Strain relatedness of meticillin-resistant Staphylococcus aureus isolates recovered from patients with repeated bacteraemia

Cross-sectional analysis of risk factors associated with Mugil cephalus in retail fish markets concerning methicillin-resistant Staphylococcus aureus and Aeromonas hydrophila

Introduction

Aeromonas hydrophila and methicillin-resistant Staphylococcus aureus (MRSA) are potent bacterial pathogens posing major hazards to human health via consuming fish harboring these pathogens or by cross-contamination beyond the contaminated environment. The aim of this study was to determine risk variables associated with the presence of certain pathogenic bacteria from Mugil cephalus fish in retail markets in Egypt. The virulence genes of A. hydrophila and S. aureus were also studied. Furthermore, the antibiotic sensitivity and multidrug resistance of the microorganisms were evaluated.

Methods

In a cross-sectional investigation, 370 samples were collected from mullet skin and muscle samples, washing water, fish handlers, knives, and chopping boards. Furthermore, fish handlers' public health implications were assessed via their response to a descriptive questionnaire.

Results

S. aureus and Aeromonas species dominated the investigated samples with percentages of 26.76% and 30.81%, respectively. Furthermore, A. hydrophila and MRSA were the predominant recovered bacterial pathogens among washing water and knives (53.85% and 46.66%, respectively). The virulence markers aerA and hlyA were found in 90.7% and 46.5% of A. hydrophila isolates, respectively. Moreover, the virulence genes nuc and mec were prevalent in 80% and 60% of S. aureus isolates, respectively. Antimicrobial susceptibility results revealed that all A. hydrophila isolates were resistant to amoxicillin and all MRSA isolates were resistant to amoxicillin and ampicillin. Remarkably, multiple drug resistance (MDR) patterns were detected in high proportions in A. hydrophila (88.37%) and MRSA (100%) isolates. The prevalence of Aeromonas spp. and S. aureus had a positive significant correlation with the frequency of handwashing and use of sanitizer in cleaning of instruments. MRSA showed the highest significant prevalence rate in the oldest age category.

Conclusion

The pathogenic bacteria recovered in this study were virulent and had a significant correlation with risk factors associated with improper fish handling. Furthermore, a high frequency of MDR was detected in these pathogenic bacteria, posing a significant risk to food safety and public health.

Risk Factors of Recurrent Infection in Patients with Staphylococcus aureus Bacteremia: a Competing Risk Analysis

Although several clinical variables have been reported as risk factors for recurrence of Staphylococcus aureus infection, most studies have not considered competing risk events that may overestimate the risk. In this study, we performed competing risk analysis to identify risk factors related to 90-day recurrence in patients with S. aureus bacteremia (SAB) using a large cohort data from a single tertiary hospital in South Korea. All adults who experienced SAB during admission were prospectively enrolled from August 2008 to December 2019. After the day of the first positive blood culture, recurrence and all-cause mortality were assessed for 90 days. Recurrence was defined as a development of symptoms or signs of infection with or without repeated bacteremia after >7 days of negative blood culture and clinically apparent improvement. Subdistribution hazard ratios (sHR) for recurrence and all-cause mortality were estimated using Fine and Gray models. Of 1,725 SAB patients, including 885 cases (51.3%) of methicillin-resistant S. aureus (MRSA) bacteremia, 85 (5.0%) experienced recurrence during the study period. In a multivariate Fine and Gray regression model, the presence of a vascular graft (subdistribution HR [sHR], 3.48; 95% confidence interval [CI], 1.90-6.40), nasal MRSA carriage (sHR, 2.10; 95% CI, 1.28-3.44), methicillin resistance (sHR, 1.69; 95% CI, 1.00-2.84), and rifampicin resistance (sHR, 2.20; 95% CI, 1.12-4.33) were significantly associated with 90-day recurrence. In a large cohort of SAB patients with a high prevalence of MRSA, indwelling vascular graft, nasal MRSA carriage, methicillin resistance, and rifampicin resistance were potential risk factors for recurrence of S. aureus infection.

