Efficacy of lysostaphin-coated titanium plates on implant-associated MRSA osteitis in minipigs.

PURPOSE: The growing incidence of implant-associated infections (IAIs) caused by biofilm-forming Staphylococcus aureus in combination with an increasing resistance to antibiotics requires new therapeutic strategies. Lysostaphin has been shown to eliminate this biofilm. Own studies confirm the effectiveness in a murine model. The current study characterizes the effects of lysostaphin-coated plates in an IAI minipig model. METHODS: The femur of 30 minipigs was stabilized with a five-hole plate, a bone defect was created, and in 20 cases methicillin-resistant Staphylococcus aureus was applied. Ten animals served as control group. After 14 days, local debridement, lavage, and plate exchange (seven-hole plate) were performed. Ten of the infected minipigs received an uncoated plate and 10 a lysostaphin-coated plate. On day 84, the minipigs were again lavaged, followed by euthanasia. Bacterial load was quantified by colony-forming units (CFU). Immunological response was determined by neutrophils, as well as interleukins. Fracture healing was assessed radiologically. RESULTS: CFU showed significant difference between infected minipigs with an uncoated plate and minipigs with a lysostaphin-coated plate (p = 0.0411). The infection-related excessive callus formation and calcification was significantly greater in the infected animals with an uncoated plate than in animals with a lysostaphin-coated plate (p = 0.0164/p = 0.0033). The analysis of polymorphonuclear neutrophils and interleukins did not reveal any pioneering findings. CONCLUSION: This study confirms the minipig model for examining IAI. Furthermore, coating of plates using lysostaphin could be a promising tool in the therapeutic strategies of IAI. Future studies should focus on coating technology of implants and on translation into a clinical model.

Hydrogel delivery of lysostaphin eliminates orthopedic implant infection by Staphylococcus aureus and supports fracture healing.

Orthopedic implant infections are a significant clinical problem, with current therapies limited to surgical debridement and systemic antibiotic regimens. Lysostaphin is a bacteriolytic enzyme with high antistaphylococcal activity. We engineered a lysostaphin-delivering injectable PEG hydrogel to treat Staphylococcus aureus infections in bone fractures. The injectable hydrogel formulation adheres to exposed tissue and fracture surfaces, ensuring efficient, local delivery of lysostaphin. Lysostaphin encapsulation within this synthetic hydrogel maintained enzyme stability and activity. Lysostaphin-delivering hydrogels exhibited enhanced antibiofilm activity compared with soluble lysostaphin. Lysostaphin-delivering hydrogels eradicated S. aureus infection and outperformed prophylactic antibiotic and soluble lysostaphin therapy in a murine model of femur fracture. Analysis of the local inflammatory response to infections treated with lysostaphin-delivering hydrogels revealed indistinguishable differences in cytokine secretion profiles compared with uninfected fractures, demonstrating clearance of bacteria and associated inflammation. Importantly, infected fractures treated with lysostaphin-delivering hydrogels fully healed by 5 wk with bone formation and mechanical properties equivalent to those of uninfected fractures, whereas fractures treated without the hydrogel carrier were equivalent to untreated infections. Finally, lysostaphin-delivering hydrogels eliminate methicillin-resistant S. aureus infections, supporting this therapy as an alternative to antibiotics. These results indicate that lysostaphin-delivering hydrogels effectively eliminate orthopedic S. aureus infections while simultaneously supporting fracture repair.

Thermally triggered release of the bacteriophage endolysin CHAPK and the bacteriocin lysostaphin for the control of methicillin resistant Staphylococcus aureus (MRSA).

