Scanning electronmicroscopy of Staphylococcus aureus and Enterococcus faecalis exposed to daptomycin

The novel lipopeptide antibiotic, daptomycin, at a concentration of 8 mg/L, caused gross morphological changes in both a methicillin-sensitive and a methicillin-resistant strain of Staphylococcus aureus and in a strain of Enterococcus faecalis. The earliest (after 1 h) surface lesion observed was the appearance of boss-like processes randomly distributed on the cell surface. Later, grossly deformed bacteria were seen and in two of the three bacteria prolonged exposure led to degeneration of the cells into an amorphous syncytial mass. Omission of calcium (which is known to potentiate the activity of daptomycin) from the culture medium did not affect the morphological response to an inhibitory concentration of the antibiotic.     

Molecular Epidemiology of Staphylococcus aureus and Enterococcus faecalis in Endophthalmitis

Genomic DNA fingerprint analysis was performed on 39 Staphylococcus aureus and 28 Enterococcus faecalis endophthalmitis isolates collected from multiple clinical centers. Among 21 S. aureus genomic DNA fingerprint patterns identified, five clonotypes were recovered from multiple unrelated patients and accounted for 58.9% (23 of 39) of the isolates analyzed. Compared with strains having unique genomic DNA fingerprint patterns, the S. aureus clonotypes occurring more than once were more likely to result in visual acuities of 20/200 or worse (P = 0.036 [χ² test]). In contrast to the S. aureus isolates, the E. faecalis endophthalmitis isolates were a clonally diverse population, enriched for the expression of a known toxin, cytolysin, which is plasmid encoded.

