Staphylococcus aureus skin infection recurrences among household members: an examination of host, behavioral, and pathogen-level predictors

α-Hemolysin from Staphylococcus aureus Changes the Epigenetic Landscape of Th17 Cells

The human body harbors a substantial population of bacteria, which may outnumber host cells. Thus, there are multiple interactions between both cell types. Given the common presence of Staphylococcus aureus in the human body and the role of Th17 cells in controlling this pathogen on mucous membranes, we sought to investigate the effect of α-hemolysin, which is produced by this bacterium, on differentiating Th17 cells. RNA sequencing analysis revealed that α-hemolysin influences the expression of signature genes for Th17 cells as well as genes involved in epigenetic regulation. We observed alterations in various histone marks and genome methylation levels via whole-genome bisulfite sequencing. Our findings underscore how bacterial proteins can significantly influence the transcriptome, epigenome, and phenotype of human Th17 cells, highlighting the intricate and complex nature of the interaction between immune cells and the microbiota.

Tissue resident cells differentiate S. aureus from S. epidermidis via IL-1β following barrier disruption in healthy human skin

The Staphylococcus sp. are a dominant part of the human skin microbiome and present across the body. Staphylococcus epidermidis is a ubiquitous skin commensal, while S. aureus is thought to colonize at least 30% of the population. S. aureus are not only colonizers but a leading cause of skin and soft tissue infections and a critical healthcare concern. To understand how healthy human skin may differentiate commensal bacteria, such as S. epidermidis, from the potential pathogen methicillin-resistant S. aureus (MRSA), we use ex vivo human skin models that allow us to study this host-bacterial interaction in the most clinically relevant environment. Our work highlights the role of the outer stratum corneum as a protective physical barrier against invasion by colonizing Staphylococci. We show how the structural cells of the skin can internalize and respond to different Staphylococci with increasing sensitivity. In intact human skin, a discriminatory IL-1β response was identified, while disruption of the protective stratum corneum triggered an increased and more diverse immune response. We identified and localized tissue resident Langerhans cells (LCs) as a potential source of IL-1β and go on to show a dose-dependent response of MUTZ-LCs to S. aureus but not S. epidermidis. This suggests an important role of LCs in sensing and discriminating between bacteria in healthy human skin, particularly in intact skin and provides a detailed snapshot of how human skin differentiates between friend and potential foe. With the rise in antibiotic resistance, understanding the innate immune response of healthy skin may help us find ways to enhance or manipulate these natural defenses to prevent invasive infection.

Multifunctional fucoidan-loaded Zn-MOF-encapsulated microneedles for MRSA-infected wound healing

Infected wound healing remains a challenging task in clinical practice due to several factors: (I) drug-resistant infections caused by various pathogens, (II) persistent inflammation that hinders tissue regeneration and (III) the ability of pathogens to persist intracellularly and evade antibiotic treatment. Microneedle patches (MNs), recognized for their effecacious and painless subcutaneous drug delivery, could greatly enhance wound healing if integrated with antibacterial functionality and tissue regenerative potential. A multifunctional agent with subcellular targeting capability and contained novel antibacterial components, upon loading onto MNs, could yield excellent therapeutic effects on wound infections. In this study, we sythesised a zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) loaded with low molecular weight fucoidan (Fu) and further coating by hyaluronic acid (HA), obtained a multifunctional HAZ@Fu NPs, which could hinders Methicillin-resistant Staphylococcus aureus (MRSA) growth and promotes M2 polarization in macrophages. We mixed HAZ@Fu NPs with photocrosslinked gelatin methacryloyl (GelMA) and loaded it into the tips of the MNs (HAZ@Fu MNs), administered to mice model with MRSA-infected full-thickness cutaneous wounds. MNs are able to penetrate the skin barrier, delivering HAZ@Fu NPs into the dermal layer. Since cells within infected tissues extensively express the HA receptor CD44, we also confirmed the HA endows the nanoparticles with the ability to target MRSA in subcellular level. In vitro and in vivo murine studies have demonstrated that MNs are capable of delivering HAZ@Fu NPs deep into the dermal layers. And facilitated by the HA coating, HAZ@Fu NPs could target MRSA surviving at the subcellular level. The effective components, such as zinc ions, Fu, and hyaluronic acid could sustainably released, which contributes to antibacterial activity, mitigates inflammation, promotes epithelial regeneration and fosters neovascularization. Through the RNA sequencing of macrophages post co-culture with HAZ@Fu, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis reveals that the biological functionalities associated with wound healing could potentially be facilitated through the PI3K-Akt pathway. The results indicate that the synergistic application of HAZ@Fu NPs with biodegradable MNs may serve as a significant adjunct in the treatment of infected wounds. The intricate mechanisms driving its biological effects merit further investigation.

Toxin-neutralizing Abs are associated with improved T cell function following recovery from Staphylococcus aureus infection

BACKGROUNDT cell responses are impaired in Staphylococcus aureus-infected children, highlighting a potential mechanism of immune evasion. This study tested the hypotheses that toxin-specific antibodies protect immune cells from bacterial killing and are associated with improved T cell function following infection.METHODSS. aureus-infected and healthy children (N = 33 each) were prospectively enrolled. During acute infection and convalescence, we quantified toxin-specific IgG levels by ELISA, antibody function using a cell killing assay, and functional T cell responses by ELISPOT.RESULTSThere were no differences in toxin-specific IgG levels or ability to neutralize toxin-mediated immune cell killing between healthy and acutely infected children, but antibody levels and function increased following infection. Similarly, T cell function, which was impaired during acute infection, improved following infection. However, the response to infection was highly variable; up to half of children did not have improved antibody or T cell function. Serum from children with higher α-hemolysin-specific IgG levels more strongly protected immune cells against toxin-mediated killing. Importantly, children whose serum more strongly protected against toxin-mediated killing also had stronger immune responses to infection, characterized by more elicited antibodies and greater improvement in T cell function following infection.CONCLUSIONThis study demonstrates that, despite T cell impairment during acute infection, S. aureus elicits toxin-neutralizing antibodies. Individual antibody responses and T cell recovery are variable. These findings also suggest that toxin-neutralizing antibodies protect antigen-presenting cells and T cells, thereby promoting immune recovery. Finally, failure to elicit toxin-neutralizing antibodies may identify children at risk for prolonged T cell suppression.FUNDINGNIH National Institute of Allergy and Infectious Diseases R01AI125489 and Nationwide Children's Hospital.

Trained immunity in recurrent Staphylococcus aureus infection promotes bacterial persistence

Bacterial persister cells, a sub-population of dormant phenotypic variants highly tolerant to antibiotics, present a significant challenge for infection control. Investigating the mechanisms of antibiotic persistence is crucial for developing effective treatment strategies. Here, we found a significant association between tolerance frequency and previous infection history in bovine mastitis. Previous S. aureus infection led to S. aureus tolerance to killing by rifampicin in subsequent infection in vivo and in vitro. Actually, the activation of trained immunity contributed to rifampicin persistence of S. aureus in secondary infection, where it reduced the effectiveness of antibiotic treatment and increased disease severity. Mechanically, we found that S. aureus persistence was mediated by the accumulation of fumarate provoked by trained immunity. Combination therapy with metformin and rifampicin promoted eradication of persisters and improved the severity of recurrent S. aureus infection. These findings provide mechanistic insight into the relationship between trained immunity and S. aureus persistence, while providing proof of concept that trained immunity is a therapeutic target in recurrent bacterial infections involving persistent pathogens.

Metabolism Shapes Immune Responses to Staphylococcus aureus

BACKGROUND

Staphylococcus aureus (S. aureus) is a common cause of hospital- and community-acquired infections that can result in various clinical manifestations ranging from mild to severe disease. The bacterium utilizes different combinations of virulence factors and biofilm formation to establish a successful infection, and the emergence of methicillin- and vancomycin-resistant strains introduces additional challenges for infection management and treatment.

SUMMARY

Metabolic programming of immune cells regulates the balance of energy requirements for activation and dictates pro- versus anti-inflammatory function. Recent investigations into metabolic adaptations of leukocytes and S. aureus during infection indicate that metabolic crosstalk plays a crucial role in pathogenesis. Furthermore, S. aureus can modify its metabolic profile to fit an array of niches for commensal or invasive growth.

KEY MESSAGES

Here we focus on the current understanding of immunometabolism during S. aureus infection and explore how metabolic crosstalk between the host and S. aureus influences disease outcome. We also discuss how key metabolic pathways influence leukocyte responses to other bacterial pathogens when information for S. aureus is not available. A better understanding of how S. aureus and leukocytes adapt their metabolic profiles in distinct tissue niches may reveal novel therapeutic targets to prevent or control invasive infections.

The Identification and Treatment of Common Skin Infections

Skin conditions are a common problem addressed by medical providers. Up to 25% of individuals in the United States will seek attention for these conditions each year. The same problem occurs in the athletic training room, where athletes with infectious skin conditions can be seen. Most conditions are simple and can be treated without concern for spread to susceptible athletes. However, others can be quite serious and spread rapidly through a team and opponents during competition. Knowledge of the different types of skin infections is necessary to help treat these athletes and prevent spread to others. With proper diagnosis and treatment, certified athletic trainers can keep the athlete off the field of play for a minimum period and prevent transmission.

