resistance mechanisms
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Author(s):  
Julie Flood ◽  

In the early 20th century, coffee wilt disease (CWD) caused by the vascular wilt pathogen, Fusarium xylarioides, spread across Africa destroying coffee trees, reducing yields and significantly impacting producer livelihoods. Through systematic sanitation and establishment of breeding programmes in affected countries, CWD appeared to decline. However, the disease re-emerged and increased to epidemic proportions in the 1990s affecting robusta coffee in DRC, Uganda and Tanzania and arabica coffee in Ethiopia. In 1999, 14.5 million robusta coffee trees were estimated to have been destroyed in Uganda alone. This chapter discusses the history, impact, symptoms, cause and spread of CWD. A summary of the Regional Coffee Wilt Programme (RCWP) which examined many aspects of the disease and its management is also provided. . Future research trends include host specificity, underlying resistance mechanisms and the role of alternative hosts. Investigation of pathogen ecology is needed to allow greater focus on agroecological management practices.


BMC Genomics ◽  
2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Sixian Chen ◽  
Aizhen Fu ◽  
Yuan Lu ◽  
Wei Lu ◽  
Yongfeng Chen ◽  
...  

Abstract Background Lung carcinoma is a common geriatric disease. The development of genotype-targeted therapies greatly improved the management of lung carcinoma. However, the treatment for old patients can be more complex than that for young individuals. Results To investigate the benefits of genetic detection for older patients with lung carcinoma, we explored the genomic profiling of 258 patients with more than 55 years using a targeted next generation sequencing, and some of these patients were treated with targeted therapies based on the results of genomic detection. KRAS codon 61 mutations were found in 15.2% KRAS-mutated patients, which tend to be co-existing with other classical activating mutations other than codons 12/13. Acquired EGFR C797S mutations were identified in 2 cases and ERBB2 amplification was identified in 1 case. All these 3 cases developed resistance to EGFR tyrosine kinase inhibitors and showed expected results of their followed therapies. The median progression-free survival and median overall survival of patients treated with molecular targeted therapies were better than those of patients treated with chemoradiotherapy alone. Conclusions Our findings revealed the specific genomic profiles of patients older than 55 years with lung carcinoma and suggested that these old patients have been benefit from the genetic detection, which helped identify druggable mutations and distinguish resistance mechanisms.


PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0261713
Author(s):  
Assalif Demissew ◽  
Abebe Animut ◽  
Solomon Kibret ◽  
Arega Tsegaye ◽  
Dawit Hawaria ◽  
...  

Background Indoor residual spraying and insecticide-treated nets are among the key malaria control intervention tools. However, their efficacy is declining due to the development and spread of insecticide resistant vectors. In Ethiopia, several studies reported resistance of An. arabiensis to multiple insecticide classes. However, such data is scarce in irrigated areas of the country where insecticides, pesticides and herbicides are intensively used. Susceptibility of An. gambiae s.l. to existing and new insecticides and resistance mechanisms were assessed in Arjo-Didessa sugarcane plantation area, southwestern Ethiopia. Methods Adult An. gambiae s.l. reared from larval/pupal collections of Arjo-Didessa sugarcane irrigation area and its surrounding were tested for their susceptibility to selected insecticides. Randomly selected An. gambiae s.l. (dead and survived) samples were identified to species using species-specific polymerase chain reaction (PCR) and were further analyzed for the presence of knockdown resistance (kdr) alleles using allele-specific PCR. Results Among the 214 An. gambiae s.l. samples analyzed by PCR, 89% (n = 190) were An. amharicus and 9% (n = 20) were An. arabiensis. Mortality rates of the An. gambiae s.l. exposed to deltamethrin and alphacypermethrin were 85% and 86.8%, respectively. On the other hand, mortalities against pirmiphos-methyl, bendiocarb, propoxur and clothianidin were 100%, 99%, 100% and 100%, respectively. Of those sub-samples (An. amharicus and An. arabiensis) examined for presence of kdr gene, none of them were found to carry the L1014F (West African) allelic mutation. Conclusion Anopheles amharicus and An. arabiensis from Arjo-Didessa sugarcane irrigation area were resistant to pyrethroids which might be synergized by extensive use of agricultural chemicals. Occurrence of pyrethroid resistant malaria vectors could challenge the ongoing malaria control and elimination program in the area unless resistance management strategies are implemented. Given the resistance of An. amharicus to pyrethroids, its behavior and vectorial capacity should be further investigated.