Infectious endophthalmitis is a sight-threatening clinical crisis that occurs as a complication of ocular surgery (postoperative endophthalmitis) or penetrating ocular injury (posttraumatic endophthalmitis). The severity of vision loss in endophthalmitis is related to the pathogenic potential of the infecting organism (7, 19, 25–29, 33). Coagulase-negative staphylococci are generally associated with final visual acuities of 20/40 or better, whereas in endophthalmitis caused by more virulent organisms such as Staphylococcus aureus, Enterococcus faecalis, or Bacillus cereus, visual outcomes ranging from 20/100 to enucleation occur in approximately 50 to 90% of cases (1, 5, 7). Despite a general association between visual outcome and the infectious agent, relatively little is known about the species-specific factors that account for the characteristic severity of each disease.We previously focused on determining the role of secreted bacterial toxins in the pathogenesis of endophthalmitis caused by S. aureus and E. faecalis by using well-characterized laboratory strains in animal models of disease. These studies showed that cytolytic E. faecalis not only causes more fulminant disease but also renders the infection unresponsive to therapeutic intervention (17, 18). The production of most secreted and cell surface proteins in S. aureus is coordinately controlled by chromosomal regulatory loci termed accessory gene regulator (agr) and staphylococcal accessory regulator (sar) (6, 16, 20). Mutant strains of S. aureus with insertional mutations in the sar and agr loci are attenuated in virulence in experimental endophthalmitis compared with parental strains (3, 4). Since sar and agr affect the expression of 12 or more unrelated genes (6, 20), the staphylococcal toxin(s) that contributes most significantly to the severity of disease has not yet been identified.To further analyze the bacterial factors that contribute to the pathogenesis of endophthalmitis, we performed a genomic DNA fingerprint analysis on 39 S. aureus and 28 E. faecalis strains isolated from the vitreous or aqueous humor of endophthalmitis patients treated at multiple clinical centers. The purpose of this investigation was to assess whether common traits that may be related to ocular colonization and/or the severity of disease outcome exist among isolates of a particular species.The S. aureus and E. faecalis isolates analyzed in this study were collected from patients with endophthalmitis between 1984 and 1995 at Cullen Eye Institute, Houston, Tex. (CE), Dean A. McGee Eye Institute, Oklahoma City, Okla. (DM), University of Pittsburgh School of Medicine, Pittsburgh, Pa. (UP), King Fahd Hospital, Al Hasa, Saudi Arabia (KF) (a kind gift from LouAnn Bartholomew), and Bascom Palmer Eye Institute, Miami, Fla. (BP). S. aureus strains were collected from DM (7 isolates), UP (7 isolates), and BP (25 isolates), while E. faecalis strains were collected from CE (10 isolates), DM (3 isolates), UP (4 isolates), KF (2 isolates), and BP (9 isolates). Twenty-nine additional S. aureus clinical isolates of extraocular origin were a kind gift from Mark Huycke, Veterans Administration Medical Center, Oklahoma City, Okla. Twenty-one S. aureus keratitis isolates were obtained from the Alcon Microbiology Culture Collection (Fort Worth, Tex.).Pulsed-field gel electrophoretic analysis of endophthalmitis isolates.Bacterial genomic DNA was prepared as previously described (24), except that lysostaphin (50 μg/ml) was added to the lysis solution for the preparation of S. aureus chromosomal DNA. Isolates with similar banding patterns and no more than three band differences were considered clonally related (32). Isolates with banding patterns similar to clonally related strains but with no more than four band differences were considered subtypes of the clonal group. Once isolates were recognized as having identical or similar banding patterns, a second gel containing all isolates from the same group was run to verify clonal relationships. Twenty-one distinct fingerprint patterns were identified among the S. aureus isolates. Of these, five clonotypes were present more than once and accounted for 58.9% (23 of 39) of the total number of isolates. The clonotype represented most frequently was designated SA1 and accounted for 25.6% (10 of 39) of the isolates tested (Fig. ​(Fig.1).1). Isolates in this group were derived from each of the clinical centers from which S. aureus isolates were obtained (DM, UP, and BP). Clonotypes SA2 (n = 4) and SA3 (n = 2) were also derived from multiple clinical centers (DM and BP). All isolates comprising clonotypes SA4 (n = 3) and SA5 (n = 4) were derived from the same clinical center (BP) (Fig. ​(Fig.1).1). The remaining 16 isolates (41%) were present only once (data not shown) and were derived from all three clinical centers. To ensure that the general clonality observed among the S. aureus endophthalmitis isolates was not attributable to a methicillin-resistant S. aureus (MRSA) genotype (21), strains comprising each of the five S. aureus clonotypes were analyzed for the presence of the mecA antibiotic resistance determinant (8). Briefly, bacteria from a 0.5-ml suspension of bacterial cells in phosphate-buffered saline were lysed by boiling in a sealed tube for 10 min, followed by centrifugation (10,000 × g for 1 min) to remove cell debris. PCR was performed on cell lysates with previously published mecA-specific primers (8). Only clonotype SA4 (three isolates), was found to be mecA positive; all other clonotypes were mecA negative. Open in a separate windowFIG. 1PFGE of SmaI-digested chromosomal DNA of endophthalmitis-derived S. aureus clinical isolates collected from three clinical centers, BP, DM, and UP. Separate panels show clonally related isolates. Where present, subtypes are designated with the suffix 1 or 2. Molecular size standards are the New England Biolabs lambda ladder.In contrast to the S. aureus isolates, substantial clonal diversity was observed among the E. faecalis isolates. Of the 28 isolates collected from five clinical centers (CE, DM, UP, KF, and BP), 25 unique genomic DNA fingerprints were identified. Two E. faecalis clonotypes, EF1 (n = 3) and EF2 (n = 2), occurred more than once (Fig. ​(Fig.2).2). EF1 isolates were derived from either UP (two isolates) or CE (one isolate), while EF2 isolates were derived from CE and DM. The remaining 23 E. faecalis endophthalmitis isolates had unique genomic DNA fingerprints. Open in a separate windowFIG. 2PFGE of SmaI-digested chromosomal DNA of selected endophthalmitis-derived E. faecalis clinical isolates collected from five clinical centers, BP, DM, UP, KF, and CE. Clonally related strains are identified below the panels. Molecular size standards are the New England Biolabs lambda ladder.Comparison of S. aureus endophthalmitis clonotypes with S. aureus isolated from various sources.Since it was determined that the general clonality observed among the endophthalmitis-derived S. aureus isolates was not due to an MRSA genotype, it was considered that the clonotypes identified might represent species subsets uniquely associated with ocular infection. To test this hypothesis, we examined chromosomal DNA fingerprints for 21 S. aureus keratitis isolates and 29 S. aureus strains isolated from extraocular infections, such as soft-tissue, catheter-associated, and surgical-wound infections. The frequency of occurrence of clonotypes SA1 to SA5 within these populations of isolates is shown in Table ​Table1.1. Clonotypes SA1, SA3, SA4, and SA5 were found among the S. aureus keratitis isolates and accounted for 47.6% (10 of 21) of the total number of isolates analyzed; the remaining isolates in this group all showed unique genomic DNA fingerprints. Interestingly, as in the case of endophthalmitis-derived clonotypes SA1, SA2 and SA3, keratitis-derived clonotypes SA1, SA3, SA4, and SA5 were collected from geographically diverse clinical centers (6a). All five endophthalmitis-derived S. aureus clonotypes occurred at least once among the extraocular-infection isolates. One new clonotype consisting of three strains (SA6), which was not represented among either the endophthalmitis- or keratitis-derived isolates, was identified among the soft-tissue-wound isolates. The frequency of occurrence of clonotype SA1 among the extraocular-infection isolates was approximately 2.5-fold lower than that observed for the endophthalmitis isolates (10% versus 25.6%); however, the difference was not statistically significant (P = 0.136 [Fisher’s exact test]). When analyzed in combination, the frequency of occurrence of clonotypes SA1 to SA5 was not significantly different between the groups (P = 0.340 [χ² test]). These results indicate that although clonotypes SA1 to SA5 are isolated frequently from ocular infections, these isolates are not unique to this site of infection. TABLE 1Frequency of S. aureus clonotypes SA1 to SA5 among isolates from various sources

