The spread of mupirocin-resistant Staphylococcus aureus strains in hospitals and communities is a universal challenge. Limited data is available on the genetic features of high-level mupirocin resistant- (HLMUPR-) S. aureus isolates in Tehran. In the present research, we investigated 48 high-level mupirocin resistance S. aureus by antimicrobial activity, virulence analysis, biofilm formation, multilocus sequence typing (MLST), and staphylocoagulase (SC) typing. All the HLMUPR strains were positive for mupA gene. The frequency of multidrug resistance was 97.9%. Twenty-one (43.8%) were toxinogenic with 14 producing pvl (29.2%), 5 tst (10.4%), and two eta (4.2%). Among the HLMUPR isolates, biofilm production was detected in 45 (89.6%) isolates with complete dominance clfB, clfA genes, and a noticeably high frequency fnbA (95.8%), followed by fnbB (93.8%), eno and icaD (each 83.3%), sdrC (81.3%), ebps (79.2%), icaA (75%), sdrD (66.7%), fib (60.4%), sdrE (50%), cna (41.7%), and bap (4.2%). Coagulase typing distinguished isolates into four genotypic patterns including III (50%), II (27.1%), and type IVa (22.9%). A total of three clonal complexes (CCs) and 4 sequence types (STs) including CC/ST22 as the most prevalent (52.1%), CC8/ST239 (20.8%), CC/ST8 (16.7%), and CC/ST5 (10.4%) were identified in current work. According to our analysis, nonbiofilm producer isolates belonged to CC8/ST239 (6.3%) and CC/ST8 (4.2%). Fusidic acid-resistant isolates belonged to CC/ST45 (
) and CC8/ST239 (
). Observations highlighted the circulation of the CC/ST22 HLMUPR S. aureus strains with strong biofilm-production ability in our hospitals, indicating the possibility of transmission of this type between community and hospital.
This paper investigates 71 isolates of two genera of entomopathogens, Metarhizium and Beauveria, and a biostimulative genus Trichoderma, for their ability to infect yellow mealworms (Tenebrio molitor) and to stimulate maize (Zea mays) growth. Fungal origin, host, and isolation methods were taken into account in virulence analysis as well. Isolates Metarhizium brunneum (1154) and Beauveria bassiana (2121) showed the highest mortality (100%) against T. molitor. High virulence seems to be associated with fungi isolated from wild adult mycosed insects, meadow habitats, and Lepidopteran hosts, but due to uneven sample distribution, we cannot draw firm conclusions. Trichoderma atroviride (2882) and Trichoderma gamsii (2883) increased shoot length, three Metarhizium robertsii isolates (2691, 2693, and 2688) increased root length and two M. robertsii isolates (2146 and 2794) increased plant dry weight. Considering both criteria, the isolate M. robertsii (2693) was the best as it caused the death of 73% T. molitor larvae and also significantly increased maize root length by 24.4%. The results warrant further studies with this isolate in a tri-trophic system.
The zoonotic disease leptospirosis is caused by pathogenic species of the genus Leptospira. With the advancement of studies in leptospirosis, several new species are being reported. It has always been a query, whether Leptospira species, serovars, and strains isolated from different geographical locations contribute to the difference in the disease presentations and severity. In an epidemiological surveillance study performed in Malaysia, we isolated seven novel intermediate and saprophytic species (Leptospira semungkisensis, Leptospira fletcheri, Leptospira langatensis, Leptospira selangorensis, Leptospira jelokensis, Leptospira perdikensis, Leptospira congkakensis) from environments and three pathogenic species from rodents (Leptospira borgpetersenii strain HP364, Leptospira weilii strain SC295, Leptospira interrogans strain HP358) trapped in human leptospirosis outbreak premises. To evaluate the pathogenic potential of these isolates, we performed an in vivo and in silico virulence analysis. Environmental isolates and strain HP364 did not induce any clinical manifestations in hamsters. Strain SC295 caused inactivity and weight loss with histopathological changes in kidneys, however, all hamsters survived until the end of the experiment. Strain HP358 showed a high virulent phenotype as all infected hamsters died or were moribund within 7 days postinfection. Lungs, liver, and kidneys showed pathological changes with hemorrhage as the main presentation. In silico analysis elucidated the genome size of strain HP358 to be larger than strains HP364 and SC295 and containing virulence genes reported in Leptospira species and a high number of specific putative virulence factors. In conclusion, L. interrogans strain HP358 was highly pathogenic with fatal outcome. The constituent of Leptospira genomes may determine the level of disease severity and that needs further investigations.
