Body site colonization in patients with community-associated methicillin-resistant Staphylococcus aureus and other types of S. aureus skin infections

Study on molecular characteristics of Staphylococcus from yak milk-Xizang

This study investigated the biological characteristics of Staphylococcus strains isolated from Xizangan yak milk by examining the antibiotic resistance phenotypes of 69 isolates against 18 antibiotics, detecting 31 associated resistance genes, identifying 16 virulence genes, and assessing biofilm formation capability. Furthermore, molecular typing techniques including spa typing, multilocus sequence typing (MLST), and Staphylococcus cassette chromosome mec (SCCmec) were used for detailed characterization of the isolates. The findings revealed a high penicillin resistance rate of 72.46%. Resistance genes such as gyrA (100.00%), glrB (92.75%), and gyrB (44.93%) were prevalent. The detection rates were 81.16% and 55.07% for the beta-lactamase gene blaZ and the mecA gene, respectively. Among the tested virulence genes, lukS, lukF, hla, clfA, and icaD were detected in 40.58% of isolates, while sec was detected in 24.64%. MLST typing identified four isolates belonging to the ST62623 type and 24 other isolates representing novel ST types not reported on PubMLST.org. Spa typing revealed spa types t1940 (n = 9), t3022 (n = 8), t4558 (n = 6), t4236 (n = 3), t4445 (n = 1), and one unreported spa type. For SCCmec typing, 11 isolates were typed as SCCmec IVb and 9 as SCCmec V. These findings significantly enhance our understanding of the biological characteristics of Staphylococcus strains derived from Xizangan yak milk.

Emergence of persister cells in Staphylococcus aureus: calculated or fortuitous move?

A stable but reversible phenotype switch from normal to persister state is advantageous to the intracellular pathogens to cause recurrent infections and to evade the host immune system. Staphylococcus aureus is a versatile opportunistic pathogen known to cause chronic infections with significant mortality. One of the notable features is the ability to switch to a per-sisters cell, which is found in planktonic and biofilm states. This phenotypic switch is always an open question to explore the hidden fundamental science that coheres with a calculated or fortuitous move. Toxin-antitoxin modules, nutrient stress, and an erroneous translation-enabled state of dormancy entail this persistent behaviour in S. aureus. It is paramount to get a clear picture of why the cell chooses to enter a persistent condition, as it would decide the course of treatment. Analyzing the exit from a persistent state to an active state and the subsequent repercussion of this transition is essential to determine its role in chronic infections. This review attempts to provide a constructed argument discussing the most widely accepted mechanisms and identifying the various attributes of persistence.

Dynamics of Staphylococcus aureus in patients and the hospital environment in a tertiary care hospital in the Netherlands

BACKGROUND

The dynamics of Staphylococcus aureus in patients and the hospital environment are relatively unknown. We studied these dynamics in a tertiary care hospital in the Netherlands.

METHODS

Nasal samples were taken from adult patients at admission and discharge. Isolates cultured from clinical samples taken before and during hospitalization from these patients were included. Environmental samples of patient rooms were taken over a three-year period. Finally, isolates from clinical samples from patients with an epidemiological link to S. aureus positive rooms were included. Staphylococcal protein A (spa) typing was performed.

RESULTS

Nasal samples were taken from 673 patients. One hundred eighteen (17.5%) were positive at admission and discharge, 15 (2.2%) patients acquired S. aureus during hospitalization. Nineteen patients had a positive clinical sample during hospitalization, 15.9% of the S. aureus were considered as from an exogenous source. One hundred and forty (2.8%) environmental samples were S. aureus positive. No persistent contamination of surfaces was observed. Isolates were highly diverse: spa typing was performed for 893 isolates, identifying 278 different spa types, 161 of these spa types were observed only once.

CONCLUSION

Limited transmission could be identified between patients and the hospital environment, and from patient-to-patient. Exogenous acquisition was assumed to occur in 15% of clinical samples. Environmental contamination was infrequent, temporarily, and coincided with the strain from the patient admitted to the room at that time. MRSA was rare and not found in the environment.

Preparation and characterization of porous membranes of glucomannan and silver decorated cellulose nanocrystals for application as biomaterial

Bacterial infection usually represents a threat in medical wound care, due to the increase in treatment complexity and the risk of antibiotic resistance. For presenting interesting characteristics for the use as biomaterial, natural polymers have been explored for this application. Among them, a promising candidate is the konjac glucomannan (KGM) with outstanding biocompatibility and biodegradability but lack of antibacterial activity. In this study, KGM was combined with silver decorated cellulose nanocrystals (CNC-Ag) to prepare membranes by using a recent reported casting-freezing method. The results highlight the potential anti-adhesive activity of the new materials against Staphylococcus aureus upon contact, without the burst release of silver nanoparticles. Furthermore, the incorporation of CNC enhanced the thermal stability of these membranes while preserving the favorable mechanical properties of the KGM-based material. These findings highlight a straightforward approach to enhance the antibacterial properties of natural polymers, which can be effectively useful in medical devices like wound dressings that typically lack such properties.

Bacterial Membrane Vesicles: Physiological Roles, Infection Immunology, and Applications

Bacterial or fungal membrane vesicles, traditionally considered as microbial metabolic wastes, are secreted mainly from the outer membrane or cell membrane of microorganisms. However, recent studies have shown that these vesicles play essential roles in direct or indirect communications among microorganisms and between microorganisms and hosts. This review aims to provide an updated understanding of the physiological functions and emerging applications of bacterial membrane vesicles, with a focus on their biogenesis, mechanisms of adsorption and invasion into host cells, immune stimulatory effects, and roles in the much-concerned problem of bacterial resistance. Additionally, the potential applications of these vesicles as biomarkers, vaccine candidates, and drug delivery platforms are discussed.

Bacterial Decolonization for Prevention of Radiation Dermatitis: A Randomized Clinical Trial

Importance

Evidence-based approaches for the prevention of acute radiation dermatitis (ARD) are limited, and additional strategies are necessary to optimize care.

Objective

To determine the efficacy of bacterial decolonization (BD) to reduce ARD severity compared with standard of care.

Design, Setting, and Participants

This phase 2/3 randomized clinical trial was conducted from June 2019 to August 2021 with investigator blinding at an urban academic cancer center and enrolled patients with breast cancer or head and neck cancer receiving radiation therapy (RT) with curative intent. Analysis was performed on January 7, 2022.

Interventions

Intranasal mupirocin ointment twice daily and chlorhexidine body cleanser once daily for 5 days prior to RT and repeated for 5 days every 2 weeks through RT.

Main Outcomes and Measures

The primary outcome as planned prior to data collection was the development of grade 2 or higher ARD. Based on wide clinical variability of grade 2 ARD, this was refined to grade 2 ARD with moist desquamation (grade 2-MD).

Results

Of 123 patients assessed for eligibility via convenience sampling, 3 were excluded, and 40 refused to participate, with 80 patients in our final volunteer sample. Of 77 patients with cancer (75 patients with breast cancer [97.4%] and 2 patients with head and neck cancer [2.6%]) who completed RT, 39 were randomly assigned BC, and 38 were randomly assigned standard of care; the mean (SD) age of the patients was 59.9 (11.9) years, and 75 (97.4%) were female. Most patients were Black (33.7% [n = 26]) or Hispanic (32.5% [n = 25]). Among patients with breast cancer and patients with head and neck cancer (N = 77), none of the 39 patients treated with BD and 9 of the 38 patients (23.7%) treated with standard of care developed ARD grade 2-MD or higher (P = .001). Similar results were observed among the 75 patients with breast cancer (ie, none treated with BD and 8 [21.6%] receiving standard of care developed ARD grade ≥2-MD; P = .002). The mean (SD) ARD grade was significantly lower for patients treated with BD (1.2 [0.7]) compared with patients receiving standard of care (1.6 [0.8]) (P = .02). Of the 39 patients randomly assigned to BD, 27 (69.2%) reported regimen adherence, and only 1 patient (2.5%) experienced an adverse event related to BD (ie, itch).

Conclusions and Relevance

The results of this randomized clinical trial suggest that BD is effective for ARD prophylaxis, specifically for patients with breast cancer.

Trial Registration

ClinicalTrials.gov Identifier: NCT03883828.

