Community-acquired methicillin-resistant Staphylococcus aureus in hospitalized adults and children without known risk factors

HAIR TRANSPLANTATION COMPLICATED BY METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS SEPSIS AND ENDOGENOUS ENDOPHTHALMITIS

PURPOSE

To describe a case of endogenous endophthalmitis as a complication from hair transplantation.

METHODS

Case report of a 53-year-old man with a history of recent hair transplantation.

RESULTS

The patient presented with a febrile illness and blurry vision 1 week after hair transplantation. Infectious workup included blood cultures positive for methicillin-resistant Staphylococcus aureus, and he was treated with IV antibiotics. Initial ocular examination demonstrated 20/30 and hand motions in the right and left eyes, respectively, with significant vitritis. He underwent vitreous tap and injections of vancomycin and dexamethasone in both eyes and removal of purulent staple from the site of recently transplanted hair. His ocular and systemic symptoms improved. Approximately 3 months after initial clearing of the initial infection he had recurrence of bacteremia that prompted repeat intravitreal and systemic antibiotics. His vision returned to baseline with mild residual optic nerve pallor and atrophic retinal changes in the left eye.

CONCLUSION

Hair transplantation is associated with minimal systemic complications, but in rare cases, sepsis is possible and can result in intraocular seeding causing endophthalmitis. MRSA endogenous endophthalmitis frequently results in negative vitreous taps and treatment outcomes in the literature have been shown to vary widely including a return to baseline vision as in the described case.

Native Aortic Valve Infective Endocarditis Secondary to Community-Acquired Methicillin-Resistant Staphylococcus aureus: A Case Report and Literature Review

Infective endocarditis (IE) refers to a microbial infection affecting either a heart valve or endocardium, resulting in tissue damage and the formation of vegetation. Native aortic valve endocarditis in children is rare and is associated with serious complications related to valvular insufficiency and systemic embolizations. As reports about community-acquired methicillin-resistant Staphylococcus aureus (MRSA) native aortic valve endocarditis in children are very scarce, we report this case along with a literature review about its complications and management. Here, we report the case of a seven-month-old infant who was previously healthy and presented with signs and symptoms of shock and systemic embolizations secondary to native aortic valve IE. His blood culture showed MRSA. He developed aortic valve insufficiency heart failure and multiorgan septic emboli that progressed to fatal refractory multiorgan failure. The management of complicated aortic valve endocarditis in children is challenging and needs a multidisciplinary team approach and prompt intervention.

Genome Sequences of Community Carriage Strains of Staphylococcus aureus from Yuma, Arizona

Staphylococcus aureus exists as a pathogen and commensal. Individuals with asymptomatic carriage serve as a reservoir for transmission and are at increased risk of infecting themselves. In order to characterize the genomic diversity of S. aureus circulating in the community, we sequenced 166 genomes collected from individuals in Yuma, AZ.

Empiric Vancomycin Reduction in a Pediatric Intensive Care Unit

BACKGROUND

At our institution, empirical vancomycin is overused in children with suspected bacterial community-acquired infections (CAIs) admitted to the PICU because of high community rates of methicillin-resistant Staphylococcus aureus (MRSA). Our goal was to reduce unnecessary vancomycin use for CAIs in the PICU.

METHODS

Empirical PICU vancomycin indications for suspected CAIs were developed by using epidemiological risk factors for MRSA. We aimed to reduce empirical PICU vancomycin use in CAIs by 30%. After retrospectively testing, the indications were implemented and monthly PICU empirical vancomycin use during baseline (May 2017-April 2018) and postintervention (May 2018-July 2019) periods. Education was provided to PICU providers, vancomycin indications were posted, and the antibiotic order set was revised. Statistical process control methods tracked improvement over time. Proven S aureus infections for which vancomycin was not empirically prescribed and linezolid or clindamycin use were balancing measures.

RESULTS

We identified 1620 PICU patients with suspected bacterial CAIs. Empirical vancomycin decreased from a baseline of 73% to 45%, a 38% relative reduction. No patient not prescribed empirical vancomycin later required the addition of vancomycin or other MRSA-targeted antibiotics. There was no change in nephrotoxicity or in the balancing measures.

CONCLUSIONS

Development of clear and concise recommendations, combined with clinician education and decision support via an order set, was an effective and safe strategy to reduce PICU vancomycin use. Retrospective validation of the recommendations with local data were key to obtaining PICU clinician buy in.

Genetic and phenotypic diversity of methicillin-resistant Staphylococcus aureus among Japanese inpatients in the early 1980s

To trace the linkage between Japanese healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) strains in the early 1980s and the 2000s onward, we performed molecular characterizations using mainly whole-genome sequencing. Among the 194 S. aureus strains isolated, 20 mecA-positive MRSA (10.3%), 8 mecA-negative MRSA (4.1%) and 3 mecA-positive methicillin-susceptible S. aureus (MSSA) (1.5%) strains were identified. The most frequent sequence type (ST) was ST30 (n = 11), followed by ST5 (n = 8), ST81 (n = 4), and ST247 (n = 3). Rates of staphylococcal cassette chromosome mec (SCCmec) types I, II, and IV composed 65.2%, 13.0%, and 17.4% of isolates, respectively. Notably, 73.3% of SCCmec type I strains were susceptible to imipenem unlike SCCmec type II strains (0%). ST30-SCCmec I (n = 7) and ST5-SCCmec I (n = 5) predominated, whereas only two strains exhibited imipenem-resistance and were tst-positive ST5-SCCmec II, which is the current Japanese HA-MRSA genotype. All ST30 strains shared the common ancestor strain 55/2053, which caused the global pandemic of Panton-Valentine leukocidin-positive MSSA in Europe and the United States in the 1950s. Conspicuously more heterogeneous, the population of HA-MRSA clones observed in the 1980s, including the ST30-SCCmec I clone, has shifted to the current homogeneous population of imipenem-resistant ST5-SCCmec II clones, probably due to the introduction of new antimicrobials.

Interaction of the antimicrobial peptide ∆M3 with the Staphylococcus aureus membrane and molecular models

Staphylococcus aureus is one of the most pathogenic bacteria; infections with it are associated with significant morbidity and mortality in health care facilities. Antimicrobial peptides are a promising next generation antibiotic with great potential against bacterial infections. In this study, evidence is presented of the biological and biophysical properties of the novel synthetic peptide ΔM3. Its antimicrobial activity against the ATCC 25923 and methicillin-resistant S. aureus strains was evaluated. The results showed that ΔM3 has activity in the same μM range as vancomycin. Biophysical studies were performed with palmitoyloleoylphosphatidylglycerol and cardiolipin liposomes loaded with calcein and used to follow the lytic activity of the peptide by fluorescence spectroscopy. On the other hand, ΔM3 was induced to interact with molecular models of the erythrocyte membrane buil-up of dimiristoylphosphatidylcholine and dimyristoylphosphatidylethanolamine, representative lipids of the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of ΔM3 to interact with the bacteria and erythrocyte model membranes was also evaluated by X-ray diffraction and differential scanning calorimetry. The morphological changes induced by the peptide to human erythrocytes were observed by scanning electron microscopy. Results with these techniques indicated that ΔM3 interacted with the inner monolayer of the erythrocyte membrane, which is rich in anionic lipids. Additionally, the cytotoxic effects of ΔM3 on red blood cells were evaluated by monitoring the hemoglobin release from erythrocytes. The results obtained from these different approaches showed ΔM3 to be a non-cytotoxic peptide with antibacterial activity.

Epidemiology of methicillin-resistant Staphylococcus aureus in a Japanese neonatal intensive care unit

BACKGROUND

There have been few reports on the genetic structure of the current population of methicillin-resistant Staphylococcus aureus (MRSA) from neonatal intensive care units (NICUs) in Japan. In the present study we conducted a molecular epidemiological analysis based on whole genome sequencing against MRSA strains in a Japanese NICU.

