Recurrent skin and soft tissue infections due to methicillin-resistant Staphylococcus aureus requiring operative debridement

The Incidence of Skin and Soft Tissue Infections in the United States and Associated Healthcare Utilization Between 2010 and 2020

Background

The number of patients with skin and soft tissue infections (SSTIs) in the United States appeared to be increasing well into the 21st century. However, no recent data have confirmed this trend.

Methods

This retrospective, observational cohort study used claims data over 11 years (2010-2020) from Optum's de-identified Clinformatics Data Mart Database. SSTI episodes, complications, and comorbidities were identified using International Classification of Diseases codes. Annual SSTI incidence rates, proportions of recurrent SSTI, SSTI-associated deaths, and total costs were estimated.

Results

During the study period, 5.4 million patients experienced 9.1 million SSTI episodes, with an incidence of 77.5 (95% confidence interval, 77.4-77.5) per 1000 person-years of observation (PYO). Annual incidence did not change significantly over time. Overall incidence (per 1000 PYO) of SSTI episodes in patients without comorbidities was 32.1 (highest incidence was for previous SSTI [113.5]) versus much higher rates if comorbidities were present. Incidence rates (per 1000 PYO) of chronic ulcers increased over time from 11.3 to 18.2 (P < .0001) and complicated disease from 3.5 to 6.3 (P < .0001). Deaths occurring within 30 days post-SSTI hospitalization rose from 2.6% to 4.6% in 2020. Recurrences occurred in 26.3% of index cases. The mean cost of an SSTI episode was US$3334 (median US$190) and was highest for surgical site infections and chronic ulcers.

Conclusions

The epidemiology of SSTI in the United States is changing and the disease burden is increasing despite stabilization in overall incidence. These data can inform identification of priority populations who could benefit from targeted interventions.

Risk factors for infection in patients undergoing shoulder arthroscopy: A Systematic Review and Meta-analysis

PURPOSE

We conducted a meta-analysis to determine the risk of infection following shoulder arthroscopy and to identify risk factors for infection.

METHODS

We systematically searched the PubMed/Medline, Embase and Cochrane Library databases, as well as the reference lists of previous systematic reviews and meta-analyses; manual searches were also performed. A random-effects model was employed to estimate pooled ORs, based on sample size, the p value of Egger's test and heterogeneity among studies.

RESULTS

Of the 29,342 articles screened, 16 retrospective studies comprising 74,759 patients were included. High-quality evidence showed that patients with diabetes (OR, 1.30; 95% CI, 1.20-1.41) or hypertension (OR, 1.26;95% CI, 1.10-1.44) had a higher risk of infection, while moderate quality evidence showed that patients with obesity (BMI ≥30 kg/m2) (OR, 1.42;95% CI, 1.28-1.57), those who were male (OR, 1.65;95% CI, 1.12-2.44), those who had an ASA class ≥3 (OR, 2.02;95% CI,1.02-3.99) and those who had a history of smoking (OR, 2.44;95% CI, 1.39-4.28) had a higher risk of infection. The meta-analysis revealed that there was no association between age, time of surgery, or alcohol consumption and infection.

CONCLUSIONS

This meta-analysis identified six significant risk factors for infection following shoulder arthroscopy, including diabetes, obesity, hypertension, male sex, ASA class, history of smoking. These patient-related risk factors may help identify postoperative patients at higher risk for infection following shoulder arthroscopy.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and Level IV studies.

TRIAL REGISTRATION NUMBER

The review protocol was registered in PROSPERO. Unique Identifying Number (UIN) is "CRD42023463316".

Facial Physiological Characteristics and Skin Microbiomes Changes are Associated with Body Mass Index (BMI)

Background

Overweight and obesity have become public health problems worldwide. An increasing number of research works are focusing on skin physiology and the manifestations of obesity-associated skin diseases, but little is known about the correlations between body mass index (BMI), facial skin physiological parameters, and the facial skin microbiome in healthy women.

Objective

To investigate the correlations between BMI, facial skin physiological parameters and facial bacteria and fungi in 198 women aged 18 to 35 years in Shanghai.

Methods

According to the international BMI standard and Chinese reference standard, subjects were divided into three groups, "lean" B1, "normal" B2 and "overweight" B3, and the physiological parameters of facial skin were measured by non-invasive instrumental methods, and the skin microbiota was analyzed by 16S rRNA and ITS high-throughput sequencing.

Results

Compared with the skin physiological parameters of the normal group, those of the overweight group exhibited a significant increase in trans-epidermal water loss (TEWL), which indicated that the skin barrier was impaired. The skin haemoglobin content was significantly increased, and skin surface pH was significant decreased in those with a high BMI. Furthermore, α-diversity, analysed using the Shannon, Chao, Sobs, and Ace indexes, was increased in the overweight group, suggesting that the diversity and species abundance of facial bacterial and fungal microbiota were also increased. Moreover, the overweight group had higher abundances of Streptococcus, Corynebacterium, Malassezia, and Candida. Notably, skin surface pH was significantly and negatively correlated with the relative abundances of Malassezia, Candida, and Cladosporium. Besides, the abundance of Malassezia was positively associated with the abundances of Staphylococcus and Corynebacterium.

Conclusion

These results indicate that BMI is associated with differences in the biophysical properties and microbiome of the facial skin. A high BMI affects the integrity of skin barrier and changes the skin flora diversity and species composition.

Repurposing antibiotic resistance surveillance data to support treatment of recurrent infections in a remote setting

In northern Australia, a region with limited access to healthcare and a substantial population living remotely, antibiotic resistance adds to the complexity of treating infections. Focussing on Escherichia coli urinary tract infections (UTIs) and Staphylococcus aureus skin & soft tissue infections (SSTIs) captured by a northern Australian antibiotic resistance surveillance system, we used logistic regression to investigate predictors of a subsequent resistant isolate during the same infection episode. We also investigated predictors of recurrent infection. Our analysis included 98,651 E. coli isolates and 121,755 S. aureus isolates from 70,851 patients between January 2007 and June 2020. Following an initially susceptible E. coli UTI, subsequent recovery of a cefazolin (8%) or ampicillin (13%) -resistant isolate during the same infection episode was more common than a ceftriaxone-resistant isolate (2%). For an initially susceptible S. aureus SSTI, subsequent recovery of a methicillin-resistant isolate (8%) was more common than a trimethoprim-sulfamethoxazole-resistant isolate (2%). For UTIs and SSTIs, prior infection with a resistant pathogen was a strong predictor of both recurrent infection and resistance in future infection episodes. This multi-centre study demonstrates an association between antibiotic resistance and an increased likelihood of recurrent infection. Particularly in remote areas, a patient's past antibiograms should guide current treatment choices since recurrent infection will most likely be at least as resistant as previous infection episodes. Using population-level surveillance data in this way can also help clinicians decide if they should switch antibiotics for patients with ongoing symptoms, while waiting for diagnostic results.

Favorable Aspects of Silymarin in Linezolid Treatment Against Diabetic Methicillin-Resistant Staphylococcus aureus (MRSA) Infected Rats

Background:

Linezolid used for diabetic methicillin-resistant Staphylococcus aureus (MRSA) infections is limited due to hepatotoxicity, lactic acidosis, anemia, and oxidative stress induced by diabetes and linezolid therapy. Silymarin is a hepatoprotective, antioxidant, antibacterial, and antidiabetic.

Objective:

The research investigated the role of silymarin in linezolid treatment against MRSA-infected diabetic rats.

Methods:

Type 2 diabetes mellitus (T2DM) was induced by a high-fat diet (58% calories fat) for 2 weeks, followed by a single intraperitoneal injection of streptozotocin (STZ) 35 mg/kg into Wistar rats. The diabetic rats were rendered neutropenic and subcutaneously injected with 106 CFU/ml of MRSA. Linezolid and silymarin were administered orally at a dose of 50 mg/kg twice daily for 14 days. The bacterial load/abscess, hematological, biochemical, enzymatic parameters, antioxidants, and histopathological studies were performed on the 42nd day.