A wound-friendly antibacterial hyaluronic acid dressing with on-demand removability for infected wound healing

BACKGROUND

Antibacterial activity and on-demand removability are key characteristics governing the effectiveness of clinic wound dressing. However, the excellent tissue adhesion of new dressings is often overemphasized without a detailed discussion of dressing replacement. Besides, the inherent antibacterial ability of dressings is beneficial for promoting the healing of infected wound. Therefore, we rationally design an injectable antibacterial wound dressing with on-demand removability to accelerate infected wound healing.

METHOD

We design this wound dressing with a simple and feasible method based on the electrostatic self-assembly of hyaluronic acid and ε-polylysine. We investigated the efficacy of this dressing in terms of its microtopography, rheology, self-healing performance, adhesive ability, antimicrobial, hemostatic, on-demand removal properties, and wound healing promotion through various tests.

RESULTS

The prepared dressing possesses injectability, self-healing ability and antibacterial activity, showing NaCl-triggered on-demand dissolution due to the disruption of electrostatic interactions. When used as dressings for healing full-thickness wounds, it could effectively accelerate wound healing by killing bacteria, downregulating inflammation, promoting collagen deposition, enhancing keratinocyte migration and angiogenesis due to its excellent adhesion ability, favorable hemostatic property, and potent antibacterial performance.

CONCLUSION

All results indicate that this is a simple and practical dressing for clinical application. This strategy provides a novel idea for developing on-demand removal dressings with antibacterial and injectable properties.

Toxin expression during Staphylococcus aureus infection imprints host immunity to inhibit vaccine efficacy

Staphylococcus aureus infections are a major public health issue, and a vaccine is urgently needed. Despite a considerable promise in preclinical models, all vaccines tested thus far have failed to protect humans against S. aureus. Unlike laboratory mice, humans are exposed to S. aureus throughout life. In the current study, we hypothesized that prior exposure to S. aureus "imprints" the immune response to inhibit vaccine-mediated protection. We established a mouse model in which S. aureus skin and soft tissue infection (SSTI) is followed by vaccination and secondary SSTI. Unlike naïve mice, S. aureus-sensitized mice were incompletely protected against secondary SSTI by vaccination with the inactivated α-hemolysin (Hla) mutant Hla_H35L. Inhibition of protection was specific for the Hla_H35L vaccine and required hla expression during primary SSTI. Surprisingly, inhibition occurred at the level of vaccine-elicited effector T cells; hla expression during primary infection limited the expansion of T cells and dendritic cells and impaired vaccine-specific T cell responses. Importantly, the T cell-stimulating adjuvant CAF01 rescued inhibition and restored vaccine-mediated protection. Together, these findings identify a potential mechanism for the failure of translation of promising S. aureus vaccines from mouse models to clinical practice and suggest a path forward to prevent these devastating infections.

Light-triggered theranostic hydrogels for real-time imaging and on-demand photodynamic therapy of skin abscesses

The management of wound infection remains the major challenges in real-time diagnosis, effective bacterial elimination and rapid wound healing. Herein, we developed injectable theranostic hydrogels to achieve long-term visual imaging of infected wounds and possible infection recurrence and to launch an on-demand bactericidal effect without using any antibiotics. Antimicrobial peptide ε-polylysine (ePL)-derived hydrogels were prepared through the copolymerization of methacrylated ePL (mPL) and the conjugates with tetrakis(4-carboxyphenyl) porphyrin (mPL-TCPP) and phenol red (mPL-Pr). Light illumination of mPL-TCPP produces reactive oxidative species (ROS) to initiate free radical crosslinking into PL@Pr-TCPP hydrogels without using any additional photoinitiators and concurrently exhibits antibacterial photodynamic therapy (PDT). PL@Pr-TCPP hydrogels experience quick color changes from yellow to orange and finally to red when pH values change from 5.0 to 9.0. The actual pH and related bacterial levels in the wounds could be read from G/B signal ratios of hydrogel colors captured by a smart phone. The conjugation of phenol red and TCPP into hydrogels affords a robust bacterial infection diagnosis and persistent bactericidal effect after cycled light illumination. The bacterial capture by ePL hydrogels strengthens PDT effect through alleviating the short lifetime and action distance of ROS. On a Staphylococcus aureus-infected abscess model, light illumination of the pregel solutions achieves in situ formation of hydrogel dressings. The synergistic bactericidal performance significantly relieves inflammatory status, accelerates collagen deposition, and promotes neovascularization, leading to full recovery of the infected wounds with regeneration of skin accessories. PL@Pr-TCPP hydrogels on the wound bed show color changes upon the recurrence of bacterial infection, which could also be totally eliminated after light illumination. Therefore, this study demonstrates a feasible strategy to develop theranostic hydrogel dressings for life-cycle diagnosis and on-demand treatment of wound infections. STATEMENT OF SIGNIFICANCE: Over 30% of skin and soft tissue infections become chronic even after appropriate antibacterial treatment, and recurrent infections are commonly reported after initial infection. Challenges remain in the development of theranostic wound dressings having the capability of point-of-care diagnosis, life-cycle monitoring and on-demand elimination of bacterial infection. Herein, light-triggered gelation is used to develop theranostic hydrogels for reversible naked-eye diagnosis and on-demand photodynamic therapy of wound infections. Light illumination plays a "one-stone-two-birds" role, i.e., photodynamically produced reactive oxidative species enable bactericidal effect without using any antibiotics, and the generated free radicals initiate crosslinking of hydrogels without using any additional photoinitiators. Bacterial infection-activated color changes of hydrogels could be captured with a smart phone for on-site and persistent monitoring of bacterial infection and wound healing process.

pH-Responsive non-antibiotic polymer prodrugs eradicate intracellular infection by killing bacteria and regulating immune response

Intracellular bacterial infections pose enormous challenges to food safety and public health. Antibiotic-based polymer prodrugs have been used to treat intracellular bacterial infection. However, the overuse of antibiotics may lead to the emergence of antibiotic resistance. In this work, we aimed to develop antibiotic-free pH-responsive polymeric prodrugs to combat intracellular S. aureus infection. Amphiphilic poly(ethylene glycol)-b-poly[(3-phenylprop-2-ene-1,1-diyl)bis(oxy)bis(enthane-2,1- diyl)diacrylate] (PEG-b-PCAE) was obtained by radical polymerization and they could self-assemble to form micelles. PEG-b-PCAE micelles could uptake by macrophage. Upon exposure to the acidic phagolysosome, PEG-b-PCAE micelles could release cinnamaldehyde (CA) through hydrolysis of the acetal linkage. PEG-b-PCAE could kill intracellular bacteria by damaging the bacterial membrane. Furthermore, PEG-b-PCAE micelles could generate reactive oxygen species (ROS) in macrophages and subsequently activate immune system to clear bacteria by inducing macrophages differentiation to M1 phenotype. PEG-b-PCAE micelles could accelerate the wound healing process of the S. aureus-infected model in vivo. It is anticipated that multifunctional antibiotic-free PEG-b-PCAE micelles with intrinsic antibacterial activities hold promise for improved outcomes in intracellular S. aureus infections.

Tissue specificity drives protective immunity against Staphylococcus aureus infection

Infections caused by Staphylococcus aureus range from mild to severe and frequently recur. Emerging evidence suggests that the site and severity of infection drive the potency of elicited immune responses and susceptibility to recurrent infection. In this study, we used tractable mouse models of S. aureus skin infection (SSTI) and pneumonia to determine the relative magnitude of elicited protective immunity. Surprisingly, despite both SSTI and pneumonia eliciting antibody and local effector T cell responses, only SSTI elicited protective antibody and memory T cell responses and subsequent protection against secondary SSTI and pneumonia. The failure of pneumonia to elicit protective immunity was attributed to an inability of S. aureus pneumonia to elicit toxin-specific antibodies that confer protection during secondary infection and was associated with a failure to expand antigen-specific memory T cells. Taken together, these findings emphasize the importance of understanding protective immunity in the context of the tissue-specificity.

Toward Optimization of a Rabbit Model of Staphylococcus aureus (USA300) Skin and Soft Tissue Infection

Staphylococcus aureus remains a leading cause of skin and soft tissue infections (SSTIs) globally. In the United States, many of these infections are caused by isolates classified as USA300. Our understanding of the success of USA300 as a human pathogen is due in part to data obtained from animal infection models, including rabbit SSTI models. These animal models have been used to study S. aureus virulence and pathogenesis and to gain an enhanced understanding of the host response to infection. Although significant knowledge has been gained, the need to use a relatively high inoculum of USA300 (1 × 108 to 5 × 108 CFU) is a caveat of these infection models. As a step toward addressing this issue, we created mutations in USA300 that mimic those found in S. aureus strains with naturally occurring rabbit tropism-namely, single nucleotide polymorphisms in dltB and/or deletion of rot. We then developed a rabbit SSTI model that utilizes an inoculum of 106 USA300 CFU to cause reproducible disease and tested whether primary SSTI protects rabbits against severe reinfection caused by the same strain. Although there was modest protection against severe reinfection, primary infection and reinfection with rabbit-tropic USA300 strains failed to increase the overall level of circulating anti-S. aureus antibodies significantly. These findings provide additional insight into the host response to S. aureus. More work is needed to further develop a low-inoculum infection model that can be used to better test the potential of new therapeutics or vaccine target antigens. IMPORTANCE Animal models of S. aureus infection are important for evaluating bacterial pathogenesis and host immune responses. These animal infection models are often used as an initial step in the testing of vaccine antigens and new therapeutics. The extent to which animal models of S. aureus infection approximate human infections remains a significant consideration for translation of results to human clinical trials. Although significant progress has been made with rabbit models of S. aureus infection, one concern is the high inoculum needed to cause reproducible disease. Here, we generated USA300 strains that have tropism for rabbits and developed a rabbit SSTI model that uses fewer CFU than previous models.

