A comparison of clinical features and mortality among methicillin-resistant and methicillin-sensitive strains of Staphylococcus aureus endocarditis

Is It Useful to Repeat Blood Cultures in Endocarditis Patients? A Critical Appraisal

BACKGROUND

Previous guidelines for endocarditis have suggested repeating blood cultures until they become negative, with limited evidence.

METHODS

Literature reviews were conducted (1) on the incidence of persistent bacteremia and association with outcome and (2) on timing of valve culture negativization to examine the claim for prolongation of antibiotic therapy starting from negative blood cultures.

RESULTS

Persistent bacteremia and fever may be present in the first 3 days of endocarditis, despite treatment, and are more common in Staphylococcus (especially MRSA) and Enterococcus species. Persistent bacteremia (48-72 h), persistent infection (day 7), and new onset septic shock are related and predict in-hospital mortality. It is, however, persistent infection at day 7 and septic shock that primarily determine the infectious course of endocarditis, and not persistent bacteremia. Valve cultures at surgery become negative in most cases (>85-90%) after 14-21 days of antibiotic therapy, with no calculated benefit for prolonging therapy after 21 days.

CONCLUSIONS

Persistent infection at 7 days after appropriate antibiotic therapy is a better key event for prognosis then positive or negative blood cultures at 48-72 h. Therapy prolongation from the day of negative blood cultures is not reasonable. There is no need to survey blood cultures in endocarditis patients after starting therapy.

Efficacy and clinical potential of phage therapy in treating methicillin-resistant Staphylococcus aureus (MRSA) infections: A review

Staphylococcus aureus infections have already presented a substantial public health challenge, encompassing different clinical manifestations, ranging from bacteremia to sepsis and multi-organ failures. Among these infections, methicillin-resistant S. aureus (MRSA) is particularly alarming due to its well-documented resistance to multiple classes of antibiotics, contributing significantly to global mortality rates. Consequently, the urgent need for effective treatment options has prompted a growing interest in exploring phage therapy as a potential non-antibiotic treatment against MRSA infections. Phages represent a class of highly specific bacterial viruses known for their ability to infect certain bacterial strains. This review paper explores the clinical potential of phages as a treatment for MRSA infections due to their low toxicity and auto-dosing capabilities. The paper also discusses the synergistic effect of phage-antibiotic combination (PAC) and the promising results from in vitro and animal model studies, which could lead to extensive human clinical trials. However, clinicians need to establish and adhere to standard protocols governing phage administration and implementation. Prominent clinical trials are needed to develop and advance phage therapy as a non-antibiotic therapy intervention, meeting regulatory guidelines, logistical requirements, and ethical considerations, potentially revolutionizing the treatment of MRSA infections.

Comparison of mortality, stroke, and relapse for methicillin-resistant versus methicillin-susceptible Staphylococcus aureus infective endocarditis: a retrospective cohort study

The purpose of this study was to compare survival, relapse, and stroke for patients with methicillin-resistant Staphylococcus aureus (MRSA) vs methicillin-susceptible S. aureus (MSSA) infective endocarditis (IE). In this retrospective study, the primary outcome of death and secondary outcomes of stroke and relapse were compared using multivariable Cox proportional hazards regression. Surgical treatment was adjusted for as a time-dependent variable. In total, 355 patients with at least one episode of IE caused by S. aureus were included. Patients with MRSA IE had higher mortality than those with MSSA IE (HR 1.34, 95% CI 1.01-1.77), but did not have a higher risk of stroke (HR 0.75, 95% CI 0.43-1.32) or relapse (HR 0.89, 95% CI 0.26-3.05). The cumulative incidence of relapse was very small. Among patients with IE caused by S. aureus MRSA infection is associated with higher mortality than MSSA infection.

In-Hospital and Long-Term Outcomes of Infective Endocarditis in Chronic Dialysis Patients

Purpose

To elucidate the in-hospital and long-term outcomes of infective endocarditis (IE) in end-stage kidney disease (ESKD) patients on chronic dialysis and to analyze the risk factors of mortality.

Patients and Methods

The case files of 1,817 patients who were hospitalized for IE over a 14-year period were retrospectively reviewed. Of these, 116 ESKD patients on chronic dialysis were enrolled in this study. Cox’s proportional hazard model was used to evaluate the risk factors of mortality and long-term outcomes.