Results:

The MRSA was confirmed by PCR assay. The minimum inhibitory concentration of linezolid was found to be 0.5-2 μg/ml. The linezolid treated MRSA infected diabetic rats showed 9.69 x 103 CFU / abscess bacterial count, decreased intestinal alkaline phosphatase (IAP), RBC, antioxidants, elevated lactate, and liver markers than diabetic rats. The silymarin treatment showed a decrease in the bacterial count (2.98 x 103 CFU / abscess), serum lactate, liver markers, increased IAP levels, and antioxidants in linezolid treated diabetic infected rats.

Conclusion:

The research concluded that silymarin could be a better herbal therapeutic agent that attenuated diabetic and linezolid induced complications in MRSA-infected diabetic rats.

Antimicrobial Management of Complicated Skin and Soft Tissue Infections in an Era of Emerging Multi-Drug Resistance: Perspectives from 5 Gulf Countries

The number of complicated skin and soft tissue infections (cSSTIs) in the Arabian Gulf region has risen in recent years, particularly those caused by multi-drug resistant (MDR) pathogens. The high prevalence of diabetes, obesity, and associated cardio-metabolic comorbidities in the region renders medical and surgical management of cSSTI patients with MDR infections challenging. An experienced panel of international and regional cSSTI experts (consensus group on cSSTIs) was convened to discuss clinical considerations for MDR infections from societal, antimicrobial stewardship, and cost perspectives, to develop best practice recommendations. This article discusses antibiotic therapies suitable for treating MDR cSSTIs in patients from the Gulf region and recommends that these should be tailored according to the local bacterial ecology by country and region. The article highlights the need for a comprehensive patient treatment pathway and defined roles of each of the multidisciplinary teams involved with managing patients with MDR cSSTIs. Aligned and inclusive definitions of cSSTIs for clinical and research purposes, thorough and updated epidemiological data on cSSTIs and methicillin-resistant <i>Staphylococcus aureus</i> in the region, clearcut indications of novel agents and comprehensive assessment of comparative data should be factored into decision-making are necessary.

Staphylococcus aureus uses the ArlRS and MgrA cascade to regulate immune evasion during skin infection

Skin is one of the most common sites of host immune response against Staphylococcus aureus infection. Here, through a combination of in vitro assays, mouse models, and intravital imaging, we find that S. aureus immune evasion in skin is controlled by a cascade composed of the ArlRS two-component regulatory system and its downstream effector, MgrA. S. aureus lacking either ArlRS or MgrA is less virulent and unable to form correct abscess structure due to de-repression of a giant surface protein, Ebh. These S. aureus mutants also have decreased expression of immune evasion factors (leukocidins, chemotaxis-inhibitory protein of S. aureus [CHIPS], staphylococcal complement inhibitor [SCIN], and nuclease) and are unable to kill neutrophils, block their chemotaxis, degrade neutrophil extracellular traps, and survive direct neutrophil attack. The combination of disrupted abscess structure and reduced immune evasion factors makes S. aureus susceptible to host defenses. ArlRS and MgrA are therefore the main regulators of S. aureus immune evasion and promising treatment targets.

Recalcitrant Staphylococcus aureus Infections: Obstacles and Solutions

Antibiotic treatment failure of Staphylococcus aureus infections is very common. In addition to genetically encoded mechanisms of antibiotic resistance, numerous additional factors limit the efficacy of antibiotics in vivo Identifying and removing the barriers to antibiotic efficacy are of major importance, as even if new antibiotics become available, they will likely face the same barriers to efficacy as their predecessors. One major obstacle to antibiotic efficacy is the proficiency of S. aureus to enter a physiological state that is incompatible with antibiotic killing. Multiple pathways leading to antibiotic tolerance and the formation of tolerant subpopulations called persister cells have been described for S. aureus Additionally, S. aureus is a versatile pathogen that can infect numerous tissues and invade a variety of cell types, of which some are poorly penetrable to antibiotics. It is therefore unlikely that there will be a single solution to the problem of recalcitrant S. aureus infection. Instead, specific approaches may be required for targeting tolerant cells within different niches, be it through direct targeting of persister cells, sensitization of persisters to conventional antibiotics, improved penetration of antibiotics to particular niches, or any combination thereof. Here, we examine two well-described reservoirs of antibiotic-tolerant S. aureus, the biofilm and the macrophage, the barriers these environments present to antibiotic efficacy, and potential solutions to the problem.

Risk factors for wound infection caused by Methicillin Resistant Staphylococcus aureus among hospitalized patients: a case control study from a tertiary care hospital in India

Background

Methicillin Resistant Staphylococcus aureus (MRSA) causes infection in hospitals and communities. The prevalence and risk factors of MRSA infection is not homogenous across the globe.

Objective

To find the risk factors of MRSA infection among hospitalized patients.

Methods

Cross-sectional case control study was conducted at a tertiary care hospital in India. The risk factors were collected using checklist from 130 MRSA and 130 Methicillin sensitive staphylococcus aureus (MSSA) infected patients. The pathogens were isolated from the wound swabs according to Clinical and Laboratory Standards Institute guidelines.

Results

Both the groups were comparable in terms of age, gender, diabetic status, undergoing invasive procedures, urinary catheterization and smoking (p>0.05). Multivariate logistic regression revealed surgical treatment (OR 4.355; CI 1.03, 18.328; p=0.045), prolonged hospitalization (OR 0.307; CI 0.11, 0.832; p=0.020), tracheostomy (OR 5.298, CI 1.16, 24.298; p=0.032), pressure/venous ulcer (OR 7.205; CI 1.75, 29.606; p=0.006) and previous hospitalization (OR 2.883; CI 1.25, 6.631; p=0.013) as significant risk factors for MRSA infection.

Conclusion

Surgical treatment, prolonged and history of hospitalization, having tracheostomy for ventilation and pressure/venous ulcer were the key risk factors. Therefore, special attention has to be given to the preventable risk factors while caring for hospitalized patients to prevent MRSA infection.

Skin and obesity in childhood: an update

<abstract> <p>Overweight and obesity have grown in children in the last decades and are now an epidemic, leading to significant public health issues in developed and underdeveloped nations. Obese children have a higher prevalence of skin lesions than normal weight children. The present study is an updated-on state of the art of studies describing the association between childhood obesity and related skin lesions. The most frequent obesity-associated dermatological complications in children are acanthosis nigricans and acrochordons, atopic dermatitis, skin infections, and endocrinological changes including hyperinsulinism and hyperandrogenism. Other common skin manifestations associated with obesity are striae distensae and plantar hyperkeratosis. Although the causes of the majority of the skin lesions associated with obesity are not known, the larger mass of adipose tissue and the secretion of peptides (cytokines, hormones, etc.) from enlarged fat cells due to obesity could lead to skin lesions. Therefore, the prevention of obesity is essential to avoid most skin-associated lesions.</p> </abstract>

Three-Dimensional In Vitro Staphylococcus aureus Abscess Communities Display Antibiotic Tolerance and Protection from Neutrophil Clearance

Staphylococcus aureus is a prominent human pathogen in bone and soft-tissue infections. Pathophysiology involves abscess formation, which consists of central staphylococcal abscess communities (SACs), surrounded by a fibrin pseudocapsule and infiltrating immune cells. Protection against the ingress of immune cells such as neutrophils, or tolerance to antibiotics, remains largely unknown for SACs and is limited by the lack of availability of in vitro models. We describe a three-dimensional in vitro model of SACs grown in a human plasma-supplemented collagen gel. The in vitro SACs reached their maximum size by 24 h and elaborated a fibrin pseudocapsule, as confirmed by electron and immunofluorescence microscopy. The in vitro SACs tolerated 100× the MIC of gentamicin alone and in combination with rifampin, while planktonic controls and mechanically dispersed SACs were efficiently killed. To simulate a host response, SACs were exposed to differentiated PLB-985 neutrophil-like (dPLB) cells and to primary human neutrophils at an early stage of SAC formation or after maturation at 24 h. Both cell types were unable to clear mature in vitro SACs, but dPLB cells prevented SAC growth upon early exposure before pseudocapsule maturation. Neutrophil exposure after plasmin pretreatment of the SACs resulted in a significant decrease in the number of bacteria within the SACs. The in vitro SAC model mimics key in vivo features, offers a new tool to study host-pathogen interactions and drug efficacy assessment, and has revealed the functionality of the S. aureus pseudocapsule in protecting the bacteria from host phagocytic responses and antibiotics.

