Klebsiella pneumoniae strains producing KPC-type carbapenemases (KPC-KP) are challenging multidrug-resistant pathogens due to their extensively drug-resistant phenotypes and potential for epidemic ...dissemination in health care settings. Colistin is a key component of the combination antimicrobial regimens used for treatment of severe KPC-KP infections. We previously reported that insertional inactivation of the mgrB gene, encoding a negative-feedback regulator of the PhoQ-PhoP signaling system, can be responsible for colistin resistance in KPC-KP, due to the resulting upregulation of the Pmr lipopolysaccharide modification system. In this work we investigated the status of the mgrB gene in a collection of 66 colistin-resistant nonreplicate clinical strains of KPC-KP isolated from different hospitals in Italy and Greece. Overall, 35 strains (53%) exhibited alterations of the mgrB gene, including insertions of different types of mobile elements (IS5-like, IS1F-like, or ISKpn14), nonsilent point mutations, and small intragenic deletions. Four additional strains had a larger deletion of the mgrB locus, while the remaining 27 strains (41%) did not show mgrB alterations. Transcriptional upregulation of the phoQ and pmrK genes (part of the phoPQ and pmrHFIJKLM operon, respectively) was observed in all strains with mgrB alterations. Complementation experiments with a wild-type mgrB gene restored colistin susceptibility and basal expression levels of phoQ and pmrK genes in strains carrying different types of mgrB alterations. The present results suggest that mgrB alteration can be a common mechanism of colistin resistance among KPC-KP in the clinical setting.
Abstract
Objectives
To characterize a novel phenicol–oxazolidinone–tetracycline resistance gene, named poxtA, identified in a previously described MRSA strain that was highly resistant to linezolid ...and also carried the cfr gene.
Methods
The poxtA gene was identified by bioinformatic analysis of the whole genome sequence of Staphylococcus aureus AOUC-0915. The poxtA gene was cloned in a shuttle plasmid vector and expressed in Escherichia coli, S. aureus and Enterococcus faecalis to investigate the protein function. Comparative sequence analyses at the protein and genetic levels were carried out using standard procedures.
Results
The poxtA gene encodes a protein that is 32% identical to OptrA and exhibits structural features typical of the F lineage of the ATP-binding cassette (ABC) protein superfamily that cause antibiotic resistance by ribosomal protection. Expression of poxtA in E. coli, S. aureus and E. faecalis was able to decrease susceptibility to phenicols, oxazolidinones and tetracyclines. A database search identified the presence of poxtA in E. faecalis, Enterococcus faecium and Pediococcus acidilactici strains, mostly of animal origin, and revealed the presence of poxtA homologues in the genomes of some Clostridiales. Analysis of the genetic context revealed that poxtA was located in a composite transposon-like structure containing two IS1216 elements.
Conclusions
A novel resistance gene, named poxtA, encoding a protein of the antibiotic resistance (ARE) ABC-F lineage, was identified in the genome of an MRSA of clinical origin. PoxtA can confer decreased susceptibility to phenicols, oxazolidinones and tetracyclines and is associated with a putative mobile element that could contribute to its horizontal dissemination.
Metallo-β-lactamases: a last frontier for β-lactams? Cornaglia, Giuseppe, MD; Giamarellou, Helen, MD; Rossolini, Gian Maria, MD
The Lancet infectious diseases,
05/2011, Letnik:
11, Številka:
5
Journal Article
Recenzirano
Summary Metallo-β-lactamases are resistance determinants of increasing clinical relevance in Gram-negative bacteria. Because of their broad range, potent carbapenemase activity and resistance to ...inhibitors, these enzymes can confer resistance to almost all β-lactams. Since the 1990s, several metallo-β-lactamases encoded by mobile DNA have emerged in important Gram-negative pathogens (ie, in Enterobacteriaceae, Pseudomonas aeruginosa , and Acinetobacter baumannii ). Some of these enzymes (eg, VIM-1 and NDM-1) have been involved in the recent crisis resulting from the international dissemination of carbapenem-resistant Klebsiella pneumoniae and other enterobacteria. Although substantial knowledge about the molecular biology and genetics of metallo-β-lactamases is available, epidemiological data are inconsistent and clinical experience is still lacking; therefore, several unsolved or debatable issues remain about the management of infections caused by producers of metallo-β-lactamase. The spread of metallo-β-lactamases presents a major challenge both for treatment of individual patients and for policies of infection control, exposing the substantial unpreparedness of public health structures in facing up to this emergency.
