Methicillin‐resistant Staphylococcus aureus keratitis in a dog

The purpose of this study is to report a case of methicillin‐resistant Staphylococcus aureus (MRSA) keratitis in a dog. A 7‐year‐old intact male American cocker spaniel that had undergone removal of a nictitating gland was referred for severe ulcerative keratitis. Slit‐lamp examination showed swelling of the eyelid, mucopurulent discharge, conjunctival injection and chemosis, diffuse corneal edema and opacity, and a deep ulcer in central cornea. Gram staining of discharge from the eye demonstrated Gram‐positive cocci. Despite topical ofloxacin, oxytetracycline and polymyxin B ophthalmic solution and intravenous cefazolin, there was no improvement. Cultures revealed MRSA that was sensitive only to chloramphenicol, vancomycin, lincomycin, and clindamycin. The antibiotic regimen was changed to topical and systemic chloramphenicol. After 9 days of treatment, although inflammation started to be resolved, the dog developed nonregenerative anemia. The antimicrobial regimen was changed again to topical and systemic vancomycin. Inflammation continued to improve over the next week. MRSA should be considered a potential organism in infectious keratitis, especially when general antibiotics are not effective. Although topical and systemic chloramphenicol and/or vancomycin are effective for treating MRSA keratitis, vancomycin should only be used when culture and susceptibility results indicate it is appropriate and no other options are available. To our knowledge, this is the first detailed case report of MRSA keratitis in a dog.     

Methicillin‐resistant Staphylococcus aureus in Resident Animals of a Long‐term Care Facility

Animals provide benefits to elderly and chronically ill people by decreasing loneliness, increasing social interactions, and improving mental health. As a result, many hospitals and long‐term care facilities allow family pets to visit ill or convalescing patients or support animal‐assisted therapy programs. These include programs that have resident animals in long‐term care facilities. Despite the benefits, there are concerns about disease transmission between pets and patients. Antibiotic‐resistant bacteria, such as methicillin‐resistant Staphylococcus aureus (MRSA), are a recognized problem in healthcare settings leading to refractory infections and potentially life‐threatening illnesses. MRSA has been isolated from numerous animal species, yet few studies are available on the carriage of this pathogen in animals residing in long‐term care facilities. Our objective was to characterize MRSA carriage among resident animals in a long‐term care facility. Methods: To document MRSA colonization, nasal swabs from 12 resident animals (one dogs and 11 cats) of a long‐term care facility were collected weekly for 8 weeks. Staphylococcus isolates were characterized by antimicrobial susceptibility and MRSA isolates were further characterized by pulsed‐field gel electrophoresis (PFGE). PFGE isolate patterns were compared with an existing database of MRSA isolate patterns at the Minnesota Department of Health. Results: Two of 11 cats were colonized with MRSA. MRSA was recovered from five of eight weekly samples in one cat and two of eight weekly samples in the other cat. All isolates were classified as USA100 (healthcare‐associated strains). Discussion: Long‐term care resident animals may acquire MRSA. Clonally related strains were identified over the 8‐week sampling period. It is unclear if pets serve as an on‐going source of infection to their human companions in long‐term care facilities.     

金黄色葡萄球菌感染小鼠乳房炎模型的建立

取25只分娩8～10d的昆明系小鼠随机分成5组(n=5),分别为阴性对照、生理盐水(pss)组和不同剂量金黄色葡萄球菌(1.0×102cfu/50μL、1.0×103cfu/50μL、5.0×103cfu/50μL)试验组,经乳头导管对第4对乳腺50μL/只注射,24h后观察结果,一侧乳腺甲醛固定制作切片观察组织病理变化,另一侧冰上研磨后取匀浆用高盐甘露醇鉴别培养基进行细菌计数,检测组织匀浆上清中的TNF-α含量。结果显示,试验组随着注射细菌数量的增加,病理变化加重,分离到的金黄色葡萄球菌数量显著增加,乳腺匀浆中TNF-α含量明显升高。结果表明,注射1.0×103cfu组可以引起较典型的小鼠乳房炎,且病理变化适中,适合用来建立金黄色葡萄球菌小鼠乳房炎模型。     

