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PubMed1985

Susceptibility of laboratory rats, hamsters, and mice to wound infection with Staphylococcus aureus.

Response of rodents to experimentally induced subcutaneous infection was examined to determine whether laboratory rats used in invasive procedures have a superior ability to withstand wound infection than do hamsters and mice. Rats, hamsters, and mice were injected subcutaneously with 10(9), 10(7), and 10(5) colony-forming units of Staphylococcus aureus. Quantitative counts of viable S aureus from the injection site, bacteriologic cultures of heart blood, and histologic examinations of the subcutaneous tissues were performed. Multiple linear regression of the quantitative data and equality of regression lines among groups were determined. Results indicated that the ability to eliminate bacteria varied between species and depended on the dose injected within each species. Compared with hamsters and mice at all doses, rats eliminated bacteria faster and had the mildest and most rapidly organized inflammatory response after inoculation. Experimental bacteremia developed in 3.7% of all animals evaluated, with no species-specific pattern. The rat was more resistant to localized wound infection with S aureus than were hamsters and mice.

Abscess↗
PubMed1987

Expression of capsular polysaccharide during experimental focal infection with Staphylococcus aureus.

In vivo expression of the type 8 capsular polysaccharide (CP) of Staphylococcus aureus was studied by using the Becker strain, the prototype type 8 strain, in a guinea pig model of persistent subcutaneous infection. At 24 hr after infection, supernatants of aspirates from the site of infection contained low levels of CP (median, 0.53 ng/ml; range, less than 0.16-6.30 ng/ml). CP levels increased at day 3 to a geometric mean level of 47 ng/ml, at day 6 to 389 ng/ml, at day 8 to 537 ng/ml, and thereafter persisted in that range. On days 1, 3, and 6, CP was not detectable (less than 0.16 ng/ml) in the serum, but on days 8, 10, or 13, CP was present in 15 (58%) of 26 animals; the median peak level of serum CP among these animals was 2.00 ng/ml (range, 0.31-5.90 ng/ml). These studies document that the type 8 CP of S. aureus is produced and released during a focal, suppurative infection and can be detected in the serum of infected animals.

Animals↗
PubMed2004

Persistent bacteremia due to methicillin-resistant Staphylococcus aureus infection is associated with agr dysfunction and low-level in vitro resistance to thrombin-induced platelet microbicidal protein.

BACKGROUND: The causes of persistent bacteremia (PB) due to methicillin-resistant Staphylococcus aureus (MRSA) are poorly understood. This investigation examined potential associations between PB with key clinical features and several in vitro bacterial genotypic and phenotypic characteristics, in isolates from 1 institution. METHODS: Pulsed-field gel electrophoresis (PFGE) relatedness, thrombin-induced platelet microbicidal protein (tPMP)-susceptibility phenotype, accessory gene regulator (agr) genotype and functionality (via delta-lysin production), and autolysis phenotypes were assessed in MRSA isolates from the bloodstream of 21 prospectively identified patients with PB (blood cultures positive after > or =7 days of therapy) and of 18 patients with resolving bacteremia (RB) (sterile blood cultures within the first 2-4 days of therapy) due to MRSA. RESULTS: The 2 groups had comparable baseline characteristics but differed in their clinical courses (e.g., endocarditis was more frequent in patients with PB than in those with RB [43% vs. 0%, respectively; P=.0016]); isolates from patients with PB exhibited higher rates of (1) survival in vitro after exposure to tPMP (22.4+/-14.8% vs. 11.6+/-6.5%, respectively; P=.005); (2) defective delta-lysin production (71.4% vs. 38.9%, respectively; P=.057); (3) non-agr genotype II profile (100% vs. 77.8%, respectively; P=.037); and (4) overrepresentation of a specific PFGE genotype (85.7% vs. 44.4%, respectively; P=.015). CONCLUSIONS: Isolates from patients with PB differed from those in patients with RB, in several in vitro characteristics. Further studies will be necessary to define how these factors might affect clinical outcome.

Anti-Bacterial Agents↗
PubMed1989

Rapid screening for Staphylococcus aureus infection by measuring enterotoxin B.

We developed a simple, sensitive laser nephelometric assay (LNA) to detect circulating staphylococcal enterotoxin B (SEB). This assay yields the result within 2 h and needs no special treatment. Influence of protein A, a product generated by Staphylococcus aureus, was negligible in this assay. The levels of SEB in plasma were measured in 28 patients with and without S. aureus infection with the LNA. The levels of SEB in plasma increased significantly in patients with S. aureus infection. We also demonstrated that the levels of SEB in plasma were higher in patients with methicillin-resistant S. aureus infection than in patients with nonresistant staphylococcal infection. Our data indicate that LNA is a useful assay in the early diagnosis of methicillin-resistant S. aureus infection.