Detection of Oxacillin/Cefoxitin Resistance in Staphylococcus aureus Present in Recurrent Tonsillitis

BACKGROUND

Recurrent tonsillitis is one of the most common diseases in childhood, caused many times by ß-lactam-resistant S. aureus. The objective of this study was to investigate an alternative method to identify resistance to oxacillin/cefoxitin in S. aureus from hospitalized children with recurrent tonsillitis.

METHODS

The samples of S. aureus came from patients with recurrent tonsillitis and were used in 16S rRNA sequencing and an antibiogram test for identification and verifying resistance, after which HSI methodology were applied for separation of S. aureus resistances.

RESULTS

The S. aureus isolated showed sensitivity to oxacillin/cefoxitin and the diagnostic images show a visual description of the resistance different groups formed, that may be related to sensitivity and resistance to oxacillin/cefoxitin, characterizing the MRSA S. aureus.

CONCLUSIONS

Samples that showed phenotypic resistance to oxacillin/cefoxitin were clearly separated from samples that did not show this resistance. A PLS-DA model predicted the presence of resistance to oxacillin/cefoxitin in S. aureus samples and it was possible to observe the pixels classified as MRSA. The HSI was able to successfully discriminate samples in replicas that were sensitive and resistant, based on the calibration model it received.

Chlorhexidine and Mupirocin for Clearance of Methicillin-Resistant Staphylococcus aureus Colonization After Hospital Discharge: A Secondary Analysis of the Changing Lives by Eradicating Antibiotic Resistance Trial

BACKGROUND

The CLEAR Trial demonstrated that a multisite body decolonization regimen reduced post-discharge infection and hospitalization in methicillin-resistant Staphylococcus aureus (MRSA) carriers. Here, we describe decolonization efficacy.

METHODS

We performed a large, multicenter, randomized clinical trial of MRSA decolonization among adult patients after hospital discharge with MRSA infection or colonization. Participants were randomized 1:1 to either MRSA prevention education or education plus decolonization with topical chlorhexidine, oral chlorhexidine, and nasal mupirocin. Participants were swabbed in the nares, throat, axilla/groin, and wound (if applicable) at baseline and 1, 3, 6, and 9 months after randomization. The primary outcomes of this study are follow-up colonization differences between groups.

RESULTS

Among 2121 participants, 1058 were randomized to decolonization. By 1 month, MRSA colonization was lower in the decolonization group compared with the education-only group (odds ration [OR] = 0.44; 95% confidence interval [CI], .36-.54; P ≤ .001). A similar magnitude of reduction was seen in the nares (OR = 0.34; 95% CI, .27-.42; P < .001), throat (OR = 0.55; 95% CI, .42-.73; P < .001), and axilla/groin (OR = 0.57; 95% CI, .43-.75; P < .001). These differences persisted through month 9 except at the wound site, which had a relatively small sample size. Higher regimen adherence was associated with lower MRSA colonization (P ≤ .01).

CONCLUSIONS

In a randomized, clinical trial, a repeated post-discharge decolonization regimen for MRSA carriers reduced MRSA colonization overall and at multiple body sites. Higher treatment adherence was associated with greater reductions in MRSA colonization.

Does Nasal Screening for Methicillin-Resistant Staphylococcus aureus (MRSA) Prevent Deep Surgical Site Infections for Elective Cervical Spinal Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The objective of this study was to determine the relationship between nasal methicillin-resistant Staphylococcus aureus (MRSA) testing and surgical site infection (SSI) rates in the setting of primary posterior cervical instrumented spine surgery.

SUMMARY OF BACKGROUND DATA

Preoperative MRSA screening and decolonization has demonstrated success for some orthopedic subspecialties in prevention of SSIs. Spine surgery, however, has seen varied results, potentially secondary to the anatomic and surgical heterogeneity of the patients included in prior studies. Given that prior research has demonstrated greater propensity for gram positive SSIs in the cervical spine, we sought to investigate if MRSA screening would be more impactful in the cervical spine.

MATERIALS AND METHODS

Adult patients undergoing primary instrumented posterior cervical procedures from January 2015 to December 2019 were reviewed for MRSA testing <90 days before surgery, preoperative mupirocin, perioperative antibiotics, and SSI defined as operative incision and drainage (I&D) <90 days after surgery. Logistic regression modeling used SSI as the primary outcome, MRSA screening as primary predictor, and clinical and demographic factors as covariates.

RESULTS

This study included 668 patients, of whom MRSA testing was performed in 212 patients (31.7%) and 6 (2.8%) were colonized with MRSA. Twelve patients (1.8%) underwent an I&D. On adjusted analysis, preoperative MRSA testing was not associated with postoperative I&D risk. Perioperative vancomycin similarly had no association with postoperative I&D risk. Notably, 6 patients (50%) grew methicillin sensitive Staphylococcus aureus from intraoperative cultures, with no cases of MRSA.

CONCLUSIONS

There was no association between preoperative nasal MRSA screening and SSIs in primary posterior cervical instrumented procedures, nor was there any association between vancomycin or infection rate. Furthermore, there was a preponderance of gram positive infections but none caused by MRSA. Given these findings, the considerable cost and effort associated with MRSA testing in the setting of primary posterior cervical instrumentation may not be justified. Further research should investigate if higher-risk scenarios demonstrate greater utility of preoperative testing.

Unsuspected Clonal Spread of Methicillin-Resistant Staphylococcus aureus Causing Bloodstream Infections in Hospitalized Adults Detected Using Whole Genome Sequencing

BACKGROUND

Though detection of transmission clusters of methicillin-resistant Staphylococcus aureus (MRSA) infections is a priority for infection control personnel in hospitals, the transmission dynamics of MRSA among hospitalized patients with bloodstream infections (BSIs) has not been thoroughly studied. Whole genome sequencing (WGS) of MRSA isolates for surveillance is valuable for detecting outbreaks in hospitals, but the bioinformatic approaches used are diverse and difficult to compare.

METHODS

We combined short-read WGS with genotypic, phenotypic, and epidemiological characteristics of 106 MRSA BSI isolates collected for routine microbiological diagnosis from inpatients in 2 hospitals over 12 months. Clinical data and hospitalization history were abstracted from electronic medical records. We compared 3 genome sequence alignment strategies to assess similarity in cluster ascertainment. We conducted logistic regression to measure the probability of predicting prior hospital overlap between clustered patient isolates by the genetic distance of their isolates.

RESULTS

While the 3 alignment approaches detected similar results, they showed some variation. A gene family-based alignment pipeline was most consistent across MRSA clonal complexes. We identified 9 unique clusters of closely related BSI isolates. Most BSIs were healthcare associated and community onset. Our logistic model showed that with 13 single-nucleotide polymorphisms, the likelihood that any 2 patients in a cluster had overlapped in a hospital was 50%.

CONCLUSIONS

Multiple clusters of closely related MRSA isolates can be identified using WGS among strains cultured from BSI in 2 hospitals. Genomic clustering of these infections suggests that transmission resulted from a mix of community spread and healthcare exposures long before BSI diagnosis.

Skin Microbiome, Metabolome and Skin Phenome, from the Perspectives of Skin as an Ecosystem

Skin is a complex ecosystem colonized by millions of microorganisms, including bacteria, fungi, and viruses. Skin microbiota is believed to exert critical functions in maintaining host skin health. Profiling the structure of skin microbial community is the first step to overview the ecosystem. However, the community composition is highly individualized and extremely complex. To explore the fundamental factors driving the complexity of the ecosystem, namely the selection pressures, we review the present studies on skin microbiome from the perspectives of ecology. This review summarizes the following: (1) the composition of substances/nutrients in the cutaneous ecological environment that are derived from the host and the environment, highlighting their proposed function on skin microbiota; (2) the features of dominant skin commensals to occupy ecological niches, through self-adaptation and microbe-microbe interactions; (3) how skin microbes, by their structures or bioactive molecules, reshape host skin phenotypes, including skin immunity, maintenance of skin physiology such as pH and hydration, ultraviolet (UV) protection, odor production, and wound healing. This review aims to re-examine the host-microbe interactions from the ecological perspectives and hopefully to give new inspiration to this field.

