Management of Staphylococcus aureus Bloodstream Infections

Long versus short course anti-MICROBIAL therapy of uncomplicated STAPHYLOCOCCUS aureus bacteraemia: a systematic review

BACKGROUND

Current guidelines recommend at least two weeks duration of antibiotic therapy (DOT) for patients with uncomplicated Staphylococcus aureus bacteraemia (SAB) but the evidence for this recommendation is unclear.

OBJECTIVES

To perform a systematic literature review assessing current evidence for recommended DOT for patients with SAB.

METHODS

Data sources: We searched MEDLINE, ISI Web of Science, the Cochrane Database and clinicaltrials.gov from inception to March 30, 2024. References of eligible studies were screened and experts in the field contacted for additional articles.

STUDY ELIGIBILITY CRITERIA

All clinical studies, regardless of design, publication status and language.

PARTICIPANTS

Adult patients with uncomplicated SAB.

INTERVENTIONS

Long (>14; >18; 11-16 days) vs. short (≤14; 10-18; 6-10 days, respectively) DOT with the DOT being defined as the first until the last day of antibiotic therapy.

ASSESSMENT OF RISK OF BIAS

Risk of bias was assessed using the ROBINS-I-tool.

METHODS OF DATA SYNTHESIS

The primary outcome was 90-day all-cause mortality. Only studies presenting results of adjusted analyses for mortality were included. Data synthesis could not be performed.

RESULTS

Eleven non-randomized studies were identified that fulfilled the predefined inclusion criteria, of which three studies reported adjusted effect ratios. Only these were included in the final analysis. We did not find any RCT. Two studies with 1,230 patients reported the primary endpoint 90-day all-cause mortality. Neither found a statistically significant superiority for longer (>14; 11-16 days) or shorter DOT (≤14; 6-10 days, respectively) for patients with uncomplicated SAB. Two studies investigated the secondary endpoint 30-day all-cause mortality (>18; 11-16 days vs. 10-18; 6-10 days, respectively) and did not find a statistically significant difference. All included studies had a moderate risk of bias.

CONCLUSIONS

Sound evidence that supports any duration of antibiotic treatment for patients with uncomplicated SAB is lacking.

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

Host response signature trends in persistent bacteraemia and metastatic infection due to Staphylococcus aureus and Gram-negative bacilli: a prospective multicentre observational study

BACKGROUND

A prompt diagnosis of bacteraemia and sepsis is essential. Markers to predict the risk of persistent bacteraemia and metastatic infection are lacking. SeptiCyte RAPID is a host response assay stratifying patients according to the risk of infectious vs sterile inflammation through a scoring system (SeptiScore). In this study we explore the association between SeptiScore and persistent bacteraemia as well as metastatic and persistent infection in the context of a proven bacteraemia episode.

METHODS

This is a prospective multicentre observational 14-month study on patients with proven bacteraemia caused by Staphylococcus aureus or Gram-negative bacilli. Samples for assessment by SeptiCyte were collected with paired blood cultures for 4 consecutive days after the index blood culture.

RESULTS

We included 86 patients in the study, 40 with S. aureus and 46 with Gram-negative bacilli bacteraemia. SeptiScores over the follow-up were higher in patients with Gram-negative compared to S. aureus bacteraemia (median 6.4, IQR 5.5-7.4 vs 5.6 IQR 5.1-6.2, p = 0.002). Higher SeptiScores were found to be associated with positive blood cultures at follow-up (AUC = 0.86, 95%CI 0.68-1.00) and with a diagnosis of metastatic infection at day 1 and 2 of follow-up (AUC = 0.79, 95%CI 0.57-1.00 and AUC = 0.82, 95%CI 0.63-1.00 respectively) in the context of Gram-negative bacteraemia while no association between SeptiScore and the outcomes of interest was observed in S. aureus bacteraemia. Mixed models confirmed the association of SeptiScore with positive blood cultures at follow-up (p = 0.04) and metastatic infection (p = 0.03) in the context of Gram-negative bacteraemia but not S. aureus bacteraemia after adjusting for confounders.

CONCLUSIONS

SeptiScores differ in the follow-up of S. aureus and Gram-negative bacteraemia. In the setting of Gram-negative bacteraemia SeptiScore demonstrated a good negative predictive value for the outcomes of interest and might help rule out the persistence of infection defined as metastatic spread, lack of source control or persistent bacteraemia.

Development of Oxadiazolone Activity-Based Probes Targeting FphE for Specific Detection of Staphylococcus aureus Infections

Staphylococcus aureus (S. aureus) is a major human pathogen that is responsible for a wide range of systemic infections. Since its propensity to form biofilms in vivo poses formidable challenges for both detection and treatment, tools that can be used to specifically image S. aureus biofilms are highly valuable for clinical management. Here, we describe the development of oxadiazolone-based activity-based probes to target the S. aureus-specific serine hydrolase FphE. Because this enzyme lacks homologues in other bacteria, it is an ideal target for selective imaging of S. aureus infections. Using X-ray crystallography, direct cell labeling, and mouse models of infection, we demonstrate that oxadiazolone-based probes enable specific labeling of S. aureus bacteria through the direct covalent modification of the FphE active site serine. These results demonstrate the utility of the oxadizolone electrophile for activity-based probes and validate FphE as a target for the development of imaging contrast agents for the rapid detection of S. aureus infections.

