Bacteremia due to Staphylococcus epidermidis: microbiologic, epidemiologic, clinical, and prognostic features

Atomistic simulation on flavonoids derivatives as potential inhibitors of bacterial gyrase of Staphylococcus aureus

The bacterial DNA gyrase is an attractive target to identify the novel antibacterial agents. The flavonoid derivatives possess various biological activities such as antimicrobial, anti-inflammatory and anticancer activities. The aim of present study is to identify the potential molecule from flavonoid derivatives against Staphylococcus aureus using atomistic simulation namely Molecular Docking, Quantum Chemical and Molecular Dynamics. The molecules Cpd58, Cpd65 and Cpd70 are identified as potential molecules through molecular docking approaches by exploring through the N - H…O hydrogen bonding interactions with Asn31 and Glu35 of Gyrase B. To confirm the intramolecular charge transfer in the flavonoid derivatives, Frontier Molecular Orbital (FMO) calculation was performed at M06/6-31g(d) level in gas phase. The lowest HOMO-LUMO gap was calculated for Cpd58, Cpd65 and Cpd70 among the selected compounds used in this study. Molecular dynamics simulation were carried out for Cpd58 and Cpd70 for a time period of 50 ns and found to be stable throughout the analysis. Therefore, the identified compounds are found to be a potent inhibitor for GyrB of S. aureus that can be validated by experimental studies. Communicated by Ramaswamy H. Sarma.

Clinical Behavior of Implant Infections Due to Staphylococcus Epidermidis

Surgical implants and other foreign material are increasingly used in modern medicine to restore or to improve the function of the human body. Infection of an implant is associated with considerable morbidity due to frequent hospitalizations, surgery and antimicrobial treatment. The underlying mechanism is the formation of a bacterial biofilm on the surface of the implanted body. The recognition and diagnosis of implant infections is essential for further therapy and, above all, the decision to remove and exchange the implant.

Methods

We compared the data of 60 patients with implant infections with those of 60 patients with transient bacteremia caused by Staphylococcus epidermidis. The pathogens isolated from blood were characterized with regard to antimicrobial susceptibility and formation of biofilms using a static microtiter plate model. Wild type skin isolates from non-hospitalized healthy volunteers served as control with regard to antimicrobial susceptibility and biofilm formation.

Results

Clinical signs and symptoms, underlying diseases and outcome were not different in either group. However, patients with implant infection had fever over a longer time (mean 12 days versus 3 days, respectively, p & 0.05) and more often positive blood cultures than patients with transient bacteremia (3.1 versus 1.2, p & 0.05). Thrombocytopenia was observed in patients with implant infections but not in patients with transient bacteremia (p & 0.05). Biofilms were formed in 86.4 % of the isolates in implant infection, in 88.8 % in transient bacteremia and in 76.9 % of the isolates from healthy volunteers (not significant). Multi-resistance to penicillin, oxacillin, erythromycin, clindamycin, ciprofloxacin and trimethoprim was more common in the hospital strains than in the wild type strains (75.6 % versus 48.7 %, p & 0.05).

Conclusions

The clinical features of implant infections are indistinguishable from those of transient bacteremia. Persisting fever and multiple blood culture yielding the growth of skin flora bacteria are strong indicators for infection of implanted material. Biofilm formation and antimicrobial multiresistance, as common in implant infection as in transient bacteremia, seem to be accessory factors in infections due to Staphylococcus epidermidis.

Role of Antibiotic Lock Therapy for the Treatment of Catheter-Related Bloodstream Infections

Catheter-related bloodstream infections are often difficult to treat because they are caused by organisms that embed themselves in a bio film layer on the catheter surface, resulting in an increased resistance to antimicrobial agents. Systemic antibiotics are usually administered but, although generally effective in eliminating circulating bacteria, they frequently fail to sterilize the line, leaving the patient at a continuing risk of complications or recurrence. A successful approach to managing these infections requires making an appropriate decision regarding whether the catheter should be removed or retained using antibiotic lock therapy; and choosing the type and duration of antimicrobial therapy based on the type of organism and its resistance pattern. Studies that have evaluated antibiotic lock therapy have varied in the types of antibiotics and concentrations used, the addition of heparin to the solutions, and dwell times in the catheter lumen. Guidelines from the Infectious Diseases Society of America include use of antibiotic lock therapy as a therapeutic option for intraluminal infections when the device is not removed and, although not routine, as prophylaxis for catheter-related infection in select patient populations. However, there are no published guidelines on the concentration of heparin or antibiotics that should be used, and minimal published data on the stability of heparin combinations with antibiotics. It is to be hoped that antibiotic locks will be subject to randomized controlled trials of sufficient power to confirm or refute their use.