Risk Factors for Recurrent Staphylococcus aureus Bacteremia

BACKGROUND

To understand the clinical, bacterial, and host characteristics associated with recurrent Staphylococcus aureus bacteremia (R-SAB), patients with R-SAB were compared to contemporaneous patients with a single episode of SAB (S-SAB).

METHODS

All SAB isolates underwent spa genotyping. All isolates from R-SAB patients underwent pulsed-field gel electrophoresis (PFGE). PFGE-indistinguishable pairs from 40 patients underwent whole genome sequencing (WGS). Acute phase plasma from R-SAB and S-SAB patients was matched 1:1 for age, race, sex, and bacterial genotype, and underwent cytokine quantification using 25-analyte multiplex bead array.

RESULTS

R-SAB occurred in 69 (9.1%) of the 756 study patients. Of the 69 patients, 30 experienced relapse (43.5%) and 39 reinfection (56.5%). Age, race, hemodialysis dependence, presence of foreign body, methicillin-resistant Staphyloccus aureus, and persistent bacteremia were individually associated with likelihood of recurrence. Multivariate risk modeling revealed that black hemodialysis patients were nearly 2 times more likely (odds ratio [OR] = 9.652 [95% confidence interval [CI], 5.402-17.418]) than white hemodialysis patients (OR = 4.53 [95% CI, 1.696-10.879]) to experience R-SAB. WGS confirmed PFGE interpretations in all cases. Median RANTES (regulated on activation, normal T cell expressed and secreted) levels in acute phase plasma from the initial episode of SAB were higher in R-SAB than in matched S-SAB controls (P = .0053, false discovery rate < 0.10).

CONCLUSION

This study identified several risk factors for R-SAB. The largest risk for R-SAB is among black hemodialysis patients. Higher RANTES levels in R-SAB compared to matched controls warrants further study.

Combination ceftaroline and daptomycin salvage therapy for complicated methicillin-resistant Staphylococcus aureus bacteraemia compared with standard of care

Complicated methicillin-resistant Staphylococcus aureus bloodstream infections (MRSA-BSIs), particularly those with delayed culture clearance, are associated with high mortality. Combination therapy with daptomycin and ceftaroline (DAP+CPT) represents a novel therapeutic approach to MRSA-BSI owing to synergistic bactericidal activity. This study aimed to compare DAP+CPT with historical standard of care (SoC) for treatment of complicated MRSA-BSI. This single-centre retrospective cohort study included patients with complicated MRSA-BSI at University of Colorado Hospital. Patients receiving DAP+CPT for ≥48 h between November 2013 and March 2020 or SoC with vancomycin or DAP ± gentamicin and/or rifampicin from November 2011 to December 2013 were compared. The primary outcome was clinical failure defined as a composite of MRSA-related mortality and recurrent infection at 60 days. A total of 60 patients received DAP+CPT (n = 30) or SoC (n = 30). Median age was 56 years and median Pitt bacteremia score was 3. Common infectious sites were endovascular (63%) and musculoskeletal (40%). DAP+CPT was associated with a numerically lower incidence of clinical failure compared with SoC (20% vs. 43%; P = 0.052). Multivariable analysis controlling for immunocompromised status (OR, 6.90, 95% CI 1.08-44.15), Charlson comorbidity index (OR, 1.12, 95% CI 0.90-1.39) and source control (OR, 0.35, 95% CI 0.08-1.46) associated DAP+CPT with 77% lower odds of clinical failure (OR, 0.23, 95% CI 0.06-0.89). In patients with complicated MRSA-BSI with delayed clearance, DAP+CPT trended towards lower rates of clinical failure than SoC and was significantly associated with decreased clinical failure after adjustment for baseline differences.

Enhancing the Antibacterial Activity of Erythromycin with Titanium Dioxide Nanoparticles against MRSA

BACKGROUND

Staphylococcus aureus (S. aureus) is the most common infectious agent in the community and hospitals. Infections with S. aureus are now becoming difficult to be treated by using conventional antibiotics due to its emerging methicillin-resistant S. aureus (MRSA) strain.

OBJECTIVE

In the present study, MRSA was isolated from clinical samples and evaluated for resistance against different antibiotics, TiO2 nanoparticles, and their combinations.

