A new target for Staphylococcus aureus associated with keratitis

Staphylococcus aureus is a leading cause of keratitis, with an increased number of isolates exhibiting antibiotic resistance. Therefore, we need to understand the present situation regarding drug-resistant S. aureus in the ocular site. It has been shown that 35% of S. aureus isolates from ocular sites are methicillin-resistant Staphylococcus aureus (MRSA). MRSA isolates from ocular sites have a high rate of multiple mutations and high levels of resistance against fluoroquinolones. Wall teichoic acids (WTAs) are major polyanionic polymers in the cell wall of S. aureus and are likely to be important in the pathogenesis of eye infection. A new compound, targocil, was recently shown to function as a bacteriostatic inhibitor of WTA biosynthesis in S. aureus. The minimum inhibitory concentration (MIC) at which 90% of the keratitis isolates are inhibited (MIC90) by targocil was 2 μg/mL for both MRSA and methicillin-sensitive Staphylococcus aureus. Targocil exhibited little toxicity at concentrations near the MIC, with increased toxicity at higher concentrations and longer exposure times. Targocil inhibited intracellular bacteria in the presence of human corneal epithelial cells to a greater extent than vancomycin. Targocil-resistant strains exhibited a significantly reduced ability to adhere to human corneal epithelial cells (P < 0.001). The WTA biosynthesis pathway of S. aureus appears to be a viable target for preventing keratitis caused by strains of this bacterium.     

A high incidence of Staphylococcus aureus colonization in the external eyes of patients with atopic dermatitis

OBJECTIVE: To determine the frequency distribution of bacteria on the external surface of eyes of patients with atopic dermatitis (AD) and to investigate the relationship between the frequency of bacterial colonization and the grade of atopy or ocular diseases associated with AD. DESIGN: Comparative cross-sectional study. PARTICIPANTS: Thirty-six AD patients (mean age, 24.5 years) and 16 nonatopic, age-matched control participants (mean age, 25.5 years). INTERVENTION: The eyelid margins and conjunctival sacs were scraped with sterile swabs. These samples were inoculated into aerobic and anaerobic culture media. MAIN OUTCOME MEASURES: The frequency distribution of bacteria isolated from the eyelid margins and conjunctival sacs. RESULTS: Bacteria isolated from AD patients were: Staphylococcus aureus in 21 of 36 patients (including methicillin-resistant Staphylococcus aureus in two patients); Staphylococcus epidermidis in two patients (including methicillin-resistant Staphylococcus epidermidis in one patient); other coagulase-negative Staphylococcus in six patients;alpha-streptococcus in three patients; Corynebacterium species in three patients; Neisseria species in two patients; and Propionibacterium acnes in one patient. From the nonatopic control participants, we isolated S. aureus in one patient, S. epidermidis in two patients and alpha-streptococcus in one patient. S. aureus was isolated from 67% of the AD patients, and any type of bacteria was isolated from 86% of the patients. These rates were significantly higher than those of nonatopic control participants (6% S. aureus and 25% any bacteria). There was no significant relationship between the frequency distribution of bacteria and the grade of atopy or associated ocular diseases. CONCLUSIONS: High rates of bacterial colonization, especially S. aureus, were found in the conjunctival sacs and eyelid margins of AD patients. In case management of AD patients, this unique distribution of bacteria must be carefully considered.     

Pathogenesis of Staphylococcus in the rabbit anterior chamber

PURPOSE: To investigate the host defense against Staphylococcus in the rabbit anterior chamber. METHODS: The bactericidal activity of rabbit aqueous humor was investigated in vitro. Rabbit anterior chambers were injected with viable Staphylococcus aureus or Staphylococcus epidermidis (1,000 or 500,000 colony-forming units [CFU]), killed bacteria, culture supernatants of either organism, or purified S. aureus alpha-toxin. CFU as well as phospholipase (PLA(2)) and myeloperoxidase (MPO) activities of aqueous humor were determined up to 25 hours postinfection (PI). RESULTS: The number of viable S. aureus or S. epidermidis was significantly reduced when incubated with aqueous humor for 30 minutes (P 相似文献   

Intracameral Vigamox (moxifloxacin 0.5%) is non-toxic and effective in preventing endophthalmitis in a rabbit model

