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A new topical model of Staphylococcus corneal infection in the mouse.

PURPOSE: To establish, in the scarified mouse eye, a new model of Staphylococcus aureus keratitis suitable for studies of pathogenesis and host defense mechanisms. METHODS: Corneas of three strains of mice (BALB/c, A/J, and C57BL/6) were scarified and inoculated with S. aureus strain 8325-4. Mice underwent slit lamp examination (SLE) at 1, 3, 5, 7, and 9 days after infection and were killed. Histopathologic analyses, determination of bacterial colony-forming units (CFU), and myeloperoxidase (MPO) activity assays were performed at each time point. RESULTS: S. aureus keratitis developed in both BALB/c and A/J strains of mice, but not in C57BL/6. The BALB/c and A/J strains demonstrated greater susceptibility to infection, as evidenced by significantly higher SLE scores and more viable bacteria per infected eye than in C57BL/6 mice at 5, 7, and 9 days after infection (P <or= 0.0001). Histopathologic analysis and MPO assays of infected A/J mice both revealed an influx of polymorphonuclear leukocytes (PMNs). Histology demonstrated presence of leukocytes in the aqueous humor, migration of PMNs into infected tissue, corneal erosion, and edema in the eyes of infected A/J mice. Whereas infected BALB/c mice demonstrated both PMN migration and corneal edema, eyes of infected C57BL/6 mice failed to show even mild histopathologic changes. CONCLUSIONS: These studies demonstrate the establishment of Staphylococcus keratitis in the mouse eye. This model should provide for a large range of future studies that are currently unavailable in the rabbit keratitis model, particularly those requiring a genetically altered host or specific immunologic reagents.

Animals↗

Methicillin-resistant Staphylococcus aureus infections in vascular surgery: increasing prevalence.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a virulent organism that causes substantial infection-related morbidity and mortality in hospitalized patients. For example, MRSA infection of prosthetic vascular grafts can be limb- and life-threatening in surgical patients. We investigated the incidence of MRSA infection in vascular surgical patients who developed postoperative infectious complications. METHODS: Prospective data (including procedure, nature of complication, and outcome) were collected on all vascular surgery patients (n = 772) over a two-year period from January, 2000, to December, 2001. The study cohort included all patients who developed postoperative complications (n = 119, 15.4%), including infection, unplanned or prolonged intubation, metabolic abnormalities, and myocardial ischemia. Bacteriologic data of all clinical cultures were reviewed and infection-related outcomes were examined. RESULTS: Hospital-acquired infection occurred in 79 (66.4%) of 119 patients who developed postoperative complications. Review of microbiology data (total, 197 bacterial isolates) confirmed that gram-positive organisms were the leading cause of infections, with 120 gram-positive isolates (60.9%). Of the gram-positive isolates, S. aureus was the most common pathogen, isolated in 73 (60.8%) cultures. The single most prevalent organism was MRSA, identified in 42 of 73 (57.5%) of cultures. The site of MRSA infection was confirmed to be the surgical site (54.8%), sputum (17.0%), blood (14.3%), urine (9.5%), peritoneal fluid (2.4%), or catheter insertion site (2.4%). Only four patients had prior MRSA infection or colonization. Prosthetic vascular grafts were placed in 51 (42.9%) of the 119 vascular patients, and 26 patients (51.6%) acquired MRSA infection. Graft removal was required in three patients due to infection (MRSA infection in two patients, Pseudomonas aeruginosa in one patient). Forty percent of patients with MRSA infection required an amputation as their surgical procedure. No patient died of MRSA bacteremia during the study period. Mean hospital length of stay (LOS) was longer in patients with MRSA infection (29.6 d vs. 22.7 days, range 2-174 days, p < 0.05) compared to the total study cohort of vascular patients with postoperative infections. CONCLUSIONS: Methicillin-resistant S. aureus has emerged as the leading cause of postoperative infection in vascular surgery patients, and is associated with substantial morbidity, increased hospital LOS, and higher incidences of amputation and graft removal. Greater emphasis on preoperative screening protocols for MRSA colonization is warranted, in conjunction with aggressive infection control measures, alteration of preoperative prophylactic antimicrobial use in MRSA-colonized patients, and meticulous postoperative surveillance for MRSA infection. Furthermore, antimicrobial treatment of postoperative infectious complications in vascular surgery patients should include empiric coverage for MRSA in institutions where MRSA is endemic.

