Excretion of ciprofloxacin in sweat and multiresistant Staphylococcus epidermidis

The microenvironment in antibiotic susceptibility testing

Antibiotic susceptibility testing (AST) by agar diffusion has been repeatedly standardized and, in most cases, gives results which predict clinical success when antibiotic treatment is based on such results. The formation of the inhibition zone is due to a transition from planktonic to biofilm mode of growth. The kinetics of the interaction of antibiotics with bacteria is similar during AST by agar diffusion and during administration of antibiotics to the patients. However, the Mueller-Hinton agar (MHA) recommended for AST agar diffusion test is fundamentally different from the composition of the interstitial fluid in the human body where the infections take place and human cells do not thrive in MH media. Use of RPMI 1640 medium designed for growth of eucaryotic cells for AST of Pseudomonas aeruginosa against azithromycin results in lower minimal inhibitory concentration, compared to results obtained by MHA. The reason is that the RPMI 1640 medium increases uptake and reduces efflux of azithromycin compared to MHA. During treatment of cystic fibrosis patients with azithromycin, mutational resistance occur which is not detected by AST with MHA. Whether this is the case with other antibiotics and bacteria is not known but it is of clinical importance to be studied.

Diverse Drug Classes Partition into Human Sweat: Implications for Both Sweat Fundamentals and for Therapeutic Drug Monitoring

ABSTRACT

Therapeutic drug monitoring to optimize drug therapy typically relies on the inconvenience of repeated plasma sampling. Sweat is a potential alternative biofluid convenient for sampling. However, limited information exists regarding the range of drugs excreted in sweat and their correlation with plasma concentrations. This study evaluated drugs in sweat and plasma of an ambulatory clinical cohort. Pilocarpine-induced sweat was collected from ambulatory participants at a single instance using an absorbent nylon mesh, followed by concurrent blood sampling for ratio and correlation analyses. In a model drug study, the pharmacokinetics of acetaminophen in sweat and plasma were compared. Of the 14 drugs and 2 metabolites monitored in the clinical study, all compounds were present in sweat and plasma; however, the sweat-to-plasma ratio varied substantially across the drugs. Opioids and methocarbamol demonstrated the highest concentrations in sweat, sometimes exceeding plasma concentrations. Selected antidepressants and muscle relaxants were also detected in sweat at a 2-10-fold dilution to the plasma. Others, such as gabapentin and pregabalin, were highly diluted (>30-fold) in sweat compared with plasma. Together, these data suggest that molecular attributes, specifically hydrophobicity (logP) and charge state at physiologic pH (7.4), enable reasonable prediction of sweat-to-plasma drug correlation. These findings demonstrated that sweat could be used as an alternative biofluid for therapeutic drug monitoring. The findings also suggest that although it has been broadly accepted that small hydrophobic molecules most likely have a strong plasma correlation, there is a small window of hydrophobicity and charge state that permits sweat partitioning.

Analysis of distribution and antibiotic resistance of Gram-positive bacteria isolated from a tertiary-care hospital in southern China: an 8-year retrospective study

Objective

Due to the severe drug resistance situation of Gram-negative bacteria, especially Gram-negative enterobacter, relatively little attention has been paid to the changes in Gram-positive bacteria species and drug resistance. Therefore, this study analyzed the prevalence and drug resistance of Gram-positive bacteria in a general tertiary-care hospital from 2014 to 2021, in order to discover the changes in Gram-positive bacteria distribution and drug resistance that cannot be easily identified, inform clinicians in their respective regions when selecting antimicrobial agents, and to provide the basis for the diagnosis of Gram-positive bacterial infection, and for the comprehensive and multi-pronged prevention and control of drug-resistant bacteria.

Methods

A retrospective study was conducted on Gram-positive bacteria isolated from patients presented to a general tertiary-care hospital from January 2014 to December 2021. A total of 15,217 Gram-positive strains were analyzed.

Results

During the 8-year period, the total number and the species of Gram-positive bacteria isolated from clinic increased continuously. The seven most common species were Streptococcus pneumoniae (21.2%), Staphylococcus aureus (15.9%), Enterococcus faecium (20.6%), Enterococcus faecalis (14.0%), and Staphylococcus epidermidis (7.8%), Staphylococcus haemolyticus (4.8%), Streptococcus agalactiae (3.6%). The isolation rates of Staphylococcus aureus and Streptococcus agalactiae increased, and the isolation rate of Enterococcus faecium decreased. The resistance rates of Staphylococcus aureus to erythromycin, clindamycin, tetracycline, rifampicin and furantoin decreased obviously. The resistance rates of Streptococcus pneumoniae to cefepime (non-meningitis) and ceftriaxone (meningitis) decreased significantly. The resistance rates of Enterococcus faecium to penicillin, ampicillin, erythromycin, levofloxacin, ciprofloxacin and furantoin rose rapidly from 50.3, 47.6, 71.5, 44.9, 52.3, and 37.5% in 2014 to 93.1, 91.6, 84.9, 86.8, 86.8, and 60.0% in 2021, respectively.

Conclusion

The total number and the species of Gram-positive bacteria isolated during the 8-year period increased continuously. Streptococcus pneumoniae and Staphylococcus aureus are the main causes of positive bacterial infections in this hospital. The resistance rates of Enterococcus faecium to a variety of commonly used antibiotics increased significantly. Therefore, it is very important to monitor the distribution of bacteria and their resistance to antibiotics to timely evaluate and identify changes in drug resistance that are not easily detected.

Markers of epidemiological success of methicillin-resistant Staphylococcus aureus isolates in European populations

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) infections impose a considerable burden on health systems, yet there is remarkable variation in the global incidence and epidemiology of MRSA. The MACOTRA consortium aimed to identify bacterial markers of epidemic success of MRSA isolates in Europe using a representative MRSA collection originating from France, the Netherlands and the United Kingdom.

METHODS

Operational definitions of success were defined in consortium meetings to compose a balanced strain collection of successful and sporadic MRSA isolates. Isolates were subjected to antimicrobial susceptibility testing and whole-genome sequencing; genes were identified and phylogenetic trees constructed. Markers of epidemiological success were identified using genome-based time-scaled haplotypic density analysis and linear regression. Antimicrobial usage data from ESAC-Net was compared with national MRSA incidence data.

RESULTS

Heterogeneity of MRSA isolate collections across countries hampered the use of a unified operational definition of success; therefore, country-specific approaches were used to establish the MACOTRA strain collection. Phenotypic antimicrobial resistance varied within related MRSA populations and across countries. In time-scaled haplotypic density analysis, fluoroquinolone, macrolide and mupirocin resistance were associated with MRSA success, whereas gentamicin, rifampicin and trimethoprim resistance were associated with sporadicity. Usage of antimicrobials across 29 European countries varied substantially, and β-lactam, fluoroquinolone, macrolide and aminoglycoside use correlated with MRSA incidence.

DISCUSSION

Our results are the strongest yet to associate MRSA antibiotic resistance profiles and antibiotic usage with the incidence of infection and successful clonal spread, which varied by country. Harmonized isolate collection, typing, resistance profiling and alignment with antimicrobial usage over time will aid comparisons and further support country-specific interventions to reduce MRSA burden.

A pilot study on the efficacy of topical lotion containing anti-acne postbiotic in subjects with mild -to -moderate acne

Introduction

Acne can compromise facial esthetics and become a mental burden, especially when it occurs in puberty. Skincare cosmetics with anti-acne efficiency is more convenient than other treatment modalities, such as dietary supplements, in certain circumstances. The purpose of this study was to investigate the efficacy of an anti-acne lotion in alleviating acne.

