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PubMed2005

Deletion of pT181-like sequence in an smr-encoding mosaic plasmid harboured by a persistent bovine Staphylococcus warneri strain.

OBJECTIVES: The aim was to study the persistence and characteristics of Staphylococcus warneri strains resistant to quaternary ammonium compounds (QACs), including sequencing and analysis of two plasmids proved to carry the smr gene. METHODS: During a 3.5 year period quarter milk samples were collected on three occasions from all lactating cows in a dairy herd. The samples were screened with regard to QAC-resistant bacteria using a selective medium. Thirty randomly selected QAC-resistant S. warneri were typed by PFGE and subjected to plasmid isolation and analysis followed by gene detection using PCR. Two smr-containing plasmids in S. warneri isolates were sequenced. RESULTS: All isolates from the initial collection of quarter milk contained smr residing on a 5.8 kb plasmid (pSW174), which contained regions with high similarities to various plasmids, including pT181, pSK108 and pPI-2. The pT181-like sequence was flanked by 148 bp direct repeats, denoted ISLE49, with high similarity to previously reported sequences of approximately 148 bp, including ISLE39 flanking the insertion sequence IS257 in methicillin-resistant Staphylococcus aureus. All isolates from subsequent collections of quarter milk harboured a smaller smr-containing plasmid (pSW49). Sequence analyses revealed pSW49 (3552 bp) to be an in-part deleted version of pSW174 (5767 bp). CONCLUSIONS: The IS-associated elements found in this study may have a wider role in the integration and excision of DNA sequences in staphylococci than previously reported. The mosaic plasmid structure based on genetic elements of various origins contributes to further knowledge on the flexibility of smr-encoding plasmids.

Animals↗

PubMed2006

Diversity and evolution of blaZ from Staphylococcus aureus and coagulase-negative staphylococci.

OBJECTIVES: To elucidate the diversity and evolutionary history of plasmid- and chromosomally-located blaZ, to detect indications of frequent exchange of blaZ between human and bovine staphylococci and to estimate the frequency of transfer of blaZ between coagulase-negative staphylococci (CoNS) and Staphylococcus aureus of bovine origin. METHODS: blaZ was detected in 143 strains of penicillin-resistant S. aureus and CoNS from five Danish cattle herds (n = 25/23), random CoNS isolates from Denmark (n = 37), a collection of S. aureus from six different countries (n = 52), humans in Denmark (n = 3) and beta-lactamase control strains (n = 3). The sequence was determined in 105 strains and compared to published sequences by pairwise and multiple alignments. Maximum likelihood analysis was performed including bootstrap analysis. Parsimony, neighbour joining and consensus comparisons were performed for recombination. The localization of blaZ was determined by Southern blotting in 108 isolates. RESULTS: All penicillin-resistant strains carried blaZ and showed a similar organization of blaR1 and blaZ. The blaZ gene was localized to a plasmid in only 16 of the resistant strains. Sixty-nine sequences representing 105 isolates and sequences retrieved from public databases were compared. A phylogenetic tree showed that blaZ exists in three evolutionary lines: one group was of plasmid origin, one group was of chromosomal origin and one intermediate group. Sixty-nine sequence types were demonstrated. They translated into 11 BlaZ protein types. The major types all contained strains of both human and bovine origin, and more than one Staphylococcus species, demonstrating a shared gene pool. In a comparison of S. aureus and CoNS obtained from five Danish cattle herds, the same type of blaZ was only detected in one case. CONCLUSIONS: Results indicated a separate evolution for plasmid- and chromosomally-encoded blaZ. Although a common gene pool seems to exist among staphylococci, exchange of blaZ between strains and species is judged to be an extremely rare event.

Alleles↗

PubMed1976

A restriction endonuclease from Staphylococcus aureus.

A specific endonuclease, Sau 3AI, has been partially purified from Staphylococcus aureus strain 3A by DEAE-cellulose chromatography. The enzyme cleaves adenovirus type 5 DNA many times, SV40 DNA eight times but does not cleave double-stranded phi X174 DNA. It recognizes the sequence (see article) and cleaves as indicated by the arrows. Evidence is presented that this enzyme plays a role in the biological restriction-modification system of Staphylococcus aureus strain 3A.