Adult↗

A case of isolated and transient splenial lesion of the corpus callosum associated with disseminated Staphylococcus aureus infection.

We report a 20-year-old man who presented with temporary encephalopathy. Serial brain MRI revealed an isolated and transient splenial lesion of the corpus callosum (SCC). He was subsequently diagnosed with septic metastasis of Staphylococcus aureus (S. aureus) involving both lungs and multiple joints; however, there was no indication of S. aureus involvement of the meninges or brain parenchyma in CSF and MRI studies. Within 24 h of presentation, the serum sodium concentration and effective osmolality changed by approximately 10 mmol/L and 25 mOsm/kg H(2)O, respectively. On the basis of the MRI findings, the changes in electrolyte concentration, and a review of relevant literature, an isolated and transient SCC in this case might be related to osmotic demyelination caused by fluid imbalance rather than direct invasion of S. aureus.

Adult↗

[Infection by Staphylococcus lugdunensis: clinico-microbiologic characterization of 25 cases].

INTRODUCTION: S. lugdunensis is a recently described staphylococcal species with morphologic characteristic similar to those of S. aureus. It has been associated to a variety of clinical infections. In this paper we present the clinical and microbiological features of S. lugdunensis isolates from 25 patients. MATERIALS AND METHODS: We have studied the S. lugdunensis isolates obtained from clinical specimens in our laboratory over a three-year period, 1994-96. For all isolates we determined the presence of clumping factor, Dnase, free coagulase in tube and ornithine decarboxylase (ODC). Full identification was performed with API ID32-Staph strips (bioMérieux) and antimicrobial susceptibility with commercial broth microdilution MIC panels (PASCO System, Difco). RESULTS: We obtained 38 S. lugdunensis isolates from 25 patients. The clinical specimens were: breast exudate/pus (8), blood (5), surgical wound (2), urine (2), nasal exudate (2), peritoneal fluid (1), pleural fluid (1), venous catheter (1), Tenckoff catheter (1), bartholin pus (1), ulcer (1). The isolates were considered clinically significant in 20 patients, whereas those of the remaining 5 patients were considered mere colonizers. All isolates were clumping factor (+), ODC (+), Dnase (-) and free coagulase (-). 16/23 (69.5%) were susceptible to penicillin and only one isolate was methicillin-resistant. CONCLUSIONS: We have isolated S. lugdunensis from a great variety of clinical specimens (blood, sterile body fluids, urine, skin, abscesses and nasal mucosa). It is specially remarkable the association with non-puerperal mastitis. The presence of clumping factor in all isolates can easily lead to misidentification as S. aureus. The ODC test appears as a good screening method for detecting S. lugdunensis. S. lugdunensis shows a good susceptibility to betalactamic an other antimicrobial agents.

Adult↗

Nosocomial infections by Staphylococcus epidermidis: how a commensal bacterium turns into a pathogen.

Staphylococcus epidermidis is a commensal bacterium of the human skin. However, S. epidermidis and other coagulase-negative staphylococci (CNS) emerge also as common nosocomial pathogens infecting immunocompromized patients carrying medical devices. Antibiotic resistance and the ability of many nosocomial S. epidermidis isolates to form biofilms on inert surfaces make these infections hard to treat. Epidemiological analyses using multilocus sequence typing (MLST) and genetic studies suggest that S. epidermidis isolates in the hospital environment differ from those obtained outside of medical facilities with respect to biofilm formation, antibiotic resistance, and the presence of mobile DNA elements. Since S. epidermidis isolates exhibit high genome flexibility, they are now regarded as reservoirs for the evolution and spread of resistance traits within nosocomial bacterial communities.

Biofilms↗

Efficacies of liposome-encapsulated enrofloxacin against Staphylococcus aureus infection in Anatolian shepherd dog monocytes in vitro.

