Invasive Staphylococcal Infections Research Articles

OTULIN-related conditions: Report of a new case and review of the literature using GenIA

OTULIN encodes an eponymous linear deubiquitinase (DUB) essential for controlling inflammation as a negative regulator of the canonical NF-κB signaling pathway via the regulation of M1-Ub dynamics. Biallelic loss-of-function (LOF) mutations in OTULIN cause an autosomal recessive condition named Otulin-Related Autoinflammatory Syndrome (ORAS), also known as Otulipenia or AutoInflammation, Panniculitis, and Dermatosis Syndrome (AIPDS). Monoallelic OTULIN LOF, also known as OTULIN Haploinsufficiency (OHI) or Immunodeficiency 107 (IMD107), has been linked to an incompletely penetrant, dominantly inherited susceptibility to invasive Staphylococcal infections. At the same time, a recent novel ORAS-like inflammatory syndrome was described in association with a heterozygous missense mutation that appears to exert dominant negative (DN) effects. In this manuscript, we report the identification of a novel homozygous missense mutation, c.595 T > A; p.(Trp199Arg), in a Moroccan infant with an ORAS phenotype and provide experimental evidence for its pathogenicity. We go on to systematically review the literature for OTULIN-associated conditions by using the GenIA database (www.geniadb.net) to collect, extract and harmonize all clinical, laboratory and functional data for published patients and variants. Our comprehensive synthesis of genotypic, phenotypic, and mechanistic data enables a more in-depth view of the diverse mechanisms and pathways by which the OTULIN pathogenic variants may lead to human immune disease. This review may help variant classification activities and inform future variant evaluation, as well as the development of diagnostic and management guidelines. It also identifies current knowledge gaps and raises additional questions warranting future investigation.

English

The 24-h area under the curve concentration (AUC24 h) is associated with better clinical and bacteriological response to vancomycin in patients with methicillin-resistant Staphylococcus aureus who achieve the target AUC24 h between 400 and 700 mg×h/L. Recent consensus recommends maintaining trough concentrations between 15 and 20 mg/mL as a convenient target  to reach an AUC/minimum inhibitory concentration (MIC) ≥ 400. The aim of this study was to determine the correlation between a calculated AUC24 h and a measured trough vancomycin concentration (C0). We conducted a retrospective observational study. Hospitalized patients prescribed vancomycin for a presumed or documented invasive staphylococcal infections were evaluated. A formula based on the relationship between dose, vancomycin clearance and creatinine clearance was used to determine each patient's AUC24 h. 161 patients were included in the study. Median age was 34 years. The mean daily dose of vancomycin was 28 mg/kg/day. The median vancomycin C0 was 12.2 mg/mL, 17.3% were in the therapeutic range. The median AUC was 246.84 mg×h/L, only 8% achieved the target AUC24 h between 400 and 700 mg×h/L. Of these, 3 patients had C0 between 15 and 20 mg/mL and 9 patients had C0> 20 mg/mL. A poor correlation was found between C0 and AUC24 h = 0.37; r2 = 0.14; p<0.0001. In conclusion, vancomycin C0 correlated poorly with AUC24/MIC targets. C0 seems to underestimate AUC24 h. So, a patient specific AUC24/MIC may serve to predict efficacy while C0 can be used as indicators of possible nephrotoxicity and development of resistance. Key words: Vancomycin, area under the curve (AUC), trough concentration, minimum inhibitory concentration, therapeutic drug monitoring.

Optimizing Detection of MEC-Mediated Methicillin Resistance in Coagulase Negative Staphylococcus Species