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.

Antibiotic Treatment of Staphylococcus aureus Infection Inhibits the Development of Protective Immunity

Recurrent Staphylococcus aureus infections are common, suggesting a failure to elicit protective immunity. Given the emergence of antibiotic resistance, a vaccine is urgently needed, but there is no approved vaccine for S. aureus. While antibiotics are routinely used to treat S. aureus infections, their impact on the development of protective immunity is not understood. Using an established mouse model of S. aureus skin and soft tissue infection (SSTI), we observed that antibiotic therapy effectively resolved infection but failed to elicit protection against secondary (2°) SSTI. Key contributors to protective immunity, toxin-specific antibodies and interleukin-17A (IL-17A)-producing T cells, were not strongly elicited in antibiotic-treated mice. Delaying antibiotic treatment failed to resolve skin lesions but resulted in higher antibody levels after infection and strong protection against 2° SSTI, suggesting that the development of protective immunity requires a longer period of antigen exposure. We next investigated if combining α-hemolysin (Hla) vaccination with antibiotics during primary infection would both treat infection and generate durable protective immunity. This "therapeutic vaccination" approach resulted in rapid resolution of primary infection and protection against recurrent infection, demonstrating that concurrent vaccination could circumvent the deleterious effects of antibiotic therapy on elicited immune responses. Collectively, these findings suggest that protective immunity is thwarted by the rapid elimination of antigen during antibiotic treatment. However, vaccination in conjunction with antibiotic treatment can retain the benefits of antibiotic treatment while also establishing protective immunity.

Effect of topical antimicrobial therapy and household cleaning on meticillin-resistant Staphylococcus pseudintermedius carriage in dogs

BACKGROUND

Meticillin-resistant Staphylococcus pseudintermedius (MRSP) is a multidrug-resistant canine pathogen with a low zoonotic potential. This study investigated MRSP carriage and clearance through topical antimicrobial therapy and household cleaning in dogs recovered from MRSP infection.

METHODS

Dogs were swabbed for MRSP carriage; household contamination was assessed using contact plates. Carrier dogs were allocated randomly to receive topical fusidic acid and chlorhexidine/miconazole treatment combined with owners implementing a household hygiene protocol (H&T) or implementation of hygiene alone (H) over three weeks. Carriage-negative dogs were monitored monthly. The relatedness of isolates over time was investigated by pulsed-field gel electrophoresis (PFGE).

RESULTS

At inclusion, MRSP carriage was confirmed in 31/46 (67.4%) index dogs and 16/24 (66.7%) contact dogs, and contamination was found in 18/40 (45%) environments. In dogs completing all cycles, interventions cleared carriage in 5/9 (55.6%) dogs in group H&T and 2/6 (33.3%) in group H. Environmental contamination was infrequent but associated with carrier dogs (p = 0.047). Monthly monitoring of initially negative dogs showed intermittent carriage in 9/14 dogs. PFGE-concordance was found among all 34 MRSP isolated from eight index dogs over time.

CONCLUSION

MRSP carriage was common in dogs after recovery from infection. Topical antimicrobial therapy temporarily eliminated carriage but recurrence was frequent. Management efforts must include the prevention of recurrent infections and hygiene.

Staphylococcus aureus Vaccine Research and Development: The Past, Present and Future, Including Novel Therapeutic Strategies

Staphylococcus aureus is one of the most important human pathogens worldwide. Its high antibiotic resistance profile reinforces the need for new interventions like vaccines in addition to new antibiotics. Vaccine development efforts against S. aureus have failed so far however, the findings from these human clinical and non-clinical studies provide potential insight for such failures. Currently, research is focusing on identifying novel vaccine formulations able to elicit potent humoral and cellular immune responses. Translational science studies are attempting to discover correlates of protection using animal models as well as in vitro and ex vivo models assessing efficacy of vaccine candidates. Several new vaccine candidates are being tested in human clinical trials in a variety of target populations. In addition to vaccines, bacteriophages, monoclonal antibodies, centyrins and new classes of antibiotics are being developed. Some of these have been tested in humans with encouraging results. The complexity of the diseases and the range of the target populations affected by this pathogen will require a multipronged approach using different interventions, which will be discussed in this review.

Household Transmission of Community-Associated Methicillin-Resistant Staphylococcus Aureus

Currently, the mechanism of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) transmission mechanism is unclear; however, it must be considered in conjunction with asymptomatic S. aureus strains colonization dynamics. This epidemiological study aimed to determine the role of the household in CA-MRSA transmission in China. Five patients with culture-confirmed CA-MRSA infection and five control patients were recruited from the Sir Run Run Shaw Hospital in Zhejiang, China, between December 2019 and January 2020. The household members of the patients, their pets, and environmental surfaces were sampled and screened for MRSA colonization. Mass spectrometry identification and antimicrobial susceptibility testing were performed on the MRSA isolates. Whole-genome sequencing and core genome multilocus sequence typing (cgMLST) were performed to determine the origin and transmission of the MRSA isolates in the households. Overall, 14 S. aureus-positive specimens (14.1%, 14/99) were obtained from the five households of patients with CA-MRSA infections, of which 12 (85.7%) were MRSA. The overall positivity of MRSA was 12.1% (12/99) among the samples from the CA-MRSA households, while no MRSA isolates were detected in the five control households. Most MRSA isolates belonged to epidemic CA-MRSA clones, such as ST59 (15/35, 42.9%) and ST508 (15/35, 42.9%). The cgMLST results confirmed that MRSA was transmitted among patients, contacts, and pets in the households and was present on environmental surfaces in the CA-MRSA patients' households. In conclusion, the study revealed that the home environment was an important MRSA reservoir. Therefore, focusing on MRSA decolonization in patients alone is not sufficient for infection control of CA-MRSA.

Diversity of Functionally Distinct Clonal Sets of Human Conventional Memory B Cells That Bind Staphylococcal Protein A

Staphylococcus aureus, a common cause of serious and often fatal infections, is well-armed with secreted factors that disarm host immune defenses. Highly expressed in vivo during infection, Staphylococcal protein A (SpA) is reported to also contribute to nasal colonization that can be a prelude to invasive infection. Co-evolution with the host immune system has provided SpA with an Fc-antibody binding site, and a Fab-binding site responsible for non-immune superantigen interactions via germline-encoded surfaces expressed on many human BCRs. We wondered whether the recurrent exposures to S. aureus commonly experienced by adults, result in the accumulation of memory B-cell responses to other determinants on SpA. We therefore isolated SpA-specific class-switched memory B cells, and characterized their encoding VH : VL antibody genes. In SpA-reactive memory B cells, we confirmed a striking bias in usage for VH genes, which retain the surface that mediates the SpA-superantigen interaction. We postulate these interactions reflect co-evolution of the host immune system and SpA, which during infection results in immune recruitment of an extraordinarily high prevalence of B cells in the repertoire that subverts the augmentation of protective defenses. Herein, we provide the first evidence that human memory responses are supplemented by B-cell clones, and circulating-antibodies, that bind to SpA determinants independent of the non-immune Fc- and Fab-binding sites. In parallel, we demonstrate that healthy individuals, and patients recovering from S. aureus infection, both have circulating antibodies with these conventional binding specificities. These findings rationalize the potential utility of incorporating specially engineered SpA proteins into a protective vaccine.

Complicated skin and soft tissue infections in remote indigenous communities

The burden and consequences of skin infections for remote living indigenous people are high. While skin infections are recognised as an antecedent to conditions such as acute rheumatic fever in children, data are limited concerning skin infection complications such as cellulitis, abscesses and osteomyelitis in older children and adults. In a 1-year retrospective audit of 439 patients presenting to two remote health clinics, 330/439 (75%) patients presented with a skin infection and 18 (4%) developed a complication.

Distribution and drug resistance of pathogens in burn patients in China from 2006 to 2019

BACKGROUND

In this study, recent trends in the distribution and drug resistance of pathogenic bacteria isolated from patients treated at a burn ward between 2006 and 2019 were investigated.

AIM

To develop more effective clinical strategies and techniques for the prevention and treatment of bacterial infections in burn patients.

METHODS

Clinical samples with positive bacteria were collected from patients at the burn ward in Beijing Jishuitan Hospital in China between January 2006 and December 2019. The samples were retrospectively analyzed, the distribution of pathogenic bacteria was determined, and the trends and changes in bacterial drug resistance during different period were assessed. Drug resistance in several main pathogenic bacteria from 2006 to 2011 and from 2012 to 2019 was comparatively summarized and analyzed.