Current Epidemiology, Etiology, and Burden of Acute Skin Infections in the United States

The US burden of acute skin infections is substantial. While Staphylococcus aureus and Streptococcus spp. are the most common causes, gram-negative bacteria and mixed infections can occur in some settings. These mixed infections are more likely to result in inappropriate empiric antibiotic therapy. Important challenges remain in diagnosing and treating acute skin infections.

Analysis of Pooled Phase III Efficacy Data for Delafloxacin in Acute Bacterial Skin and Skin Structure Infections

Background

Delafloxacin is an oral or intravenous (IV) antibiotic indicated for the treatment of acute bacterial skin and skin structure infections (ABSSSI), including both gram-positive (including methicillin-resistant Staphylococcus aureus [MRSA]) and gram-negative organisms. Chemically distinct from other quinolones, delafloxacin exhibits enhanced potency, particularly against gram-positive pathogens. The integration of efficacy data across the Phase III ABSSSI studies is presented here and allows for additional examination of results across subgroups.

Methods

Results of 2 multicenter, randomized, double-blind trials of 1510 adults with ABSSSI were pooled for this analysis. Subjects in the vancomycin arm received 15 mg/kg, plus 1–2 g of aztreonam every 12 hours. Delafloxacin was dosed at 300 mg IV every 12 hours in Study 302; dosing in Study 303 was 300 mg IV every 12 hours for 3 days, with a mandatory, blinded switch to delafloxacin at 450 mg orally every 12 hours. The primary endpoint was objective response (OR), defined as a ≥20% reduction of lesion spread of erythema area at the primary infection site at 48 to 72 hours (±2 hours), in the absence of clinical failure. Investigator-assessed response, based on the resolution of signs and symptoms at follow-up (FU; Day 14 ± 1) and late follow-up (LFU; Day 21– 28), were secondary endpoints.

Results

In the intent-to-treat analysis set, the OR was 81.3% in the delafloxacin arm and 80.7% in the comparator arm (mean treatment difference 0.8%, 95% confidence interval -3.2% to 4.7). Results for OR in the defined subgroups showed delafloxacin to be comparable to vancomycin/aztreonam. Investigator-assessed success was similar at FU (84.7% versus 84.1%) and LFU (82.0% versus 81.7%). Delafloxacin was comparable to vancomycin/aztreonam in the eradication of MRSA, at 98.1% versus 98.0%, respectively, at FU. The frequencies of treatment-emergent adverse events between the groups were similar.

Conclusions

Overall, IV/oral delafloxacin fixed-dose monotherapy was non-inferior to IV vancomycin/aztreonam combination therapy and was well tolerated in each Phase III study, as well as in the pooled analysis, regardless of endpoint or analysis population.

Methicillin-Resistant Staphylococcus aureus Eradication and Decolonization in Children Study (Part 2): Patient- and Parent-Centered Outcomes of Decolonization

BACKGROUND

Skin and soft tissue infections (SSTIs) due to community-acquired methicillin-resistant Staphylococcus aureus (MRSA) can lead to a number of significant known medical outcomes including hospitalization, surgical procedures such as incision and drainage (I&D), and the need for decolonization procedures to remove the bacteria from the skin and nose and prevent recurrent infection. Little research has been done to understand patient and caregiver-centered outcomes associated with the successful treatment of MRSA infection.

OBJECTIVE

This study aimed to uncover MRSA decolonization outcomes that are important to patients and their parents in order to create a set of prototype measures for use in the MRSA Eradication and Decolonization in Children (MEDiC) study.

METHODS

A 4-hour, human-centered design (HCD) workshop was held with 5 adolescents (aged 10-18 years) who had experienced an I&D procedure and 11 parents of children who had experienced an I&D procedure. The workshop explored the patient and family experience with skin infection to uncover patient-centered outcomes of MRSA treatment. The research team analyzed the audio and artifacts created during the workshop and coded for thematic similarity. The final themes represent patient-centered outcome domains to be measured in the MEDiC comparative effectiveness trial.

RESULTS

The workshop identified 9 outcomes of importance to patients and their parents: fewer MRSA outbreaks, improved emotional health, improved self-perception, decreased social stigma, increased amount of free time, increased control over free time, fewer days of school or work missed, decreased physical pain and discomfort, and decreased financial burden.

CONCLUSIONS

This study represents an innovative HCD approach to engaging patients and families with lived experience with MRSA SSTIs in the study design and trial development to determine meaningful patient-centered outcomes. We were able to identify 9 major recurrent themes. These themes were used to develop the primary and secondary outcome measures for MEDiC, a prospectively enrolling comparative effectiveness trial.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02127658; https://clinicaltrials.gov/ct2/show/NCT02127658.

Methicillin-Resistant Staphylococcus aureus Eradication and Decolonization in Children Study (Part 1): Development of a Decolonization Toolkit With Patient and Parent Advisors

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections affect many healthy children. A significant number of these children are hospitalized and require surgical incision and drainage (I&D). Once sent home, these children and families are asked to complete burdensome home decolonization and hygiene procedures in an effort to prevent the high rate of recurrent infections.

OBJECTIVE

This component of the Methicillin-resistant Staphylococcus aureus Eradication and Decolonization in Children (MEDiC) study aimed to develop a toolkit to assist MEDiC study participants in completing MRSA decolonization and hygiene procedures at home (the MEDiC kit).

METHODS

In all, 5 adolescents (aged 10-18 years) who had undergone an I&D procedure for a skin infection and 11 parents of children who had undergone an I&D procedure for a skin infection were engaged in a 4-hour group workshop using a human-centered design approach. The topics covered in this workshop and analyzed for this paper were (1) attitudes about MRSA decolonization procedures and (2) barriers to the implementation of MRSA decolonization and hygiene procedures. The team analyzed the audio and artifacts created during the workshop and synthesized their findings to inform the creation of the MEDiC kit.

RESULTS

The workshop activities uncovered barriers to successful completion of the decolonization and hygiene procedures: lack of step-by-step instruction, lack of proper tools in the home, concerns about adverse events, lack of control over some aspects of the hygiene procedures, and general difficulty coordinating all the procedures. Many of these could be addressed as part of the MEDiC kit. In addition, the workshop revealed that effective communication about decolonization would have to address concerns about the effects of bleach, provide detailed information, give reasons for the specific decolonization and hygiene protocol steps, and include step-by-step instructions (preferably through video).

CONCLUSIONS

Through direct engagement with patients and families, we were able to better understand how to support families in implementing MRSA decolonization and hygiene protocols. In addition, we were able to better understand how to communicate about MRSA decolonization and hygiene protocols. With this knowledge, we created a robust toolkit that uses patient-driven language and visuals to help support patients and families through the implementation of these protocols.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02127658; https://clinicaltrials.gov/ct2/show/NCT02127658.