Diagnostics ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 197
Author(s):  
Camille Gonzalez ◽  
Christian Moguet ◽  
Arnaud Chalin ◽  
Saoussen Oueslati ◽  
Laurent Dortet ◽  
...  

Rapid detection of expanded-spectrum cephalosporins (ESC) hydrolysing enzymes is crucial to implement infection control measures and antibiotic stewardship. Here, we have evaluated three biochemical ESC hydrolysis assays (ESBL NDP test, β-LACTA™ test, LFIA-CTX assay) and the NG-Test® CTX-M MULTI that detects CTX-M enzymes, on 93 well-characterized Gram-negative isolates, including 60 Enterobacterales, 21 Pseudomonas spp. and 12 Acinetobacter spp. The performances were good for all three hydrolysis assays, with the LFIA-CTX being slightly more sensitive and specific on the tested panel of isolates especially with Enterobacterales, without ambiguous results. This study showed that LFIA-CTX may be used for the detection of ESC hydrolysis as a competitive alternative to already available assays (β-LACTA™ test and ESBL NDP test) without any specific equipment and reduced hands-on-time. The lateral flow immunoassay NG-Test® CTX-M MULTI has proven to be a useful, easy, rapid, and reliable confirmatory test in Enterobacterales for detection of CTX-M-type ESBLs, which account for most of the resistance mechanisms leading to ESC resistance in Enterobacterales, but it misses rare ESC hydrolysing β-lactamases (AmpC, minor ESBLs, and carbapenemases). Combining it with the LFIA-CTX assay would yield an assay detecting the most frequently-encountered ESBLs (CTX-M-like β-lactamases) together with ESC hydrolysis.


2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Qingqing Fang ◽  
Yu Feng ◽  
Alan McNally ◽  
Zhiyong Zong

AbstractCarbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a severe global health challenge. We isolate and characterize two previously unidentified lytic phages, P24 and P39, with large burst sizes active against ST11 KL64, a major CRKP lineage. P24 and P39 represent species of the genera Przondovirus (Studiervirinae subfamily) and Webervirus (Drexlerviridae family), respectively. P24 and P39 together restrain CRKP growth to nearly 8 h. Phage-resistant mutants exhibit reduced capsule production and decreased virulence. Modifications in mshA and wcaJ encoding capsule polysaccharide synthesis mediate P24 resistance whilst mutations in epsJ encoding exopolysaccharide synthesis cause P39 resistance. We test P24 alone and together with P39 for decolonizing CRKP using mouse intestinal colonization models. Bacterial load shed decrease significantly in mice treated with P24 and P39. In conclusion, we report the characterization of two previously unidentified lytic phages against CRKP, revealing phage resistance mechanisms and demonstrating the potential of lytic phages for intestinal decolonization.


2022 ◽  
Vol 12 ◽  
Author(s):  
Brandon Robin ◽  
Marion Nicol ◽  
Hung Le ◽  
Ali Tahrioui ◽  
Annick Schaumann ◽  
...  

Acinetobacter baumannii has emerged as one of the most problematic bacterial pathogens responsible for hospital-acquired and community infections worldwide. Besides its high capacity to acquire antibiotic resistance mechanisms, it also presents high adhesion abilities on inert and living surfaces leading to biofilm development. This lifestyle confers additional protection against various treatments and allows it to persist for long periods in various hospital niches. Due to their remarkable antimicrobial tolerance, A. baumannii biofilms are difficult to control and ultimately eradicate. Further insights into the mechanism of biofilm development will help to overcome this challenge and to develop novel antibiofilm strategies. To unravel critical determinants of this sessile lifestyle, the proteomic profiles of two A. baumannii strains (ATTC17978 and SDF) grown in planktonic stationary phase or in mature solid–liquid (S-L) biofilm were compared using a semiquantitative proteomic study. Of interest, among the 69 common proteins determinants accumulated in the two strains at the S-L interface, we sorted out the MacAB-TolC system. This tripartite efflux pump played a role in A. baumannii biofilm formation as demonstrated by using ΔmacAB-tolC deletion mutant. Complementary approaches allowed us to get an overview of the impact of macAB-tolC deletion in A. baumannii physiology. Indeed, this efflux pump appeared to be involved in the envelope stress response occurring in mature biofilm. It contributes to maintain wild type (WT) membrane rigidity and provides tolerance to high osmolarity conditions. In addition, this system is probably involved in the maintenance of iron and sulfur homeostasis. MacAB-TolC might help this pathogen face and adapt to deleterious conditions occurring in mature biofilms. Increasing our knowledge of A. baumannii biofilm formation will undoubtedly help us develop new therapeutic strategies to tackle this emerging threat to human health.