METHODS

Clinical samples were collected from Ayub Medical Complex (AMC), Abbottabad, Pakistan, and identified by different biochemical tests and polymerase chain reactions (PCR). Kirby-Bauer disk diffusion method was performed to evaluate antimicrobial susceptibility. Minimum Inhibitory Concentration (MIC) of ampicillin, ciprofloxacin, erythromycin, and vancomycin was found out by agar dilution method while the broth dilution method was used for the MIC of TiO2 nanoparticles and their combinations with erythromycin.

RESULTS

All 13/100 (13%) MRSA were successfully identified. All isolates were susceptible to quinupristin/ dalfopristin, teicoplanin, and vancomycin, while the highest resistance was seen with erythromycin, penicillin, and tetracycline. MIC showed high resistance against ampicillin (0.25-512 mg/L) and erythromycin (0.25-1024 mg/L).

CONCLUSION

The MIC value of 2 mM TiO2 nanoparticles was found to be the most effective concentration after 12 h of incubation, while the combination of erythromycin with 3 mM TiO2 nanoparticles was found to be more potent which significantly lowered down the MIC of erythromycin to 2-16 mg/L.

Association between treatment duration and mortality or relapse in adult patients with Staphylococcus aureus bacteraemia: a retrospective cohort study

OBJECTIVES

The aim was to evaluate the effect of duration of therapy (DOT) on mortality and relapse for patients with Staphylococcus aureus bacteraemia (SAB).

METHODS

We performed a retrospective single-centre cohort study including adult patients with SAB. We determined the association between DOT (≤14 days versus >14 days) and mortality by adjusted hazard ratios (aHR) and 95% confidence intervals through Cox regression adjusted for immortal-time bias and confounding by indication, stratified by presence of complicated SAB (any of: endocarditis, implant, duration of SAB >2 days, fever >3 days). The primary outcome was 90-day all-cause mortality, and the secondary outcome was 90-day relapse.

RESULTS

Between January 2010 and December 2015, we included 530 patients, of whom 94 out of 530 (17.7%) had methicillin-resistant SAB and 305 out of 530 (57.6%) had complicated SAB. Ninety-day mortality was 27.0% (143/530), with no significant trend across the study period; median time to death was 17 days (interquartile range (IQR) 8-30) after onset of SAB. Median DOT was 20 days (IQR 13-39). Patients with complicated SAB had significantly reduced mortality with DOT >14 days (aHR 0.32, 95% CI 0.16-0.64). DOT was not associated with mortality in patients with uncomplicated SAB (aHR 0.85; 0.41-1.78). Eighteen (18/530) patients (3.4%) relapsed; on univariate analysis, DOT was not associated with relapse (HR 1.01; 0.97-1.06).

CONCLUSIONS

DOT >14 days is associated with higher survival in patients with complicated SAB, but not for patients with uncomplicated SAB. No association was found for relapse, but 90-day relapse was very low in this cohort. Importantly, 90-day mortality remained high across the study period.

Clinical and microbiologic characteristics of adult patients with recurrent bacteraemia caused by extended-spectrum β-lactamase-producing Escherichia coli or Klebsiella pneumoniae

The characteristics of patients with recurrent bacteraemia caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli or Klebsiella pneumoniae (EK) are rarely described. Flomoxef belongs to the cephamycins group and demonstrates in vitro activity against ESBL-producing organisms. Whether flomoxef may be used for the treatment of such infections remains controversial. This retrospective case-control study enrolled adult patients who had bacteraemia caused by ESBL-EK during 2005-2011. Case patients were those who had more than one episode of ESBL-EK bacteraemia. Controls were those who were matched for age and interval time of blood sampling and had only one episode of ESBL-EK bacteraemia with subsequent bacteraemia episodes caused by other non-ESBL-EK bacteria. Pulsed-field gel electrophoresis and microbiologic profiles of the initial and subsequent ESBL-EK isolates were analysed. During the study period, 424 patients were found to have at least one positive blood culture after the first ESBL-EK bacteraemia episode, and 67 (15.8%) had a second episode of ESBL-EK bacteraemia. Bacteraemia resulting from vascular catheter-related infection (odds ratio, 3.24; 95% confidence interval, 1.31-8.05), and definitive therapy with flomoxef (odds ratio, 2.99; 95% confidence interval, 1.10-8.15) were both independent risk factors for the recurrence. Among the 56 patients with available ESBL-EK isolates for analysis, 38 (67.8%) were infected by genetically similar strains. In three of these 38 recurrent ESBL-EK bacteraemia cases caused by an identical strain, the minimum inhibitory concentrations of carbapenem for the subsequent K. pneumoniae isolates were fourfold or higher than the initial isolates. Recurrent bacteraemia was not uncommon in our patients with ESBL-EK bacteraemia, and most of the episodes were caused by identical strains.