Impact of Decolonization Protocols and Recurrence in Pediatric MRSA Skin and Soft-Tissue Infections

BACKGROUND

Methicillin-resistant staphylococcus aureus (MRSA) colonization is associated with the development of skin and soft-tissue infection in children. Although MRSA decolonization protocols are effective in eradicating MRSA colonization, they have not been shown to prevent recurrent MRSA infections. This study analyzed the prescription of decolonization protocols, rates of MRSA abscess recurrence, and factors associated with recurrence.

MATERIALS AND METHODS

This study is a single-institution retrospective review of patients ≤18 y of age diagnosed with MRSA culture-positive abscesses who underwent incision and drainage (I&D) at a tertiary-care children's hospital. The prescription of an MRSA decolonization protocol was recorded. The primary outcome was MRSA abscess recurrence.

RESULTS

Three hundred ninety-nine patients with MRSA culture-positive abscesses who underwent I&D were identified. Patients with previous history of abscesses, previous MRSA infection groin/genital region abscesses, higher number of family members with a history of abscess/cellulitis or MRSA infection, and I&D by a pediatric surgeon were more likely to be prescribed decolonization. Decolonized patients did not have lower rates of recurrence. Recurrence was more likely to occur in patients with previous abscesses, previous MRSA infection, family history of abscesses, family history of MRSA infection, Hispanic ethnicity, and those with fever on admission.

CONCLUSIONS

MRSA decolonization did not decrease the rate of recurrence of MRSA abscesses in our patient cohort. Patients at high risk for MRSA recurrence such as personal or family history of abscess or MRSA infection, Hispanic ethnicity, or fever on admission did not benefit from decolonization.

The Limited Utility of Routine Culture in Pediatric Pilonidal, Gluteal, and Perianal Abscesses

BACKGROUND

Pilonidal, buttock, and perianal abscesses are common reasons for surgical consultation in the pediatric emergency department. Treatment typically includes a bedside incision and drainage, often followed by an abscess culture, and a course of oral antibiotics. We aimed to study the impact of culture data on changes in management and clinical outcomes. We hypothesized that management is unaffected by culture data, and therefore, fluid culture from pilonidal, buttock, and perianal abscesses in the pediatric population may represent an unnecessary laboratory test and cost.

MATERIALS AND METHODS

A single institution's electronic medical record was searched between February 1, 2013 and August 1, 2017, identifying 249 pediatric patients meeting the inclusion criteria: age 0 to 18 y; diagnosis of pilonidal, buttock, or perianal abscess; bedside incision and drainage. Patients were divided into two different comparison groups for data analysis based on the presence or absence of culture and recurrence or no recurrence.

RESULTS

Culture results directly altered management in only 5 patient encounters (2.7% of all cultured). When comparing groups by culture or no culture, no statistically significant difference in recurrence rate (P = 0.4) was noted. When comparing groups by recurrence versus no recurrence, we found no statistically significant difference between sex, resident type, vessel loop use, packing use, or antibiotic use (P > 0.05).

CONCLUSIONS

We conclude that microbiological culture results are of limited utility in the management of pediatric pilonidal, buttock, and perianal abscesses as they do not appear to alter treatment, and omission of culture is not associated with failure of surgical management.

Validation of the American Association for the Surgery of Trauma emergency general surgery grade for skin and soft tissue infection

INTRODUCTION

Skin and soft tissue infections (SSTIs) present with variable severity. The American Association for the Surgery of Trauma (AAST) developed an emergency general surgery (EGS) grading system for several diseases. We aimed to determine whether the AAST EGS grade corresponds with key clinical outcomes.

METHODS

Single-institution retrospective review of patients (≥18 years) admitted with SSTI during 2012 to 2016 was performed. Patients with surgical site infections or younger than 18 years were excluded. Laboratory Risk Indicator for Necrotizing Fasciitis score and AAST EGS grade were assigned. The primary outcome was association of AAST EGS grade with complication development, duration of stay, and interventions. Secondary predictors of severity included tissue cultures, cross-sectional imaging, and duration of inpatient antibiotic therapy. Summary and univariate analyses were performed.

RESULTS

A total of 223 patients were included (mean ± SD age of 55.1 ± 17.0 years, 55% male). The majority of patients received cross sectional imaging (169, 76%) or an operative procedure (155, 70%). Skin and soft tissue infection tissue culture results included no growth (51, 24.5%), monomicrobial (83, 39.9%), and polymicrobial (74, 35.6%). Increased AAST EGS grade was associated with operative interventions, intensive care unit utilization, complication severity (Clavien-Dindo index), duration of hospital stay, inpatient antibiotic therapy, mortality, and hospital readmission.

CONCLUSION

The AAST EGS grade for SSTI demonstrates the ability to correspond with several important outcomes. Prospective multi-institutional study is required to determine its broad generalizability in several populations.

LEVEL OF EVIDENCE

Prognostic, level IV.

The Electron Transport Chain Sensitizes Staphylococcus aureus and Enterococcus faecalis to the Oxidative Burst

Small-colony variants (SCVs) of Staphylococcus aureus typically lack a functional electron transport chain and cannot produce virulence factors such as leukocidins, hemolysins, or the antioxidant staphyloxanthin. Despite this, SCVs are associated with persistent infections of the bloodstream, bones, and prosthetic devices. The survival of SCVs in the host has been ascribed to intracellular residency, biofilm formation, and resistance to antibiotics. However, the ability of SCVs to resist host defenses is largely uncharacterized. To address this, we measured the survival of wild-type and SCV S. aureus in whole human blood, which contains high numbers of neutrophils, the key defense against staphylococcal infection. Despite the loss of leukocidin production and staphyloxanthin biosynthesis, SCVs defective for heme or menaquinone biosynthesis were significantly more resistant to the oxidative burst than wild-type bacteria in human blood or the presence of purified neutrophils. Supplementation of the culture medium of the heme-auxotrophic SCV with heme, but not iron, restored growth, hemolysin and staphyloxanthin production, and sensitivity to the oxidative burst. Since Enterococcus faecalis is a natural heme auxotroph and cause of bloodstream infection, we explored whether restoration of the electron transport chain in this organism also affected survival in blood. Incubation of E. faecalis with heme increased growth and restored catalase activity but resulted in decreased survival in human blood via increased sensitivity to the oxidative burst. Therefore, the lack of functional electron transport chains in SCV S. aureus and wild-type E. faecalis results in reduced growth rate but provides resistance to a key immune defense mechanism.

An Update on Clinical Burden, Diagnostic Tools, and Therapeutic Options of Staphylococcus aureus

Staphylococcus aureus is an important pathogen responsible for a variety of diseases ranging from mild skin and soft tissue infections, food poisoning to highly serious diseases such as osteomyelitis, endocarditis, and toxic shock syndrome. Proper diagnosis of pathogen and virulence factors is important for providing timely intervention in the therapy. Owing to the invasive nature of infections and the limited treatment options due to rampant spread of antibiotic-resistant strains, the trend for development of vaccines and antibody therapy is increasing at rapid rate than development of new antibiotics. In this article, we have discussed elaborately about the host-pathogen interactions, clinical burden due to S aureus infections, status of diagnostic tools, and treatment options in terms of prophylaxis and therapy.