Multifunctional Filter Membranes Based on Self-Assembled Core-Shell Biodegradable Nanofibers for Persistent Electrostatic Filtration through the Triboelectric Effect

The massive production of polymer-based respiratory masks during the COVID-19 pandemic has rekindled the issue of environmental pollution from nonrecyclable plastic waste. To mitigate this problem, conventional filters should be redesigned with improved filtration performance over the entire operational life while also being naturally degradable at the end. Herein, we developed a functional and biodegradable polymeric filter membrane consisting of a polybutylene adipate terephthalate (PBAT) matrix blended with cetyltrimethylammonium bromide (CTAB) and montmorillonite (MMT) clay, whose surface properties have been modified through cation exchange reactions for good miscibility with PBAT in an organic solvent. Particularly, the spontaneous evolution of a partial core-shell structure (i.e., PBAT core encased by CTAB-MMT shell) during the electrospinning process amplified the triboelectric effect as well as the antibacterial/antiviral activity that was not observed in naive PBAT. Unlike the conventional face mask filter that relies on the electrostatic adsorption mechanism, which deteriorates over time and/or due to external environmental factors, the PBAT@CTAB-MMT nanofiber membrane (NFM)-based filter continuously retains electrostatic charges on the surface due to the triboelectric effect of CTAB-MMT. As a result, the PBAT@CTAB-MMT NFM-based filter showed high filtration efficiencies (98.3%, PM_0.3) even at a low differential pressure of 40 Pa or less over its lifetime. Altogether, we not only propose an effective and practical solution to improve the performance of filter membranes while minimizing their environmental footprint but also provide valuable insight into the synergetic functionalities of organic-inorganic hybrid materials for applications beyond filter membranes.

Understanding short-term transmission dynamics of methicillin-resistant Staphylococcus aureus in the patient room

OBJECTIVE

Little is known about the short-term dynamics of methicillin-resistant Staphylococcus aureus (MRSA) transmission between patients and their immediate environment. We conducted a real-life microbiological evaluation of environmental MRSA contamination in hospital rooms in relation to recent patient activity.

DESIGN

Observational pilot study.

SETTING

Two hospitals, hospital 1 in Zurich, Switzerland, and hospital 2 in Ann Arbor, Michigan, United States.

PATIENTS

Inpatients with MRSA colonization or infection.

METHODS

At baseline, the groin, axilla, nares, dominant hands of 10 patients and 6 environmental high-touch surfaces in their rooms were sampled. Cultures were then taken of the patient hand and high-touch surfaces 3 more times at 90-minute intervals. After each swabbing, patients' hands and surfaces were disinfected. Patient activity was assessed by interviews at hospital 1 and analysis of video footage at hospital 2. A contamination pressure score was created by multiplying the number of colonized body sites with the activity level of the patient.

RESULTS

In total, 10 patients colonized and/or infected with MRSA were enrolled; 40 hand samples and 240 environmental samples were collected. At baseline, 30% of hands and 20% of high-touch surfaces yielded MRSA. At follow-up intervals, 8 (27%) of 30 patient hands, and 10 (6%) of 180 of environmental sites were positive. Activity of the patient explained 7 of 10 environmental contaminations. Patients with higher contamination pressure score showed a trend toward higher environmental contamination.

CONCLUSION

Environmental MRSA contamination in patient rooms was highly dynamic and was likely driven by the patient's MRSA body colonization pattern and the patient activity.

The Effect of Systemic Antibiotics for Suppurative Skin and Soft Tissue Infections on Skin Microbiome

Background

Skin and soft tissue infections (SSTIs) are very common bacterial infections. There are few data on the microbiome of persons with and without SSTIs and the effects of systemic antibiotic therapy.

Methods

We sampled the skin microbiome from 10 outpatients with acute suppurative SSTI before and after systemic antibiotic therapy and enrolled 10 matched controls. Samples were collected at 6 skin body sites (occipital scalp, axilla, interdigital hand web spaces, gluteal crease, inguinal creases, and popliteal fossa), 2 mucosal sites (throat, anterior nares), and the site of skin infection (for case subjects) at baseline and a week later after abscess incision, drainage, and oral antibiotics.

Result

Among 10 SSTI cases, mean age was 41.5 years and 3 had diabetes mellitus. The gluteal crease at baseline had higher α-diversity in controls vs cases (P = .039); β-diversity analysis showed significant differences in overall bacterial community composition (P = .046). However, at other body sites there were no significant differences by either α- or β-diversity. Systemic antibiotic use did not affect body site diversity indices except at the SSTI site (α-diversity increased, P = .001).

Conclusions

We surprisingly found no significant differences in microbiome comparing noninfected skin sites before and after systemic SSTI antibiotic therapy nor significant differences at noninfected skin sites between SSTI cases and uninfected controls. We also found minimal significant differences between microbiome diversity and bacterial signatures at noninfected skin sites between patients with acute skin infection and uninfected controls. Our findings challenge the dogma that systemic antibiotics impact the skin microbiome.

Molecular Characterization of Staphylococcus aureus Strains Isolated from Mobile Phones

The widespread use of mobile phones (MP) among healthcare personnel might be considered as an important source of contamination. One of the most pathogenic bacteria to humans is Staphylococcus aureus, which can be transmitted through the constant use of MP. Nevertheless, which specific type of strains are transmitted and which are their sources have not been sufficiently studied. The aim of this study is to determine the source of contamination of MP and characterize the corresponding genotypic and phenotypic properties of the strains found. Nose, pharynx, and MP samples were taken from a group of health science students. We were able to determinate the clonality of the isolated strains by pulsed-field gel electrophoresis (PFGE) and spa gene typing (spa-type). Adhesin and toxin genes were detected, and the capacity of biofilm formation was determined. Several of the MP exhibited strains of S. aureus present in the nose and/or pharynx of their owners. methicillin-susceptible Staphylococcus aureus (MSSA), hospital-acquired methicillin-resistant S. aureus (HA-MRSA), and community-acquired methicillin-resistant S. aureus (CA-MRSA) strains were found, which indicated a variety of genotypes. This study concludes that MP can be contaminated with the strains of S. aureus present in the nose and/or pharynx of the owners; these strains can be of different types and there is no dominant genotype.

Differential microbiological spectrum and resistance pattern in periprosthetic hip joint infections: a matched-cohort analysis comparing direct anterior versus lateral approach

BACKGROUND

In recent years, total hip arthroplasty via the direct anterior approach (DAA) has become more common. Little is known on the influence of the surgical approach on the microbiological spectrum and resistance pattern in periprosthetic hip joint infections. The aim of the present study was to evaluate the microbiological spectrum and resistance pattern in periprosthetic hip joint infections comparing the direct anterior versus lateral approach in a matched-cohort analysis at a single institution.

METHODS

Patients who underwent revision hip arthroplasty due to PJI following primary total hip arthroplasty with culture positive microbiology were analyzed. In all study patients, both the primary surgery and the revisions surgery were performed at the same institution. Only patients in whom primary surgery was performed via a direct anterior or lateral approach were included (n = 87). A matched cohort analysis was performed to compare the microbiological spectrum and resistance pattern in PJI following direct anterior (n = 36) versus lateral (n = 36) primary THA.

RESULTS

We identified both a significantly different microbiological spectrum and resistance pattern in PJI comparing direct anterior versus lateral approach THA. Cutibacterium avidum was obtained more frequently in the anterior subgroup (22.2% vs. 2.8%, p = 0.028). In the subgroup of infections with Staphylococcus aureus (n = 12), methicillin resistance was detected in 3/5 cases in the direct anterior group versus 0/7 cases in the lateral group (p = 0.045). Overall, Staphylococcus epidermidis was the most common causative microorganism in both groups (direct anterior: 36.1%; lateral: 27.8%, p = 0.448).

CONCLUSION

The present study indicates a potential influence of the localization of the skin incision in THA on the microbiological spectrum and resistance pattern in PJI. Cutibacterium avidum seemed to be a more common causative microorganism in PJI in patients who underwent direct anterior compared to lateral approach THA.

Clinical Spectrum and Resistance Profile of Staphylococcus Infections in a Peri Urban Tertiary Care Hospital

Staphylococcus may be evaluated to be a serious microorganism to colonizes and contaminate both the healthy and immuno-competent people in the community along with the hospitalized patients with decreased immunity. This bacterium has been commonly present on the skin and in the nasal cavity of the human body. In the particular sites the organisms may give rise to local diseases of the nose, urethra, vagina and gastrointestinal tract, skin however most of them are minor and not associated with any mortality. S. aureus as well as coagulase-negative staphylococcus which are gram-positive bacteria that lives on the upper respiratory, mouth and skin structure creation, are the possible element for nosocomial and opportunistic disease in humans as well as in animals. Major complications involved with staphylococcus involved SSI, bullous impetigo, skin & soft tissues infection, bacteremia, pulmonary infections etc. The situation is further complicated by methicillin resistance in staphylococcus. MRSA/MRCoNS are considered as the emerging cause of hospital-acquired infections. it is very necessary to quantify the load of infections in order to achieve good hospital infection control policies. Furthermore, the morbidity and mortality rate may also be reduced in the same manner.