Persistence of Detectable Pathogens by Culture-Independent Systems (T2 Magnetic Resonance) in Patients With Bloodstream Infection: Prognostic Role and Possible Clinical Implications

BACKGROUND

Persistent Staphylococcus aureus bacteremia is associated with metastatic infection and adverse outcomes, whereas gram-negative bacteremia is normally transient and shorter course therapy is increasingly advocated for affected patients. Whether the prolonged detection of pathogen DNA in blood by culture-independent systems could have prognostic value and guide management decisions is unknown.

METHODS

We performed a multicenter, prospective, observational study on 102 patients with bloodstream infection (BSI) to compare time to bloodstream clearance according to T2 magnetic resonance and blood cultures over a 4-day follow-up. We also explored the association between duration of detectable pathogens according to T2 magnetic resonance (magnetic resonance-DNAemia [MR-DNAemia]) and clinical outcomes.

RESULTS

Time to bloodstream clearance according to T2 magnetic resonance was significantly longer than blood culture clearance (HR, .54; 95% CI, .39-.75) and did not differ according to the causative pathogen (P = .5). Each additional day of MR-DNAemia increased the odds of persistent infection (defined as metastatic infection or delayed source control) both in the overall population (OR, 1.98; 95% CI, 1.45-2.70) and in S. aureus (OR, 1.92; 95% CI, 1.12-3.29) and gram-negative bacteremia (OR, 2.21; 95% CI, 1.35-3.60). MR-DNAemia duration was also associated with no improvement in Sequential Organ Failure Assessment score at day 7 from infection onset (OR, 1.76; 95% CI, 1.21-2.56).

CONCLUSIONS

T2 magnetic resonance may help diagnose BSI in patients on antimicrobials with negative blood cultures as well as to identify patients with metastatic infection, source control failure, or adverse short-term outcome. Future studies may inform its usefulness within the setting of antimicrobial stewardship programs.

MEndoB, a chimeric lysin featuring a novel domain architecture and superior activity for the treatment of staphylococcal infections

Bacterial infections are a growing global healthcare concern, as an estimated annual 4.95 million deaths are associated with antimicrobial resistance (AMR). Methicillin-resistant Staphylococcus aureus is one of the deadliest pathogens and a high-priority pathogen according to the World Health Organization. Peptidoglycan hydrolases (PGHs) of phage origin have been postulated as a new class of antimicrobials for the treatment of bacterial infections, with a novel mechanism of action and no known resistances. The modular architecture of PGHs permits the creation of chimeric PGH libraries. In this study, the chimeric enzyme MEndoB was selected from a library of staphylococcal PGHs based on its rapid and sustained activity against staphylococci in human serum. The benefit of the presented screening approach was illustrated by the superiority of MEndoB in a head-to-head comparison with other PGHs intended for use against staphylococcal bacteremia. MEndoB displayed synergy with antibiotics and rapid killing in human whole blood with complete inhibition of re-growth over 24 h at low doses. Successful treatment of S. aureus-infected zebrafish larvae with MEndoB provided evidence for its in vivo effectiveness. This was further confirmed in a lethal systemic mouse infection model in which MEndoB significantly reduced S. aureus loads and tumor necrosis factor alpha levels in blood in a dose-dependent manner, which led to increased survival of the animals. Thus, the thorough lead candidate selection of MEndoB resulted in an outstanding second-generation PGH with in vitro, ex vivo, and in vivo results supporting further development.IMPORTANCEOne of the most pressing challenges of our era is the rising occurrence of bacteria that are resistant to antibiotics. Staphylococci are prominent pathogens in humans, which have developed multiple strategies to evade the effects of antibiotics. Infections caused by these bacteria have resulted in a high burden on the health care system and a significant loss of lives. In this study, we have successfully engineered lytic enzymes that exhibit an extraordinary ability to eradicate staphylococci. Our findings substantiate the importance of meticulous lead candidate selection to identify therapeutically promising peptidoglycan hydrolases with unprecedented activity. Hence, they offer a promising new avenue for treating staphylococcal infections.