Cross Reactions↗
PubMed2003

Graft-preserving treatment for vascular graft infected with Staphylococcus aureus with antibiotic-releasing porous apatite ceramic in the rabbit.

OBJECTIVE: This study was undertaken to investigate whether infection of a vascular graft with Staphylococcus aureus can be treated in situ by applying antibiotic-loaded porous apatite ceramic, in a rabbit model. METHODS: Teicoplanin (TEIC) was loaded onto a beta-tricalcium phosphate (TCP) block, a type of porous apatite ceramic. The activity of TEIC released from the antibiotic-loaded TCP block was examined in vivo. A vascular graft was patched onto the abdominal aorta in 24 rabbits, and S aureus was applied directly on it. Seven days postoperatively, each rabbit underwent repeat laparotomy, and retroperitoneal abscess around the prosthetic vascular patch was debrided. Animals were divided into four groups of 6 rabbits each. In group 1 only debridement was carried out. In groups 2 and 3, solution containing 40 or 60 mg of TEIC, respectively, was applied to the prosthetic vascular patch. In group 4, an antibiotic-loaded TCP block (63 +/- 6.6 mg of TEIC) was placed around the graft. Three weeks after the second operation, the graft, the tissue around it, and arterial blood were collected and cultured. RESULTS: TEIC activity was maintained for 28 days in vivo. In group 1, bacterial cultures of the prosthetic vascular graft and the tissue around it were positive in 5 animals and negative in 1 animal (infection rate, 83%). In both groups 2 and 3, cultures were positive in 3 animals and negative in 3 animals (infection rate, 50%). In group 4, cultures were negative in all animals (infection rate, 0%). Blood cultures were negative in all animals. Infection rate in group 4 was significantly lower than that in group 1 (P =.03), and was also lower than that in groups 2 and 3, but the difference was not significant. CONCLUSIONS: Use of slow-release antibiotic loaded onto a TCP block, along with debridement, may control infection in vascular grafts in situ, averting the necessity to remove the graft.

Administration, Topical↗
PubMed2006

Evaluation of an intervention designed to decrease the rate of nosocomial methicillin-resistant Staphylococcus aureus infection by encouraging decreased fluoroquinolone use.

OBJECTIVE: Society for Health Care Epidemiology guidelines recommend decreasing the use of fluoroquinolone antibiotics in institutions where methicillin-resistant Staphylococcus aureus (MRSA) is endemic. We evaluated whether an intervention to limit fluoroquinolone use was associated with a lower rate of nosocomial MRSA infection and summarized changes in antibiotic use, changes in other variables potentially correlated with a lower rate of MRSA infection, and rates of nosocomial infections due to other pathogens. DESIGN: Single-center quasi-experimental design. A time series of nosocomial MRSA infections was measured at monthly intervals from July 2001 through June of 2004; there were 80 MRSA infections recorded. Segmented regression analysis (ie, quasi-Poisson generalized linear models) was used to evaluate variables possibly associated with the nosocomial MRSA infection rate. SETTING: An 87-bed Veterans Affairs teaching hospital with an extended-care facility. INTERVENTION: A physician-directed computer-generated intervention designed to limit the use of fluoroquinolone antibiotics was initiated, and institutional changes in antibiotic use and nosocomial MRSA infection rates were tracked. RESULTS: After the intervention, fluoroquinolone use decreased by approximately 34%, and levofloxacin use decreased by approximately 50%. Decreased fluoroquinolone use was offset by increased cephalosporin, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole use. The nosocomial MRSA infection rate decreased from 1.37 to 0.63 episodes per 1,000 patient-days after the study intervention (P=.02). Coagulase-negative Staphylococcus and Enterococcus infection rates also decreased. However, the rate of infection with gram-negative organisms increased. The rate of MRSA infection was positively correlated with levofloxacin use (P=.01) and azithromycin use (P=.08), whereas it was negatively correlated with summer season (P=.05). In a subsequent model, the rate of MRSA infection was negatively correlated with the study intervention (P=.04). CONCLUSION: Reduction in the institutional use of fluoroquinolones may be associated with a lower nosocomial MRSA infection rate.

Cross Infection↗
PubMed2001

[Vascular graft infection by Staphylococcus epidermidis: efficacy of various perioperative prophylaxis protocols in an animal model].