Methods

In our study, an anti-acne lotion containing ferment lysate produced by Lactiplantibacillus plantarum VHProbi^® E15 were applied to subjects with mild -to -moderate acne over 4 weeks. The efficacy was evaluated based on instrumental measurements using Visia^®-CR and CK-MPA^® system.

Results and discussion

The anti-acne lotion exhibited favorable safety, meeting the stringent criteria for the detection of microbes, heavy metals, toxicity, and irritation. After 2 weeks of treatment, a statistically significant improvement in acne lesions was observed compared to baseline (P < 0.01), and this continued to the end of the study. After 4 weeks of treatment, the transepidermal water loss (P < 0.05) and sebum production (P < 0.05) were significantly decreased in subjects compared to baseline. In addition, the pore/area of interest (AOI) and stratum corneum hydration displayed slightly positive changes throughout treatment. Thus, we conclude that applying topical anti-acne lotion may be safe and confer effective benefits in people with mild -to -moderate acne and represents a promising therapeutic option for acne.

Low Ciprofloxacin Concentrations Select Multidrug-Resistant Mutants Overproducing Efflux Pumps in Clinical Isolates of Pseudomonas aeruginosa

Low antibiotic concentrations present in natural environments are a severe and often neglected threat to public health. Even if they are present below their MICs, they may select for antibiotic-resistant pathogens. Notably, the minimal subinhibitory concentrations that select resistant bacteria, and define the respective sub-MIC selective windows, differ between antibiotics. The establishment of these selective concentrations is needed for risk-assessment studies regarding the presence of antibiotics in different habitats. Using short-term evolution experiments in a set of 12 Pseudomonas aeruginosa clinical isolates (including high-risk clones with ubiquitous distribution), we have determined that ciprofloxacin sub-MIC selective windows are strain specific and resistome dependent. Nonetheless, in all cases, clinically relevant multidrug-resistant (MDR) mutants emerged upon exposure to low ciprofloxacin concentrations, with these concentrations being below the levels reported in ciprofloxacin-polluted natural habitats where P. aeruginosa can be present. This feature expands the conditions and habitats where clinically relevant quinolone-resistant mutants can emerge. In addition, we established the lowest concentration threshold beyond which P. aeruginosa, regardless of the strain, becomes resistant to ciprofloxacin. Three days of exposure under this sub-MIC "risk concentration" led to the selection of MDR mutants that displayed resistance mechanisms usually ascribed to high selective pressures, i.e., the overproduction of the efflux pumps MexCD-OprJ and MexEF-OprN. From a One-Health viewpoint, these data stress the transcendent role of low drug concentrations, which can be encountered in natural ecosystems, in aggravating the antibiotic resistance problem, especially when it comes to pathogens of environmental origin. IMPORTANCE It has been established that antibiotic concentrations below MICs can select antibiotic-resistant pathogens, a feature of relevance for analyzing the role of nonclinical ecosystems in antibiotic resistance evolution. The range of concentrations where this selection occurs defines the sub-MIC selective window, whose width depends on the antibiotic. Herein, we have determined the ciprofloxacin sub-MIC selective windows of a set of Pseudomonas aeruginosa clinical isolates (including high-risk clones with worldwide distribution) and established the lowest concentration threshold, notably an amount reported to be present in natural ecosystems, beyond which this pathogen acquires resistance. Importantly, our results show that this ciprofloxacin sub-MIC selects for multidrug-resistant mutants overproducing clinically relevant efflux pumps. From a One-Health angle, this information supports that low antimicrobial concentrations, present in natural environments, may have a relevant role in worsening the antibiotic resistance crisis, particularly regarding pathogens with environmental niches, such as P. aeruginosa.

Next-Generation Digital Biomarkers for Tuberculosis and Antibiotic Stewardship: Perspective on Novel Molecular Digital Biomarkers in Sweat, Saliva, and Exhaled Breath

The internet of health care things enables a remote connection between health care professionals and patients wearing smart biosensors. Wearable smart devices are potentially affordable, sensitive, specific, user-friendly, rapid, robust, lab-independent, and deliverable to the end user for point-of-care testing. The datasets derived from these devices are known as digital biomarkers. They represent a novel patient-centered approach to collecting longitudinal, context-derived health insights. Adding automated, analytical smartphone applications will enable their use in high-, middle-, and low-income countries. So far, digital biomarkers have been focused primarily on accelerometer data and heart rate due to well-established sensors originating from the consumer market. Novel emerging smart biosensors will detect biomarkers (or compounds) independent of a lab and noninvasively in sweat, saliva, and exhaled breath. These molecular digital biomarkers are a promising novel approach to reduce the burden from 2 major infectious diseases with urgent unmet needs: tuberculosis and infections with multidrug resistant pathogens. Active tuberculosis (aTbc) is one of the deadliest diseases from an infectious agent. However, a simple and reliable test for its detection is still missing. Furthermore, inappropriate antimicrobial use leads to the development of antimicrobial resistance, which is associated with high mortality and health care costs. From this perspective, we discuss the innovative approach of a noninvasive and lab-independent collection of novel biomarkers to detect aTbc, which at the same time may additionally serve as a scalable therapeutic drug monitoring approach for antibiotics. These molecular digital biomarkers are next-generation digital biomarkers and have the potential to shape the future of infectious diseases.

Non-invasive Drug Monitoring of β-Lactam Antibiotics Using Sweat Analysis-A Pilot Study

Background: Antimicrobial resistance is a major challenge in treating infectious diseases. Therapeutic drug monitoring (TDM) can optimize and personalize antibiotic treatment. Previously, antibiotic concentrations in tissues were extrapolated from skin blister studies, but sweat analyses for TDM have not been conducted. Objective: To investigate the potential of sweat analysis as a non-invasive, rapid, and potential bedside TDM method. Methods: We analyzed sweat and blood samples from 13 in-house patients treated with intravenous cefepime, imipenem, or flucloxacillin. For cefepime treatment, full pharmacokinetic sampling was performed (five subsequent sweat samples every 2 h) using ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry. The ClinicalTrials.gov registration number is NCT03678142. Results: In this study, we demonstrated for the first time that flucloxacillin, imipenem, and cefepime are detectable in sweat. Antibiotic concentration changes over time demonstrated comparable (age-adjusted) dynamics in the blood and sweat of patients treated with cefepime. Patients treated with standard flucloxacillin dosage showed the highest mean antibiotic concentration in sweat. Conclusions: Our results provide a proof-of-concept that sweat analysis could potentially serve as a non-invasive, rapid, and reliable method to measure antibiotic concentration and as a surrogate marker for tissue penetration. If combined with smart biosensors, sweat analysis may potentially serve as the first lab-independent, non-invasive antibiotic TDM method.

Sweat as a Source of Next-Generation Digital Biomarkers

Sweat has been associated with health and disease ever since it was linked to high body temperature and exercise. It contains a broad range of electrolytes, proteins, and lipids, and therefore hosts a broad panel of potential noninvasive biomarkers. The development of novel smartphone-based biosensors will enable a more sophisticated, patient-driven sweat analysis. This will provide a broad range of novel digital biomarkers. Digital biomarkers are of increasing interest because they deliver various relevant longitudinal health data. To date, investigations on digital biomarkers have focused on creating objective measurements of function. Sweat analysis using smartphone-based biosensors has the potential to provide initial noninvasive metabolic feedback and therefore represents a promising complement and a source for next-generation digital biomarkers. From this viewpoint, we discuss state-of-the-art sweat research, focusing on the clinical implementation of sweat in medicine. Sweat provides biomarkers that represent direct metabolic feedback and is therefore expected to be the next generation of digital biomarkers. With regard to its broad application in various fields of medicine, we see a clear need to evolve the internet-enabled field of sweat expertise: iSudorology.

