Risk factors for hospital-acquired methicillin-resistant Staphylococcus aureus bacteraemia: a case-control study

Automated detection of methicillin-resistant Staphylococcus aureus with the MRSA CHROM imaging application on BD Kiestra Total Lab Automation System

The virulence of methicillin-resistant Staphylococcus aureus (MRSA) and its potentially fatal outcome necessitate rapid and accurate detection of patients colonized with MRSA in healthcare settings. Using the BD Kiestra Total Lab Automation (TLA) System in conjunction with the MRSA Application (MRSA App), an imaging application that uses artificial intelligence to interpret colorimetric information (mauve-colored colonies) indicative of MRSA pathogen presence on CHROMagar chromogenic media, anterior nares specimens from three sites were evaluated for the presence of mauve-colored colonies. Results obtained with the MRSA App were compared to manual reading of agar plate images by proficient laboratory technologists. Of 1,593 specimens evaluated, 1,545 (96.98%) were concordant between MRSA App and laboratory technologist reading for the detection of MRSA growth [sensitivity 98.15% (95% CI, 96.03, 99.32) and specificity 96.69% (95% CI, 95.55, 97.60)]. This multi-site study is the first evaluation of the MRSA App in conjunction with the BD Kiestra TLA System. Using the MRSA App, our results showed 98.15% sensitivity and 96.69% specificity for the detection of MRSA from anterior nares specimens. The MRSA App, used in conjunction with laboratory automation, provides an opportunity to improve laboratory efficiency by reducing laboratory technologists' labor associated with the review and interpretation of cultures.

Evaluation of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia: Epidemiology, clinical characteristics, and outcomes in the older patients in a tertiary teaching hospital in Malaysia

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is a major concern in the global healthcare system. However, data from Asian regions dealing with the singularity of this infection in older persons is lacking. We aimed to identify the differences in the clinical characteristics and outcomes of MRSA bacteremia between adults aged 18-64 and ≥ 65 years.

METHODS

A retrospective study cohort was conducted at the University Malaya Medical Centre (UMMC) on cases of MRSA bacteremia from 2012 to 2016. Patient demographic and clinical data were collected for risk factors analyses.

RESULTS

New cases of MRSA bacteremia showed a trend of increase from 0.12 to 100 admissions in 2012 to 0.17 per 100 admissions in 2016 but a drop was observed in 2014 (0.07 per 100 admissions). Out of the 275 patients with MRSA bacteremia, 139 (50.5%) patients were aged ≥ 65 years old. Co-morbidities and severity at presentation were significantly higher among older adults, including diabetes mellitus (p = 0.035), hypertension (p = 0.001), and ischemic heart disease (p < 0.001), as well as higher Charlson Comorbidity Index (p < 0.001) and Pitt bacteremia scores (p = 0.016). Central line-associated bloodstream infections were more common among younger patients (37.5% vs. 17.3% in older patients, p < 0.001), while skin and soft tissue infections are more frequent among older adults (20.9% vs. 10.3% in younger patients, p = 0.016). All-cause mortality and in-hospital mortality were significantly higher in older patients (82.7% and 56.1% vs. 63.2% and 28.7% in younger patients, p < 0.001). Multivariate analysis revealed age ≥ 65 years (adjusted odds ratio: 3.36; 95% confidence interval: 1.24-9.13), Pitt score ≥ 3 (2.15; 1.54-3.01), hospital (6.12; 1.81-20.72) and healthcare (3.19; 1.30-7.81) acquisition of MRSA, indwelling urinary catheters (5.43; 1.39-21.23), inappropriate targeted treatment (8.08; 1.15-56.86), lack of infectious disease team consultation (2.90; 1.04-8.11) and hypoalbuminemia (3.31; 1.25-8.79), were significant risk factors for 30-day mortality.

CONCLUSION

Older patients' risk of mortality from MRSA bacteremia was three times higher than younger patients. Our data will contribute to developing and validating a robust scoring system for risk-stratifying patients to achieve better management and improved clinical outcomes.

Molecular Characterization of Community- and Hospital- Acquired Methicillin-Resistant Staphylococcus aureus Isolates during COVID-19 Pandemic

Methicillin-resistant Staphylococcus aureus (MRSA) is a drug-resistant superbug that causes various types of community- and hospital-acquired infectious diseases. The current study was aimed to see the genetic characteristics and gene expression of MRSA isolates of nosocomial origin. A total of 221 MRSA isolates were identified from 2965 clinical samples. To identify the bacterial isolates, the clinical samples were inoculated on blood agar media plates first and incubated at 37 °C for 18-24 h. For further identification, the Gram staining and various biochemical tests were performed once the colonies appeared on the inoculated agar plates. The phenotypic identification of antibiotic susceptibility patterns was carried out using Kirby-Bauer disk diffusion method by following the Clinical and Laboratory Standards Institute (CLSI) 2019 guidelines. The biofilm-producing potentials of MRSA were checked quantitatively using a spectrophotometric assay. All strains were characterized genotypically by SCCmec and agr typing using the specific gene primers. Furthermore, a total of twelve adhesion genes were amplified in all MRSA isolates. MRSA was a frequently isolated pathogen (44% community acquired (CA)-MRSA and 56% hospital acquired (HA)-MRSA), respectively. Most of the MRSA isolates were weak biofilm producers (78%), followed by moderate (25%) and strong (7%) biofilm producers, respectively. Prominent adhesion genes were clfB (100%), icaAD (91%), fib (91%), sdrC (91%) followed by eno (89%), fnbA (77%), sdrE (67%), icaBC (65%), clfA (65%), fnbB (57%), sdrD (57%), and cna (48%), respectively. The results of the current study will help to understand and manage the spectrum of biofilm-producing MRSA-associated hospital-acquired infections and to provide potential molecular candidates for the identification of biofilm-producing MRSA.