METHODS

We performed genotyping by whole genome sequencing, polymerase chain reaction-based typing of Staphylococcal cassette chromosome mec (SCCmec) and polymerase chain reaction-based open-reading frame typing against 57 MRSA strains from fecal or nasal specimens from NICU patients in Juntendo University Shizuoka Hospital in 2013-2014.

RESULTS

Forty-nine MRSA strains (86.0%) exhibited a clonal complex (CC) 1, and were divided into three sequence types (STs): ST2725 (n = 25), ST2764 (n = 21), and ST1 (n = 3). All CC1 MRSA strains had SCCmec IVa, and were resistant to new quinolones, which are limited in pediatric use, suggesting that these strains were derived from adult MRSA clones. Single nucleotide polymorphism differences of both ≤10 and >100 nucleotides were observed by pairwise, single nucleotide polymorphism analysis among ST2725 and ST2764 MRSA strains, respectively. Seven ST8 MRSA strains (12.2%) were isolated, and no strain exhibiting the Japanese hospital-associated MRSA genotype (ST5/SCCmec II) was isolated in this study.

CONCLUSIONS

Our molecular epidemiological analysis suggested that ST2725 and ST2764 MRSA strains had genetic diversity that could not be explained only by a recent transmission event in the NICU. These MRSA clones might be disseminated in other Japanese hospital facilities as new endemic clones. Our results are expected to contribute to the improvement of infection control measures of MRSA in NICUs.

Prevalence and associated factors for carriage of Enterobacteriaceae producing ESBLs or carbapenemase and methicillin-resistant Staphylococcus aureus in Hong Kong community

OBJECTIVES

We conducted a cross-sectional study in Hong Kong community to estimate the carriage prevalence, associated factors and genotypes of extended-spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E), methicillin-resistant Staphylococcus aureus (MRSA) and carbapenemase-producing Enterobacteriaceae (CPE).

METHODS

Seemingly healthy subjects were asked to provide nasal, handprint and stool samples from March to April 2017. Isolates were characterized by molecular methods. We used multivariable logistic regression models within a generalized estimating equation framework to identify risk factors for ESBL-E carriage. Characteristics of MRSA/CPE carriage were summarized.

RESULTS

The prevalence of ESBL-E, MRSA and CPE were 52.8% (104/197), 2.5% (5/197) and 0.5% (1/197) respectively. Most ESBL-E isolates were E. coli (85.6%; 113/132). Most ESBL genes belonged to bla_CTX-M-G9 (68.9%) and bla_TEM (53.0%) types. Self-reported antibiotic consumption (≥2 courses) in the past six months was associated with ESBL-E carriage (adjusted odds ratio: 4.71-5.47).

CONCLUSIONS

Abundance of ESBL-E in the community are causes of concern, and antibiotic use is associated with its carriage. Presence of MRSA and CPE in community members without clear healthcare exposure hints on a change in their epidemiology. This study establishes a baseline to formulate infection control policies and future studies in combating antimicrobial resistance.

Methicillin-Resistant Staphylococcus aureus Keratitis: Initial Treatment, Risk Factors, Clinical Features, and Treatment Outcomes

PURPOSE

To analyze the clinical characteristics, management choices, and outcomes of cases of methicillin-resistant Staphylococcus aureus (MRSA) keratitis.

DESIGN

Retrospective interventional case series.

METHODS

Fifty-two culture-proven (52 eyes) cases of MRSA keratitis diagnosed and treated at the University of Pittsburgh Medical Center were identified and reviewed.

RESULTS

The mean age was 66.6 ± 19.2 years with a median follow-up time of 147 days. The most prevalent risk factors included a history of ocular surgery (62.5%), topical corticosteroid use (35.4%), and dry eye syndrome (37.5%). There was a high burden of systemic disease (95.8%). The average presenting logarithm of minimal angle of resolution visual acuity was 1.7 ± 0.8 and the average final logarithm of minimal angle of resolution visual acuity was 1.2 + 1.0. Initial antibiotic treatment varied, with 20.8% receiving moxifloxacin alone, 20.8% receiving fortified cefazolin and fortified tobramycin together, and 12.5% receiving fortified vancomycin and fortified tobramycin, although other antibiotics were used during treatment if warranted. Surgical management was often required as 17.3% of eyes perforated: 13.5% required tarsorrhaphy, 5.8% required penetrating keratoplasty, and 1 eye was enucleated. When patients treated with fourth-generation fluoroquinolones were compared with those treated with fortified vancomycin, no difference in final visual acuity, treatment duration, or need for surgery was found.

CONCLUSION

MRSA causes fulminant keratitis often requiring surgical management with poor visual acuity outcomes. Poor ocular surface, topical corticosteroid use, previous ocular surgery, and/or a high burden of systemic disease were identified as common risk factors. Patients treated with fluoroquinolones in our study had comparable outcomes to those treated with fortified vancomycin; however, those treated with fortified vancomycin tended to have more severe ulcers at presentation.

The Bactericidal Activity of Temporin Analogues Against Methicillin Resistant Staphylococcus aureus

Staphylococcus aureus is a major infectious agent responsible for a plethora of superficial skin infections and systemic diseases, including endocarditis and septic arthritis. Recent epidemiological data revealed the emergence of resistance to commonly used antibiotics, including increased numbers of both hospital- and community-acquired methicillin-resistant S. aureus (MRSA). Due to their potent antimicrobial functions, low potential to develop resistance, and immunogenicity, antimicrobial peptides (AMPs) are a promising alternative treatment for multidrug-resistant strains. Here, we examined the activity of a lysine-rich derivative of amphibian temporin-1CEb (DK5) conjugated to peptides that exert pro-proliferative and/or cytoprotective activity. Analysis of a library of synthetic peptides to identify those with antibacterial potential revealed that the most potent agent against multidrug-resistant S. aureus was a conjugate of a temporin analogue with the synthetic Leu-enkephalin analogue dalargin (DAL). DAL-PEG-DK5 exerted direct bactericidal effects via bacterial membrane disruption, leading to eradication of both planktonic and biofilm-associated staphylococci. Finally, we showed that accumulation of the peptide in the cytoplasm of human keratinocytes led to a marked clearance of intracellular MRSA, resulting in cytoprotection against invading bacteria. Collectively, the data showed that DAL-PEG-DK5 might be a potent antimicrobial agent for treatment of staphylococcal skin infections.

Agr typing of Staphylococcus aureus species isolated from clinical samples in training hospitals of Isfahan and Shahrekord

Objective

As an opportunistic pathogen, Staphylococcus aureus is associated with serious nosocomial infections and growing antimicrobial resistance against beta-lactams among S. aureus strains has become a global challenge. The current study was designed to investigate the presence of agr genes among S. aureus strains recovered from clinical samples in university hospitals of Isfahan and Shahrekord.

Results

A total of 150 S. aureus isolates were screened by Disk diffusion method (DDM) and conventional PCR. The minimum (17.3%) and maximum (46%) antibiotic resistance rates were found in vancomycin and cefoxitin, respectively. The majority of our isolates were classified as agr type I followed by type II, type IV, and type III. The statistical analysis showed a significant correlation between agr type I and antibiotic resistance against cefoxitin and erythromycin (p = 0.04 and p = 0.03, respectively). Based on our findings, the agr typing could be considered an effective approach for molecular tracking of S. aureus infections.