RESULTS

Samples from 17119 patients were collected and analyzed from 2006 to 2019. Surprisingly, a total of 7960 strains of different pathogenic bacteria were isolated at this hospital. Among these bacteria, 87.98% (7003/7960) of the strains were isolated from burn wounds, and only 1.34% (107/7960) were isolated from the blood of patients. In addition, 49.70% (3956/7960) were identified as Gram-positive bacteria, 48.13% (3831/7960) were Gram-negative bacteria, and the remaining 2.17% (173/7960) were classified as fungi or other pathogens. Importantly, Staphylococcus aureus (21.68%), Pseudomonas aeruginosa (14.23%), and Staphylococcus epidermidis (9.61%) were the top three pathogens most frequently isolated from patients.

CONCLUSION

In patients treated at the burn ward in this hospital from 2006 to 2019, Staphylococcus aureus and Pseudomonas aeruginosa were the predominant clinical pathogens responsible for bacterial infections. The circumstantial detection and detailed monitoring of the intensity and growth of different pathogenic bacteria in clinical patients as well as tests of drug sensitivity during burn recovery are particularly important to provide guidelines for the application of antibiotics and other related drugs. Careful collection and correct, standard culture of bacterial specimens are also crucial to improve the efficiency of bacterial infection detection. Effective monitoring and timely clinical treatment in patients may help reduce the possibility and rate of infection as well as alleviate the effects of drug resistance among patients in burn centers.

IBT-V02: A Multicomponent Toxoid Vaccine Protects Against Primary and Secondary Skin Infections Caused by Staphylococcus aureus

Staphylococcus aureus causes a wide range of diseases from skin infections to life threatening invasive diseases such as bacteremia, endocarditis, pneumonia, surgical site infections, and osteomyelitis. Skin infections such as furuncles, carbuncles, folliculitis, erysipelas, and cellulitis constitute a large majority of infections caused by S. aureus (SA). These infections cause significant morbidity, healthcare costs, and represent a breeding ground for antimicrobial resistance. Furthermore, skin infection with SA is a major risk factor for invasive disease. Here we describe the pre-clinical efficacy of a multicomponent toxoid vaccine (IBT-V02) for prevention of S. aureus acute skin infections and recurrence. IBT-V02 targets six SA toxins including the pore-forming toxins alpha hemolysin (Hla), Panton-Valentine leukocidin (PVL), leukocidin AB (LukAB), and the superantigens toxic shock syndrome toxin-1 and staphylococcal enterotoxins A and B. Immunization of mice and rabbits with IBT-V02 generated antibodies with strong neutralizing activity against toxins included in the vaccine, as well as cross-neutralizing activity against multiple related toxins, and protected against skin infections by several clinically relevant SA strains of USA100, USA300, and USA1000 clones. Efficacy of the vaccine was also shown in non-naïve mice pre-exposed to S. aureus. Furthermore, vaccination with IBT-V02 not only protected mice from a primary infection but also demonstrated lasting efficacy against a secondary infection, while prior challenge with the bacteria alone was unable to protect against recurrence. Serum transfer studies in a primary infection model showed that antibodies are primarily responsible for the protective response.

Evasion of Immunological Memory by S. aureus Infection: Implications for Vaccine Design

Recurrent S. aureus infections are common, suggesting that natural immune responses are not protective. All candidate vaccines tested thus far have failed to protect against S. aureus infections, highlighting an urgent need to better understand the mechanisms by which the bacterium interacts with the host immune system to evade or prevent protective immunity. Although there is evidence in murine models that both cellular and humoral immune responses are important for protection against S. aureus, human studies suggest that T cells are critical in determining susceptibility to infection. This review will use an “anatomic” approach to systematically outline the steps necessary in generating a T cell-mediated immune response against S. aureus. Through the processes of bacterial uptake by antigen presenting cells, processing and presentation of antigens to T cells, and differentiation and proliferation of memory and effector T cell subsets, the ability of S. aureus to evade or inhibit each step of the T-cell mediated response will be reviewed. We hypothesize that these interactions result in the redirection of immune responses away from protective antigens, thereby precluding the establishment of “natural” memory and potentially inhibiting the efficacy of vaccination. It is anticipated that this approach will reveal important implications for future design of vaccines to prevent these infections.

Targeting Skin-Resident Memory T Cells via Vaccination to Combat Staphylococcus aureus Infections

Tissue-resident memory T cells are important in adaptive immunity against many infections, rendering these cells attractive potential targets in vaccine development. Genetic and experimental evidence highlights the importance of cellular immunity in protection from Staphylococcus aureus skin infections, yet skin-resident memory T cells are, thus far, an untested component of immunity during such infections. Novel methods of generating and sampling vaccine-induced skin memory T cells are paralleled by discoveries of global, skin-wide immunosurveillance. We propose skin-resident memory CD4⁺ T cells as a potential missing link in the search for correlates of protection during S. aureus infections. A better appreciation of their phenotypes and functions could accelerate the development of preventive vaccines against this highly virulent and antibiotic-resistant pathogen.

Staphylococcus aureus Skin and Soft Tissue Infection Recurrence Rates in Outpatients: A Retrospective Database Study at 3 US Medical Centers

Background

Staphylococcusaureus skin and soft tissue infections (SA-SSTIs) are common in healthcare and community settings, and recurrences occur at variable frequency, even after successful initial treatment. Knowing the exact burden and timing of recurrent disease is critical to planning and evaluating interventions to prevent recurrent SSTIs.

Methods

In this retrospective study, SSTI cases in patients aged ≥18 years at 3 US medical centers (Columbia, Chicago, Vanderbilt) between 2006 and 2016 were analyzed according to a biennial cohort design. Index SSTIs (with or without key comorbidities), either microbiologically confirmed to be SA-SSTI or not microbiologically tested (NMT-SSTI), were recorded within 1 calendar year and followed up for 12 months for recurrent infections. The number of index cases, proportion of index cases with ≥1 recurrence(s), time to first recurrence, and number of recurrences were collected for both SA-SSTI and NMT-SSTI events.

Results

In the most recent cohorts, 4755 SSTI cases were reported at Columbia, 2873 at Chicago, and 6433 at Vanderbilt. Of these, 452, 153, and 354 cases were confirmed to be due to S. aureus. Most cases were reported in patients without key comorbidities. Across centers, 16.4%–19.0% (SA-SSTI) and 11.0%–19.2% (NMT-SSTI) of index cases had ≥1 recurrence(s). In patients without key comorbidities, more than 60% of index SSTIs with recurrences had only 1 recurrence, half of which occurred in the first 3 months following primary infection.

Conclusions

SA-SSTI recurrences are common among healthy adults and occur in at least 1 in 6 individuals during the 1 year following the primary event.

Staphylococcus aureus toxin suppresses antigen-specific T cell responses

Staphylococcus aureus remains a leading cause of human infection. These infections frequently recur when the skin is a primary site of infection, especially in infants and children. In contrast, invasive staphylococcal disease is less commonly associated with reinfection, suggesting that tissue-specific mechanisms govern the development of immunity. Knowledge of how S. aureus manipulates protective immunity has been hampered by a lack of antigen-specific models to interrogate the T cell response. Using a chicken egg OVA-expressing S. aureus strain to analyze OVA-specific T cell responses, we demonstrated that primary skin infection was associated with impaired development of T cell memory. Conversely, invasive infection induced antigen-specific memory and protected against reinfection. This defect in adaptive immunity following skin infection was associated with a loss of DCs, attributable to S. aureus α-toxin (Hla) expression. Gene- and immunization-based approaches to protect against Hla during skin infection restored the T cell response. Within the human population, exposure to α-toxin through skin infection may modulate the establishment of T cell-mediated immunity, adversely affecting long-term protection. These studies prompt consideration that vaccination targeting S. aureus may be most effective if delivered prior to initial contact with the organism.

Bactericidal In Vitro Activity of a Tissue-Achievable Concentration of Cefazolin against Methicillin-Resistant Staphylococcus aureus

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of skin and soft tissue infections and their recurrences. Although traditionally not considered for use against MRSA, cefazolin presents a possible option when administered using ultrasonic drug dispersion (UD2). This novel technique localizes delivery of drug into the subcutaneous tissue and achieves concentrations that exceed the minimum inhibitory concentrations (MICs) of most clinical MRSA isolates. The purpose of this study was to evaluate the impact of achievable cefazolin concentrations on the rate and extent of bactericidal activity using time-kill methodologies Materials and Methods: The cefazolin MICs of the four MRSA isolates selected for this in vitro time-kill study were 64, 128, 256, and 512 mg/L. Duplicates of drug-free control and cefazolin experiments were carried out using the average UD2-achievable cefazolin concentration (1,300 mg/L). Experiments were incubated at 37°C throughout each run. Samples were plated and incubated for 18 to 24 hours. The lower limit of detection of colony forming units per milliliter (CFU/mL) was 1.7 log₁₀ CFU/mL. Cefazolin was considered bactericidal when it decreased bacterial density by ≥3 log₁₀ CFU/mL from the initial inoculum after 24 hours of incubation. Results: Cefazolin produced mean 24-hour CFU changes of -4.39 to -4.89 log₁₀ CFU/mL against MRSA isolates with MICs from 64 to 512 mg/L. Cefazolin demonstrated bactericidal activity against all studied MRSA isolates and no regrowth was observed at 24 hours. Conclusions: The mean cefazolin tissue concentration achieved by UD2 was bactericidal against four MRSA isolates. Further investigation is warranted to assess the utility of UD2-administered cefazolin against MRSA skin and soft tissue infections.