Staphylococcus aureus infections of the skin and soft tissue pose a major concern to public health, largely owing to the steadily increasing prevalence of drug resistant isolates. As an alternative mode of treatment both bacteriophage endolysins and bacteriocins have been shown to possess antimicrobial efficacy against multiple species of bacteria including otherwise drug resistant strains. Despite this, the administration and exposure of such antimicrobials should be restricted until required in order to discourage the continued evolution of bacterial resistance, whilst maintaining the activity and stability of such proteinaceous structures. Utilising the increase in skin temperature during infection, the truncated bacteriophage endolysin CHAPK and the staphylococcal bacteriocin lysostaphin have been co-administered in a thermally triggered manner from Poly(N-isopropylacrylamide) (PNIPAM) nanoparticles. The thermoresponsive nature of the PNIPAM polymer has been employed in order to achieve the controlled expulsion of a synergistic enzybiotic cocktail consisting of CHAPK and lysostaphin. The point at which this occurs is modifiable, in this case corresponding to the threshold temperature associated with an infected wound. Consequently, bacterial lysis was observed at 37°C, whilst growth was maintained at the uninfected skin temperature of 32°C.

Lysostaphin-coated titan-implants preventing localized osteitis by Staphylococcus aureus in a mouse model.

The increasing incidence of implant-associated infections induced by Staphylococcus aureus (SA) in combination with growing resistance to conventional antibiotics requires novel therapeutic strategies. In the current study we present the first application of the biofilm-penetrating antimicrobial peptide lysostaphin in the context of bone infections. In a standardized implant-associated bone infection model in mice beta-irradiated lysostaphin-coated titanium plates were compared with uncoated plates. Coating of the implant was established with a poly(D,L)-lactide matrix (PDLLA) comprising lysostaphin formulated in a stabilizing and protecting solution (SPS). All mice were osteotomized and infected with a defined count of SA. Fractures were fixed with lysostaphin-coated locking plates. Plates uncoated or PDLLA-coated served as controls. All mice underwent debridement and lavage on Days 7, 14, 28 to determine the bacterial load and local immune reaction. Fracture healing was quantified by conventional radiography. On Day 7 bacterial growth in the lavages of mice with lysostaphin-coated plates showed a significantly lower count to the control groups. Moreover, in the lysostaphin-coated plate groups complete fracture healing were observed on Day 28. The fracture consolidation was accompanied by a diminished local immune reaction. However, control groups developed an osteitis with lysis or destruction of the bone and an evident local immune response. The presented approach of terminally sterilized lysostaphin-coated implants appears to be a promising therapeutic approach for low grade infection or as prophylactic strategy in high risk fracture care e.g. after severe open fractures.

Chitosan-protein scaffolds loaded with lysostaphin as potential antistaphylococcal wound dressing materials.

AIMS: The development of technology for preparing chitosan-protein scaffolds loaded with lysostaphin, which potentially could be used as dressing for wound treatment and soft tissue infections caused by Staphylococcus aureus. METHODS AND RESULTS: The unique technology of chitosan solubilization using gaseous CO(2) instead of organic or inorganic acids was used for the incorporation of lysostaphin, the enzyme that exhibits bactericidal activity against staphylococci, within the structure of chitosan-protein sponges. The developed chitosan-protein scaffolds loaded with lysostaphin revealed high antistaphylococcal activity, which has been confirmed with a large (n = 143) collection of clinical (skin and wound infections) and animal (bovine mastitis) isolates of these bacteria, including MRSA. No change of bactericidal activity of the lyophilized materials has been observed during half-year storage at 4°C. CONCLUSIONS: The developed materials are potential candidates for preparing biologically active, antistaphylococcal wound dressing materials. SIGNIFICANCE AND IMPACT OF THE STUDY: Staphylococci belong to the most popular and most burdensome aetiological factors of wound and soft tissues infections. The developed chitosan-protein scaffolds loaded with lysostaphin could be a possible solution to problems associated with treatment of these infections.

Bioluminescence and 19F magnetic resonance imaging visualize the efficacy of lysostaphin alone and in combination with oxacillin against Staphylococcus aureus in murine thigh and catheter-associated infection models.