Rapid detection of Staphylococcus aureus in blood culture samples using human IgG-based lateral flow assay

Staphylococcus aureus is one of the most common pathogens. The conventional workflow for identifying this organism is time-consuming and takes up to several days. Therefore, we developed a colloidal gold-based lateral flow immunoassay (LFIA) using human IgG as a conjugated antibody to detect S. aureus. One hundred and thirty-eight clinical isolates, including 79 S. aureus and 59 non-S. aureus were spiked in blood samples, and incubated at 37°C for 24 h. The bacterial antigens were simply extracted before being tested by the developed LFIA strips. The results were read by the naked eye within 15 min. Conventional PCR was used as a reference method. The sensitivity and specificity of the developed LFIA were 100% (95% CI: 94.2%-100.0% and 92.4%-100.0%, respectively) in spiked blood culture samples. The detection limits of the LFIA for the purified protein A and bacterial colonies were 10-3 µg/mL and 107 CFU/mL, respectively. The performance of the LFIA testing in 221 bacterial colony isolates and 118 positive blood culture bottles from three hospitals by their medical technologists showed 98.1% (95% CI: 94.1%-99.5%) and 89.7% (95% CI: 79.3%-95.4%) sensitivity, respectively. The LFIA is a quick, easy, and sensitive method for detecting S. aureus without expensive equipment. It might have the potential for early diagnosis of routine service in low-resource laboratories, leading to a rapid and effective treatment.IMPORTANCEIn this study, we modified our previously developed lateral flow immunoassay (LFIA) test for the detection of Staphylococcus aureus by using an in-house human IgG as a conjugated antibody instead of the specific commercial antibody. It gave comparable results to the former developed-LFIA test and helped cost reduction.

Development of Oxadiazolone Activity-Based Probes Targeting FphE for Specific Detection of S. aureus Infections

Staphylococcus aureus is a major human pathogen responsible for a wide range of systemic infections. Since its propensity to form biofilms in vivo poses formidable challenges for both detection and treatment, tools that can be used to specifically image S. aureus biofilms are highly valuable for clinical management. Here we describe the development of oxadiazolonebased activity-based probes to target the S. aureus-specific serine hydrolase FphE. Because this enzyme lacks homologs in other bacteria, it is an ideal target for selective imaging of S. aureus infections. Using X-ray crystallography, direct cell labeling and mouse models of infection we demonstrate that oxadiazolone-based probes enable specific labeling of S. aureus bacteria through the direct covalent modification of the FphE active site serine. These results demonstrate the utility of the oxadizolone electrophile for activity-based probes (ABPs) and validate FphE as a target for development of imaging contrast agents for the rapid detection of S. aureus infections.

Effect of Usnea longissima ethyl acetate extract on acute oxidative and inflammatory lung damage from Staphylococcus aureus infection in rats

The role of oxidants and proinflammatory cytokines in the pathogenesis of pneumonia caused by Staphylococcus aureus (S. aureus) has been demonstrated. The present study aims to investigate the protective effect of ethyl acetate extract (EtOAc) obtained from Usnea longissima (UL) against acute oxidative and inflammatory lung damage due to S. aureus infection in rats. Albino Wistar-type male rats were divided into three groups: Healthy (HG), S. aureus inoculated (SaG), and S. aureus inoculated + ULEtOAc administered (SUL). SaG (n = 6) and SUL (n = 6) group rats' left nostrils (excluding HG) were inoculated with 0.1 ml bacterial mixture. After 24 hours, ULEtOAc (50 mg/kg) was administered orally to the SUL group, and the same volume of normal saline was administered orally to the HG (n = 6) and SaG groups. This procedure was performed once a day for seven days. Levels of oxidant and antioxidant parameters such as malondialdehyde (MDA) and total glutathione (tGSH), as well as pro-inflammatory cytokine levels such as nuclear factor-kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin-one beta (IL-1β), were measured in removed lung tissues. Tissues were also examined histopathologically. Biochemical results showed that ULEtOAc significantly suppressed the increase of MDA, NF-κB, TNF-α, and IL-1β levels and the decrease of tGSH caused by S. aureus in lung tissue. S. aureus inoculation caused severe mononuclear cell infiltration in interstitial areas, severe lymphoid hyperplasia in bronchial-associated lymphoid tissue and severe alveolar edema, histopathologically. Treatment with ULEtOAc had an attenuating effect on these histopathological findings. Experimental results from this study suggest that ULEtOAc may be beneficial in treating S. aureus-induced oxidative and inflammatory lung damage.

The Controversial Effect of Antibiotics on Methicillin-Sensitive S. aureus: A Comparative In Vitro Study

Methicillin-sensitive Staphylococcus (S.) aureus (MSSA) bacteremia remains a global challenge, despite the availability of antibiotics. Primary treatments include β-lactam agents such as cefazolin and flucloxacillin. Ongoing discussions have focused on the potential synergistic effects of combining these agents with rifampicin or fosfomycin to combat infections associated with biofilm formation. Managing staphylococcal infections is challenging due to antibacterial resistance, biofilms, and S. aureus's ability to invade and replicate within host cells. Intracellular invasion shields the bacteria from antibacterial agents and the immune system, often leading to incomplete bacterial clearance and chronic infections. Additionally, S. aureus can assume a dormant phenotype, known as the small colony variant (SCV), further complicating eradication and promoting persistence. This study investigated the impact of antibiotic combinations on the persistence of S. aureus 6850 and its stable small colony variant (SCV strain JB1) focusing on intracellular survival and biofilm formation. The results from the wild-type strain 6850 demonstrate that β-lactams combined with RIF effectively eliminated biofilms and intracellular bacteria but tend to select for SCVs in planktonic culture and host cells. Higher antibiotic concentrations were associated with an increase in the zeta potential of S. aureus, suggesting reduced membrane permeability to antimicrobials. When using the stable SCV mutant strain JB1, antibiotic combinations with rifampicin successfully cleared planktonic bacteria and biofilms but failed to eradicate intracellular bacteria. Given these findings, it is reasonable to report that β-lactams combined with rifampicin represent the optimal treatment for MSSA bacteremia. However, caution is warranted when employing this treatment over an extended period, as it may elevate the risk of selecting for small colony variants (SCVs) and, consequently, promoting bacterial persistence.