Diagnostic Evidence of Staphylococcus Warneri as a Possible Cause of Bovine Abortion

Following a routine necropsy of a bovine fetus aborted at 5 months of gestation, placenta, fetal tissue samples, and stomach contents were subjected to a number of laboratory tests. Staphylococcus warneri was isolated in pure culture from the lung, liver, and stomach contents, whereas the placenta yielded S. warneri and a number of contaminants. Gross evaluation of agar plates showed predominant colonies to be morphologically consistent with those of S. warneri and the identity of the agent was further confirmed on a Trek Diagnostic Systems Sensititre, gram-positive identification (GPID) plate. Microscopic evaluation of fetal tissue sections showed extensive necrotizing lesions of the tongue, lung, and placenta in which there were numerous coccoid shaped gram-positive bacteria with morphology consistent with Staphylococcus spp. These results provide strong diagnostic evidence of S. warneri as a possible cause of bovine abortion and suggest there should be further investigations into the abortivirulence of this agent.

Determining the Clinical Significance of Coagulase-Negative Staphylococci Isolated From Blood Cultures

Background and Objective:

Coagulase-negative staphylococci are both an important cause of nosocomial bloodstream infections and the most common contaminants of blood cultures. Judging the clinical significance of coagulase-negative staphylococci is vital but often difficult and can have a profound impact on an institution's bloodstream infection rates. Our objective was to develop an algorithm to assist in determining the clinical significance of coagulase-negative staphylococci.

Design:

A single experienced reviewer examined the medical records of 960 consecutive patients with positive blood cultures in a tertiary-care referral teaching hospital. Four hundred five of the cultures contained coagulase-negative staphylococci. A determination of clinical significance was made and the performances of various published algorithms that contained readily available clinical and laboratory data were compared.

Results:

Eighty-nine (22%) of the episodes were considered significant, whereas 316 were contaminants. Patients with bacteremia were significantly more likely to be neutropenic and exhibit signs of sepsis syndrome. The algorithm with the best combined sensitivity (62%) and specificity (91%) for determining the clinical significance of coagulase-negative staphylococci was defined as at least two blood cultures positive for coagulase-negative staphylococci within 5 days, or one positive blood culture plus clinical evidence of infection, which includes abnormal white blood cell count and temperature or blood pressure.

Conclusion:

Use of this algorithm could potentially reduce misclassification of nosocomial bloodstream infections and inappropriate use of vancomycin for positive blood cultures likely to represent contamination (Infect Control Hosp Epidemiol2005;26:559-566).

Nosocomial Bacteremia Clinical Significance of a Single Blood Culture Positive for Coagulase-Negative Staphylococci

Objectives:

To describe the epidemiology of nosocomial coagulase-negative staphylococci (CoNS) bacteremia and to evaluate the clinical significance of a single blood culture positive for CoNS.

Design:

A 3-year retrospective cohort study based on data prospectively collected through hospital-wide surveillance. Bacteremia was defined according to CDC criteria, except that a single blood culture growing CoNS was not systematically considered as a contaminant. All clinically significant blood cultures positive for CoNS nosocomial bacteremia were considered for analysis.

Setting:

A large university teaching hospital in Geneva, Switzerland.

Results:

A total of 2,660 positive blood cultures were identified. Of these, 1,108 (41.7%) were nosocomial; CoNS were recovered from 411 nosocomial episodes (37.1%). Two hundred thirty-four episodes of CoNS bacteremia in the presence of signs of sepsis were considered clinically relevant and analyzed. Crude mortality and associated mortality were 24.4% and 12.8%, respectively. Associated mortality was similar among patients with one positive blood culture and those with two or more (16.2% vs 10.8%, respectively;P= .3). Mortality rates after bacteremia for patients with a single positive blood culture and for those with two or more were 15.3% and 7.0%, respectively, at day 14 (RR, 2.2; CI%, 0.87-5.46) and 20.8% and 11.3%, respectively, at day 28 (RR, 1.9; CI95, 0.9-3.8). On multivariate analysis, only age and a rapidly fatal disease were independently associated with death.

Conclusion:

CoNS bacteremia harbor a significant mortality and a single positive blood culture in the presence of signs of sepsis should be considered as clinically relevant.