Base Sequence↗

PubMed1998

Adherence of Staphylococcus aureus isolated in peritoneal dialysis-related exit-site infections to HEp-2 cells and silicone peritoneal catheter materials.

BACKGROUND: Peritoneal catheter exit-site infections cause a relevant morbidity in peritoneal dialysis patients and are frequently caused by Staphylococcus aureus. We tested the hypothesis that adherence of exit-site-derived S. aureus to epithelial cells and peritoneal catheter silicone tubes discriminates virulent and less virulent strains. METHODS: The binding of isolated S. aureus to an epithelial cell line (HEp-2) and to silicone tubes was analyzed using light-microscopy or radioactive labeling of bacteria. RESULTS: Of 378 exit-site swabs, 99 (26%) were positive for microbial growth. S. aureus was cultured in 25 of 99 positive swabs; three of 13 swabs taken in exit-site infections grade 3 and 4 that had tested positive for S. aureus. Adherence of S. aureus from exit-site infections grade 2, 3 and 4 to Hep-2 cells did not differ from adherence of bacteria isolated from asymptomatic or moderately inflamed catheter exit sites (grade 0-2). However, binding of S. aureus to silicone tubes was enhanced in grade 0/1 compared with grade 2-4 exit-site isolates. CONCLUSIONS: Staphylococcus aureus is an important pathogen in CAPD-related exit-site infection being isolated in about 6.6% of all exit-site swabs (and in 25% of all positive swabs). Silicone-adhesive strains may be of more clinical significance in peritoneal dialysis patients since adhesion to silicone was increased in S. aureus strains isolated in more severe exit-site infections.

Bacterial Adhesion↗

PubMed1996

Effectiveness of contact isolation during a hospital outbreak of methicillin-resistant Staphylococcus aureus.

Contact isolation has been recommended by the Centers for Disease Control and Prevention for the prevention of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA), but there are few data which prospectively quantitate the effectiveness of contact isolation for this purpose. During an outbreak of MRSA in a neonatal intensive care unit between July 18, 1991 and January 30, 1992, weekly surveillance cultures were performed on all patients. Sixteen of 331 admissions became colonized with MRSA, and 3 (19%) developed infections: bacteremia, conjunctivitis, and dialysis catheter site infection. The isolates from all 16 patients were submitted to plasmid profile analysis and restriction enzyme analysis of whole cell DNA. All of the patients had identical chromosomal patterns and plasmid profiles, which differed from control isolates from other wards, indicating that the outbreak resulted from spread of a unique strain. None of 144 personnel who were cultured after recent contact with newly colonized patients during the outbreak were found to carry MRSA, which suggests that patients were the reservoir for transmission rather than caregivers. The most probable source for each individual transmission was determined based on proximity in time and space and shared exposure to caregivers. The rate of transmission of MRSA from patients on contact isolation was significantly lower (0.009 transmissions per day on isolation) than the rate for patients not on isolation (0.140 transmissions per day unisolated, relative risk = 15.6, 95% confidence interval 5.3-45.6, p < 0.0001). The authors conclude that the risk of nosocomial transmission of MRSA was reduced 16-fold by contact isolation during the outbreak in this neonatal intensive care unit. These data confirm the results of previous studies which have suggested that contact isolation was effective in controlling the epidemic spread of methicillin-resistant Staphylococcus aureus.

Contact Tracing↗

PubMed1996

Native-valve endocarditis caused by Staphylococcus lugdunensis.

Coagulase-negative staphylococci cause about 5% of native-valve endocarditis. Staphylococcus lugdunensis, a recently-described species of coagulase-negative staphylococci, has been reported to cause destructive native-valve endocarditis with a high mortality. We report four consecutive cases of definite Staphylococcus lugdunensis native-valve endocarditis by the Duke criteria over a 4-year period. All patients required urgent aortic valve replacement 1-5 days after admission, and recovered. An intriguing, aspect in the presentation of these patients was a history of vasectomy and inguinal skin breaks in the immediate period preceding the occurrence of endocarditis.