Host gut-derived Bacillus probiotics supplementation improves growth performance, serum and liver immunity, gut health, and resistive capacity against Vibrio harveyi infection in hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus)

Several reports have revealed the vital role that probiotics play in fish growth and health. However, few works are available for host gut-derived probiotics on the growth, immunity, and gut microbiota of fish, especially in hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus) due to their isolation difficulty and functional verification. This study aimed at assessing 3 host gut-derived Bacillus species' effects on the growth, immune and antioxidant-biochemical responses, haematological parameters, intestinal morphology, immune-related gene expression, gut microbiota, and disease resistance against Vibrio harveyi in hybrid grouper. A total of 480 hybrid grouper (initial weight = 9.03 ± 0.02 g) were randomly allotted into 4 groups, namely, the group fed a basal diet without probiotic inclusion (control, B0), the group fed the basal diet with Bacillus velezensis GPSAK4 (BV), the group fed the basal diet with Bacillus subtilis GPSAK9 (BS), and the group fed the basal diet with Bacillus tequilensis GPSAK2 (BT) strains at 1.0 × 10⁹ CFU/g. After a 6-week feeding trial, the results revealed significant improvements (P < 0.05) in the growth performance, whole fish-body proximate composition, blood haematological parameters, serum, liver, and intestinal biochemical indexes, intestinal morphology, and protection against V. harveyi pathogen in the probiotic-treated groups compared with the untreated. Additionally, the expressions of intestinal tight junction genes (occludin and ZO1), pro- and anti-inflammatory genes, including IL1β, IL6, IL8, TNFα, MyD88, IL10, and TGFβ, were upregulated (P < 0.05) after Bacillus species administration. Host gut-derived Bacillus supplementation shaped the gut microbiota by significantly increasing (P < 0.05) the relative abundance of Proteobacteria, Bacteroidetes, Actinobacteria (except the BS group), Acidobacteria (except the BT group), Cyanobacteria (except the BV and BT groups), and Verrucomicrobia phyla, as well as known beneficial genera (Romboutsia, Turicibacter, Epulopiscium, Clostridium_sensu_stricto 1 and 13, Lactobacillus, and Bacillus), but significantly decreased (P < 0.05) the abundance of Firmicutes, Chloroflexi, and Fusobacteria phyla, and purported pathogenic genera (Staphylococcus and Photobacterium) compared with the control group. Collectively, the results suggest that B. velezensis GPSAK4, B. subtilis GPSAK9 (especially this strain), B. tequilensis GPSAK2 dietary supplementation at 1.0 × 10⁹ CFU/g has positive effects on the intestinal health of hybrid grouper via microbial composition modulation, thus enhancing the assimilation and absorption of nutrients to boost fish growth, immunity, and disease resistance.

Molecular characterization of enterotoxin genes in methicillin-resistant S. aureus isolated from food poisoning outbreaks in Egypt

BACKGROUND

Staphylococcus aureus (S. aureus), especially methicillin-resistant S. aureus (MRSA), is a known disease-causing bacteria with many associated health hazards. Staphylococcal food poisoning can result from staphylococcal enterotoxins (SEs).

METHODS

In this study, 50 S. aureus isolates were isolated from the gastrointestinal tract (GIT) clinical samples of patients with food poisoning in clinical laboratories at Mansoura University Hospital, Egypt. For determination their antibiogram, these isolates were tested for antimicrobial sensitivity against 12 antimicrobial agents using the agar disk diffusion test. After DNA extraction from the isolates, conventional polymerase chain reaction (PCR) was used to detect mecA and SEs genes.

RESULTS

As a result, all isolates were ampicillin and cefoxitin-resistant, while 86% (43 of 50) of the tested isolates exhibited multidrug resistance (MDR). In contrast, the highest sensitivity was confirmed against vancomycin, linezolid and quinolones, namely ciprofloxacin and norfloxacin. Although 100% of the isolates were mecA positive, staphylococcal enterotoxin genes set-A, set-B, set-C, set-G, set-M, and set-O genes were detected in 56%, 20%, 8%, 32%, 16%, and 24%, of the tested isolates, respectively. Finally, isolates encompassing SEs genes were used to validate a microarray chip, indicating its potential for a better methodological approach for detecting and identifying SEs in human samples.

CONCLUSION

The genotypic findings of this study may help explain the enterotoxigenic patterns in S. aureus among Egyptian patients with food poisoning.

