Comparison of Outcomes among Adult Patients with Nosocomial Bacteremia Caused by Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus: A Retrospective Cohort Study

PBP4 is required for serum-induced cell wall thickening and antibiotic tolerance in Staphylococcus aureus

The bacterial pathogen Staphylococcus aureus responds to the host environment by synthesizing a thick peptidoglycan cell wall, which protects the bacterium from membrane-targeting antimicrobials and the immune response. However, the proteins required for this response were previously unknown. Here, we demonstrate by three independent approaches that the penicillin-binding protein PBP4 is crucial for serum-induced cell wall thickening. First, mutants lacking various non-essential cell wall synthesis enzymes were tested, revealing that a mutant lacking pbp4 was unable to generate a thick cell wall in serum. This resulted in reduced serum-induced tolerance of the pbp4 mutant toward the last resort antibiotic daptomycin relative to wild-type cells. Second, we found that serum-induced cell wall thickening occurred in each of a panel of 134 clinical bacteremia isolates, except for one strain with a naturally occurring mutation that results in an S140R substitution in the active site of PBP4. Finally, inhibition of PBP4 with cefoxitin prevented serum-induced cell wall thickening and the resulting antibiotic tolerance in the USA300 strain and clinical MRSA isolates. Together, this provides a rationale for combining daptomycin with cefoxitin, a PBP4 inhibitor, to potentially improve treatment outcomes for patients with invasive MRSA infections.

Female Sex and Mortality in Patients with Staphylococcus aureus Bacteremia: A Systematic Review and Meta-analysis

Importance

Staphylococcus aureus is the leading cause of death due to bacterial bloodstream infection. Female sex has been identified as a risk factor for mortality in S aureus bacteremia (SAB) in some studies, but not in others.

Objective

To determine whether female sex is associated with increased mortality risk in SAB.

Data Sources

MEDLINE, Embase, and Web of Science were searched from inception to April 26, 2023.

Study Selection

Included studies met the following criteria: (1) randomized or observational studies evaluating adults with SAB, (2) included 200 or more patients, (3) reported mortality at or before 90 days following SAB, and (4) reported mortality stratified by sex. Studies on specific subpopulations (eg, dialysis, intensive care units, cancer patients) and studies that included patients with bacteremia by various microorganisms that did not report SAB-specific data were excluded.

Data Extraction and Synthesis

Data extraction and quality assessment were performed by 1 reviewer and verified by a second reviewer. Risk of bias and quality were assessed with the Newcastle-Ottawa Quality Assessment Scale. Mortality data were combined as odds ratios (ORs).

Main Outcome and Measures

Mortality at or before 90-day following SAB, stratified by sex.

Results

From 5339 studies retrieved, 89 were included (132 582 patients; 50 258 female [37.9%], 82 324 male [62.1%]). Unadjusted mortality data were available from 81 studies (109 828 patients) and showed increased mortality in female patients compared with male patients (pooled OR, 1.12; 95% CI, 1.06-1.18). Adjusted mortality data accounting for additional patient characteristics and treatment variables were available from 32 studies (95 469 patients) and revealed a similarly increased mortality risk in female relative to male patients (pooled adjusted OR, 1.18; 95% CI, 1.11-1.27). No evidence of publication bias was encountered.

Conclusions and Relevance

In this systematic review and meta-analysis, female patients with SAB had higher mortality risk than males in both unadjusted and adjusted analyses. Further research is needed to study the potential underlying mechanisms.

Discovery of Bactericidal Proteins from Staphylococcus Phage Stab21 Using a High-Throughput Screening Method

In the escalating battle against antimicrobial resistance, there is an urgent need to discover and investigate new antibiotic strategies. Bacteriophages are untapped reservoirs of such potential antimicrobials. This study focused on Hypothetical Proteins of Unknown Function (HPUFs) from a Staphylococcus phage Stab21. We examined its HPUFs for bactericidal activity against E. coli using a Next Generation Sequencing (NGS)-based approach. Among the 96 HPUFs examined, 5 demonstrated cross-species toxicity towards E. coli, suggesting the presence of shared molecular targets between E. coli and S. aureus. One toxic antibacterial HPUF (toxHPUF) was found to share homology with a homing endonuclease. The implications of these findings are profound, particularly given the potential broad applicability of these bactericidal agents. This study confirms the efficacy of NGS in streamlining the screening process of toxHPUFs, contributes significantly to the ongoing exploration of phage biology, and offers promises in the search for potent antimicrobial agents.