Adult↗

PubMed1990

The effect of HIV infection on phagocytosis and killing of Staphylococcus aureus by human pulmonary alveolar macrophages.

Pulmonary alveolar macrophages (PAM) play a central role in host defense against pulmonary infection. The authors studied the number, viability, and ultrastructure of PAM recovered by bronchoalveolar lavage from normal and HIV-infected subjects, and their ability to phagocytose and kill Staphylococcus aureus. PAM from HIV-infected subjects who did not have pneumonia were present in greater numbers and phagocytosed significantly more opsonized Staphylococcus aureus (32.5% and 27.3% for nonsmokers and smokers, respectively) than did PAM from healthy controls (19.5% and 18.2%). In 15 patients with AIDS and pneumonia (due to Pneumocystis carinii in 13/15), viability of PAM and their phagocytic capacity were significantly reduced; in smokers with AIDS and pneumonia, the PAM yield was also dramatically decreased. Killing of S. aureus was similar by PAM from all patient groups. HIV infection was associated with the electron microscopic finding in PAM of extensively ruffled PAM cell-surfaces and ingestion of lymphocytes. Thus, HIV infection stimulates the phagocytic capacity and produces morphologic changes consistent with the possibility that PAM are activated by this retroviral infection. In patients with AIDS who develop pneumonia, especially in smokers, the number, viability and phagocytic capacity of PAM are significantly decreased; our study could not determine whether this diminished activity reflects evolution of the HIV infection or a secondary effect of the pneumonia.

Adult↗

PubMedDate not supplied

Experimental Staphylococcus epidermidis implant infection in the mouse. Kinetics of rifampin and vancomycin action.

Staphylococcus epidermidis implant infections remain a therapeutic challenge; they frequently result in failure of conservative management and require removal of the implant. This resistance to antibiotic therapy has been ascribed to the presence of a protective bacterial biofilm at the surface of the implant. An animal model of implant associated infection has been developed in which preformed bacterial biofilm catheter segments are implanted intraperitoneally, resulting in a chronic standardized localized infection. The authors have determined the superior rapid action of rifampin (Cieba-Geigy) compared to vancomycin hydrochloride (Eli Lilly) and determined that the combination is superior to either used alone. No rifampin resistant surviving infection was noted, which indicates the significant contribution of mammalian host defenses. This animal model is an excellent vehicle for the study of Staphylococcus epidermidis implant associated infection and the evaluation of the relative efficacy of antibiotic regimens, singly and in combination.

Animals↗

PubMed1997

New model for chronic osteomyelitis with Staphylococcus aureus in sheep.

The purpose of this study was to develop a large animal model for chronic osteomyelitis, suitable for toxicologic research and therapeutic intervention studies. Osteomyelitis was induced in 52 healthy adult Texel sheep by injecting a sclerosing agent and a hemolytic strain of Staphylococcus aureus into the proximal tibial marrow cavity. Evaluation was done by clinical, radiologic, bacteriologic, and histologic parameters for 3 months. Clinical signs of infection consisted of localized soft tissue swelling, pain during the acute phase, and limping in all sheep. Radiologic features were moderate to extensive periosteal reaction, cortical lysis, mild to extensive new bone formation, and frequent development of sequestra limited to the proximal part of the tibia. Cultures were positive for the same strain of Staphylococcus aureus in all but one sheep. Histology showed chronic active inflammation, osteolysis, new woven bone formation, debris, clusters of bacteria, and surrounding granulation tissue. It was necessary to administer a single prophylactic dose of antibiotics 1 hour after surgery to prevent fatal sepsis. It was concluded that sheep are a suitable model for chronic osteomyelitis.

Animals↗

PubMedDate not supplied

Methicillin-resistant Staphylococcus aureus eradication in a burn center.

Methicillin-Resistant Staphylococcus aureus and its detection, virulence, and significance relative to morbidity, epidemics, and cost have been widely discussed in the literature. Although some experts recommend against attempting to eradicate the organism, our health center decided that under the circumstances this course should be pursued. This article describes the outbreak of Staphylococcus aureus, the rationale for pursuing its eradication, the measures successful in doing so, and the relative costs involved.