PURPOSE: To determine whether Vigamox (moxifloxacin 0.5% ophthalmic solution) can be safely injected intracamerally to prevent Staphylococcus aureus endophthalmitis in a rabbit model. DESIGN: Animal study. METHODS: The safety and bactericidal-effectiveness of Vigamox were evaluated in three stages using 189 New Zealand White rabbits. (Stage 1) The toxicity of two intravitreal doses of Vigamox (moxifloxacin 500, 250 microg) was compared with vancomycin (1 mg) and saline. (Stage 2) A reproducible rabbit model of Staphylococcus aureus endophthalmitis was established. (Stage 3) The bactericidal effect of intracameral Vigamox (moxifloxacin 500, 250, 125, 50 microg) was compared with vancomycin (1 mg) and saline. Intracameral antibiotic therapy commenced immediately after Staphylococcus aureus intravitreal challenge (5000 cfu). Toxicity was evaluated by masked clinical examination using a slit-lamp, an indirect ophthalmoscope, and corneal-ultrasound pachymetry. The clinical examination included the exterior eye, cornea, anterior chamber, vitreous, and retina. The presentations were graded on a severity scale of 0, 0.5, 1, 2, and 3. The bactericidal efficacy was determined using intracameral colony counts. RESULTS: In the toxicity studies without bacterial challenge, the clinical scores of rabbits injected intracamerally with Vigamox were statistically equivalent to rabbits given intracameral vancomycin or saline. In the efficacy studies, eyes treated intravitreally with Vigamox, at all doses, or vancomycin were negative for Staphylococcus aureus and nontreated controls remained culture-positive. CONCLUSIONS: Vigamox appears to be nontoxic for intracameral injection and effective in preventing experimental endophthalmitis in the rabbit model. Further studies will determine the clinical role of intracameral Vigamox for surgical prophylaxis and postoperative therapy.     

Study of the resistance pattern and alteration in the conjunctival flora of patients exposed to repeated antibiotics

AIM: To investigate and analyze the changes in the conjunctival flora of patients exposed to repeated antibiotic usage. In addition, determining the effects of this repeated exposure on the resistance pattern of the conjunctival flora. METHODS: This study included 40 patients, admitted to the Retina Unit of the Research Institute of Ophthalmology. All chosen patients had a minimum of 4 consecutive, monthly intravitreal injections (IVI), some were extended to 6mo or 1y as required. The patients were randomly divided into 3 groups and each group received one kind of antibiotic which was either ofloxacin, moxifloxacin or ceftazidime. All bacterial isolates were tested for antibiotic susceptibility using Kirby-Bauer disc diffusion technique. RESULTS: In this study the conjunctival normal flora at base line culture varied from a predominance of Staphylococcus epidermidis (51.2%), followed by Staphylococcus aureus 14% to Micrococcus species 12.8% and other coagulase negative staphylococci (CONS) 13%. Our results showed an increase in the percentage of Staphylococcus epidermidis among ceftazidime treated eyes during the four visits in comparison to baseline cultures of patients randomized to ceftazidime. In contrast, there was no noticeable increase in Staphylococcus aureus percentage from baseline. In fluoroquinolone treated eyes, we also observed an increase in percentage of Staphylococcus epidermidis from base line. In contrast to ceftazidime treated eyes, the Staphylococcus aureus percentage in fluoroquinolone treated eyes showed an increase from baseline. However, the pattern of the ocular flora composition changed with the exposure to the old and newer generation of fluoroquinolones. We noticed an increase of Staphylococcus epidermidis in moxifloxacin treated eyes than that in ofloxacin treated eyes from baseline. There was no observed difference in the pattern of Staphylococcus aureus regarding exposure to older and newer generations of fluoroquinolones. CONCLUSION: Repeated use of ophthalmic antibiotics not only alters the composition of the normal ocular flora, but also selects for resistant strains.     

Efficacy of topical chloramphenicol and tobramycin ophthalmic solutions in preventing severe Staphylococcus aureus keratitis in rabbits

