed by azithromycin, erythromycin, co-trimoxazole and ciprofloxacin, while these strains were sensitive to linezolid and vancomycin, followed by teicoplanin, fosfomycin and fusidic acid. Conclusion: In conclusion, proper diagnosis of MRSA required conventional, phenotypic molecular techniques in our hospital diagnostic settings. This will help in choosing the effective antibiotics combat the infection.

No abstract

No abstract