Biodistribution and intracellular localization of hyaluronan and its nanogels. A strategy to target intracellular S. aureus in persistent skin infections

Intracellular pathogens are a critical challenge for antimicrobial therapies. Staphylococcus aureus (S. aureus) causes approximately 85% of all skin and soft tissue infections in humans worldwide and more than 30% of patients develop chronic or recurrent infections within three months, even after appropriate antibacterial therapies. S. aureus is also one of the most common bacteria found in chronic wounds. Recent evidences suggest that S. aureus is able to persist within phagolysosomes of skin cells (i.e. keratinocytes, phagocytic cells), being protected from both the immune system and a number of antimicrobials. To overcome these limits, nano-formulations that enable targeted therapies against intracellular S. aureus might be developed. Herein, the biodistribution and intracellular localisation of hyaluronan (HA) and HA-based nanoparticles (nanogels, NHs) are investigated, both after intravenous (i.v.) injections (in mice) and topical administrations (in ex vivo human skin). Results indicate HA and NHs accumulate especially in skin and liver of mice after i.v. injection. After topical application on human skin explants, no penetration of both HA and NHs was detected in skin with intact stratum corneum. By contrast, in barrier-disrupted human skin (with partial removal and loosening of stratum corneum), HA and NHs penetrate to the viable epidermis and are taken up by keratinocytes. In mechanically produced wounds (skin without epidermis) they accumulate in wound tissue and are taken up by dermis cells, e.g. fibroblasts and phagocytic cells. Interestingly, in all cases, the cellular uptake is CD44-mediated. In vitro studies confirmed that after CD44-mediated uptake, both HA and NHs accumulate in lysosomes of dermal fibroblasts and macrophages, as previously reported for keratinocytes. Finally, the colocalisation between intracellular S. aureus and HA or NHs is demonstrated, in macrophages. Altogether, for the first time, these results strongly suggest that HA and HA-based NHs can provide a targeted therapy to intracellular S. aureus, in persistent skin or wound infections.

HOME2: Household vs. Personalized Decolonization in Households of Children with Methicillin-Resistant Staphylococcus aureus Skin and Soft Tissue Infection - A Randomized Clinical Trial

BACKGROUND

A household approach to decolonization decreases skin and soft tissue infection (SSTI) incidence, though this is burdensome and costly. As prior SSTI increases risk for SSTI, we hypothesized the effectiveness of decolonization measures to prevent SSTI when targeted to household members with prior year SSTI would be non-inferior to decolonizing all household members.

METHODS

Upon completion of our 12-month observational HOME study, 102 households were enrolled in HOME2, a 12-month, randomized non-inferiority trial. Pediatric index patients with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) SSTI, their household contacts, and pets were enrolled. Households were randomized 1:1 to the Personalized (decolonization performed only by household members who experienced SSTI during the HOME study) or Household (decolonization performed by all household members) approaches. The 5-day regimen included hygiene education, twice-daily intranasal mupirocin, and daily bleach-water baths. At 5 follow-up visits in participants' homes, swabs to detect S. aureus were collected from participants, environmental surfaces, and pets; incident SSTI were ascertained.

RESULTS

Non-inferiority of the Personalized Approach was established for the primary outcome 3-month cumulative SSTI: 23 of 212 (10.8%) participants reported SSTI in Household Approach households, while 23 of 236 (9.7%) participants reported SSTI in Personalized Approach households; difference in proportions -1.1% (95% CI -6.7%, 4.5%). In multivariable analyses, prior year SSTI and baseline MRSA colonization were associated with cumulative SSTI.

CONCLUSIONS

The Personalized Approach was non-inferior to the Household Approach in preventing SSTI. Future studies should interrogate longer durations of decolonization and/or decontamination of the household environment to reduce household MRSA burden.

Environmental Methicillin-resistant Staphylococcus aureus Contamination, Persistent Colonization, and Subsequent Skin and Soft Tissue Infection

IMPORTANCE

The longitudinal association among persistent Staphylococcus aureus colonization, household environmental contamination, and recurrent skin and soft tissue infection (SSTI) is largely unexplored to date.

OBJECTIVES

To identify factors associated with persistent S aureus colonization and recurrent SSTI in households with children with community-associated methicillin-resistant S aureus (MRSA) SSTI.

DESIGN, SETTING, AND PARTICIPANTS

This 12-month prospective cohort study included 150 children with community-associated MRSA SSTI, 542 household contacts, and 154 pets enrolled from January 3, 2012, through October 20, 2015. A total of 5 quarterly home visits were made to 150 households in the St Louis, Missouri, region. Statistical analysis was performed from September 18, 2018, to January 7, 2020.

EXPOSURES

Covariates used in S aureus strain persistence and interval SSTI models included S aureus colonization and contamination measures, personal hygiene and sharing habits, health history, activities external to the home, and household characteristics (eg, cleanliness, crowding, home ownership, and pets). Serial samples to detect S aureus were collected from household members at 3 anatomic sites, from pets at 2 anatomic sites, and from environmental surfaces at 21 sites.

MAIN OUTCOMES AND MEASURES

Molecular epidemiologic findings of S aureus isolates were assessed via repetitive-sequence polymerase chain reaction. Individual persistent colonization was defined as colonization by an identical strain for 2 consecutive samplings. Longitudinal, multivariable generalized mixed-effects logistic regression models were used to assess factors associated with persistent S aureus personal colonization, environmental contamination, and interval SSTI.

RESULTS

Among 692 household members in 150 households, 326 (47%) were male and 366 (53%) were female, with a median age of 14.82 years (range, 0.05-82.25 years). Of 540 participants completing all 5 samplings, 213 (39%) were persistently colonized with S aureus, most often in the nares and with the strain infecting the index patient at enrollment. Nine pets (8%) were persistently colonized with S aureus. Participants reporting interval intranasal mupirocin application were less likely to experience persistent colonization (odds ratio [OR], 0.44; 95% credible interval [CrI], 0.30-0.66), whereas increasing strain-specific environmental contamination pressure was associated with increased individual persistent colonization (OR, 1.17; 95% CrI, 1.06-1.30). Strains with higher colonization pressure (OR, 1.47; 95% CrI, 1.25-1.71) and MRSA strains (OR, 1.57; 95% CrI, 1.16-2.19) were more likely to persist. Seventy-six index patients (53%) and 101 household contacts (19%) reported interval SSTIs. Individuals persistently colonized with MRSA (OR, 1.56; 95% CrI, 1.17-2.11), those with a history of SSTI (OR, 2.55; 95% CrI, 1.88-3.47), and index patients (OR, 1.54; 95% CrI, 1.07-2.23) were more likely to report an interval SSTI.

CONCLUSIONS AND RELEVANCE

The study findings suggest that recurrent SSTI is associated with persistent MRSA colonization of household members and contamination of environmental surfaces. Future studies may elucidate the effectiveness of specific combinations of personal decolonization and environmental decontamination efforts in eradicating persistent strains and mitigating recurrent SSTIs.

Inhibition of protective immunity against Staphylococcus aureus infection by MHC-restricted immunodominance is overcome by vaccination

Recurrent Staphylococcus aureus infections are common, despite robust immune responses. S. aureus infection elicited protective antibody and T cell responses in mice that expressed the Major Histocompatibility Complex (MHC) of the H-2^d haplotype, but not H-2^b, demonstrating that host genetics drives individual variability. Vaccination with a-toxin or leukotoxin E (LukE) elicited similar antibody and T cell responses in mice expressing H-2^d or H-2^b, but vaccine-elicited responses were inhibited by concomitant infection in H-2^d-expressing mice. These findings suggested that competitive binding of microbial peptides to host MHC proteins determines the specificity of the immunodominant response, which was confirmed using LukE-derived peptide-MHC tetramers. A vaccine that elicited T cell and antibody responses protected mice that expressed H-2^d or H-2^b, demonstrating that vaccination can overcome MHC-restricted immunodominance. Together, these results define how host genetics determine whether immunity elicted by S. aureus is protective and provide a mechanistic roadmap for future vaccine design.

Longitudinal, strain-specific Staphylococcus aureus introduction and transmission events in households of children with community-associated meticillin-resistant S aureus skin and soft tissue infection: a prospective cohort study

BACKGROUND

Devising effective, targeted approaches to prevent recurrent meticillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infection requires an understanding of factors driving MRSA acquisition. We comprehensively defined household longitudinal, strain-level S aureus transmission dynamics in households of children with community-associated MRSA skin and soft tissue infection.

METHODS

From 2012-15, otherwise healthy paediatric patients with culture-confirmed, community-onset MRSA infections were recruited for the Household Observation of MRSA in the Environment (HOME) prospective cohort study from hospitals and community practices in metropolitan St Louis (MO, USA). Children with health-care-related risk factors were excluded, as determined by evidence of recent hospital admission, an invasive medical device, or residence in a long-term care facility. Household contacts (individuals sleeping in the home ≥four nights per week) and indoor dogs and cats were also enrolled. A baseline visit took place at the index patient's primary home, followed by four quarterly visits over 12 months. At each visit, interviews were done and serial cultures were collected, to detect S aureus from three anatomic sites of household members, two anatomic sites on dogs and cats, and 21 environmental surfaces. Molecular typing was done by repetitive-sequence PCR to define distinct S aureus strains within each household. Longitudinal, multivariable generalised mixed-effects logistic regression models identified factors associated with S aureus acquisition.