Methicillin-resistant Staphylococcus aureus colonization of infectious and non-infectious skin and soft tissue lesions in patients in Tehran

Background

The most common clinical manifestations of Staphylococcus aureus strains in the community are skin and soft-tissue infections. S. aureus could colonize the body sites and complicate the pathogenesis of skin diseases. S. aureus colonization is a risk factor for severe conditions such as bone and joint infections, pneumonia, bacteremia, and endocarditis. This study aimed to investigate the prevalence of S. aureus strains in skin and soft tissue infections and other skin disorders in patients referring to dermatology clinics and to evaluate the antibiotic resistance pattern and molecular characteristics of S. aureus isolates.

Methods

Skin swabs were collected from the lesional sites in 234 outpatients referring to dermatology clinics in three hospitals in Tehran. Antibiotic susceptibility, biofilm formation, and hemolysis tests were performed for isolates. PCR was done for SCCmec typing, agr grouping, and virulence genes detecting.

Results

The prevalence of S. aureus strains among patients with skin and soft-tissue infections and other skin lesions was 44.77% (30/67) and 44.91% (75/167), respectively. Also, 59 (56.19%) isolates were MRSA, 35.57% were HA-MRSA, and 30.5% were CA-MRSA. The psmα gene was more prevalent (62.8%) among isolates, followed by hlaα (56.1%), tsst-1 (15.2%) eta (13.3%), etb (6.6%), and pvl (2.8%). The agr specificity groups I, II, III, and IV were identified in 49.5, 21.9, 11.4, and 14.2% of S. aureus isolates, respectively. Most (56%) S. aureus isolates produced a moderate biofilm, and 23.8% of them produced strong biofilms. α-hemolysin (46.6%), β-hemolysin (25.7%), γ-hemolysin (19%), and both α and β-hemolysin (5.7%) were also produced by isolates.

Conclusion

The present study results indicated high colonization of skin lesions by HA-MRSA and CA-MRSA clones; MRSA strains were more resistant to antibiotics, contained various toxin genes, and were able to form biofilms. Therefore, they could play a vital role in the pathogenesis of various skin diseases; also, they could spread and cause infections in other body sites. Eradication and decolonization strategies could prevent recurrent infections and the spread of resistant strains and improve skin conditions.

Hydrogen Peroxide Affects Growth of S. aureus Through Downregulation of Genes Involved in Pyrimidine Biosynthesis

Reactive oxygen species (ROS) play a crucial role in the cellular defense against S. aureus, as evidenced by the importance of this pathogen in patients lacking the ROS-generating phagocyte NADPH oxidase NOX2. ROS concentrations required to kill S. aureus in vitro are much higher than those found in the phagosome. We therefore hypothesized that sublethal ROS concentrations may play a role in S. aureus gene dysregulation and investigated the in vitro transcriptomic response of S. aureus to sublethal concentrations of hydrogen peroxide (H₂O₂). A striking observation of these experiments was a coordinated and massive downregulation of genes involved in pyrimidine metabolism. Using transposon insertion mutants, we demonstrated that deletion of carA, a gene involved in pyrimidine synthesis, led to a significant growth defect and to an increased sensitivity of S. aureus to added H₂O₂. The phenotype of the carA mutant could be reversed through supplementation with the pyrimidine precursor uracil, or with a multicopy vector encoding carA. As opposed to the impact of ROS on extracellular survival, carA deletion did not affect the intracellular survival in neutrophils. Our results raise the possibility that ROS-dependent downregulation of pyrimidine metabolism might be a survival strategy of S. aureus, allowing colonization through intracellular survival, while decreasing the risk of killing the host through dampened extracellular growth.

A naturally occurring point mutation in the hyaluronidase gene (hysA1) of Staphylococcus aureus UAMS-1 results in reduced enzymatic activity

Hyaluronic acid is a high-molecular-weight polysaccharide that is widely distributed in animal tissues. Bacterial hyaluronidases degrade hyaluronic acid as secreted enzymes and have been shown to contribute to infection. Staphylococcus aureus UAMS-1 is a clinical isolate that codes for two hyaluronidases (hysA1 and hysA2). Previous research has shown the presence of a full-length HysA1 protein from the S. aureus UAMS-1 strain with no evidence of enzymatic activity. In this study, the coding and upstream promoter regions of hysA1 from the S. aureus UAMS-1 strain were cloned, sequenced, and compared to the hysA1 gene from the S. aureus Sanger 252 strain. A single base change resulting in an E480G amino acid change was identified in the hysA1 gene from the S. aureus UAMS-1 strain when compared to the hysA1 gene from S. aureus Sanger 252. A plasmid copy of hysA1 from S. aureus Sanger 252 transduced into an S. aureus UAMS-1 hysA2 deletion mutant strain restored near wild-type levels of enzymatic activity. Homology modeling of the HysA1 hyaluronidase was performed with SWISS-MODEL using hyaluronidase from Streptococcus pneumoniae as the template, followed by a series of structural analyses using PyMOL, PLIP, PDBsum, and HOPE servers. This glutamic acid is highly conserved among hyaluronidases from Staphylococcus and other gram-positive bacteria. A series of structural analyses suggested that Glu-480 in HysA1 is critically responsible for maintaining the structural and functional ensemble of the catalytic and tunnel-forming residues, which are essential for enzyme activity. The missense mutation of Glu-480 to Gly introduces a loss of side chain hydrogen bond interactions with key residues Arg-360 and Arg-364, which are responsible for the tunnel topology, resulting in displacement of the substrate from an ideal position for catalysis through a localized conformational change of the active site. There is a high degree of relatedness among several gram-positive bacterial hyaluronidases; the loss of enzymatic activity of HysA1 in the S. aureus UAMS-1 strain is most likely caused by the mutation identified in our study. The role of hyaluronidase in staphylococcal infection and the redundancy of this gene are yet to be determined.

Repeated intracranial empyema following cranioplasty in a patient with atopic dermatitis: a case report

Background

Atopic dermatitis is a chronic inflammatory skin disease associated with pruritus. Skin affected by atopic dermatitis not only shows a high percentage of Staphylococcus aureus colonization, but corneal barrier dysfunction is also known to occur. It is considered a risk factor for bacterial infections in various areas of the body. However, the relationship between atopic dermatitis and bacterial infection following neurological surgery has not yet been reported. Here, we present a case of atopic dermatitis in which the surgical site became infected twice and finally resolved only after the atopic dermatitis was treated.

Case presentation

A 50-year-old Japanese woman with atopic dermatitis underwent cerebral aneurysm clipping to prevent impending rupture. Postoperatively, she developed repeated epidural empyema following titanium cranioplasty. As a result of atopic dermatitis treatment with oral antiallergy medicines and external heparinoids, postoperative infection was suppressed by using an absorbable plastic plate for cranioplasty. The patient’s postoperative course was uneventful for 16 months.

Conclusions

Atopic dermatitis is likely to cause surgical-site infection in neurosurgical procedures, and the use of a metal implant could promote the development of surgical-site infection in patients with dermatitis.

Prevalences and characteristics of cultivable nasal bacteria isolated from preclinical medical students

OBJECTIVES

Commensal bacteria in the nasal cavity may act as opportunistic pathogens that cause infections under certain conditions. Screening for commensal bacteria in the nasal cavity may aid in understanding their roles in microbiota balance and preventing potential infections.

METHODS

Nasal samples were collected from healthy preclinical medical students and used to inoculate various bacterial culture media, by means of the WaspLab microbiology automated system. Bacterial colonies were then identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Antibiotic resistance phenotypes of Staphylococcus aureus were determined by antibiotic susceptibility tests.