Bacterial distribution and drug resistance in blood samples of children in Jiangxi Region, 2017-2021

Objective

This study aims to investigate the distribution and drug resistance of bacteria in clinical blood culture specimens from children in Jiangxi province in recent years and to provide a foundation for preventing and treating bloodstream infection diseases in children.

Methods

The study involved a statistical analysis of the isolation and drug resistance of bacterial strains obtained from blood culture specimens of children in Jiangxi province between 2017 and 2021. The analysis was performed using the WHONET 5.6 software.

Results

A total of 7,977 bacterial strains were isolated from the blood samples of children between 2017 and 2021. Of these, 2,334 strains (29.3%) were identified as Gram-negative bacteria, and 5,643 strains (70.7%) were identified as Gram-positive bacteria. The most commonly isolated pathogens were coagulase-negative Staphylococcus, Escherichia coli, and Staphylococcus aureus. Among the Gram-negative bacteria, Escherichia coli (840 strains, 36.0%), Klebsiella pneumoniae (385 strains), Salmonella (283 strains), Acinetobacter baumannii (137 strains), and Pseudomonas aeruginosa (109 strains) were the most prevalent. Among the Gram-positive bacteria, coagulase-negative Staphylococcus (3,424 strains, 60.7%), Staphylococcus aureus (679 strains), Streptococcus pneumoniae (432 strains), Enterococcus sp. (292 strains), and Streptococcus agalactiae (192 strains) were the most common. Resistance to third-generation cephalosporins (cefotaxime/ceftriaxone) was observed in 45.9% and 56.0% of Escherichia coli and Klebsiella pneumoniae strains, respectively, while resistance to carbapenems was observed in 4.6% and 20.3% of these strains, respectively. Resistance to third-generation cephalosporins (cefotaxime/ceftriaxone) was observed in 15.5% of Salmonella strains, while resistance to imipenem was absent. Carbapenem resistance was observed in 17.1% (20/117) and 13% (14/108) of Acinetobacter baumannii and Pseudomonas aeruginosa strains, respectively. Methicillin-resistant Staphylococcus aureus (MRSA) was detected in 32.7% of the strains, while methicillin-resistant coagulase-negative Staphylococcus was detected in 64.3% of the coagulase-negative Staphylococcus strains. No Staphylococcus bacteria resistant to vancomycin were detected. Four strains of vancomycin-resistant Enterococcus faecium were detected over the 5-year period, and one strain of linezolid-resistant Enterococcus faecalis was detected.

Conclusion

Gram-positive cocci were the most commonly isolated clinical pathogens in blood specimens from children in Jiangxi province. The composition of the pathogen species showed a slight change over the years. The detection ratios of pathogens varied with age group and season. Although the isolation rate of common carbapenem-resistant Enterobacter bacteria has decreased, it remains high. It is necessary to monitor the antimicrobial resistance of pathogens causing bloodstream infections in children more closely, and antimicrobial agents should be used with caution.

A Retrospective Study of Staphylococcus aureus Bacteremia in a Tertiary Hospital and Factors Associated with Mortality

Staphylococcus aureus bacteremia (SAB) is a severe infection frequently associated with significant morbidity and mortality. Recent studies have shown that SAB mortality has decreased during the last decades. However, about 25% of patients suffering from the disease will ultimately die. Hence, there is an urgent need for more timely and efficient treatment of patients with SAB. The aim of the present study was to retrospectively evaluate a cohort of SAB patients hospitalized in a tertiary hospital and to identify factors independently associated with mortality. All 256 SAB patients hospitalized from January 2005 to December 2021 in the University Hospital of Heraklion, Greece, were evaluated. Their median age was 72 years, while 101 (39.5%) were female. Most SAB patients were cared for in medical wards (80.5%). The infection was community-acquired in 49.5%. Among all strains 37.9% were methicillin-resistant S. aureus (MRSA), however, definite treatment with an antistaphylococcal penicillin was given only in 22% of patients. Only 14.4% of patients had a repeat blood culture after the initiation of antimicrobial treatment. Infective endocarditis was present in 8%. In-hospital mortality has reached 15.9%. Female gender, older age, higher McCabe score, previous antimicrobial use, presence of a central venous catheter, neutropenia, severe sepsis, septic shock, and MRSA SAB were positively associated with in-hospital mortality, while monomicrobial bacteremia was negatively associated. The multivariate logistic regression model identified only severe sepsis (p = 0.05, odds ratio = 12.294) and septic shock (p = 0.007, odds ratio 57.18) to be independently positively associated with in-hospital mortality. The evaluation revealed high rates of inappropriate empirical antimicrobial treatment and non-adherence to guidelines, as shown, by the lack of repeat blood cultures. These data underline the urgent need for interventions with antimicrobial stewardship, increased involvement of infectious diseases physicians, educational sessions, and creation and implementation of local guidelines for improvement of the necessary steps for timely and efficient SAB treatment. Optimization of diagnostic techniques is needed to overcome challenges such as heteroresistance that may affect treatment. Clinicians should be aware of the factors associated with mortality in patients with SAB to identify those who are at a higher risk and optimize medical management.