Various marketed chloramphenicol ophthalmic solutions were compared and various dilutions of Tobrex Ophthalmic Solution were tested for effectiveness in a Staphylococcus aureus rabbit keratitis model. Anesthetized rabbits were each infected intracorneally with 10(4) Staphylococcus aureus ATCC 29737 cells. Treatment groups consisted of five or six rabbits (10 or 12 eyes) per group. One group of rabbits was infected but not treated (Positive Control Group). Topical dosing of commercially available ophthalmic solutions was accomplished by depositing 0.1 mL of a color-coded test solution into the lower cul-de-sac of each eye. Dosing begin one hour after the mid-infection time and continued for a total of nine hourly treatments. Twenty-four hours after infection the rabbit eyes were graded (masked) using standard slit-lamp scoring procedures. The slit-lamp scores for five of eight ocular parameters were used to calculate an eye score value for each rabbit eye. The five ocular parameters were selected, based on previous Stepwise Discriminant Computer Analysis of over 300 rabbit eyes infected with Staphylococcus aureus ATCC 29737 and treated with various antibiotics. The eye score values for each group were averaged and the treatments were compared for significant differences in efficacy using the nonparametric, Wilcoxon-Mann-Whitney Rank Sum Test.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ciprofloxacin and levofloxacin resistance among methicillin-sensitive Staphylococcus aureus isolates from keratitis and conjunctivitis

PURPOSE: The majority of Staphylococcus aureus isolated from ocular infections are methicillin sensitive (MSSA). Fluoroquinolone resistance among methicillin- resistant Staphylococcus aureus is well known but not among MSSA. In this study we investigate the emergence of fluoroquinolone (ciprofloxacin, levofloxacin) resistance among methicillin-sensitive Staphylococcus aureus isolates from keratitis and conjunctivitis. DESIGN: Cross-sectional study. METHODS: Minimal inhibitory concentration susceptibility profiles for 1230 S. aureus isolates from keratitis and conjunctivitis were analyzed. Historical and current rates of emerging fluoroquinolone resistance for methicillin-resistant (MRSA) and methicillin-sensitive isolates (MSSA) were evaluated. Sensitivity patterns for vancomycin and gentamicin were also documented. RESULTS: Ciprofloxacin resistance among corneal and conjunctival S. aureus isolates during the first 6 years after its introduction (baseline) (1990-1995) was 8% and ranged from 3% to 11%. The rate for the most recent 6 years (current) (1996-2001) was 20.7%. Baseline ciprofloxacin resistance for MSSA isolates was 2% vs 55.8% for MRSA. The current resistance rate for MSSA is 5% vs 83.7% for MRSA. The general resistance rate from January 2000 to December 2001 for levofloxacin was 25.5% vs 33.2% for ciprofloxacin (P =.13). The levofloxacin-resistance rate for MSSA was 4.7% vs 11.9% for ciprofloxacin (P =.05). In MRSA isolates, a higher resistance rate was found for ciprofloxacin (95.7%) vs levofloxacin (82.1%) (P =.04). No resistance for vancomycin was documented for any of the S. aureus isolates. Gentamicin susceptibility for MSSA was 99% and MRSA was 86%. CONCLUSIONS: Ciprofloxacin and levofloxacin resistance among methicillin-sensitive S. aureus corneal and conjunctival isolates is increasing. This is of concern because it narrows treatment choices for the management of these common ocular infections.     

Comparison of potential pathogenic traits of staphylococci that may contribute to corneal ulceration and inflammation.

Staphylococcus epidermidis and Staphylococcus aureus are two of the commonest bacteria isolated from corneal ulcers. The aim of the current investigation was to determine the frequency of potentially pathogenic traits in the two staphylococcal species. Strains of both species, some isolated from eyes during active corneal inflammation, were screened for their ability to degrade a variety of proteins and hyaluronic acid and the production of cytotoxins. S. aureus produced more tissue-destructive enzymes than the S. epidermidis. S. aureus strains more commonly synthesized the cytotoxin, alpha-toxin. The production of elastase was more common among S. aureus strains isolated from ulcerative events. The production of alpha-toxin was inversely correlated with isolation from keratitis. This study has demonstrated that S. aureus is better equipped with a range of potentially damaging enzymes and toxins than S. epidermidis and that S. aureus elastase may be involved in the production of corneal ulcers.     

Spectrum of eye disease caused by methicillin-resistant Staphylococcus aureus

PURPOSE: To compare the clinical features and antibiotic susceptibility of ocular methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). DESIGN: Cross-sectional study. METHODS: The Proctor clinical laboratory database was reviewed to identify all ocular isolates of S. aureus collected between July 1, 1998 and July 31, 2006. RESULTS: Of 915 S. aureus isolates, there were 88 MRSA isolates in 41 different patients. The proportion MRSA increased from 4.1% in 1998 to 1999 to 16.7% in 2005 to 2006. A total of 78.0% of patients with MRSA had blepharoconjunctivitis, 2.4% had cellulitis, 2.4% had dacryocystitis, 14.6% had keratitis, and 2.4% had endophthalmitis. The diagnoses associated with MSSA were not statistically different. A total of 63.6% of MRSA isolates were sensitive to bacitracin, 100% to vancomycin, 14.8% to ciprofloxacin, 14.8% to erythromycin, 97.7% to sulfisoxazole, and 93.2% to tetracycline. CONCLUSIONS: MRSA has become a more common ocular pathogen but, as with MSSA, causes mild disease. MRSA should be treated with vancomycin.     