Microbiome as a tool and a target in the effort to address antimicrobial resistance

Reciprocal, intimate relationships between the human microbiome and the host immune system are shaped by past microbial encounters and prepare the host for future ones. Antibiotics and other antimicrobials leave their mark on both the microbiome and host immunity. Antimicrobials alter the structure of the microbiota, expand the host-specific pool of antimicrobial-resistance genes and organisms, degrade the protective effects of the microbiota against invasion by pathogens, and may impair vaccine efficacy. Through these effects on the microbiome they may affect immune responses. Vaccines that exert protective or therapeutic effects against pathogens may reduce the use of antimicrobials, the development and spread of antimicrobial resistance, and the harmful impacts of these drugs on the microbiome. Other strategies involving manipulation of the microbiome to deplete antibiotic-resistant organisms or to enhance immune responses to vaccines may prove valuable in addressing antimicrobial resistance as well. This article describes the intersections of immunity, microbiome and antimicrobial exposure, and the use of vaccines and other alternative strategies for the control and management of antimicrobial resistance.

Estimating the proportion of bystander selection for antibiotic resistance among potentially pathogenic bacterial flora

Bystander selection-the selective pressure for resistance exerted by antibiotics on microbes that are not the target pathogen of treatment-is critical to understanding the total impact of broad-spectrum antibiotic use on pathogenic bacterial species that are often carried asymptomatically. However, to our knowledge, this effect has never been quantified. We quantify bystander selection for resistance for a range of clinically relevant antibiotic-species pairs as the proportion of all antibiotic exposures received by a species for conditions in which that species was not the causative pathogen ("proportion of bystander exposures"). Data sources include the 2010-2011 National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey, the Human Microbiome Project, and additional carriage and etiological data from existing literature. For outpatient prescribing in the United States, we find that this proportion over all included antibiotic classes is over 80% for eight of nine organisms of interest. Low proportions of bystander exposure are often associated with infrequent bacterial carriage or concentrated prescribing of a particular antibiotic for conditions caused by the species of interest. Applying our results, we roughly estimate that pneumococcal conjugate vaccination programs result in nearly the same proportional reduction in total antibiotic exposures of Streptococcus pneumoniae, Staphylococcus aureus, and Escherichia coli, despite the latter two organisms not being targeted by the vaccine. These results underscore the importance of considering antibiotic exposures of bystanders, in addition to the target pathogen, in measuring the impact of antibiotic resistance interventions.

Resistance profile of clinically relevant bacterial isolates against fluoroquinolone in Ethiopia: a systematic review and meta-analysis

Background

Fluoroquinolones are among the most frequently utilized antibacterial agents in developing countries like Ethiopia. Ciprofloxacin has become the most prescribed drug within this class and remains as one of the top three antibacterial agents prescribed in Ethiopia. However, several studies indicated that there is a gradual increase of antibacterial resistance. Therefore, this meta-analysis aimed to quantitatively estimate the prevalence of ciprofloxacin resistance bacterial isolates in Ethiopia.

Methods

Literature search was conducted from electronic databases and indexing services including EMBASE (Ovid interface), PubMed/MEDLINE, Google Scholar, Science Direct and WorldCat. Data were extracted with structured format prepared in Microsoft Excel and exported to STATA 15.0 software for the analyses. Pooled estimation of outcomes was performed with DerSimonian-Laird random-effects model at 95% confidence level. Degree of heterogeneity of studies was presented with I² statistics. Publication bias was conducted with comprehensive meta-analysis version 3 software and presented with funnel plots of standard error supplemented by Begg’s and Egger’s tests. The study protocol has been registered on PROSPERO with reference number ID: CRD42018097047.

Results

A total of 37 studies were included for this study. The pooled prevalence of resistance in selected gram-positive bacterial isolates against ciprofloxacin was found to be 19.0% (95% confidence interval [CI]: 15.0, 23.0). The degree of resistance among Staphylococcus aureus, Coagulase negative Staphyloccoci (CoNS), Enterococcus faecalis and Group B Streptococci (GBS) was found to be 18.6, 21.6, 23.9, and 7.40%, respectively. The pooled prevalence of resistance in gram-negative bacteria was about 21.0% (95% CI: 17, 25). Higher estimates were observed in Neisseria gonorrhea (48.1%), Escherichia coli (24.3%) and Klebsiella pneumonia (23.2%). Subgroup analysis indicated that blood and urine were found to be a major source of resistant S. aureus isolates. Urine was also a major source of resistant strains for CoNS, Klebsiella and Proteus species.

Conclusion

Among gram-positive bacteria, high prevalence of resistance was observed in E. faecalis and CoNS whereas relatively low estimate of resistance was observed among GBS isolates. Within gram-negative bacteria, nearly half of isolates in N. gonorrhoea were found ciprofloxacin resistant. From enterobacteriaceae isolates, K. pneumonia and E. coli showed higher estimates of ciprofloxacin resistance.

Electronic supplementary material

The online version of this article (10.1186/s40360-018-0274-6) contains supplementary material, which is available to authorized users.

Antimicrobial Stewardship and Antimicrobial Resistance

Antimicrobial stewardship programs aim to reduce costs, optimize therapeutic outcomes, and reduce antimicrobial resistance. Reductions of antimicrobial resistance are the most elusive because emergence and spread of resistant bacteria involves antimicrobial selective pressure and lapses in infection control techniques. The relationship between antimicrobial usage and resistance is not always direct. The understanding of which techniques are most effective is limited because many studies are descriptive or quasiexperimental. Recent meta-analyses or systematic reviews of stewardship programs offer encouragement that some interventions reduce overall antimicrobial selective pressure and, where associated with infection control interventions, impact resistance rates in individual institutions.

Evolution of Antibiotic Resistance in Biofilm and Planktonic Pseudomonas aeruginosa Populations Exposed to Subinhibitory Levels of Ciprofloxacin

The opportunistic Gram-negative pathogen Pseudomonas aeruginosa, known for its intrinsic and acquired antibiotic resistance, has a notorious ability to form biofilms, which often facilitate chronic infections. The evolutionary paths to antibiotic resistance have mainly been investigated in planktonic cultures and are less studied in biofilms. We experimentally evolved P. aeruginosa PAO1 colony biofilms and stationary-phase planktonic cultures for seven passages in the presence of subinhibitory levels (0.1 mg/liter) of ciprofloxacin (CIP) and performed a genotypic (whole-bacterial population sequencing) and phenotypic assessment of the populations. We observed a higher proportion of CIP resistance in the CIP-evolved biofilm populations than in planktonic populations exposed to the same drug concentrations. However, the MICs of ciprofloxacin were lower in CIP-resistant isolates selected from the biofilm population than the MICs of CIP-resistant isolates from the planktonic cultures. We found common evolutionary trajectories between the different lineages, with mutations in known CIP resistance determinants as well as growth condition-dependent adaptations. We observed a general trend toward a reduction in type IV-pilus-dependent motility (twitching) in CIP-evolved populations and a loss of virulence-associated traits in the populations evolved in the absence of antibiotic. In conclusion, our data indicate that biofilms facilitate the development of low-level mutational resistance, probably due to the lower effective drug exposure than in planktonic cultures. These results provide a framework for the selection process of resistant variants and the evolutionary mechanisms involved under the two different growth conditions.

Risk of meticillin resistant Staphylococcus aureus and Clostridium difficile in patients with a documented penicillin allergy: population based matched cohort study

OBJECTIVE

To evaluate the relation between penicillin allergy and development of meticillin resistant Staphylococcus aureus (MRSA) and C difficile.

DESIGN

Population based matched cohort study.

SETTING

United Kingdom general practice (1995-2015).