Wound Infection Incidence and Obesity in Elective Cesarean Sections in Jordan

Background:

Wound infection is a challenge that face healthcare facilities.

Objective:

The aim of the study was to assess the effect of obesity on wound infection incidence.

Methods:

A prospective study involved 127 patients underwent elective Cesarean section surgeries in the first ten months of 2018 with a follow up period of 90 days.

Results:

The wound infection incidence was 37.8%; the suture infection was 15.7% and SSI was 22%, which divided into: the superficial SSI among 23 (82.1%) patients, and deep tissue SSI among five (17.9%) patients. Obese patients with BMI of 30 kg/m2 or more were significantly at higher risk for wound infections than those whose BMI less than 30 kg/m2 (p= 0.02, relative risk= 2.363).

Conclusion:

Obese patients who underwent Cesarean sections were found to have higher risk to develop wound infections. A larger scale study is needed to determine other associated risk factors.

Development of a Machine Learning Algorithm to Predict Nonroutine Discharge Following Unicompartmental Knee Arthroplasty

BACKGROUND

Reliable and effective prediction of discharge destination following unicompartmental knee arthroplasty (UKA) can optimize patient outcomes and system expenditure. The purpose of this study is to develop a machine learning algorithm that can predict nonhome discharge in patients undergoing UKA.

METHODS

A retrospective review of a prospectively collected national surgical outcomes database was performed to identify adult patients who underwent UKA from 2015 to 2019. Nonroutine discharge was defined as discharge to a location other than home. Five machine learning algorithms were developed to predict this outcome. Performance of the algorithms was assessed through discrimination, calibration, and decision curve analysis.

RESULTS

Overall, of the 7275 patients included, 263 (3.6) patients were unable to return home upon discharge following UKA. The factors determined most important for identification of candidates for nonroutine discharge were total hospital length of stay, preoperative hematocrit, body mass index, preoperative sodium, American Society of Anesthesiologists classification, gender, and functional status. The extreme boosted model achieved the best performance based on discrimination (area under the curve = 0.875), calibration, and decision curve analysis. This model was integrated into a web-based open access application able to provide both predictions and explanations.

CONCLUSION

The present model can, following appropriate external validation, be used to augment clinician decision-making in patients undergoing elective UKA. Patients with high preoperative probabilities of nonroutine discharge based on nonmodifiable risk factors should be counseled to start the insurance authorization process with case management to avoid unnecessary inpatient stay, and those with modifiable risk can attempt prehabilitation to optimize these parameters before surgery.

Bacterial translocation in horses with colic and the potential association with surgical site infection: a pilot study

BACKGROUND

Surgical site infection (SSI) is a leading cause of morbidity in horses undergoing emergency exploratory laparotomy for the treatment of acute colic. The exact mechanism by which SSI develops in these cases is unclear. This prospective observational study investigated whether bacterial translocation occurs in horses with acute colic and if there is an association between bacterial translocation and development of SSI.

METHODS

Peripheral venous blood (PVB) and peritoneal fluid (PF) samples were collected on admission and PF samples were collected at the end of surgery from horses presenting for investigation of acute colic. Any discharge from the laparotomy incision in horses that developed SSI was also collected. All samples were submitted for bacterial culture.

RESULTS

In total, 7.7 per cent of PVB samples (3/39), 11.8 per cent (4/34) of admission PF samples and 8.7 per cent (2/23) of the PF samples at surgery were culture positive. The prevalence of SSI was 10.2 per cent. No association was identified between a positive PVB or PF culture and development of a SSI or survival to hospital discharge.

CONCLUSION

Bacterial translocation can occur in some horses with acute colic. However, we were unable to identify any association between bacterial translocation and the development of SSIs following emergency exploratory laparotomy.