Diet-Induced Obesity Does Not Alter Tigecycline Treatment Efficacy in Murine Lyme Disease

Obese individuals more frequently suffer from infections, as a result of increased susceptibility to a number of bacterial pathogens. Furthermore, obesity can alter antibiotic treatment efficacy due to changes in drug pharmacokinetics which can result in under-dosing. However, studies on the treatment of bacterial infections in the context of obesity are scarce. To address this research gap, we assessed efficacy of antibiotic treatment in diet-induced obese mice infected with the Lyme disease pathogen, Borrelia burgdorferi. Diet-induced obese C3H/HeN mice and normal-weight controls were infected with B. burgdorferi, and treated during the acute phase of infection with two doses of tigecycline, adjusted to the weights of diet-induced obese and normal-weight mice. Antibiotic treatment efficacy was assessed 1 month after the treatment by cultivating bacteria from tissues, measuring severity of Lyme carditis, and quantifying bacterial DNA clearance in ten tissues. In addition, B. burgdorferi-specific IgG production was monitored throughout the experiment. Tigecycline treatment was ineffective in reducing B. burgdorferi DNA copies in brain. However, diet-induced obesity did not affect antibiotic-dependent bacterial DNA clearance in any tissues, regardless of the tigecycline dose used for treatment. Production of B. burgdorferi-specific IgGs was delayed and attenuated in mock-treated diet-induced obese mice compared to mock-treated normal-weight animals, but did not differ among experimental groups following antibiotic treatment. No carditis or cultivatable B. burgdorferi were detected in any antibiotic-treated group. In conclusion, obesity was associated with attenuated and delayed humoral immune responses to B. burgdorferi, but did not affect efficacy of antibiotic treatment.

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.

The Effects of Patient Obesity on Early Postoperative Complications After Shoulder Arthroscopy

PURPOSE

To report the prevalence of obesity in shoulder arthroscopy, determine a body mass index (BMI) threshold most predictive of complication within 30 days, and evaluate obesity as an independent risk factor for medical and surgical complications.

METHODS

Using the National Surgical Quality Improvement Program database, we reviewed all patients who underwent shoulder arthroscopy during 2011 to 2013. Receiver operating characteristic and Youden coefficient were calculated to find an optimal BMI cutoff to predict complications within 30 days of surgery. A case-control matched analysis was then performed by stratifying patient BMI by this cutoff and matching patients one to one according to age, sex, type of shoulder arthroscopy, American Society of Anesthesiology rating, surgical setting, and 8 comorbidities. Operating time, complications, and readmissions were also compared.

RESULTS

Of the 15,589 patients who underwent shoulder arthroscopy, 6,684 (43%) were classified as obese when using the optimal cutoff point of BMI = 30 according to the Youden coefficient. Obese patients had a higher risk of superficial site infection than nonobese patients (0.3% vs 0.0%; odds ratio [OR]: 6.00; 95% confidence interval [CI], 1.3 to 26.8; P = .015). Obese patients did not have significantly increased risk for overall early postoperative complication (1.2% compared with nonobese 0.8%; OR: 1.54; 95% CI, 1.0 to 2.4), readmissions (OR: 0.85; 95% CI, 0.5 to 1.5), or increased operating time (P = .068).

CONCLUSIONS

Up to 43% of patients undergoing shoulder arthroscopy can be classified as obese, but early perioperative complications are uncommon. Higher patient BMI is associated with increased risk of superficial site infection but not an overall risk for complication, readmission, or increased operating time.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Pathogenesis of Staphylococcus aureus Bloodstream Infections

Staphylococcus aureus, a Gram-positive bacterium colonizing nares, skin, and the gastrointestinal tract, frequently invades the skin, soft tissues, and bloodstreams of humans. Even with surgical and antibiotic therapy, bloodstream infections are associated with significant mortality. The secretion of coagulases, proteins that associate with and activate the host hemostatic factor prothrombin, and the bacterial surface display of agglutinins, proteins that bind polymerized fibrin, are key virulence strategies for the pathogenesis of S. aureus bloodstream infections, which culminate in the establishment of abscess lesions. Pathogen-controlled processes, involving a wide spectrum of secreted factors, are responsible for the recruitment and destruction of immune cells, transforming abscess lesions into purulent exudate, with which staphylococci disseminate to produce new infectious lesions or to infect new hosts. Research on S. aureus bloodstream infections is a frontier for the characterization of protective vaccine antigens and the development of immune therapeutics aiming to prevent disease or improve outcomes.

Examination of hospital length of stay in Canada among patients with acute bacterial skin and skin structure infection caused by methicillin-resistant Staphylococcus aureus

PURPOSE

Skin infections, particularly those caused by resistant pathogens, represent a clinical burden. Hospitalization associated with acute bacterial skin and skin structure infections (ABSSSI) caused by methicillin-resistant Staphylococcus aureus (MRSA) is a major contributor to the economic burden of the disease. This study was conducted to provide current, real-world data on hospitalization patterns for patients with ABSSSI caused by MRSA across multiple geographic regions in Canada.

PATIENTS AND METHODS

This retrospective cohort study evaluated length of stay (LOS) for hospitalized patients with ABSSSI due to MRSA diagnosis across four Canadian geographic regions using the Discharge Abstract Database. Patients with ICD-10-CA diagnosis consistent with ABSSSI caused by MRSA between January 2008 and December 2014 were selected and assigned a primary or secondary diagnosis based on a prespecified ICD-10-CA code algorithm.

RESULTS

Among 6,719 patients, 3,273 (48.7%) and 3,446 (51.3%) had a primary and secondary diagnosis, respectively. Among patients with a primary or secondary diagnosis, the cellulitis/erysipelas subtype was most common. The majority of patients presented with 0 or 1 comorbid condition; the most common comorbidity was diabetes. The mean LOS over the study period varied by geographic region and year; in 2014 (the most recent year analyzed), LOS ranged from 7.7 days in Ontario to 13.4 days in the Canadian Prairie for a primary diagnosis and from 18.2 days in Ontario to 25.2 days in Atlantic Canada for a secondary diagnosis. A secondary diagnosis was associated with higher rates of continuing care compared with a primary diagnosis (10.6%-24.2% vs 4.6%-12.1%).

CONCLUSION

This study demonstrated that the mean LOS associated with ABSSSI due to MRSA in Canada was minimally 7 days. Clinical management strategies, including medication management, which might facilitate hospital discharge, have the potential to reduce hospital LOS and related economic burden associated with ABSSSI caused by MRSA.

Host factors that contribute to recurrent staphylococcal skin infection

PURPOSE OF REVIEW

Staphylococcus aureus is the most common cause of skin and soft tissue infections (SSTI) in the United States and elsewhere. Recurrent infections occur frequently in patients with S. aureus SSTI, underscoring the need to better understand the nature of protective immunity against these infections. Here, we review recent findings concerning the host factors that predispose to S. aureus SSTI.

RECENT FINDINGS

Recurrent infections occur in nearly half of all patients with S. aureus SSTI. Epidemiologic and environmental factors, such as exposure to healthcare, age, and household contacts with S. aureus SSTI, and contaminated household fomites are associated with recurrence. The majority of the population has evidence of antistaphylococcal antibodies, but whether these are protective remains enigmatic. In contrast, recent clinical and experimental findings clearly highlight the critical roles of innate and T cell-mediated immunity in defense against these infections. S. aureus interferes with innate and adaptive immunity by a number of recently elucidated mechanisms.

SUMMARY

Recurrent S. aureus SSTIs are common, suggesting incomplete or absent protective immunity among these patients. Our understanding of protective immunity against recurrent infections is incomplete, and further basic and translational investigation is urgently needed to design strategies to prevent and treat these infections.

A randomized, double-blind, Phase 2 study to evaluate subjective and objective outcomes in patients with acute bacterial skin and skin structure infections treated with delafloxacin, linezolid or vancomycin

Objectives

Delafloxacin is an investigational anionic fluoroquinolone being developed to treat infections caused by Gram-positive and -negative organisms. This clinical trial evaluated the efficacy and safety of delafloxacin in the treatment of acute bacterial skin and skin structure infections (ABSSSIs).

Methods

In a double-blind, Phase 2 trial, 256 patients were randomized (1 : 1 : 1) to 300 mg of delafloxacin, 600 mg of linezolid or 15 mg/kg vancomycin (actual body weight), each administered intravenously twice daily for 5–14 days. Randomization was stratified by infection category. The primary endpoint was the investigator's assessment of cure, defined as complete resolution of baseline signs and symptoms at follow-up. Secondary endpoints included reductions in the total areas of erythema and induration and assessments of bacterial eradication. This trial has been registered at ClinicalTrials.gov under registration number NCT01283581.