金黄色葡萄球菌诱导大鼠乳腺炎模型的建立

妊娠Wistar大鼠84只,随机分为试验组和对照组(n=42)。产后第4天,试验组经第4对乳腺的乳导管灌注金黄色葡萄球菌0.1 m L(2×107CFU/m L),对照组注射同量的生理盐水。动态观察和记录大鼠的临床症状、病理组织学变化、胸腺和脾脏指数、乳腺组织内细菌数和血液学变化。结果显示,注菌后,试验组胸腺和脾脏指数显著或极显著升高(P0.05或P0.01);乳腺组织内细菌量在接种后6 h迅速升高,之后开始下降,直至96 h,乳腺组织仍可以检测到金黄色葡萄球菌,高于300 CFU/mg乳腺组织;外周血中的嗜中性粒细胞在接种后6 h,12 h,极显著升高(P0.01),之后差异不显著;病理组织学检查显示,接种细菌后可导致明显的炎症反应。表明本研究建立了经乳腺导管灌注金黄色葡萄球菌诱发大鼠乳腺炎的动物模型。     

Brain microabscesses in a porcine model of Staphylococcus aureus sepsis

Background

Sepsis caused by Staphylococcus aureus often leads to brain microabscesses in humans. Animal models of haematogenous brain abscesses would be useful to study this condition in detail. Recently, we developed a model of S. aureus sepsis in pigs and here we report that brain microabscesses develop in pigs with such induced S. aureus sepsis.Twelve pigs were divided into three groups. Nine pigs received an intravenous inoculation of S. aureus once at time 0 h (group 1) or twice at time 0 h and 12 h (groups 2 and 3). In each group the fourth pig served as control. The pigs were euthanized at time 12 h (Group 1), 24 h (Group 2) and 48 h (Group 3) after the first inoculation. The brains were collected and examined histopathologically.

Results

All inoculated pigs developed sepsis and seven out of nine pigs developed brain microabscesses. The microabscesses contained S. aureus and were located in the prosencephalon and mesencephalon. Chorioditis and meningitis occurred from 12 h after inoculation.

Conclusions

Pigs with experimental S. aureus sepsis often develop brain microabscesses. The porcine brain pathology mirrors the findings in human sepsis patients. We therefore suggest the pig as a useful animal model of the development of brain microabscesses caused by S. aureus sepsis.     

Longitudinal Investigation of Methicillin‐Resistant Staphylococcus aureus in Piglets

Methicillin‐resistant Staphylococcus aureus (MRSA) has emerged as an important public health concern and pigs have been implicated in human infections. Cross‐sectional studies have demonstrated that MRSA can be commonly found in pigs internationally, but little is known about age‐related changes in MRSA colonization. This study evaluated MRSA colonization in piglets in a longitudinal manner. Serial nasal swabs were collected from piglets born to 10 healthy sows. The prevalence of MRSA colonization on days 1, 3, 7, 14 and 21 was 1% (1/100), 6.2% (3/97), 8.5% (8/94), 4.4% (4/91) and 20% (18/91) respectively, with an overall pre‐weaning prevalence of 34.5%. The prevalence on days 28, 42, 56 and 70 was 34% (31/91), 65% (57/88), 50% (44/88) and 42% (36/87) respectively, with an overall post‐weaning prevalence of 85%. Eighty‐four percent of piglets from negative sows and 100% of piglets from positive sows that survived at least until the time of weaning were colonized with MRSA at one or more times during the study. There was a significant association between sow and piglet colonization. The age of the piglet was significantly associated with the probability of colonization. No piglets or sows received antimicrobials during the study period. These results indicate that age must be considered when designing surveillance programmes and interpreting results of different studies on MRSA.     