Burn Units↗

PubMed1987

Staphylococcus aureus meningitis: a broad-based epidemiologic study.

In an effort to ascertain important epidemiologic and prognostic risk factors, we analyzed 33 cases of Staphylococcus aureus meningitis occurring over an 8-year period (1976 to 1984). Staphylococcus aureus caused 6% of all bacterial meningitis at our University Hospital. Fifty percent of cases were pediatric and included 7 newborn infants, of whom 71% were either premature or had low birth weight. Major underlying diseases were: central nervous system (CNS) disorders (55%), endocarditis (21%, predominantly intravenous drug abusers), other sites of infection (27%), and prematurity (24%). Fifty-seven percent of patients were bacteremic and 41% of those had concomitant bacteriuria. Hypoglycorrhachia was present in 27% of cases, positive cerebrospinal fluid (CSF) Gram stain in 20%, disseminated intravascular coagulation (DIC) in 19%, and methicillin-resistant organisms in 18%. Cerebrospinal fluid cultures remained positive for a protracted period (mean, 6.7 days) regardless of the presence or absence of a CNS shunt. Overall mortality was 21%. Favorable outcomes were associated with the eventual presence of sterile CSF (15.4% vs. 100% mortality) and the removal of foreign bodies (10% vs. 67% mortality). Mortality was also associated (p less than 0.5) with the presence of diabetes mellitus, age greater than 60, obtundation or coma on presentation, bacteremia, or DIC. Cure correlated (p less than .05) with CNS shunt-associated infections, age less than 1, normal neurologic examinations on presentation, or the absence of DIC or bacteremia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed2002

Endocarditis caused by Staphylococcus lugdunensis.

We describe a case of native valve endocarditis caused by Staphylococcus lugdunensis, a perineal skin commensal, and review 28 other cases from the medical literature. Correctly identifying this coagulase-negative organism is critical because endocarditis is usually associated with left sided valvular disruption and life-threatening embolic complications, reminiscent of disease caused by Staphylococcus aureus. Urgent surgical intervention is necessary in most cases.

Adolescent↗

PubMed1989

Evaluation of antibacterial sensitivity testing methods for methicillin-resistant Staphylococcus aureus in a dermatology outpatient population.

Over a period of one year, 1986-1987, 116 strains of Staphylococcus aureus were isolated from patients attending two outpatient dermatology clinics in Houston, Texas. The purpose of this study was to evaluate the adequacy of routine antibiotic sensitivity testing methods for detecting methicillin-resistant Staphylococcus aureus (MRSA). The Kirby-Bauer disk diffusion method was compared with a commercially available screening medium containing 6 micrograms/ml of oxacillin and 4% NaCl. The minimal inhibitory concentration (MIC) of methicillin, oxacillin, and oxacillin with 4% NaCl to S aureus using the agar dilution method was also determined. Approximately 90% of S aureus strains produced beta-lactamase and were resistant to penicillin and ampicillin. By disk diffusion, no strains were resistant to methicillin, though diameters of zones of inhibition were between 10 and 14 mm in seven strains. All strains proved to be sensitive to methicillin by MIC determinations and on the oxacillin-NaCl screening medium. The MIC of methicillin was 2.5 micrograms/ml for the majority of strains of S aureus, between 0.16 and 0.31 microgram/ml for oxacillin, and 0.08 to 0.16 microgram for oxacillin with 4% NaCl. We concluded that the incidence of MRSA in an outpatient dermatology population is low, and a combination of disk diffusion and oxacillin-NaCl screening is adequate for testing sensitivity.

Adolescent↗

PubMed1998

Prevalence of methicillin-resistant Staphylococcus aureus in a dermatology outpatient population.