A rat model was used to investigate the efficacy of levofloxacin, cefazolin and teicoplanin in the prevention of vascular prosthetic graft infection. Graft infections were established in the subcutaneous tissue of 300 male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with methicillin-susceptible and methicillin-resistant S. epidermidis. The study included a group without contamination, two contaminated groups without prophylaxis, two contaminated groups with intraperitoneal levofloxacin prophylaxis (10 mg/kg), two contaminated groups with intraperitoneal cefazolin prophylaxis (30 mg/kg), two contaminated groups with intraperitoneal teicoplanin prophylaxis (10 mg/kg) and six contaminated groups with rifampin-soaked graft and intraperitoneal levofloxacin, cefazolin or te- icoplanin prophylaxis. The grafts were removed after 7 days and evaluated by quantitative culture. The efficacy of levofloxacin against the methicillin- susceptible strain did not differ from that of cefazolin or teicoplanin. Levofloxacin showed slight less efficacy than teicoplanin against the methicillin-resistant strain. The levofloxacin-rifampin combination proved to be similarly effective to the rifampin-teicoplanin combination and more effective than the rifampin-cefazolin combination against both strains. The rifampin-levofloxacin combination may be useful for the prevention of late-appearing vascular graft infections caused by S. epidermidis because it takes advantage of the good anti-staphylococcal activity of both drugs.

Animals↗
PubMed1989

Ciprofloxacin therapy for methicillin-resistant Staphylococcus aureus infections or colonizations.

Thirty patients were treated for colonization or for skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus. Three treatment regimens were evaluated, each progressively more aggressive. Our regimen was 750 mg of ciprofloxacin twice daily for 5 days, the second regimen was 750 mg of ciprofloxacin twice daily for 10 to 14 days, and the final regimen was 750 mg of ciprofloxacin twice daily plus 300 mg of rifampin twice daily for 21 days. It appears that ciprofloxacin alone produced an initial eradication rate in at least one site in 50% of the patients, regardless of whether the treatment was for 5 or up to 14 days. All of the patients with eradication became recolonized within 1 week posttherapy. When rifampin was combined with ciprofloxacin, the eradication rate was 100% when the isolates were susceptible to both agents, and these patients remained free of methicillin-resistant S. aureus at 1-week and 1-month follow-ups.

Ciprofloxacin↗
PubMed1993

Efficacy of antibiotic-coated catheters in preventing subcutaneous Staphylococcus aureus infection in rabbits.

Vascular catheters coated with antiinfective compounds were evaluated as to their ability to prevent Staphylococcus aureus catheter infection in a rabbit model. Zones of inhibition of agar surface-plated S. aureus demonstrated the following hierarchy: dicloxacillin and clindamycin were each better than fusidic acid or chlorhexidine, which were better than ciprofloxacin, cefotaxime, or cefuroxime. In vivo half-lives of inhibitory activity for clindamycin and dicloxacillin were 5.6 and 17.7 h, respectively, with apparent first-order kinetics. Chlorhexidine disappeared in vivo with apparent two-compartment kinetics: first-compartment t1/2, 16.8 h; second-compartment t1/2, 115.6 h. In a rabbit model, dicloxacillin, clindamycin, fusidic acid, and chlorhexidine decreased the risk of infection compared with uncoated control catheters (P < .05). For dicloxacillin, clindamycin, and chlorhexidine, this was true even if the S. aureus inoculation was delayed 48 or 96 h after catheter implantation. These data suggest that vascular catheters with antiinfective coatings should be investigated further in hospitalized patients.

Animals↗
PubMed1999

Failure of antibiotic therapy in Staphylococcus epidermidis infection of implantable venous access devices in patients with AIDS, as documented by molecular typing.

OBJECTIVE: To study the efficacy and safety of high-concentration antibiotic locks in association with systemic antibiotherapy in Staphylococcus epidermidis infections of totally implantable venous access devices (TIVADs) in patients with AIDS. METHODS: Thirty-one episodes of S. epidermidis TIVAD infection were observed in nine patients. Locks consisted of high concentrations of aminoglycosides or vancomycin according to antibiogram results (susceptibility results obtained with the disk diffusion technique). Genotyping of bacterial strains was performed by pulsed-field gel electrophoresis (PFGE) in 26 of the 31 infectious episodes. RESULTS: The infections occurred within a median period of 62 catheter-days. The median duration of systemic antibiotic therapy was 17.5 days in association with a median of three antibiotic locks. Failure as defined by the occurrence of a novel episode within 2 months was observed in 17 of the 31 infections (58%). According to the PFGE results, relapse with the same strain of S. epidermidis or reinfection with a different strain of S. epidermidis could be assigned to 10 episodes which failed to respond to therapy. Relapse was observed in six of 10 episodes. Four episodes were followed by the occurrence of a novel infection with a different S. epidermidis strain. In one patient, a relapse occurred despite TIVAD removal. CONCLUSION: Our observations further document the poor efficacy of associating antibiotic locks with systemic antibiotic therapy for the treatment of TIVAD infections in patients with AIDS.

