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At least 613 records · Page 34Linked to original sources
PubMed2000

Are B lymphocytes of importance in severe Staphylococcus aureus infections?

To investigate the role of B cells in experimental, superantigen-mediated Staphylococcus aureus arthritis and sepsis, we used gene-targeted B-cell-deficient mice. The mice were inoculated intravenously with a toxic shock syndrome toxin 1 (TSST-1)-producing S. aureus strain. The B-cell-deficient and thus agamma-globulinemic mice showed striking similarities to the wild-type control animals with respect to the development of arthritis, the mortality rate, and the rate of bacterial clearance. Surprisingly, we found that the levels of gamma interferon in serum were significantly lower (P < 0. 0001) in B-cell-deficient mice than in the controls, possibly due to impaired superantigen presentation and a diminished expression of costimulatory molecules. In contrast, the levels of interleukin-4 (IL-4), IL-6, and IL-10 in serum were equal in both groups. Our findings demonstrate that neither mature B cells nor their products significantly contribute to the course of S. aureus-induced septic arthritis.

Animals↗
PubMed1999

Experimental acute hematogenous osteomyelitis in mice. II. Influence of Staphylococcus aureus infection on T-cell immunity.

A murine model of acute hematogenous osteomyelitis was used to study the immune response following Staphylococcus aureus infection and to examine the hypothesis that the bacteria may modify T-cell responses due to the production of bacterial enterotoxins with mitogenic or superantigenic activity. Lymph-node T cell-receptor expression was assessed with use of flow cytometry and reverse transcription-polymerase chain reaction techniques, and increased apoptosis (programmed cell death) in T-cell subsets was monitored. The expression and levels of circulating cytokines and T-cell cytokines within tissues surrounding the damaged area of the proximal tibia were also investigated. Analysis of T-cell receptors in experimental osteomyelitis revealed two distinct patterns of T-cell evolution during the disease. Certain T-cell subsets (Vbeta2, Vbeta3, Vbeta9, and Vbeta10) were activated and expanded during the first 24 hours after infection; they reached maximum levels 6 days after infection, followed by a return to pre-infection levels. In contrast, other T-cell subsets (Vbeta11, Vbeta12, Vbeta13, Vbeta14, and Vbeta16) contracted during the first 24 hours after infection, followed by expansion to a maximum level 9 days after infection. Activation and proliferation of T-cell subsets (notably Vbeta14 T cells) was followed by apoptosis, suggesting that staphylococcal bone infection caused superantigenic-like effects on the mouse immune system. Analysis of cytokine responses in local tissue revealed that the T-cell cytokines interleukin-2 and interferon-gamma showed a late and relatively short activation pattern compared with the inflammatory cytokines interleukin-1, interleukin-6, and tumor necrosis factor-alpha. The results suggest that Staphylococcus aureus bone infection may undermine the antibacterial immune response through downregulation of T-cell immunity and immune-cytokine production, which could increase the severity of the systemic infection and local osseous destruction that occur with acute hematogenous osteomyelitis.

Acute Disease↗
PubMed2004

Epidemiology and prevention of skin and soft tissue infections.

Staphylococcus aureus and Streptococcus pyogenes remain the 2 major organisms responsible for most common skin and soft tissue infections. While methicillin-resistant S aureus (MRSA) typically is considered a hospital-acquired organism, outbreaks of community-acquired MRSA are being reported. Simple interventions can reduce the spread of this infection. Erysipelas is a streptococcal syndrome with high morbidity. The epidemiology has changed, with an increasing number of cases involving the lower extremities. Risk factors for erysipelas can be identified, which allow clinicians to target patients at high risk for recurrent disease. Although staphylococci and streptococci are the predominant cutaneous pathogens, enterococci and gram-negative organisms account for a significant proportion of skin infections.

Humans↗
PubMed1992

A comparison of clinical virulence of nosocomially acquired methicillin-resistant and methicillin-sensitive Staphylococcus aureus infections in a university hospital.