PARTICIPANTS

301 399 adults without previous MRSA or C difficile enrolled in the Health Improvement Network database: 64 141 had a penicillin allergy and 237 258 comparators matched on age, sex, and study entry time.

MAIN OUTCOME MEASURES

The primary outcome was risk of incident MRSA and C difficile. Secondary outcomes were use of β lactam antibiotics and β lactam alternative antibiotics.

RESULTS

Among 64 141 adults with penicillin allergy and 237 258 matched comparators, 1365 developed MRSA (442 participants with penicillin allergy and 923 comparators) and 1688 developed C difficile (442 participants with penicillin allergy and 1246 comparators) during a mean 6.0 years of follow-up. Among patients with penicillin allergy the adjusted hazard ratio for MRSA was 1.69 (95% confidence interval 1.51 to 1.90) and for C difficile was 1.26 (1.12 to 1.40). The adjusted incidence rate ratios for antibiotic use among patients with penicillin allergy were 4.15 (95% confidence interval 4.12 to 4.17) for macrolides, 3.89 (3.66 to 4.12) for clindamycin, and 2.10 (2.08 to 2.13) for fluoroquinolones. Increased use of β lactam alternative antibiotics accounted for 55% of the increased risk of MRSA and 35% of the increased risk of C difficile.

CONCLUSIONS

Documented penicillin allergy was associated with an increased risk of MRSA and C difficile that was mediated by the increased use of β lactam alternative antibiotics. Systematically addressing penicillin allergies may be an important public health strategy to reduce the incidence of MRSA and C difficile among patients with a penicillin allergy label.

Invasive Methicillin-Resistant Staphylococcus aureus USA500 Strains from the U.S. Emerging Infections Program Constitute Three Geographically Distinct Lineages

USA500 isolates are clonal complex 8 (CC8) Staphylococcus aureus strains closely related to the prominent community- and hospital-associated USA300 group. Despite being relatively understudied, USA500 strains cause a significant burden of disease and are the third most common methicillin-resistant S. aureus (MRSA) strains identified in the U.S. Emerging Infections Program (EIP) invasive S. aureus surveillance. To better understand the genetic relationships of the strains, we sequenced the genomes of 539 USA500 MRSA isolates from sterile site infections collected through the EIP between 2005 and 2013 in the United States. USA500 isolates fell into three major clades principally separated by their distribution across different U.S. regions. Clade C1 strains, found principally in the Northeast, were associated with multiple IS256 insertion elements in their genomes and higher levels of antibiotic resistance. C2 was associated with Southern states, and E1 was associated with Western states. C1 and C2 strains all shared a frameshift in the gene encoding AdsA surface-attached surface protein. We propose that the term "USA500" should be used for CC8 strains sharing a recent common ancestor with the C1, C2, and E1 strains but not in the USA300 group.IMPORTANCE In this work, we have removed some of the confusion surrounding the use of the name "USA500," placed USA500 strains in the context of the CC8 group, and developed a strategy for assignment to subclades based on genome sequence. Our new phylogeny of USA300/USA500 will be a reference point for understanding the genetic adaptations that have allowed multiple highly virulent clonal strains to emerge from within CC8 over the past 50 years.

Antibiotic treatment of biofilm infections

Bacterial biofilms are associated with a wide range of infections, from those related to exogenous devices, such as catheters or prosthetic joints, to chronic tissue infections such as those occurring in the lungs of cystic fibrosis patients. Biofilms are recalcitrant to antibiotic treatment due to multiple tolerance mechanisms (phenotypic resistance). This causes persistence of biofilm infections in spite of antibiotic exposure which predisposes to antibiotic resistance development (genetic resistance). Understanding the interplay between phenotypic and genetic resistance mechanisms acting on biofilms, as well as appreciating the diversity of environmental conditions of biofilm infections which influence the effect of antibiotics are required in order to optimize the antibiotic treatment of biofilm infections. Here, we review the current knowledge on phenotypic and genetic resistance in biofilms and describe the potential strategies for the antibiotic treatment of biofilm infections. Of note is the optimization of PK/PD parameters in biofilms, high-dose topical treatments, combined and sequential/alternate therapies or the use antibiotic adjuvants.

Individual pharmacokinetic variation leads to underdosing of ciprofloxacin in some cystic fibrosis patients

Ciprofloxacin (CIP) is frequently used when treating cystic fibrose (CF) patients with intermittent Pseudomonas aeruginosa (P. aeruginosa) lung colonization. However, approximately 20% of the patients progress to chronic infection despite early intervention. The aim of this study, was to investigate the pharmacokinetics of CIP, to evaluate if CYP3A4-related metabolism is involved and to find the optimal dose needed to eradicate intermittently colonizing bacteria in the lungs of CF patients. Methods An open-label, prospective pharmacokinetic study was performed. Twenty-two adult CF-patients were each given 500 mg CIP orally. One blood sample was taken at t = 0, and the following 12 hr, nine blood samples were collected. The optimal dose and interval was then calculated by Monte Carlo simulation. CYP3A4-activity was mesured using the Erythromycin Breath Test (ERMBT). Results A 14-fold variation in AUC for the 500 mg CIP (median 473.5 µg/ml × min), and a 30-fold variation in Cmax for CIP (median 2 µg/ml) was found. For CYP3A4-activity the variation was 8-fold. No correlation was found between the CYP3A4-activity and CIP-concentrations. The probability of eradicating intermittent P. aeruginosa colonization in the lungs of CF patients was found to be 57% (3 doses/day), when 500 mg CIP was given. It was calculated to be 89% (2 doses/day) and 94% (3 doses/day), respectivly if 750 mg CIP had been given. Conclusion A large pharmacokinetic difference of CIP in CF patiens was found, not explained by CYP3A4 variation. CIP should be given at 750 mg two or three times daily to adult CF patients with intermittently colonization. Pediatr Pulmonol. 2017;52:319-323. © 2016 Wiley Periodicals, Inc.

Antimicrobial resistance development following surgical site infections

Surgical site infections (SSIs) determine an increase in hospitalization time and antibiotic therapy costs. The aim of this study was to identify the germs involved in SSIs in patients from the Clinical Emergency County Hospital of Craiova (SCJUC) and to assess their resistance to antimicrobials, with comparisons between surgical wards and the intensive care unit (ICU). The biological samples were subjected to classical bacteriological diagnostics. Antibiotic resistance was tested by disc diffusion. We used hierarchical clustering as a method to group the isolates based upon the antibiotic resistance profile. The most prevalent bacterial species isolated were Staphylococcus aureus (S. aureus; 50.72%), followed by Escherichia coli (E. coli; 17.22%) and Pseudomonas aeruginosa; 10.05%). In addition, at lower percentages, we isolated glucose-non-fermenting, Gram-negative bacteria and other Enterobacteriaceae. The antibiotic resistance varied greatly between species; the most resistant were the non-fermenting Gram-negative rods. E. coli exhibited lower resistance to third generation cephalosporins, quinolones and carbapenems. By contrast, Klebsiella was resistant to many cephalosporins and penicillins, and to a certain extent to carbapenems due to carbapenemase production. The non-fermenting bacteria were highly resistant to antibiotics, but were generally sensitive to colistin. S. aureus was resistant to ceftriaxone (100%), penicillin (91.36%), amoxicillin/clavulanate (87.50%), amikacin (80.00%) and was sensitive to levofloxacin, doxycycline, gentamycin, tigecycline and teicoplanin. The Enterobacteriaceae resistance was only slightly higher in the ICU, particularly to carbapenems (imipenem, 31.20% in the ICU vs. 14.30% in the surgical wards; risk ratio = 2.182). As regards Staphylococcus species, but for non-fermenting bacteria, even if the median was almost the same, the antibiotic resistance index values were confined to the upper limit in the ICU. The data gathered from this study may help infection control teams to establish effective guidelines for antibiotic therapies in various surgical procedures, in order to minimize the risk of developing SSIs by the efficient application of the anti-infection armamentarium.