In silico designing and molecular docking of a potent analog against Staphylococcus aureus porphobilinogen synthase

Background:

The emergence of multidrug-resistant strains of Staphylococcus aureus, there is an urgent need for the development of new antimicrobials which are narrow and pathogen specific.

Aim:

In this context, the present study is aimed to have a control on the staphylococcal infections by targeting the unique and essential enzyme; porphobilinogen synthase (PBGS) catalyzes the condensation of two molecules of δ-aminolevulinic acid, an essential step in the tetrapyrrole biosynthesis. Hence developing therapeutics targeting PBGS will be the promising choice to control and manage the staphylococcal infections. 4,5-dioxovalerate (DV) is known to inhibit PBGS.

Materials and Methods:

In view of this, in this study, novel dioxovalerate derivatives (DVDs) molecules were designed so as to inhibit PBGS, a potential target of S. aureus and their inhibitory activity was predicted using molecular docking studies by molecular operating environment. The 3D model of PBGS was constructed using Chlorobium vibrioform (Protein Data Bank 1W1Z) as a template by homology modeling method.

Results:

The built structure was close to the crystal structure with Z score − 8.97. Molecular docking of DVDs into the S. aureus PBGS active site revealed that they are showing strong interaction forming H-bonds with the active sites of K248 and R217. The ligand–receptor complex of DVD13 showed a best docking score of − 14.4555 kcal/mol among DV and all its analogs while the substrate showed docking score of − 13.0392 kcal/mol showing interactions with S199, K217 indicating that DVD13 can influence structural variations on the enzyme and thereby inhibiting the enzyme.

Conclusion:

The substrate analog DVD13 is showing significant interactions with active site of PBGS and it may be used as a potent inhibitor to control S. aureus infections.

Mortality and hospital stay related to coagulase-negative Staphylococci bacteremia in non-critical patients

OBJECTIVES

To describe the morbidity and mortality related to coagulase-negative Staphylococci (CNS) bacteremia in non-critical patients.

METHODS

Prospective, matched case-control study nested in a cohort. Patients with CNS bacteremia and no other isolate in blood cultures during their admission were defined as cases. Each case was matched by age, sex and area of hospitalization to one control. A 30-day follow-up was performed. Mortality and hospital stay were defined as endpoints.

RESULTS

105 cases and 105 controls were included. All cases carried intravascular catheters at the time of inclusion. Cases presented higher mortality compared to controls (14.3% vs. 4.8%), although this association was not independent in a multivariate analysis (p = 0.11). CNS bacteremia was independently associated with longer hospital stay (mean 12 vs. 8.5 days, p = 0.008). Moreover, when patients with CNS bacteremia were specifically analyzed, the persistence of fever (p = 0.005) and inappropriate empirical treatment (p = 0.04) were independently related to mortality.

CONCLUSION

We did not observe increased mortality attributable to CNS bacteremia, although it was associated with longer hospitalizations. Early appropriate empirical antibiotic therapy pending blood culture results might improve the outcome of patients with CNS bacteremia. Close follow-up is recommended if fever persists beyond 72 h.

High-throughput molecular identification of Staphylococcus spp. isolated from a clean room facility in an environmental monitoring program

BACKGROUND

The staphylococci are one of the most common environmental isolates found in clean room facility. Consequently, isolation followed by comprehensive and accurate identification is an essential step in any environmental monitoring program.

FINDINGS

We have used the API Staph identification kit (bioMérieux, France) which depends on the expression of metabolic activities and or morphological features to identify the Staphylococcus isolates. The API staphylococci showed low sensitivity in the identification of some species, so we performed molecular methods based on PCR based fingerprinting of glyceraldehyde-3-phosphate dehydrogenase encoding gene as useful taxonomic tool for examining Staphylococcus isolates.

CONCLUSIONS

Our results showed that PCR protocol used in this study which depends on genotypic features was relatively accurate, rapid, sensitive and superior in the identification of at least 7 species of Staphylococcus than API Staph which depends on phenotypic features.