Outbreak of methicillin-resistant Staphylococcus aureus in general hospital intensive care unit]

Mantes' hospital polyvalent intensive care unit (ICU) experienced an outbreak episode caused by methicillin resistant Staphylococcus aureus (MRSA). Suspicion of physicians was strengthened by observing the weekly reading of multiresistant germs and the significative increase of MRSA carriers incidence rate, compared with the number of admission in the ICU: 5.5% to 11.3%. This outbreak was surprising: it happened immediately after the installation in a new hospital and the reinforcement of nosocomial infection surveillance (systematic screening of every patient admitted to the I.U.C., his isolation if he presents risk factors to multiresistant germs, increasing of handwashing stations). The overlapping period of hospitalisation concerning the 13 patients being reported as SARM carrier, having the same antibiogram, and the epidemic curve suggested a cross contamination. The index case was a MRSA carrier the day of her admission and have had a recent hospitalisation in a high risk unit. MRSA has always been isolated in nasal swab. Six patients among the thirteen carriers developed an infection and have been treated by vancomycin: two systemic infections and four pulmonary infections. The mortality rate was 33% and only one of them seemed to be directly due to MRSA. Area samples were all negative. The clinical staff have been screened with nasal swab. We identified only one nasal MRSA carrier. The pulsed-field gel electrophoresis study showed that 9/11 which have been analysed were identical. This outbreak brought about staff, more sensibilisation to the nosocomial infection and updating of plain hygien rules leaded to its stop five months later.     

Time to positivity of follow-up blood cultures in patients with persistent Staphylococcus aureus bacteremia

We investigated the clinical usefulness of time to blood culture positivity (TTP) of follow-up positive blood cultures (FUPBC) in patients with persistent Staphylococcus aureus bacteremia (SAB). Of the patients who did not have resolution of SAB after primary therapeutic intervention (PTI), patients who had decreases in TTP of FUPBC after PTI more frequently experienced 30-day mortality or secondary foci of infection than those who did not have decrease in TTP (83.3% vs. 28.6%; p?=?0.005).     