Abstract Introduction/Objective Parenteral therapy for invasive staphylococcal infections often comprises lipo/glycopeptides for methicillin resistant (MR) organisms, with extended spectrum penicillins reserved for those confirmed as methicillin susceptible (MS). While phenotypic antimicrobial susceptibility testing (AST) using cefoxitin has high accuracy for differentiating MR/MS for S. aureus, the same, simple approach does not reliably distinguish resistance among all coagulase negative Staphylococcus species (CoNS). As such, clinicians may work under an assumption that MS CoNS cannot be reliably predicted by laboratories, leading to lipo/glycopeptide therapeutic use for invasive infections caused by both MR and MS isolates. To better inform laboratory practice, this study aimed to establish the accuracy of multiple phenotypic and genotypic tests for differentiation of MR/MS among commonly recovered CoNS species producing invasive infections. Methods/Case Report A convenience sample of 155 unique invasive CoNS isolates with historic Vitek 2 and/or disc diffusion (DD) AST results (~50% MR) were retrieved from frozen storage and tested by: (1) cefoxitin and oxacillin DD, (2) a lateral flow immunoassay for PBP2a without beta-lactam induction, and (3) a lab-developed PCR for mecA. A commercial real-time PCR for mecA/C was also employed for a subset of isolates. Results (if a Case Study enter NA) A total of 144 isolates belonging to 11 taxa were evaluated by all tests after accounting for missing, non-viable, and incorrectly cataloged isolates. Using PCR mecA/C detection as the reference standard, categorical agreement for MR/MS status was 95.5% (127/133) for original Vitek GP75 results, 98.6% (142/144) for DD interpreted using updated, species-specific CLSI guidelines, and 100% (144/144) for the lateral flow PBP2a assay. Six MR isolates from five different taxa that were repeatedly mecA-negative by lab-developed PCR confirmed as mecA/C-positive by a commercial assay. Conclusion Although all methods evaluated distinguish MR/MS CoNS with sufficient accuracy, definitive determination is best achieved using off-label/lab-developed PCR for mec or lateral flow immunoassay for PBP2a.

Exebacase: A Novel Approach to the Treatment of Staphylococcal Infections.

Lysins are bacteriophage-derived enzymes that degrade essential components of bacteria. Exebacase (Lysin CF-301) is an attractive antimicrobial agent because it demonstrates rapid bacteriolytic activity against staphylococcal species, including Staphylococcus aureus, has a low resistance profile, eradicates biofilms, and acts synergistically with other antibiotics. Combinations including exebacase and standard of care antibiotics represent an alternative to antibiotic monotherapies currently used to treat invasive staphylococcal infections. This manuscript reviews what is known about exebacase and explores how this novel agent may be used in the future to treat human bacterial pathogens.

Staphylococcus aureus injection drug use-associated bloodstream infections are propagated by community outbreaks of diverse lineages

BackgroundThe ongoing injection drug use (IDU) crisis in the United States has been complicated by an emerging epidemic of Staphylococcus aureus IDU-associated bloodstream infections (IDU-BSI).MethodsWe performed a case-control study comparing S. aureus IDU-BSI and non-IDU BSI cases identified in a large US Midwestern academic medical center between Jan 1, 2016 and Dec 21, 2019. We obtained the whole-genome sequences of 154 S. aureus IDU-BSI and 91 S. aureus non-IDU BSI cases, which were matched with clinical data. We performed phylogenetic and comparative genomic analyses to investigate clonal expansion of lineages and molecular features characteristic of IDU-BSI isolates.ResultsHere we show that patients with IDU-BSI experience longer durations of bacteremia and have lower medical therapy completion rates. In phylogenetic analyses, 45/154 and 1/91 contemporaneous IDU-BSI and non-IDU BSI staphylococcal isolates, respectively, group into multiple, unique clonal clusters, revealing that pathogen community transmission distinctively spurs IDU-BSI. Lastly, multiple S. aureus lineages deficient in canonical virulence genes are overrepresented among IDU-BSI, which may contribute to the distinguishable clinical presentation of IDU-BSI cases.ConclusionsWe identify clonal expansion of multiple S. aureus lineages among IDU-BSI isolates, but not non-IDU BSI isolates, in a community with limited access to needle exchange facilities. In the setting of expanding numbers of staphylococcal IDU-BSI cases consideration should be given to treating IDU-associated invasive staphylococcal infections as a communicable disease.

Dissecting the Human Response to Staphylococcus aureus Systemic Infections

Staphylococcus aureus is a common human commensal and the leading cause of diverse infections. To identify distinctive parameters associated with infection and colonization, we compared the immune and inflammatory responses of patients with a diagnosis of invasive S. aureus disease to healthy donors. We analyzed the inflammatory responses founding a pattern of distinctive cytokines significantly higher in the patients with invasive disease. The measure of antibody levels revealed a wide antibody responsiveness from all subjects to most of the antigens, with significantly higher response for some antigens in the invasive patients compared to control. Moreover, functional antibodies against toxins distinctively associated with the invasive disease. Finally, we examined the genomic variability of isolates, showing no major differences in genetic distribution compared to a panel of representative strains. Overall, our study shows specific signatures of cytokines and functional antibodies in patients with different primary invasive diseases caused by S. aureus. These data provide insight into human responses towards invasive staphylococcal infections and are important for guiding the identification of novel preventive and therapeutic interventions against S. aureus.