Investigation of the Antibacterial Effect of Mesoporous Magnesium Carbonate

Mesoporous magnesium carbonate (MMC) was first presented in 2013, and this material is currently under consideration for use in a number of biotechnological applications including topical formulations. This study presents the first evaluation of the antibacterial properties of the material with mesoporous silica and two other magnesium-containing powder materials used as references. All powder materials in this study are sieved to achieve a particle size distribution between 25 and 75 μm. The Gram-positive bacterium Staphylococcus epidermidis is used as the model bacterium due to its prevalence on human skin, its likelihood of developing resistance to antibiotics, for example, from routine exposure to antibiotics secreted in sweat, and because it is found inside affected acne vulgaris pores. Quantification of bacterial viability using a metabolic activity assay with resazurin as the fluorescent indicator shows that MMC exerts a strong antibacterial effect on the bacteria and that alkalinity accounts for the major part of this effect. The results open up for further development of MMC in on-skin applications where bacterial growth inhibition without using antibiotics is deemed favorable.

Antimicrobial susceptibility and body site distribution of community isolates of coagulase-negative staphylococci

The primary aim of this study was to determine antimicrobial resistance in coagulase-negative staphylococci (CoNS) from healthy adults in the community. Healthy adults (n = 114) were swabbed on six body sites; both armpits, both knee pits and both sides of the groin. Species determination was performed using Matrix Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF) and susceptibility testing for 11 relevant antimicrobials was performed by the disc diffusion method and minimal inhibitory concentration gradient test. In total, 693 CoNS isolates were identified. Susceptibility testing was done on 386 isolates; one CoNS from each species found on each participant from the different body sites. The prevalence of antimicrobial resistance in the CoNS isolates were; erythromycin (24.6%), fusidic acid (19.9%), tetracycline (11.4%), clindamycin (7.8%), gentamicin (6.2%) and cefoxitin (4.1%). Multidrug resistance was observed in 5.2% of the isolates. Staphylococcus epidermidis and S. hominis were the first and second most prevalent species on all three body sites. We conclude that CoNS isolates from healthy adults in the community have a much lower prevalence of antimicrobial resistance than reported in nosocomial CoNS isolates. Still, we believe that levels of resistance in community CoNS should be monitored as the consumption of antimicrobials in primary care in Norway is increasing.

Resistance in Staphylococcus Aureus: The Never-Ending Story

Combating Staphylococcus aureus (S. aureus) infections using antibacterial drugs is actually an ongoing effort to overcome resistance mechanism of this microorganism. In this paper, we discussed (1) the mechanisms of resistance to some of the most commonly used antimicrobial agents in the treatment of S. aureus: methicillin, vancomicyn and quinolones. In addition, (2) efflux pump mechanisms involved in maintaining homeostasis in the presence of compounds that inhibit S. aureus growth and reproduction, as well as mechanisms of resistance to a number of antibiotics, have been reviewed.

The phenotypic evolution of Pseudomonas aeruginosa populations changes in the presence of subinhibitory concentrations of ciprofloxacin

Ciprofloxacin is a widely used antibiotic, in the class of quinolones, for treatment of Pseudomonas aeruginosa infections. The immediate response of P. aeruginosa to subinhibitory concentrations of ciprofloxacin has been investigated previously. However, the long-term phenotypic adaptation, which identifies the fitted phenotypes that have been selected during evolution with subinhibitory concentrations of ciprofloxacin, has not been studied. We chose an experimental evolution approach to investigate how exposure to subinhibitory concentrations of ciprofloxacin changes the evolution of P. aeruginosa populations compared to unexposed populations. Three replicate populations of P. aeruginosa PAO1 and its hypermutable mutant ΔmutS were cultured aerobically for approximately 940 generations by daily passages in LB medium with and without subinhibitory concentration of ciprofloxacin and aliquots of the bacterial populations were regularly sampled and kept at  - 80 °C for further investigations. We investigate here phenotypic changes between the ancestor (50 colonies) and evolved populations (120 colonies/strain). Decreased protease activity and swimming motility, higher levels of quorum-sensing signal molecules and occurrence of mutator subpopulations were observed in the ciprofloxacin-exposed populations compared to the ancestor and control populations. Transcriptomic analysis showed downregulation of the type III secretion system in evolved populations compared to the ancestor population and upregulation of denitrification genes in ciprofloxacin-evolved populations. In conclusion, the presence of antibiotics at subinhibitory concentration in the environment affects bacterial evolution and further studies are needed to obtain insight into the dynamics of the phenotypes and the mechanisms involved.

Surveillance of antibiotic resistance

Surveillance involves the collection and analysis of data for the detection and monitoring of threats to public health. Surveillance should also inform as to the epidemiology of the threat and its burden in the population. A further key component of surveillance is the timely feedback of data to stakeholders with a view to generating action aimed at reducing or preventing the public health threat being monitored. Surveillance of antibiotic resistance involves the collection of antibiotic susceptibility test results undertaken by microbiology laboratories on bacteria isolated from clinical samples sent for investigation. Correlation of these data with demographic and clinical data for the patient populations from whom the pathogens were isolated gives insight into the underlying epidemiology and facilitates the formulation of rational interventions aimed at reducing the burden of resistance. This article describes a range of surveillance activities that have been undertaken in the UK over a number of years, together with current interventions being implemented. These activities are not only of national importance but form part of the international response to the global threat posed by antibiotic resistance.

Comparative dynamics of the emergence of fluoroquinolone resistance in staphylococci from the nasal microbiota of patients treated with fluoroquinolones according to their environment

Fluoroquinolone-resistant staphylococci (FQRS) are primarily selected in the nasal microbiota during fluoroquinolone (FQ) treatment. To gain insight into the dynamics of the emergence of FQRS, 49 hospitalised patients (HPs) and 62 community patients (CPs) treated with FQs were studied. Nasal swabs were collected before (T0), at the end of (T1) and 1 month after (T2) FQ treatment. FQRS were identified by mass spectrometry. Antibiotic resistance was determined. Pre- and post-exposure staphylococci populations were compared phenotypically and by MLST to determine the origin of FQRS. At T0, 33/49 HPs (67%) and 24/62 CPs (39%) carried FQRS (OR=3.3, 95% CI: 1.4-7.9; P<0.001). Among patients with no FQRS at T0, 15/16 HPs (94%) and 16/38 CPs (42%) had FQRS detected at T1 and/or T2 (OR=19.6, 95% CI: 2.5-902; P<0.001). Among FQRS having emerged, co-resistance to meticillin was detected in 87% and 82% of HPs and CPs, respectively. No selection of resistance emerging from the initial microbiota was evidenced. FQRS showed decreased species diversity in favour of Staphylococcus haemolyticus and Staphylococcus epidermidis. As a consequence of FQ treatment, acquisition of FQRS in the nasal microbiota is frequent in the community and almost inevitable in hospitals. Acquisition from extranasal sites prevails. A restriction in species diversity in favour of more pathogenic and resistant species occurs. This highlights the major impact of FQ treatment on nasal microbiota, the role of the ecological environment in the emergence of FQRS, and the high-risk of dissemination of resistant staphylococci.