Staphylococci are the leading cause of hospital-acquired infections worldwide. Increasingly, they resist antibiotic treatment owing to the development of multiple antibiotic resistance mechanisms in most strains. Therefore, the activity and efficacy of recombinant lysostaphin as a drug against this pathogen have been evaluated. Lysostaphin exerts high levels of activity against antibiotic-resistant strains of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA). The therapeutic value of lysostaphin has been analyzed in two different clinically relevant in vivo models, a catheter-associated infection model and a thigh infection model. We infected mice with luciferase-expressing S. aureus Xen 29, and the efficacies of lysostaphin, vancomycin, oxacillin, and combined lysostaphin-oxacillin were investigated by determining numbers of CFU, detecting bioluminescent signals, and measuring the accumulation of perfluorocarbon emulsion at the site of infection by (19)F magnetic resonance imaging. Lysostaphin treatment significantly reduced the bacterial burden in infected thigh muscles and, after systemic spreading from the catheter, in inner organs. The efficiency of lysostaphin treatment was even more pronounced in combinatorial therapy with oxacillin. These results suggest that recombinant lysostaphin may have potential as an anti-S. aureus drug worthy of further clinical development. In addition, both imaging technologies demonstrated efficacy patterns similar to that of CFU determination, although they proved to be less sensitive. Nonetheless, they served as powerful tools to provide additional information about the course and gravity of infection in a noninvasive manner, possibly allowing a reduction in the number of animals needed for research evaluation of new antibiotics in future studies.

MRSA decolonization of cotton rat nares by a combination treatment comprising lysostaphin and the antimicrobial peptide ranalexin.

OBJECTIVES: To evaluate the in vivo effectiveness of a combination treatment containing ranalexin (a natural antimicrobial peptide) and lysostaphin (an antistaphylococcal endopeptidase) for reducing nasal burden of methicillin-resistant Staphylococcus aureus (MRSA). METHODS: The community-acquired MRSA strain S. aureus NRS384 (USA300-0114) was used in the present study because it is commonly isolated from human nares and it established consistent and reproducible colonization of cotton rat nares. This model was used to evaluate the efficacy of ranalexin/lysostaphin gels (0.1%-1% w/v; administered intranasally once or once per day for 3 consecutive days) for reducing nasal MRSA burden. Control animals were administered vehicle gel only (0.5% hydroxypropyl methylcellulose) or 2% mupirocin, which is used clinically for nasal decolonization of MRSA. Nasal MRSA burden was assessed at 192 h post-inoculation, which was at least 72 h after the final treatment had been administered. An additional study assessed the efficacy of 0.1% ranalexin/lysostaphin against a mupirocin-resistant MRSA strain (MUP20), which had been selected by serial passage of S. aureus NRS384 through subinhibitory concentrations of mupirocin. RESULTS: Gels containing 0.1% ranalexin/lysostaphin consistently reduced median nasal burden of MRSA to an extent similar to or greater than 2% mupirocin. Treatment with 0.1% ranalexin/lysostaphin was also effective against the MUP20 strain. There was evidence for only minimal irritancy in cotton rat nares administered three doses of 0.1% ranalexin/lysostaphin, suggesting that this agent is suitable for short-course therapy such as is employed currently for nasal decolonization with mupirocin. CONCLUSIONS: Ranalexin/lysostaphin could serve as an alternative to mupirocin for nasal decolonization of MRSA.

Anti-staphylococcal activities of lysostaphin and LytM catalytic domain.

BACKGROUND: Lysostaphin and the catalytic domain of LytM cleave pentaglycine crossbridges of Staphylococcus aureus peptidoglycan. The bacteriocin lysostaphin is secreted by Staphylococcus simulans biovar staphylolyticus and directed against the cell walls of competing S. aureus. LytM is produced by S. aureus as a latent autolysin and can be activated in vitro by the removal of an N-terminal domain and occluding region. RESULTS: We compared the efficacies of the lysostaphin and LytM catalytic domains using a newly developed model of chronic S. aureus infected eczema. Lysostaphin was effective, like in other models. In contrast, LytM was not significantly better than control. The different treatment outcomes could be correlated with in vitro properties of the proteins, including proteolytic stability, affinity to cell wall components other than peptidoglycan, and sensitivity to the ionic milieu. CONCLUSIONS: Although lysostaphin and LytM cleave the same peptide bond in the peptidoglycan, the two enzymes have very different environmental requirements what is reflected in their contrasting performance in mouse eczema model.