新生儿急性细菌性结膜炎细菌培养结果分析

目的：分析新生儿急性细菌性结膜炎的细菌培养结果，探讨其病原菌和耐药性的变迁，寻找有效的抗生素，为临床合理用药提供依据。方法：对63例(97只眼)经临床诊断为新生儿急性细菌性结膜炎患儿的结膜囊分泌物标本进行细菌培养，同时对培养阳性菌株的种类及药物敏感试验结果进行分析。结果：新生儿急性细菌性结膜炎的细菌平均检出率为78．4％。不同年份的细菌检出率变化无明显差异(x^2＝0．79，P＞0．05)。新生儿急性细菌性结膜炎的致病菌，由以金黄色葡萄球菌、草绿色链球菌为主，转变为以淋球菌、表皮葡萄球菌和腐生葡萄球菌为主。大多数细菌对环丙沙星敏感，对氯霉素耐药。结论：对新生儿急性细菌性结膜炎患儿的结膜囊分泌物标本进行细菌培养、药物敏感试验既助于提高临床治疗，又可防止临床滥用抗生素、造成耐药菌株的增加。     

Recurrent Staphylococcus aureus chalazia in hyperimmunoglobulinemia E (Job's) syndrome

PURPOSE: To report a case of recurrent Staphylococcus aureus chalazia in a patient with hyperimmunoglobulinemia E syndrome (Job's Syndrome). DESIGN: Case report. METHODS: Three separate surgical incisions and curettages of multiple, recurrent chalazia of the right upper eyelid were performed over a course of 3 months. Cultures and pathologic specimens were obtained. Postoperative treatment consisted of oral erythromycin and amoxicillin/clavulonate, topical tobramycin/dexamethasone ointment, and warm compresses. RESULTS: Pathology of the tarsus confirmed the diagnosis of multiple chalazia. Cultures of the chalazia contents were positive for Staphylococcus aureus. No further recurrence was observed following the third surgical procedure over a 3-month follow-up period. CONCLUSION: Characteristic Staphylococcus aureus skin infections in immunodeficient patients with hyperimmunoglobulinemia E syndrome can involve the eyelids and may be recurrent despite appropriate medical and surgical therapy.     

Recurrent methicillin-resistant Staphylococcus aureus wound ulcer after clear-cornea cataract surgery.

PURPOSE: To present a case of recurrent, methicillin-resistant Staphylococcus aureus (MRSA) wound ulcer after clear-cornea cataract surgery. METHODS: Case report. RESULTS: An 82-year-old man underwent an uncomplicated phacoemulsification procedure with posterior-chamber intraocular lens (PCIOL) implantation. Two weeks after surgery, a corneal ulcer was present at the wound site. Corneal tissue sample cultures produced methicillin-resistant Staphylococcus aureus. The ulcer responded to high-dose vancomycin but recurred twice as vancomycin was tapered. Lamellar keratectomy with conjunctival flap was performed at 6 months after surgery, with no additional ulcer recurrence. CONCLUSIONS: Wound infection after clear-cornea cataract surgery occurs infrequently. Management of these infections, however, can provide challenging clinical decisions.     

Methicillin resistance of bacteria isolated from vitreous fluid from patients undergoing vitrectomy.