Does local vancomycin powder impregnated with autogenous bone graft and bone substitute decrease the risk of deep surgical site infection in degenerative lumbar spine fusion surgery?—An ambispective study

Background

Deep surgical site infection (DSSI) is one of the most challenging complications in lumbar fusion surgery. Few investigations examined the effect of vancomycin powder mixed with autogenic bone graft (ABG) and bone substitutes on preventing DSSI in degenerative lumbar fusion surgeries as well as any interference with bony fusion. The aim of the study was to investigate the effects of ABG along with bone substitutes as a local vancomycin delivery system on preventing DSSI in lumbar instrumented fusion and compared with those who did not use vancomycin powder.

Methods

From January, 2015 through December, 2015, a one-year prospective study using vancomycin powder mixed with ABG and bone substitute for degenerative lumbar fusion surgeries as vancomycin (V) group, 1 gm vancomycin for 2 and 3-level, and 2 gm for more than 3-level instrumentation. From December, 2013 through December 2014, patients received degenerative lumbar fusion surgeries without using vancomycin before the vancomycin protocol were retrospectively enrolled as non-vancomycin (NV) group. Vancomycin concentration was checked at post-operative days 1 and 3 for both the serum and drainage. Patients’ demographic data, microbiology reports, fusion status and functional outcomes were evaluated.

Results

One hundred and ten patients were enrolled prospectively in the V group, and 86 for the NV group. After an average 41 months follow-up (range, 36–54), 3 patients (3.48%) developed postoperative DSSIs in the NV group, thereby requiring revision surgeries and parenteral antibiotics treatment versus no DSSIs (0%, 0/100) in the V group. (p = 0.048). The postoperative serum vancomycin levels were undetectable and no vancomycin related side effects was encountered. The mean vancomycin concentration of drainage at postoperative days 1 and 3 were 517.96 ± 174.4 and 220.14 ± 102.3 μg/mL, respectively. At final follow-up, there was no statistical difference observed in terms of clinical and radiologic outcomes.

Conclusions

Our vancomycin protocol may reduce the incidence of DSSI in degenerative lumbar fusion surgery without affecting bony fusion.

Level of Evidence

Level III ambispective comparative study.

Sequence type 8 as an emerging clone of methicillin-resistant Staphylococcus aureus causing bloodstream infections in Taiwan

Sequence type (ST) 8 has not been a common methicillin-resistant Staphylococcus aureus (MRSA) clone in Asia until recently. We aimed to determine the clinical significance and microbiological characteristics of MRSA bacteraemia (MRSAB) caused by ST8 and other endemic clones. A total of 281 non-duplicated MRSAB were identified in a medical centre between 2016 and 2018. Sequencing of target genes was performed to determine ST and to confirm ST8 belonging to USA300. Antimicrobial susceptibility testing was performing by using Sensititre standard panel. In total, ST8 accounted for 18.5% of MRSAB ranking after ST239 (31.0%) and ST59 (23.5%). However, it increased to become the most prevalent clone finally. All ST8 isolates belonged to spa clonal complex008, and carried SCCmec IV/IVa, PVL and ACME genes, indicating USA300. ST8/USA300 isolates were highly susceptible to non-β-lactams antibiotics, except fluoroquinolone and erythromycin. ST8/USA300 MRSAB is commonly developed in community settings with either healthcare risks or not (71.2%). Compared to other STs MRSAB, ST8/USA300 MRSAB patients had more diabetes mellitus (50.0%), more admitted from long-term care facility residents (25.0%), had more skin ad soft tissue infection as primary focus (25.0%), and had fewer vascular devices (26.9%) at MRSAB onset. On multivariable analysis, isolates with vancomycin MIC were significantly associated with mortality in the dose-response relationship, rather than STs. This report depicts the clinical features of ST8/USA300 MRSAB and clonal shift from prior endemic clones to ST8/USA300. Our data strongly support long-term surveillance to ascertain whether ST8/USA300 will successfully disseminate and demonstrate its pathogenicity on clinical outcomes.