Access technique and its problems in parenteral nutrition - Guidelines on Parenteral Nutrition, Chapter 9

Catheter type, access technique, and the catheter position should be selected considering to the anticipated duration of PN aiming at the lowest complication risks (infectious and non-infectious). Long-term (>7-10 days) parenteral nutrition (PN) requires central venous access whereas for PN <3 weeks percutaneously inserted catheters and for PN >3 weeks subcutaneous tunnelled catheters or port systems are appropriate. CVC (central venous catheter) should be flushed with isotonic NaCl solution before and after PN application and during CVC occlusions. Strict indications are required for central venous access placement and the catheter should be removed as soon as possible if not required any more. Blood samples should not to be taken from the CVC. If catheter infection is suspected, peripheral blood-culture samples and culture samples from each catheter lumen should be taken simultaneously. Removal of the CVC should be carried out immediately if there are pronounced signs of local infection at the insertion site and/or clinical suspicion of catheter-induced sepsis. In case PN is indicated for a short period (max. 7-10 days), a peripheral venous access can be used if no hyperosmolar solutions (>800 mosm/L) or solutions with a high titration acidity or alkalinity are used. A peripheral venous catheter (PVC) can remain in situ for as long as it is clinically required unless there are signs of inflammation at the insertion site.

Homologous and heterologous expression and maturation processing of extracellular glutamyl endopeptidase of Staphylococcus epidermidis

The extracellular serine endopeptidase GluSE (EC 3.4.21.19) is considered to be one of the virulence factors of Staphylococcus epidermidis. The present study investigated maturation processing of native GluSE and that heterologously expressed in Escherichia coli. In addition to the 28-kDa mature protease, small amounts of proenzymes with molecular masses of 32, 30, and 29 kDa were identified in the extracellular and cell wall-associated fractions. We defined the pre (M1-A27)- and pro (K28-S66)-segments, and found that processing at the E32-S33 and D48-I49 bonds was responsible for production of the 30- and 29-kDa intermediates, respectively. The full-length form of C-terminally His-tagged GluSE was purified as three proenzymes equivalent to the native ones. These molecules possessing an entire or a part of the pro-segment were proteolytically latent and converted to a mature 28-kDa form by thermolysin cleavage at the S66-V67 bond. Mutation of the essential amino acid S235 suggested auto-proteolytic production of the 30- and 29-kDa intermediates. Furthermore, an undecapeptide (I56-S66) of the truncated pro-segment not only functions as an inhibitor of the protease but also facilitates thermolysin processing. These findings could offer clues to the molecular mechanism involved in the regulation of proteolytic activity of pathogenic proteases secreted from S. epidermidis.

Sources and outcome of bloodstream infections in cancer patients: the role of central venous catheters

Simultaneously drawn quantitative blood cultures are used to diagnose catheter-related bloodstream infections. We conducted this study to determine the frequency with which central venous catheters were the source of bloodstream infections detected through paired positive blood cultures drawn from cancer patients and the potential for quantitative blood cultures to help predict outcome in neutropenic and non-neutropenic patients. From September 1999 to November 2000, we identified 169 patients with bloodstream infections. Of all bloodstream infections, 56% were catheter-related bloodstream infections. Gram-positive bacteremia was found to be catheter-related in 55% and 69% of patients with hematologic malignancy and solid tumors, respectively, whereas gram-negative bacteremia was catheter-related in only 19% of patients with underlying hematologic malignancy and in 60% of patients with solid tumor (P = 0.01). By multivariate analysis, poor response was associated with critical illness and persistent neutropenia (P < 0.01). In neutropenic patients with catheter-related bloodstream infections, peripheral quantitative blood cultures of >or=100 CFU/mL was also associated with poor response (P = 0.05). Central venous catheters were the major source of bloodstream infection, particularly in patients with solid tumors. In addition to critical illness and persistent neutropenia, quantitative blood cultures might be useful in predicting outcomes for neutropenic patients with catheter-related bloodstream infections.

Gram-positive cocci infections in intensive care: guide to antibacterial selection

The incidence of multiresistance in Gram-positive cocci causing infections in critically ill patients admitted to the intensive care unit (ICU) has increased notably in recent years. Thus, therapeutic proposals have been modified according to the emergence of multiresistant cocci and adapted to epidemiological markers of individual infectious processes, geographical variations of these markers, the availability of new antibacterials, and advances in the knowledge of pharmacokinetic and pharmacodynamic aspects of their use. The current management of critically ill patients should consider new therapeutic approaches, such as the "de-escalating strategy", which includes the administration of empirical antibacterials active against multiresistant pathogens followed by directed treatment based on unequivocal data from antibacterial-susceptibility testing. Optimisation of antibacterial treatment should be viewed in the context of the need to determine plasma drug concentrations, pharmacoeconomic considerations and control of drug-related adverse events. Therapeutic proposals should be developed within the framework of the antibacterial policy of each hospital. The present review is focused on the description of the therapeutic strategies for the main infectious processes caused by Gram-positive cocci in severely ill patients admitted to the ICU according to a review of the pertinent literature and the clinical experience of the authors.