[Therapy-relevant antibiotic resistances in a One Health context]

One Health refers to a concept that links human, animal, and environmental health. In Germany, there is extensive data on antibiotic resistance (AMR) and multidrug-resistant (micro)organisms (MDRO) in human and veterinary medicine, as well as from studies in various environmental compartments (soil, water, wastewater). All these activities are conducted according to different specifications and standards, which makes it difficult to compare data. A focus on AMR and MDRO of human therapeutic importance is helpful to provide some guidance. Most data are available across sectors on methicillin-resistant Staphylococcus aureus (MRSA) and multiresistant Enterobacterales such as Escherichia coli and Klebsiella pneumoniae. Here, the trends of resistance are heterogeneous. Antibiotic use leads to MRE selection, which is well documented. Success in minimizing antibiotic use has also been demonstrated in recent years in several sectors and could be correlated with success in containing AMR and MDRO (e.g., decrease in MRSA in human medicine). Sector-specific measures to reduce the burden of MDRO and AMR are also necessary, as not all resistance problems are linked to other sectors. Carbapenem resistance is still rare, but most apparent in human pathogens. Colistin resistance occurs in different sectors but shows different mechanisms in each. Resistance to antibiotics of last resort such as linezolid is rare in Germany, but shows a specific One Health correlation. Efforts to harmonize methods, for example in the field of antimicrobial susceptibility testing and genome-based pathogen and AMR surveillance, are an important first step towards a better comparability of the different data collections.

May Sulfonamide Inhibitors of Carbonic Anhydrases from Mammaliicoccus sciuri Prevent Antimicrobial Resistance Due to Gene Transfer to Other Harmful Staphylococci?

Mammaliicoccus sciuri, previously known as Staphylococcus sciuri, is a Gram-positive bacterium involved in gene transfer phenomena that confer resistance to multiple antibiotics. These plasmid-encoded genes can be easily transferred to other pathogenic staphylococci. Because antibiotic resistance is rising, inhibiting M. sciuri proliferation may be a credible strategy for restricting antimicrobial resistance gene transfer to other pathogenic bacteria. Recently, it has been shown that blocking bacterial carbonic anhydrases (CAs, EC 4.2.1.1), metalloenzymes sustaining bacterial metabolic activities, can reduce pathogen survival and fitness. Here, the recombinant M. sciuri γ-CA (MscCAγ) has been cloned and purified, utilizing the DNA recombinant technology. Its kinetic properties for the CO₂ hydration reaction, as well as the sulfonamide inhibition profile, were investigated and compared with those reported earlier for MscCAβ (previously described as SauBCA) and the two off-target human CA isoforms (hCA I and hCA II). The recombinant MscCAγ showed significant hydratase activity. Moreover, the MscCAγ sulfonamide inhibitory profile was different from that of MscCAβ, implying that a varied amino acid set typifies the catalytic pocket of the two enzymes. These differences provide additional evidence for the possibility of developing novel CA class-specific inhibitors.

Development of a Multiplex Polymerase Chain Reaction-Based DNA Lateral Flow Assay as a Point-of-Care Diagnostic for Fast and Simultaneous Detection of MRSA and Vancomycin Resistance in Bacteremia

To reduce high mortality and morbidity rates, timely and proper treatment of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection is required. A multiplex polymerase reaction (mPCR)-based DNA lateral flow assay (MBDLFA) was developed as a point-of-care diagnostic for simultaneous identification of S. aureus, methicillin resistance, and vancomycin resistance directly from blood or blood cultures. A mPCR was developed to detect nuc, mecA, and vanA/B; its sensitivity, specificity, and limit of detection (LOD) were determined. The developed reaction was further modified for use in MBDLFA and its sensitivity for detection of target genes from artificially inoculated blood samples was checked. The optimized mPCR successfully detected nuc, mecA, and vanA/B from genomic DNA of bacterial colonies with LODs of 107, 107, and 105 CFU/mL, respectively. The reaction was sensitive and specific. The optimized mPCR was used in MBDLFA that detected nuc, mecA, and vanA/B with LODs of 107, 108, and 104 CFU/mL, respectively, directly from artificially inoculated blood. The developed MBDLFA can be used as a rapid, cheap point-of-care diagnostic for detecting S. aureus, MRSA, and vancomycin resistance directly from blood and blood cultures in ~2 h with the naked eye. This will reduce morbidity, mortality, and treatment cost in S. aureus bacteremia.

Rapid detection of Staphylococcus aureus using a novel multienzyme isothermal rapid amplification technique

Staphylococcus aureus is a common pathogen that causes various infections. Therefore, it is crucial to develop a fast and easy detection method for diagnosing and preventing S. aureus infections. In this study, MIRA assay was developed and validated (specificity; 100%) for the detection of S. aureus with nuc as the target gene. The reaction temperature and reaction time were then optimized, and the best reaction was at 40°C, 20 min. The assay could detect S. aureus in only 25 min. Additionally, the limit of detection of MIRA was 5 × 10² CFU/ml, 10-fold lower than that of the traditional PCR. Furthermore, this assay efficiently detected 219 S. aureus of 335 strains obtained from different bacterial samples (detection accuracy; 99.40%). In conclusion, this study provides a rapid and easy-to-operate method for the detection of S. aureus, and thus can be used for the timely diagnosis and prevention of S. aureus infection.