Nasal colonization with methicillin-resistant Staphylococcus aureus associated with elevated homocysteine levels in the general US adults

Given the emergence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) as a global health threat, understanding the risk factors for MRSA infection in the community may be a reasonable strategy to prevent it. We investigated the associations between serum homocysteine levels and prevalence of nasal colonization with S aureus and MRSA among United States adults. We conducted a cross-sectional analysis of a nationally representative sample of 7832 adults (20 years or older). The main outcome variables were nasal colonization with S aureus and MRSA. Percentages of colonization with S aureus and MRSA were calculated by the quartiles of serum homocysteine. A total of 7832 of 2051 subjects (26.2%) were culture positive for S aureus, 98 (4.8%) of whom had nasal colonization with MRSA. In comparison with subjects having the lowest serum homocysteine, the odds of nasal colonization with MRSA were significantly higher in those with the highest homocysteine (odds ratio, 3.09; 95% confidence interval, 1.11-8.61) in multivariate analysis, adjusted for all confounding variables. By contrast, homocysteine elevation was not significantly associated with S aureus colonization. Nasal colonization with MRSA in the general community was significantly associated with increases in serum homocysteine levels.

Sexual dimorphism in bacterial infections

Background

Sex differences are important epidemiological factors that impact in the frequency and severity of infectious diseases. A clear sexual dimorphism in bacterial infections has been reported in both humans and animal models. Nevertheless, the molecular mechanisms involved in this gender bias are just starting to be elucidated. In the present article, we aim to review the available data in the literature that report bacterial infections presenting a clear sexual dimorphism, without considering behavioral and social factors.

Main body

The sexual dimorphism in bacterial infections has been mainly attributed to the differential levels of sex hormones between males and females, as well as to genetic factors. In general, males are more susceptible to gastrointestinal and respiratory bacterial diseases and sepsis, while females are more susceptible to genitourinary tract bacterial infections. However, these incidences depend on the population evaluated, animal model and the bacterial species. Female protection against bacterial infections and the associated complications is assumed to be due to the pro-inflammatory effect of estradiol, while male susceptibility to those infections is associated with the testosterone-mediated immune suppression, probably via their specific receptors. Recent studies indicate that the protective effect of estradiol depends on the estrogen receptor subtype and the specific tissue compartment involved in the bacterial insult, suggesting that tissue-specific expression of particular sex steroid receptors contributes to the susceptibility to bacterial infections. Furthermore, this gender bias also depends on the effects of sex hormones on specific bacterial species. Finally, since a large number of genes related to immune functions are located on the X chromosome, X-linked mosaicism confers a highly polymorphic gene expression program that allows women to respond with a more expanded immune repertoire as compared with men.

Conclusion

Notwithstanding there is increasing evidence that confirms the sexual dimorphism in certain bacterial infections and the molecular mechanisms associated, further studies are required to clarify conflicting data and to determine the role of specific hormone receptors involved in the gender bias of bacterial infections, as well as their potential as therapeutic targets.

Treating Central Catheter-Associated Bacteremia Due to Methicillin-Resistant Staphylococcus aureus: Beyond Vancomycin

Methicillin-resistant Staphylococcus aureus is a frequent cause of hospital-associated infections, including central catheter-associated bacteremia. Vancomycin has been the drug of choice for treating this type of bacteremia for decades in patients who have no contraindications to the antibiotic. However, resistance to vancomycin is an emerging problem. Newer antibiotics approved by the Food and Drug Administration have activity against methicillin-resistant S aureus Some of the antibiotics also have activity against strains of S aureus that are intermediately susceptible or resistant to vancomycin. This article uses a case study to highlight the clinical signs of vancomycin failure and describes the indications for and appropriate use of alternative antimicrobials such as ceftaroline, daptomycin, linezolid, tigecycline, and telavancin. (Critical Care Nurse 2016;36[4]:46-57).

Ex Vivo Tracer Efficacy in Optical Imaging of Staphylococcus Aureus Nuclease Activity

The key to effective treatment of bacterial infections is a swift and reliable diagnosis. Current clinical standards of bacterial diagnosis are slow and laborious. There are several anatomical imaging modalities that can detect inflammation, but none can distinguish between bacterial and sterile inflammation. Novel tracers such as smart activatable fluorescent probes represent a promising development that allow fast and specific testing without the use of ionizing radiation. Previously, a smart activatable probe was developed that is a substrate for the micrococcal nuclease as produced by Staphylococcus aureus. In the present study, the function of this probe was validated. Practical applicability in terms of sensitivity was assessed by incubation of the probe with 26 clinical S. aureus isolates, and probe specificity was verified by incubation with 30 clinical isolates and laboratory strains of various bacterial pathogens. The results show that the nuclease-specific probe was activated by all tested S. aureus isolates and laboratory strains with a threshold of ~106-107 cells/mL. The probe was also activated by certain opportunistic staphylococci. We therefore propose that the studied nuclease probe represents a significant step forward to address the need for a rapid, practical, and precise method to detect infections caused by S. aureus.

Hospital-associated methicillin-resistant Staphylococcus aureus: A cross-sectional analysis of risk factors in South African tertiary public hospitals

Introduction

Hospital-associated methicillin-resistant S. aureus (HA-MRSA) remains a significant cause of morbidity and mortality worldwide. We conducted a study to determine risk factors for HA-MRSA in order to inform control strategies in South Africa.

Methods

We used surveillance data collected from five tertiary hospitals in Gauteng and Western Cape provinces during 2014 for analysis. A case of HA-MRSA was defined as isolation of MRSA from a blood culture 48 hours after admission and/or if the patient was hospitalised in the six months prior to the current culture. Multivariable logistic regression modelling was used to determine risk factors for HA-MRSA.