Are Antimicrobial-Impregnated Catheters Effective? Replace the Water and Grab Your Washcloth, Because We Have a Baby to Wash

Significant controversy surrounds the usefulness of central venous catheters (CVCs) impregnated with antimicrobial agents (A-CVCs) for the prevention of catheter-related bloodstream infections (CRBSIs). In a recent issue of Clinical Infectious Diseases, we reviewed 11 published trials of A-CVCs versus uncoated CVCs, and we concluded that there is a lack of solid evidence to support a benefit of A-CVCs in reducing the rate of CRBSIs. A response to our review was recently published in Clinical Infectious Diseases. In this response, our colleagues assert that there is a large body of evidence that demonstrates a powerful decrease in the risk of infection, and they conclude that we should not waste precious resources while we perform additional research to confirm what we have already found to be true. Although these authors agree with us on the significant shortcomings of the studies used to support the use of A-CVCs, they dismiss the need for additional trials to demonstrate that the use of A-CVCs does reduce infections. This dismissal, however, cannot be justified, because of the existence of an ongoing, federally supported, multicenter, prospective, placebo-controlled trial, led by our colleagues, that compares the rate of CRBSIs among patients randomized to receive either an A-CVC or a "placebo" uncoated CVC. That our colleagues are leading a trial that assesses the efficacy of A-CVCs versus placebo uncoated CVCs supports our viewpoint that the truth regarding the protective role of A-CVCs has yet to be determined. Because of the significant cost, potential toxicity, and risk of increased antimicrobial resistance associated with the use of A-CVCs, and until the results of the important trial conducted by our colleagues convincingly demonstrate that A-CVCs reduce the rate of clinically significant events (not just catheter colonization), we recommend that the use of A-CVCs be limited to investigational settings.

Effect of hospitalization and antimicrobial therapy on antimicrobial resistance of colonizing Staphylococcus epidermidis

Endogenous infections with multi-resistant S. epidermidis are among the leading causes of nosocomial infections. The effect of hospitalization and antimicrobial therapy on antimicrobial resistance of colonizing staphylococci was determined from swabs of the nose, hand, axilla and groin from 157 patients on one day. Hospitalization for >72 hours, compared with <72 hours, was associated with a higher percentage of isolates resistant to oxacillin (56% versus 19%), gentamicin (40% versus 15%), trimethoprim (36% versus 17%), clindamycin (56% versus 17%), and fusidic acid (20% versus 4%; p < 0.01 for all), but not to rifampicin (6% versus 1%) or fosfomycin (43% versus 34%, p > 0.05 for both). Concurrent antimicrobial therapy resulted in increased resistance to oxacillin (61% versus 28%), gentamicin (43% versus 20%), and clindamycin (60% versus 26%; p < 0.01 for all), but not to trimethoprim (39% versus 23%), fusidic acid (19% versus 9%), rifampicin (6% versus 3%), or fosfomycin (46% versus 38%, p > 0.05 for all). The increase in resistant isolates was not independent, since hospitalization and antimicrobial therapy were correlated (p < 0.001). After adjustment for potential risk factors such as diabetes mellitus, central venous catheters, and hemodialysis, the odds ratio for oxacillin resistance was 2.8-3.6. None of the risk factors showed statistically significant results, except for the presence of neoplastic disease, which had a significant interaction (P=0.035). The within-subgroup odds ratios for patients with and without neoplasm were 4.2 (95% CI, 2.3-5.7) and 2.1 (95% CI, 0.78-3.12), respectively. These results show that hospitalization for more than three days, with or without antimicrobial therapy, and the presence of neoplastic disease are associated with increased antimicrobial resistance in colonizing S. epidermidis.

Mucosa or skin as source of coagulase-negative staphylococcal bacteraemia?