RESULTS

In total, 549 bacterial strains were isolated from 161 participants. These strains included the following genera: Staphylococcus, Streptococcus, Corynebacterium, Dolosigranulum, Bacillus, Micrococcus, Haemophilus, Neisseria, Moraxella, Pseudomonas, and members of Enterobacteriaceae (e.g., Escherichia, Klebsiella, Citrobacter, Enterobacter, and Serratia). Approximately 25.5% of students were carriers of S. aureus; most S. aureus isolates were resistant to penicillin, erythromycin, and clindamycin. The prevalence of methicillin-resistant S. aureus in nasal samples was 4.3%.

CONCLUSIONS

A diverse group of nasal commensal bacteria inhabited our population of healthy volunteers. These data can improve comprehension of the potential roles of these nasal commensal bacteria in regulating microbiota balance and promoting or mitigating potential future infections.

A Longitudinal Study of Adult Patients with Staphylococcus aureus Bacteremia over 11 Years in Korea

BACKGROUND

The temporal changes in the Staphylococcus aureus genotypes causing S. aureus bacteremia (SAB) and the corresponding clinical changes over the last decade in South Korea are rarely investigated.

METHODS

A longitudinal study of adult SAB patients was conducted in a large referral hospital in Seoul, South Korea. Adult monomicrobial SAB patients were enrolled between August 2008 and December 2018. Genotyping was performed by multilocus sequence typing (MLST) and staphylococcal protein A (spa) typing. Trends in changes were identified by linear regression analysis.

RESULTS

Of 1782 adult SAB patients, the blood isolates of 1,778 (99.8%) and 1,634 (91.7%) were determined to be MLST and spa type, respectively. ST5 (-2.626%/year) and ST239 (-0.354%/year) decreased during the study period (P < 0.001 for both), but ST72 (2.009%/yr)-and ST8 (0.567%/yr) increased (P < 0.001 for both). The most common genotype was changed from ST5 in 2008 (44.9%) to ST72 in 2018 (36.3%). Panton-Valentine leukocidin-positive spa-t008-MRSA (USA300) was found in 28.6%. Central venous catheter (CVC)-related SAB (-2.440%/yr) and persistent SAB (-1.016%/yr) decreased, but mortality and recurrence rates were unchanged.

CONCLUSION

Over the last decade, the hospital clones ST5 and ST239 have been replaced by community genotype ST72. This was associated with decreased CVC-related and persistent SAB. Increased USA300 was observed in community and hospital settings. Further research is required to identify the reasons for the ST72 epidemic and predict the impending epidemic of ST8 strains, including USA300.

In Vitro Antibacterial, Anti-Adhesive and Anti-Biofilm Activities of Krameria lappacea (Dombey) Burdet & B.B. Simpson Root Extract against Methicillin-Resistant Staphylococcus aureus Strains

Methicillin-resistant Staphylococcus aureus (MRSA) represents a serious threat to public health, due to its large variety of pathogenetic mechanisms. Accordingly, the present study aimed to investigate the anti-MRSA activities of Krameria lappacea, a medicinal plant native to South America. Through Ultra-High-Performance Liquid Chromatography coupled with High-Resolution Mass spectrometry, we analyzed the chemical composition of Krameria lappacea root extract (KLRE). The antibacterial activity of KLRE was determined by the broth microdilution method, also including the minimum biofilm inhibitory concentration and minimum biofilm eradication concentration. Besides, we evaluated the effect on adhesion and invasion of human lung carcinoma A549 cell line by MRSA strains. The obtained results revealed an interesting antimicrobial action of this extract, which efficiently inhibit the growth, biofilm formation, adhesion and invasion of MRSA strains. Furthermore, the chemical analysis revealed the presence in the extract of several flavonoid compounds and type-A and type-B proanthocyanidins, which are known for their anti-adhesive effects. Taken together, our findings showed an interesting antimicrobial activity of KLRE, giving an important contribution to the current knowledge on the biological activities of this plant.

Staphylococcus aureus-Specific Tissue-Resident Memory CD4+ T Cells Are Abundant in Healthy Human Skin

The skin is an immunocompetent tissue that harbors several kinds of immune cells and a plethora of commensal microbes constituting the skin microbiome. Staphylococcus aureus is a prominent skin pathogen that colonizes a large proportion of the human population. We currently have an incomplete understanding of the correlates of protection against S. aureus infection, however genetic and experimental evidence has shown that CD4⁺ T cells play a key role in orchestrating a protective anti-S. aureus immune response. A high S. aureus-specific memory CD4⁺ T cell response has been reported in the blood of healthy subjects. Since T cells are more abundant in the skin than in blood, we hypothesized that S. aureus-specific CD4⁺ T cells could be present in the skin of healthy individuals. Indeed, we observed proliferation of tissue-resident memory CD4⁺ T cells and production of IL-17A, IL-22, IFN-γ and TNF-β by cells isolated from abdominal skin explants in response to heat-killed S. aureus. Remarkably, these cytokines were produced also during an ex vivo epicutaneous S. aureus infection of human skin explants. These findings highlight the importance of tissue-resident memory CD4⁺ T cells present at barrier sites such as the skin, a primary entry site for S. aureus. Further phenotypical and functional characterization of these cells will ultimately aid in the development of novel vaccine strategies against this elusive pathogen.

Methicillin-Resistant Staphylococcus aureus (MRSA): One Health Perspective Approach to the Bacterium Epidemiology, Virulence Factors, Antibiotic-Resistance, and Zoonotic Impact

Methicillin-resistant Staphylococcus aureus (MRSA) is a major human pathogen and a historically emergent zoonotic pathogen with public health and veterinary importance. In humans, MRSA commonly causes severe infectious diseases, including food poisoning, pyogenic endocarditis, suppurative pneumonia, otitis media, osteomyelitis, and pyogenic infections of the skin, soft tissues. In the horse, MRSA could cause a localized purulent infection and botryomycosis; in cattle and ewe, localized pyogenic infection and severe acute mastitis with marked toxemia; in sheep, abscess disease resembles caseous lymphadenitis caused by anaerobic strains; in dogs and cats, pustular dermatitis and food poisoning; in pig, exudative epidermatitis “greasy pig disease; in birds, MRSA causes bumble-foot. The methicillin resistance could be determined by PCR-based detection of the mecA gene as well as resistance to cefoxitin. In Egypt, MRSA is one of the important occasions of subclinical and clinical bovine mastitis, and the prevalence of MRSA varies by geographical region. In this review, we are trying to illustrate variable data about the host susceptibility, diseases, epidemiology, virulence factors, antibiotic resistance, treatment, and control of MRSA infection.

Opportunities and Obstacles in the Prevention of Skin and Soft-Tissue Infections Among Military Personnel

INTRODUCTION

Skin and soft-tissue infections (SSTIs) are an important cause of infectious disease morbidity among military populations. Due to the high direct and indirect costs associated with SSTIs, particularly with methicillin-resistant Staphylococcus aureus (MRSA) infections, there remains a critical need for the development and evaluation of SSTI prevention strategies among high-risk military personnel. Herein, we review efforts of the Infectious Disease Clinical Research Program (IDCRP) related to the prevention of SSTIs in the military.

METHODS

The IDCRP of the Uniformed Services University has conducted clinical research protocols on SSTI epidemiology and prevention among military personnel since 2009. Observational studies have examined the epidemiology of Staphylococcus aureus colonization and SSTI in training and deployment settings. Two randomized controlled trials of personal hygiene strategies for SSTI prevention at Marine Corps Base Quantico (Virginia) and Fort Benning (Georgia) were performed. Lastly, two vaccine trials have been conducted by the IDCRP, including a Phase 2 S. aureus vaccine trial (currently ongoing) among military trainees.

RESULTS

Military recruits and deployed personnel experience an intense and prolonged exposure to S. aureus, the major causative agent of SSTI. The burden of S. aureus colonization and SSTI is particularly high in military trainees. Hygiene-based trials for S. aureus decolonization among military trainees were not effective in reducing rates of SSTI. In January 2018, the IDCRP initiated a Phase 2 S. aureus vaccine trial among the US Army Infantry training population at Fort Benning.

CONCLUSIONS

In the military, a disproportionate burden of SSTIs is borne by the recruit population. Strategies relying upon routine application of agents for S. aureus decolonization have not been effective in preventing SSTIs. A novel S. aureus vaccine candidate is being currently evaluated in a military training population and may represent a new opportunity to prevent SSTIs for the military.