Staphylococcus aureus nasal carriage as a marker for subsequent staphylococcal infections in intensive care unit patients

From January to December 1994, 752 consecutive patients admitted to intensive care units (ICU) for more than two days were studied prospectively forStaphylococcus aureus colonization and infection. Nasal swabs were obtained at admission and weekly during the ICU stay. At ICU admission 166 patients (22.1%) wereStaphylococcus aureus nasal carriers, while 586 were free of nasal colonization. Of the 166 nasal carriers, 163 harbored methicillin-sensitiveStaphylococcus aureus (MSSA) and three methicillinresistantStaphylococcus aureus (MRSA). During the ICU stay 24 of the 586 noncolonized patients became nasal carriers (11 MSSA and 13 MRSA), and one nasal carrier initially colonized by MSSA was recolonized by MRSA. Staphylococcal infections were documented in 51 (6.8%) of the total 752 patients. After 14 days of ICU stay, the probability of developing staphylococcal infections was significantly higher for those patients who were nasal carriers at ICU admission than for those found to be initially negative (relative risk 59.6, 95% Cl 20.37–184.32; p<0.0001). In patients with ICU-acquired nasal colonization, most infections were documented prior to or at the time of the detection of the nasal colonization; thus, in this group of patients nasal carriage showed a lower predictive value for subsequentStaphylococcus aureus infections than that described classically. Paired isolates of nasal colonizing and clinical strains were studied by pulsed-field gel electrophoresis (PFGE) andmecA polymorphism analysis in 30 patients; identity was demonstrated in all but two patients. The results suggest that, outside the setting of an outbreak of MRSA, the detection ofStaphylococcus aureus nasal carriers on admission may be particularly useful in identifying those patients who are at high risk for developing staphylococcal infections during their ICU stay.     

Molecular characterization of epidemic ciprofloxacin- and methicillin-resistant Staphylococcus aureus strains colonizing patients in an intensive care unit.

Eighteen methicillin-resistant Staphylococcus aureus (MRSA) samples isolated from patients and the environment in an intensive care unit (ICU) during a routine surveillance were tested for antimicrobial resistance and typed by pulsed-field gel electrophoresis. Three pulsed-field patterns were observed. Sixteen were ciprofloxacin resistant and had identical pulsed-field patterns. The results suggested that a ciprofloxacin-resistant MRSA clone had contaminated the environment and spread among patients. This study demonstrates the application of infection control surveillance combined with strain typing in detecting MRSA colonization in the ICU where it was not known to exist.     

Use of surveillance cultures and enteral vancomycin to control methicillin-resistant Staphylococcus aureus in a paediatric intensive care unit

This study assessed the effects of throat and gut surveillance, combined with enteral vancomycin, on gut overgrowth, transmission of methicillin-resistant Staphylococcus aureus (MRSA), infections and mortality in patients admitted to a paediatric intensive care unit (PICU). A 4-year prospective observational study was undertaken with 1241 children who required ventilation for >or=4 days. Patients identified as MRSA carriers following surveillance cultures of throat and rectum received enteral vancomycin. Twenty-nine (2.4%) children carried MRSA, 19 on admission and nine during treatment in the PICU; one patient was not able to be evaluated. Overgrowth was present in 22 (75%) of the carriers. Ten (0.8%) children developed 21 MRSA infections (15 exogenous infections in eight children at a median of 8 days (IQR 3-10.5); five primary endogenous infections at a median of 3 days (IQR 1-25) in three children when they were in overgrowth status; one child developed both types of infection). Enteral vancomycin reduced gut overgrowth significantly, completely preventing secondary endogenous infections. Transmission occurred on nine occasions over a period of 4 years. Four patients died, two (5.9%) with MRSA infection, giving a mortality (11.8%) similar to the study population (9.8%). No emergence of vancomycin-resistant enterococci or S. aureus with intermediate susceptibility to vancomycin was detected. A policy based on throat and gut surveillance, combined with enteral vancomycin, for critically-ill children who were MRSA carriers was found to be effective and safe, and challenges the recommended guidelines of nasal swabbing followed by topical mupirocin.     