Nosocomial bacteraemia is associated with significant morbidity, mortality, and cost worldwide, and is most commonly caused by coagulase-negative staphylococci (CONS). Establishing the source of CONS bacteraemia is therefore important in the prevention and management of this infection. CONS infections are presumed to originate at the cutaneous sites of central venous catheters (CVCs), a belief that has led to prevention strategies that focus almost exclusively on the skin. However, mucosal colonisation by CONS is well established, suggesting that mucosal sites might be an important source of CONS bacteraemia. We review the published material that evaluates the source(s) of CONS. We included only studies that used a strict definition of CONS bacteraemia, evaluated skin and other potential sources of CONS, and studied the molecular association between CONS blood isolates and their potential sources. Three published reports fulfilled our criteria. In cancer patients with CONS or CONS bacteraemia, most of the colonising strains that had a molecular match with the strain recovered from the blood of the same patient were mucosal isolates; by contrast, no association was seen between CONS blood and skin isolates. Furthermore, in several patient populations evidence was reported of mucosal colonisation by CONS and in several reports experimental and clinical mucosal translocation of CONS with subsequent bacteraemia was documented. Together these data indicate that mucosal sites are an important source of CONS bacteraemia. Clinical strategies for the treatment of patients with a positive blood culture for CONS, the widespread use of antimicrobial-coated CVCs, and maximum barrier protection for CVC insertion should be reassessed, and strategies to decrease mucosal colonisation by CONS should be developed.

Diagnosis and Management of Long-term Central Venous Catheter Infections

The pathogenesis, diagnosis, and management of central venous catheter infections differ between short-term and long-term catheters. This review summarizes available data regarding the diagnosis and management of catheter-related bloodstream infections (CRBSIs) associated with long-term catheters. A review of various diagnostic modalities is provided, including methods of CRBSI diagnosis for catheters that are retained. Management of CRBSIs for long-term catheters is also addressed, with an emphasis on differentiating infections that require catheter removal from those that may allow catheter salvage. Data regarding catheter salvage with use of antibiotic lock therapy are also reviewed.

Molecular typing of coagulase-negative staphylococcal blood and skin culture isolates to differentiate between bacteremia and contamination

In order to determine whether a blood culture positive for coagulase-negative staphylococci (CNS) represents bacteremia or contamination, a prospective study was conducted using molecular typing to analyze CNS blood culture isolates and corresponding CNS skin isolates collected after skin disinfection from 431 subjects. CNS bacteremia was not found in any of the 301 subjects not suspected of having bacteremia. In 130 patients suspected of having bacteremia, the rate of actual CNS bacteremia was 6%. The overall rate of CNS blood culture contamination was 1%. Chart analysis showed good agreement between our microbiological definitions of bacteremia and the clinical definitions previously published. Bacteremia and contamination can be differentiated using pulsed-field gel electrophoresis and molecular typing of CNS isolates obtained from cultures of blood and corresponding skin samples.

Clinical prognostic markers in patients with severe sepsis: a prospective analysis of 139 consecutive cases

OBJECTIVES

To analyze the clinical characteristics and determine predictive factors of mortality in previously healthy individuals suffering from severe sepsis.

METHODS

The study included 139 patients with severe sepsis, admitted to the Department of Medicine over a two years period. Data recorded on admission included demographic information, blood pressure, core temperature, white blood count, hepatic and renal function tests, coagulation factors, blood gases, serum lactic acid levels, simplified acute physiology score (SAPS-II) and Glasgow Coma Scale (GCS).

RESULTS

On admission, 62 patients were hypotensive, 52 had signs of diffuse intravascular coagulation (DIC), 72 had renal and 27 hepatic dysfunction. The overall mortality rate was 27.3%. Twenty-nine patients had septic shock on admission with a mortality rate of 62.07%. Hypoxemia, metabolic acidosis and the presence of DIC were more frequent in non-survivors, who also had significantly higher SAPS-II on admission and days 3 and 7. Independent factors associated with mortality were older age, septic shock, DIC and acute renal failure on admission, as well as SAPS-II at all time points and lactic acid levels on day 7.

CONCLUSIONS

Septic patients with advanced age, septic shock, renal failure, DIC and metabolic acidosis on admission are at increased risk of mortality. The sustained presence of high SAPS-II and lactacidemia one week after admission are also important risk factors of poor outcome.

Do antimicrobial-impregnated central venous catheters prevent catheter-related bloodstream infection?

Controversy surrounds the role of central venous catheters (CVCs) impregnated with antimicrobial agents in the prevention of catheter-related bloodstream infection (CRBSI). We reviewed the current literature to evaluate the efficacy of antimicrobial-impregnated CVCs for preventing CRBSI. Eleven randomized studies published in article form were identified that included a control group that received nonimpregnated CVCs. We evaluated study methodologies, inclusion of key patient characteristics, use of clinically relevant end points, and molecular-relatedness studies. Review of these 11 trials revealed several methodological flaws, including inconsistent definitions of CRBSI, failure to account for confounding variables, suboptimal statistical and epidemiological methods, and rare use of clinically relevant end points. This review also failed to demonstrate any significant clinical benefit associated with the use of antimicrobial-impregnated CVCs for the purpose of reducing CRBSI or improving patient outcomes. More rigorous studies are required to support or refute the hypothesis that antimicrobial-impregnated CVCs reduce the rate of or prevent CRBSI.