Since early 2020, the COVID-19 pandemic has caused an excess in morbidity and mortality rates worldwide. Containment strategies rely firstly on rapid and sensitive laboratory diagnosis, with ...molecular detection of the viral genome in respiratory samples being the gold standard. The reliability of diagnostic protocols could be affected by SARS-CoV-2 genetic variability. In fact, mutations occurring during SARS-CoV-2 genomic evolution can involve the regions targeted by the diagnostic probes. Following a review of the literature and an in silico analysis of the most recently described virus variants (including the UK B 1.1.7 and the South Africa 501Y.V2 variants), we conclude that the described genetic variability should have minimal or no effect on the sensitivity of existing diagnostic protocols for SARS-CoV-2 genome detection. However, given the continuous emergence of new variants, the situation should be monitored in the future, and protocols including multiple targets should be preferred.
Abstract Objectives In airway infections, biofilm formation has been demonstrated to be responsible for both acute and chronic events, and constitutes a genuine challenge in clinical practice. ...Difficulty in eradicating biofilms with systemic antibiotics has led clinicians to consider the possible role of non-antibiotic therapy. The aim of this review is to examine current evidence for the use of N-acetylcysteine (NAC) in the treatment of biofilm-related respiratory infections. Methods Electronic searches of PUBMED up to September 2015 were conducted, searching for ‘biofilm’, ‘respiratory tract infection’, ‘N-acetylcysteine’, ‘cystic fibrosis’, ‘COPD’, ‘bronchiectasis’, ‘otitis’, and ‘bronchitis’ in titles and abstracts. Studies included for review were primarily in English, but a few in Italian were also selected. Results Biofilm formation may be involved in many infections, including ventilator-associated pneumonia, cystic fibrosis, bronchiectasis, bronchitis, and upper respiratory airway infections. Many in vitro studies have demonstrated that NAC is effective in inhibiting biofilm formation, disrupting preformed biofilms (both initial and mature), and reducing bacterial viability in biofilms. There are fewer clinical studies on the use of NAC in disruption of biofilm formation, although there is some evidence that NAC alone or in combination with antibiotics can decrease the risk of exacerbations of chronic bronchitis, chronic obstructive pulmonary disease, and rhinosinusitis. However, the usefulness of NAC in the treatment of cystic fibrosis and bronchiectasis is still matter of debate. Most of the studies published to date have used oral or intramuscular NAC formulations. Conclusions Evidence from in vitro studies indicates that NAC has good antibacterial properties and the ability to interfere with biofilm formation and disrupt biofilms. Results from clinical studies have provided some encouraging findings that need to be confirmed and expanded using other routes of administration of NAC such as inhalation.
The characterization of the adaptive immune response to COVID-19 vaccination in individuals who recovered from SARS-CoV- 2 infection may define current and future clinical practice. To determine the ...effect of the 2-dose BNT162b2 mRNA COVID-19 vaccination schedule in individuals who recovered from COVID-19 (COVID- 19-recovered subjects) compared with naive subjects, we evaluated SARS-CoV-2 Spike-specific T and B cell responses, as well as specific IgA, IgG, IgM, and neutralizing antibodies titers in 22 individuals who received the BNT162b2 mRNA COVID-19 vaccine, 11 of whom had a previous history of SARS-CoV-2 infection. Evaluations were performed before vaccination and then weekly until 7 days after second injection. Data obtained clearly showed that one vaccine dose is sufficient to increase both cellular and humoral immune response in COVID-19-recovered subjects without any additional improvement after the second dose. On the contrary, the second dose proved mandatory in naive subjects to further enhance the immune response. These findings were further confirmed at the serological level in a larger cohort of naive (n = 68) and COVID-19-recovered (n = 29) subjects, tested up to 50 days after vaccination. These results question whether a second vaccine injection in COVID-19-recovered subjects is required, and indicate that millions of vaccine doses may be redirected to naive individuals, thus shortening the time to reach herd immunity.