Results

Of the 9971 patients with positive blood cultures, 7.7% (772) had S. aureus bacteraemia (SAB). The overall prevalence of MRSA among those with SAB was 30.9% (231/747; 95% confidence interval [CI] 27.6%– 34.3%). HA-MRSA infections accounted for 28.3% of patients with SAB (207/731; 95% CI 25.1%– 31.7%). Burns (adjusted odds ratio [aOR] 12.7; 95% CI 4.7–34.4), age ≤1 month (aOR 8.7; 95% CI 3.0–24.6), residency at a long-term care facility (aOR 5.2; 95% CI, 1.5–17.4), antibiotic use within two months of the current SAB episode (aOR 5.1; 95% CI 2.8–9.1), hospital stay of 13 days or more (aOR 2.8; 95% CI 1.3–5.6) and mechanical ventilation (aOR 2.2; 95% CI 1.07–4.6), were independent risk factors for HA-MRSA infection.

Conclusion

The prevalence of MRSA remains high in South African tertiary public hospitals. Several identified risk factors of HA-MRSA infections should be considered when instituting infection and prevention strategies in public-sector hospitals, including intensifying the implementation of antimicrobial stewardship programmes. There is an urgent need to strengthen infection prevention and control in burn wards, neonatal wards, and intensive care units which house mechanically ventilated patients.

[Risk factors for methicillin-resistant Staphylococcus aureus bacteremia: A multicenter matched case-control study]

INTRODUCTION

Methicillin-resistant Staphylococcus aureus is a frequent pathogen at critical care services. Its presence leads to increased hospital stays and mortality risk in patients with bacteremia. However, the etiology of this resistance marker has not been fully studied.

OBJECTIVE

To identify risk factors associated with the emergence of methicillin-resistant S. aureus bacteremia in critically ill patients treated at intensive care units in Bogotá, Colombia.

MATERIALS AND METHODS

We conducted a retrospective paired case-control study, nested in a cohort of patients diagnosed with S. aureus bacteremia and treated at intensive care units between 2006 and 2008 in Bogotá. Cases were patients with positive blood culture to methicillin resistance, matched in a 1:1 ratio with methicillin-sensitive controls isolated from the same institution and hospitalization year. We used conditional logistic regression to analyze the risk factors associated with the presence of resistance, with emphasis on prior antibiotic therapy.

RESULTS

We included 372 patients with S. aureus bacteremia. Factors such as the use of pre-hospital devices: vascular (OR=1.986, 95% CI 1.038 to 3.801) and urinary (OR=2.559, 95% CI: 1.170 to 5.596), along with the number of previously used antibiotics, were associated with the emergence of resistance. The number of antibiotics used previously was determined to have a gradient effect, particularly carbapenems.

CONCLUSIONS

The rational use of antibiotics and surveillance of exposure to surgical procedures or use of invasive devices are interventions that could diminish the emergence of methicillin-resistant S. aureus bacteremia causes.

Trimethoprim-sulfamethoxazole versus vancomycin for severe infections caused by meticillin resistant Staphylococcus aureus: randomised controlled trial

OBJECTIVE

To show non-inferiority of trimethoprim-sulfamethoxazole compared with vancomycin for the treatment of severe infections due to meticillin resistant Staphylococcus aureus (MRSA).

DESIGN

Parallel, open label, randomised controlled trial.

SETTING

Four acute care hospitals in Israel.

PARTICIPANTS

Adults with severe infections caused by MRSA susceptible to trimethoprim-sulfamethoxazole and vancomycin. Patients with left sided endocarditis, meningitis, chronic haemodialysis, and prolonged neutropenia were excluded.

INTERVENTIONS

Trimethoprim-sulfamethoxazole 320 mg/1600 mg twice daily versus vancomycin 1 g twice daily for a minimum of seven days and then by indication.

MAIN OUTCOME MEASURES

The primary efficacy outcome was treatment failure assessed at day 7, consisting of death, persistence of haemodynamic instability or fever, stable or worsening Sequential Organ Failure Assessment score, and persistence of bacteraemia. The primary safety outcome was all cause mortality at day 30. Non-inferiority was defined by a difference of less than 15% for treatment failure.

RESULTS

252 patients were included in the trial, of whom 91 (36%) had bacteraemia. No significant difference in treatment failure was seen for trimethoprim-sulfamethoxazole (51/135, 38%) versus vancomycin (32/117, 27%)-risk ratio 1.38 (95% confidence interval 0.96 to 1.99). However, trimethoprim-sulfamethoxazole did not meet the non-inferiority criterion-absolute difference 10.4% (95% confidence interval -1.2% to 21.5%). For patients with bacteraemia, the risk ratio was 1.40 (0.91 to 2.16). In a multivariable logistic regression analysis, trimethoprim-sulfamethoxazole was significantly associated with treatment failure (adjusted odds ratio 2.00, 1.09 to 3.65). The 30 day mortality rate was 32/252 (13%), with no significant difference between arms. Among patients with bacteraemia, 14/41 (34%) treated with trimethoprim-sulfamethoxazole and 9/50 (18%) with vancomycin died (risk ratio 1.90, 0.92 to 3.93).