鼠金黄色葡萄球菌的分离与鉴定

20 0 1年 9月 ,从江苏省某动物房感染发病的实验小鼠中分离到 1株金黄色葡萄球菌并进行了鉴定。该菌能产生金黄色色素 ,发生 β 溶血反应 ,发酵部分糖和甘露醇 ,凝固酶试验为阳性     

Colonization of Butchers with Livestock‐Associated Methicillin‐Resistant Staphylococcus aureus

Reports have documented colonization of swine in Europe, North America and more recently in China with livestock‐associated methicillin‐resistant Staphylococcus aureus (LA‐MRSA). Contamination of pig farmers, veterinarians and abattoir workers with these strains has been observed. However, although contamination levels of 10% of retail pork were reported from the Netherlands and Canada, there are limited data of contamination rates of workers handling raw meat. We investigated the rates of MRSA contamination of local butchers working in wet markets, where recently slaughtered pigs are cut up. Nasal swabs collected from 300 pork butchers at markets throughout Hong Kong were enriched in brain heart infusion broth with 5% salt and cultured on MRSASelect^®. Isolates were confirmed as Staphylococcus aureus and susceptibility testing performed. The presence of mecA was confirmed, SCCmec and spa type determined and relatedness investigated by PFGE. Subjects completed a questionnaire on MRSA carriage risk factors. Seventeen samples (5.6%) yielded MRSA, 15 harbouring SCCmec IVb. Ten strains were t899 (CC9), previously reported from local pig carcasses. Five strains were healthcare associated: SCCmec type II, t701(CC6), colonizing two subjects at the same establishment, and single isolates of t008 (CC8), t002 (CC5) and t123 (CC45). The remaining isolates were t359 (CC97), previously reported from buffaloes, and t375 (CC5), reported from bovine milk. None of these butchers reported recent hospitalization or a healthcare worker in the family. Two had recently received antibiotics, one for a skin infection. Four reported wound infections within the last year. All were exposed to meat for >9 h per day. Carriage of MRSA was higher in butchers than in the general community. Although five strains were probably of healthcare origin, the high incidence of t899 (CC9) suggests that cross‐contamination from pork occurs frequently. Washing of hands after touching raw pork is advised.     

Methicillin‐Resistant Staphylococcus aureus Colonization in Personnel Attending a Veterinary Surgery Conference

Objective— To evaluate the prevalence of, and risk factors for, methicillin‐resistant Staphylococcus aureus (MRSA) colonization in veterinary personnel. Study Design— Cross‐sectional study. Sample Population— Conference attendees (n=341) at the 2008 American College of Veterinary Surgeons Symposium in San Diego California. Methods— Nasal swabs were collected and tested using selective culture for MRSA. Isolates were typed and risk factors were evaluated using questionnaire data. Results— 17.3% of subjects (17% veterinarians and 18% technicians) were MRSA positive. Colonized individuals originated from 5 different countries, predominantly the United States and Canada. Contact with small ruminants in the preceding 30 days (odds ratio [OR] 2.2), living with a person diagnosed with MRSA in the preceding year (OR 19.8) and working in a clinic where there is a specific person in charge of the infection control program (OR 2.2) were associated with colonization using multivariable analysis. Conclusion— The high rate of colonization identified here provides more evidence that MRSA exposure is likely an occupational risk for veterinary personnel. The equal rates in small animal and large animal personnel were surprising and contradict earlier studies indicating greater rates among equine personnel. The association of MRSA and small ruminant contact has not been reported previously. Clinical Relevance— MRSA is an important emerging pathogen in veterinary medicine and is a concern for both patients and veterinary personnel. The high colonization rate indicates the need to understand and control the spread of MRSA in veterinary clinics.     