BACKGROUND: The number of methicillin-resistant STaphylococcus aureus (MRSA) infections in the hospital setting is increasing but little is known of its prevalence in the community. In a 1986-1987 study, the prevalence in dermatology outpatient clinics was <0.9%. This study reports changes in the same facilities from 1988 through 1996. METHODS: Culture results and antimicrobial susceptibility patterns were reviewed for the population for the period 1988 through 1996. RESULTS: We report a gradual increase of MRSA from 1.5% of all strains of Staphylococcus aureus in 1988 to 11.9% in 1996 in these outpatient facilities. Susceptibility data indicate that the MRSA strains isolated in 1996 are more resistant to oral agents such as ciprofloxacin and tetracycline, while all strains remain susceptible to the intravenous agent vancomycin. CONCLUSION: The prevalence of MRSA in the community is increasing and should be considered when selecting a treatment regimen for staphylococcal infections.

Ambulatory Care Facilities↗

PubMed2005

Complete osteolysis of the dens with atlantoaxial luxation caused by infection with Staphylococcus aureus: a case report and review of the literature.

STUDY DESIGN: Case report. OBJECTIVES: To present a case of complete osteolysis of the dens and accompanying luxation of the atlantoaxial joint, on the basis of a Staphylococcus aureus infection. SUMMARY OF BACKGROUND DATA: To date, complete osteolysis of the dens followed by atlantoaxial dislocation has only been reported as a rare complication in patients with tuberculosis but not as secondary to a Staphylococcus aureus infection. METHODS: Because of emerging neurological complications in both upper extremities, we chose closed reduction and temporary Halo-fixation together with appropriate antibiotic coverage as primary treatment followed by an operative stabilization with Magerl fusion (Galli fusion combined with transarticular screw fixation of C1 and C2). RESULTS: After the operative procedure (Magerl fusion), immediate pain relief was achieved as well as almost complete resolution of neurological deficits. CONCLUSIONS: To our knowledge, this presents the first reported case of a complete destruction of the dens, as a result of a purulent bacterial infection leading to atlantoaxial luxation. Our case demonstrates that infections of the atlantoaxial region are difficult to diagnose and are seen mostly in immunocompromised patients, such as patients with diabetes. Furthermore, it proves that other infections besides tuberculosis can lead to complete osteolytic destruction of the atlantoaxial joint.

Adult↗

PubMed2004

Management and outcome of children with skin and soft tissue abscesses caused by community-acquired methicillin-resistant Staphylococcus aureus.

BACKGROUND: Although the epidemiology of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been explored in many investigations, management of this emerging infection has not been well-studied. For non-methicillin-resistant Staphylococcus aureus skin and soft tissue abscesses, incision and drainage is generally adequate therapy without the use of antibiotics, but this has not been established for CA-MRSA. METHODS: Children presenting to Children's Medical Center of Dallas for management of skin and soft tissue abscesses caused by culture-proved CA-MRSA were prospectively followed. We analyzed data from the initial evaluation and from two follow-up visits that focused on the management and outcome of CA-MRSA infection. Retrospective chart review was performed 2 to 6 months after the initial visit. RESULTS: Sixty-nine children were identified with culture-proved CA-MRSA skin and soft tissue abscess. Treatment consisted of drainage in 96% of patients and wound packing in 65%. All children were treated with antibiotics. Five patients (7%) were prescribed an antibiotic to which their CA-MRSA isolate was susceptible before culture results were known. Four patients (6%) required hospital admission on the first follow-up; none of these patients had received an antibiotic effective against CA-MRSA. A significant predictor of hospitalization was having a lesion initially >5 cm (P = 0.004). Initial ineffective antibiotic therapy was not a significant predictor of hospitalization (P = 1.0). Of the 58 patients initially given an ineffective antibiotic and managed as outpatients, an antibiotic active against CA-MRSA was given to 21 (36%) patients after results of cultures were known. No significant differences in response were observed in those who never received an effective antibiotic than in those who did. CONCLUSIONS: Incision and drainage without adjunctive antibiotic therapy was effective management of CA-MRSA skin and soft tissue abscesses with a diameter of <5 cm in immunocompetent children.

Abscess↗

PubMed2003

A prospective multicenter study of Staphylococcus aureus bacteremia: incidence of endocarditis, risk factors for mortality, and clinical impact of methicillin resistance.