Journal Article↗
PubMed1968

Association of C-reactive protein and circulating leukocytes with resistance to Staphylococcus aureus infection in endotoxin-treated mice and rabbits.

The response of rabbits and mice to treatment with Escherichia coli endotoxin, as measured by C-reactive protein (CRP) and leukocyte levels, and resistance to Staphylococcus aureus infection was studied to evaluate the significance of these responses and their associations. In both species, there was an initial leukopenia without early recovery of normal lymphocyte levels. This was followed by an increase in polymorphonuclear leukocytes and a return to near the normal range. The CRP level was slightly altered during the stage of decreased resistance and increased throughout the remainder of the period of observation. The resistance level was decreased initially, recovered to normal levels, and continued to increase. The changes in CRP and resistance levels were closely associated. It would appear that this association between CRP and resistance, the antibacterial activity of CRP, and its action on the polysaccharides obtained from bacterial cell walls are evidence for the participation of CRP in nonspecific resistance to infection.

Animals↗
PubMed1999

Extracellular-matrix-binding proteins as targets for the prevention of Staphylococcus aureus infections.

Staphylococcal infections cause a number of serious diseases, ranging from acute septicaemia to chronic problems such as osteomyelitis and septic arthritis. Resistance to antibiotics is a growing problem and has re-ignited interest in vaccines and in passive immunization with antibodies. Natural infections and vaccines based on whole bacteria lead to poor antibody responses, but recent research using animal models of several staphylococcal diseases reveals that vaccines based on recombinant staphylococcal extracellular-matrix-binding proteins are much more protective. Passive immunization with antibodies against one of these proteins (collagen-binding protein) also shows promise in a mouse model of sepsis.

Adhesins, Bacterial↗
PubMed1994

Genetic impact on the risk of intramammary infection following Staphylococcus aureus challenge.

This study evaluated relationships among intramammary challenge with Staphylococcus aureus, SCC, and susceptibility to infection and determined the genetic contribution to susceptibility of infection with special emphasis on bovine lymphocyte antigens. Intramammary challenge with S. aureus Newbould 305 was used as a model for natural infection. A total of 124 cows were challenged in all quarters with 600 cfu of S. aureus Newbould 305 in 2 ml of PBS solution. Quarter milk samples for bacteriology and SCC were taken at three times both before and after challenge. Lymphocytes were separated from whole blood and tested with a standard microlymphocytotoxicity test to determine the presence of bovine lymphocyte antigens class I alleles. One hundred and thirteen cows were negative for S. aureus at challenge, and 11 cows exhibited positive S. aureus counts in one or more quarters at challenge. Fifty-three percent of quarters from the 124 cows challenged became infected after challenge. Nineteen cows had no quarters infected; 19 cows, one; 26 cows, two; 25 cows, three; and 24 cows had four quarters infected after challenge. Average SCC before challenge was 181,000 and after challenge was 758,600. The SCC prior to challenge of cows that resisted infection were higher than prior SCC of cows that became infected (282,000 and 91,000, respectively). The reverse was true after challenge. Presence of the bovine lymphocyte antigens class I allele CA42, instead of EU28 (based on gene substitution), increased susceptibility to S. aureus infection. Heritability estimates of S. aureus susceptibility after experimental challenge were low and unstable.

Alleles↗
PubMed1999

Regulated antisense RNA eliminates alpha-toxin virulence in Staphylococcus aureus infection.

The ability to selectively disrupt gene function remains a critical element in elucidating information regarding gene essentiality for bacterial growth and/or pathogenesis. In this study, we adapted a tet regulatory expression system for use in Staphylococcus aureus, with the goal of downregulating gene expression via induction of antisense RNA. We demonstrate that this system exhibits a 50- to 100-fold dose-dependent level of induction in bacterial cells grown in culture (i.e., in vitro) and also functions in mice (i.e., in vivo) following oral administration of inducer. To determine whether induced antisense RNA could interfere with chromosomally derived gene expression, we cloned a fragment of the S. aureus alpha-toxin gene (hla) in antisense orientation downstream of the tet promoter system and introduced the construct into S. aureus. Induced antisense hla RNA downregulated chromosomally derived hla gene expression in vitro approximately 14-fold. Similarly, induction of hla antisense RNA in vivo dramatically reduced alpha-toxin expression in two different murine models of S. aureus infection. Most importantly, this reduction completely eliminated the lethality of the infection. These results indicate that the tet regulatory system functions efficiently in S. aureus and induced antisense RNA can effectively downregulate chromosomal gene expression both in vitro and in vivo.

Animals↗