Rapid Detection of PBP2a in Staphylococci from Shortly Incubated Subcultures of Positive Blood Cultures by an Immunochromatographic Assay.

ABSTRACTStaphylococcus aureus, as well as coagulase-negative staphylococci (CoNS), can cause a wide range of human infections both in nosocomial and community settings. Βeta-lactams are the antibiotics of choice for the treatment of bloodstream infections (BSI) caused by these microorganisms. Resistance to virtually all β-lactams (also referred to as methicillin resistance) primarily results from the production of an alternative penicillin-binding protein (PBP2a) encoded by the mecA gene. While β-lactams are still used as first-line therapy against BSI caused by S. aureus, BSI with CoNS are usually treated with vancomycin due to the high prevalence of methicillin resistance. Rapid detection of methicillin resistance is thus critical for continuation or adjustment of the empirical therapy and therewith to improve the clinical outcome of the patients. The revised version of the immunochromatographic assay PBP2a SA culture colony test (SACCT) is a rapid, inexpensive, and easy method that enables reliable detection of PBP2a in mecA-positive staphylococcal isolates after18 to 24 h of incubation. Here, we evaluated the diagnostic performance of the SACCT using primary subcultures of spiked blood cultures after short incubation (4 to 6 h) and established a modified procedure with an equal analytical performance to that of longer-grown cultures. With the proposed method the SACCT can be employed for PBP2a detection from shortly incubated subcultures of clinically relevant staphylococcal isolates, thereby allowing more rapid and effective management of BSI caused by these organisms.IMPORTANCE Antibiotic resistance poses a major threat to health and incurs high economic costs worldwide. Rapid detection of resistance mechanisms can contribute to improving patient care and preventing the dissemination of antimicrobial resistance. Here, we describe a rapid method to detect the most important beta-lactam resistance mechanism (the plasmid-encoded alternative transpeptidase PBP2a) in staphylococcal isolates causing BSI. We show that, using a modified procedure, PBP2a can be reliably detected from primary subcultures of spiked blood cultures after short incubation (4 to 6 h) with a rapid, inexpensive, and simple immunochromatographic test (SACCT). We provide an accurate, inexpensive, and rapid method to facilitate appropriate management and control of infections in patients suffering from invasive staphylococcal infections.

English

Staphylococcus aureus is an important organism in orthopaedic practice as it is the most common cause of orthopaedic infections including surgical site infections (SSIs), osteomyelitis and septic arthritis. Carriers of S. aureus are predisposed to developing invasive staphylococcal infections. Knowledge of a patient’s carrier status before surgery together with interventions to eliminate the carrier state have been shown to reduce post-operative infections by S. aureus. A cross-sectional study carried out at Kenyatta National Hospital orthopaedic wards from 1 June 2019 to 30 September 2019. To determine the prevalence and factors associated with nasal colonisation by S. aureus among patients who have been admitted to undergo surgery. Consecutive sampling was done until the required sample size was achieved. Nasal swabs were taken from patients at admission for culture. Data concerning comorbid conditions as well as healthcare associated risk factors was collected. The overall prevalence of colonisation by S. aureus at admission was found to be 24.7% whereas the overall prevalence of colonisation by Methicillin Resistant S. aureus (MRSA) was found to be 3.03%. The prevalence of colonisation by S. aureus is high amongst patients being admitted to orthopaedic wards at Kenyatta National Hospital when compared with previous studies and amongst these are those who are colonised by MRSA. The prevalence of MRSA calls for the need of screening programmes to curtail spread within hospital and community settings.   Key words: Staphylococcus aureus, prevalence, nasal colonization, associated factors.

Mechanisms of Antibiotic Failure During Staphylococcus aureus Osteomyelitis.