The aim of this study was to evaluate the intracellular activity of two types of liposome-encapsulated enrofloxacin (LE) compared with free enrofloxacin and non-treated control against Staphylococcus aureus, phagocytosed by monocytes in healthy Anatolian Shepherd dogs. Enrofloxacin was encapsulated with two different types of liposome in multilamellar large vesicles (MLV). Type A MLV were composed of 15 mg phosphatidylcholine and 35 mg cholesterol, Type B MLV were composed of phosphatidylcholine, cholesterol and enrofloxacin in a molar ratio of 1:1:1. Intracellular activity was estimated by comparing the numbers of bacteria surviving intracellularly in monocytes exposed to free enrofloxacin and LE for 4 h at the doses of 0.25, 0.5 and 1 microg/ml, with those surviving intracellularly in untreated control monocytes. All three forms of enrofloxacin (free, Type A and B liposomes) increased the intracellular killing of S. aureus in a concentration dependent manner. Comparison of 1 microg/ml Type B LE revealed that killing activity was significantly higher than those of other concentrations. The results showed that LE was superior in reducing the number of intracellularly located bacteria compared to the free drug and control. The beneficial effect of liposomal encapsulation is presumably due to the fact that both liposomes and bacteria are localized at the same spot in phagocytic cells.

Animals↗

Management of outbreaks of methicillin-resistant Staphylococcus aureus infection in the neonatal intensive care unit: a consensus statement.

OBJECTIVE: In 2002, the Chicago Department of Public Health (CDPH; Chicago, Illinois) convened the Chicago-Area Neonatal MRSA Working Group (CANMWG) to discuss and compare approaches aimed at control of methicillin-resistant Staphylococcus aureus (MRSA) in neonatal intensive care units (NICUs). To better understand these issues on a regional level, the CDPH and the Evanston Department of Health and Human Services (EDHHS; Evanston, Illinois) began an investigation. DESIGN: Survey to collect demographic, clinical, microbiologic, and epidemiologic data on individual cases and clusters of MRSA infection; an additional survey collected data on infection control practices. SETTING: Level III NICUs at Chicago-area hospitals. PARTICIPANTS: Neonates and healthcare workers associated with the level III NICUs. METHODS: From June 2001 through September 2002, the participating hospitals reported all clusters of MRSA infection in their respective level III NICUs to the CDPH and the EDHHS. RESULTS: Thirteen clusters of MRSA infection were detected in level III NICUs, and 149 MRSA-positive infants were reported. Infection control surveys showed that hospitals took different approaches for controlling MRSA colonization and infection in NICUs. CONCLUSION: The CANMWG developed recommendations for the prevention and control of MRSA colonization and infection in the NICU and agreed that recommendations should expand to include future data generated by further studies. Continuing partnerships between hospital infection control personnel and public health professionals will be crucial in honing appropriate guidelines for effective approaches to the management and control of MRSA colonization and infection in NICUs.

Chicago↗

In vitro zones of inhibition of coated vascular catheters predict efficacy in preventing catheter infection with Staphylococcus aureus in vivo.

This report summarizes data from 35 rabbit model experiments investigating the relationship between in vitro anti-infective catheter coating zones of inhibition and in vivo efficacy. The rabbit model studies involving 15 anti-infective coatings demonstrate an inverse correlation between the sizes of zones of inhibition of Staphylococcus aureus and both the quantity of Staphylococcus aureus removed from the catheter and the risk of a purulent infection. The review of seven previously published clinical trials reveals that the use of anti-infective coated catheters, efficacious in the rabbit model, was associated with a higher success rate than the use of uncoated catheters in preventing both Staphylococcus aureus catheter colonization (odds ratio: 1.28; 95% confidence interval: 0.84-1.93) and Staphylococcus aureus catheter-related bloodstream infection (odds ratio: 3.07; 95% confidence interval: 0.98-9.60) in humans. These findings strongly suggest a correlation between zones of inhibition and in vivo efficacy. In vitro zones of inhibition may serve as a useful screening test for evaluating new anti-infective coatings.