CONCLUSIONS

High dose trimethoprim-sulfamethoxazole did not achieve non-inferiority to vancomycin in the treatment of severe MRSA infections. The difference was particularly marked for patients with bacteraemia. Trial registration Clinical trials NCT00427076.

Multifunctional Au nanoclusters for targeted bioimaging and enhanced photodynamic inactivation of Staphylococcus aureus

A novel nanocluster platform is developed to combine intense red fluorescence of Au₂₅–BSA nanoclusters (QY ∼ 14%), biospecific binding to S. aureus due to human antistaphylococcal IgG, and photodynamic inactivation due to photosensitizer Photosens™.

Staphylococcus aureus bacteraemia in Gauteng academic hospitals, South Africa

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) infections are responsible for longer hospital stays, increased hospital costs, and poorer outcomes compared to methicillin-sensitive S. aureus (MSSA) infections. We aimed to describe the epidemiology of S. aureus bacteraemia (SAB) and to determine factors associated with MRSA infection in South Africa.

METHODS

Cases of SAB were reported from September 2012 to September 2013 from three sentinel sites. A case was defined as the isolation of S. aureus from a blood culture during a 21-day period. Detailed clinical information was collected. Multivariable logistic regression was done to determine factors associated with MRSA infection and mortality.

RESULTS

There were 442 cases of SAB reported; antimicrobial susceptibility testing was performed on 240 isolates (54%). Thirty-six percent (86/240) of cases had an MRSA infection. A longer hospital stay before positive specimen collection (odds ratio (OR) 1.08, 95% confidence interval (CI) 1.02-1.13, p=0.004), hospitalization in the last year (OR 15.7, 95% CI 2.5-99.5, p=0.003), HIV infection (OR 4.9, 95% CI 1.05-22.90, p=0.044), and antibiotic use in the previous 2 months (OR 0.1, 95% CI 0.01-0.68, p=0.022) were independent predictors of MRSA. Older age, and in particular age 25-44 years (OR 22.2, 95% CI 2.7-185.5, p=0.004, compared to those aged<5 years), was the only independent predictor of mortality amongst cases with SAB. MRSA isolates were non-susceptible to more antimicrobial agents compared to MSSA isolates.

CONCLUSIONS

HIV infection was an independent risk factor for MRSA infection. The selection of appropriate empirical antimicrobial treatment is essential in patients with MRSA infections because of non-susceptibility to many other antimicrobial classes.

In Vitro Antibacterial Activity, Gas Chromatography-Mass Spectrometry Analysis of Woodfordia fruticosa Kurz. Leaf Extract and Host Toxicity Testing With In Vitro Cultured Lymphocytes From Human Umbilical Cord Blood

Objectives

To locate a plant with suitable phytochemicals for use as antimicrobial agents to control multidrug-resistant (MDR) bacteria as a complementary medicine, without host toxicity as monitored through cultured lymphocytes from human umbilical cord blood.

Methods

The methanol crude leaf extract of the plant Woodfordia fruticosa was subjected to antimicrobial assay in vitro with nine pathogenic MDR bacteria from clinical samples. This was followed by bioassay-guided fractionation with seven non-polar to polar solvents, gas chromatography–mass spectrometry analysis of the n-butanol fraction, and monitoring of the host toxicity of the leaf extract with in vitro grown lymphocytes from human umbilical cord blood.

Results

The leaf extract of W. fruticosa had a controlling capacity for MDR bacteria. The minimum inhibitory concentration and minimum bactericidal concentration of the n-butanol fraction were < 1.89 mg/mL extract and 9.63 mg/mL extract, respectively. The gas chromatography–mass spectrometry spectrum of the n-butanol fraction confirmed the presence of 13 peaks of different compounds with retention times of 9.11 minutes, 9.72 minutes, 10.13 minutes, 10.78 minutes, 12.37 minutes, 12.93 minutes, 18.16 minutes, 21.74 minutes, 21.84 minutes, 5.96 minutes, 12.93 minutes, 24.70 minutes, and 25.76 minutes. The six leading compounds were: diethyl phthalate: IUPAC name: diethyl benzene-1,2-dicarboxylate; 5-methyl-2-(1-methylethyl) phenol: IUPAC name: 5-methyl-2-propan-2-ylphenol; (E )-3,7-dimethylocta-2,6-diene-1-thiol: IUPAC name: (2Z)-3,7-dimethylocta-2,6-diene-1-thiol; 2,6,10-dodecatrien-1-ol, 3,7,11-trimethyl-, (E,E ): IUPAC name: 2,6,10-dodecatrien-1-ol; 3,7,11-trimethyl-, (E,E); 2-methoxy-4-(2-propenyl) phenol: IUPAC name: 2-methoxy-4-[(1E)-prop-1-en-1-yl]phenol; hexadecanoic acid: IUPAC name: hexadecanoic acid.