Staphylococcus aureus Bacteremia in Patients Infected With COVID-19: A Case Series

Background

Previous viral pandemics have shown that secondary bacterial infections result in higher morbidity and mortality, with Staphylococcus aureus being the primary causative pathogen. The impact of secondary S. aureus bacteremia on mortality in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains unknown.

Methods

This was a retrospective observational case series of patients with coronavirus disease 2019 (COVID-19) who developed secondary S. aureus bacteremia across 2 New York City hospitals. The primary end point was to describe 14-day and 30-day hospital mortality rates of patients with COVID-19 and S. aureus bacteremia. Secondary end points included predictors of 14-day and 30-day hospital mortality in patients with COVID-19 and S. aureus bacteremia.

Results

A total of 42 patients hospitalized for COVID-19 with secondary S. aureus bacteremia were identified. Of these patients, 23 (54.8%) and 28 (66.7%) died at 14 days and 30 days, respectively, from their first positive blood culture. Multivariate analysis identified hospital-onset bacteremia (≥4 days from date of admission) and age as significant predictors of 14-day hospital mortality and Pitt bacteremia score as a significant predictor of 30-day hospital mortality (odds ratio [OR], 11.9; 95% CI, 2.03-114.7; P = .01; OR, 1.10; 95% CI, 1.03-1.20; P = .02; and OR, 1.56; 95% CI, 1.19-2.18; P = .003, respectively).

Conclusions

Bacteremia with S. aureus is associated with high mortality rates in patients hospitalized with COVID-19. Further investigation is warranted to understand the impact of COVID-19 and secondary S. aureus bacteremia.

Characterisation of antibiotic resistance, virulence, clonality and mortality in MRSA and MSSA bloodstream infections at a tertiary-level hospital in Hungary: a 6-year retrospective study

BACKGROUND

Staphylococcus aureus bloodstream infections (BSI) cause significant morbidity and mortality due to the frequent antibiotic resistance, toxin and adhesin production of the bacterium. These characteristics differ significantly in methicillin resistant (MRSA) and methicillin sensitive S. aureus (MSSA) and also among isolates of different MRSA clones, contributing to the outcome of S. aureus bacteraemia.

METHODS

In this study, all MRSA BSI isolates from Semmelweis University, Budapest, Hungary, isolated between 2011-2016 and the same number of matched MSSA (overall 306 isolates) were characterised in terms of antibiotic susceptibility, virulence genes, clonality and their association with all-cause 30-day mortality. Effect of patient related variables, such as age, gender and comorbidities were also investigated.

RESULTS

ST22-MRSA-IV and ST5-MRSA-II were the most prevalent clones in our study. SCCmec I isolates showed the highest resistance rates and SCCmec II carried most virulence genes. Infections caused by SCCmec IV isolates were associated with the highest mortality rate (42.2%), despite the similar comorbidity rates of the different patient groups. All-cause 30-day mortality was 39.9% in the MRSA and 30.7% in the MSSA group. Increased teicoplanin MIC was associated with high mortality rate. Resistance to ciprofloxacin, erythromycin and clindamycin was common in MRSA, whereas MSSA isolates were more sensitive to all antibiotics with the exception of doxycycline. All MRSA isolates were sensitive to glycopeptides and linezolid; resistance to rifampicin and sulfamethoxazole-trimethoprim was low. MRSA isolates carried more adhesion genes, superantigens were more frequent in MSSA. Panton-Valentine leukocidin was found in 2.3% of the isolates.

