Posts filed under ‘Infecciones cardio-vasculares’

Bicarbonate Resensitization of Methicillin-Resistant Staphylococcus aureus to β-Lactam Antibiotics.

Antimicrob Agents Chemother. June 24, 2019 V.63 N.7  pii: e00496-19.

Ersoy SC1, Abdelhady W1, Li L1, Chambers HF2, Xiong YQ3,4, Bayer AS1,4.

1 Los Angeles Biomedical Research Institute, Torrance, California, USA.

2 Division of Infectious Diseases, Zuckerberg San Francisco General Department of Medicine, San Francisco School of Medicine, University of California, San Francisco, California, USA.

3 Los Angeles Biomedical Research Institute, Torrance, California, USA yxiong@ucla.edu .

4 Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.

Abstract

Endovascular infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major health care concern, especially infective endocarditis (IE).

Standard antimicrobial susceptibility testing (AST) defines most MRSA strains as “resistant” to β-lactams, often leading to the use of costly and/or toxic treatment regimens.

In this investigation, five prototype MRSA strains, representing the range of genotypes in current clinical circulation, were studied.

We identified two distinct MRSA phenotypes upon AST using standard media, with or without sodium bicarbonate (NaHCO3) supplementation: one highly susceptible to the antistaphylococcal β-lactams oxacillin and cefazolin (NaHCO3 responsive) and one resistant to such agents (NaHCO3 nonresponsive).

These phenotypes accurately predicted clearance profiles of MRSA from target tissues in experimental MRSA IE treated with each β-lactam.

Mechanistically, NaHCO3 reduced the expression of two key genes involved in the MRSA phenotype, mecA and sarA, leading to decreased production of penicillin-binding protein 2a (that mediates methicillin resistance), in NaHCO3-responsive (but not in NaHCO3-nonresponsive) strains.

Moreover, both cefazolin and oxacillin synergistically killed NaHCO3-responsive strains in the presence of the host defense antimicrobial peptide (LL-37) in NaHCO3-supplemented media.

These findings suggest that AST of MRSA strains in NaHCO3-containing media may potentially identify infections caused by NaHCO3-responsive strains that are appropriate for β-lactam therapy.

FULL TEXT

https://aac.asm.org/content/63/7/e00496-19.long

PDF

https://aac.asm.org/content/aac/63/7/e00496-19.full.pdf

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July 18, 2019 at 8:59 am

Staphylococcus aureus Bacteremia and Endocarditis: Making an Impact on Outcomes: The Role of the Patient and the Organism

Infectious Diseases in Clinical Practice July 2011 V.19 N.4 P.238-242

NFID Clinical Updates

Weinstein, Robert A.

Three scientific approaches to infectious disease-case series, epidemiologic investigation, and molecular analysis-have aided researchers in understanding the evolution of pathogen activity.

Four eras of pathogen activity have occurred from 1920 to the present (streptococcus, staphylococci, gram-negative rods, and multidrug-resistant organisms).

The emergence of health care-associated and community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) infections has resulted in the blurred distinction among the entities.

In addition, there are several virulence factors that contribute significantly to the pathogenicity of the organism, and single nucleotide polymorphisms (SNPs) play an important role in determining an individual’s response to infection.

Health outcomes are significantly worse in MRSA patients compared with uninfected patients or those infected with methicillin-susceptible S. aureus (MSSA).

Ongoing molecular research will continue to elucidate mechanisms associated with virulence of MRSA.

FULL TEXT

https://journals.lww.com/infectdis/Fulltext/2011/07000/Staphylococcus_aureus_Bacteremia_and_Endocarditis_.2.aspx

PDF (CLIC en PDF)

December 7, 2018 at 9:30 am

Highlights From Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus aureus Infections in Adults and Children

Infectious Diseases in Clinical Practice May 2011 V.19 N.3 P.207-20

Clinical Guidelines

File, Thomas M. Jr

Recently, the Infectious Diseases Society published evidence-based guidelines for the treatment of methicillin-resistant Staphylococcus aureus infections.

The guideline discusses the management of a variety of infections including skin infections, bacteremia and endocarditis, pneumonia, and osteomyelitis and joint infections.

