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Methicillin-resistant Staphylococcus aureus infection was identified in 11 dogs. The infection was associated with surgical treatment especially orthopaedic surgery. Infection after traumatic wounding, and recurrent pyoderma was also seen. Oral antibiotic treatment improved or resolved the infection in nine of the 11 dogs, although the methicillin-resistant isolates were susceptible to relatively few antibiotics.
The progress of Staphylococcus aureus infection from inoculation to the early chronic stage was examined in 12 Israeli-Holstein cows (four primiparous and eight multiparous) for up to 48 d after inoculation. Before inoculation, the primiparous cows were free from any infection and the multiparous cows were infected by coagulase-negative staphylococci. Two quarters in each cow were inoculated intracisternally following milking with 2000 cfu of a local prevailing Staph. aureus strain, VL-8407. Infection was established in 21 out of 24 quarters. The control quarters remained free from infection during the study, with no significant change in function. No statistically significant differences were found between primiparous and multiparous cows in the responses examined. Somatic cell count (SCC) increased within 24 h of inoculation and remained high for the duration of the study. In the infected quarters mean ln (SCC) increased within 24 h from 9.9 +/- 0.5 before inoculation to 13.0 +/- 0.2 after inoculation; most of the cells were neutrophils. N-acetyl-beta-glucosaminidase activity, expressed as ln (nnmol/min per l), was increased from 0.9 +/- 0.6 to 2.4 +/- 0.2 by inoculation, and was highly correlated with SCC. The Staph. aureus count fluctuated with no particular relationship with SCC. The phagocytic activity of neutrophils was significantly lower in the inoculated than in the control quarters and this difference increased with time after inoculation. CD8+ T lymphocytes were the main subpopulation of lymphocytes found in inoculated quarters. After inoculation, maximum but not minimum electrical conductivity (EC) recorded during milking increased significantly. The rises in maximum EC varied significantly among cows. The rises in SCC were associated with a persistent increase in EC in only one of the eight cows examined. No clinical signs were observed, and milk yield and composition were not affected during the study period. The results suggest that some strains of Staph. aureus may induce a relatively mild response in mammary glands of cows in mid lactation, and that the concomitant development of such chronic Staph. aureus infections in two quarters may not be detected by changes in the EC of composite milk and in the yield of the cow.
INTRODUCTION: Staphylococcus lugdunensis is a coagulase-negative staphylococcus associated with infections such as aggressive endocarditis, repeated abscess formation and opportunist infections. MATERIALS AND METHODS: S. lugdunensis isolates recovered at our hospital during three years (1997-2000) were studied. The fibrinogen affinity factor and tube free-coagulase were analysed. The identification was made by the Crystal GPID (Becton-Dickinson) and Wider (Soria Melguizo) systems. Antibiotic sensitivity testing was performed with Wider panels. The clinical records of patients with S. lugdunensis recovered were studied. RESULTS: Thirteen S. Lugdunensis isolates were recovered from the following sources: abscess (9), surgical wound (2), blood culture (1), and urine (1). In ten cases the microorganism was obtained in pure culture; in the remaining three cases, S. lugdunensis grew in mixed culture. Two cases were excluded, as S. lugdunensis was considered not to be associated with the clinical condition. Lesions were located at: inguinal region (4), gluteal region (2), breast (2), abdominal wall (1), foot (1), unknown (1). Tent of the 13 isolates (76%) had fibrinogen affinity factor. Penicillin sensitivity was observed in 11/13 strains (84.6%). In one case, the isolate was beta-lactamase producer (7.6%); and in other case, the isolate was resistant to methicillin (7.6%). CONCLUSIONS: In this study we observed that S. lugdunensis is associated with skin and soft tisue infections, particularly abscess formation. The infection occurs most frequently in cancer patients, as observed in three cases in our series. The necessity of correctly identifying S. Lugdunensis is underscored. The recovery of coagulase-negative staphylococci should not reassure us unless a potentially pathogen species has been ruled out.
Methicillin-resistant Staphylococcus aureus (MRSA) infections are an emerging problem in both children and adults throughout the United States. Skin and soft tissue infections are most common, however serious invasive disease can occur and may involve any anatomic site. The initial empiric therapy of suspected S. aureus infections will be influenced by the regional antimicrobial susceptibility patterns for the organism as well as the severity of the infection being treated. This article will review the epidemiology, clinical features, and treatment considerations for MRSA infections in children.