Evasion of host defenses by intracellular Staphylococcus aureus

Staphylococcus aureus is one of the leading causes of hospital and community-acquired infections worldwide. The increasing occurrence of antibiotic resistant strains and the high rates of recurrent staphylococcal infections have placed several treatment challenges on healthcare systems. In recent years, it has become evident that S. aureus is a facultative intracellular pathogen, able to invade and survive in a range of cell types. The ability to survive intracellularly provides this pathogen with yet another way to evade antibiotics and immune responses during infection. Intracellular S. aureus have been strongly linked to several recurrent infections, including severe bone infections and septicemias. S. aureus is armed with an array of virulence factors as well as an intricate network of regulators that enable it to survive, replicate and escape from a number of immune and nonimmune host cells. It is able to successfully manipulate host cell pathways and use it as a niche to multiply, disseminate, as well as persist during an infection. This bacterium is also known to adapt to the intracellular environment by forming small colony variants, which are metabolically inactive. In this review we will discuss the clinical evidence, the molecular pathways involved in S. aureus intracellular persistence, and new treatment strategies for targeting intracellular S. aureus.

Novel strategies for rapid identification and susceptibility testing of MRSA

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs. Rapid diagnosis of MRSA infections has been associated with positive impact on clinical outcomes.

AREAS COVERED

We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review describes screening and diagnostic test methods for MRSA and their analytical performances with a focus on rapid molecular-based assays including those that are on the horizon. Future novel technologies will allow more rapid detection of phenotypic resistance. In the case of whole-genome sequencing, detection of mutations may predict resistance, transmission, and virulence.

EXPERT OPINION

Currently there are many diagnostic options for the detection of MRSA in surveillance and clinical samples. In general, these are highly accurate and have resulted in improvements in targeted management and reduction in hospital or intensive care unit length of stay for both MSSA and MRSA. Impact on mortality has been variable. Promising novel technologies will not only accurately identify pathogens and detect their resistance markers but will allow discovery of virulence determinants that might further affect patient management.

Antimicrobial approaches in the prevention of Staphylococcus aureus infections: a review

Background

The prophylactic application of antimicrobials that are active against Staphylococcus aureus can prevent infections. However, implementation in clinical practice is limited. We have reviewed antimicrobial approaches for the prevention of S. aureus infections.

Methods

We searched the Cochrane Central Register of Controlled Trials, PubMed/MEDLINE and EMBASE databases and trial registries using synonyms for S. aureus, infections and prevention as search terms. We included randomized controlled trials and systematic reviews only.

Results

Most studies were conducted with mupirocin. Mupirocin is effective in preventing S. aureus infections in patients receiving dialysis treatment and in surgical patients, particularly if the patients are carriers of S. aureus. The combination of mupirocin and chlorhexidine, but not chlorhexidine alone, is also effective against S. aureus infections. So far, vaccines have not proven successful in protecting against S. aureus infections. Regarding prophylactic povidone-iodine and systemic antibiotics, there is limited evidence supporting their effectiveness against S. aureus infections. Antimicrobial honey has not been proven to be more effective or non-inferior to mupirocin in protecting against S. aureus infections.

Conclusions

The current evidence supports the use of mupirocin as prophylaxis for preventing infections with S. aureus, particularly in carriers and in the surgical setting or in patients receiving dialysis treatment. Other antimicrobial agents have not been sufficiently proven to be effective so far, or have been proven ineffective. New trials with vaccines and anti-staphylococcal peptides are currently underway and may lead to new preventive strategies in the future.

Staphylococcus aureus carriage state in healthy adult population and phenotypic and genotypic properties of isolated strains

INTRODUCTION

At present, infections induced by staphylococci, especially methicillin-resistant Staphylococcus aureus (MRSA) are one of key therapeutic and epidemiological problems.

AIM

The assessment of Staphylococcus aureus carrier state occurrence among a healthy adult population as well as determination of phenotypic and genotypic properties of the isolated strains.

MATERIAL AND METHODS

The study included 100 healthy individuals. Material for bacteriological evaluation was collected from the posterior pharyngeal wall and tonsils, nasal vestibule and the skin of anterior nares using a sterile swab. The isolates identified as Staphylococcus aureus were analysed further, towards slime-forming capacity and the presence of genes mecA and nuc.

RESULTS

The analysis included 300 samples obtained from the posterior vault of the pharynx and tonsils, nasal vestibule and the skin of nares. Pharyngeal and vestibular S. aureus carriage was determined in 20% of the examined adults, whereas in 11 people with recognized positive throat colonization, the concurrent presence of golden staph was detected in the vestibule of the nose and on the skin, in the nose region. Identification process indicated the occurrence of strains defective in clumping factor synthesis (5% of isolates) and lack of the coa gene (11% of examined isolates). The PCR technique used to screen for the presence of the mec gene, did not confirm it in any of the strains under study. All the isolates had the gene encoding the thermostable nuclease nuc.

CONCLUSIONS

S. aureus is a pervasive pathogen in community settings with constantly changing trends.

Skin-Associated B Cells in Health and Inflammation

Traditionally, the skin was believed to be devoid of B cells, and studies of the skin immune system have largely focused on other types of leukocytes. Exciting recent data show that B cells localize to the healthy skin of humans and other mammalian species with likely homeostatic functions in host defense, regulation of microbial communities, and wound healing. Distinct skin-associated B cell subsets drive or suppress cutaneous inflammatory responses with important clinical implications. Localized functions of skin-associated B cell subsets during inflammation comprise Ab production, interactions with skin T cells, tertiary lymphoid tissue formation, and production of proinflammatory cytokines but also include immunosuppression by providing IL-10. In this review, we delve into the intriguing new roles of skin-associated B cells in homeostasis and inflammation.

Intersection of HIV and community-associated methicillin-resistant Staphylococcus aureus

The epidemiology of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has evolved over the past approximately 20 years, with certain populations appearing to have disproportionate risk. Of concern is the potential worsening of S. aureus infections in light of the continued opioid crisis. This review will discuss how CA-MRSA has significantly impacted HIV-infected individuals and address additional factors and populations that are associated with increased risk for MRSA. It will review therapeutic options and infection control strategies as well as highlight how whole genome sequencing can be used to extend traditional epidemiologic analysis and ultimately, inform infection prevention efforts. Continued work identifying those at the highest risk for MRSA, what the best infection prevention settings are in community settings and how to effectively implement and target these strategies is needed. Ultimately, infection control efforts will likely need to extend beyond healthcare settings to effectively and sustainably reduce MRSA infections.

Genomic epidemiology of MRSA infection and colonization isolates among military trainees with skin and soft tissue infection

PURPOSE

Individuals with methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infection (SSTI) can be simultaneously colonized with MRSA on multiple body sites. Using whole genome sequencing (WGS), the intrahost relatedness of MRSA colonization and infection isolates was investigated.

METHODS

In the context of a prospective case-control study of SSTI, we analyzed colonization and infection isolates from US Army Infantry trainees with purulent infection due to MRSA. At the time of clinical presentation for SSTI, culture swabs were obtained from the infection site, as well as from the patient's nasal, oral, inguinal, and perianal regions. S. aureus culture and susceptibility was performed by standard methods. DNA from MRSA isolates was extracted and libraries were produced. Sequences were generated on an Illumina MiSeq, sequence reads were assembled, and single nucleotide variant (SNV) data were analyzed.

RESULTS

Of 74 trainees with MRSA SSTI, 19 (25.7%) were colonized with MRSA. Ten (52.6%) were colonized on more than one body site. Colonization frequency by anatomic site was as follows: inguinal region (33%), nasal region (30%), perianal region (22%), and oral region (14%). A total of 36 MRSA colonization isolates were characterized. The intrahost median number of SNVs between infection and colonization isolates was 17. Among trainees with recurrent MRSA SSTI, limited intrahost diversity suggests that persistent colonization is a major contributor to recurrence risk.

CONCLUSIONS

Among military trainees with MRSA SSTI, genomic characterization of infection and colonization isolates revealed a high degree of strain relatedness. Single acquisition events may account for MRSA colonization and infection in this population.

Finding of Agr Phase Variants in Staphylococcus aureus

Staphylococcus aureus is responsible for a broad range of infections. This pathogen has a vast arsenal of virulence factors at its disposal, but avirulent strains are frequently isolated as the cause of clinical infections. These isolates have a mutated agr locus and have been believed to have no evolutionary future. Here we show that a fraction of Agr-negative strains can repair their mutated agr locus with mechanisms resembling phase variation. The agr revertants sustain an Agr OFF state as long as they exist as a minority but can activate their Agr system upon phagocytosis. These revertant cells might function as a cryptic insurance strategy to survive immune-mediated host stress that arises during infection.