N-(1,3,4-oxadiazol-2-yl)benzamide analogs, bacteriostatic agents against methicillin- and vancomycin-resistant bacteria

Various reports of multidrug-resistant bacteria that are immune to all available FDA-approved drugs demand the development of novel chemical scaffolds as antibiotics. From screening a chemical library, we identified compounds with antibacterial activity. The most potent compounds, F6-5 and F6, inhibited growth of various drug-resistant Gram-positive bacterial pathogens at concentrations ranging from 1 μg/mL to 2 μg/mL. Both compounds were active against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate and vancomycin-resistant S. aureus (VISA and VRSA respectively) and vancomycin-resistant Enterococcus faecalis (VRE). Resistance generation experiments revealed that MRSA could develop resistance to the antibiotic ciprofloxacin but not to F6. Excitingly, F6 was found to be non-toxic against mammalian cells. In a mouse skin wound infection model, F6 was equipotent to the antibiotic fusidic acid in reducing MRSA burden.

Development of a New Application for Comprehensive Viability Analysis Based on Microbiome Analysis by Next-Generation Sequencing: Insights into Staphylococcal Carriage in Human Nasal Cavities

The nasal carriage rate of Staphylococcus aureus in human is 25 to 30%, and S. aureus sporadically causes severe infections. However, the mechanisms underlying staphylococcal carriage remain largely unknown. In the present study, we constructed an rpoB-based microbiome method for staphylococcal species discrimination. Based on a microbiome scheme targeting viable cell DNA using propidium monoazide (PMA) dye (PMA microbiome method), we also developed a new method to allow the comprehensive viability analysis of any bacterial taxon. To clarify the ecological distribution of staphylococci in the nasal microbiota, we applied these methods in 46 nasal specimens from healthy adults. PMA microbiome results showed that Staphylococcaceae and Corynebacteriaceae were the most predominant viable taxa (average relative abundance: 0.435262 and 0.375195, respectively), and Staphylococcus epidermidis exhibited the highest viability in the nasal microbiota. Staphylococcus aureus detection rates from nasal specimens by rpoB-based conventional and PMA microbiome methods were 84.8% (39 of 46) and 69.5% (32 of 46), respectively, which substantially exceeded the values obtained by a culture method using identical specimens (36.9%). Our results suggest that Staphylococcaceae species, especially S. epidermidis, adapted most successfully to human nasal cavity. High detection of S. aureus DNA by microbiome methods suggests that almost all healthy adults are consistently exposed to S. aureus in everyday life. Furthermore, the large difference in S. aureus detection rates between culture and microbiome methods suggests that S. aureus cells frequently exist in a viable but nonculturable state in nasal cavities. Our method and findings will contribute to a better understanding of the mechanisms underlying carriage of indigenous bacteria.IMPORTANCE Metagenomic analyses, such as 16S rRNA microbiome methods, have provided new insights in various research fields. However, conventional 16S rRNA microbiome methods do not permit taxonomic analysis of only the viable bacteria in a sample and have poor resolving power below the genus level. Our new schemes allowed for viable cell-specific analysis and species discrimination, and nasal microbiome data using these methods provided some interesting findings regarding staphylococcal nasal carriage. According to our comprehensive viability analysis, the high viability of Staphylococcus species, especially Staphylococcus epidermidis, in human nasal carriage suggests that this taxon has adapted most successfully to human nasal tissue. Also, a higher detection rate of S. aureus DNA by microbiome methods (84.8%) than by a culture method (36.9%) suggests that almost all healthy adults are consistently exposed to Staphylococcus aureus in the medium and long term. Our findings will contribute to a better understanding of the mechanisms underlying the carriage of indigenous bacteria.

New Horizon on Community-Acquired Methicillin Resistant Staphylococcus Aureus (Ca-Mrsa) Skin and Soft Tissue Infection: Nanotechnology Antimicrobial Spray

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in community and hospital is increasing. The development of drug resistance may be attributed to the extensive use of antibiotics. Nanotechnology antimicrobial spray (NTAS), a physical antibacterial agent, is an alternative to antibiotic treatment on wound management. We report a case of MRSA associated skin abscess using NTAS in the wound management. NTAS possesses potent, broad spectrum antibacterial effect while carrying no risk of resistance and minimal adverse effect. Moreover, NTAS facilitates home wound management, thus reducing dependency on public health resources. Further studies are indicated to explore the clinical role of NTAS in an attempt to reduce the use of antibiotics. (Hong Kong j.emerg.med. 2011;18:432-436)

The epidemiology of Staphylococcus aureus carriage in patients attending inner city sexually transmitted infections and community clinics in Calgary, Canada

BACKGROUND

Although the nares represent the most common carriage site for traditional hospital-associated strains of Staphylococcus aureus (SA), the predominant site of carriage of SA in the community is less certain.

METHODS

We conducted a cross-sectional study in 285 patients attending sexually transmitted diseases and inner-city clinics to evaluate the prevalence, body site colonisation and risk factors associated with carriage of methicillin susceptible SA (MSSA). All isolates were characterized by pulsed field gel electrophoresis, staphylococcal cassette chromosome mec, staphylococcal protein A and multilocus sequence typing.

RESULTS

The prevalence of colonisation with SA was 57.5% (164/285); 162 (56.8%) participants were colonized with MSSA, and 4 (1.4%) with methicillin-resistant SA (MRSA), 2 of them were co-colonised with both MRSA and MSSA. The most common sites of colonisation were the throat (73.1%), nares (65.2%) and interdigital web spaces of the hand (21.3%). Three out of 4 MRSA isolates were USA300-MRSA strains. Twelve MSSA isolates were closely related to the USA300 CA-MRSA. We identified sexual behaviours such as having more than 6 heterosexual sexual partners in the last 6 months and trimming pubic hair to be independently associated with MSSA colonisation, and more specifically practicing oral sex as a risk factor for throat colonisation.

CONCLUSION

There is a high prevalence of MSSA carriage in this population, with a low prevalence of MRSA. The throat was the most common site of carriage and sexual behaviours were found to be risk factors for MSSA colonisation. Close strain relatedness of MSSA and USA300-MRSA isolates suggests either gain or loss of the SCCmec element, respectively.

The changing face of community-acquired methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, both in hospitalised patients with significant healthcare exposure and in patients without healthcare risk factors. Community-acquired methicillin-resistant S. aureus (CA-MRSA) are known for their rapid community transmission and propensity to cause aggressive skin and soft tissue infections and community-acquired pneumonia. The distinction between the healthcare-associated (HA)-MRSA and CA-MRSA is gradually fading owing to the acquisition of multiple virulence factors and genetic elements. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community or HA status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacotherapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-β-lactam antibacterial agents. This review aimed at illuminating the characteristic features of CA-MRSA, virulence factors, changing clinical settings and molecular epidemiology, insurgence into the hospital settings and therapy with drug resistance.

Prevalence of and Risk Factors for Carriage of Panton-Valentine Leukocidin–Positive Methicillin-ResistantStaphylococcus aureusAmong Residents and Staff of a German Nursing Home

The aims of this cross-sectional study were to determine the prevalence of and risk factors for carriage of Panton-Valentine leukocidin–producing methicillin-resistantStaphylococcus aureus(PVL-MRSA) in residents and personnel of a nursing home in Germany. In this study, PVL-MRSA carriage status among nursing home residents was associated with risk factors reflecting their dependence on nursing care. No specific risk factors were detected among staff.

Clinical and Laboratory Features of Community-Associated Methicillin-ResistantStaphylococcus aureus:Is It Really New?

Objective.

To review the epidemiologic and molecular characteristics of community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) in Detroit, Michigan, to assess the risk factors for infection and the response to therapy.

Design.

Prospective clinical and laboratory study of 2003-2004 CA-MRSA isolates. Molecular features were compared with CA-MRSA isolates from 1980.

Setting.

A 600-bed urban academic medical center.