Results

The in-hospital mortality rate of the 116 enrolled patients was as high as 43.1%. Patients who survived the index admission had a three-year mortality rate of 33%. Univariate analysis was used to compare survivors and non-survivors; poor in-hospital outcomes were associated with the use of a tunneled cuffed catheter for dialysis access, a shorter duration hospitalization, shock or respiratory failure during hospitalization, a higher white blood count, a higher percentage of polymorphonuclear leukocytes, a higher C-reactive protein level, a lower serum albumin level, and a higher total bilirubin level. Following multivariate adjustment, shock (odds ratio, 9.29, with a 95% confidence interval [CI] of 2.78 to 34.24; p<0.001) or respiratory failure (odds ratio, 25.16, with a 95% CI of 5.63 to 153.54; p<0.001) during hospitalization was strongly associated with increased in-hospital mortality. Patients who underwent cardiac operations (odds ratio, 0.22, with a 95% CI of 0.052 to 0.86; p=0.031) had better in-hospital outcomes. Heart failure reduced ejection fraction (HFrEF) at the time of initial hospitalization was an independent risk factor for 3-year mortality (hazard ratio, 3.48, with a 95% CI of 1.09 to 11.09; p=0.035).

Conclusion

The outcomes of IE for ESKD patients on chronic dialysis were poor. Only 56.9% of these patients survived the index admission and their mortality rate over three years was 33%. Shock or respiratory failure during hospitalization was associated with increased in-hospital mortality. Patients who underwent cardiac operations had better in-hospital outcomes. HFrEF at the time of initial hospitalization was an independent risk factor for three-year mortality.

Reevaluation of the impact of methicillin-resistance on outcomes in patients with Staphylococcus aureus bacteremia and endocarditis

BACKGROUND/AIMS

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in hospitals, and has recently emerged in the community. The impact of methicillin-resistance on mortality and medical costs for patients with S. aureus bacteremia (SAB) requires reevaluation.

METHODS

We searched studies with SAB or endocarditis using electronic databases including Ovid-Medline, Embase-Medline, and Cochrane Library, as well as five local databases for published studies during the period January 2000 to September 2011.

RESULTS

A total of 2,841 studies were identified, 62 of which involved 17,563 adult subjects and were selected as eligible. A significant increase in overall mortality associated with MRSA, compared to that with methicillin-susceptible S. aureus (MSSA), was evidenced by an odds ratio (OR) of 1.95 (95% confidence interval [CI], 1.73 to 2.21; p < 0.01). In 13 endocarditis studies, MRSA increased the risk of mortality, with an OR of 2.65 (95% CI, 1.46 to 4.80). When three studies, which compared mortality rates between CA-MRSA and CA-MSSA, were combined, the risk of methicillin-resistance increased 3.23-fold compared to MSSA (95% CI, 1.25 to 8.34). The length of hospital stay in the MRSA group was 10 days longer than that in the MSSA group (95% CI, 3.36 to 16.70). Of six studies that reported medical costs, two were included in the analysis, which estimated medical costs to be $9,954.58 (95% CI, 8,951.99 to 10,957.17).

CONCLUSION

MRSA is still associated with increased mortality, longer hospital stays and medical costs, compared with MSSA in SAB in studies published since the year 2000.

A successful salvage therapy with daptomycin and linezolid for right-sided infective endocarditis and septic pulmonary embolism caused by methicillin-resistant Staphylococcus aureus

Although vancomycin administration is recommended for the treatment of infective endocarditis (IE) caused by methicillin-resistant Staphylococcus aureus (MRSA), it is unclear whether an alternative agent, daptomycin, can be used to treat IE with pulmonary complications. A 26-year-old female who had undergone surgical repair of a ventricular septal defect as an early teenager presented with fever, headache, and vomiting. She was admitted to our hospital and diagnosed with right-sided IE with septic pulmonary embolism caused by MRSA. Vancomycin, rifampicin, and gentamicin were administered; however, exacerbation of drug eruption due to the antimicrobial agents on the 11th day led us to switch from vancomycin and rifampicin to daptomycin. Furthermore, we included linezolid to treat lung abscesses that accompanied the septic pulmonary embolism. We confirmed negative blood cultures on the 18th day. On the same day, a patch closure for the ventricular septal defect and tricuspid valve replacement were performed. She was discharged on the 65th day with an uneventful postoperative course. This experience suggests that daptomycin and linezolid are effective salvage therapies for right-sided IE caused by MRSA and accompanied by pulmonary complications.