Molecular Epidemiology of Recurrent Cutaneous Methicillin-Resistant Staphylococcus aureus Infections in Children

We assessed the relatedness by repetitive-sequence polymerase chain reaction of isolates obtained from children with recurrent methicillin-resistant Staphylococcus aureus cutaneous infections over 6 years. Ninety percent of the cases could be attributed to recurrence of the same strain type, suggesting that optimized decolonization methods in children might effectively prevent recurrent infection.

Recurrent community-associated Staphylococcus aureus infections in children presenting to Texas Children's Hospital in Houston, Texas

BACKGROUND

There are limited data characterizing recurrent staphylococcal disease in children. We sought to define the clinical features and laboratory findings of children with recurrent community-associated Staphylococcus aureus infections presenting to Texas Children's Hospital in Houston, TX.

METHODS

Medical records of children with recurrent, culture-proven community-associated S. aureus infections at Texas Children's Hospital from 8/1/2001 to 7/29/2009 were reviewed, and antibiotic susceptibility patterns were obtained for all S. aureus isolates.

RESULTS

Six hundred ninety-four otherwise healthy patients presented to Texas Children's Hospital with 2-7 episodes of community-associated S. aureus infection, accounting for 1495 encounters, 823 hospitalizations and 3337 inpatient days. In 90% of patients with ≤12 months separating their initial and recurrent infections, the methicillin susceptibility of the initial and recurrent isolates was the same, compared with 79% of patients with > 12 months separating their infections. The overall antibiotic susceptibility pattern did not change between isolates in 71% of otherwise healthy children compared with only 33% of children with eczema. Ninety-two percent of otherwise healthy children had only recurrent skin and soft tissue infections; 8% had ≥1 non-skin and soft tissue infections. The location of skin and soft tissue infections varied by age, with children≤36 months of age being more likely to have ≥1 S. aureus infection located in the diaper area.

CONCLUSIONS

Our study demonstrates that recurrent staphylococcal disease requiring emergency center or inpatient care is common, accounting for significant utilization of hospital resources. Children with recurrent staphylococcal infections are likely to have repeated infections from the same staphylococcal strain (by antibiotic susceptibility pattern), indicating that persistent colonization, frequent exposure to others who are chronically colonized, or environmental contamination is playing a role in recurrent disease. Finally, our study emphasizes the need for repeat cultures in children with recurrent disease, as 29% of healthy children and 67% of children with a predisposing risk factor (such as eczema) have a change in the antibiotic susceptibility pattern between S. aureus isolates.

Trends in the susceptibility of methicillin-resistant Staphylococcus aureus to nine antimicrobial agents, including ceftobiprole, nemonoxacin, and tyrothricin: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006-2010