Patients.

Twenty-three patients with CA-MRSA infections from 2003-2004 were evaluated. In addition, laboratory analysis was performed on 13 CA-MRSA isolates from 1980.

Main Outcome Measures.

Laboratory analysis of isolates included antimicrobial susceptibility testing, pulsed-field genotyping, testing for Panton-Valentine leukocidin (PVL) genes, and staphylococcal cassette chromosomemectyping.

Results.

Patients were predominantly young African American males and presented with skin and soft-tissue infections. All isolates were resistant to erythromycin and highly susceptible to other agents. Patients were generally treated successfully with combination incision and drainage and systemic antibiotics. Among the 23 isolates, 20 (87%) were the same strain. This strain carried the staphylococcal cassette chromosomemectype IV and PVL genes and is genetically identical to USA 300. Thirteen isolates of patients from our community who presented with CA-MRSA infections in 1980 represented a single clone that is unique compared with the 2003-2004 isolates. This strain carried staphylococcal cassette chromosomemectype IVA but did not carry the PVL genes.

Conclusions.

In our community, CA-MRSA is largely due to a single clone with a type IVmecgene and PVL gene. The type IV staphylococcal cassette chromosomemectype can be demonstrated in CA-MRSA isolates from a remote period, suggesting that earlier outbreaks were not related to healthcare exposure.

Blood-Retinal Barrier Compromise and Endogenous Staphylococcus aureus Endophthalmitis

PURPOSE

To test the hypothesis that blood-retinal barrier compromise is associated with the development of endogenous Staphylococcus aureus endophthalmitis.

METHODS

To compromise the blood-retinal barrier in vivo, streptozotocin-induced diabetes was induced in C57BL/6J mice for 1, 3, or 5 months. Diabetic and age-matched nondiabetic mice were intravenously injected with 108 colony-forming units (cfu) of S. aureus, a common cause of endogenous endophthalmitis in diabetics. After 4 days post infection, electroretinography, histology, and bacterial counts were performed. Staphylococcus aureus-induced alterations in in vitro retinal pigment epithelial (RPE) cell barrier structure and function were assessed by anti-ZO-1 immunohistochemistry, FITC-dextran conjugate diffusion, and bacterial transmigration assays.

RESULTS

We observed one bilateral infection in a control, nondiabetic animal (mean = 1.54 × 103 ± 1.78 × 10² cfu/eye, 7% incidence). Among the 1-month diabetic mice, we observed culture-confirmed unilateral infections in two animals (mean = 5.54 × 10² ± 7.09 × 10² cfu/eye, 12% incidence). Among the 3-month diabetic mice, infections were observed in 11 animals, three with bilateral infections (mean = 2.67 × 10² ± 2.49 × 10² cfu/eye, 58% incidence). Among the 5-month diabetic mice, we observed infections in five animals (mean = 7.88 × 10² ± 1.08 × 10³ cfu/eye, 33% incidence). In vitro, S. aureus infection reduced ZO-1 immunostaining and disrupted the barrier function of cultured RPE cells, resulting in diffusion of fluorophore-conjugated dextrans and transmigration of live bacteria across a permeabilized RPE barrier.

CONCLUSIONS

Taken together, these results indicated that S. aureus is capable of inducing blood-retinal barrier permeability and causing endogenous bacterial endophthalmitis in normal and diabetic animals.

The Type I Restriction Enzymes as Barriers to Horizontal Gene Transfer: Determination of the DNA Target Sequences Recognised by Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complexes 133/ST771 and 398

The Type I DNA restriction-modification (RM) systems of Staphylococcus aureus are known to act as a significant barrier to horizontal gene transfer between S. aureus strains belonging to different clonal complexes. The livestock-associated clonal complexes CC133/771 and CC398 contain Type I RM systems not found in human MRSA strains as yet but at some point transfer will occur. When this does take place, horizontal gene transfer of resistance will happen more easily between these strains. The reservoir of antibiotic resistance, virulence and host-adaptation genes present in livestock-associated MRSA will then potentially contribute to the development of newly evolving MRSA clones. The target sites recognised by the Type I RM systems of CC133/771 and CC398 were identified as CAG(N)5RTGA and ACC(N)5RTGA, respectively. Assuming that these enzymes recognise the methylation state of adenine, the underlined A and T bases indicate the unique positions of methylation. Target methylation points for enzymes from CC1 were also identified. The methylation points for CC1-1 are CCAY(N)5TTAA and those for CC1-2 are CCAY(N)6 TGT with the underline indicating the adenine methylation site thus clearing up the ambiguity noted previously (Roberts et al. 2013, Nucleic Acids Res 41:7472-7484) for the half sites containing two adenine bases.

Noninvasive target CT detection and anti-inflammation of MRSA pneumonia with theranostic silver loaded mesoporous silica

Antibiotics resistant MRSA related pneumonia lesions could be detected under CT guidance and controlled using theranostic reported herein.

Postpartum pyogenic sacroiliitis with methicillin-resistant Staphylococcus aureus in a healthy adult: A case report and review of the literature

OBJECTIVE

Back and buttock pain during pregnancy and the postpartum period generally improves spontaneously and rarely causes problems. However, such pain is infrequently induced by pyogenic sacroiliitis.

CASE REPORT

We herein present a 37-year-old female patient with no previous medical history who developed pyogenic sacroiliitis with severe right buttock pain 7 days after cesarean delivery. Arthrocentesis was performed, and a culture revealed the presence of methicillin-resistant Staphylococcus aureus (MRSA). After 6 weeks of treatment with intravenous antibiotics, her infection became quiescent. Eight cases of pyogenic sacroiliitis during the postpartum period and seven cases during pregnancy have been reported, but most of the causative pathogens were methicillin-sensitive Staphylococcus or Streptococcus species.

CONCLUSION

This report describes the first case of postpartum pyogenic sacroiliitis caused by MRSA. The frequency of infection with MRSA has recently increased, and community-acquired MRSA, which affects even healthy young people, has also become a problem. Antibiotics for empirical therapy after a diagnosis of pyogenic sacroiliitis, including anti-MRSA antibiotics, should be carefully selected.

Necrotizing pneumonia and septic shock: suspecting CA-MRSA in patients presenting to Canadian emergency departments

We report a case of fatal necrotizing pneumonia and sepsis caused by community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) in an otherwise well, 48-year-old Canadian man with type 2 diabetes mellitus who had travelled to Texas. Despite therapy that included intravenous antibiotics, intravenous immune globulin and other supportive measures, the patient succumbed to his illness. Recently, CA-MRSA pneumonia has been reported in several countries. The virulence of this organism may in part be related to its ability to produce toxins, such as Panton-Valentine leukocidin. As rates of CA-MRSA increase worldwide, physicians should be aware of the potential for MRSA to cause life-threatening infections in patients presenting to Canadian emergency departments (EDs). Necrotizing pneumonia caused by MRSA must be considered in the differential diagnosis of acute, severe respiratory illness. Early recognition of this syndrome in the ED may help physicians initiate appropriate antibiotic therapy in a timely manner.

Staphylococcus aureus infections: transmission within households and the community

Staphylococcus aureus, both methicillin susceptible and resistant, are now major community-based pathogens worldwide. The basis for this is multifactorial and includes the emergence of epidemic clones with enhanced virulence, antibiotic resistance, colonization potential, or transmissibility. Household reservoirs of these unique strains are crucial to their success as community-based pathogens. Staphylococci become resident in households, either as colonizers or environmental contaminants, increasing the risk for recurrent infections. Interactions of household members with others in different households or at community sites, including schools and daycare facilities, have a critical role in the ability of these strains to become endemic. Colonization density at these sites appears to have an important role in facilitating transmission. The integration of research tools, including whole-genome sequencing (WGS), mathematical modeling, and social network analysis, has provided additional insight into the transmission dynamics of these strains. Thus far, interventions designed to reduce recurrent infections among household members have had limited success, likely due to the multiplicity of potential sources for recolonization. The development of better strategies to reduce the number of household-based infections will depend on greater insight into the different factors that contribute to the success of these uniquely successful epidemic clones of S. aureus.