Staphylococcus aureus is a major cause of surgical wound infections. The development of mechanisms of antimicrobial resistance by this and other bacterial pathogens has prompted the search for new approaches to treat infectious diseases. Hyaluronic acid binding peptides have been shown to modulate cellular trafficking during host responses and were assessed for their ability to treat and possibly prevent experimental surgical wound infections caused by S. aureus. Treatment with these peptides was highly efficacious in reducing the number of S. aureus cells at the wound site and ameliorated the inflammatory host response associated with these infections. These data suggest a novel approach for the treatment and prophylaxis of staphylococcal wound infections in the clinical setting.
Staphylococcus aureus is the leading cause of bacterial infection in liver transplant recipients. Preoperative nasal carriage of methicillin-resistant S. aureus (MRSA) is associated with a high risk of infection. We conducted a retrospective cohort study in order to identify independent risk factors for early-onset S. aureus infection after liver transplantation. Patients were screened preoperatively for methicillin-susceptible S. aureus (MSSA) and MRSA nasal carriage. Risk factor analysis was performed by univariate analysis followed by stepwise logistic regression. Of the 323 patients included, 63 (19.5%) patients developed S. aureus infection (36 MRSA, 27 MSSA) within 1 month of surgery. Variables significantly associated with infection in the univariate analysis were MRSA and MSSA nasal carriage, alcoholic cirrhosis, absence of hepatocellular carcinoma, decreased prothrombin ratio, and presence of ascites. In the multivariate analysis, MRSA carriage (odds ratio [OR]: 20.9, P < 0.0001), MSSA carriage (OR: 3.4, P = 0.0004), alcoholic cirrhosis (OR: 2.4, P = 0.01) and decreased prothrombin ratio (OR: 1.2, P = 0.01) were independent predictors of infection. Molecular typing showed that the infecting isolate was identical to the isolate from the nose in most patients. In conclusion, preoperative nasal carriage of MRSA and MSSA is an independent risk factor for S. aureus infection in liver transplant recipients. The infection is most often of endogenous origin. Alcoholic cirrhosis and the severity of liver failure are also associated with a high risk of infection.
Dairy herds (n = 76) with an initial prevalence of Staphylococcus aureus IMI > or = 10% were included in this study. Criteria were that herds did not change teat dipping or dry cow treatment practices, did not segregate cows that were positive for S. aureus at the initial visit, and did not cull > 50% of cows found to be positive on the initial visit. During a follow-up period (6 to 24 mo), segregation or separate milking of cows that were positive for S. aureus reduced prevalence from 29.5 to 16.3% and bulk tank SCC from 600,000 to 345,000/ml. Prevalence of S. aureus mastitis was unchanged for herds that did not segregate cows with S. aureus, 22.5 to 20.2%, and the reduction in SCC from 698,000 to 484,000 for nonsegregated herds was also smaller. Segregation of cows that were known to be positive for S. aureus is an effective mastitis control practice.
BACKGROUND: Coagulase-negative Staphylococcus epidermidis has become a major frequent cause of infections in relation to the use of implanted medical devices. The pathogenicity of S. epidermidis has been attributed to its capacity to form biofilms on surfaces of medical devices, which greatly increases its resistance to many conventional antibiotics and often results in chronic infection. It has an urgent need to design novel antibiotics against staphylococci infections, especially those can kill cells embedded in biofilm. RESULTS: In this report, a series of novel inhibitors of the histidine kinase (HK) YycG protein of S. epidermidis were discovered first using structure-based virtual screening (SBVS) from a small molecular lead-compound library, followed by experimental validation. Of the 76 candidates derived by SBVS targeting of the homolog model of the YycG HATPase_c domain of S. epidermidis, seven compounds displayed significant activity in inhibiting S. epidermidis growth. Furthermore, five of them displayed bactericidal effects on both planktonic and biofilm cells of S. epidermidis. Except for one, the compounds were found to bind to the YycG protein and to inhibit its auto-phosphorylation in vitro, indicating that they are potential inhibitors of the YycG/YycF two-component system (TCS), which is essential in S. epidermidis. Importantly, all these compounds did not affect the stability of mammalian cells nor hemolytic activities at the concentrations used in our study. CONCLUSION: These novel inhibitors of YycG histidine kinase thus are of potential value as leads for developing new antibiotics against infecting staphylococci. The structure-based virtual screening (SBVS) technology can be widely used in screening potential inhibitors of other bacterial TCSs, since it is more rapid and efficacious than traditional screening technology.
BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen that causes severe morbidity and mortality in many hospitals worldwide, and MRSA infections are frequent in intensive care units (ICUs). OBJECTIVE: A prospective study was implemented to investigate the risk factors for ICU-acquired MRSA infections. METHODS: This study was conducted in surgical and neurologic ICUs from May to November 2003. The patients staying in ICUs more than 48 hours were included in the study. All of the patients were visited daily, and data were recorded on individual forms for each patient until discharge or death. Nasal swab cultures were done within 48 hours of ICU admission and repeated every week until the patients colonized with MRSA or were discharged from ICUs. ICU-acquired MRSA infection was diagnosed when MRSA was isolated from the infected site. RESULTS: Overall, 249 patients were followed during the study. MRSA infection was detected in 21 (8.4%) of these patients. The most frequent infection was primary bloodstream infection (10/21, 47%). It was followed by pneumonia (8/21, 38%) and surgical site infection (3/21, 14%). Nasal MRSA colonization was detected in 59 (23.7%) patients, and 12 of them (20.3%) developed MRSA infection. In univariate analysis, hospitalization period in an ICU, intraabdominal and orthopedic pathologies, mechanical ventilation, central venous catheter insertion, total parenteral nutrition, previous antibiotic use, surgical ICU stay, nasal MRSA colonization, and presence of more than 2 patients having nasal colonization in the same ICU at the same time were found significant for MRSA infections. In multivariate analysis; hospitalization period in an ICU (OR, 1.090; 95% CI: 1.038-1.144, P = .001), central venous catheter insertion (OR, 1.822; 95% CI: 1.095-3.033, P = .021), previous antibiotic use (OR, 2.337; 95% CI: 1.326-4.119, P = .003) and presence of more than 2 patients having nasal colonization in the same ICU at the same time (OR, 1.398; 95% CI: 1.020-1.917, P = .037) were independently associated with MRSA infections. CONCLUSION: According to the our results, hospitalization period in an ICU, presence of patients colonized with MRSA in the same ICU at the same time, previous antibiotic use, and central venous catheter insertion are independent risk factors for ICU-acquired MRSA infections. Detection of these factors helps to decrease the rate of MRSA infections in the ICUs.
The opportunistic human pathogen Staphylococcus epidermidis has become the most important cause of nosocomial infections in recent years. Its pathogenicity is mainly due to the ability to form biofilms on indwelling medical devices. In a biofilm, S. epidermidis is protected against attacks from the immune system and against antibiotic treatment, making S. epidermidis infections difficult to eradicate.
PURPOSE OF REVIEW: Staphylococcus aureus produces two closely-related fibronectin-binding proteins (FnBPs) that facilitate attachment by this versatile pathogen. Recent studies of staphylococcal FnBP have increased our understanding of the molecular mechanisms that are critical in bacterial-host cell interactions and in infection. RECENT FINDINGS: This review will summarize current knowledge of the role of the FnBPs of Staphylococcus aureus in the pathogenesis of infection. The FnBPs, which facilitate attachment of this pathogen to host cells and to fibronectin-coated biomaterials, are important mediators of infection in experimental endocarditis. In addition, recent vaccine studies utilizing FnBP derivatives have shown partial protection in animals. FnBPs also act as invasins permitting uptake of the staphylococcus by cultured non-professional phagocytes using host fibronectin to bridge with integrins on the cell surface. However, the precise role of FnBP in tissue invasion and the relevance of intracellular invasion in disease remain to be elucidated. SUMMARY: FnBP is one of many adhesins expressed by S. aureus that influence host tissue adherence by binding to host fibronectin. FnBP-based vaccine strategies and novel anti-adherence tools based upon FnBP derivatives are in the early stages of investigation but may show promise in preventing staphylococcal infections.
Survival of Staphylococcus epidermidis inside macrophages has been recognized as a pivotal process in the pathogenesis of biomaterial-associated infection (BAI). Interferon (IFN)-gamma is a potent activator of macrophages. This study examined whether subcutaneous injections of IFN-gamma can reverse macrophage deactivation induced by implanted biomaterials. Mice received subcutaneous implants combined with an injection of 106 S. epidermidis to induce an experimental BAI. Subsequently, 3 groups of mice received subcutaneous injections of 25,000 IU IFN-gamma 3 times weekly, 10,000 IU IFN-gamma 3 times in 2 weeks, or saline 3 times weekly (saline control), respectively. A fourth group received no injections (control). Segments and tissues of the IFN-gamma-treated mice were significantly less (P<.05) culture positive than those of the control groups. Histologically, the high numbers of intracellularly persisting gram-positive cocci observed in the control mice were absent in the IFN-gamma-treated mice. These data indicate that IFN-gamma protects against experimental BAI.