Development of chitosan-collagen hydrogel incorporated with lysostaphin (CCHL) burn dressing with anti-methicillin-resistant Staphylococcus aureus and promotion wound healing properties.

Methicillin-resistant Staphylococcus aureus (MRSA) have become increasingly prevalent as nosocomial pathogens, especially in burn patients, which is the leading cause of their death. A drug delivery system of chitosan-collagen hydrogel incorporated with lysostaphin (CCHL) based on the lysostaphin gauze was developed for MRSA infected burn wounds. CCHL scaffold consisted of numerous interconnected sphericles and tubular bodies with an average diameter of 100-200 µm, 20-60-fold swelling, high water retention capacity, and cell proliferation properties. The minimal inhibitory concentration of CCHL was 0.053 U/mL. By the second week after its application on MRSA infected third-degree burn wounds, no bacteria could be detected and the burn wounds had started healing. Therefore, CCHL should be studied further as a promising candidate of burn treatment dressing against MRSA infections for clinics.

Extension of nasal anti-Staphylococcus aureus efficacy of lysostaphin by its incorporation into a chitosan-o/w cream.

Nasal colonization of Staphylococcus aureus (S.aureus) is known as a significant risk factor for nosocomial infections, and clearance of its nasal colonization greatly reduces the risk. In the present study the preparation and characterizations of the chitosan-o/w cream incorporated with lysostaphin (CCL) were described. It showed that the concentration of incorporated lysostaphin had a direct relationship with its release behavior from the cream. It was rapid at 2 and 3.5 mg lysostaphin/g cream and of a more sustained pattern at 5 mg lysostaphin/g cream. Efficacy of lysostaphin released from the CCL cream to inhibit S.aureus growth was higher than that of lysostaphin delivery routinely treated, as demonstrated by the reduction of the mucociliary transport rate (MTR) in contrast to the control graphite particles (p < 0.05). Therefore, it is concluded that drug delivery by the CCL holds its potential as a local nasal anti-S.aureus infection.

Sustained anti-staphylococcal effect of lysostaphin in the rabbit aqueous humor.

PURPOSE: Staphylococcus aureus is an important cause of ocular infections including endophthalmitis. The purpose of this study was to determine the ability of a relatively large molecule, such as lysostaphin, to remain in the rabbit aqueous humor for extended periods while retaining its bactericidal activity. METHODS: Lysostaphin, gatifloxacin, or Tris-buffered saline (TBS) was injected into the rabbit anterior chamber. Aqueous humor was sampled at 0.5, 1, 2, 3, and 4 days after injection, and then assayed for bactericidal activity against S. aureus. The anterior chamber of treated eyes was also challenged 2 days after treatment by an infection of S. aureus. The surviving bacteria were quantified to determine bactericidal effectiveness in the anterior chamber. The aqueous humor of lysostaphin injected eyes was assayed by western blot for the presence of the molecule 2 days post-injection. RESULTS: The bactericidal activity of lysostaphin was confirmed by lysis of S. aureus and sensitivity to zinc. Eyes injected with lysostaphin showed no adverse reactions. Aqueous humor of gatifloxacin injected eyes demonstrated no greater effectiveness than that of TBS injected eyes in vitro at any time point assayed, whereas lysostaphin injected eyes retained potent bactericidal activity for at least 3 days. In an in vivo challenge, the anterior chamber of lysostaphin injected eyes retained significant bactericidal activity for at least 2 days after treatment, whereas gatifloxacin injected eyes demonstrated no significant difference from those injected with TBS. Western blot analysis demonstrated the presence of lysostaphin in the aqueous humor 2 days post-injection. CONCLUSIONS: Lysostaphin demonstrated the ability to remain in the aqueous humor for days while maintaining its bactericidal activity, an indication that a high molecular weight antimicrobial can provide prolonged prophylactic protection of the anterior chamber.