Staphylococcus aureus is a highly successful Gram-positive pathogen capable of causing both superficial and invasive, life-threatening diseases. Of the invasive disease manifestations, osteomyelitis or infection of bone, is one of the most prevalent, with S. aureus serving as the most common etiologic agent. Treatment of osteomyelitis is arduous, and is made more difficult by the widespread emergence of antimicrobial resistant strains, the capacity of staphylococci to exhibit tolerance to antibiotics despite originating from a genetically susceptible background, and the significant bone remodeling and destruction that accompanies infection. As a result, there is a need for a better understanding of the factors that lead to antibiotic failure in invasive staphylococcal infections such as osteomyelitis. In this review article, we discuss the different non-resistance mechanisms of antibiotic failure in S. aureus. We focus on how bacterial niche and destructive tissue remodeling impact antibiotic efficacy, the significance of biofilm formation in promoting antibiotic tolerance and persister cell formation, metabolically quiescent small colony variants (SCVs), and potential antibiotic-protected reservoirs within the substructure of bone.

Measurement of Osteoblast Cytotoxicity Induced by S. aureus Secreted Toxins.

Staphylococcus aureus is a Gram-positive bacterium that is capable of infecting and inducing tissue pathology in nearly every organ system. The pathogenesis of staphylococcal infection is dictated, in part, through the production of toxins that induce cellular death through receptor-dependent and -independent mechanisms, thereby contributing to tissue injury. One common manifestation of invasive staphylococcal infection is osteomyelitis, or infection of bone. Osteomyelitis triggers extreme bone loss, in part, through production of secreted toxins. Cytotoxicity assays, therefore, can be instrumental in elucidating how S. aureus triggers bone loss, and such assays are rapidly adaptable to study of tissue damage across multiple cell types and organ systems. Additionally, in conjunction with proteomic approaches, cytotoxicity studies may help identify toxins capable of inducing host cell death. Here, a protocol is described for the isolation and stimulation of primary osteoblasts with S. aureus supernatants for rapid detection of cytotoxicity. This assay provides an excellent in vitro system to better understand how staphylococcal secreted toxins impact skeletal cell biology to induce changes in bone homeostasis.

Development of Biphenylthiazoles Exhibiting Improved Pharmacokinetics and Potent Activity Against Intracellular Staphylococcus aureus.

Exploring the structure-activity relationship (SAR) at the cationic part of arylthiazole antibiotics revealed hydrazine as an active moiety. The main objective of the study is to overcome the inherited toxicity associated with the free hydrazine. A series of hydrocarbon bridges was inserted in between the groups, to separate the two amino groups. Hence, the aminomethylpiperidine-containing analog 16 was identified as a new promising antibacterial agent with efficient antibacterial and pharmacokinetic profiles. Briefly, compound 16 outperformed vancomycin in terms of the antibacterial spectrum against vancomycin-resistant staphylococcal and enterococcal strains with minimum inhibitory concentrations (MICs) ranging from 2 to 4 μg/mL, which is a faster bactericidal mode of action, completely eradicating the high staphylococcal burden within 6-8 h, and it has a unique ability to completely clear intracellular staphylococci. In addition, the initial pharmacokinetic assessment confirmed the high metabolic stability of compound 16 (biological half-life >4 h); it had a good extravascular distribution and maintained a plasma concentration higher than the average MIC value for over 12 h. Moreover, compound 16 significantly reduced MRSA burden in an in vivo MRSA skin infection mouse experiment. These attributes collectively suggest that compound 16 is a good therapeutic candidate for invasive staphylococcal and enterococcal infections. From a mechanistic point of view, compound 16 inhibited undecaprenyl diphosphate phosphatase (UppP) with an IC50 value of 29 μM.

Demographic and Clinical Profile of Invasive Staphylococcal Infections in Children Admitted to Pediatric Intensive Care Unit: A Retrospective Study.