Impact of fluoroquinolones on human microbiota. Focus on the emergence of antibiotic resistance

The aggregate of microorganisms residing on the surface of the skin, in the oropharynx and in the GI tract, known as the human microbiota, play a major role as natural reservoirs for bacterial resistance to antibiotics. Fluoroquinolones (FQ) are among the most prescribed antibiotics and a major increase in FQ resistance is occurring worldwide. High concentrations of FQ are found in microbial ecosystems explaining their profound effect on the clinically relevant bacteria that compose them. Yet, because of different local pharmacokinetics, distinct selective pressures occur in the different microbiota. Here we review the qualitative and quantitative impact of FQ on the three main human microbiota and their consequences, particularly in terms of emergence of antibiotic resistance. Finally, we review potential actions that could decrease the impact of FQs on microbiota.

Antibiotic exposure in a low-income country: screening urine samples for presence of antibiotics and antibiotic resistance in coagulase negative staphylococcal contaminants

Development of antimicrobial resistance has been assigned to excess and misuse of antimicrobial agents. Staphylococci are part of the normal flora but are also potential pathogens that have become essentially resistant to many known antibiotics. Resistances in coagulase negative staphylococci (CoNS) are suggested to evolve due to positive selective pressure following antibiotic treatment. This study investigated the presence of the nine most commonly used antimicrobial agents in human urine from outpatients in two hospitals in Ghana in relation to CoNS resistance. Urine and CoNS were sampled (n = 246 and n = 96 respectively) from patients in two hospitals in Ghana. CoNS were identified using Gram staining, coagulase test, and MALDI-TOF/MS, and the antimicrobial susceptibility to 12 commonly used antimicrobials was determined by disk diffusion. Moreover an analytical method was developed for the determination of the nine most commonly used antimicrobial agents in Ghana by using solid-phase extraction in combination with HPLC-MS/MS using electron spray ionization. The highest frequency of resistance to CoNS was observed for penicillin V (98%), trimethoprim (67%), and tetracycline (63%). S. haemolyticus was the most common isolate (75%), followed by S. epidermidis (13%) and S. hominis (6%). S. haemolyticus was also the species displaying the highest resistance prevalence (82%). 69% of the isolated CoNS were multiple drug resistant (≧4 antibiotics) and 45% of the CoNS were methicillin resistant. Antimicrobial agents were detected in 64% of the analysed urine samples (n = 121) where the most frequently detected antimicrobials were ciprofloxacin (30%), trimethoprim (27%), and metronidazole (17%). The major findings of this study was that the prevalence of detected antimicrobials in urine was more frequent than the use reported by the patients and the prevalence of resistant S. haemolyticus was more frequent than other resistant CoNS species when antimicrobial agents were detected in the urine.

Clinical characteristics of Staphylococcus epidermidis: a systematic review

Staphylococci are known as clustering Gram-positive cocci, nonmotile, non-spore forming facultatively anaerobic that classified in two main groups, coagulase-positive and coagulase-negative. Staphylococcus epidermidis with the highest percentage has the prominent role among coagulase-negative Staphylococci that is the most important reason of clinical infections. Due to various virulence factors and unique features, this microorganism is respected as a common cause of nosocomial infections. Because of potential ability in biofilm formation and colonization in different surfaces, also using of medical implant devices in immunocompromised and hospitalized patients the related infections have been increased. In recent decades the clinical importance and the emergence of methicillin-resistant Staphylococcus epidermidis strains have created many challenges in the treatment process.

A case of Capnocytophaga canimorsus sacral abscess in an immunocompetent patient

We report a unique case of sacral Capnocytophaga canimorsus abscess successfully treated with surgery and antibiotics. Close contact to a dog was assumed to be the most likely source of infection. Established risk factors for invasive C. canimorsus infection such as splenectomy, alcoholism or overt immunosuppression could not be identified. The role of cigarette smoking, portal of entry and the possible relevance of altered skin microbiota as well as the diagnostic value of polymerase chain reaction are discussed in the light of the scarce literature of spinal C. canimorsus infections.

[Resistance to fluoroquinolones in 2013: what are the consequences in internal medicine?]

Because of their important qualities, fluoroquinolones are amongst the most prescribed antibiotics in the world. The corollary of this success is the rapid increase in resistance to fluoroquinolones, responsible for treatment failures. Moreover, fluoroquinolone-resistance is often accompanied by resistance to other classes of antibiotics. Currently, significant levels of resistance are found both in hospitals and in community settings, severely limiting possibilities for empirical use of fluoroquinolones. A major mechanism explaining the rapid emergence of resistance to fluoroquinolones is their specific impact on human microbiota and the selection of resistant strains in the microbiota, which seems to be an unavoidable ecological side effect. In order to preserve the efficiency of this important class of antibiotics, limiting their use and respecting good practice recommendations are essential.

Sublethal ciprofloxacin treatment leads to rapid development of high-level ciprofloxacin resistance during long-term experimental evolution of Pseudomonas aeruginosa

The dynamics of occurrence and the genetic basis of ciprofloxacin resistance were studied in a long-term evolution experiment (940 generations) in wild-type, reference strain (PAO1) and hypermutable (PAOΔmutS and PAOMY-Mgm) P. aeruginosa populations continuously exposed to sub-MICs (1/4) of ciprofloxacin. A rapid occurrence of ciprofloxacin-resistant mutants (MIC of ≥12 μg/ml, representing 100 times the MIC of the original population) were observed in all ciprofloxacin-exposed lineages of PAOΔmutS and PAOMY-Mgm populations after 100 and 170 generations, respectively, and in one of the PAO1 lineages after 240 generations. The genetic basis of resistance was mutations in gyrA (C248T and G259T) and gyrB (C1397A). Cross-resistance to beta-lactam antibiotics was observed in the bacterial populations that evolved during exposure to sublethal concentrations of ciprofloxacin. Our study shows that mutants with high-level ciprofloxacin resistance are selected in P. aeruginosa bacterial populations exposed to sub-MICs of ciprofloxacin. This can have implications for the long-term persistence of resistant bacteria and spread of antibiotic resistance by exposure of commensal bacterial flora to low antibiotic concentrations.

Impact of an enhanced antibiotic stewardship on reducing methicillin-resistant Staphylococcus aureus in primary and secondary healthcare settings

The objective of this study was to evaluate the impact of restricting high-risk antibiotics on methicillin-resistant Staphylococcus aureus (MRSA) incidence rates in a hospital setting. A secondary objective was to assess the impact of reducing fluoroquinolone use in the primary-care setting on MRSA incidence in the community. This was an interventional, retrospective, ecological investigation in both hospital and community (January 2006 to June 2010). Segmented regression analysis of interrupted time-series was employed to evaluate the intervention. The restriction of high-risk antibiotics was associated with a significant change in hospital MRSA incidence trend (coefficient=-0·00561, P=0·0057). Analysis showed that the intervention relating to reducing fluoroquinolone use in the community was associated with a significant trend change in MRSA incidence in community (coefficient=-0·00004, P=0·0299). The reduction in high-risk antibiotic use and fluoroquinolone use contributed to both a reduction in incidence rates of MRSA in hospital and community (primary-care) settings.

Length of exposure to the hospital environment is more important than antibiotic exposure in healthcare associated infections by methicillin-resistant Staphylococcus aureus: a comparative study

OBJECTIVES

Both total antimicrobial use and specific antimicrobials have been implicated as risk factors for healthcare-associated methicillin-resistant Staphylococcus aureus (HCA-MRSA) infection. The aims of this study were: (I) to explore predictors of a new HCA-MRSA infection in comparison with a new healthcare-associated methicillin-sensitive Staphylococcus aureus (HCA-MSSA); (II) to thoroughly assess the role of recent antibiotic use qualitatively and quantitatively.