Staphylococcus aureus vaccine against mastitis in dairy cows,composition and evaluation of its immunogenicity in a mouse model

Bovine mastitis caused by Staphylococcus aureus (S. aureus) is a most important infection disease that affects both the quality and the quantity of milk production. Antibiotic therapies formulated for intramammary use are generally unsuccessful in eliminating existing S. aureus infections. Vaccination is a logical approach to the control of S. aureus udder infections. However, to date commercially available S. aureus vaccine have shown limited efficacy under field conditions, mainly due to the paucity of information regarding relevant antigens which will induce a broad spectrum immunization. In the present paper the attempt to develop a new vaccine designated MASTIVAC I is described. MASTIVAC I is composed of three strains of S. aureus namely: VLVL8407; ZO3984 and BS449 which were isolated from clinical and sub-clinical cases of bovine mastitis. A mouse model was used to evaluate the S. aureus specific antibody production and protection of mice against virulent S. aureus strains. The results obtained showed that this vaccine exhibits a broad spectrum of antigenic and immunogenic properties that protects mice from homologues and hetrologous S. aureus challenge.     

The invasiveness of Staphylococcus aureus and Staphylococcus epidermidis for the mammary gland of the mouse

The invasiveness of Staphylococcus aureus and Staphylococcus epidermidis for the mammary gland of the mouse was assessed by contaminating the damaged teats of suckling mice and sampling the mammary glands for the contaminating organism 48 hours later. Using this test system Staphylococcus aureus strain BB invaded 17 of 40 glands (42.5 %) and Staphylococcus epidermidis strain 279 invaded 2 of 40 glands (5.0 %). The histopathological changes in glands infected with Staphylococcus aureus were more severe than in those infected with Staphylococcus epidermidis.     

Phagocytosis and killing of Staphylococcus aureus by bovine neutrophils after priming by tumor necrosis factor-alpha and the des-arginine derivative of C5a

OBJECTIVES: To evaluate effects of proinflammatory mediators on phagocytosis and killing of Staphylococcus aureus, the oxidative burst (OB), and expression of receptors for opsonins by bovine neutrophils. SAMPLE POPULATION: Neutrophils from 10 cattle. PROCEDURE: Neutrophils were primed with recombinant bovine tumor necrosis factor-alpha (TNF-alpha) or the des-arginine derivative of bovine C5a (C5a(desArg)) and mixed with S aureus. Phagocytosis and OB were measured by use of flow cytometry. Rate of phagocytosis and intracellular killing were evaluated. Expression of receptors for immunoglobulins and the C3bi fragment of complement were estimated by use of flow cytometry. RESULTS: Priming of neutrophils by TNF-alpha improved phagocytosis of S aureus with a concentration-dependent effect. Phagocytosis of preopsonized washed bacteria was increased by activation of neutrophils with C5a(desArg). Phagocytosis was optimal when neutrophils primed with TNF-alpha were activated with C5a(desArg). The OB of phagocytizing neutrophils was highest when TNF-alpha and C5a(desArg) were used in combination. Bactericidal activity of neutrophils was stimulated by priming with TNF-alpha or C5a(desArg). Binding of bovine IgM or IgG2 to bovine neutrophils was not stimulated byTNF-alpha, C5a(desArg), or both, and aggregated IgG1 did not bind to neutrophils regardless of their activation state. Both TNF-alpha and C5a(desArg) increased expression of beta2 integrins (CD18), with the highest expression when they were used in combination. CONCLUSIONS AND CLINICAL RELEVANCE: The mediators TNF-alpha and C5a(desArg) stimulated phagocytic killing by neutrophils and potentiated each other when used at suboptimal concentrations. Bovine neutrophils have enhanced bactericidal activities at inflammatory sites when TNF-alpha, C5a(desArg), or both are produced locally.     