FINDINGS

Across household members, pets, and environmental surfaces, 1267 strain acquisition events were observed. Acquisitions were driven equally by 510 introductions of novel strains into households and 602 transmissions within households, each associated with distinct factors. Frequent handwashing decreased the likelihood of novel strain introduction into the household (odds ratio [OR] 0·86, credible interval [CrI] 0·74-1·01). Transmission recipients were less likely to own their homes (OR 0·77, CrI 0·63-0·94) and were more likely to share bedrooms with strain-colonised individuals (OR 1·33, CrI 1·12-1·58), live in homes with higher environmental S aureus contamination burden (OR 3·97, CrI 1·96-8·20), and report interval skin and soft tissue infection (OR 1·32, CrI 1·07-1·64). Transmission sources were more likely to share bath towels (OR 1·25, CrI 1·01-1·57). Pets were often transmission recipients, but rarely the sole transmission source.

INTERPRETATION

The household environment plays a key role in transmission, a factor associated with skin and soft tissue infection. Future interventions should inclusively target household members and the environment, focusing on straightforward changes in hand hygiene and household sharing behaviours.

FUNDING

National Institutes of Health, Agency for Healthcare Research and Quality, Children's Discovery Institute, Burroughs Wellcome Foundation, Defense Advanced Research Projects Agency.

Staphylococcus aureus Internalized by Skin Keratinocytes Evade Antibiotic Killing

Staphylococcus aureus causes the majority of skin and soft tissue infections. Half of patients treated for primary skin infections suffer recurrences within 6 months despite appropriate antibiotic sensitivities and infection control measures. We investigated whether S. aureus internalized by human skin keratinocytes are effectively eradicated by standard anti-staphylococcal antibiotics. S. aureus, but not S. epidermidis, were internalized and survive within keratinocytes without inducing cytotoxicity or releasing the IL-33 danger signal. Except for rifampicin, anti-staphylococcal antibiotics in regular clinical use, including flucloxacillin, teicoplanin, clindamycin, and linezolid, did not kill internalized S. aureus, even at 20-fold their standard minimal inhibitory concentration. We conclude that internalization of S. aureus by human skin keratinocytes allows the bacteria to evade killing by most anti-staphylococcal antibiotics. Antimicrobial strategies, including antibiotic combinations better able to penetrate into mammalian cells are required if intracellular S. aureus are to be effectively eradicated and recurrent infections prevented.

Trends in resistant Enterobacteriaceae and Acinetobacter species in hospitalized patients in the United States: 2013-2017

BACKGROUND

Trends in antimicrobial resistance help inform infection control efforts. We examined trends in resistance for Enterobacteriaceae and Acinetobacter spp. from 2013 to 2017 in hospitalized US patients.

METHODS

We analyzed antimicrobial susceptibility of non-duplicate isolates in hospitalized patients (not limited to hospital-acquired infections) in the US BD Insights Research Database. Resistance profiles of interest were extended-spectrum beta-lactamase (ESBL)-producing, multidrug resistant (MDR), and carbapenem-nonsusceptible (Carb-NS) phenotypes of Enterobacteriaceae, and MDR and Carb-NS Acinetobacter spp. Time series models were used to evaluate the patterns of resistance trends in rate per 100 hospital admissions and proportion per isolates tested.

RESULTS

More than 1 million Enterobacteriaceae isolates were obtained from 411 hospitals; 12.05% were ESBL, 1.21% Carb-NS, and 7.08% MDR. Urine was the most common source. For Acinetobacter spp. (n = 19,325), 37.48% were Carb-NS, 47.66% were MDR, and the most common source was skin/wound cultures. Trend analyses showed that the rates of ESBL and Carb-NS Enterobacteriaceae per 100 hospital admissions increased significantly between 2013 and 2017. Rates of MDR Enterobacteriaceae and Carb-NS and MDR Acinetobacter spp. decreased during this time period. Trends in proportions of resistant isolates generally mirrored trends in rates per 100 hospital admissions. MDR Enterobacteriaceae and Carb-NS and MDR Acinetobacter spp. were more common in winter than summer.

CONCLUSIONS

In this large-scale study of patients in US hospitals, rates of ESBL and Carb-NS Enterobacteriaceae per 100 hospital admissions increased between 2013 and 2017. MDR Enterobacteriaceae and MDR and Carb-NS Acinetobacter spp. isolates decreased over this period. These data support continuing infection control and stewardship efforts and the development of new therapeutic options.

Dirty Money on Holy Ground: Isolation of Potentially Pathogenic Bacteria and Fungi on Money Collected from Church Offerings

BACKGROUND

Fomites (including money) can transmit diseases to humans. How the nature of money influences contamination has not been adequately demonstrated. Moreover, such studies in church settings are non-existent. Thus, we studied how money collected from a church could serve as human disease transmission vehicles.

METHODS

Overall, 284 money samples (currency notes and coins) were collected during two Sundays in the months of Nov and Dec 2015 from a church congregation in Pretoria, Gauteng, South Africa. The presence of potentially pathogenic bacteria and fungi were investigated using culture (Colilert^® method) and molecular methods (Sanger sequencing). Scanning Electron Microscopy (SEM) was used to visualize the possible positions of the bacteria on various parts of a currency note.

RESULTS

Of the 192 samples (first sampling round), 76 (39.6%) were positive for E. coli. Smaller notes (R10) recorded the highest E. coli counts per note. Of the 92 notes analyzed for potentially pathogenic bacteria and fungi (second sampling round), 76 (82%) showed growth on at least one of the six culture media used. Sequencing revealed three bacterial (Bacillus, Staphylococcus and Corynebacterium) and two fungal (Clavispora and Rhodotorula) genera. SEM revealed that microorganisms could enter cracks of creased notes.

CONCLUSION

Unlike previous studies conducted where recent contamination could occur, the current study shows that microorganisms can survive on money; samples were collected from a church, where little or no exchange takes place. Moreover, using SEM demonstrates that aged and creased notes favor attachment of bacteria to money and could be of public health concern by transmitting disease within a given population.

Prevention Strategies for Recurrent Community-Associated Staphylococcus aureus Skin and Soft Tissue Infections

PURPOSE OF REVIEW

Staphylococcus aureus skin and soft tissue infections (SSTI) are a major source of morbidity. More than half of patients experiencing SSTI will have at least one recurrent infection. These infections frequently cluster in households. Given the burden these infections pose to patients and healthcare, prevention strategies are of major clinical importance and represent an active area of research. Bacterial colonization is frequently an early and critical step in the pathogenesis of infection. As such, strategies to prevent reinfection have aimed to decrease staphylococcal colonization of the skin and mucus membranes, a process referred to as decolonization.

RECENT FINDINGS

Treatment of acute SSTI with incision and drainage and systemic antibiotics is the mainstay of therapy for healing of the acute infection. Systemic antibiotics also provide benefit through reduced incidence of recurrent SSTI. Education for patients and families regarding optimization of personal and household hygiene measures, and avoidance of sharing personal hygiene items, is an essential component in prevention efforts. For patients experiencing recurrent SSTI, or in households in which multiple members have experienced SSTI, decolonization should be recommended for all household members. A recommended decolonization regimen includes application of intranasal mupirocin and antiseptic body washes with chlorhexidine or dilute bleach water baths. For patients who continue to experience recurrent SSTI, periodic decolonization should be considered. Personal decolonization with topical antimicrobials and antiseptics reduces the incidence of recurrent S. aureus SSTI. Future avenues for investigation include strategies for household environmental decontamination as well as manipulation of the host microbiota.

Characterizing the molecular epidemiology of Staphylococcus aureus across and within fitness facility types

BACKGROUND

Staphylococcus aureus is a common bacterium found in the nose and throat of healthy individuals, and presents risk factors for infection and death. We investigated environmental contamination of fitness facilities with S. aureus in order to determine molecular types and antibiotic susceptibility profiles of contaminates that may be transmitted to facility patrons.

METHODS

Environmental swabs (n = 288) were obtained from several fitness facilities (n = 16) across Northeast Ohio including cross-fit type facilities (n = 4), traditional iron gyms (n = 4), community center-based facilities (n = 5), and hospital-associated facilities (n = 3). Samples were taken from 18 different surfaces at each facility and were processed within 24 h using typical bacteriological methods. Positive isolates were subjected to antibiotic susceptibility testing and molecular characterization (PVL and mecA PCR, and spa typing).