Lysostaphin eradicates established Staphylococcus aureus biofilms in jugular vein catheterized mice.

OBJECTIVES: Staphylococcus aureus infections associated with indwelling devices can be very difficult to treat due to the recalcitrant nature of bacterial biofilms to conventional antibiotics. Lysostaphin has been shown to clear S. aureus biofilms in vitro, and in this study we determined whether lysostaphin could also eradicate established S. aureus biofilms on implanted jugular vein catheters in mice. METHODS: Jugular vein catheterized mice (four to six per group) challenged with S. aureus developed multiorgan infection and biofilm infections on the catheters. The infected mice with established biofilms received various doses of recombinant lysostaphin through the catheters, administered up to three times daily for up to 4 days. Some mice also received lysostaphin combined with nafcillin. Following treatment, mice were sacrificed and cfu on the catheter and in the liver and heart were determined. In another set of experiments, implanted jugular vein catheters in mice were pre-instilled with lysostaphin to determine whether this pre-treatment would protect the mice from biofilm infection. RESULTS AND CONCLUSIONS: Lysostaphin administered at 15 mg/kg in combination with 50 mg/kg nafcillin three times per day for 4 days eradicated established S. aureus, including methicillin-resistant S. aureus, biofilms from implanted catheters and sterilized heart and liver infections of S. aureus-infected mice. Furthermore, a single pre-instillation of 10 mg/kg lysostaphin in catheters completely protected catheterized mice from a subsequent biofilm infection. These results demonstrate that lysostaphin is an effective treatment as well as prophylaxis for S. aureus biofilms on indwelling catheters.

Treatment of methicillin-resistant Staphylococcus aureus in neonatal mice: lysostaphin versus vancomycin.

S. aureus is a significant cause of late-onset sepsis in neonates. Increasing antibiotic resistance, however, requires additional treatment options. Lysostaphin, an endopeptidase, has that potential. The objective of this study is to compare lysostaphin versus vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) in a neonatal mouse model. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against MRSA strain USA300 were determined using standard methods. To determine pharmacokinetics, neonatal pups received either vancomycin or lysostaphin intraperitoneal and serum samples were obtained. To evaluate efficacy, pups were infected s.c. and littermates randomized to receive either saline, vancomycin, or lysostaphin intraperitoneal. Pups were observed for survival and growth. Quantitative blood cultures were obtained 24 h after infection. The MIC/MBC for vancomycin and lysostaphin were 0.71/1.19 microg/mL and <0.008/0.015 microg/mL, respectively. Mean lysostaphin concentrations ranged from 2.34 to 8.92 microg/mL. Mean vancomycin concentrations ranged from 1.72 to 11.2 microg/mL. Lysostaphin improved survival compared with placebo (p < 0.00001) and vancomycin (p < 0.03). There was no significant difference in growth among the groups. All treatment regimens resulted in less bacteremia compared with placebo (p < 0.0001). Lysostaphin appears to be more effective than vancomycin in treating MRSA in a neonatal model.

Lysostaphin in treatment of neonatal Staphylococcus aureus infection.

This study describes lysostaphin's effect against methicillin-sensitive Staphylococcus aureus in suckling rats. Standard techniques determined minimal inhibitory and bactericidal concentrations, pharmacokinetics, and efficacy. The numbers of surviving rats after vancomycin, oxacillin, and lysostaphin treatment were comparable and were different from that of controls (P < 0.00001). Lysostaphin appears effective in the treatment of neonatal S. aureus infection.

The effectiveness of lysostaphin therapy for experimental coagulase-negative Staphylococcus endophthalmitis.