Rapid detection of Staphylococcus aureus bacteremia and methicillin resistance by real-time PCR in whole blood samples

We prospectively evaluated a real-time polymerase chain reaction (PCR) approach for the rapid diagnosis of Staphylococcus aureus bacteremia and presence of the mecA gene in 902 blood samples from 468 infectious episodes of 384 patients. Eight of 12 blood culture (BC)-confirmed samples were positive by the S. aureus-specific PCR. In addition, the mecA gene PCR correctly detected all cases of BC-confirmed methicillin-resistant Staphylococcus aureus (MRSA) infection. A positive PCR result was also obtained in ten of 462 BC-negative infectious episodes, including three patients with culture-confirmed S. aureus infection at other body sites. Juliane Winter and Susanne Gebert contributed equally to this work.     

Independent risk factors for the co-colonization of vancomycin-resistant Enterococcus faecalis and methicillin-resistant Staphylococcus aureus in the region most endemic for vancomycin-resistant Staphylococcus aureus isolation

In the majority of cases of vancomycin-resistant Staphylococcus aureus (VRSA), vancomycin-resistant Enterococcus faecalis (VR E. faecalis) served as the vanA donor to S. aureus. Previous studies that evaluated the risk factors for co-colonization with VRE and MRSA did not differentiate between VR E. faecalis and VR E. faecium. This study aimed to identify variables associated with VR E. faecalis and MRSA co-colonization. A retrospective case–control study from January 2008 to December 2009 was conducted at the Detroit Medical Center. Data were extracted from charts and pharmacy records. Unique patients co-colonized with VR E. faecalis and MRSA (defined as isolation of MRSA within 7 days of VR E. faecalis isolation) were compared with patients with VR E. faecalis who were not co-colonized with MRSA. A total of 546 patients with VR E. faecalis isolation were identified. 85 (15.6 %) VR E. faecalis patients were co-colonized with MRSA and 461 (84.4 %) VR E. faecalis patients were not co-colonized with MRSA. The mean age of the study cohort was 65.9?±?16.4 years, 424 (77.7 %) were African–American, and 270 (49.5 %) were residing in long-term care institutions. Independent predictors of co-colonization of VR E. faecalis and MRSA were male gender, impaired consciousness, ICU stay prior to VR E. faecalis isolation, indwelling devices, and isolation of VR E. faecalis from wounds. MRSA was frequently isolated from the same culture specimen as VR E. faecalis (n?=?39, 45.9 %), most commonly from wounds. This large study of patients with VR E. faecalis identified the severity of illness, indwelling devices, and chronic wounds as independent predictors of co-colonization with VR E. faecalis and MRSA     

Methicillin-resistant Staphylococcus aureus (MRSA) in an intensive care unit: a one-year survey

Methicillin-resistant Staphylococcus aureus (MRSA) is frequently isolated in nosocomial outbreaks. In our study, we analysed the occurrence of colonisation and infection in an Intensive Care Unit of our hospital during a 12-month period. We also evaluated the possibility of using automated ribotyping as a molecular method in order to type the isolates. Twice a week a nasal swab and a rectal swab were performed on all patients; from ventilator-assisted patients, a sputum culture was also taken. All the MRSA isolated were identified by using commonly phenotypic procedures and on all isolates susceptibility tests were performed. An automated ribotyping using EcoRI was also done. Out of 292 patients enrolled in the study, 205 were never colonised (group N); among the other 87 who were colonised by MRSA (29.8%), 40 patients (group A) were MRSA carriers at the time of admission, while 47 (group B) were colonised in the ICU. Twenty-seven patients (11 from group A, 15 from group B and 1 from group N) developed 31 infections due to MRSA. Patients from group A exhibited, as a rule, worse clinical conditions than those from the other two groups. For the former group, MRSA infection was frequently systemic (sepsis), while in group B pneumonia was the predominant infection. The prevalence of colonisations in our study was 30%, which is a value comparable to those presented by other authors in similar cases. MRSA colonisation is a necessary condition for subsequent infections in almost all cases, with an average lag of 7 days. Susceptibility tests were non-discriminating among the isolates: all the strains were susceptible to glycopeptides; nearly all of them were resistant to erythromycin, clindamycin, ciprofloxacin and gentamicin. Automated ribotyping allowed us to distinguish 12 different ribogroups, the most frequent of which was composed of 146 isolates. In our study, this molecular method was able to define a possible endemic clone that should be better investigated by using methods with a higher discriminatory power, such as RAPD or PFGE. The method that we employed is highly reliable, easy to perform and not time-consuming. In our opinion, it could be the method of choice in the first screening of high numbers of isolates.     