A Comparison of Administrative Data Versus Surveillance Data for Hospital-Associated Methicillin-Resistant Staphylococcus aureus Infections in Canadian Hospitals

BACKGROUND In Canadian hospitals, clinical information is coded according to national coding standards and is routinely collected as administrative data. Administrative data may complement active surveillance programs by providing in-hospital MRSA infection data in a standardized and efficient manner, but only if infections are accurately captured. OBJECTIVE To assess the accuracy of administrative data regarding in-hospital bloodstream infections (BSIs) and all-body-site infections due to MRSA. METHODS A retrospective study of all (adult and pediatric) in-hospital MRSA infections was conducted by comparing administrative data against surveillance data from 217 acute Canadian hospitals (124 in Ontario, 93 in Alberta) over a 12-month period. Hospital-associated MRSA BSI cases in Ontario, and for all-body-site MRSA infections in Alberta were identified. Pearson correlation coefficients were used to compare the number of hospital-level MRSA cases within administrative versus surveillance datasets. The correlation of all-body-site MRSA infections versus MRSA BSIs was also assessed using the Ontario administrative data. RESULTS Strong correlations between hospital-level MRSA cases in administrative and surveillance datasets were identified for Ontario (r=0.79; 95% CI, 0.72-0.85) and Alberta (r=0.92; 95% CI, 0.88-0.94). A strong correlation between all-body-site and bloodstream-only MRSA infection rates was identified across Ontario hospitals (r=0.95; P<.0001; 95% CI, 0.93-0.96). CONCLUSIONS This study provides good evidence of the comparability of administrative and surveillance datasets in identifying in-hospital MRSA infections. With standard definitions, administrative data can provide estimates of in-hospital infections for monitoring and/or comparisons across hospitals. Infect Control Hosp Epidemiol 2017;38:436-443.

Screening and treatment for Staphylococcus aureus in patients undergoing hemodialysis: a systematic review and meta-analysis

BACKGROUND

This study was performed to evaluate the effectiveness of surveillance for screening and treatment of patients with chronic kidney disease undergoing hemodialysis and colonized by Staphylococcus aureus.

METHODS

A systematic review and meta-analysis were performed. The literature search involved the following databases: the Cochrane Controlled Trials Register, Embase, LILACS, CINAHL, SciELO, and PubMed/Medline. The descriptors were "Staphylococcus aureus", "MRSA", "MSSA", "treatment", "decolonization", "nasal carrier", "colonization", "chronic kidney disease", "dialysis", and "haemodialysis" or "hemodialysis". Five randomized controlled trials that exhibited agreement among reviewers as shown by a kappa value of >0.80 were included in the study; methodological quality was evaluated using the STROBE statement. Patients who received various treatments (various treatments group) or topical mupirocin (mupirocin group) were compared with those who received either no treatment or placebo (control group). The outcomes were skin infection at the central venous catheter insertion site and bacteremia.

RESULTS

In total, 2374 patients were included in the analysis, 626 (26.4%) of whom were nasal carriers of S. aureus. The probability of S. aureus infection at the catheter site for hemodialysis was 87% lower in the mupirocin group than in the control group (odds ratio [OR], 0.13; 95% confidence interval [CI], 0.05-0.34; p<0.001). The risk of bacteremia was 82% lower in the mupirocin group than in the control group (OR, 0.18; 95% CI, 0.08-0.42; p<0.001). No statistically significant difference in bacteremia was observed between the various treatments group (excluding mupirocin) and the control group (OR, 0.77; 95% CI, 0.51-1.15; p=0.20).

CONCLUSIONS

Twenty-six percent of patients undergoing hemodialysis were nasal carriers of S. aureus. Of all treatments evaluated, topical mupirocin was the most effective therapy for the reduction of S. aureus catheter site infection and bacteremia in patients undergoing chronic hemodialysis.