Staphylococcus aureus is an important human pathogen whose success is largely attributed to its vast arsenal of virulence factors that facilitate its invasion into, and survival within, the human host. The expression of these virulence factors is controlled by the quorum sensing accessory gene regulator (Agr) system. However, a large proportion of clinical S. aureus isolates are consistently found to have a mutationally inactivated Agr system. These mutants have a survival advantage in the host but are considered irreversible mutants. Here we show, for the first time, that a fraction of Agr-negative mutants can revert their Agr activity. By serially passaging Agr-negative strains and screening for phenotypic reversion of hemolysis and subsequent sequencing, we identified two mutational events responsible for reversion: a genetic duplication plus inversion event and a poly(A) tract alteration. Additionally, we demonstrate that one clinical Agr-negative methicillin-resistant S. aureus (MRSA) isolate could reproducibly generate Agr-revertant colonies with a poly(A) tract genetic mechanism. We also show that these revertants activate their Agr system upon phagocytosis. We propose a model in which a minor fraction of Agr-negative S. aureus strains are phase variants that can revert their Agr activity and may act as a cryptic insurance strategy against host-mediated stress.

The effect of preoperative oral antibiotic use on the risk of periprosthetic joint infection after primary knee or hip replacement: a retrospective study with a 1-year follow-up

OBJECTIVES

Antibiotics are used for various reasons before elective joint replacement surgery. The aim of this study was to investigate patients' use of oral antibiotics before joint replacement surgery and how this affects the risk for periprosthetic joint infection (PJI).

METHODS

Patients having a primary hip or knee replacement in a tertiary care hospital between September 2002 and December 2013 were identified (n = 23 171). Information on oral antibiotic courses purchased 90 days preoperatively and patients' chronic diseases was gathered. Patients with a PJI in a 1-year follow-up period were identified. The association between antibiotic use and PJI was examined using a multivariable logistic regression model and propensity score matching.

RESULTS

One hundred and fifty-eight (0.68%) cases of PJI were identified. In total, 4106 (18%) joint replacement operations were preceded by at least one course of antibiotics. The incidence of PJI for patients with preoperative use of oral antibiotics was 0.29% (12/4106), whereas for patients without antibiotic use it was 0.77% (146/19 065). A preoperative antibiotic course was associated with a reduced risk for subsequent PJI in the multivariable model (OR 0.40, 95% CI 0.22-0.73). Similar results were found in the propensity score matched material (OR 0.34, 95% CI 0.18-0.65).

CONCLUSIONS

The use of oral antibiotics before elective joint replacement surgery is common and has a potential effect on the subsequent risk for PJI. Nevertheless, indiscriminate use of antibiotics before elective joint replacement surgery cannot be recommended, even though treatment of active infections remains an important way to prevent surgical site infections.

Immune and Inflammatory Reponses to Staphylococcus aureus Skin Infections

Purpose of Review

There have been recent advances in our understanding of cutaneous immune responses to the important human skin pathogen, Staphylococcus aureus (S. aureus). This review will highlight these insights into innate and adaptive immune mechanisms in host defense and cutaneous inflammation in response to S. aureus skin infections.

Recent Findings

Antimicrobial peptides, pattern recognition receptors and inflammasome activation function in innate immunity as well as T cells and their effector cytokines play a key role in adaptive immunity against S. aureus skin infections. In addition, certain mechanisms by which S. aureus contributes to aberrant cutaneous inflammation, such as in flares of the inflammatory skin disease atopic dermatitis have also been identified.

Summary

These cutaneous immune mechanisms could provide new targets for future vaccines and immune-based therapies to combat skin infections and cutaneous inflammation caused by S. aureus.

The association between community-associated Staphylococcus aureus colonization and disease: a meta-analysis

Background

Colonization with Staphylococcus aureus is a well-defined risk factor for disease in hospitals, which can range from minor skin infections to severe, systemic diseases. However, the generalizability of this finding has not been thoroughly investigated outside of the hospital environment. We aimed to assess the role of S. aureus colonization as a risk factor for disease in the community.

Methods

We performed a meta-analysis of observational studies and searched PubMed for articles published between December 1979 and May 23, 2016. We included cohort, cross-sectional, and case-control studies that reported quantitative estimates of both S. aureus colonization and disease statuses of all study subjects. We excluded studies on recently hospitalized subjects, long-term care facilities, surgery patients, dialysis patients, hospital staff, S. aureus outbreaks, and livestock-associated infections. Our meta-analysis was performed using random-effects analysis to obtain pooled odds ratios (ORs) to compare the odds of S. aureus disease with respect to S. aureus colonization status.

Results

We identified 3477 citations, of which 12 articles on 6998 subjects met the eligibility criteria. Overall, subjects colonized with S. aureus were more likely to progress to disease than those who were non-colonized: (OR 1.87, 95% CI 1.21–2.88, n = 7 studies). We observed a larger effect with methicillin-resistant S. aureus colonization (7.06, 4.60–10.84, n = 7 studies). However, the methicillin-sensitive S. aureus colonization was not associated with greater odds of disease (1.20, 0.69–2.06, n = 4 studies). Heterogeneity was present across studies in all of the subgroups: S. aureus (I² = 95.0%, χ² = 120.3, p < 0.001), MRSA (I² = 92.8%, χ² = 82.8, p = p < 0.001), and MSSA (I² = 86.3%, χ² = 21.8, p < 0.001).

Conclusions

While the majority of papers individually support the assumption that colonization is a risk factor for S. aureus disease in the general population, there is marked heterogeneity between studies and further investigation is needed to identify the major sources of this variance. There is a shortage of literature addressing this topic in the community setting and a need for further research on colonization as a focus for disease prevention.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-2990-3) contains supplementary material, which is available to authorized users.

Antibacterial activity against Staphylococcus aureus of chitosan/chondroitin sulfate nanocomplex aerogels alone and enriched with erythromycin and elephant garlic (Allium ampeloprasum L. var. ampeloprasum) extract

The antibacterial activity against Staphylococcus aureus of aerogels fabricated from colloidal suspensions of chitosan/chondroitin sulfate nanocomplexes is analyzed. Upon freeze-drying the colloidal suspensions, the aerogels presented a porous structure made of microsheets and microfibers. The aerogels could, in addition, be loaded with antimicrobial agents. Loaded with the antibiotic erythromycin, the aerogels showed crystalline deposits, affecting the topography of the samples as well as their mechanical properties, showing a decrease on the apparent Young’s modulus and hardness at 40% deformation. Loaded with elephant garlic (Allium ampeloprasum L. var. ampeloprasum) extract, the aerogels showed texturization of the microsheets and microfibers, and the higher relative mass allowed an increase on the apparent Young’s modulus and hardness at 40% deformation with respect to pristine aerogels. Unloaded aerogels showed activity against Staphylococcus aureus, including a methicillin-resistant strain. The release of erythromycin from the aerogels to an agar environment is governed by equilibrium forces with the polysaccharides, which allow modulating the load of antibiotic and its concomitant diffusion from the material. The diffusion of the active components of the elephant garlic extract did not show a dependence on the polysaccharide content, revealing a week interaction. The elephant garlic extract resulted active against the methicillin-resistant Staphylococcus aureus strain, while resistance was found for the antibiotic, revealing the therapeutic potential of the natural extract. The antimicrobial aerogels may be used for several therapeutic purposes, such as healing of infected chronic wounds.

Severe infections emerge from commensal bacteria by adaptive evolution

Bacteria responsible for the greatest global mortality colonize the human microbiota far more frequently than they cause severe infections. Whether mutation and selection among commensal bacteria are associated with infection is unknown. We investigated de novo mutation in 1163 Staphylococcus aureus genomes from 105 infected patients with nose colonization. We report that 72% of infections emerged from the nose, with infecting and nose-colonizing bacteria showing parallel adaptive differences. We found 2.8-to-3.6-fold adaptive enrichments of protein-altering variants in genes responding to rsp, which regulates surface antigens and toxin production; agr, which regulates quorum-sensing, toxin production and abscess formation; and host-derived antimicrobial peptides. Adaptive mutations in pathogenesis-associated genes were 3.1-fold enriched in infecting but not nose-colonizing bacteria. None of these signatures were observed in healthy carriers nor at the species-level, suggesting infection-associated, short-term, within-host selection pressures. Our results show that signatures of spontaneous adaptive evolution are specifically associated with infection, raising new possibilities for diagnosis and treatment.