[(18)F]FDG-6-P as a novel in vivo tool for imaging staphylococcal infections

BACKGROUND

Management of infection is a major clinical problem. Staphylococcus aureus is a Gram-positive bacterium which colonises approximately one third of the adult human population. Staphylococcal infections can be life-threatening and are frequently complicated by multi-antibiotic resistant strains including methicillin-resistant S. aureus (MRSA). Fluorodeoxyglucose ([(18)F]FDG) imaging has been used to identify infection sites; however, it is unable to distinguish between sterile inflammation and bacterial load. We have modified [(18)F]FDG by phosphorylation, producing [(18)F]FDG-6-P to facilitate specific uptake and accumulation by S. aureus through hexose phosphate transporters, which are not present in mammalian cell membranes. This approach leads to the specific uptake of the radiopharmaceutical into the bacteria and not the sites of sterile inflammation.

METHODS

[(18)F]FDG-6-P was synthesised from [(18)F]FDG. Yield, purity and stability were confirmed by RP-HPLC and iTLC. The specificity of [(18)F]FDG-6-P for the bacterial universal hexose phosphate transporter (UHPT) was confirmed with S. aureus and mammalian cell assays in vitro. Whole body biodistribution and accumulation of [(18)F]FDG-6-P at the sites of bioluminescent staphylococcal infection were established in a murine foreign body infection model.

RESULTS

In vitro validation assays demonstrated that [(18)F]FDG-6-P was stable and specifically transported into S. aureus but not mammalian cells. [(18)F]FDG-6-P was elevated at the sites of S. aureus infection in vivo compared to uninfected controls; however, the increase in signal was not significant and unexpectedly, the whole-body biodistribution of [(18)F]FDG-6-P was similar to that of [(18)F]FDG.

CONCLUSIONS

Despite conclusive in vitro validation, [(18)F]FDG-6-P did not behave as predicted in vivo. However at the site of known infection, [(18)F]FDG-6-P levels were elevated compared with uninfected controls, providing a higher signal-to-noise ratio. The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection.

Comprehensive review of methicillin-resistant Staphylococcus aureus: screening and preventive recommendations for plastic surgeons and other surgical health care providers

BACKGROUND

Up to 2.3 million people are colonized with methicillin-resistant Staphylococcus aureus in the United States, causing well-documented morbidity and mortality. Although the association of clinical outcomes with community and hospital carriage rates is increasingly defined, less is reported about asymptomatic colonization prevalence among physicians, and specifically plastic surgeons and the subsequent association with the incidence of patient surgical-site infection.

METHODS

A review of the literature using the PubMed and Cochrane databases analyzing provider screening, transmission, and prevalence was undertaken. In addition, a search was completed for current screening and decontamination guidelines and outcomes.

RESULTS

The methicillin-resistant S. aureus carriage prevalence of surgical staff is 4.5 percent. No prospective data exist regarding transmission and interventions for plastic surgeons. No studies were found specifically looking at prevalence or treatment of plastic surgeons. Current recommendations by national organizations focus on patient-oriented point-of-care testing and intervention, largely ignoring the role of the health care provider. Excellent guidelines exist regarding screening, transmission prevention, and treatment both in the workplace and in the community. No current such guidelines exist for plastic surgeons.

CONCLUSIONS

No Level I or II evidence was found regarding physician screening, treatment, or transmission. Current expert opinion, however, indicates that plastic surgeons and their staff should be vigilant for methicillin-resistant S. aureus transmission, and once a sentinel cluster of skin and soft-tissue infections is identified, systematic screening and decontamination should be considered. If positive, topical decolonization therapy should be offered. In refractory cases, oral antibiotic therapy may be required, but this should not be used as a first-line strategy.

Methicillin-Resistant Staphylococcus aureus: A 5-Year Review of Surveillance Data in a Tertiary Care Hospital in Saudi Arabia

Background.

Staphylococcus aureus is an important pathogen that leads to serious infections in the community and in hospitals. Evidence has shown that the prevalence of infection and colonization with drug-resistant S. aureus, such as methicillin-resistant S. aureus (MRSA) and glycopeptide intermediately susceptible S. aureus, is increasing. Authorities must be aware of the prevalence of MRSA infection and colonization in their country in order to implement and monitor infection control policies that help curtail further emergence of this pathogen.

Objectives.

To examine the trend of hospital-acquired MRSA infection and colonization in a tertiary care institution in Saudi Arabia during a 5-year period in order to identify specific areas at high risk for MRSA transmission, and to review our MRSA decolonization procedure and outcomes.

Methods.

Surveillance data prospectively collected from January 1, 2000, through December 31, 2004, on hospital-acquired (HA) MRSA were analyzed, with an emphasis on the trend of HA-MRSA infection and colonization, areas of high transmission, risk factors, and effectiveness of the implemented decolonization policy.

Results.

During the study period, 442 cases of HA-MRSA infection and colonization were identified. Of these, 51.2% were infections, and 48.8% were colonizations. An increasing trend in the incidence rates of infection and colonization was noticed during the study period, and most cases were identified on the surgical ward (33.3%) and medical ward (32.1%). Of the 34 infected patients who underwent systematic decolonization, 35.3% were successfully decolonized, and of the 11 who underwent topical decolonization, 63.6% were successfully decolonized.

Conclusion.

The increasing trend of HA-MRSA infections has been a noticeable global problem. We identified a gradual increase in the rates of MRSA colonization and infection in a tertiary care center Saudi Arabia and recognize the importance of abiding by strict infection control policies, including hand hygiene and proper isolation practices. Continued surveillance for MRSA and other emerging multidrug-resistant pathogens is also needed.

A case control study of environmental and occupational exposures associated with methicillin resistant Staphylococcus aureus nasal carriage in patients admitted to a rural tertiary care hospital in a high density swine region

BACKGROUND

Distinct strains of methicillin resistant Staphylococcus aureus (MRSA) have been identified on livestock and livestock workers. Industrial food animal production may be an important environmental reservoir for human carriage of these pathogenic bacteria. The objective of this study was to investigate environmental and occupational exposures associated with nasal carriage of MRSA in patients hospitalized at Vidant Medical Center, a tertiary hospital serving a region with intensive livestock production in eastern North Carolina.

METHODS

MRSA nasal carriage was identified via nasal swabs collected within 24 hours of hospital admission. MRSA carriers (cases) were gender and age matched to non-carriers (controls). Participants were interviewed about recent environmental and occupational exposures. Home addresses were geocoded and publicly available data were used to estimate the density of swine in residential census block groups of residence. Conditional logistic regression models were used to derive odds ratio (OR) estimates and 95% confidence intervals (CI). Presence of the scn gene in MRSA isolates was assessed. In addition, multi locus sequence typing (MLST) of the MRSA isolates was performed, and the Diversilab® system was used to match the isolates to USA pulsed field gel electrophoresis types.

RESULTS

From July - December 2011, 117 cases and 119 controls were enrolled. A higher proportion of controls than cases were current workforce members (41.2% vs. 31.6%) Cases had a higher odds of living in census block groups with medium densities of swine (OR: 4.76, 95% CI: 1.36-16.69) and of reporting the ability to smell odor from a farm with animals when they were home (OR: 1.51, 95% CI: 0.80-2.86). Of 49 culture positive MRSA isolates, all were scn positive. Twenty-two isolates belonged to clonal complex 5.