Conclusion

The presence of antimicrobial compounds that are therapeutically potent against MDR bacteria was confirmed in W. fruticosa. The crude leaf extract showed no host toxicity with human lymphocytes; the n-butanol fraction of the extract was the most suitable bioactive fraction. The terpenes isolated were: 5-methyl-2-(1-methylethyl) phenol, 2-methoxy-4-(2-propenyl) phenol, 2,6-octadien-1-ol, 3,7-dimethyl-(E)-2,6-octadienal, 3,7-dimethylcyclohexanol, and cyclohexanol, 2-methylene-5-(1-methylethenyl) which were reported to have specifically antimicrobial activity.

Enhanced photoinactivation of Staphylococcus aureus with nanocomposites containing plasmonic particles and hematoporphyrin

We fabricated composite nanoparticles consisting of a plasmonic core (gold nanorods or gold-silver nanocages) and a hematoporphyrin-doped silica shell. The dual photodynamic and photothermal activities of such nanoparticles against Staphylococcus aureus 209 P were studied and compared with the activities of reference solutions (hematoporphyrin or silica-coated plasmonic nanoparticles). Bacteria were incubated with nanocomposites or with the reference solutions for 15 min, which was followed by CW light irradiation with a few exposures of 5 to 30 min. To stimulate the photodynamic and photothermal activities of the nanocomposites, we used LEDs (405 and 625 nm) and a NIR laser (808 nm), respectively. We observed enhanced inactivation of S. aureus 209 P by nanocomposites in comparison with the reference solutions. By using fluorescence microscopy and spectroscopy, we explain the enhanced antimicrobial effect of hematoporphyrin-doped nanocomposites by their selective accumulation in the vicinity of the bacteria.

Staphylococcus aureus extracellular adherence protein triggers TNFα release, promoting attachment to endothelial cells via protein A

Staphylococcus aureus is a leading cause of bacteraemia, which frequently results in complications such as infective endocarditis, osteomyelitis and exit from the bloodstream to cause metastatic abscesses. Interaction with endothelial cells is critical to these complications and several bacterial proteins have been shown to be involved. The S. aureus extracellular adhesion protein (Eap) has many functions, it binds several host glyco-proteins and has both pro- and anti-inflammatory activity. Unfortunately its role in vivo has not been robustly tested to date, due to difficulties in complementing its activity in mutant strains. We previously found Eap to have pro-inflammatory activity, and here show that purified native Eap triggered TNFα release in whole human blood in a dose-dependent manner. This level of TNFα increased adhesion of S. aureus to endothelial cells 4-fold via a mechanism involving protein A on the bacterial surface and gC1qR/p33 on the endothelial cell surface. The contribution this and other Eap activities play in disease severity during bacteraemia was tested by constructing an isogenic set of strains in which the eap gene was inactivated and complemented by inserting an intact copy elsewhere on the bacterial chromosome. Using a murine bacteraemia model we found that Eap expressing strains cause a more severe infection, demonstrating its role in invasive disease.

[Interest of real-time PCR Xpert MRSA/SA on GeneXpert(®) DX System in the investigation of staphylococcal bacteremia]

AIM OF THE STUDY

Recently, a rapid, fully automated real-time PCR test has become available for detection of Staphylococcus aureus in positive blood cultures, Xpert MRSA/SA blood culture. This study was defined to evaluate the use of this product in our hospital setting to assist in optimizing antibiotic treatment.

MATERIALS AND METHODS

Over a period of 18months (from February 2008 to July 2009), 51 positive blood cultures were examined for Staphylococcus using the Xpert MRSA/SA assay on the GeneXpert(®) System. The PCR results were transferred to the clinician as soon as available. The presence of empirical antibiotic therapy was noted and modified if necessary after discussions between the clinician and the infectious disease specialist.

RESULTS

Twenty-three blood bottles were positive for S. aureus, two were resistant to methicillin. Twenty-eight were coagulase negative staphylococci. No discrepancy between identification (S. aureus) and methicillin resistance was observed. Thirty-two samples had clinically significant bacteremia (23 S. aureus and nine coagulase negative staphylococci). Sixteen (50%) of these patients had received inappropriate antibiotic therapy (11 without antibiotic therapy, five with betalactam antibiotics). For these patients, an appropriate antibiotic therapy was prescribed according to these results. Sixteen patients had adequate empirical antibiotic therapy at the time of receiving the PCR result. Among these 16 patients, eight switches were performed from broad-spectrum treatment to a more restrictive antistaphylococcal treatment. Of the 19 patients with a nonclinically relevant coagulase negative staphylococci infection, four were already on antibiotics for other infections and these treatments were not modified. Empirical treatment could be avoided in 13 patients who had a clinical presentation consistent with staphylococcal bacteremia (multiple sores, history of carrying methicllin-resistant or susceptible S. aureus infection, presence of intravascular material or prosthesis).

CONCLUSION

The real-time PCR Cepheid Xpert MRSA/SA on GeneXpert(®) DX System has become an essential tool in our laboratory enhancing the reports of positive blood cultures for staphylococci. This test is fast (50min) and reliable. It allows optimization of antibiotic therapy in hospital.