Mycology and Plant Pathology Laboratory, Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh
Pyricularia oryzae pathotype Triticum, causal agent of wheat blast, has emerged in Bangladesh as a serious threat for wheat production. Virulence analysis of plant pathogen can reveal the pathogenic nature of that pathogen. In the present study, twenty-four monoconidial isolates of P. oryzae from Chuadanga, Meherpur, Kustia and Jhenaidaha districts of Bangladesh were analyzed to observe their pathogenic potential. Based on the disease reactions, all the isolates were grouped into 3 pathotypes. Present investigation revealed that the isolates with high virulence were prevalent in the studied P. oryzae population. Again, Pathotype 1 that was identified as the most virulent can be used as reference for screening resistant wheat varieties.
Dhaka Univ. J. Biol. Sci. 30(2): 151-157, 2021 (July)
In this study, 225 isolates of Pseudomonas aeruginosa were recovered from burn wounds in major hospitals in Duhok and Erbil, Iraq, between April 2015 and September 2015. A total of 136 of these isolates were from men, comprising 60.4% of the total, whereas 89 (39.6%) were recovered from women. One hundred of these isolates were selected (50 from each province of Erbil and Duhok) and subjected to 16 different antibiotics using the disc diffusion method. The isolates showed a high level of resistance to most of the tested antibiotics, with 90% of the isolates being multidrug resistant. Imipenem was considered as the most effective antibiotic against these isolates with a resistant rate of 47%. The genome of all of these isolates were successfully amplified and produced a single band for the 16S rDNA locus with a molecular weight of about 956 base pairs, which was used to confirm, at the molecular level, that all these isolates were indeed P. aeruginosa. The results of the detection of five virulence-related genes including opr1, toxA, exoS, lasB, and nan1 revealed that 10 of these isolates, accounting for 10%, lacked any of the tested virulence markers. The opr1 gene, as a marker for the presence of a pathogenicity island, was the most dominant marker among all the virulence markers and was detected in 90 isolates (90%), followed by the toxA and exoS genes, which were both observed in 86 (86%) isolates, whereas the lasB gene was found in 82 (82%) isolates and the nan1 gene in 35 (35%) of the isolates, respectively.
Toxoplasma gondii archetypes II and III are mildly virulent, yet virulence of variant strains is largely unknown. While lineage II dominates in humans in Europe, lineage III strains are present in various intermediate hosts. In Serbia, lineage III represents 24% of the population structure and occurs most frequently in domestic animals, implying a significant presence in the human food web. In this study, the virulence of four genetically distinct lineage III variants was assessed in vivo and in vitro. In vivo, two strains were shown to be intermediately virulent and two mildly virulent, with cumulative mortalities of 69.4%, 38.8%, 10.7%, and 6.8%, respectively. The strain with the highest mortality has previously been isolated in Europe and may be endemic; the strain with the lowest mortality matches ToxoDB#54, while the remaining two represent novel genotypes. Identical alleles were detected at ROP5, ROP16, ROP18, and GRA15. A set of in vitro analyses revealed proliferation and plaque formation as virulence factors. Higher levels of expression of ENO2 in intermediately virulent strains point to enhanced metabolism as the underlying mechanism. The results suggest that metabolic attenuation, and possibly stage conversion, may be delayed in virulent strains.