Results

Cure rates were significantly greater with delafloxacin versus vancomycin (mean difference: −16.3%; 95% CI, −30.3% to −2.3%; P = 0.031); differences were significant for obese patients (BMI ≥30 kg/m²; mean difference: −30.0%; 95% CI, −50.7% to −9.3%; P = 0.009), but not for non-obese patients. Cure rates with delafloxacin and linezolid were similar. Using digital measurement, the percentage decrease in total erythema area was significantly greater with delafloxacin versus vancomycin at follow-up (−96.4% versus −84.5%; P = 0.028). There were no differences in bacterial eradication among the treatment groups. The most frequently reported treatment-emergent adverse events were nausea, diarrhoea and vomiting.

Conclusions

These data show that delafloxacin is effective in the treatment of ABSSSIs and is well tolerated.

Risk Factors Associated With Abscess Formation in Children 5 Years of Age and Younger

From 1997 to 2009, hospitalization rates have doubled for pediatric patients with soft tissue abscesses requiring incision and drainage. Despite this increasing national burden, few studies have been conducted to identify the risk factors associated with abscess formation. Our study evaluates a collection of physiological and lifestyle parameters that may serve as risk factors for abscess formation among pediatric patients 5 years of age or younger. Our results indicate family history and age 2 years and younger are associated with higher risk of abscess formation. Furthermore, methicillin-resistant Staphylococcus aureus and methicillin-susceptible Staphylococcus aureus were prevalent pathogens associated with abscess in our study group. Pediatricians may employ these novel parameters to educate parents and/or guardians of high-risk groups on preventing abscess formation to alleviate the burden of incision & dragining requiring abscess on health care costs.

Decolonization of children after incision and drainage for MRSA abscess: a retrospective cohort study

BACKGROUND/PURPOSE

Whether decolonization following incision and drainage (I&D) for methicillin-resistant Staphylococcus aureus (MRSA) abscess decreases repeat I&D and MRSA-positive cultures in children is unknown.

MATERIALS/METHODS

Referral to the Pediatric Infectious Disease Service (PIDS) for decolonization was determined for eligible children (2003-2010), with outcomes studied over 12 months.

RESULTS

We identified 653 children; 54 had been seen by PIDS. In the PIDS group, no patients (0/54, 0%) had a repeat I&D. In the no PIDS group 36/599 (6%) had a repeat I&D, P = .06. Logistic regression modeling for repeat I&D showed no significant effect, odds ratio = 0.29; 95% confidence interval = 0.04-2.15; P = .23. In the PIDS group, 3 patients (3/54, 5.6%) had a repeat MRSA-positive culture. In the no PIDS group, 58/599 (9.7%) had a positive repeat culture, P = .46. Logistic regression modeling for positive culture showed no significant effect (odds ratio = 0.55; 95% confidence interval = 0.17-1.81; P = .32).

CONCLUSIONS

We detected no statistically significant association between decolonization and repeat I&D or MRSA-positive culture.

Mechanisms of NDV-3 vaccine efficacy in MRSA skin versus invasive infection

Increasing rates of life-threatening infections and decreasing susceptibility to antibiotics urge development of an effective vaccine targeting Staphylococcus aureus. This study evaluated the efficacy and immunologic mechanisms of a vaccine containing a recombinant glycoprotein antigen (NDV-3) in mouse skin and skin structure infection (SSSI) due to methicillin-resistant S. aureus (MRSA). Compared with adjuvant alone, NDV-3 reduced abscess progression, severity, and MRSA density in skin, as well as hematogenous dissemination to kidney. NDV-3 induced increases in CD3+ T-cell and neutrophil infiltration and IL-17A, IL-22, and host defense peptide expression in local settings of SSSI abscesses. Vaccine induction of IL-22 was necessary for protective mitigation of cutaneous infection. By comparison, protection against hematogenous dissemination required the induction of IL-17A and IL-22 by NDV-3. These findings demonstrate that NDV-3 protective efficacy against MRSA in SSSI involves a robust and complementary response integrating innate and adaptive immune mechanisms. These results support further evaluation of the NDV-3 vaccine to address disease due to S. aureus in humans.

Resource use in patients hospitalized with complicated skin and soft tissue infections in Europe and analysis of vulnerable groups: the REACH study

BACKGROUND

Hospitalized patients with complicated skin and soft tissue infections (cSSTI) present a substantial economic burden, and resource use can vary according to the presence of comorbidities, choice of antibiotic agent, and the requirement for initial treatment modification. REACH (NCT01293435) was a retrospective, observational study aimed at collecting empirical data on current (year 2010-2011) management strategies of cSSTI in 10 European countries.

METHODS

Patients (n = 1995) were aged ≥18 years, hospitalized with a cSSTI and receiving intravenous antibiotics. Data, collected via electronic Case Report Forms, detailed patient characteristics, medical history, disease characteristics, microbiological diagnosis, disease course and outcomes, treatments before and during hospitalization, and health resource consumption.

RESULTS

For the analysis population, mean length of hospital stay (including duration of hospitalizations for patients with recurrences) was 18.5 days (median 12.0). Increased length of hospital stay was found for patients with comorbidities vs those without (mean = 19.9; [median = 14.0] days vs 13.3 [median = 8.0] days), for patients with methicillin-resistant Staphylococcus aureus compared with patients with methicillin-sensitive S. aureus (mean = 27.7 [median = 19.5] days vs 18.4 [median = 13.0] days) and for patients requiring surgery (mean = 24.4 [median = 16.0] days vs 15.0 [median = 11.0] days). Patients requiring modification of their initial antibiotic treatment had an associated increase in mean length of hospital stay of 10.9 days (median = 6.5) and additional associated hospital resource use. A multivariate analysis confirmed the association of nosocomial infections, comorbidities, directed treatment, recurrent infections, diabetes, recent surgery, and older age (≥65 years), with longer hospital stay.

CONCLUSIONS

This study provides real-life data on factors that are expected to impact length of hospital stay, to guide clinical decision-making to improve outcomes, and reduce resource use in patients with cSSTI.

The Agr quorum-sensing system regulates fibronectin binding but not hemolysis in the absence of a functional electron transport chain

Staphylococcus aureus is responsible for numerous chronic and recurrent infections, which are frequently associated with the emergence of small-colony variants (SCVs) that lack a functional electron transport chain. SCVs exhibit enhanced expression of fibronectin-binding protein (FnBP) and greatly reduced hemolysin production, although the basis for this is unclear. One hypothesis is that these phenotypes are a consequence of the reduced Agr activity of SCVs, while an alternative is that the lack of a functional electron transport chain and the resulting reduction in ATP production are responsible. Disruption of the electron transport chain of S. aureus genetically (hemB and menD) or chemically, using 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), inhibited both growth and Agr activity and conferred an SCV phenotype. Supplementation of the culture medium with synthetic autoinducing peptide (sAIP) significantly increased Agr expression in both hemB mutant strains and S. aureus grown with HQNO and significantly reduced staphylococcal adhesion to fibronectin. However, sAIP did not promote hemolysin expression in hemB mutant strains or S. aureus grown with HQNO. Therefore, while Agr regulates fibronectin binding in SCVs, it cannot promote hemolysin production in the absence of a functional electron transport chain.