Postoperative deep shoulder infections following rotator cuff repair

Rotator cuff repair (RCR) is one of the most commonly performed surgical procedures in orthopaedic surgery. The reported incidence of deep soft-tissue infections after RCR ranges between 0.3% and 1.9%. Deep shoulder infection after RCR appears uncommon, but the actual incidence may be higher as many cases may go unreported. Clinical presentation may include increasing shoulder pain and stiffness, high temperature, local erythema, swelling, warmth, and fibrinous exudate. Generalized fatigue and signs of sepsis may be present in severe cases. Varying clinical presentation coupled with a low index of suspicion may result in delayed diagnosis. Laboratory findings include high erythrocyte sedimentation rate and C-reactive protein level, and, rarely, abnormal peripheral blood leucocyte count. Aspiration of glenohumeral joint synovial fluid with analysis of cell count, gram staining and culture should be performed in all patients suspected with deep shoulder infection after RCR. The most commonly isolated pathogens are Propionibacterium acnes, Staphylococcus epidermidis, and Staphylococcus aureus. Management of a deep soft-tissue infection of the shoulder after RCR involves surgical debridement with lavage and long-term intravenous antibiotic treatment based on the pathogen identified. Although deep shoulder infection after RCR is usually successfully treated, complications of this condition can be devastating. Prolonged course of intravenous antibiotic treatment, extensive soft-tissue destruction and adhesions may result in substantially diminished functional outcomes.

Epidemiology and clinical relevance of Staphylococcus aureus intestinal carriage: a systematic review and meta-analysis

Recent data highlight the importance of screening more than one site for improving the detection of S. aureus colonization. Intestinal carriage is frequently under-investigated and its clinical impact ought to be defined a better way. Areas covered: This review and meta-analysis provide an updated overview of prevalence, characteristics and clinical significance of S. aureus intestinal carriage in different populations, both for methicillin-susceptible and -resistant S. aureus strains. Expert commentary: Intestinal S. aureus carriage is documented with higher prevalence in children and in patients with S. aureus skin and soft tissue infections. This site of colonization was shown to be associated with a high risk of dissemination in the environment and with S. aureus infection. Intestinal carriage is frequently retrieved in nasal carriers, reflecting probably an association with a high bacterial load. Exclusive intestinal carriage present in one third of intestinal carriers can be associated with infection. Comparative genotyping analysis of different strains from nasal and extra-nasal sites of carriage, including the intestinal ones, in the same individuals, would allow a better comprehension of the pathophysiology of S. aureus endogenous infection. It could also permit to improve the prevention of these infections by decolonization of sites implicated in infection genesis.

A Cross-Sectional Study of Colonization Rates with Methicillin-Resistant Staphylococcus aureus (MRSA) and Extended-Spectrum Beta-Lactamase (ESBL) and Carbapenemase-Producing Enterobacteriaceae in Four Swiss Refugee Centres

BACKGROUND

The recent crisis of refugees seeking asylum in European countries challenges public health on many levels. Most refugees currently arrive from Syria, Afghanistan, or Eritrea. Data about multidrug resistant bacteria (MDR) prevalence are not present for these countries. However, when entering the European heath care systems, data about colonisation rates regarding highly resistant bacterial pathogens are important.

METHODS

We performed a cross-sectional screening in four Swiss refugee centres to determine the colonization rates for MRSA and ESBL- and carbapenemase-producing Enterobacteriaceae. We used pharyngeal, nasal, and inguinal swabs for MRSA and rectal swabs and urine for ESBL and carbapenemase screening using standard microbiological procedures. Whole genome sequencing (WGS) was used to determine the relatedness of MRSA isolates with high resolution due to a suspected outbreak.

RESULTS

41/261(15.7%) refugees were colonized with MRSA. No differences regarding the country of origin were observed. However, in a single centre significantly more were colonized, which was confirmed to be a recent local outbreak. 57/241 (23.7%) refugees were colonized with ESBL with significantly higher colonisation in persons originating from the Middle East (35.1%, p<0.001). No carbapenemase producers were detected.

CONCLUSION

The colonisation rate of the refugees was about 10 times higher for MRSA and 2-5 times higher for ESBL compared to the Swiss population. Contact precaution is warranted for these persons if they enter medical care. In cases of infections, MRSA and ESBL-producing Enterobacteriaceae should be considered regarding antibiotic treatment choices.

Staphylococcus epidermidis Protection Against Staphylococcus aureus Colonization in People Living With Human Immunodeficiency Virus in an Inner-City Outpatient Population: A Cross-Sectional Study

Background.

People living with human immunodeficiency virus (PLWH) have been disproportionally affected by methicillin-resistant Staphylococcus aureus (MRSA) colonization and infection, in particular by clones USA300 and USA500. However, the contribution of epidemiological, bacterial, and immunological risk factors to the excess of S aureus in PLWH remain incompletely understood.

Methods.

In this cross-sectional study, we determined the prevalence and molecular epidemiology of S aureus colonization in 93 PLWH attending an urban human immunodeficiency virus (HIV) clinic. Participants completed a structured interview assessing demographic information and risk factors for MRSA. Swabs were obtained from the nose, throat, and groin and cultured for S aureus and Staphylococcus epidermidis.

Results.

Most participants had well controlled HIV infection (89, 96% CD4 >200). Thirty-six (39%) individuals were colonized with S aureus at 1 or more body sites, including 6 (6%) with MRSA. Regular gym use was a risk factor for S aureus but not MRSA carriage. In contrast, S epidermidis was present in almost all individuals (n = 84, 90%), predominantly in the nares (n = 66, 71%). Using generalized estimating equation models, we observed that the odds of S aureus colonization were significantly and drastically reduced when S epidermidis was detected (P = .0001). After controlling for site, gender, and age, we identified that the odds of S aureus colonization were 80% less if S epidermidis was present (adjusted odds ratio, 0.20; 95% confidence interval, .09–.45; P < .0001).

Conclusions.

Taken together, we observed a lower prevalence of S aureus and MRSA colonization than has been previously reported in PLWH. In this cohort, colonization with S epidermidis was protective against S aureus colonization.

Livestock-Associated, Antibiotic-Resistant Staphylococcus aureus Nasal Carriage and Recent Skin and Soft Tissue Infection among Industrial Hog Operation Workers

Swine production work is a risk factor for nasal carriage of livestock-associated (LA-) Staphylococcus aureus and also for skin and soft tissue infection (SSTI). However, whether LA-S. aureus nasal carriage is associated with increased risk of SSTI remains unclear. We aimed to examine S. aureus nasal carriage and recent (≤3 months prior to enrollment) SSTI symptoms among industrial hog operation (IHO) workers and their household contacts. IHO workers and their household contacts provided a nasal swab and responded to a questionnaire assessing self-reported personal and occupational exposures and recent SSTI symptoms. Nasal swabs were analyzed for S. aureus, including methicillin-resistant S. aureus (MRSA), multidrug-resistant-S. aureus (MDRSA), absence of scn (livestock association), and spa type. S. aureus with at least one indicator of LA was observed among 19% of 103 IHO workers and 6% of 80 household members. Prevalence of recent SSTI was 6% among IHO workers and 11% among 54 minor household members (0/26 adult household members reported SSTI). Among IHO workers, nasal carriers of MDRSA and scn-negative S. aureus were 8.8 (95% CI: 1.8, 43.9) and 5.1 (95% CI: 1.2, 22.2) times as likely to report recent SSTI as non-carriers, respectively. In one household, both an IHO worker and child reported recent SSTI and carried the same S. aureus spa type (t4976) intranasally. Prevalence of scn-negative S. aureus (PR: 5.0, 95% CI: 1.2, 21.4) was elevated among IHO workers who reported never versus always wearing a face mask at work. Although few SSTI were reported, this study of IHO workers and their household contacts is the first to characterize a relation between nasal carriage of antibiotic-resistant LA-S. aureus and SSTI. The direction and temporality of this relation and IHO workers' use of face masks to prevent nasal carriage of these bacteria warrant further investigation.