CONCLUSION

This study provides insight into the clonal composition and associated mortality of BSI S. aureus isolates in Hungary. The results suggest that the outcome of the infection is determined by the antibiotic resistance, genotype of the bacterium, and patient-related factors; rather than the virulence factors carried by the bacteria.

Comparison of quick SOFA and SIRS scales at the bedside of patients with Staphylococcus aureus bacteremia

Introducción:

Staphylococcus aureus es una de las principales causas de bacteriemia, adquirida en la comunidad o asociada con la atención en salud, la cual presenta un gran porcentaje de complicaciones y elevadas tasas de morbilidad y mortalidad. Los criterios SRIS (Systemic Inflammatory Response Syndrome) se han usado tradicionalmente con el fin de establecer la presencia de sepsis; sin embargo, recientemente se ha cuestionado su valor predictivo dada su baja sensibilidad y especificidad. En el 2016, apareció la escala qSOFA (quick Sequential Organ Failure Assessment), como una nueva herramienta para la evaluación rápida de las infecciones en los servicios de urgencias.

Objetivo.

Comparar las herramientas qSOFA y SRIS para la predicción de la bacteriemia por S. aureus.

Materiales y métodos.

Se hizo un estudio observacional sobre el comportamiento clínico de pacientes con bacteriemia por S. aureus para evaluar el perfil de resistencia fenotípica, algunas características sociodemográficas, clínicas y de laboratorio, las complicaciones y la mortalidad, así como los resultados de las evaluaciones con la escala qSOFA y los criterios SRIS, para establecer cuál podría predecir mejor la presencia de bacteriemia por S. aureus.

Resultados.

Se seleccionaron 26 pacientes con bacteriemia, en cuyas muestras S. aureus había sido el segundo germen más frecuentemente aislado. Se encontró una mortalidad del 50 % (13 casos) y una prevalencia del 30 % de S. aureus resistente a meticilina (SARM). Según los puntajes clínicos obtenidos, la escala qSOFA fue positiva en 30,8 % de los pacientes y los criterios SRIS lo fueron en el 92,3 %.

Discusión.

Se encontró una elevada mortalidad en la población analizada. La escala qSOFA fue menos efectiva para el diagnóstico que los criterios clásicos de reacción inflamatoria sistémica.

Part II: Minimum Quality Threshold in Preclinical Sepsis Studies (MQTiPSS) for Types of Infections and Organ Dysfunction Endpoints

Although the clinical definitions of sepsis and recommended treatments are regularly updated, a systematic review has not been done for preclinical models. To address this deficit, a Wiggers-Bernard Conference on preclinical sepsis modeling reviewed the 260 most highly cited papers between 2003 and 2012 using sepsis models to create a series of recommendations. This Part II report provides recommendations for the types of infections and documentation of organ injury in preclinical sepsis models. Concerning the types of infections, the review showed that the cecal ligation and puncture model was used for 44% of the studies while 40% injected endotoxin. Recommendation #8 (numbered sequentially from Part I): endotoxin injection should not be considered as a model of sepsis; live bacteria or fungal strains derived from clinical isolates are more appropriate. Recommendation #9: microorganisms should replicate those typically found in human sepsis. Sepsis-3 states that sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, but the review of the papers showed limited attempts to document organ dysfunction. Recommendation #10: organ dysfunction definitions should be used in preclinical models. Recommendation #11: not all activities in an organ/system need to be abnormal to verify organ dysfunction. Recommendation #12: organ dysfunction should be measured in an objective manner using reproducible scoring systems. Recommendation #13: not all experiments must measure all parameters of organ dysfunction, but investigators should attempt to fully capture as much information as possible. These recommendations are proposed as "best practices" for animal models of sepsis.