Comparison of clinical features and outcomes of staphylococcus aureus vertebral osteomyelitis caused by methicillin-resistant and methicillin-sensitive strains

The causative organism of vertebral osteomyelitis (VO) was almost exclusively Staphylococcus aureus. The purpose of this study was to delineate the differences in clinical features and outcomes between patients with methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) VO. This study retrospectively reviewed 85 consecutive patients with VO treated between 2005 and 2011. Surgical site infections were excluded. Diagnosis was made by cultures of either blood or biopsied samples. We identified 16 cases of MRSA VO and 14 cases of MSSA VO. The average follow-up period was 18.5 months. Clinical features and outcomes were analyzed. Males were more likely to have MRSA VO than MSSA VO (87.5% vs. 35.7%). In regards to the number of co-morbidities, patients with MRSA VO had significantly more co-mobidities than patients with MSSA VO. Additionally, the rate of patients who underwent surgical procedure (excluding spinal surgeries in the affected region) within 3 months were significantly higher in the MRSA VO group than the MSSA VO group (56.3% vs. 14.3%). White blood cell counts and C-reactive protein levels in patients with both strains significantly improved 4 weeks after the initial treatment compared with the pretreatment values. The recurrence rate within 6 months tended to be higher for MRSA VO (37.5% vs. 7.1%), but no significant difference in mortality was observed between the two VO types. In conclusion, male sex, multiple co-morbidities and previous non-spine surgery were significant risk factors for VO due to MRSA as compared to MSSA. The recurrence rate within 6 months tended to be higher for MRSA VO. Patients with MRSA VO should be monitored carefully for recurrence by sequential clinical, radiographic, and laboratory examinations during the treatment course.

Mapping the genetic diversity within major clonal complexes of meticillin-resistant Staphylococcus aureus utilizing genome-wide fluorescent amplified fragment length polymorphism markers

The genetic diversity between major meticillin-resistant Staphylococcus aureus (MRSA) lineages was probed using fluorescent amplified fragment length polymorphism (FAFLP) as a random genome sampling tool. Genomic DNA was digested with endonucleases BglII and Csp6I and a subset of the restricted fragments were amplified using the primer pair BglII+A and Csp6I+0. Sixty-seven FAFLP profiles consisting of 46-68 amplified fragments ranging in size from 50 to 600 bp were exhibited amongst the 71 isolates analysed. Cluster analysis of FAFLP data revealed concordance with spa typing and MLST clonal complexes (CC), with isolates of each CC grouping in the same FAFLP cluster. Furthermore, FAFLP could differentiate subtypes within the homogeneous CC22 isolates and also between MLST sequence types 8 and 239. The discriminatory power of FAFLP was 0.998 compared to values of 0.975 and 0.909 for spa typing and MLST, respectively. Thus, FAFLP analysis proved to be a rapid, reproducible and high-resolution tool that displayed the microheterogeneity within MRSA lineages. Using FAFLP data, lineage-specific fragments were identified and sequenced; these encoded toxins, antibiotic resistance determinants and bacteriophage resistance factors. Lineage-specific sequence variations were observed, which may provide insights into the evolution and fitness of successful lineages. This will also aid in the development of rapid and high-throughput diagnostic PCR-based assays for the identification of MRSA lineages in resource-poor settings.

Changing Italian nosocomial-community trends and heteroresistance in Staphylococcus aureus from bacteremia and endocarditis

Bloodstream infections due to Staphylococcus aureus (BSI) are serious infections both in hospitals and in the community, possibly leading to infective endocarditis (IE). The use of glycopeptides has been recently challenged by various forms of low-level resistance. This study evaluated the distribution of MSSA and MRSA isolates from BSI and IE in 4 Italian hospitals, their antibiotic susceptibility—focusing on the emergence of hVISA—and genotypic relationships. Our results demonstrate that the epidemiology of MRSA is changing versus different STs possessing features between community-acquired (CA)- and hospital-acquired (HA)-MRSA groups; furthermore, different MSSA isolated from BSI and IE were found, with the same backgrounds of the Italian CA-MRSA. The hVISA phenotype was very frequent (19.5%) and occurred more frequently in isolates from IE and in both the MSSA and MRSA strains. As expected, hVISA were detected in MRSA with vancomycin minimum inhibitory concentrations (MICs) of 1–2 mg/l, frequently associated with the major SCCmec I and II nosocomial clones; this phenotype was also detected in some MSSA strains. The few cases of MR-hVISA infections evaluated in our study demonstrated that 5 out of 9 patients (55%) receiving a glycopeptide, died. Future studies are required to validate these findings in terms of clinical impact.

