Methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci co-colonization in patients: A meta-analysis

Mechanisms of acquisition of the vanA operon among vancomycin-resistant Staphylococcus aureus genomes: The tip of the iceberg?

BACKGROUND

Vancomycin is frequently used as a last line of defence against infections due to multidrug-resistant Staphylococcus aureus (S. aureus). A recent finding described the acquisition of vancomycin-resistant S. aureus strains by the integration of an enterococcal plasmid containing the vanA operon into the S. aureus chromosome via homologous recombination involving a specific integration site called locus L2.

METHODS

To characterise all mechanisms of acquisition of vanA, this study analysed the 15 706 S. aureus genomes to look for vanA and described its genetic environment.

RESULTS

A complete vanA operon was found in 25 S. aureus strains isolated from 12 patients, including nine co-isolated with vancomycin-resistant Enterococcus strains. VanA was found within transposon Tn1546-like elements on 17 plasmids and eight chromosomes. VanA might be acquired through conjugation of enterococcal and staphylococcal plasmids, transposition of Tn1546 carrying vanA and plasmid integration into the chromosome. Further, L2 was detected in 2087 genomes (13.3%) of S. aureus strains across different continents. Six potential chromosomal hotspots for integration of the entire vanA-containing enterococcal plasmid were identified by homologous recombination via L2.

CONCLUSIONS

These findings suggest that the recently described scenario in a New York patient could be reproduced anywhere. Surveillance of this possibility is mandatory, especially in patients with vancomycin-resistant Enterococcus infection or colonisation.

Vancomycin-Resistant Enterococcus faecium and the emergence of new Sequence Types associated with Hospital Infection

Enterococcus faecium is a major cause of vancomycin-resistant enterococcal (VRE) infection. New variants of the pathogen have emerged and become dominant in healthcare settings. Two such examples, vanB ST796 and vanA ST1421 sequence types, originally arose in Australia and proceeded to cause VRE outbreaks in other countries. Of concern is the detection of a vancomycin variable enterococcal (VVE) variant of ST1421 in Europe that exhibits a vancomycin-susceptible phenotype but which can revert to resistant in the presence of vancomycin. The recent application of genome sequencing for increasing our understanding of the evolution and spread of VRE is also explored here.

Synergistic effects of length of stay and prior MDRO carriage on the colonization and co-colonization of methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and carbapenemase-producing Enterobacterales across healthcare settings

OBJECTIVE

To characterize the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and carbapenemase-producing Enterobacterales (CPE) co-colonization and to compare risk factors between healthcare facility types.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a 3-year cross-sectional study among patients admitted to an acute-care hospital (ACH) and its 6 closely affiliated intermediate- and long-term care facilities (ILTCFs) in Singapore in June and July of 2014-2016.

METHODS

Specimens were concurrently collected from nares, axillae, and groins for MRSA detection, and from rectum or stool for VRE and CPE detection. Co-colonization was defined as having >1 positive culture of MRSA/VRE/CPE. Multinomial logistic regression was performed to determine predictors of co-colonization.

RESULTS

Of 5,456 patients recruited, 176 (3.2%) were co-colonized, with higher prevalence among patients in ITCFs (53 of 1,255, 4.2%) and the ACH (120 of 3,044, 3.9%) than LTCFs (3 of 1,157, 0.3%). MRSA/VRE was the most common type of co-colonization (162 of 5,456, 3.0%). Independent risk factors for co-colonization included male sex (odds ratio [OR], 1.96; 95% confidence interval [CI], 1.37-2.80), prior antibiotic therapy of 1-3 days (OR, 10.39; 95% CI, 2.08-51.96), 4-7 days (OR, 4.89; 95% CI, 1.01-23.68), >7 days (OR, 11.72; 95% CI, 2.81-48.85), and having an open wound (OR, 2.34; 95% CI, 1.66-3.29). Additionally, we detected the synergistic interaction of length of stay >14 days and prior multidrug-resistant organism (MDRO) carriage on co-colonization. Having an emergency surgery was a significant predictor of co-colonization in ACH patients, and we detected a dose-response association between duration of antibiotic therapy and co-colonization in ILTCF patients.

CONCLUSIONS

We observed common and differential risk factors for MDRO co-colonization across healthcare settings. This study has identified at-risk groups that merit intensive interventions, particularly patients with prior MDRO carriage and longer length of stay.