Animals↗

Fulminant methicillin-sensitive Staphylococcus aureus infection in a healthy adolescent, highlighting 'Panton-Valentine leucocidin syndrome'.

A 14-year-old immunocompetent adolescent presented systemically unwell with left knee septic arthritis. Within several days, disseminated bone and soft tissue collections became evident, associated with deep venous thrombosis and pulmonary involvement. Methicillin-sensitive Staphylococcus aureus was isolated, harbouring Panton-Valentine leucocidin genes. Aggressive antibiotic and surgical therapies eventually lead to recovery. Intrafamilial spread of the pathogenic isolate was shown by household screening. This presentation is consistent with 'PVL Syndrome' and is typical of severe S. aureus infection emerging in young populations globally.

Adolescent↗

Influences of sequences of environmental factors on the response of chickens to fasting and to Staphylococcus aureus infection.

Weight gain of chickens following fasting was influenced by interactions between habituation to persons (socialization), stress (drinking water withheld) early in the life of the bird, and sex. Fasting affected socialized birds less than unsocialized birds. Body weight changes following Staphylococcus aureus infection were influenced by interactions between sex, stress early in life, socialization, and fasting. These 4 factors may also influence the occurrence of disease outbreaks in poultry farms.

Animals↗

Isotretinoin and Staphylococcus aureus infection. A possible association.

The use of isotretinoin (13-cis-retinoic acid) in the treatment of numerous dermatologic disorders, as well as the side effects encountered with use of the drug, have increased remarkably since its release. We encountered a case of Staphylococcus aureus endocarditis in a patient with chronic stable aortic insufficiency undergoing therapy with isotretinoin for extensive actinic keratoses. Although significant dysfunction of the immune system has not been demonstrated with isotretinoin, nasal colonization with S aureus has been shown to occur. Changes in skin fragility caused by the drug may provide a portal of entry for the organism. Physicians should be alert for this potential complication in patients with an underlying cardiac valvular lesion; antibiotic prophylaxis may be indicated in this group during isotretinoin therapy.

Aortic Valve Insufficiency↗

The decrease in healthcare-associated methicillin-resistant Staphylococcus aureus infections and savings from glycopeptide use.

We evaluated changes in the rate of healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) infections and healthcare-associated S. aureus infections after implementation of infection control precautions and the effect of this on glycopeptide use and expenditures for glycopeptides in a private medical center in Turkey in the years 2000-2005. A striking decrease was obtained in the number of MRSA infections, and the expenditure for glycopeptide use also decreased.

Cross Infection↗

Determinants of chronic infection with Staphylococcus aureus in patients with bronchiectasis.

Staphylococcus aureus is an uncommon pathogen in bronchiectasis not caused by cystic fibrosis (CF). The object of this study was to identify characteristics that cause patients to be prone to infection with S. aureus. The study population consisted of patients with bronchiectasis attending the authors' unit, excluding those with a diagnosis of overt CF. All patients had a high resolution computer tomographic scan (HRCT) of the thorax which demonstrated bronchiectasis. Cases that were currently chronically infected with S. aureus (isolated consecutively on more than two occasions >3 months apart) were identified (n = 12) and compared with 74 control patients who had not been chronically infected with S. aureus. Patients were carefully evaluated to determine the aetiology of their disease. Odds ratios (OR) and 95% confidence intervals (CI) as measures of the association between disease characteristics and chronic infection with S. aureus were calculated. The results for patients chronically infected by S. aureus demonstrated significant associations with allergic bronchopulmonary aspergillosis (ABPA; OR = 8.8, 95% CI 1.8-41.9), atypical variants of CF (OR = 12.0, 95% CI 1.8-81.7) or equivocal sweat sodium values (OR = 4.0, 95% CI 1.0-15.3). The associations persisted when the analysis was based on cases (n = 28) in whom S. aureus had ever been isolated from sputum. In the latter analysis there was also a significant association with predominant upper zone disease on HRCT. These results suggest that patients with bronchiectasis in whom S. aureus is isolated from sputum should be carefully evaluated to exclude allergic bronchopulmonary aspergillosis or atypical cystic fibrosis.

Adult↗