ObjectiveStaphylococcal infections are common cause of morbidity and mortality in pediatric intensive care unit (PICU). The objective of this study was to describe the clinical and microbial features, and outcome of patients with invasive staphylococcal infection.Materials and methodsWe conducted a retrospective chart review of the children admitted to PICU with invasive staphylococcal infections. Invasive staphylococcal infection was defined as clinical infection with isolation of Staphylococcus aureus from a normally sterile body site.ResultsA total of 50 children (1 month to 16 years) were identified with staphylococcal infections during the study period. There was male preponderance (75%) with high prevalence in school going children. Among these children, 36% (18) were coagulase-negative (CONS), which were excluded. Of the remaining, 64% (32) were coagulase-positive Staphylococcus aureus, 54% (27) were methicillin-resistant Staphylococcus aureus (MRSA), and 10% (5) were methicillin-susceptible Staphylococcus aureus (MSSA). Community-acquired staphylococcal infections were present in 24 children (CA-MRSA). Pneumonia with empyema was the most common 20 (62%) site of primary staphylococcal infection, followed by blood stream infection 9 (28%) and skin and soft tissue infection 3 (9%). Of the soft tissue infection, three were MRSA, with two had pyopericardium with infective endocarditis. Resistance in MSSA was found to be maximum to penicillin, erythromycin, and ciprofloxacin with no resistance with vancomycin.ConclusionThere is an increase incidence of MRSA among community-acquired staphylococcal infections requiring intensive care management. A larger study on clinical profile of Staphylococcus infection in pediatrics is urgently needed to define the exact magnitude of the problem.How to cite this articleLalitha AV, Rebello G, Chettri S, Reddy M. Demographic and Clinical Profile of Invasive Staphylococcal Infections in Children Admitted to Pediatric Intensive Care Unit: A Retrospective Study. Indian J Crit Care Med 2020;24(9):890–891.

Examining the Relationship Between Vancomycin Area Under the Concentration Time Curve and Serum Trough Levels in Adults With Presumed or Documented Staphylococcal Infections.

Investigations of the relationship between vancomycin trough concentrations and area under the concentration time curve (AUC) are growing, but still limited. The authors sought to determine vancomycin exposure among hospitalized adults with presumed or confirmed invasive staphylococcal infections using 2-level pharmacokinetic monitoring to inform changes to an institutional vancomycin dosing protocol. This was a retrospective observational study performed in 2 acute care hospitals. Adults prescribed vancomycin (therapeutic trough 15-20 mg/L) for a presumed or documented invasive staphylococcal infection were evaluated. Two steady-state serum vancomycin levels were used to determine each patient's 24-hour AUC to minimum inhibitory concentration ratio (AUC/MIC) using a non-Bayesian, equation-based approach. Patient demographics and crude clinical outcomes were also collected. Thirty-four patients were included in the study, with 2 patients having vancomycin levels drawn twice (36 sets of levels). Most patients were located in an intensive care unit (91.2%), and 85.3% of patients were prescribed vancomycin for bacteremia, pneumonia, or endocarditis. The mean ± SD vancomycin Cmin was 16.6 ± 6.1 mg/L, and the mean AUC/MIC was 588 ± 156 mg/L × hour. The rate of 24-hour vancomycin AUC/MIC target attainment was 91.2% (n = 31/34). Of the patients with a Cmin > 9 mg/L, 100% (n = 33) achieved AUC/MIC values >400 mg/L × hour and 93.9% were >500 mg/L × hour. There was a strong correlation between vancomycin Cmin and AUC24 hr (R = 0.731; P < 0.001). Targeting a vancomycin trough between 15 and 20 mg/L frequently resulted in an AUC/MIC greater than that thought to be necessary for efficacy optimization. Considering these findings alongside the practical challenges associated with wide-scale implementation of AUC monitoring, reducing the target trough as a means to prevent vancomycin overexposure warrants clinical consideration and further evaluation.

Innate Immunity to Staphylococcus aureus: Evolving Paradigms in Soft Tissue and Invasive Infections.

Staphylococcus aureus causes a wide range of diseases that together embody a significant public health burden. Aided by metabolic flexibility and a large virulence repertoire, S. aureus has the remarkable ability to hematogenously disseminate and infect various tissues, including skin, lung, heart, and bone, among others. The hallmark lesions of invasive staphylococcal infections, abscesses, simultaneously denote the powerful innate immune responses to tissue invasion as well as the ability of staphylococci to persist within these lesions. In this article, we review the innate immune responses to S. aureus during infection of skin and bone, which serve as paradigms for soft tissue and bone disease, respectively.