METHODS

The time-period for our study was from October 1997 through September 2001. Through applying strict criteria, we identified two groups of inpatients, one with a new HCA-MRSA infection and one with a new HCA-MSSA infection. We recorded demographic, clinical and antibiotic use-related data up to 30 days before the positive culture date.

RESULTS

We identified 127 and 70 patients for each group, respectively. Two logistic regression models were carried out to assess the role of antimicrobial use (qualitatively and quantitatively). In model I, duration of hospital stay, presence of chronic wounds, aminoglycoside and fluoroquinolone use retained statistical significance. In model II, duration of hospital stay and history of intubation during the last month stood out as the only significant predictors of a subsequent HCA-MRSA infection. No significant differences in outcome were noted.

CONCLUSIONS

The length of exposure to the hospital environment may be the best predictor of a new HCA-MRSA infection. Use of aminoglycosides and fluoroquinolones may also stand independently along with presence of chronic ulcers and surgical procedures. No independent association between quantitative antibiotic use and subsequent HCA-MRSA infection was documented.

Acne vulgaris

Acne is a chronic inflammatory disease of the pilosebaceous unit resulting from androgen-induced increased sebum production, altered keratinisation, inflammation, and bacterial colonisation of hair follicles on the face, neck, chest, and back by Propionibacterium acnes. Although early colonisation with P acnes and family history might have important roles in the disease, exactly what triggers acne and how treatment affects the course of the disease remain unclear. Other factors such as diet have been implicated, but not proven. Facial scarring due to acne affects up to 20% of teenagers. Acne can persist into adulthood, with detrimental effects on self-esteem. There is no ideal treatment for acne, although a suitable regimen for reducing lesions can be found for most patients. Good quality evidence on comparative effectiveness of common topical and systemic acne therapies is scarce. Topical therapies including benzoyl peroxide, retinoids, and antibiotics when used in combination usually improve control of mild to moderate acne. Treatment with combined oral contraceptives can help women with acne. Patients with more severe inflammatory acne usually need oral antibiotics combined with topical benzoyl peroxide to decrease antibiotic-resistant organisms. Oral isotretinoin is the most effective therapy and is used early in severe disease, although its use is limited by teratogenicity and other side-effects. Availability, adverse effects, and cost, limit the use of photodynamic therapy. New research is needed into the therapeutic comparative effectiveness and safety of the many products available, and to better understand the natural history, subtypes, and triggers of acne.

Photodynamic inactivation of multi-resistant bacteria (PIB) - a new approach to treat superficial infections in the 21st century

The increasing resistance of bacteria against antibiotics is one of the most important clinical challenges of the 21(st) century. Within the gram-positive bacteria the methicillin-resistant Staphylococcus aureus and Enterococcus faecium represent the major obstacle to successful therapy. Apart from the development of new antibiotics it requires additional differently constituted approaches, like photodynamic inactivation in order to have further effective treatment options against bacteria available. Certain dyes, termed photosensitizers, are able to store the absorbed energy in long-lived electronic states upon light activation with appropriate wavelengths and thus make these states available for chemical activation of the immediate surroundings. The interaction with molecular oxygen, which leads to different, very reactive and thus cytotoxic oxygen species, is highlighted. In this review the application of the photodynamic inactivation of bacteria will be discussed regarding the possible indications in dermatology, like localized skin and wound infections or the reduction of nosocomial colonization with multi-resistant bacteria on the skin. The crucial advantage of the local application of photosensitizers followed by irradiation of the area of interest is the fact that independent of the resistance pattern of a bacterium a direct inactivation takes place similarly as with an antiseptic. In this review the physical-chemical and biological basics of photo-dynamic inactivation of bacteria (PIB) will be discussed as well as the possible dermatological indications.

Independent behavior of commensal flora for carriage of fluoroquinolone-resistant bacteria in patients at admission

The important role of commensal flora as a natural reservoir of bacterial resistance is now well established. However, whether the behavior of each commensal flora is similar to that of other floras in terms of rates of carriage and risk factors for bacterial resistance is unknown. During a 6-month period, we prospectively investigated colonization with fluoroquinolone-resistant bacteria in the three main commensal floras from hospitalized patients at admission, targeting Escherichia coli in the fecal flora, coagulase-negative Staphylococcus (CNS) in the nasal flora, and α-hemolytic streptococci in the pharyngeal flora. Resistant strains were detected on quinolone-containing selective agar. Clinical and epidemiological data were collected. A total of 555 patients were included. Carriage rates of resistance were 8.0% in E. coli, 30.3% in CNS for ciprofloxacin, and 27.2% in streptococci for levofloxacin; 56% of the patients carried resistance in at least one flora but only 0.9% simultaneously in all floras, which is no more than random. Risk factors associated with the carriage of fluoroquinolone-resistant strains differed between fecal E. coli (i.e., colonization by multidrug-resistant bacteria) and nasal CNS (i.e., age, coming from a health care facility, and previous antibiotic treatment with a fluoroquinolone) while no risk factors were identified for pharyngeal streptococci. Despite high rates of colonization with fluoroquinolone-resistant bacteria, each commensal flora behaved independently since simultaneous carriage of resistance in the three distinct floras was uncommon, and risk factors differed. Consequences of environmental selective pressures vary in each commensal flora according to its local specificities (clinical trial NCT00520715 [http://clinicaltrials.gov/ct2/show/NCT00520715]).

Efficacy of besifloxacin in an early treatment model of methicillin-resistant Staphylococcus aureus keratitis

PURPOSE

To determine the effectiveness of topically applied besifloxacin, gatifloxacin, and moxifloxacin for the early treatment of experimental methicillin-resistant Staphylococcus aureus (MRSA) keratitis.

METHODS

Ten hours post-MRSA infection, rabbit eyes were treated topically with 19 doses of phosphate-buffered saline (PBS), besifloxacin, gatifloxacin, or moxifloxacin. Slit-lamp examinations were performed before and after the inoculation. Corneas were harvested for bacterial quantitation and minimal inhibitory concentrations (MICs) were determined.

RESULTS

All 3 fluoroquinolones significantly lowered the clinical severity of the infection as compared to treatment with PBS (P < 0.05). However, the mean log(10) colony-forming unit (CFU) recovered from besifloxacin-treated corneas was significantly lower than all other treatment groups (P < 0.01). CFU recovered from corneas treated with moxifloxacin and PBS showed no significant difference (P = 0.12). Corneas treated with gatifloxacin had a significantly lower log(10) CFU recovered as compared to PBS-treated corneas (P < 0.01). The MICs for gatifloxacin and moxifloxacin were 8 microg/mL, whereas the MIC for besifloxacin was 1 microg/mL.

CONCLUSIONS

All 3 fluoroquinolones significantly lowered the clinical severity of the infection. Besifloxacin had an 8-fold lower MIC for MRSA than gatifloxacin and moxifloxacin, and was significantly more effective than gatifloxacin and moxifloxacin in reducing the number of MRSA in the rabbit cornea.

Dermatotoxic effects of orally administered ciprofloxacin in sweating and nonsweating animal models

CONTEXT

Some drugs, such as ciprofloxacin (CFX), that are excreted in sweat may produce some effects/toxicities in the skin structure. In order to differentiate the dermatotoxic effects of drugs due to excretion in sweat, it is essential to perform simultaneous studies in sweating and nonsweating animal models.

OBJECTIVE

To determine the dermatotoxic effects of CFX in sweating (goats) and nonsweating (rabbits) animals and to determine whether there is a relationship between dermatotoxicity and the blood CFX concentration.

MATERIALS AND METHODS

CFX was administered orally at the dose rate of 20 mg/kg body weight to goats (n = 16) and rabbits (n = 16) for 1 and 2 weeks, while control animals were given vehicle (water). Skin biopsies were taken after 1- and 2-week administration of CFX and processed histologically. Similarly, the CFX concentration in the plasma samples was analyzed by high-performance liquid chromatography (HPLC).