PURPOSE: The aim of this study was to compare the resistance patterns of bacteria in vitreous fluid from patients undergoing vitrectomy for diagnostic reasons, with bacteria of other nosocomial infections. METHODS: Vitreous fluid samples (n=144) were obtained from 133 patients undergoing vitrectomy for endophthalmitis, and 11 for uveitis as suspected endophthalmitis. They were Gram stained and cultured. Antibiotic susceptibility tests were run on all isolates. RESULTS: Gram stains were positive in 45/144 cases (31%), among which 38/45 (84%) were confirmed by a positive culture. Cultures were positive in 74/144 patients (51%) with mainly coagulase-negative staphylococci (n = 44) and Staphylococcus aureus (n = 13). In 133 patients endophthalmitis occurred after lens implantation (80 cases) and in 53 cases there was another origin (e.g. corneal transplantation, endogenous). In 26/80 post-lens implantation infections, culture remained negative; 32 infections occurred with coagulase-negative staphylococci, 10 with Staphylococcus aureus, 9 with streptococci and 3 with gram-negative bacteria. For endophthalmitis, ophthalmologists in our institution give an intraocular injection of vanccmycin and ceftazidim after vitrectomy. Among the 44 isolates of coagulase-negative staphylococci, 12 (27%) were resistant to methicillin. This is in contrast to other hospital-related coagulase-negative staphylococcus infections in general, and the resistance rate is 75% in our hospital. Only 2/13 Staphylococcus aureus isolates were methicillin-resistant. CONCLUSIONS: We conclude that isolates of coagulase-negative staphylococci from vitreous fluid are less resistant to methicillin than those isolated in other nosocomial infections.     

螺旋藻多糖提取物滴眼液对兔金黄色葡萄球菌性角膜炎的治疗作用

目的：:观察局部应用螺旋藻多糖提取物（PSP）对大白兔金黄色葡萄球菌性角膜炎的治疗效果。方法：:实验研究。从钝顶螺旋藻干粉中提取PSP,并制备0.01% PSP滴眼液。在45只大白兔右眼角膜中央采用基质注射针基质注射5 μl金黄色葡萄球菌菌液[（ATCC25923,约100个菌落形成单位（CFU）],构建兔金黄色葡萄球...     

In vitro adherence of bacteria to intraocular lenses of different materials

OBJECTIVE: To compare the in vitro adherence of different bacteria onto the surface of various intraocular lenses (IOLs). METHOD: Electron microscopic and bacterial culture quantitative methods were used to study the adherence of Staphylococcus (S) epidermidis, Staphylococcus aureus and Pseudomonas (P) aeruginosa onto the surface of PMMA and other three foldable IOL materials (HEMA, ACRY, SI). RESULTS: S. Epidermidis: HEMA < ACRY < SI < PMMA; S. aureus: HEMA was the least and PMMA was the most, no significant difference between ACRY and SI IOLs; P. aeruginosa: HEMA was the least while no significant difference among PMMA, SI and ACRY IOLs (P > 0.05). CONCLUSION: The foldable IOLs have the potent ability to reduce the infectious endophthalmitis after surgery of extraction of cataract with IOL implantation.     

Successful treatment of methicillin-resistant Staphylococcus aureus Keratitis with topical ciprofloxacin.

Ciprofloxacin is a new quinolone antibiotic with a broad spectrum of activity against most aerobic gram-positive and gram-negative bacteria. Topical ciprofloxacin (3 mg/ml) was used to treat bacterial keratitis caused by methicillin-resistant strains of Staphylococcus aureus in two patients. Both corneal ulcers had been previously treated with other antibiotics without success. Topical ciprofloxacin was curative in both cases. The authors recommend the use of topical ciprofloxacin for methicillin-resistant S. aureus keratitis.     

The relationship between Staphylococcus aureus and atopic keratoconjunctivitis

PURPOSE: To investigate the role of Staphylococcus aureus in patients with vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) complicated by atopic dermatitis (AD). SUBJECTS AND METHODS: Microbiological culture from the conjunctival sac of acute exacerbated patients with VKC and AKC complicated by AD was performed. The subjects were 29 patients (31 eyes) with VKC and AKC who showed acute exacerbated clinical symptoms of conjunctivitis. Antigen specific IgE antibodies to staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) in serum were also examined. In this study, the patients were divided into two groups: An AD group consisting of 22 patients with VKC and AKC complicated by AD, and a control group consisting of 8 patients with allergic conjunctivitis without AD. We also examined SEA/SEB specific IgE antibody in tears from the 5 patients who underwent bacteriological examinations of the conjunctival sac at the same time. RESULTS: Twenty-seven out of 31 eyes were gram-positive in the bacteriological culture from the conjunctival sac (87.1%). Staphylococcus aureus was detected in 21 out of the 27 eyes (77.8%). In the AD group, 2 of the 22 cases were gram-positive for serum SEA specific IgE antibodies, 2 cases of the 22 cases were gram-positive for SEB specific IgE antibodies, and 9 cases were gram-positive for both SEA and SEB specific IgE antibodies. Serum SEA and SEB specific IgE antibodies were all gram-negative in the control group. Either SEA or SEB specific IgE antibody in tears was detected in all of the above 5 patients who underwent bacteriological examinations of the conjunctival sac, and 4 of the 5 were gram-positive. Staphylococcus aureus was isolated in 3 out of the 5 patients, and 1 case was gram-negative. CONCLUSION: Staphylococcus is one of the exacerbating factors in VKC and AKC. It is important to evaluate both bacteriological examinations of the conjunctival sac and SEA/SEB specific IgE in tears.     