Screening cardiac surgery patients for MRSA: an economic computer model

OBJECTIVE

To estimate the economic value of preoperative methicillin-resistant Staphylococcus aureus (MRSA) screening and decolonization for cardiac surgery patients.

STUDY DESIGN

Monte Carlo decision-analytic computer simulation model.

METHODS

We developed a computer simulation model representing the decision of whether to perform preoperative MRSA screening and decolonizing those patients with a positive MRSA culture. Sensitivity analyses varied key input parameters including MRSA colonization prevalence, decolonization success rates, the number of surveillance sites, and screening/decolonization costs. Separate analyses estimated the incremental cost-effectiveness ratio (ICER) of the screening and decolonization strategy from the third-party payer and hospital perspectives.

RESULTS

Even when MRSA colonization prevalence and decolonization success rate were as low as 1% and 25%, respectively, the ICER of implementing routine surveillance was well under $15,000 per quality-adjusted life-year from both the third-party payer and hospital perspectives. The surveillance strategy was economically dominant (less costly and more effective than no testing) for most scenarios explored.

CONCLUSIONS

Our results suggest that routine preoperative MRSA screening of cardiac surgery patients could provide substantial economic value to third-party payers and hospitals over a wide range of MRSA colonization prevalence levels, decolonization success rates, and surveillance costs. Healthcare administrators, infection control specialists, and surgeons can compare their local conditions with our study's benchmarks to make decisions about whether to implement preoperative MRSA testing. Third-party payers may want to consider covering such a strategy.

Incidence of bloodstream infection among patients on hemodialysis by central venous catheter

This study evaluated the incidence and risk factors of bloodstream infection (BSI) among patients with a double-lumen central venous catheter (CVC) for hemodialysis (HD) and identified the microorganisms isolated from the bloodstream. A follow-up included all patients (n=156) who underwent hemodialysis by double-lumen CVC at the Federal University of São Paulo-UNIFESP, Brazil, over a one-year period. From the group of patients, 94 presented BSI, of whom 39 had positive cultures at the central venous catheter insertion location. Of the 128 microorganisms isolated from the bloodstream, 53 were S. aureus, 30 were methicillin-sensitive and 23 were methicillin-resistant. Complications related to BSI included 35 cases of septicemia and 27 cases of endocarditis, of which 15 cases progressed to death. The incidence of BSI among these patients was shown to be very high, and this BSI progressed rapidly to the condition of severe infection with a high mortality rate.

Budget impact analysis of rapid screening for Staphylococcus aureus colonization among patients undergoing elective surgery in US hospitals

OBJECTIVE

To evaluate the economic impact of performing rapid testing for Staphylococcus aureus colonization before admission for all inpatients who are scheduled to undergo elective surgery and providing subsequent decolonization therapy for those patients found to be colonized with S. aureus.

METHODS

A budget impact model that used probabilistic sensitivity analysis to account for the uncertainties in the input variables was developed. Primary input variables included the marginal effect of S. aureus infection on patient outcomes among patients who underwent elective surgery, patient demographic characteristics, the prevalence of nasal carriage of S. aureus, the sensitivity and specificity of the rapid diagnostic test for S. aureus colonization, the efficacy of decolonization therapy for nasal carriage of S. aureus, and cost data. Data sources for the input variables included the 2003 Nationwide Inpatient Sample data and the published literature.