Risk factors associated with methicillin-resistant Staphylococcus aureus colonization on hospital admission among oncology patients

A nested case-control study at a tertiary care facility was conducted to assess potential risk factors for colonization with methicillin-resistant Staphylococcus aureus (MRSA) on admission among oncology patients. Risk factors for any S aureus and MRSA colonization on admission in oncology patients are consistent with previous studies in general populations. In addition, recent chemotherapy as a risk factor is a unique finding in this population.

Methicillin-resistant Staphylococcus aureus in orthopaedic surgery

Methicillin-resistant Staphylococcus aureus (MRSA) has become a ubiquitous bacterium in both the hospital and community setting. There are two major subclassifications of MRSA, community-acquired and healthcare-acquired, each with differing pathogenicity and management. MRSA is increasingly responsible for infections in otherwise healthy, active adults. Local outbreaks affect both professional and amateur athletes and there is increasing public awareness of the issue. Health-acquired MRSA has major cost and outcome implications for patients and hospitals. The increasing prevalence and severity of MRSA means that the orthopaedic community should have a basic knowledge of the bacterium, its presentation and options for treatment. This paper examines the evolution of MRSA, analyses the spectrum of diseases produced by this bacterium and presents current prevention and treatment strategies for orthopaedic infections from MRSA.

[MRSA and MSSA infections in patients operated on for head and neck cancers]

INTRODUCTION

The MRSA and MSSA infections are essential clinical problem. Both of the strains have high virulence (as a result of enzyme and toxin production), what disturbs wound healing as well as a general condition of the patient.

AIM

The purpose of this work was an estimation of the role of MRSA infections among patients operated on for head and neck cancers.

MATERIAL AND METHODS

From 1155 patients treated for head and neck cancers in The Department of Otolaryngology in Poznan in 2006-2007 189 biological samples were taken to carry out a bacteriological examination. The indications for this procedure were symptoms of infection in the operated area, wound healing per secundam and a hectic fever after the surgery. Biological specimens came from: 57 postoperative wounds, 36 tracheotomy areas, 24 tracheoesophageal fistulas, 9 salivary fistulas, 21 oral cavities and pharynxes, 2 noses, 4 ears, 6 central venous catheter areas, 2 gastrostomies, 2 cerebrospinal fluid (CSF) samples, 1 fluid from pleural cavity, 11 blood samples, 12 urine samples, 2 bronchoalveolar lavages (BAL).

RESULTS

37 biological samples were aseptic, in 11 samples there were no pathological cultures, in 141 samples pathological bacterial flora was found. MRSA was found in 6 cultures and MSSA was found in 18 cultures.

CONCLUSIONS

In order to prevent the MRSA infection the Hospital Infections Department was formed. The results of commissioned bacteriological examinations are analyzed by the Department, what enables bacteriological flora observation in the hospital, fast identification of MRSA infected patients, and, what is more, MRSA infections prevention. It also helps to select proper medicaments in empiric antibiotic therapy.

The effect of posters and displays on the use of alcohol gel

Introduction: Hand cleansing with alcohol gel is important in reducing health care associated infection (HCAI). HCAI affects 8% of acute hospital admissions in the UK costing the NHS an estimated ®1 billion per annum1. The aim of this study was to determine the effect of posters and placement of alcohol dispensers on use of alcohol dispensers by staff and visitors passing through hospital foyers.

Method: We noted the use of alcohol gel for hand cleansing in pedestrians entering through the hospital foyers. Three scenarios were noted:

■ Display 1. Poster and gel dispenser in the centre of the foyer.

■ Display 2. Poster and gel dispenser on the wall of the foyer.

■ Display 3. No poster with a gel dispenser on the wall of the foyer.

Results: For display 1 uptake of alcohol gel was 38.4%, for display 2 it was 8.6% and for display 3 it was 2.7%. There was a significant increase in uptake of alcohol hand cleansing when a display was used (p > 0.001). Regarding gender, males were better users of alcohol hand gel overall. Employment group: the highest use was amongst female visitors with display 1 (51.6%). Displays had least influence on male doctors (44% with display 1, 10% with display 3).

Conclusion: We recommend the use of prominently placed posters and gel dispensers in hospital foyers.

The incidence of and risk factors for MRSA bacteraemia in an HIV-infected cohort in the HAART era

OBJECTIVES

To define the incidence and risk factors for methicillin resistant Staphylococcus aureus (MRSA) bacteraemia in an HIV-infected population.

METHODS

From January 1, 2000 to December 31, 2004, we conducted a retrospective cohort study. We identified all cases of Staphylococcus aureus bacteraemia (SAB), including MRSA, among patients enrolled in the Johns Hopkins Hospital out-patient HIV clinic. A conditional logistic regression model was used to identify risk factors for MRSA bacteraemia compared with methicillin-sensitive SAB and no bacteraemia in unmatched (1:1) and matched (1:4) nested case-control analyses, respectively.