CONCLUSIONS

Absence of livestock workers in this study precluded evaluation of occupational exposures. Higher odds of MRSA in medium swine density areas could reflect environmental exposure to swine or poultry.

Community-acquired disseminated methicillin-resistantStaphylococcus aureusinfection: case report and clinical implications

A 6-year-old girl with community-acquired disseminated infection caused by methicillin-resistant Staphylococcus aureus (MRSA) is described. She had sepsis, meningo-encephalitis, pyomyositis, osteomyelitis, pericarditis and pulmonary embolisation caused by a multi-resistant strain of MRSA. Vancomycin is not routinely recommended as the first-line antimicrobial agent for suspected Staphylococcus aureus infection; however, it should be considered pending susceptibility results in patients presenting with severe sepsis in areas where the prevalence of MRSA is high.

Predictors of hospitals with endemic community-associated methicillin-resistant Staphylococcus aureus

OBJECTIVE

We sought to identify hospital characteristics associated with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) carriage among inpatients.

DESIGN

 Prospective cohort study.

SETTING

 Orange County, California.

PARTICIPANTS

 Thirty hospitals in a single county.

METHODS

 We collected clinical MRSA isolates from inpatients in 30 of 31 hospitals in Orange County, California, from October 2008 through April 2010. We characterized isolates by spa typing to identify CA-MRSA strains. Using California's mandatory hospitalization data set, we identified hospital-level predictors of CA-MRSA isolation.

RESULTS

 CA-MRSA strains represented 1,033 (46%) of 2,246 of MRSA isolates. By hospital, the median percentage of CA-MRSA isolates was 46% (range, 14%-81%). In multivariate models, CA-MRSA isolation was associated with smaller hospitals (odds ratio [OR], 0.97, or 3% decreased odds of CA-MRSA isolation per 1,000 annual admissions; P < .001, hospitals with more Medicaid-insured patients (OR, 1.2; P = .002), and hospitals with more patients with low comorbidity scores (OR, 1.3; P < .001). Results were similar when restricted to isolates from patients with hospital-onset infection.

CONCLUSIONS

 Among 30 hospitals, CA-MRSA comprised nearly half of MRSA isolates. There was substantial variability in CA-MRSA penetration across hospitals, with more CA-MRSA in smaller hospitals with healthier but socially disadvantaged patient populations. Additional research is needed to determine whether infection control strategies can be successful in targeting CA-MRSA influx.

Infectious diseases causing diffuse alveolar hemorrhage in immunocompetent patients: a state-of-the-art review

Diffuse alveolar hemorrhage (DAH) represents a syndrome that can complicate many clinical conditions and may be life-threatening, requiring prompt treatment. It is recognized by the signs of acute- or subacute-onset cough, hemoptysis, diffuse radiographic pulmonary infiltrates, anemia, and hypoxemic respiratory distress. DAH is characterized by the accumulation of intra-alveolar red blood cells originating most frequently from the alveolar capillaries. It must be distinguished from localized pulmonary hemorrhage, which is most commonly due to chronic bronchitis, bronchiectasis, tumor, or localized infection. Hemoptysis, the major sign of DAH, may develop suddenly or over a period of days to weeks; this sign may also be initially absent, in which case diagnostic suspicion is established after sequential bronchoalveolar lavage reveals worsening red blood cell counts. The causes of DAH can be divided into infectious and noninfectious, the latter of which may affect immunocompetent or immunodeficient patients. Pulmonary infections are rarely reported in association with DAH, but they should be considered in the diagnostic workup because of the obvious therapeutic implications. In immunocompromised patients, the main infectious diseases that cause DAH are cytomegalovirus, adenovirus, invasive aspergillosis, Mycoplasma, Legionella, and Strongyloides. In immunocompetent patients, the infectious diseases that most frequently cause DAH are influenza A (H1N1), dengue, leptospirosis, malaria, and Staphylococcus aureus infection. Based on a search of the PubMed and Scopus databases, we review the infectious diseases that may cause DAH in immunocompetent patients.

Methicillin-resistant Staphylococcus aureus (MRSA) detected at four U.S. wastewater treatment plants

BACKGROUND

The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater.

OBJECTIVE

We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants.

METHODS

We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance.

RESULTS

We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.

CONCLUSIONS

Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater. Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.

The prevalence of methicillin-resistant staphylococcus aureus among out-of-hospital care providers and emergency medical technician students

OBJECTIVE

We compared the methicillin-resistant Staphylococcus aureus (MRSA) carrier rate among out-of-hospital care providers with greater than six months' experience in emergency medical services (EMS) care with that of emergency medical technician (EMT) students with two months or less of observation time as part of their clinical training.

METHODS

We conducted a prospective study utilizing a convenience sample of out-of-hospital care providers and EMT students in an urban EMS system operating in the Midwest during October and November 2006. One hundred thirty-four out-of-hospital care providers and 152 EMT students were tested for MRSA susceptibility using the cefoxitin disk diffusion method.

RESULTS

Contrary to our hypothesis, we did not find a statistically significant difference in MRSA nasal colonization between out-of-hospital care providers (4.5%; 95% confidence interval [CI] 1.0, 8.0) and EMT students (5.3%; 95% CI 1.7, 8.8). A subgroup analysis showed that among out-of-hospital care providers, paramedics had a higher rate of nasal colonization than EMTs (5.6% vs. 2.2%).

CONCLUSION

We found that out-of-hospital care providers and EMT students had higher nasal colonization rates than the reported rate for the U.S. population (0.084% at the time the study was conducted and 1.5% currently). It is imperative that both groups adhere to infection control practices.

Global fluoroquinolone resistance epidemiology and implictions for clinical use

This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.

Skin and soft tissue infections due to Panton-Valentine leukocidin producing Staphylococcus aureus

OBJECTIVE

The authors had for aim to describe the epidemiological and clinical characteristics, and the treatment of patients presenting with skin and soft tissue infections due to Panton-Valentine leukocidin (PVL) producing Staphylococcus aureus in the Nord-Pas-de-Calais (NPDC) region, North of France.

METHODS

We included patients presenting with PVL producing S. aureus infection from seven hospitals in the NPDC region, between February 2004 and April 2008. We retrospectively collected patient data using a standardized questionnaire. The features of patients presenting with skin and soft tissue were then analyzed.

RESULTS

PVL producing S. aureus was isolated from 64 patients. Fifty-four patients presented with skin and soft tissue infections. The mean age of patients was 23.8 years (63% male patients). The mean number of persons living with the infected patient was 4.5 (vs. 2.5 in NPDC). The lesions were abscesses with inflammatory signs in 64.8% of the cases (20% were necrotic). Among the patients, 70.3% carried a methicillin resistant strain. Antibiotics per os were used for 83.3% of patients; the first-line antibiotics were considered inadequate in 53.3% of the cases. Among the patients, 83.3% underwent surgery. Fourteen out of 38 patients with available data had been exposed to antibiotic therapy during the three months before hospital management.

CONCLUSION

Recent exposure to antibiotics and living with a high number of persons are reasons to suspect a PVL producing S. aureus infection in patients with skin abscess.

Community-Associated Methicillin-Resistant Staphylococcus aureus Infections in the Athlete

CONTEXT

Community-associated methicillin-resistant Staphlococcus aureus (CA-MRSA) has become of increasing concern in the athletic setting. Appropriate recognition, treatment, and prevention measures are all paramount to protect individual athletes and teamwide outbreaks.

EVIDENCE ACQUISITION

Relevant electronic databases (Medline or PubMed) through 2008 were searched. Articles and studies relevant to this topic were reviewed for pertinent clinical information.

STUDY TYPE

Clinical review.