Mouse models for infectious diseases caused by Staphylococcus aureus

Staphylococcus aureus - a commensal of the human skin, nares and gastrointestinal tract - is also a leading cause of bacterial skin and soft tissue infection (SSTIs), bacteremia, sepsis, peritonitis, pneumonia and endocarditis. Antibiotic-resistant strains, designated MRSA (methicillin-resistant S. aureus), are common and represent a therapeutic challenge. Current research and development efforts seek to address the challenge of MRSA infections through vaccines and immune therapeutics. Mice have been used as experimental models for S. aureus SSTI, bacteremia, sepsis, peritonitis and endocarditis. This work led to the identification of key virulence factors, candidate vaccine antigens or immune-therapeutics that still require human clinical testing to establish efficacy. Past failures of human clinical trials raised skepticism whether the mouse is an appropriate model for S. aureus disease in humans. S. aureus causes chronic-persistent infections that, even with antibiotic or surgical intervention, reoccur in humans and in mice. Determinants of S. aureus evasion from human innate and adaptive immune responses have been identified, however only some of these are relevant in mice. Future research must integrate these insights and refine the experimental mouse models for specific S. aureus diseases to accurately predict the failure or success for candidate vaccines and immune-therapeutics.

Surface proteins of Staphylococcus aureus play an important role in experimental skin infection

Staphylococcus aureus is the most common cause of skin infections that range from mild diseases up to life-threatening conditions. Mechanisms of S. aureus virulence in those infections remain poorly studied. To investigate the impact of S. aureus surface proteins on skin infection, we used mouse models of skin abscess formation and skin necrosis, induced by a subcutaneous injection of bacteria. In the skin abscess model, a sortase-deficient S. aureus strain lacking all of its cell-wall anchored proteins was less virulent than its wild-type strain. Also, strains specifically lacking protein A, fibronecting binding proteins, clumping factor A or surface protein SasF were impaired in their virulence. When a model of dermonecrosis was studied, the S. aureus surface proteins could not be shown to be involved. In summary, surface proteins play an important role in virulence of S. aureus skin abscess infections, but not in formation of skin necrosis.

Predischarge postpartum methicillin resistant Staphylococcus aureus infection and group B streptococcus carriage at the individual and hospital levels

Background. We sought to characterize the relationship between individual group B streptococcus (GBS) colonization and pre-discharge postpartum methicillin resistant Staphylococcus aureus (MRSA) infection in United States women delivering at term. We also sought to examine the association between hospital GBS colonization prevalence and MRSA infection. Materials and Methods. Data was from the Nationwide Inpatient Sample, a representative sample of United States community hospitals. Hierarchical regression models were used to estimate odds ratios adjusted for patient age, race, expected payer, and prepregnancy diabetes and hospital teaching status, urbanicity, ownership, size, and geographic region. We used multiple imputation for missing covariate data. Results. There were 3,136,595 deliveries and 462 cases of MRSA infection included in this study. The odds ratio for individual GBS colonization was 1.2 (95% confidence interval: 0.9 to 1.5). For a five-percent increase in the hospital prevalence of GBS colonization, the odds ratio was 0.9 (95% CI: 0.1 to 5.6). Conclusions. The odds ratio estimate for the association of hospital GBS prevalence with MRSA infection is too imprecise to make conclusions about its magnitude and direction. Barring major bias in our estimates, individual GBS carriage does not appear to be strongly associated with predischarge postpartum MRSA infection.

Recurrent community-associated Staphylococcus aureus infections in children presenting to Texas Children's Hospital in Houston, Texas

BACKGROUND

There are limited data characterizing recurrent staphylococcal disease in children. We sought to define the clinical features and laboratory findings of children with recurrent community-associated Staphylococcus aureus infections presenting to Texas Children's Hospital in Houston, TX.

METHODS

Medical records of children with recurrent, culture-proven community-associated S. aureus infections at Texas Children's Hospital from 8/1/2001 to 7/29/2009 were reviewed, and antibiotic susceptibility patterns were obtained for all S. aureus isolates.

RESULTS

Six hundred ninety-four otherwise healthy patients presented to Texas Children's Hospital with 2-7 episodes of community-associated S. aureus infection, accounting for 1495 encounters, 823 hospitalizations and 3337 inpatient days. In 90% of patients with ≤12 months separating their initial and recurrent infections, the methicillin susceptibility of the initial and recurrent isolates was the same, compared with 79% of patients with > 12 months separating their infections. The overall antibiotic susceptibility pattern did not change between isolates in 71% of otherwise healthy children compared with only 33% of children with eczema. Ninety-two percent of otherwise healthy children had only recurrent skin and soft tissue infections; 8% had ≥1 non-skin and soft tissue infections. The location of skin and soft tissue infections varied by age, with children≤36 months of age being more likely to have ≥1 S. aureus infection located in the diaper area.

CONCLUSIONS

Our study demonstrates that recurrent staphylococcal disease requiring emergency center or inpatient care is common, accounting for significant utilization of hospital resources. Children with recurrent staphylococcal infections are likely to have repeated infections from the same staphylococcal strain (by antibiotic susceptibility pattern), indicating that persistent colonization, frequent exposure to others who are chronically colonized, or environmental contamination is playing a role in recurrent disease. Finally, our study emphasizes the need for repeat cultures in children with recurrent disease, as 29% of healthy children and 67% of children with a predisposing risk factor (such as eczema) have a change in the antibiotic susceptibility pattern between S. aureus isolates.

Diabetes and early postpartum methicillin-resistant Staphylococcus aureus infection in US hospitals

BACKGROUND

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) infection in postpartum women is not well characterized. Because diabetes is a risk factor for some infections, we sought to characterize the relationship between diabetes and invasive MRSA infections in women admitted to US hospitals for delivery of an infant.

METHODS

We used data from the Nationwide Inpatient Sample, a representative sample of US community hospitals. Multivariate hierarchical logistic regression was used to estimate odds ratios (OR), adjusting for age, race, selected comorbidities, and expected payer, and hospital teaching status, urbanicity, bed size, geographic region, and ownership.

RESULTS

The odds ratio for prepregnancy diabetes was 3.4 (95% confidence interval: 1.9-6.0). The relationship remained strong after external adjustment for obesity (OR, 2.5; 95% CI: 1.3-4.8). The OR comparing women with complicated versus uncomplicated diabetes was 1.5 (95% CI: 0.3-6.0). We did not find an association with gestational diabetes (OR, 1.1; 95% CI: 0.7-1.7).

CONCLUSION

Prepregnancy diabetes, but not gestational diabetes, appears to be a risk factor for invasive MRSA infection in the early postpartum period. Women with diabetic complications may be at additional risk, but estimates were imprecise.

Short-course therapy for severe infections

A short course of antimicrobial therapy should be the aim of all treatment unless otherwise indicated. Factors allowing short treatment courses are those that depend on the host, on the infection and on the agents administered. In essence, immunodeficiencies, long-standing infections, abscesses, or infections associated with foreign bodies cannot be treated with short-course therapies. Bactericidal antibiotics are the only agents suitable for short-course therapy. Many severe infections such as primary bacteraemia and bacteraemia complicating pneumonia, acute pyelonephritis and meningitis are amendable to short-course therapy, whilst others are not. The benefits of short-duration therapy are obvious and may contribute to halting resistance, reduced costs and rational patient management.

Skin and soft tissue infections and associated complications among commercially insured patients aged 0-64 years with and without diabetes in the U.S

Introduction

Skin and soft tissue infections (SSTIs) are common infections occurring in ambulatory and inpatient settings. The extent of complications associated with these infections by diabetes status is not well established.

Methods

Using a very large repository database, we examined medical and pharmacy claims of individuals aged 0–64 between 2005 and 2010 enrolled in U.S. health plans. Diabetes, SSTIs, and SSTI-associated complications were identified by ICD-9 codes. SSTIs were stratified by clinical category and setting of initial diagnosis.

Results

We identified 2,227,401 SSTI episodes, 10% of which occurred in diabetic individuals. Most SSTIs were initially diagnosed in ambulatory settings independent from diabetes status. Abscess/cellulitis was the more common SSTI group in diabetic and non-diabetic individuals (66% and 59%, respectively). There were differences in the frequencies of SSTI categories between diabetic and non-diabetic individuals (p<0.01). Among SSTIs diagnosed in ambulatory settings, the SSTI-associated complication rate was over five times higher in people with diabetes than in people without diabetes (4.9% vs. 0.8%, p<0.01) and SSTI-associated hospitalizations were 4.9% and 1.1% in patients with and without diabetes, respectively. Among SSTIs diagnosed in the inpatient setting, bacteremia/endocarditis/septicemia/sepsis was the most common associated complication occurring in 25% and 16% of SSTIs in patients with and without diabetes, respectively (p<0.01).

