Clinical failure of vancomycin treatment of Staphylococcus aureus infection in a tertiary care hospital in southern Brazil

Efflux Pump (QacA, QacB, and QacC) and β-Lactamase Inhibitors? An Evaluation of 1,8-Naphthyridines against Staphylococcus aureus Strains

The bacterial species Staphylococcus aureus presents a variety of resistance mechanisms, among which the expression of β-lactamases and efflux pumps stand out for providing a significant degree of resistance to clinically relevant antibiotics. The 1,8-naphthyridines are nitrogen heterocycles with a broad spectrum of biological activities and, as such, are promising research targets. However, the potential roles of these compounds on bacterial resistance management remain to be better investigated. Therefore, the present study evaluated the antibacterial activity of 1,8-naphthyridine sulfonamides, addressing their ability to act as inhibitors of β-lactamases and efflux pump (QacA/B and QacC) against the strains SA-K4414 and SA-K4100 of S. aureus. All substances were prepared at an initial concentration of 1024 μg/mL, and their minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. Subsequently, their effects on β-lactamase- and efflux pump-mediated antibiotic resistance was evaluated from the reduction of the MIC of ethidium bromide (EtBr) and β-lactam antibiotics, respectively. The 1,8-naphthyridines did not present direct antibacterial activity against the strains SA-K4414 and SA-K4100 of S. aureus. On the other hand, when associated with antibiotics against both strains, the compounds reduced the MIC of EtBr and β-lactam antibiotics, suggesting that they may act by inhibiting β-lactamases and efflux pumps such as QacC and QacA/B. However, further research is required to elucidate the molecular mechanisms underlying these observed effects.

Parenterally administered vancomycin in 29 dogs and 7 cats (2003-2017)

Background

Vancomycin is commonly used to treat resistant bacterial infections in people. Reported adverse effects of vancomycin in people include acute kidney injury (AKI), neutropenia, and systemic allergic reaction. Given the increased incidence of vancomycin‐resistant bacterial infections in people, support is growing for restriction of vancomycin.

Objectives

To evaluate the use of intravenous (IV) vancomycin in a university teaching hospital and to describe potential adverse effects.

Animals

Twenty‐nine dogs and 7 cats.

Methods

Medical records of dogs and cats treated with IV vancomycin at the Foster Hospital for Small Animals between January 2003 and October 2017 were reviewed. Information recorded included signalment, infection source, vancomycin dosing, potential adverse effects, and outcome.

Results

Vancomycin was used to treat infections from a range of sources with a variety of dosing intervals. The most common bacterial isolates susceptible to vancomycin included Enterococcus sp. (11/36, 30.6%), methicillin‐resistant Staphylococcus aureus (8/36, 22.2%), and methicillin‐resistant Staphylococcus pseudintermedius (2/36, 5.6%). AKI occurred in 6 of 36 patients (16.7%) during vancomycin treatment but could not definitively be attributed to vancomycin treatment in any patients because of illness severity, additional nephrotoxic treatments, or both. Neutropenia or allergic reaction was not documented in any animal. In 2 of 36 patients (5.6%), susceptibility data documented an infection that was only susceptible to vancomycin. Most patients survived to discharge (25/36, 69.4%).

Conclusions and Clinical Importance

Adverse effects attributable to vancomycin were infrequent in dogs and cats. In most cases, there were potential alternative effective antimicrobials or lack of susceptibility data to support vancomycin treatment.

The safety and efficacy of high versus low vancomycin trough levels in the treatment of patients with infections caused by methicillin-resistant Staphylococcus aureus: a meta-analysis

BACKGROUND

Recent guidelines have recommended vancomycin trough levels of 15-20 mg/L for treatment of serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA). However, high trough levels may increase risk of nephrotoxicity and mortality, and high vancomycin trough levels have not been well studied. This study was designed to combine safety and efficacy results from independent studies and to compare between high and low vancomycin trough levels in the treatment of MRSA-infected patients using meta-analysis.

METHODS

From 19 eligible studies, 9 studies were included in meta-analysis to compare clinical success between high and low vancomycin trough levels, while 10 and 11 studies met criteria for comparing trough levels and nephrotoxicity and trough levels and mortality, respectively. The PubMed/Medline, Web of Science, and Scopus databases, and hand searching were used to identify eligible studies dated up to March 2016. Of 2344 subjects with MRSA infection, 1036 were assigned to trough levels ≥15 mg/L and 1308 to trough levels <15 mg/L.