Long persistence of methicillin-susceptible strains of Staphylococcus aureus causing sepsis in a neonatal intensive care unit

Molecular epidemiology of Staphylococcus aureus strains causing bacteremia in neonates during 2002 to 2005 revealed seven clones, with four MSSA clones responsible for 80% of the cases. Some clones persisted or reappeared throughout the study. Three bacteremic clones were found colonizing health care workers (HCWs), particularly clone C, which was harbored by at least 15% of HCWs.     

A recommendation to perform a blood culture before the administration of intravenous antibiotics increased the detection of Staphylococcus aureus bacteremia

In 2004, the Surviving Sepsis Campaign was launched to increase awareness and improve the outcome of severe sepsis. Accordingly, in Jönköping County, Sweden, a strong recommendation to perform a blood culture before the start of intravenous antibiotic treatment was introduced in 2007. Moreover, a reminder was included in the laboratory report to consult an infectious disease specialist when Staphylococcus aureus was isolated from a blood culture. Retrospectively, patients with at least one blood culture growing S. aureus during 2002 through 2003 (pre intervention n?=?58) or during 2008 through 2009 (post intervention n?=?100) were included. Medical records were evaluated regarding clinical data and outcome. Blood culture isolates were characterized by antibiotic susceptibility testing (AST) and S. aureus protein A (spa) gene typing. The annual incidence of S. aureus bacteremia (SAB) increased from 28 per 100,000 inhabitants at the pre intervention period to 45 per 100,000 at the post intervention period (p?=?0.046). During post intervention, the SAB incidence was significantly higher in men (p?=?0.009). The mortality rate during hospital stay was 14 % during pre intervention and 18 % during post intervention (p?=?0.47). The most common spa types were t012 and t084. The Surviving Sepsis Campaign resulted in an increased number of detected cases of SAB. The mortality rate was the same before and after the intervention, and no spa type correlated to certain clinical manifestations or mortality.     

An outbreak of methicillin-resistant Staphylococcus aureus infection in patients of a pediatric intensive care unit and high carriage rate among health care workers.

BACKGROUND AND PURPOSE: Methicillin-resistant Staphylococcus aureus (MRSA) has been the leading cause of nosocomial infections in many hospitals. To investigate the impact of carriage by health care workers (HCWs) on patient transmission, surveillance culture was performed following an outbreak of MRSA in a pediatric intensive care unit (PICU). METHODS: Isolates from 61 HCWs and 10 environmental sites were collected. Pulsed-field gel electrophoresis (PFGE) and antibiogram analysis were performed to determine the clonal relationship between isolates and potential routes of transmission. RESULTS: The overall carriage rate of HCWs was 67.2% (41/61) for S. aureus and 26.2% (16/61) for MRSA. One MRSA was isolated from the 10 environmental sites sampled. Two major MRSA clusters were identified based on the PFGE patterns. Isolates with indistinguishable PFGE patterns (pulsotype A) were found in all patient isolates from the outbreak, from several HCWs plus the environmental isolate; all were resistant to ciprofloxacin, clindamycin, erythromycin, gentamicin, tetracycline, and trimethoprim-sulfamethoxazole. Interestingly, the isolate from a patient who had prolonged hospitalization in PICU had PFGE patterns (pulsotype B) distinct from the strains involved in the outbreak. This strain was susceptible to ciprofloxacin and trimethoprim-sulfamethoxazole, and was also found in several HCWs. Thus, there appeared to be 2 main MRSA clones circulating in the PICU of our hospital. CONCLUSIONS: Person-to-person and environment-to-person (or vice versa) transmissions are documented in this study. Strict hand washing before and after patient contact must be enforced and closely monitored, as it is the principal preventive measure in containing the spread of MRSA. To prevent the emergence of vancomycin-resistant MRSA and the further transmission of multidrug-resistant organisms, implementation of periodic and routine active surveillance cultures as part of infection control measures may also be evaluated.     