RESULTS

Of 4607 patients followed for a total of 11 020 person-years (PY) of follow-up, 216 episodes of SAB occurred (incidence: 19.6 cases per 1000 PY), including 94 cases (43.5%) which were methicillin-resistant. The incidence of MRSA bacteraemia increased from 5.3 per 1000 PY in 2000-2001 to 11.9 per 1000 PY in 2003-2004 (P=0.001). Multivariate analysis demonstrated that independent predictors of MRSA bacteraemia (vs. no bacteraemia) were injection drug use (IDU), end-stage renal disease (ESRD) and CD4 count <200 cells/microL.

CONCLUSIONS

MRSA bacteraemia was an increasingly common diagnosis in our HIV-infected cohort, especially in patients with history of IDU, low CD4 cell count and ESRD.

Pediatric bone and joint infections caused by Panton-Valentine leukocidin-positive Staphylococcus aureus

BACKGROUND

Panton-Valentine leukocidin (PVL) is a necrotizing toxin secreted by Staphylococcus aureus. PVL-positive S. aureus osteomyelitis and arthritis have been described.

METHODS

We analyzed demographic, clinical, laboratory, microbiologic, and imaging data in a study group of 14 pediatric cases with PVL-positive S. aureus osteomyelitis and arthritis diagnosed between 2001 and 2005 and compared results with a control group of 17 pediatric cases of PVL-negative S. aureus osteomyelitis and arthritis treated in our institution during the same period. Treatments and outcome were studied.

RESULTS

The severity of PVL-positive S. aureus bone and joint infections was indicated by the presence of severe sepsis in all cases and of septic shock in 6 of the 14 patients. By comparison, severe sepsis was not noted in the control group (P = 0.004). On admission, the median C-reactive protein value was significantly higher in the study group (202.6 mg/L versus 83 mg/L in the control group; P = 0.001). Eleven patients with PVL-positive infection had local extension of the infection by magnetic resonance imaging and 7 patients had severe deep-seated infectious complications by computed tomography. By contrast only 1 patient in the control group presented with bone abscess without extension and none had deep-seated infection (P < 0.001). The median length of hospitalization was 45.5 days in the study group versus 13 days in the control group (P < 0.001). The median duration of intravenous antibacterial chemotherapy was 48 days versus 11.3 days in the control group (P < 0.001). Ten patients (71%) of the study group required surgical procedures with a mean of 3 procedures (range, 1-5) whereas 3 patients (17%) of the control group required 1 surgical drainage each (P = 0.002). All the patients survived, but only 2 patients of the study group were free of long-term complications, whereas there were no long-term complications noted in the control group.

CONCLUSION

PVL-positive S. aureus bone and joint infection is severe and requires prolonged treatment. Local complications are more frequent and often need repeated surgical drainage.

Predictors of asking medical personnel about handwashing: the moderating role of patients' age and MRSA infection status

OBJECTIVE

The study investigates patients' behaviours protective of methicillin-resistant Staphylococcus aureus (MRSA), asking doctors and nurses about handwashing before examination, and its relations with the Theory of Planned Behaviour (TPB) variables and knowledge. We expected that MRSA infection status and age might moderate relations between the behaviour and its predictors.

METHODS

A total of 171 individuals (59% with MRSA; 54% of 65 years or older) who had contact with the Patients Association and MRSA Support groups filled out questionnaires.

RESULTS

Across the groups beliefs about ability to control own behaviour were the best predictors of intention and behaviour, except for non-MRSA patients older than 65 years, for whom knowledge about MRSA infection remained the sole predictor of behaviour. The amount of explained variance of behaviour was twice as high among younger patients compared to older ones.

CONCLUSIONS

The study indicates limitations of the predictive value of the TPB among older patients. The results support the importance of beliefs about ability to control own behaviour in predicting an error-preventive action.

PRACTICE IMPLICATIONS

Enhancing control beliefs may promote asking medical personnel about handwashing. Interventions aiming MRSA prevention should target different cognitions or knowledge depending on patients' age and MRSA infection status.

Empirical antimicrobial treatment for chemotherapy-induced febrile neutropenia

Febrile neutropenia in immunocompromised hosts is associated with a high mortality. Empirical treatment in such cases is instituted to cover the common pathogens. Generally, combination antibiotic treatment is used early in the febrile neutropenia phase. Recent studies demonstrate that monotherapy with certain beta-lactam antibiotics can be equally effective. Glycopeptide antibiotics are used in the absence of an adequate response to the initial antibiotics. Empirical antifungal therapy may be given if fever does not settle in 72-96 h despite antibiotics. Newer antifungal agents have increased the available options for initial antifungal agents though more data are needed before any conclusive recommendation can be made. Recent changes in the epidemiology of multiresistant organisms necessitate local microbiological input into empiric policies with increasing need to consider cover for methicillin-resistant Staphylococcus aureus, glycopeptide intermediate S. aureus, vancomycin-resistant S. aureus, vancomycin-resistant enterococci, Gram-negative bacilli that produce extended-spectrum beta-lactamases, Stenotrophomonas maltophilia, and multi-resistant Acinetobacter baumanii.