Staphylococcus aureus is a leading cause of serious hospital- and community-acquired infections. The discovery of serologically distinct capsular polysaccharides on the surface of clinical isolates has allowed the development of vaccines and passive protective immunity. We have studied patient characteristics, infection characteristics and the surface and capsular polysaccharide serotype distribution in patients with S. aureus infections complicated by bacteraemia admitted to VA hospitals in Maryland between 1995 and 2000. Nine hundred and ninety-three blood cultures from 331 patients were positive for S. aureus. Thirty-eight percent of patients had diabetes, 11% had end-stage renal failure, and 23% were injection drug users. Forty-two percent of infections were caused by methicillin-resistant strains (MRSA), and 60% were acquired during hospitalization. Serotyping of the first available isolate per patient (N=234 isolates) using polyclonal antibodies showed three major phenotypes--42%, type 8 (T8) capsule; 50%, type 5 (T5) capsule; and 8%, 336 polysaccharide. MRSA isolates were significantly more likely to be T5 than methicillin-susceptible isolates (66% vs. 39%, P<0.001). The proportion of T5 MRSA increased significantly (years 1-2: 41%; years 3-4: 65%; years 5-6: 90%, P<0.001). This large sample of patients with serious S. aureus infection confirms that capsular polysaccharides T5 and T8 cause most human infections, and together with serotype 336, account for nearly all those with bacteraemia.
Infection due to Staphylococcus aureus continues to be a source of significant morbidity and mortality. However, its treatment is increasingly complicated by the rising prevalence of resistance to antibiotics. Apart from the two recognized modes of staphylococcal resistance, namely, penicillinase production and intrinsic resistance, Sabath and associates have described a third type in which resistance is manifested by susceptibility to growth inhibition but tolerance to the lethal action of bactericidal agents. The mechanism of tolerance is attributed to a deficiency of autolytic enzyme activity in the part of bacteria, possibly secondary to an inhibition of autolysins in the tolerant staphylococcal strains. These strains are found in patients with infections responding poorly to treatment with cell-wall active antibiotics including vancomycin. Because of its unique mechanism of action and pharmacokinetic properties, rifampin has been reported to be the most active among 65 antistaphylococcal agents tested and have the capacity to kill intraleukocytic staphylococci. We present 2 cases who were cured following the addition of rifampin to previously established regimens. Case 1 was a 40-year-old male who had fever, cough, dyspnea, a right elbow abscess and left leg swelling for 2 weeks prior to admission. Culture of purulent material from the elbow abscess grew staphylococcus aureus. Chest X-ray showed bilateral septic embolism and phleborheography showed partial deep vein occlusion of the left ileofemoral vein. Case 2 was 22-year-old female with fever, chills and cough for 3 weeks. Blood culture grew staphylococcus aureus, and Chest X-ray revealed bilateral septic embolism with pneumonia. Neither of them responded to standard antibiotics which were judged adequate by in vitro sensitivity tests. Clinical cure was later obtained after rifampin was added to the regimens. These results suggest that rifampin may be a useful adjunct in the therapy of staphylococcal infections.
The destructive course of Staphylococcus aureus arthritis is due to certain leukocytes and their products, mainly cytokines. The cellular source of cytokines mediating this inflammatory process has not been previously assessed on a protein level. Using a mouse model of hematogenously induced S. aureus infection the intracellular production of IFN-gamma, IL-4 and IL-10 in splenic B and T cells have been determined. This has enabled us to define distinct Th1 vs Th2 and Be1 vs Be2 populations of lymphocytes participating in S. aureus infection. Spleen cells were obtained before, and at different time intervals during the first week of infection and re-stimulated in vitro with staphylococcal peptidoglycan, formalin killed staphylococci and TSST-1. The different antigens used for re-stimulation gave rise to different cytokine profiles in analysed T cells (identified as CD4+) and B cells (identified as CD19+). TSST-1 acted as the most potent re-stimulator and we found that 40% of the CD4+ cells responded with IFN-gamma production, and unexpectedly almost 20% of the CD19+ cells. As to IL-4 and IL-10 production, the percentage of B cells expressing these cytokines was higher than the percentage T cells and the peak of their appearance appeared later than that of IFN-gamma. This finding indicates that Be1 cells are an important source of IFN-gamma early during the infection and that the production of the Th2 cytokines in B cells downregulates its production of IFN-gamma. In conclusion this study shows that both B and T cells contribute to the cytokine production during S. aureus infection in a complex pattern.