PURPOSE: To quantitatively determine the effectiveness of lysostaphin therapy for experimental endophthalmitis mediated by coagulase-negative Staphylococcus species, the leading cause of postsurgical endophthalmitis. METHODS: Minimal inhibitory concentrations (MIC) of lysostaphin were determined for 54 isolates representing the following species: S. epidermidis, S. warneri, S. haemolyticus, S. cohnii, S. simulans, and S. capitis. The effectiveness of lysostaphin therapy was tested in an experimental model of endophthalmitis by intravitreally injecting log phase bacteria (100 colony-forming units; cfu) into rabbit eyes (n = 3 eyes per group). At 8 hr postinfection (PI), lysostaphin (250 microg) was injected intravitreally, and the number of cfu/ml of vitreous was determined at 24 hr PI. RESULTS: Average MIC for S. epidermidis was 0.7 microg/ml for 90% of the 33 strains tested. Six methicillin-resistant strains of S. epidermidis (MRSE) had an average MIC of 0.74 micro g/ml. All other species had MIC values of =1.1 microg/ml, except for one strain of S. capitis (MIC = 15.6 microg/ml) and one S. haemolyticus (MIC = 1.41 microg/ml). At 24 hr PI, all untreated eyes had between 5.7 and 8.08 log cfu/ml vitreous humor. Treatment with lysostaphin significantly reduced the cfu/ml as compared with untreated eyes for 13 strains tested in vivo (p = 0.020), but not for two S. haemolyticus strains (p = 0.13), two MRSE strains (p = 0.544), or one S. cohnii strain (p = 0.1366). Treatment with lysostaphin reduced the cfu/ml of methicillin-sensitive S. epidermidis strains by 6 logs; for S. warneri, there was a 2 log reduction; and for the other species a 4 log reduction in cfu/ml relative to untreated eyes. CONCLUSIONS: Lysostaphin was mostly effective in treating coagulase-negative staphylococcal experimental endophthalmitis.

Genetically enhanced cows resist intramammary Staphylococcus aureus infection.

Mastitis, the most consequential disease in dairy cattle, costs the US dairy industry billions of dollars annually. To test the feasibility of protecting animals through genetic engineering, transgenic cows secreting lysostaphin at concentrations ranging from 0.9 to 14 micrograms/ml [corrected] in their milk were produced. In vitro assays demonstrated the milk's ability to kill Staphylococcus aureus. Intramammary infusions of S. aureus were administered to three transgenic and ten nontransgenic cows. Increases in milk somatic cells, elevated body temperatures and induced acute phase proteins, each indicative of infection, were observed in all of the nontransgenic cows but in none of the transgenic animals. Protection against S. aureus mastitis appears to be achievable with as little as 3 micrograms/ml [corrected] of lysostaphin in milk. Our results indicate that genetic engineering can provide a viable tool for enhancing resistance to disease and improve the well-being of livestock.

Extended nasal residence time of lysostaphin and an anti-staphylococcal monoclonal antibody by delivery in semisolid or polymeric carriers.

PURPOSE: Eradication of Staphylococcus aureus nasal colonization reduces the risk of nosocomial and community acquired infections with this organism. This study describes the formulation and use of lysostaphin and BSYX-A110, an anti-lipoteichoic acid monoclonal antibody, for eradication of S. aureus nasal colonization. METHODS: Lysostaphin was formulated into a hydrophilic cream that forms an emulsion with the secretions of the nasal mucosa, and aqueous formulations of BSYX-A110 were made containing the mucoadhesive polymers polystyrene sulfonate and chitosan. Intranasal pharmacokinetics of the drugs was measured in mice and cotton rats. RESULTS: Lysostaphin formulated in the cream increased nasal retention of the drug by 10-fold at 3 h post-cream installation and 50-fold at 24 h as compared to lysostaphin in saline drops. Furthermore, the levels of lysostaphin in the nose 24 h post-cream instillation are still above the minimum bactericidal concentration for most bacterial strains. The liquid polymer formulations also resulted in prolonged retention of antibody in the nose, with 4-fold higher levels at 3 h post-instillation as compared to antibody in saline drops. CONCLUSIONS: These results demonstrate that cream and polymer delivery systems significantly decrease the clearance rate of lysostaphin and BSYX-A110 from the nose, thereby enhancing their therapeutic potential for eradicating S. aureus nasal colonization.