SCCmec typing of PVL-positive community-acquired Staphylococcus aureus (CA-MRSA) at a Japanese hospital

The epidemiology of Panton-Valentine leukocidin (PVL)-positive MRSA in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was examined. Three hundred and forty-two CA-MRSA strains that were susceptible to imipenem and cefazolin were isolated from 1107 samples (intravenous catheter, blood, sputum, urine, skin, wound, and pharynx) from outpatients at Showa University Hospital in Japan between September 2009 and March 2017. The PVL gene was detected in 46 of 342 CA-MRSA strains, accounting for 13.5%. The type of SCCmec was determined by detection of each SCCmec-specific region, class complex, and ccr. SCCmec type IV comprised 33 strains, type V comprised 5 strains, type VII comprised 4 strains, and the unclassified type comprised 4 strains. Among the type IV strains, subtype IVa was dominant, comprising 23 of 33 strains, and the remaining 10 strains were of varying subtypes. The SCCmec type III-specific region, CZ049, was amplified in 2 type V strains, 4 type VII strains, and 4 unclassified strains. In 4 unclassified strains, CZ049 and ccr5 were detected, but neither the SCCmec-specific region nor class complex was detected. The PVL-positive rate was lower than that in Western countries. The SCCmec types of PVL-positive CA-MRSA strains were found to vary, indicating a diverse spreading route.

Concurrent Atlantoaxial Septic Arthritis and Septic Thrombosis of the Ophthalmic Vein due to Staphylococcus aureus: A Case Report and Review of the Literature

Atlantoaxial joint septic arthritis and superior ophthalmic vein thrombosis are uncommon manifestations of Staphylococcus aureus infection. A 68-year-old man presented with acute-onset neck pain and diplopia. Imaging studies revealed atlantoaxial septic arthritis and right superior ophthalmic vein thrombosis. Blood cultures grew methicillin-susceptible S. aureus. We review the literature describing these 2 uncommon manifestations of a common pathogen.

Burdens of Invasive Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus Disease, Minnesota, USA

During August 1, 2014-July 31, 2015, in 2 counties in Minnesota, USA, incidence of invasive methicillin-susceptible Staphylococcus aureus (MSSA) (27.1 cases/100,000 persons) was twice that of invasive methicillin-resistant S. aureus (13.1 cases/100,000 persons). MSSA isolates were more genetically diverse and susceptible to more antimicrobial drugs than methicillin-resistant S. aureus isolates.

Staphylococcus aureus bloodstream infections in Latin America: results of a multinational prospective cohort study

Background

Substantial heterogeneity in the epidemiology and management of Staphylococcus aureus bacteraemia (SAB) occurs in Latin America. We conducted a prospective cohort study in 24 hospitals from nine Latin American countries.

Objectives

To assess the clinical impact of SAB in Latin America.

Patients and methods

We evaluated differences in the 30 day attributable mortality among patients with SAB due to MRSA compared with MSSA involving 84 days of follow-up. Adjusted relative risks were calculated using a generalized linear model.

Results

A total of 1030 patients were included. MRSA accounted for 44.7% of cases with a heterogeneous geographical distribution. MRSA infection was associated with higher 30 day attributable mortality [25% (78 of 312) versus 13.2% (48 of 363), adjusted RR: 1.94, 95% CI: 1.38-2.73, P < 0.001] compared with MSSA in the multivariable analysis based on investigators' assessment, but not in a per-protocol analysis [13% (35 of 270) versus 8.1% (28 of 347), adjusted RR: 1.10, 95% CI: 0.75-1.60, P = 0.616] or in a sensitivity analysis using 30 day all-cause mortality [36% (132 of 367) versus 27.8% (123 of 442), adjusted RR: 1.09, 95% CI: 0.96-1.23, P = 0.179]. MRSA infection was not associated with increased length of hospital stay. Only 49% of MSSA bloodstream infections (BSI) received treatment with β-lactams, but appropriate definitive treatment was not associated with lower mortality (adjusted RR: 0.93, 95% CI: 0.70-1.23, P = 0.602).

Conclusions

MRSA-BSIs in Latin America are not associated with higher 30 day mortality or longer length of stay compared with MSSA. Management of MSSA-BSIs was not optimal, but appropriate definitive therapy did not appear to influence mortality.