INVESTIGATION OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS NASAL CARRIAGE AND THE EFFECT OF HAND HYGIENE IN THE CARRIAGE

Ponte Academic JournalApr 2017, Volume 73, Issue 4 INVESTIGATION OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS NASAL CARRIAGE AND THE EFFECT OF HAND HYGIENE IN THE CARRIAGEAuthor(s): Sahra Kirmusaoglu ,Seyhun Yurdugul, Suphi VehidJ. Ponte - Apr 2017 - Volume 73 - Issue 4 doi: 10.21506/j.ponte.2017.4.23 Abstract:Background: Community-acquired Staphylococcus aureus (CA-S. aureus) strains gaining antibiotic resistance cause major health problems worldwide. Emerging of Methicillin resistant Staphylococcus aureus (MRSA) that are irresponsive to antibiotic treatments increased the prevalence of community- and hospital-acquired Staphylococcus aureus infections. Most of invasive staphylococcal infections are related with the nasal carriage of Staphylococcus. It is emphasized that hand and nasal carriages as a reservoir play an important role in the spread of these strains, as well as the community-acquired Staphylococcus aureus infections. In this study, we have investigated the prevalence of nasal and hand carriages of Staphylococcus aureus (S. aureus) especially MRSA among students who were enrolled in the university and the role of hand hygiene in the MRSA nasal carriage. The aims of this study are to overcome MRSA infections that are irresponsive to antimicrobial treatments by estimating the prevalence of S. aureus and MRSA nasal and hand carriages in terms of population and to reveal the effect of hand hygiene in staphylococcal nasal carriage. Methods: Nasal and hand samples that were collected from left and right anterior nares and palms, finger tips and between fingers of student, respectively. These samples were cultured and identified by MRSA. Results: We have found that the prevalence of MRSA nasal and hand carriages were 0.73% (1/137) and 6.57% (9/137), respectively. It is also revealed that the prevalence of being both S. aureus nasal and hand carriers was 2.92% (4/137) (p<0.05). Conclusion: The development of Staphylococcal nasal carriage was seem to be related with the hand hygiene (p<0.05). Detecting the epidemiology and understanding the risk factors such as Staphylococcus aureus nasal and hand carriages are important to be aware of the invasive infections and the potential for MRSA and other Staphylococcal infections. Download full text:Check if you have access through your login credentials or your institution Username Password

Bacteriophage-driven inhibition of biofilm formation in Staphylococcus strains from patients attending a Romanian reference center for infectious diseases.

The increasing burden of invasive biofilm-related staphylococcal infections has led to a dire need for new agents to prevent biofilm formation. Bacteriophages may hypothetically alter a biofilm through several mechanisms, including induction of depolymerizing enzymes and lysis of persistent bacteria. We have assessed the influence of commercially available bacteriophage cocktails on Staphylococcus spp. clinical strains viability and biofilm formation. We analyzed 83 staphylococcal strains from patients consecutively admitted to a Romanian infection reference center from October 2014 through May 2015; the strains were characterized by phenotypic and genetic tools for their resistance and virulence features and for their phyliation. Experiments were performed in triplicate. Methicillin-susceptible strains were significantly more susceptible to all tested phages: 1.7-fold higher susceptibility for PYO, 1.4-fold for INTESTI, 2.9-fold for PHAGYO, 2.7-fold for PHAGESTI and 3.9-fold for STAPHYLOCOCCAL; t030 strains were significantly more susceptible to PYO and INTESTI compared with t127 strains. We identified a significant decrease in biofilm formation in the presence of both low and high PYO and INTESTI concentrations (P < 0.001). In conclusion, Staphylococcus strains from Romania displayed fairly good susceptibility to commercially available bacteriophages. We have also ascertained there is phage-driven in vitro inhibition of biofilm formation, the results potentially impacting prevention of prosthetic infections.

Effect of Mupirocin Prophylaxis on MRSA Transmission and Invasive Staphylococcal Infections in a Neonatal Intensive Care Unit

Effect of Mupirocin Prophylaxis on MRSA Transmission and Invasive Staphylococcal Infections in a Neonatal Intensive Care Unit

Susceptibility trends including emergence of linezolid resistance among coagulase-negative staphylococci and meticillin-resistant Staphylococcus aureus from invasive infections