Lysostaphin cream eradicates Staphylococcus aureus nasal colonization in a cotton rat model.

The anterior nares are a primary ecologic niche for Staphylococcus aureus, and nasal colonization by this opportunistic pathogen increases the risk of development of S. aureus infection. Clearance of S. aureus nasal colonization greatly reduces this risk. Mupirocin ointment is the current standard of care for clearance of S. aureus nasal colonization, but resistance to this antibiotic is emerging. Lysostaphin is a glycylglycine endopeptidase which specifically cleaves the cross-linking pentaglycine bridges in the cell walls of staphylococci. Lysostaphin is extremely staphylocidal (MIC at which 90% of isolates are inhibited, 0.001 to 0.064 micro g/ml) and rapidly lyses both actively growing and quiescent S. aureus. This study demonstrates that a single application of 0.5% lysostaphin (actual dose, approximately 150 micro g of lysostaphin), formulated in a petrolatum-based cream, dramatically reduces S. aureus nasal colonization in 100% of animals tested and eradicates S. aureus nasal colonization in 93% of animals in a cotton rat model. A single dose of lysostaphin cream is more effective than a single dose of mupirocin ointment in eradicating S. aureus nasal colonization in this animal model. The lantibiotic peptide nisin, which has potent in vitro antistaphylococcal activity, was ineffective in reducing staphylococcal nasal carriage in this model. Nasal colonization was not reduced after three treatments with 5% nisin ( approximately 1,500 micro g/dose) in any of the treated animals. Lysostaphin formulated in cream may prove to be a superior alternative to mupirocin ointment for clearance of S. aureus nasal colonization.

[Methicillin-resistant Staphylococcus aureus infection and its treatment in burned patients].

Burn wound and systemic infections caused by methicillin-resistant Staphylococcus aureus (MRSA) were analysed in 95 patients. Results showed that both 95 (92.2%) out of 103 strains of Staphylococcus aureus isolated from burn wound and all 17 strains from blood were MRSA. Wound MRSA infection could be found in patients with variety of severity and in any kind of wound, while systemic MRSA infection was often occurred in extensive burn patients. The isolated MRSA were most resistant to cephalosporins and sensitive to vancomycin. In order to control wound MRSA infection, Lysostaphin which is active against these organisms could be used as a topical antimicrobial.

Lysostaphin: immunogenicity of locally administered recombinant protein used in mastitis therapy.

A recombinant bactericidal protein, recombinant lysostaphin (r-lysostaphin), that may be useful as an intramammary therapeutic for Staphylococcus aureus mastitis in dairy cattle, was evaluated for immunogenicity to various hosts. Although immunogenicity could be demonstrated in a variety of other species when administered parenterally, oral administration failed to elicit a significant immunological response. Similarly, intramammary infusion of r-lysostaphin failed to elicit significant serum titers in the bovine until 18-21 infusions were administered (total administered dose of 2-3 g of protein). Antibody titers from dairy cattle which did develop an immune response were predominantly of the IgG1 subclass. Dairy cattle with significant anti-lysostaphin titers showed no deleterious symptoms (anaphylaxis, etc.) upon subsequent infusion, and these titers did not effect the in vitro bacteriostatic activity of r-lysostaphin. Intramammary infusion of r-lysostaphin does not elicit any observable effects on the host animal or on the potential efficacy of the recombinant molecule. Intramammary recombinant proteins may be suitable effective and safe infusion products that provide an alternative to classical antibiotic therapy.