Pandemic clone USA300 in a Brazilian hospital: detection of an emergent lineage among methicillin-resistant Staphylococcus aureus isolates from bloodstream infections

Background

Staphylococcus aureus is one of the leading causes of bloodstream infections (BSI) worldwide. In Brazil, the hospital-acquired methicillin-resistant S. aureus USA100/SCCmecII lineage replaced the previously well-established clones. However, the emergence of community-associated (CA) MRSA lineages among hospitalized patients is an increasing issue.

Methods

Consecutive S. aureus isolates recovered from BSI episodes of patients admitted between January 2016 and December 2018 in a Brazilian teaching hospital were tested for antimicrobial resistance, their genotypic features were characterized, and the clinical characteristics of the patients were evaluated.

Results

A total of 123 S. aureus isolates were recovered from 113 patients. All isolates were susceptible to linezolid, teicoplanin and vancomycin and 13.8% were not susceptible to daptomycin. Vancomycin MIC50 and MIC90 of 2 mg/L were found for both MRSA and MSSA isolates. The MRSA isolation rate was 30.1% (37/123), and 51.4% of them carried the SCCmec type II, followed by SCCmecIV (40.5%). Among the 37 MRSA isolates, the main lineages found were USA100/SCCmecII/ST5 and ST105 (53.7%) and USA800/ST5/SCCmecIV (18.9%). Surprisingly, six (16%) CA-MRSA isolates, belonging to USA300/ST8/SCCmecIVa that carried PVL genes and the ACME cassette type I, were detected. These six patients with USA300 BSI had severe comorbidities, including cancer, and most had a Charlson score ≥ 5; furthermore, they were in wards attended by the same health professionals. MRSA isolates were associated with hospital acquired infections (p = 0.02) in more elderly patients (p = 0.03) and those diagnosed with hematologic cancer (p = 0.04). Among patients diagnosed with MRSA BSI, 19 (54.3%) died.

Conclusions

The pandemic MRSA USA300 was detected for the first time in the Brazilian teaching hospital under study, and its cross-transmission most probably occurred between patients with BSI. This lineage may already be circulating among other Brazilian hospitals, which highlights the importance of carrying out surveillance programs to fight multidrug resistant and hypervirulent isolates.

Cost and healthcare utilization of methicillin-resistant Staphylococcus aureus bacteremia estimated from linked antimicrobial resistance surveillance and hospital claims data in Japan

OBJECTIVE

To compare the incremental costs and healthcare utilization of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia with those of methicillin-susceptible S. aureus (MSSA) bacteremia.

DESIGN

Retrospective cohort study using data from April 2014 to March 2015.

SETTING

Antimicrobial resistance surveillance and hospital claims data from 16 Japanese hospitals.

PATIENTS

The study included 73 patients with S. aureus bacteremia: 23 with MRSA and 50 with MSSA.

METHODS

MRSA bacteremia was identified using blood cultures and drug-susceptibility tests. MRSA- and MSSA-related medical practices were evaluated. The costs were calculated and compared. All the medical costs were classified into empirical and definitive therapy periods and expressed in Japanese yen (JPY, 1 USD = 106 JPY). Additionally, costs at aggressive and passive bacterial test-performing facilities were compared.

RESULTS

No significant differences existed in MRSA-related resource use per patient episode between MRSA and MSSA bacteremia during empirical therapy. However, during definitive therapy, in MRSA bacteremia compared with MSSA bacteremia, this difference was higher. The average MRSA-related costs of empirical therapy for MRSA and MSSA were 13,380 and 9,140 JPY (126 and 86 USD) per patient, and for definitive therapy, they were 69,810 and 29,510 JPY (659 and 278 USD) per patient, respectively. No significant differences were noted. Conversely, the average examination costs during definitive therapy differed significantly: 9,740 vs 3,850 JPY (92 vs 36 USD), respectively (P = .0294). Furthermore, the incremental costs in aggressive facilities were lower for the definitive therapy period than those in passive facilities.

CONCLUSIONS

In the definitive therapy period, MRSA bacteremia had higher incremental costs and greater use of healthcare resources. In addition, the incremental costs in aggressive facilities were lower than those in passive facilities.

Engineered human antibodies for the opsonization and killing of Staphylococcus aureus

Staphylococcus aureus invariably acquires resistance mechanisms against new antibiotics. The persistent colonization with S. aureus is the key risk factor for invasive disease and a driver for the evolution of antibiotic resistant isolates. Anti-S. aureus antibodies that could promote decolonization, prevent infection, or treat disease would alleviate the selection for drug resistance. The successful development of such antibodies is complicated by Staphylococcal protein A (SpA) in the envelope of S. aureus. SpA captures immunoglobulins via their constant region, preventing antibodies from initiating anti-staphylococcal activities. Here, we demonstrate that therapeutic anti-S. aureus antibodies can be engineered to avoid sequestration by SpA. Such antibodies display extended half-lives and improve bacterial uptake and killing by immune cells.