Multiresistance in staphylococci constitutes a major challenge for the antimicrobial chemotherapy of invasive infections such as bacteraemia or bone and joint infections (BJIs). A nationwide prospective study was performed to detect antimicrobial resistance trends among staphylococci causing invasive infections. Between October 2011 and February 2012, 367 meticillin-resistant Staphylococcus aureus (MRSA) and 695 coagulase-negative staphylococci (CoNS) were collected from 37 French hospitals, mainly from bacteraemia (59.9%) and osteoarticular infections (29.0%). Minimum inhibitory concentrations (MICs) were determined by broth microdilution, and specific screening and confirmation tests were performed to detect heterogeneous vancomycin-intermediate S. aureus (hVISA). Staphylococcal isolates exhibiting a linezolid MIC>4mg/L were further characterised to determinate their clonal relationships and the mechanism of resistance. MRSA exhibited additional resistances, including levofloxacin (82% associated resistance), gentamicin (13.6%), fusidic acid (13.6%) and rifampicin (6.5%), compromising oral step-down therapy in BJIs. Only two hVISA strains (0.5%) were identified. Among the CoNS, mainly Staphylococcus epidermidis (506/695; 72.8%), resistance to first- and second-line agents was more common. Linezolid resistance was identified in 10 CoNS (1.4%). The most frequent linezolid resistance mechanism was the G2576T mutation in 23S rDNA (9/10). For the first time in France, the cfr gene was found in five related sequence type 2 (ST2) S. epidermidis from two different hospitals, in association with ribosomal RNA and L3 ribosomal protein mutations. These national data must be considered when selecting empirical treatment for invasive staphylococcal infections. Moreover, the emergence and spread of linezolid-resistant CoNS carrying the cfr gene is of concern.

Increasing pyomyositis presentations among children in Queensland, Australia.

Pyomyositis, usually associated with tropical climates, occurs less commonly in temperate regions and is most often caused by Staphylococcus aureus. Several community-acquired methicillin-resistant S. aureus (CA-MRSA) clones have emerged in Queensland since the beginning of the century, and they now account for a significant proportion of invasive staphylococcal infection. This study aims to describe trends in the rate of presentation, and the clinical and diagnostic features of pyomyositis, and to determine if trends are attributed to the emergence of CA-MRSA or other factors. A 10-year retrospective cohort study of all patients presenting to Mater Children's Hospital in Brisbane, Queensland, with pyomyositis between July 2002 and July 2012, was conducted. Data were collected for clinical features, microbiology, diagnostic tests, management and outcome. Trends in incidence, and clinical and diagnostic features of pyomyositis were analyzed. Thirty-four cases of pyomyositis were identified. There was a male predominance (79%), and the vertebro-pelvic muscles were most often affected. The rate of pyomyositis increased significantly during the study period from a rate of 2.04 cases per 10,000 emergency department admissions in the first quarter of the study, to 8.73 cases per 10,000 in the final quarter (peak rate 13.5 cases per 10,000 in 2008). A causative organism was identified in 22 cases, most commonly methicillin-susceptible S. aureus with CA-MRSA identified in 4 cases. Patients who required surgical intervention had longer hospital admission, longer time to resolution of inflammatory markers and a higher risk of complication at follow-up. This study demonstrates an increasing incidence of pyomyositis in a temperate region, which is not attributable to the emergence of CA-MRSA. The reasons for this change in incidence are not clear.

Staphylococcus aureus keratinocyte invasion is mediated by integrin-linked kinase and Rac1.

Staphylococcus aureus is a major component of the skin microbiota and causes a large number of serious infections. S. aureus first interacts with epidermal keratinocytes to breach the epidermal barrier through mechanisms not fully understood. By use of primary keratinocytes from mice with epidermis-restricted Ilk gene inactivation and control integrin-linked kinase (ILK)-expressing littermates, we investigated the role of ILK in epidermal S. aureus invasion. Heat-killed, but not live, bacteria were internalized to Rab5- and Rab7-positive phagosomes, and incubation with keratinocyte growth factor increased their uptake 2.5-fold. ILK-deficient mouse keratinocytes internalized bacteria 2- to 4-fold less efficiently than normal cells. The reduced invasion by live S. aureus of ILK-deficient cells was restored in the presence of exogenous, constitutively active Rac1. Thus, Rac1 functions downstream from ILK during invasion. Further, invasion by S. aureus of Rac1-deficient cells was 2.5-fold lower than in normal cells. Paradoxically, staphylococcal cutaneous penetration of mouse skin explants with ILK-deficient epidermis was 35-fold higher than that of normal skin, indicating defects in epidermal barrier function in the absence of ILK. Thus, we identified an ILK-Rac1 pathway essential for bacterial invasion of keratinocytes, and established ILK as a key contributor to prevent invasive staphylococcal cutaneous infection.