RESULTS

The overall prevalence of S. aureus on environmental surfaces in the fitness facilities was 38.2% (110/288). The most commonly colonized surfaces were the weight ball (62.5%), cable driven curl bar, and CrossFit box (62.5%), as well as the weight plates (56.3%) and treadmill handle (50%). Interestingly, the bathroom levers and door handles were the least contaminated surfaces in both male and female restroom facilities (18.8%). Community gyms (40.0%) had the highest contamination prevalence among sampled surfaces with CrossFit (38.9%), traditional gyms (38.9%), and hospital associated (33.3%) contaminated less frequently, though the differences were not significant (p = 0.875). The top spa types found overall were t008 (12.7%), t267 (10.0%), t160, t282, t338 (all at 5.5%), t012 and t442 (4.5%), and t002 (3.6%). t008 and t002 was found in all fitness facility types accept Crossfit, with t267 (25%), t548, t377, t189 (all 10.7%) the top spa types found within crossfit. All samples were resistant to benzylpenicillin, with community centers having significantly more strains resistant to oxacillin (52.8%), erythromycin (47%), clindamycin (36%), and ciprofloxacin (19%). Overall, 36.3% of isolates were multidrug resistant.

CONCLUSIONS

Our pilot study indicates that all facility types were contaminated by S. aureus and MRSA, and that additional studies are needed to characterize the microbiome structure of surfaces at different fitness facility types and the patrons at these facilities.

Interplay of personal, pet, and environmental colonization in households affected by community-associated methicillin-resistant Staphylococcus aureus

OBJECTIVE

We sought to determine the prevalence, molecular epidemiology, and factors associated with Staphylococcus aureus environmental surface and pet colonization in households of children with community-associated methicillin-resistant S. aureus (CA-MRSA) infection.

METHODS

Between 2012 and 2015, 150 children with CA-MRSA infections and their household contacts and pets were enrolled in this cross-sectional study in metropolitan Saint Louis, MO. Cultures to detect S. aureus were collected from 3 anatomic sites of household members, 2 dog/cat sites, and 21 environmental surfaces in each household. Molecular epidemiology of S. aureus isolates was determined via repetitive-sequence PCR. Generalized linear models were developed to identify factors associated with S. aureus/MRSA household contamination.

RESULTS

MRSA was recovered from environmental surfaces in 69 (46%) households (median 2 surfaces [range 1-18]). The enrollment infecting strain type was the most common strain recovered from the environment in most (64%) households. In generalized linear models, factors associated with a higher proportion of MRSA-contaminated environmental surfaces were household member MRSA colonization burden, MRSA as the dominant S. aureus strain colonizing household members, more strain types per household member, index case African-American race, and renting (vs. owning) the home. Of 132 pets, 14% were colonized with MRSA. Pets whose primary caretaker was MRSA-colonized were more likely to be MRSA-colonized than pets whose primary caretaker was not MRSA-colonized (50% vs. 4%, p < 0.001).

CONCLUSIONS

Household environments and pet dogs and cats serve as reservoirs of MRSA. Household member MRSA colonization burden predicts environmental MRSA contamination. Longitudinal studies will inform the directionality of household transmission.

Infectious Disease in Contact Sports

CONTEXT:

Infections are common in contact sports. This review aims to describe the epidemiology, presenting signs and symptoms, treatment guidelines, and regulations for several common infections seen in contact sport athletes. The conditions discussed include bacterial skin infections, herpes simplex virus, molluscum contagiosum, common warts, tinea, scabies, head lice, conjunctivitis, human immunodeficiency virus, hepatitis C virus, and vaccine-preventable illnesses.

EVIDENCE ACQUISITION:

Searches were performed across PubMed and MEDLINE research databases. In addition, general internet search engine results and reviews of reference lists of relevant papers were used to identify additional sources of evidence.

STUDY DESIGN:

Clinical review.

LEVEL OF EVIDENCE:

Level 4.

RESULTS:

The most common infections seen in contact sport athletes include bacterial skin infections, herpes simplex virus, molluscum contagiosum, common warts, tinea, scabies, head lice, conjunctivitis, and vaccine-preventable illnesses. Other infections, including human immunodeficiency virus and hepatitis C, are uncommon but potentially life threatening.

CONCLUSION:

Infections are common in contact sport athletes. The provider who cares for these athletes should be aware of the most common infections and their appropriate management. Early diagnosis and appropriate clinical management are important for treating the infected athlete, minimizing risk of transmission, minimizing time lost from competition, and preventing large outbreaks.

Human Memory B Cells Targeting Staphylococcus aureus Exotoxins Are Prevalent with Skin and Soft Tissue Infection

Staphylococcus aureus is a Gram-positive opportunistic pathogen that causes superficial and invasive infections in the hospital and community. High mortality from infection emphasizes the need for improved methods for prevention and treatment. Although S. aureus possesses an arsenal of virulence factors that contribute to evasion of host defenses, few studies have examined long-term humoral and B-cell responses. Adults with acute-phase skin and soft tissue infections were recruited; blood samples were obtained; and S. aureus isolates, including methicillin-resistant strains, were subjected to genomic sequence analysis. In comparisons of acute-phase sera with convalescent-phase sera, a minority (37.5%) of patients displayed 2-fold or greater increases in antibody titers against three or more S. aureus antigens, whereas nearly half exhibited no changes, despite the presence of toxin genes in most infecting strains. Moreover, enhanced antibody responses waned over time, which could reflect a defect in B-cell memory or long-lived plasma cells. However, memory B cells reactive with a range of S. aureus antigens were prevalent at both acute-phase and convalescent-phase time points. While some memory B cells exhibited toxin-specific binding, those cross-reactive with structurally related leucocidin subunits were dominant across patients, suggesting the targeting of conserved epitopes. Memory B-cell reactivity correlated with serum antibody levels for selected S. aureus exotoxins, suggesting a relationship between the cellular and humoral compartments. Overall, although there was no global defect in the representation of anti-S. aureus memory B cells, there was evidence of restrictions in the range of epitopes recognized, which may suggest potential therapeutic approaches for augmenting host defenses.

The contribution of B-cell memory and long-term antibody responses to host defenses against S. aureus exotoxins remains poorly understood. Our studies confirmed that infection did not commonly lead to enhanced long-term humoral responses. Whereas circulating memory B cells against S. aureus secreted exotoxins were prevalent, they were dominated by cross-reactivity with structurally related leucocidin subunits, consistent with recognition of conserved epitopes. These findings also provide the first evidence of a relationship between the reactivity of antistaphylococcal circulating memory B cells and serum antibody levels. In general, infection was not associated with a global defect in B-cell memory for S. aureus secreted factors, and responses were highly dominated by cross-reactivity to structurally related exotoxins, which arguably may alone be suboptimal in providing host defenses. Our studies illuminate aspects of the S. aureus-host relationship that may better inform strategies for the development of an effective protective vaccine.

Impact of Systemic Antibiotics on Staphylococcus aureus Colonization and Recurrent Skin Infection

Background

Staphylococcus aureus colonization poses risk for subsequent skin and soft tissue infection (SSTI). We hypothesized that including systemic antibiotics in the management of S. aureus SSTI, in conjunction with incision and drainage, would reduce S. aureus colonization and incidence of recurrent infection.

Methods

We prospectively evaluated 383 children with S. aureus SSTI requiring incision and drainage and S. aureus colonization in the anterior nares, axillae, or inguinal folds at baseline screening. Systemic antibiotic prescribing at the point of care was recorded. Repeat colonization sampling was performed within 3 months (median, 38 days; interquartile range, 22-50 days) in 357 participants. Incidence of recurrent infection was ascertained for up to 1 year.

Results

Participants prescribed guideline-recommended empiric antibiotics for purulent SSTI were less likely to remain colonized at follow-up sampling (adjusted hazard ratio [aHR], 0.49; 95% confidence interval [CI], .30-.79) and less likely to have recurrent SSTI (aHR, 0.57; 95% CI, .34-.94) than those not receiving guideline-recommended empiric antibiotics for their SSTI. Additionally, participants remaining colonized at repeat sampling were more likely to report a recurrent infection over 12 months (aHR, 2.37; 95% CI, 1.69-3.31). Clindamycin was more effective than trimethoprim-sulfamethoxazole (TMP-SMX) in eradicating S. aureus colonization (44% vs 57% remained colonized, P = .03) and preventing recurrent SSTI (31% vs 47% experienced recurrence, P = .008).

Conclusions

Systemic antibiotics, as part of acute SSTI management, impact S. aureus colonization, contributing to a decreased incidence of recurrent SSTI. The mechanism by which clindamycin differentially affects colonization and recurrent SSTI compared to TMP-SMX warrants further study.

Staphylococcus aureus strategies to evade the host acquired immune response

Staphylococcus aureus poses a significant public-health problem. Infection caused by S. aureus can manifest as acute or long-lasting persistent diseases that are often refractory to antibiotic and are associated with significant morbidity and mortality. To develop more effective strategies for preventing or treating these infections, it is crucial to understand why the immune response is incapable to eradicate the bacterium. When S. aureus first infect the host, there is a robust activation of the host innate immune responses. Generally, S. aureus can survive this initial interaction due to the expression of a wide array of virulence factors that interfere with the host innate immune defenses. After this initial interaction the acquired immune response is the arm of the host defenses that will try to clear the pathogen. However, S. aureus is capable of maintaining infection in the host even in the presence of a robust antigen-specific immune response. Thus, understanding the mechanisms underlying the ability of S. aureus to escape immune surveillance by the acquired immune response will help uncover potentially important targets for the development of immune-based adjunctive therapies and more efficient vaccines. There are several lines of evidence that lead us to believe that S. aureus can directly or indirectly disable the acquired immune response. This review will discuss the different immune evasion strategies used by S. aureus to modulate the different components of the acquired immune defenses.