Conclusions

Among persons with SSTIs, we found SSTI-associated complications were five times higher and SSTI-associated hospitalizations were four times higher, in patients with diabetes compared to those without diabetes. SSTI prevention efforts in individuals with diabetes may have significant impact on morbidity and healthcare resource utilization.

Phenotype switching is a natural consequence of Staphylococcus aureus replication

The pathogen Staphylococcus aureus undergoes phenotype switching in vivo from its normal colony phenotype (NCP) to a slow-growing, antibiotic-resistant small-colony-variant (SCV) phenotype that is associated with persistence in host cells and tissues. However, it is not clear whether phenotype switching is the result of a constitutive process that is selected for under certain conditions or is triggered by particular environmental stimuli. Examination of cultures of diverse S. aureus strains in the absence of selective pressure consistently revealed a small gentamicin-resistant SCV subpopulation that emerged during exponential-phase NCP growth and increased in number until NCP stationary phase. Treatment of replicating bacteria with the antibiotic gentamicin, which inhibited NCP but not SCV replication, resulted in an initial decrease in SCV numbers, demonstrating that SCVs arise as a consequence of NCP replication. However, SCV population expansion in the presence of gentamicin was reestablished by selection of phenotype-stable SCVs and subsequent SCV replication. In the absence of selective pressure, however, phenotype switching was bidirectional and occurred at a high frequency during NCP replication, resulting in SCV turnover. In summary, these data demonstrate that S. aureus phenotype switching occurs via a constitutive mechanism that generates a dynamic, antibiotic-resistant subpopulation of bacteria that can revert to the parental phenotype. The emergence of SCVs can therefore be considered a normal part of the S. aureus life cycle and provides an insurance policy against exposure to antibiotics that would otherwise eliminate the entire population.

Obesity and the risk and outcome of infection

The interactions between obesity and infectious diseases have recently received increasing recognition as emerging data have indicated an association between obesity and poor outcome in pandemic H1N1 influenza infection. Obesity is an established risk factor for surgical-site infections, nosocomial infections, periodontitis and skin infections. Several studies indicate that acute pancreatitis is more severe in the obese. Data are controversial and limited as regards the association between obesity and the risk and outcome of community-acquired infections such as pneumonia, bacteremia and sepsis and obesity and the course of HIV infection. As the cause-effect relationship between obesity and infection remains obscure in many infectious diseases, further studies are warranted. The consequences of obesity may have substantial effects on the global burden of infectious diseases.

Challenges for a universal Staphylococcus aureus vaccine

This review considers the reasons why the staphylococcal vaccine trials may have failed, based on new information about protective immunity against Staphylococcus aureus. The clinical trials and future vaccine candidate antigens are reviewed. Challenges facing the development of a universal S. aureus vaccine are also considered. The lack of a biomarker that is able to predict protection is a major stumbling block in the development of a staphylococcal vaccine. The major new information involves the role of cell-mediated immunity, specifically T-helper 17 cells and interleukin 17, as well as the lack of protection afforded by specific antibodies. This has major implications for future vaccine development and planning of clinical trials.

Obesity and the skin

Obesity is a serious global health problem, perhaps the biggest public health issue of our times. Excess body weight may be a factor in carcinogenesis in general, as well as contributing to the pathogenesis of metabolic, cardiovascular and musculoskeletal disorders. Obesity also has many cutaneous features, which form the basis for this review article. Many of these clinical entities are common to the majority of obese patients, e.g. striae distensae, plantar hyperkeratosis and an increased risk of skin infections. However, it may also be associated with poor wound healing, malignant melanoma and an increased risk of inflammatory dermatoses, such as psoriasis, as well as some rarer disorders. Therapeutic interventions for obesity, whether over-the-counter, prescription medicines or surgical interventions, are increasingly commonplace. All of these treatment modalities potentially have dermatological side-effects too.

Development of a vaccine against Staphylococcus aureus

A vaccine to prevent infections caused by Staphylococcus aureus would have a tremendously beneficial impact on public health. In contrast to typical encapsulated bacterial pathogens, such as Streptococcus pneumoniae, H. influenzae, and Neisseria meningitides, the capsule of S. aureus is not clearly linked to strain virulence in vivo. Furthermore, it is not clear that natural infection caused by S. aureus induces a protective humoral immune response, as does infection caused by typical encapsulated bacteria. Finally, pure B cell or antibody deficiency, in either animal models or in patients, does not predispose to more frequent or more severe S. aureus infections, as it does for infections caused by typical encapsulated bacteria. Rather, primary immune mechanisms necessary for protection against S. aureus infections include professional phagocytes and T lymphocytes (Th17 cells, in particular) which upregulate phagocytic activity. Thus, it is not clear whether an antibody-mediated neutralization of S. aureus virulence factors should be the goal of vaccination. Rather, the selection of antigenic targets which induce potent T cell immune responses that react to the broadest possible array of S. aureus strains should be the focus of antigen selection. Of particular promise is the potential to select antigens which induce both humoral and T cell-mediated immunity in order to generate immune synergy against S. aureus infections. A single-antigen vaccine may achieve this immune synergy. However, multivalent antigens may be more likely to induce both humoral and T cell immunity and to induce protection against a broader array of S. aureus isolates. A number of candidate vaccines are in development, raising the promise that effective vaccines against S. aureus will become available in the not-so-distant future. Possible development programs for such vaccines are discussed.

Comparative effectiveness of antibiotic treatment strategies for pediatric skin and soft-tissue infections

OBJECTIVE

To compare the effectiveness of clindamycin, trimethoprim-sulfamethoxazole, and β-lactams for the treatment of pediatric skin and soft-tissue infections (SSTIs).

METHODS

A retrospective cohort of children 0 to 17 years of age who were enrolled in Tennessee Medicaid, experienced an incident SSTI between 2004 and 2007, and received treatment with clindamycin (reference), trimethoprim-sulfamethoxazole, or a β-lactam was created. Outcomes included treatment failure and recurrence, defined as an SSTI within 14 days and between 15 and 365 days after the incident SSTI, respectively. Adjusted models stratified according to drainage status were used to estimate the risk of treatment failure and time to recurrence.

RESULTS

Among the 6407 children who underwent drainage, there were 568 treatment failures (8.9%) and 994 recurrences (22.8%). The adjusted odds ratios for treatment failure were 1.92 (95% confidence interval [CI]: 1.49-2.47) for trimethoprim-sulfamethoxazole and 2.23 (95% CI: 1.71-2.90) for β-lactams. The adjusted hazard ratios for recurrence were 1.26 (95% CI: 1.06-1.49) for trimethoprim-sulfamethoxazole and 1.42 (95% CI: 1.19-1.69) for β-lactams. Among the 41 094 children without a drainage procedure, there were 2435 treatment failures (5.9%) and 5436 recurrences (18.2%). The adjusted odds ratios for treatment failure were 1.67 (95% CI: 1.44-1.95) for trimethoprim-sulfamethoxazole and 1.22 (95% CI: 1.06-1.41) for β-lactams; the adjusted hazard ratios for recurrence were 1.30 (95% CI: 1.18-1.44) for trimethoprim-sulfamethoxazole and 1.08 (95% CI: 0.99-1.18) for β-lactams.

CONCLUSIONS

Compared with clindamycin, use of trimethoprim-sulfamethoxazole or β-lactams was associated with increased risks of treatment failure and recurrence. Associations were stronger for those with a drainage procedure.