OBJECTIVES: To compare the clinical virulence of nosocomially acquired methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) infections in 1989. DESIGN: A retrospective comparison of host factors, in-hospital exposures, sites of infections, and outcomes of patients with nosocomial MRSA and MSSA infections. SETTING: University of Illinois Hospital, Chicago, Illinois. PARTICIPANTS: Forty-four adult patients with nosocomial S aureus infections. RESULTS: The 22 MRSA-infected and 22 MSSA-infected persons were similar regarding mean age, gender, underlying diseases, and exposure to surgery. Before developing infection, MRSA-infected persons were more likely to have received antibiotics (73% compared with 27%, odds ratio = 7.1, 95% confidence interval [CI95] = 2.0-25.8 p = .003) and to have stayed in the hospital > 2 weeks (64% compared with 18%, odds ratio = 7.9, CI95 = 2.0-31.6, p = .002). Bacteremia was the most common presentation in the MRSA and MSSA groups (55% and 59%, respectively). Infectious complications and death were infrequent in both groups. CONCLUSIONS: MRSA and MSSA strains infect patients with similar demographic features and underlying diseases, but MRSA infections are significantly more common among patients with previous antibiotic therapy and a prolonged preinfection hospital stay. Clinical presentations and outcomes did not differ significantly between the 2 groups. Thus, similar to studies in the early 1980s, our findings do not suggest greater intrinsic virulence of MRSA.

Chicago↗
PubMed2006

Common house spiders are not likely vectors of community-acquired methicillin-resistant Staphylococcus aureus infections.

There is an increasing incidence in the number of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections in the United States. Skin and soft tissue infections caused by MRSA are often perceived as being preceded by a spider bite. Several possibilities exist to explain this phenomenon, including 1) spiders introduce MRSA into the bite wound and thereby serve as a potential vehicle or vector for MRSA; 2) MRSA colonization is an event secondary to the spider bite; and 3) the spider bite is a misguided way for patients or their physicians to explain the initial lesion of their skin or soft tissue infection. We hypothesized that if spiders were able to serve as vehicles or vectors for MRSA infections, they would be colonized with this pathogen. To test this hypothesis, we captured common household spiders and determined the patterns of normal microbial flora isolated from them. Spiders were collected from several homes by their occupants, photographed for identification, and cultured for external and internal microbial flora. Of > 100 spiders collected, none was found to carry Staphylococcus aureus or MRSA. Relatively low numbers of microbial flora were isolated, and only a single isolate with pathogenic potential in humans (Aeromonas spp.) was isolated. Common house spiders are unlikely to be a source of MRSA.

Animals↗
PubMed2005

A mutant of staphylococcal enterotoxin C devoid of bacterial superantigenic activity elicits a Th2 immune response for protection against Staphylococcus aureus infection.

Staphylococcal enterotoxin C (SEC), a bacterial superantigenic exotoxin, is commonly produced by invasive Staphylococcus aureus isolates, especially methicillin-resistant strains and isolates from animal diseases. We constructed and expressed a nontoxic mutant SEC (mSEC) and investigated whether immunization with mSEC, which is devoid of superantigenic activity, can protect against S. aureus infection. Mice were immunized with mSEC and challenged with viable S. aureus. The bacterial counts in the organs of mSEC-immunized mice were significantly lower and the survival rate was higher than the corresponding values for the control group. Immunization with mSEC strongly induced the production of T-helper 2 type antibodies, immunoglobulin G1, and immunoglobulin G2b. The production of interleukin-10 (IL-10) and IL-4 was significantly greater in immunized mice challenged with S. aureus than in the control mice, whereas the production of gamma interferon (IFN-gamma) was significantly decreased in the immunized mice. The cytokine response in a spleen cell culture that was stimulated with heat-killed S. aureus or SEC showed that immunization with mSEC inhibited IFN-gamma production and up-regulated IL-10 production in vitro. Furthermore, IFN-gamma and tumor necrosis factor alpha production in vitro was significantly inhibited by sera from mSEC-immunized mice but not by sera from control mice. These results suggest that immunization with mSEC devoid of superantigenic properties provides protection against S. aureus infection and that the protection might be mediated by SEC-specific neutralizing antibodies.