RESULTS

CA-MRSA is an increasing problem both in the community at large and in the athletic population.

CONCLUSION

Early infections based on methicillin-resistant Staphlococcus aureus are often misidentified, leading to delay in appropriate treatment. A high level of suspicion, prompt recognition, and appropriate treatment can minimize morbidity associated with CA-MRSA. Careful selection of antibiotics in suspected cases is important, with more severe infections requiring hospitalization and intravenous antibiotics. Eradication of bacteria in colonized patients has not yet proven to be effective. Prevention of infections is multifaceted, and it includes education, proper personal hygiene, routine cleaning of equipment, and proper wound care.

In vitro activity and microbiological efficacy of tedizolid (TR-700) against Gram-positive clinical isolates from a phase 2 study of oral tedizolid phosphate (TR-701) in patients with complicated skin and skin structure infections

Tedizolid (TR-700, formerly torezolid) is the active moiety of the prodrug tedizolid phosphate (TR-701), a next-generation oxazolidinone, with high potency against Gram-positive species, including methicillin-resistant Staphylococcus aureus (MRSA). A recently completed randomized, double-blind phase 2 trial evaluated 200, 300, or 400 mg of oral tedizolid phosphate once daily for 5 to 7 days in patients with complicated skin and skin structure infections. This report examines the in vitro activity of tedizolid and Zyvox (linezolid) against Gram-positive pathogens isolated at baseline and describes the microbiological and clinical efficacy of tedizolid. Of 196 isolates tested, 81.6% were S. aureus, and of these, 76% were MRSA. The MIC(50) and MIC(90) of tedizolid against both methicillin-susceptible S. aureus (MSSA) and MRSA were 0.25 μg/ml, compared with a MIC(50) of 1 μg/ml and MIC(90) of 2 μg/ml for linezolid. For coagulase-negative staphylococci (n = 7), viridans group streptococci (n = 15), and beta-hemolytic streptococci (n = 3), the MICs ranged from 0.03 to 0.25 μg/ml for tedizolid and from 0.12 to 1 μg/ml for linezolid. The microbiological eradication rates at the test-of-cure visit (7 to 14 days posttreatment) in the microbiologically evaluable population (n = 133) were similar in all treatment groups, with overall eradication rates of 97.7% for all pathogens, 97.9% for MRSA, and 95.7% for MSSA. The clinical cure rates for MRSA and MSSA infections were 96.9% and 95.7%, respectively, across all dose groups. This study confirms the potent in vitro activity of tedizolid against pathogenic Gram-positive cocci, including MRSA, and its 4-fold-greater potency in comparison with linezolid. All dosages of tedizolid phosphate showed excellent microbiological and clinical efficacy against MRSA and MSSA.

Immune-activating properties of Panton-Valentine leukocidin improve the outcome in a model of methicillin-resistant Staphylococcus aureus pneumonia

The Panton-Valentine leukocidin (PVL) is a cytotoxin expressed by many methicillin-resistant Staphylococcus aureus (MRSA) strains that cause community-acquired infections (CA-MRSA). Its role in virulence however, is controversial, with clinical data suggesting that PVL-producing strains may cause less severe disease in humans. PVL is capable of lysing human white blood cells, but at sublytic amounts, PVL can activate protective host immunity in the absence of cell damage. The concentration-dependent reactions it elicits from host cells could be the reason for seemingly contradictory results about PVL's role in virulence. We hypothesized that a key to understanding PVL's action on host cells and, possibly, outcomes from infection is the amount of toxin present, a hypothesis previously supported in studies using a low-inoculum skin infection model, where low levels of PVL augmented innate immune resistance to infection. Here, we present additional data supporting this hypothesis using a mouse model of MRSA pneumonia, wherein we found increased virulence of isogenic Δpvl strains and further confirmed PVL's capacity to activate proinflammatory responses from mouse and human neutrophils and pulmonary cells. Activation was measured as the production of phosphorylated p38 mitogen-activated protein kinase (MAPK) and proinflammatory cytokines interleukin-8 (IL-8) and KC (from human and mouse cells, respectively), as well as the release of antibacterial factors. Conversely, PVL lowered the levels of tumor necrosis factor alpha (TNF-α) produced in active pulmonary infection, while low doses induced apoptosis, suggesting that PVL also has the capacity to regulate inflammation. Our data indicate that, independent of its cytotoxic effects, PVL also plays an important and positive immunomodulatory role during MRSA infections.

Resistance surveillance studies: a multifaceted problem--the fluoroquinolone example

INTRODUCTION

This review summarizes data on the fluoroquinolone resistance epidemiology published in the previous 5 years.

MATERIALS AND METHODS

The data reviewed are stratified according to the different prescription patterns by either primary- or tertiary-care givers and by indication. Global surveillance studies demonstrate that fluoroquinolone- resistance rates increased in the past several years in almost all bacterial species except Staphylococcus pneumoniae and Haemophilus influenzae causing community-acquired respiratory tract infections (CARTIs), as well as Enterobacteriaceae causing community-acquired urinary tract infections. Geographically and quantitatively varying fluoroquinolone resistance rates were recorded among Gram-positive and Gram-negative pathogens causing healthcare-associated respiratory tract infections. One- to two-thirds of Enterobacteriaceae producing extended-spectrum β-lactamases (ESBLs) were fluoroquinolone resistant too, thus, limiting the fluoroquinolone use in the treatment of community- as well as healthcare-acquired urinary tract and intra-abdominal infections. The remaining ESBL-producing or plasmid-mediated quinolone resistance mechanisms harboring Enterobacteriaceae were low-level quinolone resistant. Furthermore, 10-30 % of H. influenzae and S. pneumoniae causing CARTIs harbored first-step quinolone resistance determining region (QRDR) mutations. These mutants pass susceptibility testing unnoticed and are primed to acquire high-level fluoroquinolone resistance rapidly, thus, putting the patient at risk. The continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some current guidelines for the treatment of intra-abdominal infections or even precludes the use of fluoroquinolones in certain indications like gonorrhea and pelvic inflammatory diseases in those geographic areas in which fluoroquinolone resistance rates and/or ESBL production is high. Fluoroquinolone resistance has been selected among the commensal flora colonizing the gut, nose, oropharynx, and skin, so that horizontal gene transfer between the commensal flora and the offending pathogen as well as inter- and intraspecies recombinations contribute to the emergence and spread of fluoroquinolone resistance among pathogenic streptococci. Although interspecies recombinations are not yet the major cause for the emergence of fluoroquinolone resistance, its existence indicates that a large reservoir of fluoroquinolone resistance exists. Thus, a scenario resembling that of a worldwide spread of β-lactam resistance in pneumococci is conceivable. However, many resistance surveillance studies suffer from inaccuracies like the sampling of a selected patient population, restricted geographical sampling, and undefined requirements of the user, so that the results are biased. The number of national centers is most often limited with one to two participating laboratories, so that such studies are point prevalence but not surveillance studies. Selected samples are analyzed predominantly as either hospitalized patients or patients at risk or those in whom therapy failed are sampled; however, fluoroquinolones are most frequently prescribed by the general practitioner. Selected sampling results in a significant over-estimation of fluoroquinolone resistance in outpatients. Furthermore, the requirements of the users are often not met; the prescribing physician, the microbiologist, the infection control specialist, public health and regulatory authorities, and the pharmaceutical industry have diverse interests, which, however, are not addressed by different designs of a surveillance study. Tools should be developed to provide customer-specific datasets.

CONCLUSION

Consequently, most surveillance studies suffer from well recognized but uncorrected biases or inaccuracies. Nevertheless, they provide important information that allows the identification of trends in pathogen incidence and antimicrobial resistance.