RESULTS

High vancomycin trough levels were found to be associated with risk of nephrotoxicity (odds ratio [OR] 2.14, 95 % confidence interval [CI] 1.42-3.23 and adjusted OR 3.33, 95 % CI 1.91-5.79). There was no evidence of difference between high and low vancomycin trough levels for mortality (OR; 1.09; 95 % CI 0.75-1.60) or clinical success (OR 1.07; 95 % CI 0.68-1.68).

CONCLUSION

In this study, high vancomycin trough levels were identified as an independent factor associated with risk of nephrotoxicity in MRSA-infected patients. Association between vancomycin trough levels and both adverse effects and clinical outcomes requires further study.

Molecular epidemiology of heteroresistant vancomycin-intermediate Staphylococcus aureus in Brazil

To determine the epidemiological and molecular characteristics of 12 Staphylococcus aureus isolates presenting heteroresistance to vancomycin in laboratories of two cities in Santa Catarina, southern Brazil. Epidemiological data, including the city of isolation, health institution, and date of isolation were considered, as well as the associated clinical specimen. For molecular characterization, we analyzed the staphylococcal cassette chromosome types, the erm gene presence, and the genomic diversity of isolates using pulsed-field gel electrophoresis. The 12 isolates of S. aureus were previously confirmed as heteroresistance to vancomycin using the population analysis profile–area under curve. Regarding genetic variability, two clones were detected: the main one (clone A) composed of four isolates and the clones B, with two isolates. For clone A, two isolates presented identical band patterns and were related to the same hospital, with an interval of 57 days between their isolation. The other isolates of this clone showed no epidemiological link between them because they were isolated in different hospitals and had no temporal relationship. The other clone showed no detectable epidemiological relationship. The heteroresistance to vancomycin recovered in Santa Catarina State from 2009 to 2012 had, in general, heterogeneous genomic patterns based on pulsed-field gel electrophoresis results, which is in accordance with the fact that these isolates had little or no epidemiological relationship among them. Due to the characteristic phenotypic instability and often prolonged vancomycin therapy for selection, clonal spread is not as common as for other resistance mechanisms disseminated through horizontal gene transfer.

The multifaceted resources and microevolution of the successful human and animal pathogen methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important bacterial pathogens based on its incidence and the severity of its associated infections. In addition, severe MRSA infections can occur in hospitalised patients or healthy individuals from the community. Studies have shown the infiltration of MRSA isolates of community origin into hospitals and variants of hospital-associated MRSA have caused infections in the community. These rapid epidemiological changes represent a challenge for the molecular characterisation of such bacteria as a hospital or community-acquired pathogen. To efficiently control the spread of MRSA, it is important to promptly detect the mecA gene, which is the determinant of methicillin resistance, using a polymerase chain reaction-based test or other rapidly and accurate methods that detect the mecA product penicillin-binding protein (PBP)2a or PBP2'. The recent emergence of MRSA isolates that harbour a mecA allotype, i.e., the mecC gene, infecting animals and humans has raised an additional and significant issue regarding MRSA laboratory detection. Antimicrobial drugs for MRSA therapy are becoming depleted and vancomycin is still the main choice in many cases. In this review, we present an overview of MRSA infections in community and healthcare settings with focus on recent changes in the global epidemiology, with special reference to the MRSA picture in Brazil.

Carriage frequency, phenotypic and genotypic characteristics of Staphylococcus aureus isolated from dialysis and kidney tranplant patients at a hosptial in northern paraná

The objective of the present study was to determine the frequency of Staphylococcus aureus nasal carriage among dialysis and kidney transplant patients, to identify the antimicrobial resistance profile of these strains and to verify their genetic profiles with the RW3A primer. The study included 159 individuals, comprising 111 dialysis and 48 kidney transplant patients. Of the 48 transplant patients, 75% were positive for S. aureus, whereas 49% of the 111 dialysis patients were carriers. Two samples yielded conflicting results for oxacillin sensitivity between the disk diffusion and minimum inhibitory concentration (MIC) assays: both were sensitive by the disk diffusion assay and resistant by MIC (4 μg/ml). In the antibiogram by disk diffusion, ten samples were resistant to cefoxitin, among which eight were also resistant to oxacillin. The resistance of the ten samples to cefoxitin by the disk diffusion assay was confirmed by MIC. Of the ten oxacillin-resistant samples, eight harbored the mecA gene. All samples were sensitive to vancomycin, and most were resistant to penicillin and demonstrated high rates of resistance to the other antimicrobials tested. The samples from dialysis patients exhibited a more homogenous genetic profile. Among the samples with a high percent similarity, no correlation with sensitivity or resistance to oxacillin was observed. According to the results of this study, the implementation of prevention and control measures, such as increased restrictions on prescriptions for antimicrobial drugs and nasal decontamination prior to high-risk procedures, is recommended.