RESULTS

Mean ± standard error (SE) epidermal thickness (μm) was 26.2 ± 0.2, 38.6 ± 2.05, and 37.8 ± 1.8 for the control, 1-week-treated, and 2-week-treated goats and 16.06 ± 2.39, 50.67 ± 6.61, and 34.03 ± .12 for the control, 1-week-treated, and 2-week-treated rabbits, respectively. Mean ± SE epidermal cell layers were 2.08 ± 0.08, 3.42 ± 0.16, and 3.25 ± 0.21 in the control, 1-week-treated, and 2-week-treated goats and 1 ± 0, 3.08 ± 0.37, and 1.83 ± 0.35 in the control, 1-week-treated, and 2-week-treated rabbits, respectively. Mean ± SE plasma concentration (μg/mL) of CFX was 0.37 ± 0.06 and 0.30 ± 0.05 in the 1- and 2-week-treated goats and 0.13 ± 0.04 and 0.14 ± 0.09 in the 1- and 2-week-treated rabbits, respectively.

CONCLUSION

Microscopically, increases in epidermal thickness, number of cell layers, and cell infiltration were observed in both sweating and nonsweating animals, indicating that the dermatotoxic effects may not be due to CFX excretion in sweat. No relationship was found between dermatotoxicity and blood CFX concentration in both animal models.

Structure, function and contribution of polysaccharide intercellular adhesin (PIA) to Staphylococcus epidermidis biofilm formation and pathogenesis of biomaterial-associated infections

Staphylococcus epidermidis is of major importance in infections associated with indwelling medical devices. The tight pathogenic association is essentially linked to the species ability to form adherent biofilms on artificial surfaces. Aiming at identifying novel targets for vaccination or therapy much effort has been made to unravel the molecular mechanisms leading to S. epidermidis biofilm formation. At present, polysaccharide intercellular adhesin (PIA) is the best studied factor involved in S. epidermidis biofilm accumulation. PIA is a glycan of beta-1,6-linked 2-acetamido-2-deoxy-D-glucopyranosyl residues of which 15 % are non-N-acetylated. PIA-producing S. epidermidis are widespread in clinical strain collections and PIA synthesis has been shown to be essential for S. epidermidis virulence. Moreover, PIA homologues have been identified in many other staphylococcal species, including the major human pathogen Staphylococcus aureus, and also Gram-negative human pathogens, suggesting that it might represent a more general pathogenicity principle in biofilm-related infections. In this review the current knowledge about the structure and biosynthesis of PIA is summarized. Additionally, information on its role in pathogenesis of biomaterial-related and other type of infections and the potential use of PIA and related compounds for prevention of infection is discussed.

Ciprofloxacin dosage and emergence of resistance in human commensal bacteria

BACKGROUND

Although optimization of the fluoroquinolone dosage increases the efficacy of this class of drugs against bacterial infections, its impact on the emergence of resistance in commensal bacteria is unknown.

METHODS

Six different 14-day dosages of oral ciprofloxacin were randomly assigned to 48 healthy volunteers. Individual pharmacokinetic and pharmacodynamic parameters combining antibiotic exposure in plasma, saliva, and stool specimens and ciprofloxacin minimum inhibitory concentrations (MICs) and mutant prevention concentrations against viridans group streptococci in the pharyngeal flora and Escherichia coli in the fecal flora were estimated. Their links with the emergence of resistance to nalidixic acid or ciprofloxacin in the fecal flora and to levofloxacin in the pharyngeal flora 7, 14, or 42 days after ciprofloxacin initiation were investigated.

RESULTS

Resistance emerged in the fecal and pharyngeal flora of 25% and 33% of the subjects, respectively, mainly when local concentrations of ciprofloxacin were less than the MIC. No variable that integrated pharmacokinetic data and pharmacodynamic parameters was found to differ significantly between the subjects in whom resistance emerged and those in whom it did not. Probabilities of the emergence of resistance were not significantly different across the different antibiotic dosages.

CONCLUSIONS

Selection of resistant commensals during ciprofloxacin therapy is a frequent ecological side effect that is not preventable by dosage optimization. Trial registration. Clinical Trials.gov identifier: NCT00190151.

Hospital strain colonization by Staphylococcus epidermidis

The skin and mucous membranes of healthy subjects are colonized by strains of Staphylococcus epidermidis showing a high diversity of genomic DNA polymorphisms. Prolonged hospitalization and the use of invasive procedures promote changes in the microbiota with subsequent colonization by hospital strains. We report here a patient with prolonged hospitalization due to chronic pancreatitis who was treated with multiple antibiotics, invasive procedures and abdominal surgery. We studied the dynamics of skin colonization by S. epidermidis leading to the development of catheter-related infections and compared the genotypic profile of clinical and microbiota strains by pulsed field gel electrophoresis. During hospitalization, the normal S. epidermidis skin microbiota exhibiting a polymorphic genomic DNA profile was replaced with a hospital-acquired biofilm-producer S. epidermidis strain that subsequently caused repetitive catheter-related infections.

Antimicrobial use: risk driver of multidrug resistant microorganisms in healthcare settings

PURPOSE OF REVIEW

This review explores recent evidence on the association between antibiotics usage and resistance.

RECENT FINDINGS

A meta-analysis showed that the risk of acquiring methicillin-resistant Staphylococcus aureus was increased by 1.8-fold in patients who had taken antibiotics. Such risk was almost three-times greater after using quinolones or glycopeptides. Significant heterogeneity between studies was mainly related to study designs. A Cochrane systematic review suggested that, although the quality of the evidence was poor, interventions to improve hospital antibiotic prescribing were associated with a reduction in the incidence of antimicrobial resistant pathogens. Against this evidence, mupirocin-resistant S. aureus and linezolid-resistant vancomycin-resistant enterococci (VRE) were detected in institutions where these drugs were not widely used. Studies assessing the impact of vancomycin prescribing restriction on VRE rates were heterogeneous and the effectiveness of such interventions remains poorly defined. Important confounders of studies, other than study design, are the lack of analysis of secular trends of infections, colonization pressure in the ward and duration of follow up.

SUMMARY

Available evidence, although not always of high quality, suggests that a link between antibiotics usage at individual and institutional levels and resistant bacteria does exist. Benchmark guidelines for empiric therapy in hospitalized patients, taking into consideration not only patients' needs but also ecological costs of resistance, should be rapidly developed.

[Reducing the duration of antibiotic therapy in acute community-acquired pneumonia]

In theory, the expected benefits of a reduction of the duration of antibiotic therapy during the immunocompetent adult's community-acquired pneumonia (CAP) are of four types: improved observance; reduction of the iatrogenic risk; decrease in the emergence of resistance in the commensal flora; reduction in direct and indirect costs. In practice, the expected benefits must be weighed against the risks of lesser efficiency, i.e., continuing evolution or recurrence. The experimental models of humanized pneumonia treatments show that the period of bacterial eradication is not uniform. If it lasts 48 hours for pneumonia with sensitive pneumococci, it is longer for pneumococci resistant to amoxicillin or atypical bacteria. Thus, if the clinical trials conducted in adults with non-severe CAP, have shown that the duration of treatment could be reduced, depending on the existence or not of a comorbidity, to a 3 days amoxicillin treatment, to a 5 days telithromycin treatment, to a 5 days of levofloxacin 750 mg/day treatment or to a 5 days of ceftriaxone 1g / day treatment, it is logical to assume that such reductions cannot be extrapolated to severe unqualified PACs with severe or to those caused by resistant bacteria or atypical bacteria.