Novel phenol-soluble modulin derivatives in community-associated methicillin-resistant Staphylococcus aureus identified through imaging mass spectrometry

Staphylococcus aureus causes a wide range of human disease ranging from localized skin and soft tissue infections to potentially lethal systemic infections. S. aureus has the biosynthetic ability to generate numerous virulence factors that assist in circumventing the innate immune system during disease pathogenesis. Recent studies have uncovered a set of extracellular peptides produced by community-associated methicillin-resistant S. aureus (CA-MRSA) with homology to the phenol-soluble modulins (PSMs) from Staphylococcus epidermidis. CA-MRSA PSMs contribute to skin infection and recruit and lyse neutrophils, and truncated versions of these peptides possess antimicrobial activity. In this study, novel CA-MRSA PSM derivatives were discovered by the use of microbial imaging mass spectrometry. The novel PSM derivatives are compared with their parent full-length peptides for changes in hemolytic, cytolytic, and neutrophil-stimulating activity. A potential contribution of the major S. aureus secreted protease aureolysin in processing PSMs is demonstrated. Finally, we show that PSM processing occurs in multiple CA-MRSA strains by structural confirmation of additional novel derivatives. This work demonstrates that IMS can serve as a useful tool to go beyond genome predictions and expand our understanding of the important family of small peptide virulence factors.

CD4 T cell antigens from Staphylococcus aureus Newman strain identified following immunization with heat-killed bacteria

Staphylococcus aureus is a commensal bacterium associated with the skin and mucosal surfaces of humans and animals that can also cause chronic infection. The emergence of antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA) and strains causing chronic intramammary infections (IMI) in cows results in severe human and livestock infections. Conventional approaches to vaccine development have yielded only a few noneffective vaccines against MRSA or IMI strains, so there is a need for improved vaccine development. CD4 T lymphocytes are required for promoting gamma interferon (IFN-γ) mediated immunoglobulin isotype switching in B lymphocytes to produce high-affinity IgG antibodies and IFN-γ-mediated phagocyte activation for an effective resolution of bacterial infection. However, the lack of known CD4 T cell antigens from S. aureus has made it difficult to design effective vaccines. The goal of this study was to identify S. aureus proteins recognized by immune CD4 T cells. Using a reverse genetics approach, 43 antigens were selected from the S. aureus Newman strain. These included lipoproteins, proteases, transcription regulators, an alkaline shock protein, conserved-domain proteins, hemolysins, fibrinogen-binding protein, staphylokinase, exotoxin, enterotoxin, sortase, and protein A. Screening of expressed proteins for recall T cell responses in outbred, immune calves identified 13 proteins that share over 80% sequence identity among MRSA or IMI strains. These may be useful for inclusion in a broadly protective multiantigen vaccine against MRSA or IMI.

Community-acquired methicillin-resistant Staphylococcus aureus hand infections in the pediatric population

PURPOSE

Recent studies have reported rates of methicillin-resistant Staphylococcus aureus (MRSA) hand infections in patients without risk factors ranging from 26% to 73%. The purpose of our study was to review a large series of pediatric hand infections to determine the rate of MRSA and identify potential risk factors.

METHODS

A retrospective review was performed on patients younger than 15 who were seen for hand infections (2001-2010). Patients were categorized according to medical problems, need for operation, abscess location, and mechanism of injury. Potential MRSA risk factors were assessed using a multivariate-regression model.

RESULTS

During the 10-year period, 415 patients were seen for hand infections. A total of 146 patients met the inclusion criteria: patients younger than 15 years of age who presented to the plastic surgery service requiring consultation for hand infections. The overall prevalence of MRSA-positive cultures was found to be 30%. The prevalence of MRSA was 29% in healthy patients and 0% in immunocompromised patients. The prevalence of MRSA increased in a linear fashion from patients without documentation of incision and drainage procedures to patients adequately treated with bedside incision and drainage to patients who required surgical drainage. There was a trend toward a higher prevalence of MRSA in deep space abscesses compared to other abscesses. Patients with a history of trauma and previous MRSA infections had a higher rate of MRSA than other patients.

CONCLUSIONS

Traditionally, MRSA has been associated with hospitalization, intravenous drug use, recent antibiotic use, and compromised immunity. In our study, more severe, deep-space abscesses requiring surgical drainage and patients with a history of previous MRSA infections were found to have a higher prevalence of MRSA. The immunocompromised patients had no cases of MRSA and had higher incidences of less virulent bacterial infections. This suggests that acquisition of community-acquired MRSA skin and soft tissue infections in children and adolescents might not be associated with the traditional risk factors.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Combined topical and oral antimicrobial therapy for the eradication of methicillin-resistant Staphylococcus aureus (MRSA) colonization in hospitalized patients

OBJECTIVE

How to eradicate methicillin-resistant Staphylococcus aureus (MRSA) colonization in hospitalized patients is uncertain. We reviewed our experience with MRSA decolonization therapy in hospitalized patients.

SETTING

An 1100-bed, university-affiliated tertiary care teaching hospital in Toronto, Ontario.

DESIGN

Retrospective chart review of 207 adult inpatients with MRSA colonization hospitalized between February 1996 and March 1999.

INTERVENTIONS

All patients with MRSA colonization were assessed for possible decolonization therapy with a combination of 4% chlorhexidine soap for bathing and washing, 2% mupirocin ointment applied to the anterior nares three times/day, rifampin (300 mg twice daily) and either trimethoprim/sulfamethoxazole (160 mg/800 mg twice daily) or doxycycline (100 mg twice daily). This treatment was given for seven days.

RESULTS

A total of 207 hospitalized patients with MRSA colonization were identified and 103 (50%) received decolonization therapy. Patients who received decolonization therapy were less likely than untreated patients to have intravenous (P=0.004) or urinary catheters (P<0.001), or extranasal sites of colonization (P=0.001). Successful decolonization was achieved in 90% of the 43 patients who were available for at least three months of follow-up.

CONCLUSIONS

Combined topical and oral antimicrobial therapy was found to be effective in eradicating MRSA colonization in selected hospitalized patients, especially those without indwelling medical devices or extranasal sites of colonization.

Risk factors for household transmission of community-associated methicillin-resistant Staphylococcus aureus

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a community pathogen. Community-associated (CA) MRSA infections have occurred among multiple members of a household. We describe the incidence of and risk factors for MRSA colonization among household contacts of children with CA-MRSA infections.

METHODS

MRSA-infected children <18 years of age who lacked established healthcare-associated MRSA risk factors were identified through surveillance at 12 Minnesota hospital laboratories. Nasal swab specimens and information on medical history and hygiene behaviors were collected from case-patients and enrolled household contacts during home visits. S. aureus isolates obtained from nasal cultures were screened for oxacillin resistance.

RESULTS

In all, 236 households consisting of 236 case-patients and 712 household contacts were enrolled. Home visits were conducted on an average of 69 days after the onset of symptom in case-patients (range: 16-178 days). Twenty-nine (13%) case-patients and 82 (12%) household contacts had MRSA nasal colonization. Nasal MRSA colonization in ≥ 1 household contact occurred in 58 (25%) households. Household contacts who assisted the case-patient to bathe or who shared balms/ointments/lotion with the case-patient were more likely to be colonized (P < 0.01, P < 0.05), whereas those who reported using antibacterial versus nonantibacterial soap for hand washing were less likely to be colonized (P < 0.05) with MRSA clonally related to the case-patient infection isolate.

CONCLUSIONS

Only 13% of case-patients had MRSA nasal colonization on an average of 69 days after their initial MRSA infection. CA-MRSA colonization may be short-lived or may occur at non-nasal sites. One quarter of households had at least one household contact colonized with MRSA. Modifiable behaviors, such as sharing personal items, may contribute to transmission.