The esophageal microbiota in health and disease Di Pilato, Vincenzo; Freschi, Giancarlo; Ringressi, Maria Novella ...
Annals of the New York Academy of Sciences,
October 2016, Letnik:
1381, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The esophageal mucosa is among the sites colonized by human microbiota, the complex microbial ecosystem that colonizes various body surfaces and is increasingly recognized to play roles in several ...physiological and pathological processes. Our understanding of the composition of the esophageal microbiota in health and disease is challenged by the need for invasive sampling procedures and by the dynamic nature of the esophageal environment and remains limited in comparison with the information available for other body sites. Members of the genus Streptococcus appear to be the major components of the microbiota of the healthy esophagus, although the presence of several other taxa has also been reported. Dysbiosis, consisting of enrichment in some Gram‐negative taxa (including Veillonella, Prevotella, Haemophilus, Neisseria, Campylobacter, and Fusobacterium), has been reported in association with gastroesophageal reflux disease and is hypothesized to contribute to the evolution of this condition toward Barrett's esophagus (which is the most common esophageal precancerous lesion) and, eventually, adenocarcinoma. Some Campylobacter species (mostly C. concisus) are also putatively involved in the progression of disease toward adenocarcinoma. However, variable findings have recently been reported in additional studies. Causative relationships between dysbiosis or specific bacterial species and esophageal diseases remain controversial and warrant further investigations.
In the near future, the overlap of Coronavirus disease 2019 (COVID-19) and dengue epidemics is a concrete threat in tropical regions. Co-epidemics of COVID-19 and dengue could be an overwhelming ...challenge for health systems in low- and middle-income countries. In this work, we investigated potential serological cross-reactions between COVID-19 and dengue patients. Among 32 COVID-19 positive sera, no positive Dengue virus (DENV) IgG/IgM results were observed. On the other hand, one false-positive result was observed among 44 DENV-positive sera tested for COVID-19 antibodies with each of the two rapid tests used. Further data on accuracy of COVID-19 diagnostic test are urgently warranted.
Colistin is a key drug for the treatment of infections caused by extensively drug-resistant strains of Enterobacteriaceae producing carbapenemases. However, the emergence of colistin resistance is ...being increasingly reported, especially among Klebsiella pneumoniae strains producing KPC-type carbapenemases (KPC-KP). In this work, we investigated colistin-susceptible (KPB-1) and colistin-resistant (KPB-2) sequential isolates obtained from a patient with a KPC-KP infection before and after low-dosage colistin treatment, respectively. By using a next-generation sequencing approach and comparative genomic analysis of the two isolates, we detected in KPB-2 a nonsynonymous nucleotide substitution in the gene encoding the PmrB sensor kinase, resulting in a leucine-to-arginine substitution at amino acid position 82. Compared with KPB-1, KPB-2 exhibited upregulated transcription of pmrA and of pmrK, which is part of the pmrHFIJKLM operon responsible for modification of the colistin lipopolysaccharide target. Complementation with wild-type pmrB in KPB-2 restored colistin susceptibility and reduced the transcription of pmrA and pmrK to basal levels, while expression of PmrB(L82R) in KPB-1 did not alter colistin susceptibility or upregulate pmrA and pmrK expression, confirming the dominance of wild-type PmrB versus the PmrB(L82R) mutant. The present results indicated that PmrB mutations mediating colistin resistance may be selected during low-dosage colistin treatment. The colistin-resistant phenotype of KPB-2 was stable for up to 50 generations in the absence of selective pressure and was not associated with a significant fitness cost in a competition experiment.
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