RESULTS

In 2003, there were an estimated 7,181,484 patients admitted to US hospitals for elective surgery. Our analysis indicated preadmission testing and subsequent decolonization therapy for patients colonized with S. aureus would have produced a mean annual cost savings to US hospitals of $231,538,400 (95% confidence interval [CI], -$300 million to $1.3 billion). The mean annual number of hospital-days that could have been eliminated was estimated at 364,919 days (95% CI, 67,893-926,983 days), and a mean of 935 in-hospital deaths (95% CI, 88-3,691) could have been avoided per year. Sensitivity analysis indicated a 64.5% probability that there would be cost savings to US hospitals as a result of preadmission testing and subsequent decolonization therapy.

CONCLUSION

The addition of preadmission testing and decolonization therapy to standard care would result in significant cost savings, even after accounting for variations in the model input values.

National trends in Staphylococcus aureus infection rates: impact on economic burden and mortality over a 6-year period (1998-2003)

BACKGROUND

We evaluated historical trends in the Staphylococcus aureus infection rate, economic burden, and mortality in US hospitals from 1998 through 2003.

METHODS

The Nationwide Inpatient Sample was used to assess trends over time of S. aureus infection during 1998-2003. Historical trends were determined for 5 strata of hospital stays, including all inpatient stays, surgical procedure stays, invasive cardiovascular surgical stays, invasive orthopedic surgical stays, and invasive neurosurgical stays.

RESULTS

During the 6-year study period from 1998 through 2003, the rate of S. aureus infection increased significantly for all inpatient stays (from 0.74% to 1.0%; annual percentage change (APC), 7.1%; P=.004), surgical stays (from 0.90% to 1.3%; APC, 7.9%; P=.001), and invasive orthopedic surgical stays (from 1.2% to 1.8%; APC, 9.3%; P<.001). For invasive neurosurgical stays, the rate of S. aureus infection did not change from 1998 to 2000 but increased at an annual rate of 11.0% from 2000 to 2003 (from 1.4% to 1.8%; P=.034). The total economic burden of S. aureus infection for hospitals also increased significantly for all stay types, with the annual percentage increase ranging from 9.2% to 17.9% (P<.05 for all). In 2003, the total economic burden of S. aureus infection was estimated to be $14.5 billion for all inpatient stays and $12.3 billion for surgical patient stays. However, there were significant decreases in the risk of S. aureus-related in-hospital mortality from 1998 to 2003 for all inpatient stays (from 7.1% to 5.6%; APC, -4.6%; P=.001) and for surgical stays (from 7.1% to 5.5%; APC, -4.6%; P=.002).

CONCLUSIONS

The inpatient S. aureus infection rate and economic burden of S. aureus infections for US hospitals increased substantially from 1998 to 2003, whereas the in-hospital mortality rate decreased.

Three Fatal Cases of Rapidly Progressive Infective Endocarditis Caused by Staphylococcus Aureus One Case With Huge Vegetation

Staphylococcus aureus (S. aureus) infective endocarditis (IE) is a severe disease with a high mortality despite intensive therapy. Three cases of S. aureus IE had a rapidly progressive fatal clinical course despite intensive antimicrobial therapy. One case was methicillin-sensitive S. aureus IE, which formed rapidly growing a huge vegetation on a prosthetic mitral valve, complicated with multiple systemic emboli. The other 2 cases were methicillin-resistant S. aureus IE without any predisposing heart disease.

[Staphylococcus aureus infections: new challenges from an old pathogen]

Staphylococcus aureus is a versatile organism with several virulent characteristics and resistance mechanisms at its disposal. It is also a significant cause of a wide range of infectious diseases in humans. S. aureus often causes life-threatening deep seated infections like bacteremia, endocarditis and pneumonia. While traditionally confined mostly to the hospital setting, methicillin-resistant S. aureus (MRSA) is now rapidly becoming rampant in the community. Community-acquired MRSA is particularly significant because of its potential for unchecked spread within households and its propensity for causing serious skin and pulmonary infections. Because of the unfavorable outcome of many MRSA infections with the standard glycopeptide therapy, new antimicrobial agents belonging to various classes have been introduced and have been evaluated in clinical trials for their efficacy in treating resistant staphylococcal infections. A number of preventive strategies have also been suggested to contain the spread of such infections. In this review, we address the recent changes in the epidemiology of S. aureus and their impact on the clinical manifestations and management of serious infections. We also discuss new treatment modalities for MRSA infections and emphasize the importance of preventive approaches.