Methicillin-resistant Staphylococcus caprae in a neonatal intensive care unit

Staphylococcus caprae, a hemolytic coagulase-negative staphylococcus that is infrequently associated with humans, was initially detected in specimens from six infants in our neonatal intensive care unit due to phenotypic characteristics common to methicillin-resistant Staphylococcus aureus. These isolates were subsequently identified as S. caprae by the Automated RiboPrinter microbial characterization system. This prompted an 8-month retrospective investigation in our neonatal intensive care unit. S. caprae was the cause of 6 of 18 episodes of coagulase-negative staphylococcal bacteremia, was the most common coagulase-negative staphylococcus recovered from the nares of 6 of 32 infants surveyed in a methicillin-resistant S. aureus surveillance program, and was isolated from 1 of 37 health care providers' hands. Of 13 neonatal intensive care unit isolates tested, all were methicillin resistant and positive for the mecA gene. All 21 isolates were found to be a single strain by Automated RiboPrinter and pulsed-field gel electrophoresis with ApaI or SmaI digestion; ApaI was more discriminating in analyzing epidemiologically unrelated strains than Automated RiboPrinter or electrophoresis with SmaI. These findings extend the importance of S. caprae, emphasize its similarities to methicillin-resistant S. aureus, and demonstrate its ability to persist in an intensive care unit setting.     

Antibody responses to protein A in patients with Staphylococcus aureus bacteremia and endocarditis.

To assess the significance of antibody to Staphylococcus aureus protein A (SpA) in human sera, we developed a modified enzyme-linked immunosorbent assay (ELISA). SpA antibody levels in 23 patients with S. aureus endocarditis (IE), 21 patients with non-IE S. aureus bacteremia, and 33 controls were measured. Geometric mean levels of antibody to SpA were significantly higher in S. aureus IE patients (134 ELISA units [EU]) than in uninfected controls (52 EU; P less than 0.01). Also, a significantly greater proportion of S. aureus IE patients (12 of 23) and S. aureus non-IE bacteremia patients (11 of 21) had antibody levels greater than an arbitrary threshold of 100 EU compared with uninfected controls (0 of 23; P less than or equal to 0.001). However, no significant differences in geometric mean SpA antibody levels between the bacteremic patients with and without IE were noted. The sensitivity and specificity of this ELISA to distinguish patients with S. aureus IE from those with non-IE bacteremia were low (52 and 48%, respectively). There was a significant association between SpA antibody levels and either immunoglobulin G or immunoglobulin M teichoic acid antibody levels (r = 0.406, P less than 0.05; r = 0.571, P = 0.002, respectively). For patients from whom multiple sera were available (13 IE and 5 non-IE patients), SpA antibody levels were measured over time and showed a wide temporal variation of immune responses. We conclude that antibody responses to SpA can be measured in many patients with invasive S. aureus disease but that the levels are of insufficient sensitivity or specificity to be of clinical use as a diagnostic or prognostic test.     

Inactivation of Staphylococcus aureus and Enterococcus faecalis by a direct-current,cold atmospheric-pressure air plasma microjet

Objective

A direct-current, cold atmospheric-pressure air plasma microjet (PMJ) was performed to inactivate Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis) in air. The process of sterilization and morphology of bacteria was observed. We wish to know the possible inactivation mechanisms of PMJ and explore a potential application in dental and other temperature sensitive treatment.

Methods

In this study, we employed a direct current, atmospheric pressure, cold air PMJ to inactivate bacterias. Scanning electron microscopy was employed to evaluate the morphology of S. aureus and showed rupture of cell walls after the plasma treatment and Optical emission spectrum (OES) were used to understand the possible inactivation mechanisms of PMJ.

Results

The inactivation rates could reach 100% in 5 min. When the distance between the exit nozzle of the PMJ device and Petri dish was extended from 1 cm to 3 cm, effective inactivation was also observed with a similar inactivation curve.

Conclusion

The inactivation of bacteria is attributed to the abundant reactive oxygen and nitrogen species, as well as ultroviolet radiation in the plasma. Different life spans and defensibilities of these killing agents may hold the key to understanding the different inactivation curves at different treatment distances.