The clinical significance of vancomycin minimum inhibitory concentration in Staphylococcus aureus infections: a systematic review and meta-analysis

BACKGROUND

Emerging data suggest that vancomycin may be less effective against serious methicillin-resistant Staphylococcus aureus (MRSA) infections with minimum inhibitory concentration (MIC) values at the higher end of the susceptibility range. The purpose of this review is to examine the strength of these associations.

METHODS

All relevant studies pertaining to treatment outcomes or mortality associated with vancomycin MIC were retrieved from the medical literature from January 1996 through August 2011 and analyzed according to Cochrane guidelines.

RESULTS

Of the 270 studies identified, 48 studies were reviewed, with 22 studies included in the final meta-analysis. Vancomycin MIC was significantly associated with mortality for MRSA infection irrespective of the source of infection or MIC methodology (odds ratio [OR], 1.64; 95% confidence interval [CI], 1.14-2.37; P < .01). This mortality association was predominantly driven by bloodstream infections (BSIs; OR, 1.58; 95% CI, 1.06-2.37; P = .03) and isolates with a vancomycin MIC of 2 μg/mL by Etest (OR, 1.72; 95% CI, 1.34-2.21; P < .01). Vancomycin MIC was significantly associated with treatment failure irrespective of source of infection or MIC methodology (OR, 2.69; 95% CI, 1.60-4.51; P < .01).

CONCLUSION

High vancomycin MIC was associated with a higher mortality rate in MRSA BSI. Thus, institutions should consider conducting Etest MICs on all MRSA BSI isolates. Although these data highlight concerns about vancomycin, currently, there are no data to support better survival rates with alternative antibiotics. Data are sorely needed to determine whether other agents can remedy these outcomes observed with vancomycin for MRSA infections with elevated vancomycin MIC values.

Daptomycin compared to standard therapy for the treatment of native valve endocarditis

INTRODUCTION

In a recent randomized trial of Staphylococcus aureus bacteremia and native valve endocarditis, daptomycin was found not inferior to standard therapy. We summarized findings in the subgroup of patients with endocarditis according to the Duke criteria.

METHODS

Patients were randomly assigned to receive daptomycin 6 mg/kg/day or standard therapy (vancomycin 1g every 12h or antistaphylococcal penicillin 2g every 4h, both with gentamicin 1mg/kg every 8h for the first 4 days). The primary end point was success in the modified intent-to-treat population 6 weeks after the end of therapy.

RESULTS

Fifty-three patients were included: 35 with right-sided endocarditis (RIE) and 18 with left-sided endocarditis (LIE). The success rates in patients with RIE were similar between daptomycin and the comparator (42% vs 44%). Patients with RIE with septic pulmonary infarcts responded similarly to treatment with daptomycin and standard therapy (60% vs 67%). In the LIE population, treatment success rates were poor in both arms (11% vs 22%).

CONCLUSION

Daptomycin is an efficacious and well-tolerated alternative to standard therapy in the treatment of RIE. Patients with LIE had a poor outcome regardless of the treatment received. Daptomycin is also effective in treating endocarditis with septic pulmonary infarcts.

Vancomycin: understanding its past and preserving its future

The increase in vancomycin use in the 1980s to treat antibiotic-associated colitis and methicillin-resistant Staphylococcus aureus (MRSA) is largely responsible for the appearance of vancomycin-resistant enterococcus, which in turn spawned isolated cases of vancomycin-resistant S. aureus. Perhaps most worrisome to clinicians are strains of MRSA that are heteroresistant to vancomycin; these isolates are difficult to detect. Appropriate use of vancomycin coupled with awareness of infection control measures is paramount to abrogating the emergence of new vancomycin-resistant MRSA organisms and preserving its future efficacy. The continued reliance on vancomycin for the treatment of MRSA infections will depend on whether vancomycin resistance can be minimized. Newer antibacterial agents, particularly those with activity toward MRSA and vancomycin-resistant enterococcus, such as linezolid, quinupristin/dalfopristin, daptomycin, and tigecycline, may take a more prominent clinical role when gram-positive bacteria resistance to vancomycin further escalate.