FULL TEXT

https://journals.lww.com/infectdis/Fulltext/2011/05000/Highlights_From_Clinical_Practice_Guidelines_by.13.aspx

PDF (CLIC en PDF)

December 7, 2018 at 9:28 am

Infective endocarditis due to Streptococcus dysgalactiae: clinical presentation and microbiological features

European Journal of Clinical Microbiology & Infectious Diseases December 2018 V.37 N.12 P.2261–2272

Anna Bläckberg, Nilson, Volkan Özenci, Lars Olaison, Magnus Rasmussen

Knowledge of infective endocarditis (IE) caused by Streptococcus dysgalactiae (SD) is limited.

This study aimed to identify the clinical and microbiological features of SD-caused IE and to investigate any possible synergy between penicillin and gentamicin on SD isolates.

Cases of IE 2008–2016 due to SD reported to the Swedish Registry of Infective Endocarditis (SRIE) were identified. Isolates were emm typed and synergy between antibiotics was determined in time-kill experiments. Medical records were reviewed and SD-cases were compared to cases of IE due to other pathogens reported to the SRIE.

Fifty cases of SD-caused IE were confirmed. emm types stC74a, stG62647, and stG643 were most commonly encountered.

The patients had a median age of 74 years (range 38–93) and were significantly older compared to patients with Staphylococcus aureus-caused IE, (65 years (p = 0.003)).

The median time to diagnosis from symptom onset was 1 day for patients with SD-caused IE which was less compared to patients with IE due to the other pathogens (2–15 days). Embolization was seen in 46% and the in-hospital mortality was 8%.

Etest-based methods did not indicate any synergy between penicillin and gentamicin whereas synergy was noted for four out of nine isolates applying time-kill assays.

This is the largest study of SD-caused IE, a condition with an acute onset predominantly affecting elderly people. Synergy between penicillin and gentamicin against some SD isolates was distinguished but the potential benefit of this must be weighed against the risk of aminoglycoside side effects.

PDF

https://link.springer.com/content/pdf/10.1007%2Fs10096-018-3367-7.pdf

November 21, 2018 at 12:27 pm

Should Acute Q-Fever Patients be Screened for Valvulopathy to Prevent Endocarditis?

Clinical Infectious Diseases August 1, 2018 V.67 N.3 P.360-366

Marit M A de Lange; Laura E V Gijsen; Cornelia C H Wielders; Wim van der Hoek; Arko Scheepmaker

We found no difference in occurrence of chronic Q-fever between patients with or without a newly detected valvulopathy at time of acute Q-fever diagnosis. Thus, universal screening is not justified and would lead to unnecessary and undesirable long-term antibiotic use.

FULL TEXT

https://academic.oup.com/cid/article/67/3/360/4877027

PDF (CLIC en PDF)

November 4, 2018 at 8:29 am

Understanding the Mechanism of Bacterial Biofilms Resistance to Antimicrobial Agents.

Open Microbiol J. 2017 Apr 28;11:53-62.

Singh S1, Singh SK2, Chowdhury I3, Singh R2.

1 Department of Kriya Sharir, Institute of Medical Sciences, Banaras Hindu University, Varanasi- 221 005 UP India.

2 Department of Microbiology, Biochemistry and Immunology, Morehouse School of Medicine, Atlanta, GA, USA.

3 Department of Obstetrics and Gynecology; Morehouse School of Medicine, Atlanta, GA, USA.

Abstract

A biofilm is a group of microorganisms, that causes health problems for the patients with indwelling medical devices via attachment of cells to the surface matrix. It increases the resistance of a microorganism for antimicrobial agents and developed the human infection. Current strategies are removed or prevent the microbial colonies from the medical devices, which are attached to the surfaces. This will improve the clinical outcomes in favor of the patients suffering from serious infectious diseases. Moreover, the identification and inhibition of genes, which have the major role in biofilm formation, could be the effective approach for health care systems. In a current review article, we are highlighting the biofilm matrix and molecular mechanism of antimicrobial resistance in bacterial biofilms.

PDF

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5427689/pdf/TOMICROJ-11-53.pdf

 

October 14, 2018 at 10:44 am

Biofilms: survival mechanisms of clinically relevant microorganisms.

Clinical Microbiology Reviews April 2002 V.15 N.2 P.167-93.

Donlan RM1, Costerton JW.

1 Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. rld8@cdc.gov

Abstract

Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Current intervention strategies are designed to prevent initial device colonization, minimize microbial cell attachment to the device, penetrate the biofilm matrix and kill the associated cells, or remove the device from the patient. In the future, treatments may be based on inhibition of genes involved in cell attachment and biofilm formation.

PDF

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC118068/pdf/0012.pdf

October 14, 2018 at 10:41 am

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