This study investigated the in vitro susceptibilities of methicillin-resistant Staphylococcus aureus (MRSA) to nine antimicrobial agents in Taiwan. A total of 1,725 isolates were obtained from 20 hospitals throughout Taiwan from 2006 to 2010. The minimum inhibitory concentrations (MICs) of the nine agents were determined by the agar dilution method. The MICs of mupirocin and tyrothricin were determined for 223 MRSA isolates collected from 2009 to 2010. For vancomycin, 99.7 % were susceptible; however, 30.0 % (n = 517) exhibited MICs of 2 μg/ml and 0.3 % (n = 6) demonstrated intermediate susceptibility (MICs of 4 μg/ml). Nearly all isolates (≥ 99.9 %) were susceptible to teicoplanin, linezolid, and daptomycin. The MIC90 values were 2 μg/ml for ceftobiprole and 1 μg/ml for nemonoxacin. The MIC90 values of mupirocin and tyrothricin were 0.12 and 4 μg/ml, respectively. MIC creep was noted for daptomycin during this period, but not for vancomycin, teicoplanin, linezolid, or tigecycline. For isolates with vancomycin MICs of 2 μg/ml, the MIC90 values were 2 μg/ml for teicoplanin, 0.5 μg/ml for daptomycin, and 0.5 μg/ml for tigecycline. Those values were four- to eight-fold higher than those among isolates with vancomycin MICs of 0.5 μg/ml (2, 0.06, and 0.12 μg/ml, respectively). Of the nine MRSA isolates exhibiting non-susceptibility to vancomycin (n = 6), teicoplanin (n = 1), daptomycin (n = 2), or tigecycline (n = 1), all had different pulsotypes, indicating the absence of intra-hospital or inter-hospital spread. The presence of a high proportion of MRSA isolates with elevated MICs (2 μg/ml) and MIC creep of daptomycin might alert clinicians on the therapy for serious MRSA infections in Taiwan.

Occurrence of and risk factors for methicillin-resistant Staphylococcus aureus at a teaching hospital in Philadelphia

Manual medical record mining and data analysis were performed at a tertiary care university teaching hospital to establish the rate of occurrence of and risk factors for infection with methicillin-resistant Staphylococcus aureus (MRSA). Patients with surgical site infections had the highest rate of MRSA infection, representing 59% of the MRSA infections recorded. The mortality rate in patients with relapsed MRSA was 45% (13 of 30), compared with no deaths in 149 new MRSA cases. The majority of deaths in patients with relapsed MRSA occurred in the intensive care unit.

Molecular typing and phenotype characterization of methicillin-resistant Staphylococcus aureus isolates from blood in Taiwan

Background

Staphylococcus aureus causes a variety of severe infections such as bacteremia and sepsis. At present, 60–80% of S. aureus isolates from Taiwan are methicillin resistant (MRSA). It has been shown that certain MRSA clones circulate worldwide. The goals of this study were to identify MRSA clones in Taiwan and to correlate the molecular types of isolates with their phenotypes.

Methods

A total of 157 MRSA isolates from bacteremic patients were collected from nine medical centers. They were typed based on polymorphisms in agr, SCCmec, MLST, spa, and dru. Phenotypes characterized included Panton-Valentine leucocidin (pvl), inducible macrolide-lincosamide-streptogramin B resistance (MLSBi), vancomycin (VA) and daptomycin (DAP) minimal inhibitory concentrations (MIC), and superantigenic toxin gene profiles. Difference between two consecutive samples was determined by Mann-Whitney-U test, and difference between two categorical variables was determined by Fisher's exact test.

Results

Four major MRSA clone complexes CC1, CC5, CC8, and CC59 were found, including 4 CC1, 9 CC5, 111 CC8, and 28 CC59 isolates. These clones had the following molecular types: CC1: SCCmecIV and ST573; CC5: SCCmecII and ST5; CC8: SCCmecIII, ST239, and ST241, and CC59: SCCmecIV, SCCmecV_T, ST59, and ST338. The toxin gene profiles of these clones were CC1: sec-seg-(sei)-sell-selm-(seln)-selo; CC5: sec-seg-sei-sell-selm-(seln)-selp-tst1; CC8: sea-selk-selq, and CC59: seb-selk-selq. Most isolates with SCCmecV_T, ST59, spat437, and dru11 types were pvl⁺ (13 isolates), while multidrug resistance (≥4 antimicrobials) were associated with SCCmecIII, ST239, spa t037, agrI, and dru14 (119 isolates) (p<0.001). One hundred and twenty four isolates with the following molecular types had higher VA MIC: SCCmecII and SCCmecIII; ST5, ST239, and ST241; spa t002, t037, and t421; dru4, dru10, dru12, dru13, and dru14 (p<0.05). No particular molecular types were found to be associated with MLSBi phenotype.

Conclusions

Four major MRSA clone complexes were found in Taiwan. Further studies are needed to delineate the evolution of MRSA isolates.