Animals↗
PubMed2001

Primary cultures of human chondrocytes are susceptible to low inocula of Staphylococcus aureus infection and undergo apoptosis.

Hypocellularity after joint infection has been attributed to the cytotoxic effects of pus, which can cause necrosis of chondrocytes. In this study, primary cultures of human chondrocytes lost their viability and underwent necrosis rapidly with high inocula of Staphylococcus aureus infection. Chondrocytes were shown to undergo apoptosis with low inocula of Staphylococcus aureus or their culture ultrafiltrate. These findings further support the hypothesis that residual bacterial toxins or triggered apoptotic processes in chondrocytes participate in the pathogenesis of post-infectious arthropathy.

Apoptosis↗
PubMed2005

Cutaneous community-acquired methicillin-resistant Staphylococcus aureus infection in participants of athletic activities.

OBJECTIVES: Cutaneous community-acquired methicillin-resistant Staphylococcus aureus (CAMRSA) has been identified in otherwise healthy individuals either with or without methicillin-resistant S. aureus (MRSA)-associated risk factors who participate in athletic activities. The purpose of this study was to describe the clinical features of CAMRSA skin infection that occurred in university student athletes, evaluate the potential mechanisms for the transmission of MRSA infection of the skin in participants of athletic activities, and review the measures for preventing the spread of cutaneous CAMRSA infection in athletes. METHODS: A retrospective chart review of the student athletes from the University of Houston whose skin lesions were evaluated at the Health Center and grew MRSA was performed. The clinical characteristics and the postulated mechanisms of cutaneous MRSA infection in the athletes were compared with those previously published in reports of CAMRSA skin infection outbreaks in other sports participants. RESULTS: Cutaneous CAMRSA infection occurred in seven student athletes (four women and three men) who were either weight lifters (three students) or members of a varsity sports team: volleyball (two women), basketball (one woman), and football (one man). The MRSA skin infection presented as solitary or multiple, tender, erythematous, fluctuant abscesses with surrounding cellulitis. The lesions were most frequently located in the axillary region (three weight lifters), on the buttocks (two women), or on the thighs (two women). The drainage from all of the skin lesions grew MRSA, which was susceptible to clindamycin, gentamicin, rifampin, trimethoprim/sulfamethoxazole, and vancomycin; five of the isolates were also susceptible to ciprofloxacin and levofloxacin. All of the bacterial strains were resistant to erythromycin, oxacillin, and penicillin. The cutaneous MRSA infections persisted or worsened in the six athletes who were empirically treated for methicillin-sensitive S. aureus at their initial visit. Complete resolution of the skin infection occurred after the abscesses had been drained and the athlete had been treated with systemic antimicrobial therapy for which the bacterial strain was susceptible. CONCLUSIONS: Cutaneous CAMRSA infection typically presents as an abscess, with or without surrounding cellulitis, in otherwise healthy participants of athletic activities who have or do not have MRSA-associated risk factors. Athletes who have MRSA skin infections include weight lifters and team members from competitive sports such as basketball, fencing, football, rugby, volleyball, and wrestling. Bacterial culture of suspected infectious skin lesions should be performed to establish the diagnosis of cutaneous MRSA infection and to determine the antibiotic susceptibility of the bacterial isolate. Treatment of cutaneous MRSA infection involves drainage of the abscess (either spontaneously or after incision) and appropriate systemic antimicrobial therapy. Direct skin-to-skin physical contact with infectious lesions or drainage, skin damage that facilitates the entry of bacteria, and sharing of infected equipment, clothing, or personal items may result in the acquisition and transmission of MRSA infection in participants of athletic activities. Earlier detection and topical treatment of the athlete's skin wounds by their coaches, avoidance of contact with other participants' cutaneous lesions and their drainage, and good personal hygiene are measures that can potentially prevent the spread of cutaneous MRSA infection in participants of athletic activities.