CONTEXT: Methicillin-resistant Staphylococcus aureus (MRSA) has traditionally been considered a health care-associated pathogen in patients with established risk factors. However, MRSA has emerged in patients without established risk factors (community-associated MRSA). OBJECTIVE: To characterize epidemiological and microbiological characteristics of community-associated MRSA cases compared with health care-associated MRSA cases. DESIGN, SETTING, AND PATIENTS: Prospective cohort study of patients with MRSA infection identified at 12 Minnesota laboratory facilities from January 1 through December 31, 2000, comparing community-associated (median age, 23 years) with health care-associated (median age, 68 years) MRSA cases. MAIN OUTCOME MEASURES: Clinical infections associated with either community-associated or health care-associated MRSA, microbiological characteristics of the MRSA isolates including susceptibility testing, pulsed-field gel electrophoresis, and staphylococcal exotoxin gene testing. RESULTS: Of 1100 MRSA infections, 131 (12%) were community-associated and 937 (85%) were health care-associated; 32 (3%) could not be classified due to lack of information. Skin and soft tissue infections were more common among community-associated cases (75%) than among health care-associated cases (37%) (odds ratio [OR], 4.25; 95% confidence interval [CI], 2.97-5.90). Although community-associated MRSA isolates were more likely to be susceptible to 4 antimicrobial classes (adjusted OR, 2.44; 95% CI, 1.35-3.86), most community-associated infections were initially treated with antimicrobials to which the isolate was nonsusceptible. Community-associated isolates were also more likely to belong to 1 of 2 pulsed-field gel electrophoresis clonal groups in both univariate and multivariate analysis. Community-associated isolates typically possessed different exotoxin gene profiles (eg, Panton Valentine leukocidin genes) compared with health care-associated isolates. CONCLUSIONS: Community-associated and health care-associated MRSA cases differ demographically and clinically, and their respective isolates are microbiologically distinct. This suggests that most community-associated MRSA strains did not originate in health care settings, and that their microbiological features may have contributed to their emergence in the community. Clinicians should be aware that therapy with beta-lactam antimicrobials can no longer be relied on as the sole empiric therapy for severely ill outpatients whose infections may be staphylococcal in origin.
Among 3394 patients with Staphylococcus aureus bacteraemia from the years 1986-89, 88 patients were found whose intravenous catheter and blood grew organisms of the same phage type. Strains of phage type 95 were more frequent among the patients with confirmed catheter-related bacteraemia than among other bacteraemia cases. Strains with particular phage-type patterns occurring with increasing frequency in Denmark during recent years also occurred with significantly higher frequencies among the confirmed catheter-related bacteraemias. No major differences in antibiotic resistance were observed. Patients with catheter-related bacteraemia had, in spite of a higher frequency of underlying diseases, a lower mortality compared with other bacteraemia patients, and endocarditis occurred less frequently (2% vs. 6%). Among 201 S. aureus isolates from catheters in 1988 only strains of group I occurred with increased frequency. The possible role of catheters as selection pressure on the S. aureus population is discussed.
One hundred five Staphylococcus aureus infections occurring in 79 children who were seen in a private office practice were evaluated for response to antibiotic therapy. The value of in vitro disk susceptibility testing in directing antibiotic selection in treatment failures was also examined. Of the total episodes studied, the types of infection studied included vesicular pyoderma (48%), secondary pyoderma (13%), bullous pyoderma (5%), furunculosis (14%), carbunculosis (12%), cellulitis (3%), suppurative otitis media (4%), and paronychia (2%). Comparative treatment efficacy was obtained with perioral erythromycin estolate and erythromycin ethylsuccinate, cefaclor and cephalexin, and clindamycin hydrochloride and dicloxacillin sodium. Penicillin V potassium, ampicillin, and topical bacitracin were generally ineffective. In 23 patients, 27/105 infections were initial treatment failures. Antibiotic disk susceptibility testing predicted these clinical failures and/or the antibiotic that would produce a clinical response in 21 of these 23 patients, suggesting that this office procedure can be of considerable value.