Characterization and molecular cloning of a glutamyl endopeptidase from Staphylococcus epidermidis

A novel extracellular endopeptidase, designated GluSE, was purified from Staphylococcus epidermidis ATCC 14990 cultured by the dialysis membrane technique, and the structural gene (gseA) was cloned. GluSE was a 27kDa, glutamic acid-specific protease, and the optimal pH was 8.0. The proteolytic activity was specifically inhibited with diisopropyl fluorophosphate, indicating that it is a serine protease. The gseA encoded a single polypeptide of 282 amino acids with a deduced molecular weight of 30,809, in which the first 19 N-terminal amino acids completely matched the deduced sequence starting at Val-67, suggesting that GluSE is synthesized with a propeptide. The amino acid sequence of GluSE exhibited 50.5% identity to Staphylococcus aureus V8-protease (GluV8). Although GluSE lacks a C-terminal 12 repeats of the PBN/PBZ tripeptide of GluV8, a catalytic triad of His-117, Asp-159 and Ser-235 was conserved in GluSE. Southern hybridization analysis revealed that gseA exists as a single copy on the chromosomal DNA. The finding that production of GluSE was obviously observed in the adherent culture conditions of the dialysis membrane technique, but not in the planktonic culture conditions, strongly suggests that GluSE could be involved in an important etiologic process in S.epidermidis infection leading to multiple tissue damages.

Effect of an evidence-based hand washing policy on hand washing rates and false-positive coagulase negative staphylococcus blood and cerebrospinal fluid culture rates in a level III NICU

OBJECTIVE

To determine the effect of implementing an evidence-based hand washing policy on between-patient hand washing compliance and on blood and cerebrospinal fluid (CSF) culture rates in a level III neonatal intensive care unit (NICU).

METHODS

An evidence-based hand washing policy, supported by an intensive education program, was introduced in a regional NICU. A total of 2009 preintervention neonates (16,168 patient days) over 17 months were compared to 676 postintervention neonates (5779 patient days) over 6 months. Hand washing compliance and rates of blood and CSF cultures yielding coagulase negative staphylococci (CONS) were compared before and after intervention.

RESULTS

Compliance with appropriate between-patient hand washing improved (from 47.4% to 85.4%, p=0.001) after the hand washing policy was introduced. The rate of cultures positive for CONS declined from 6.1+/-2.3 to 3.2+/-1.6 per 1000 patient days (p=0.005). Most of this reduction was attributable to a reduction in false-positive cultures, from 4.2+/-2.4 to 1.9+/-1.8 per 1000 patient days (p=0.042), but there was a trend toward decreased true-positive cultures (from 2.1+/-1.2 to 1.2+/-1.0 per 1000 patient days, p=0.074) as well. Potential confounders and demographics factors were similar between the control and intervention subjects.

CONCLUSION

Implementation of an evidence-based hand washing policy resulted in a significant increase in hand washing compliance and a significant decrease in false-positive coagulase negative staphylococcal blood and CSF culture rates. Exploratory data analysis revealed a possible effect on true-positive coagulase negative staphylococcal blood and CSF culture rates, but these results need to be confirmed in future studies.

Clinical and epidemiologic significance of coagulase-negative staphylococci bacteremia in a tertiary care university Israeli hospital

OBJECTIVES

To characterize the clinical significance of coagulase-negative staphylococci (CNS) bacteremia.

DESIGN

Prospective cohort study.

SETTING

A 900-bed hospital in Haifa, Israel, from November 1996 to March 1997.

RESULTS

Of 137 episodes of positive blood cultures for CNS, 41 (30%) were considered as true infection. Twenty-seven of 119 episodes associated with only 1 blood culture positive for CNS (23%) met the definition of infection as compared with 14 of 18 episodes (78%) associated with 2 or more blood cultures positive for CNS (P <.001). Methicillin resistance was significantly more frequent among Staphylococcus epidermidis isolates of episodes of true bacteremia than of episodes of contamination (15 of 22 [68%] vs. 11 of 33 [33%], respectively; P =.02). S hominis was isolated only in episodes considered as contamination (P =.01). It was estimated that CNS represents 24% of all nosocomial bloodstream pathogens. When CNS were isolated in the first 48 hours of hospitalization, an intravascular device was more frequently associated with episodes of true bacteremia than in those considered as contamination (7 of 7 [100%] vs. 10 of 57 [18%], respectively; P <.001). The mortality rate among patients with true CNS bacteremia was 16%.