Antibiotics ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 102
Author(s):  
Daniela Fortini ◽  
Slawomir Owczarek ◽  
Anna Dionisi ◽  
Claudia Lucarelli ◽  
Sergio Arena ◽  
...  

Background: A collection of human-epidemiologically unrelated S. enterica strains collected over a 3-year period (2016 to 2018) in Italy by the national surveillance Enter-Net Italia was analysed. Methods: Antimicrobial susceptibility tests, including the determination of minimal inhibitory concentrations (MICs) for colistin, were performed. Colistin resistant strains were analysed by PCR to detect mobile colistin resistance (mcr) genes. In mcr-negative S. enterica serovar Enteritidis strains, chromosomal mutations potentially involved in colistin resistance were identified by a genomic approach. Results: The prevalence of colistin-resistant S. enterica strains was 7.7%, the majority (87.5%) were S. Enteritidis. mcr genes were identified only in one strain, a S. Typhimurium monophasic variant, positive for both mcr-1.1 and mcr-5.1 genes in an IncHI2 ST4 plasmid. Several chromosomal mutations were identified in the colistin-resistant mcr-negative S. Enteritidis strains in proteins involved in lipopolysaccharide and outer membrane synthesis and modification (RfbN, LolB, ZraR) and in a component of a multidrug efflux pump (MdsC). These mutated proteins were defined as possible candidates for colistin resistance in mcr-negative S. Enteritidis of our collection. Conclusions: The colistin national surveillance in Salmonella spp. in humans, implemented with genomic-based surveillance, permitted to monitor colistin resistance, determining the prevalence of mcr determinants and the study of new candidate mechanisms for colistin resistance.


2022 ◽  
pp. 1-7
Author(s):  
Dal-Hoe Koo ◽  
Rajendran Sathishraj ◽  
Bernd Friebe ◽  
Bikram S. Gill

In agriculture, various chemicals are used to control the weeds. Out of which, glyphosate is an important herbicide invariably used in the cultivation of glyphosate-resistant crops to control weeds. Overuse of glyphosate results in the evolution of glyphosate-resistant weeds. Evolution of glyphosate resistance (GR) in <i>Amaranthus palmeri</i> (AP) is a serious concern in the USA. Investigation of the mechanism of GR in AP identified different resistance mechanisms of which <i>5-enolpyruvylshikimate-3-phosphate synthase</i> (<i>EPSPS</i>) gene amplification is predominant. Molecular analysis of GR AP identified the presence of a 5- to &#x3e;160-fold increase in copies of the <i>EPSPS</i> gene than in a glyphosate-susceptible (GS) population. This increased copy number of the <i>EPSPS</i> gene increased the genome size ranging from 3.5 to 11.8%, depending on the copy number compared to the genome size of GS AP. FISH analysis using a 399-kb <i>EPSPS</i> cassette derived from bacterial artificial chromosomes (BACs) as probes identified that amplified <i>EPSPS</i> copies in GR AP exist in extrachromosomal circular DNA (eccDNA) in addition to the native copy in the chromosome. The <i>EPSPS</i> gene-containing eccDNA having a size of ∼400 kb is termed <i>EPSPS</i>-eccDNA and showed somatic mosacism in size and copy number. <i>EPSPS</i>-eccDNA has a genetic mechanism to tether randomly to mitotic or meiotic chromosomes during cell division or gamete formation and is inherited to daughter cells or progeny generating copy number variation. These eccDNAs are stable genetic elements that can replicate and exist independently. The genomic characterization of the <i>EPSPS</i> locus, along with the flanking regions, identified the presence of a complex array of repeats and mobile genetic elements. The cytogenomics approach in understanding the biology of <i>EPSPS</i>-eccDNA sheds light on various characteristics of <i>EPSPS</i>-eccDNA that favor GR in AP.


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