Abscess↗
PubMed2001

Pharmacodynamics of daptomycin in a murine thigh model of Staphylococcus aureus infection.

Daptomycin is a lipopeptide antibiotic with activity against gram-positive bacteria, including Staphylococcus aureus. We defined the pharmacodynamic parameters that determine the activity of daptomycin for S. aureus using in vitro methods and the Craig (W. A. Craig, J. Redington, and S. C. Ebert, J. Antimicrob. Chemother. 27[Suppl. C]:29--40, 1991) neutropenic mouse thigh infection model. In Mueller-Hinton broth, the MICs for three S. aureus isolates were 0.1 to 0.2 microg/ml. In mouse serum, the MICs were 1.0 microg/ml. The protein binding of daptomycin was 90 to 92.5% in mouse serum. Single-dose intraperitoneal (i.p.) pharmacokinetic studies with infected mice showed a linear relationship between dose versus the maximum concentration of drug in serum and dose versus the area under the concentration-time curve (AUC). The serum half-life of daptomycin in infected mice was approximately 1.8 h. In single-dose, dose-ranging studies using mice, daptomycin showed a dose-response effect described by an inhibitory sigmoid E(max) (maximum effect) curve (r = 0.974; P << 0.001). The density of S. aureus in untreated controls was 8.26 log(10) CFU/g, and the E(max) was 3.97 log(10) CFU/g. The 50% effective dose (ED(50)) was 3.7 mg/kg of body weight i.p. and the stasis dose was 7.1 mg/kg. Dose fractionation studies at schedules of Q6h, Q12h, and Q24h, for total 24-h ED(30), ED(60), and ED(80) doses of 2.5, 5.6, and 15 mg/kg i.p., showed no difference in effect at each total 24-h dose level by schedule, indicating that the AUC/MIC ratio is the dynamically linked variable.

Animals↗
PubMed2006

Clinical, microbiological, and molecular characterization of methicillin-resistant Staphylococcus aureus infections of cats.

OBJECTIVE: To compare clinical information obtained from medical records of cats with methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S aureus (MSSA) infections, evaluate antibiograms of MRSA and MSSA for multiple-drug resistance (MDR), and characterize the strain type and staphylococcal chromosome cassette (SCC)mec type of each MRSA. SAMPLE POPULATION: 70 S aureus isolates obtained from 46 cats. PROCEDURES: Clinical information obtained from medical records, including signalment, clinical signs, histologic examination of affected tissues, and outcomes, was compared between the 2 groups. Composite antibiograms of MRSA and MSSA were compared statistically. The MRSA strains were characterized by use of pulsed-field gel electrophoresis and SCCmec typing. RESULTS: No statistical differences in signalment or subjective differences in clinical signs or outcomes were detected between groups with MRSA or MSSA infection. Significant differences in antimicrobial resistance were detected, with MRSA having complete resistance to fluoroquinolone and macrolide antimicrobials, whereas MSSA maintained a high frequency of susceptibility. Seven pulsed-field patterns were observed in 15 MRSA strains; all but 1 were highly related. All MRSA isolates contained a type II SCCmec element. CONCLUSIONS AND CLINICAL RELEVANCE: Because MDR cannot be predicted in staphylococcal infections in cats on the basis of clinical signalment, culture and susceptibility testing are recommended whenever initial empirical treatment is unsuccessful. Molecular characterization of MRSA strains suggests that there has been reverse-zoonotic transmission from humans. IMPACT FOR HUMAN MEDICINE: The SCCmec type II element is typically associated with nosocomial MRSA infections of people. Cats may serve as reservoirs for MRSA infections in humans.

Animals↗
PubMed1990

[Outbreak of Staphylococcus aureus infections in an intensive care unit].