Incidence and factors associated with emergency department visits for recurrent skin and soft tissue infections in patients in California, 2005-2011

More than 2 million visits for skin and soft tissue infections (SSTIs) are seen in US emergency departments (EDs) yearly. Up to 50% of patients with SSTIs, suffer from recurrences, but associated factors remain poorly understood. We performed a retrospective study of patients with primary diagnosis of SSTI between 2005 and 2011 using California ED discharge data from the State Emergency Department Databases and State Inpatient Databases. Using a multivariable logistic regression, we examined factors associated with a repeat SSTI ED visits up to 6 months after the initial SSTI. Among 197 371 SSTIs, 16·3% were associated with a recurrent ED visit. We found no trend in recurrent visits over time (χ 2 trend = 0·68, P = 0·4). Race/ethnicity, age, geographical location, household income, and comorbidities were all associated with recurrent visits. Recurrent ED visits were associated with drug/alcohol abuse or liver disease [odds ratio (OR) 1·4, 95% confidence interval (CI) 1·3-1·4], obesity (OR 1·3, 95% CI 1·2-1·4), and in infections that were drained (OR 1·1, 95% CI 1·1-1·1) and inversely associated with hospitalization after initial ED visit (OR 0·4, 95% CI 0·3-0·4). In conclusion, we found several patient-level factors associated with recurrent ED visits. Identification of these high-risk groups is critical for future ED-based interventions.

Efficient Production of Gene-Modified Mice using Staphylococcus aureus Cas9

The CRISPR/Cas system is an efficient genome-editing tool to modify genes in mouse zygotes. However, only the Streptococcus pyogenes Cas9 (SpCas9) has been systematically tested for generating gene-modified mice. The protospacer adjacent motif (PAM, 5'-NGG-3') recognized by SpCas9 limits the number of potential target sites for this system. Staphylococcus aureus Cas9 (SaCas9), with its smaller size and unique PAM (5'-NNGRRT-3') preferences, presents an alternative for genome editing in zygotes. Here, we showed that SaCas9 could efficiently and specifically edit the X-linked gene Slx2 and the autosomal gene Zp1 in mouse zygotes. SaCas9-mediated disruption of the tyrosinase (Tyr) gene led to C57BL/6J mice with mosaic coat color. Furthermore, multiplex targeting proved efficient multiple genes disruption when we co-injected gRNAs targeting Slx2, Zp1, and Tyr together with SaCas9 mRNA. We were also able to insert a Flag tag at the C-terminus of histone H1c, when a Flag-encoding single-stranded DNA oligo was co-introduced into mouse zygotes with SaCas9 mRNA and the gRNA. These results indicate that SaCas9 can specifically cleave the target gene locus, leading to successful gene knock-out and precise knock-in in mouse zygotes, and highlight the potential of using SaCas9 for genome editing in preimplantation embryos and producing gene-modified animal models.

Prevention of Recurrent Staphylococcal Skin Infections

Staphylococcus aureus infections pose a significant health burden. The emergence of community-associated methicillin-resistant S aureus has resulted in an epidemic of skin and soft tissue infections (SSTI), and many patients experience recurrent SSTI. As S aureus colonization is associated with subsequent infection, decolonization is recommended for patients with recurrent SSTI or in settings of ongoing transmission. S aureus infections often cluster within households, and asymptomatic carriers serve as reservoirs for transmission; therefore, a household approach to decolonization is more effective than measures performed by individuals alone. Novel strategies for the prevention of recurrent SSTI are needed.

Optimizing antimicrobial therapy in children

Management of common infections and optimal use of antimicrobial agents are presented, highlighting new evidence from the medical literature that enlightens practice. Primary therapy of staphylococcal skin abscesses is drainage. Patients who have a large abscess (>5 cm), cellulitis or mixed abscess-cellulitis likely would benefit from additional antibiotic therapy. When choosing an antibiotic for outpatient management, the patient, pathogen and in vitro drug susceptibility as well as tolerability, bioavailability and safety characteristics of antibiotics should be considered. Management of recurrent staphylococcal skin and soft tissue infections is vexing. Focus is best placed on reducing density of the organism on the patient's skin and in the environment, and optimizing a healthy skin barrier. With attention to adherence and optimal dosing, acute uncomplicated osteomyelitis can be managed with early transition from parenteral to oral therapy and with a 3-4 week total course of therapy. Doxycycline should be prescribed when indicated for a child of any age. Its use is not associated with dental staining. Azithromycin should be prescribed for infants when indicated, whilst being alert to an associated ≥2-fold excess risk of pyloric stenosis with use under 6 weeks of age. Beyond the neonatal period, acyclovir is more safely dosed by body surface area (not to exceed 500 mg/m(2)/dose) than by weight. In addition to the concern of antimicrobial resistance, unnecessary use of antibiotics should be avoided because of potential later metabolic effects, thought to be due to perturbation of the host's microbiome.

Association of Environmental Contamination in the Home With the Risk for Recurrent Community-Associated, Methicillin-Resistant Staphylococcus aureus Infection

IMPORTANCE

The role of environmental contamination in recurrent Staphylococcus aureus infections within households and its potential effect on intervention strategies has been debated recently.

OBJECTIVE

To assess whether household environmental contamination increases the risk for recurrent infection among individuals with a community-associated methicillin-resistant S aureus (MRSA) infection.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted from November 1, 2011, to June 30, 2014, in the Columbia University Medical Center catchment area. All patients within 72 hours of presentation with skin or soft-tissue infections and blood, urine, or sputum cultures positive for MRSA were identified. Two hundred sixty-two patients met study inclusion criteria; 83 of these (31.7%) agreed to participate (index patients) with 214 household members. Participants were followed up for 6 months, and 62 of the 83 households (74.7%) completed follow-up. Participants and researchers were blinded to exposure status throughout the study. Follow-up was completed on June 30, 2014, and data were assessed from July 1, 2014, to February 19, 2016.

EXPOSURE

Concordant environmental contamination, defined as having an isolate with the identical staphylococcal protein A and staphylococcal chromosomal cassette mec type or antibiogram type as the index patient's clinical isolate, present on 1 or more environmental surfaces at the time of a home visit to the index patient after infection.

MAIN OUTCOMES AND MEASURES

Index recurrent infection, defined as any self-reported infection among the index patients during follow-up.

RESULTS

One patient did not complete any follow-up. Of the remaining 82 index patients, 53 (64.6%) were female and 59 (72.0%) were Hispanic. The mean age was 30 (SD, 20; range, 1-79) years. Forty-nine of 61 MRSA infections where the clinical isolate could be obtained (80.3%) were due to the epidemic strain USA300. Among the 82 households in which a patient had an index MRSA infection, the clinical isolate was present in the environment in 20 (24.4%) and not found in 62 (75.6%). Thirty-five patients (42.7%) reported a recurrent infection during follow-up, of whom 15 (42.9%) required hospitalization. Thirteen recurrent infections were from the 20 households (65.0%) with and 22 were from the 62 households (35.5%) without environmental contamination (P = .04). Environmental contamination increased the rate of index recurrent infection (incident rate ratio, 2.05; 95% CI, 1.03-4.10; P = .04).

CONCLUSIONS AND RELEVANCE

Household environmental contamination was associated with an increased rate of recurrent infection. Environmental decontamination should be considered as a strategy to prevent future MRSA infections, particularly among households where an infection has occurred.

Relationship between Adherence to Oral Antibiotics and Postdischarge Clinical Outcomes among Patients Hospitalized with Staphylococcus aureus Skin Infections

Skin and soft tissue infections are common and frequently recur. Poor adherence to antibiotic therapy may lead to suboptimal clinical outcomes. However, adherence to oral antibiotic therapy for skin and soft tissue infections and its relationship to clinical outcomes have not been examined. We enrolled adult patients hospitalized with uncomplicated skin and soft tissue infections caused by Staphylococcus aureus who were being discharged with oral antibiotics to complete therapy. We fit the participants' pill bottles with an electronic bottle cap that recorded each pill bottle opening, administered an in-person standardized questionnaire at enrollment, 14 days, and 30 days, and reviewed the participants' medical records to determine outcomes. Our primary outcome was poor clinical response, defined as a change in antibiotic therapy, new incision-and-drainage procedure, or new skin infection within 30 days of hospital discharge. Of our 188 participants, 87 had complete data available for analysis. Among these participants, 40 (46%) had a poor clinical response at 30 days. The mean electronically measured adherence to antibiotic therapy was significantly different than the self-reported adherence (57% versus 96%; P < 0.0001). In a multivariable model, poor clinical response at 30 days was associated with patients having lower adherence, being nondiabetic, and reporting a lack of illicit drug use within the previous 12 months (P < 0.05). In conclusion, we found that patient adherence to oral antibiotic therapy for a skin and soft tissue infection after hospital discharge was low (57%) and associated with poor clinical outcome. Patients commonly overstate their medication adherence, which may make identification of patients at risk for nonadherence and poor outcomes challenging. Further studies are needed to improve postdischarge antibiotic adherence after skin and soft tissue infections.