Gram-positive organisms with their thick envelope cannot be lysed by complement alone. Nonetheless, antibody-binding on the surface can recruit complement and mark these invaders for uptake and killing by phagocytes, a process known as opsonophagocytosis. The crystallizable fragment of immunoglobulins (Fcγ) is key for complement recruitment. The cell surface of S. aureus is coated with Staphylococcal protein A (SpA). SpA captures the Fcγ domain of IgG and interferes with opsonization by anti-S. aureus antibodies. In principle, the Fcγ domain of therapeutic antibodies could be engineered to avoid the inhibitory activity of SpA. However, the SpA-binding site on Fcγ overlaps with that of the neonatal Fc receptor (FcRn), an interaction that is critical for prolonging the half-life of serum IgG. This evolutionary adaptation poses a challenge for the exploration of Fcγ mutants that can both weaken SpA–IgG interactions and retain stability. Here, we use both wild-type and transgenic human FcRn mice to identify antibodies with enhanced half-life and increased opsonophagocytic killing in models of S. aureus infection and demonstrate that antibody-based immunotherapy can be improved by modifying Fcγ. Our experiments also show that by competing for FcRn-binding, staphylococci effectively reduce the half-life of antibodies during infection. These observations may have profound impact in treating cancer, autoimmune, and asthma patients colonized or infected with S. aureus and undergoing monoclonal antibody treatment.

Beta hemolysin gene of Staphylococcus phage 3AJ_2017 genome is a suitable molecular marker for identification and characterization of pathogenic Staphylococcus aureus

BACKGROUND

Staphylococcus aureus cause diseases both in humans and animals. These diseases range from mild to fatal infections thus necessitating development of a specific molecular method for detection of pathogenic S. aureus.

OBJECTIVES

To identify and analyze genetic profile of pathogenic S. aureus using bacteriophage based genetic biomarkers.

METHODS

Using culture and biochemical methods, 148 S. aureus (87 %) were isolated from 170 raw milk samples taken from 10 dairy farms in Marsabit and Isiolo counties in Northern Kenya between June 2016 and February 2017. The samples were collected directly from dairy lactating cows previously diagnosed with S. aureus in a follow-up study. The isolates were analyzed by PCR and sequencing of beta hemolysin (hlb) gene. The genetic relationship between five Kenyan S. aureus isolates and five isolates previously identified was inferred.

RESULTS

From the 96 isolates screened for hlb gene, 75 (78.1%) tested positive. Some of the positive isolates yielded a band size of 975 bp, while others 1100 bp. Through Basic Local Alignment Search Tool (BLAST) search analysis, the two different band sizes (975 bp and 1100 bp) were both confirmed to be hlb gene from S. aureus isolates indicating that the difference in band size may have been due to deletions that were detected in the 975 bp hlb gene. Some S. aureus isolates from Kenya appeared to be closely related to isolates from other parts of the world, while some showed a distant relationship.

CONCLUSIONS

Phage-derived hlb gene is a suitable molecular marker for detection of pathogenic S. aureus.

Diversity, Chemical Constituents, and Biological Activities of Endophytic Fungi Isolated From Ligusticum chuanxiong Hort

The objective of this study was to evaluate the diversity of endophytic fungi of different parts of Ligusticum chuanxiong Hort (CX) and further characterize their biological activities and identify chemical compounds produced by these endophytic fungi. A total of 21 endophytic fungi were isolated and identified from CX. Penicillium oxalicum, Simplicillium sp., and Colletotrichum sp. were identified as promising strains by the color reaction. Comparing different organic extracts of the three strains, it was observed that the ethyl acetate extract of Penicillium oxalicum and Simplicillium sp. and the n-butanol extract of Colletotrichum sp. showed significant antioxidant and antibacterial activities. The ethyl acetate extracts of Penicillium oxalicum had outstanding antioxidant and antibacterial effects, and its radical scavenging rates for ABTS and DPPH were 98.43 ± 0.006% and 90.11 ± 0.032%, respectively. At the same time, their IC₅₀ values were only 0.18 ± 0.02 mg/mL and 0.04 ± 0.003 mg/mL. The ethyl acetate extract of Penicillium oxalicum showed MIC value of only 0.5 mg/mL against Escherichia coli and Staphylococcus aureus. By liquid chromatography-mass spectrometry (LC-MS), we found that Penicillium oxalicum could produce many high-value polyphenols, such as hesperidin (36.06 μmol/g), ferulic acid (1.17 μmol/g), and alternariol (12.64 μmol/g), which can be a potential resource for the pharmaceutical industry. In conclusion, these results increase the diversity of CX endophytic fungi and the antioxidant and antibacterial activities of their secondary metabolites.