An outbreak of nosocomial staphylococcal infections occurred over a six months period in an intensive care unit. This outbreak was caused by a single phage type of oxacillin resistant Staphylococcus aureus (SA) which infected ten patients. Six patients had bacteremia with infected catheter, two with urinary tract infection and two patients had a pneumonia. The median SAPS was 13. Four patients died. An epidemiologic study was performed to know SA nasal carriage prevalence of patients and hospital staff. There were seven isolates of SA from 83 hospital staff and three from 20 patients, all with the same phage type 77. Hospital staff and patients colonisation with a same SA strain is a potential reservoir for epidemic nosocomial infections. Prophylactic measures are hygienic measures like handwashing, but perhaps also patients and staff selective decontamination with topical antimicrobial substances.

Cross Infection↗
PubMed1983

Bacteria isolated from deep joint sepsis after operation for total hip or knee replacement and the sources of the infections with Staphylococcus aureus.

A wide variety of bacterial species, many usually regarded as of low pathogenicity, were isolated from septic joints after operation for total hip or knee joint replacement in a multi-centre trial of ultraclean air in operating rooms. The prophylactic antibiotics generally used appeared to reduce considerably the rates of infection with most species but to be ineffective against 'gut' organisms. For about half the septic infections involving Staphylococcus aureus nasal swabs had been obtained from the patient and operating staff at the time of operation for insertion of the prosthesis. Strains of Staph, aureus isolated from these and from the infected joints were phage typed and tested for antibiotic sensitivity. A probable source among the carriers was found for seven out of the 14 infections and a possible source for another five. Very small numbers of Staph. aureus were needed to initiate infection.

Air Microbiology↗
PubMed1987

Outbreak of methicillin-resistant Staphylococcus aureus infection in a New Zealand hospital.

During a 17 month period from March 1985 to July 1986, 30 patients and four members of staff became infected or colonised with a single strain of methicillin-resistant Staphylococcus aureus (MRSA) during an outbreak which originated at Wellington Hospital. Initially, crossinfection occurred within the intensive care unit but infected or colonised patients became distributed to 14 hospital wards and to five other hospitals within New Zealand. MRSA septicaemia contributed to the death of two patients. The source of the epidemic strain of MRSA has not been established with certainty, but may have been introduced by a staff nurse known to be a carrier when employed at an Australian hospital. The investigation, management and eventual control of this first outbreak in New Zealand are described.

Adolescent↗
PubMed1994

[The improvement on the nursing procedure for pregnant women and newborns and the decrease of Staphylococcus aureus infections in newborns and infants in our hospital].

Knowing the importance of prevention of Staphylococcus aureus infections, especially that of Methicillin-resistant S. aureus (herein after abbreviated as MRSA) in the newborn room, we improved the nursing procedure in the room and examined subsequent changes in the onset condition of the above infection in newborns and infants less than 1-year-old. The infection was detected in 13 cases of stage 1 (stage according to the nursing procedure since the opening of our hospital): 6 cases (all MRSA) had their onset in the room. MRSA was detected in 11 cases, suspecting a hospital cross infection in relation to the period of birth and coagulase type. The infection was detected in 9 cases of stage 2 (stage of prevention of inter-newborn hospital cross infection through environmental purification within the newborn room, through hand and finger disinfection of medical workers, through improved bathing, etc.); 2 cases (1 of MRSA, 1 of Methicillin-sensitive S. aureus [hereinafter abbreviated as MSSA]) had an onset in the room. MRSA was detected in 5 cases, but hospital cross infection was thought difficult to be responsible. The MRSA infection was detected in 4 pregnant cases (0.8%) of stage 3 (stage of effortful prevention of MRSA from carrying into the ward following examination of possible intra-nasal MRSA establishment in pregnant women in addition to similar newborn nursing to stage 2), indicating pregnant women's possible carrying MRSA into the newborn room. S. aureus infection was detected in 9 cases; 2 cases (MSSA) had an onset in the above room.(ABSTRACT TRUNCATED AT 250 WORDS)

Cross Infection↗