Antibiotic-Loaded Amphiphilic Chitosan Nanoparticles Target Macrophages and Kill an Intracellular Pathogen

In this work, levofloxacin (LVX), a third-generation fluoroquinolone antibiotic, is encapsulated within amphiphilic polymeric nanoparticles of a chitosan-g-poly(methyl methacrylate) produced by self-assembly and physically stabilized by ionotropic crosslinking with sodium tripolyphosphate. Non-crosslinked nanoparticles display a size of 29 nm and a zeta-potential of +36 mV, while the crosslinked counterparts display 45 nm and +24 mV, respectively. The cell compatibility, uptake, and intracellular trafficking are characterized in the murine alveolar macrophage cell line MH-S and the human bronchial epithelial cell line BEAS-2B in vitro. Internalization events are detected after 10 min and the uptake is inhibited by several endocytosis inhibitors, indicating the involvement of complex endocytic pathways. In addition, the nanoparticles are detected in the lysosomal compartment. Then, the antibacterial efficacy of LVX-loaded nanoformulations (50% w/w drug content) is assessed in MH-S and BEAS-2B cells infected with Staphylococcus aureus and the bacterial burden is decreased by 49% and 46%, respectively. In contrast, free LVX leads to a decrease of 8% and 5%, respectively, in the same infected cell lines. Finally, intravenous injection to a zebrafish larval model shows that the nanoparticles accumulate in macrophages and endothelium and demonstrate the promise of these amphiphilic nanoparticles to target intracellular infections.

Clinical and microbiological characteristics of bloodstream infections caused by Enterococcus spp. within internal medicine wards: a two-year single-centre experience

Enterococcal bloodstream infections (E-BSI) constitute the second cause of Gram-positive bacterial BSI in Europe with a high rate of in-hospital mortality. Furthermore, E-BSI treatment is still challenging because of intrinsic and acquired antibiotic resistances. We conducted a retrospective, 2-year, observational, single-centre study to evaluate clinical outcome and risk factors for E-BSI mortality in internal medicine wards. 201patients with E-BSI were included in the analysis. Infection rate was 2.4/1000 days of hospital admission. Most E-BSI were hospital acquired (78.1%). The median age was 68 years. Charlson Comorbidity Index, adjusted for age, was 5 (range 4-6). Patients with E-BSI frequently had at least one invasive device, predominantly a central venous (73%) or a bladder catheter (61.7%). Enterococcus faecium accounted for 47.94% of E-BSI (resistance rate to ampicillin or vancomycin was 22.2 and 23.3%, respectively) and Enterococcus faecalis for 52.08% (resistance rate to ampicillin or vancomycin was 3.1 and 2.2%, respectively). Among all E-BSI, 25% of patients received appropriate therapy. In total, 59% of E-BSI underwent echocardiography. At the multivariate analysis, resistance to vancomycin (OR 2.09, p = 0.025), sepsis (OR 2.57, p = 0.003) and septic shock (OR 3.82, p = 0.004) was a predictor of mortality. No difference in 28-day survival was observed between appropriate or inappropriate treatment, except for endocarditis. However, E-BSI sources in clinical practices are not always properly investigated, including the rule-out of intracardiac vegetations. We did not demonstrate a difference in mortality for inappropriate therapy in the absence of endocarditis in comorbid patients with a long history of medicalization.

Teicoplanin combined with conventional vancomycin therapy for the treatment of pulmonary methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis infections

BACKGROUND

Vancomycin and teicoplanin are both antibiotics that have significant antimicrobial effects on Gram-positive cocci.

AIM

To explore the value of teicoplanin combined with conventional (vancomycin only) anti-infective therapy for the treatment of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis pulmonary infections.

METHODS

A total of 86 patients with methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus epidermidis pulmonary infections, treated in our hospital between January 2018 and February 2020, were assigned to the study and control groups using a random number table method, with 43 patients in each group. The control group received conventional treatment (vancomycin), and the study group received both teicoplanin and conventional treatment. The following indicators were assessed in both groups: the time required for symptom relief, treatment effectiveness, serum levels of inflammatory factors (procalcitonin, interleukin-1β, tumor necrosis factor-α, C-reactive protein), clinical pulmonary infection scores before and after treatment, and the incidence of adverse reactions.

RESULTS

Patients in the study group were observed to have faster cough and expectoration resolution, white blood cell count normalization, body temperature normalization, and rales disappearance than patients in the control group (all P < 0.05); the total rate of effectiveness was 93.02% in the study group, higher than the 76.74% in the control group (P < 0.05). The pre-treatment serum levels of procalcitonin, interleukin-1β, tumor necrosis factor-α, and C-reactive protein as well as the clinical pulmonary infection scores were similar among the patients in both groups. However, the post-treatment serum levels of procalcitonin, interleukin-1β, tumor necrosis factor-α, and C-reactive protein as well as the clinical pulmonary infection scores were significantly lower in the study group than in the control group (P < 0.05). There was no significant difference in the incidence of adverse reactions between the groups.

CONCLUSION

Compared with conventional (vancomycin only) therapy, teicoplanin and vancomycin combination therapy for patients with pulmonary methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis infections can improve patient clinical symptoms, modulate serum inflammatory factor levels, and improve treatment efficacy, without increasing the risk of adverse reactions.