Our objectives were to determine the incidence of endocarditis in patients whose Staphylococcus aureus bacteremia was community-acquired, related to hemodialysis, or hospital-acquired; to assess clinical factors that would reliably distinguished between S. aureus bacteremia and S. aureus endocarditis; to assess the emergence of methicillin-resistant S. aureus (MRSA) as a cause of endocarditis; and to examine risk factors for mortality in patients with S. aureus endocarditis. We conducted a prospective observational study in 6 university teaching hospitals; we evaluated 505 consecutive patients with Staphylococcus aureus bacteremia. Thirteen percent of patients with S. aureus bacteremia were found to have endocarditis, including 21% with community-acquired S. aureus bacteremia, 5% with hospital-acquired bacteremia, and 12% on hemodialysis. Infection was due to MRSA in 31%. Factors predictive of endocarditis included underlying valvular heart disease, history of prior endocarditis, intravenous drug use, community acquisition of bacteremia, and an unrecognized source. Twelve patients with bacteremia had a prosthetic valve; 17% developed endocarditis. Unexpectedly, nonwhite race proved to be an independent risk factor for endocarditis by both univariate and multivariate analyses. Persistent bacteremia (positive blood cultures at day 3 of appropriate therapy) was identified as an independent risk factor for both endocarditis and mortality, a unique observation not reported in other prospective studies of S. aureus bacteremia. Patients with endocarditis due to MRSA were significantly more likely to have complicating renal insufficiency and to experience persistent bacteremia than those with endocarditis due to MSSA. The 30-day mortality was 31% among patients with endocarditis compared to 21% in patients who had bacteremia without endocarditis (p = 0.055). Risk factors for death due to endocarditis included severity of illness at onset of bacteremia (as measured by Apache III and Pitt bacteremia score), MRSA infection, and presence of atrioventricular block on electrocardiogram. Patients with S. aureus bacteremia who have community acquisition of infection, underlying valvular heart disease, intravenous drug use, unknown portal of entry, history of prior endocarditis, and possibly, nonwhite race should undergo echocardiography to screen for the presence of endocarditis. We recommend that blood cultures be repeated 3 days following initiation of antistaphylococcal antibiotic therapy in all patients with S. aureus bacteremia. Positive blood cultures at 3 days may prove to be a useful marker in promoting more aggressive management, including more potent antibiotic therapy and surgical resection of the valve in endocarditis cases. MRSA as the infecting organism should be added to the list of risk factors for consideration of valvular resection in cases of endocarditis.

Bacteremia↗

PubMed2005

Blood neutrophil bactericidal activity against methicillin-resistant and methicillin-sensitive Staphylococcus aureus during cardiac surgery.

Whether methicillin-resistant Staphylococcus aureus (MRSA) constitutes per se an independent risk factor for morbidity and mortality after surgery as compared with methicillin-sensitive Staphylococcus aureus (MSSA) remains a subject of debate. The aim of this study was to assess whether innate defenses against MRSA and MSSA strains are similarly impaired after cardiac surgery. Both intracellular (isolated neutrophil functions) and extracellular (plasma) defenses of 12 patients undergoing scheduled cardiac surgery were evaluated preoperatively (day 0) and postoperatively (day 3) against two MSSA strains with a low level of catalase secretion and two MRSA strains with a high level of catalase secretion, inasmuch as SA killing by neutrophils relies on oxygen-dependent mechanisms. After surgery, an increase in plasma concentration of IL-10, an anti-inflammatory cytokine able to inhibit reactive oxygen species secretion and bactericidal activity of neutrophils, was evidenced. Despite the fact that univariate analysis suggested a specific impairment of neutrophil functions against MRSA strains, two-way repeated-measures ANOVA failed to demonstrate that the effect of S. aureus phenotype was significant. On the other hand, an increase in type-II secretory phospholipase A2 activity, a circulating enzyme involved in SA lysis, was evidenced and was associated with an enhancement of extracellular defenses (bactericidal activity of plasma) against MRSA. Overall, cardiac surgery and S. aureus phenotype had a significant effect on plasma bactericidal activity. Cardiac surgery was characterized by enhanced antibacterial defenses of plasma, whereas neutrophil killing properties were reduced. The overall effect of S. aureus phenotype on neutrophil functions did not seem significant.

Aged↗