Predictors of relapse of methicillin-resistant Staphylococcus aureus bacteremia after treatment with vancomycin

The risk factors for relapse of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia after vancomycin treatment are unknown. Diversilab typing was used to classify recurrent bacteremia as relapse or reinfection. Bacteremia for >7 days and staphylococcal cassette chromosome mec element (SCCmec) type II were independently associated with relapse of MRSA bacteremia after vancomycin treatment.

Treatment considerations for recurrent MRSA bacteremia leading to cholecystitis

We present an end-stage renal disease patient with acute cholecystitis caused by a recurrence of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. Timely antibiotic therapy with vancomycin did not eradicate the patient's infection. In this patient, the minimum inhibitory concentration (MIC) of the organism for vancomycin was at the upper limit of susceptibility. The ability to thoroughly understand and interpret mean inhibitory concentrations is crucial in antibiotic selection. For high-risk patients with Staphylococcus aureus infection with reduced susceptibility to vancomycin as demonstrated by an MIC of 2 mg/L or greater, we suggest further investigation into linezolid as an alternative antibiotic to vancomycin therapy. Compared to vancomycin, linezolid has similar effectiveness in patients with MRSA bacteremia as well as improved penetration, particularly in bile.

Molecular analysis of repeated methicillin-resistant Staphylococcus aureus infections in children

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen that causes severe morbidity and mortality in hospitalized patients. It is unclear whether repeated MRSA infections in pediatric patients are caused by relapse of previous infecting strains or by acquiring new strains from extrinsic sources. The study aimed to define the genetic relatedness of MRSA isolates from children with repeated infections.

Methodology/Principal Findings

Children with multiple MRSA infections during 2004–2006 were identified in a teaching hospital. Repeated infections were confirmed by chart review and the responsible isolates were genotyped and screened for Panton-Valentine leukocidin (PVL) genes. Two consecutive episodes comprised an infection pair, and strain relatedness was defined for each pair as indistinguishable, highly related, or distinct if the isolates were of the same subtype, the same genotype, or different genotype, respectively. A total of 114 episodes comprising 66 infection pairs were identified in 48 children. The interval of infection pairs ranged from 15 days to 346 days, with a median duration of 57.5 days. Genotypings classified all isolates into 7 genotypes and 31 subtypes. Of 66 pairs, 46 (69.7%), 13 (19.7%) and 7 (10.6%) pairs were caused by indistinguishable, highly related and distinct strains, respectively. Subsequent infections caused by indistinguishable strains were more common for PVL-positive strains (17/18, 94.4%) than for PVL-negative strains (29/48, 60.4%, P = 0.007). The strain relatedness was not affected by the durations of interval between infections.

Conclusions/Significance

Most repeated MRSA infections in children are caused by indistinguishable strains even after a long period of interval, suggesting that persistent carriage and relapse of initial infecting strains were responsible for the majority of recurrent MRSA infections.

Animal and human antibodies to distinct Staphylococcus aureus antigens mutually neutralize opsonic killing and protection in mice

New prophylactic approaches are needed to control infection with the Gram-positive bacterium Staphylococcus aureus, which is a major cause of nosocomial and community-acquired infections. To develop these, greater understanding of protective immunity against S. aureus infection is needed. Human immunity to extracellular Gram-positive bacterial pathogens is primarily mediated by opsonic killing (OPK) via antibodies specific for surface polysaccharides. S. aureus expresses two such antigens, capsular polysaccharide (CP) and poly-N-acetyl glucosamine (PNAG). Here, we have shown that immunization-induced polyclonal animal antisera and monoclonal antibodies specific for either CP or PNAG antigens have excellent in vitro OPK activity in human blood but that when mixed together they show potent interference in OPK activity. In addition, reductions in antibody binding to the bacterial surface, complement deposition, and passive protection were seen in two mouse models of S. aureus infection. Electron microscopy, isothermal calorimetry, and surface plasmon resonance indicated that antibodies to CP and PNAG bound together via an apparent idiotype-anti-idiotype interaction. This interaction was also found in sera from humans with S. aureus bacteremia. These findings suggest that the lack of effective immunity to S. aureus infections in humans could be due, in part, to interference in OPK when antibodies to CP and PNAG antigens are both present. This information could be used to better design S. aureus vaccine components.