Effects of alpha-toxin-deficient Staphylococcus aureus on the production of peripheral corneal ulceration in an animal model

PURPOSE: To examine the role of Staphylococcus aureus alpha-toxin in contact lens-induced peripheral ulceration (CLPU). MATERIALS AND METHODS: Proteolytic enzyme, hyaluronidase, alpha-toxin, and beta-toxin production by S. aureus 8325-4 and its alpha-toxin-deficient mutant (S. aureus DU1090) were examined. Using a rabbit model of CLPU, animals were fitted with hydrogel contact lenses colonized by either S. aureus 8325-4 or the mutant strain. The clinical presentation, bacterial cultures, and histology of the ulceration were examined. RESULTS: Both strains of S. aureus produced similar levels of caseinase, gelatinase, elastase, hyaluronidase, and beta-toxin. S. aureus DU1090 induced weaker haemolysis of rabbit blood cells than S. aureus 8325-4. Ulceration in the S. aureus DU1090 eye was less frequent and less severe than that caused by S. aureus 8325-4. CONCLUSIONS: The enzyme production profile of S. aureus DU1090 was similar to the parent strain. S. aureus strains may produce CLPU-like lesions irrespective of alpha-toxin production, but severe infectious lesions are produced only in the presence of alpha-toxin.     

紫外线-核黄素光动力疗法对眼科常见致病细菌的体外杀菌作用

背景 金黄色葡萄球菌、表皮葡萄球菌和铜绿假单胞菌是眼科的常见致病菌,研究最佳杀菌方法对眼科的临床工作具有重要意义. 目的 观察紫外线-核黄素光动力疗法（PDT）对眼科常见致病细菌的体外杀菌作用. 方法 分别取金黄色葡萄球菌、表皮葡萄球菌和铜绿假单胞菌冻存菌各10株接种于血培养皿中,复活2次培养至对数生长期后刮取菌落,置于细菌稀释液中,制备0.5麦氏浓度的细菌悬液原液,原液稀释10倍用于PDT实验.分别用1、2、3 mW/cm2紫外线A（UVA）对不同质量分数核黄素作用后的细菌照射10、20、30 min,测量不同条件下抑菌圈直径的大小,确定最佳抑菌条件.将金黄色葡萄球菌、表皮葡萄球菌和铜绿假单胞菌分别分为正常对照组、单独核黄素作用组、单独紫外线照射组和PDT组,比较不同组间各种细菌菌落数的差异. 结果 当UVA强度为3 mW/cm2、作用30 min、核黄素质量分数为0.1％时,MH固体培养皿上抑菌圈直径接近6 mm,故上述参数为PDT法抑菌的最佳条件.正常对照组、单独核黄素作用组、单独紫外线照射组和PDT组的金黄色葡萄球菌、表皮葡萄球菌和铜绿假单胞菌的菌落数依次减少,差异均有统计学意义（F=110.990、190.841、118.197,均P=0.000）,单独紫外线照射组各种细菌的菌落数均明显少于正常对照组,差异均有统计学意义（t=14.640、7.550、5.320,P＜0.05）,PDT组各种细菌的菌落数亦明显少于正常对照组的菌落数,差异均有统计学意义（t=25.480、14.750、12.920,P＜0.05）.单独紫外线照射组细菌量较正常对照组降低46.4％～50.2％,PDT组的细菌量降低91.6％ ～96.7％,而单独核黄素作用组的细菌菌落数与正常对照组相比差异均无统计学意义（t=0.660、0.470、0.510,P＞0.05）.结论 在紫外线-核黄素PDT灭活微生物的最佳体外实验条件下,PDT法对金黄色葡萄球菌、表皮葡萄球菌和铜绿假单胞菌的杀菌效果最好.