Exploring surface cleaning strategies in hospital to prevent contact transmission of methicillin-resistant Staphylococcus aureus

Background

Cleaning of environmental surfaces in hospitals is important for the control of methicillin-resistant Staphylococcus aureus (MRSA) and other hospital-acquired infections transmitted by the contact route. Guidance regarding the best approaches for cleaning, however, is limited.

Methods

In this study, a mathematical model based on ordinary differential equations was constructed to study MRSA concentration dynamics on high-touch and low-touch surfaces, and on the hands and noses of two patients (in two hospitals rooms) and a health care worker in a hypothetical hospital environment. Two cleaning interventions – whole room cleaning and wipe cleaning of touched surfaces – were considered. The performance of the cleaning interventions was indicated by a reduction in MRSA on the nose of a susceptible patient, relative to no intervention.

Results

Whole room cleaning just before first patient care activities of the day was more effective than whole room cleaning at other times, but even with 100% efficiency, whole room cleaning only reduced the number of MRSA transmitted to the susceptible patient by 54%. Frequent wipe cleaning of touched surfaces was shown to be more effective that whole room cleaning because surfaces are rapidly re-contaminated with MRSA after cleaning. Wipe cleaning high-touch surfaces was more effective than wipe cleaning low-touch surfaces for the same frequency of cleaning. For low wipe cleaning frequency (≤3 times per hour), high-touch surfaces should be targeted, but for high wipe cleaning frequency (>3 times per hour), cleaning should target high- and low-touch surfaces in proportion to the surface touch frequency. This study reproduces the observations from a field study of room cleaning, which provides support for the validity of our findings.

Conclusions

Daily whole room cleaning, even with 100% cleaning efficiency, provides limited reduction in the number of MRSA transmitted to susceptible patients via the contact route; and should be supplemented with frequent targeted cleaning of high-touch surfaces, such as by a wipe or cloth containing disinfectant.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2120-z) contains supplementary material, which is available to authorized users.

Thrombocytopaenia during methicillin-sensitive Staphylococcus aureus bacteraemia

The prognostic impact of thrombocytopaenia in Staphylococcus aureus bacteraemia (SAB) has previously been determined at bacteraemia onset only and relevant pre-bacteraemic thrombocytopaenia predisposing parameters have not been accounted for. We evaluated the prognostic impact of low thrombocyte count in SAB excluding pre-bacteraemic factors potentially causing thrombocytopaenia. This was a multicentre retrospective analysis of methicillin-sensitive SAB (MS-SAB) patients. Thrombocyte count was determined at blood culture collection and at days 3 and 7. Thrombocytopaenia was defined as a thrombocyte count less than 150 ×10⁹/L. Patients with chronic alcoholism, liver diseases and haematologic malignancies were excluded. Altogether, 495 patients were identified. Thrombocytopaenia at blood culture and at day 3 associated to endocarditis (p < 0.05 and p < 0.01) and defervescence (p < 0.001 and p < 0.01). Mortality at 90 days was higher for patients with thrombocytopaenia at blood culture collection (26 vs. 16%, p < 0.05), at day 3 (32 vs. 13%, p < 0.01) and at day 7 (50 vs. 14%, p < 0.001). In receiver operating characteristic analyses, thrombocytopaenia predicted a poor outcome at blood culture collection (p < 0.05), at day 3 (p < 0.001) and at day 7 (p < 0.001). When accounting for all prognostic parameters, thrombocytopaenia at day 3 [hazard ratio (HR), 1.83; p = 0.05] demonstrated a trend towards poor outcome, whereas thrombocytopaenia at day 7 (HR, 3.64; p < 0.001) associated to poor outcome. Thrombocytopaenia at blood culture collection was not a prognostic parameter when all prognostic factors were taken into account. However, thrombocytopaenia at day 3 indicated a poor outcome and thrombocytopaenia at day 7 was a significant independent negative prognostic marker that has not been previously reported in SAB.