Molecular characterization of community‐associated methicillin‐resistant Staphylococcus aureus from pet dogs

Community‐associated methicillin‐resistant Staphylococcus aureus (MRSA) is a serious public health concern and in Australia, one that disproportionately affects Aboriginal people. Paralleling MRSA in human medicine, methicillin‐resistant S. pseudintermedius (MRSP) is an increasingly prevalent pathogen in veterinary medicine. We aimed to characterize the carriage of MRSA and MRSP in dogs and cats from predominantly Aboriginal communities in a very remote region of New South Wales (NSW), Australia. Pets (303 dogs and 80 cats) were recruited from six communities in western NSW. Three swabs were collected from each animal (anterior nares, oropharynx and perineum) and from skin lesions or wounds (if present) and cultured on selective media for methicillin‐resistant staphylococci. Human host‐adapted community‐associated MRSA representing four multilocus sequence types (ST1‐IV, ST5‐IV, ST72‐IV, ST93‐IV) were isolated from eight dogs (prevalence 2.6%, 95% confidence interval 1.3%–5.1%). Two ST5‐IV isolates from a single dog were phenotypically trimethoprim‐resistant, harbouring trimethoprim‐resistant gene dfrG within the SCCmec type IVo mobile genetic element. MRSA was not isolated from any cats and MRSP was not isolated from any dogs or cats. This study estimated a high prevalence of human host‐adapted community‐associated MRSA carriage in dogs despite an absence of MRSP. This suggests MRSA carried by dogs in remote NSW originate from human hosts. The cycle of transmission between people, dogs and common environmental sources warrants further investigation. To our knowledge, this is the first report of trimethoprim‐resistant ST5‐IV in eastern Australia and the first report of trimethoprim‐resistant ST5‐IV from a dog.     

Effects of lysostaphin on Staphylococcus aureus infections of the mouse mammary gland

A 5 to 6 log10 reduction in the viable count of Staphylococcus aureus was produced in vitro with 10 micrograms lysostaphin ml-1 milk. Infusion of the lactating murine mammary gland with 10 micrograms lysostaphin, immediately following inoculation with 10(8) colony forming units of S aureus, resulted in a significant 2 to 3 log10 reduction in viable S aureus (P less than 0.02) within 30 minutes. Pre-infusion with 10 micrograms lysostaphin either immediately before or one hour before staphylococcal challenge reduced the recovery of S aureus by more than 6 log10 and greatly reduced pathological changes typical of S aureus mastitis. This clearly demonstrates that lysostaphin has considerable potential for the therapeutic or prophylactic control of staphylococcal mastitis.     

High and low virulence Staphylococcus aureus strains in a rabbit skin infection model

In the present study, an in vivo rabbit skin infection model was developed to reproduce the lesions caused by high and low virulence Staphylococcus aureus strains from rabbits. "O"-shaped dermal skin lesions were induced on the shaved flanks of anaesthetised rabbits using a tattoo pin and pincers. The induced lesions on the flanks of four groups of 10 rabbits were then inoculated by topical application of 0.1 ml of 10(8)cfu S. aureus bacteria. One group was inoculated with a typical high virulence (HV) S. aureus strain from rabbits, one group received an atypical HV strain and two groups were inoculated with low virulence (LV) strains. Five animals were kept as negative controls. The development, appearance and size of abscesses were scored daily for a period of 2 weeks. The infection model showed reproducible results for the different S. aureus inoculation groups. Inoculation of the skin with the typical HV strain resulted in significantly larger abscesses than those caused by the LV strains. The atypical HV strain caused abscesses of a size intermediate to that obtained with the HV and LV strains. In rabbits infected with LV strains, most of the lesions had healed by day 14 post-inoculation. The devised infection model is able to reliably reproduce the virulence properties of HV and LV S. aureus strains.     

Vesicular Lesions Produced in Guinea Pigs by a Staphylococcus aureus Strain

A bacterium isolated from vesicular lesions on foot pads of guinea pigs reproduced lesions similar to those seen in experimental infections of guinea pigs with foot-and-mouth disease virus. (FMDV). These bacterial lesions were produced with an inactivated FMDV suspension. Identification as Staphylococcus aureus was determined by growth characteristics on nutrient and blood agar, Gram staining, fermentation of mannitol and coagulase positive reactions. In addition, the organism was sensitive to concentrations of penicillin and streptomycin commonly used in laboratory diluents.