CONCLUSION

Some laboratory parameters may help identify episodes of true CNS bacteremia, which appears to be more common than previously considered.

Possible virulence factors of Staphylococcus sciuri

Staphylococcus sciuri is an opportunistic pathogen of controversial clinical significance. The factors that contribute to colonization and/or infection caused by this bacterium have not been studied intensively so far. The present research was carried out in order to study the presence of potential virulence factors in 121 human and animal isolates of this bacterium. Isolates were examined for biofilm formation, hemagglutination, presence of clumping factor, production of spreading factors and exotoxins, cytotoxicity and capacity to stimulate nitric oxide production. The results showed that S. sciuri is highly capable of biofilm production, that it displays strong proteolytic and DNase activities, produces hemolysins and stimulates nitric oxide production by rat macrophages. Although the present study showed existence of a wide spectrum of possible virulence determinants of S. sciuri, their exact contribution to virulence of this bacterium in vivo remains to be determined.

Glyceraldehyde-3-phosphate dehydrogenase-encoding gene as a useful taxonomic tool for Staphylococcus spp

The gap gene of Staphylococcus aureus, encoding glyceraldehyde-3-phosphate dehydrogenase, was used as a target to amplify a 933-bp DNA fragment by PCR with a pair of primers 26 and 25 nucleotides in length. PCR products, detected by agarose gel electrophoresis, were also amplified from 12 Staphylococcus spp. analyzed previously. Hybridization with an internal 279-bp DNA fragment probe was positive in all PCR-positive samples. No PCR products were amplified when other gram-positive and gram-negative bacterial genera were analyzed using the same pair of primers. AluI digestion of PCR-generated products gave 12 different restriction fragment length polymorphism (RFLP) patterns, one for each species analyzed. However, we could detect two intraspecies RFLP patterns in Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus simulans which were different from the other species. An identical RFLP pattern was observed for 112 S. aureus isolates from humans, cows, and sheep. The sensitivity of the PCR assays was very high, with a detection limit for S. aureus cells of 20 CFU when cells were suspended in saline. PCR amplification of the gap gene has the potential for rapid identification of at least 12 species belonging to the genus Staphylococcus, as it is highly specific.

Problems and solutions in hospital-acquired bacteraemia

Despite infection control efforts, bacteraemia remains one of the most frequent and challenging hospital-acquired infections and is associated with high attributable morbidity and mortality and additional use of healthcare resources. Prevention and control of hospital-acquired blood-stream infection requires improved detection methods, better definition of patient populations at risk, more refined guidelines for the interpretation of positive blood cultures and a better discrimination between sporadic contaminants and true bacteraemia. These issues are addressed in the current review together with those related to the diagnosis, management and recent advances in the prevention of cathether-related bacteraemia, the leading cause of hospital-acquired blood-stream infection. Finally, the reasons and perspectives for blood-stream infection surveillance are briefly discussed.

Vaccine potential of poly-1-6 beta-D-N-succinylglucosamine, an immunoprotective surface polysaccharide of Staphylococcus aureus and Staphylococcus epidermidis

Staphylococcus aureus and S. epidermidis are among the most common causes of nosocomial infection, and S. aureus is also of major concern to human health due to its occurrence in community-acquired infections. These staphylococcal species are also major pathogens for domesticated animals. We have previously identified poly-N-succinyl beta-1-6 glucosamine (PNSG) as the chemical form of the S. epidermidis capsular polysaccharide/adhesin (PS/A) which mediates adherence of coagulase-negative staphylococci (CoNS) to biomaterials, serves as the capsule for strains of CoNS that express PS/A, and is a target for protective antibodies. We have recently found that PNSG is made by S. aureus as well, where it is an environmentally regulated, in vivo-expressed surface polysaccharide and similarly serves as a target for protective immunity. Only a minority of fresh human clinical isolates of S. aureus elaborate PNSG in vitro but most could be induced to do so under specific in vitro growth conditions. However, by immunofluorescence microscopy, S. aureus cells in infected human sputa and lung elaborated PNSG. The ica genes, previously shown to encode proteins in CoNS that synthesize PNSG, were found by PCR in all S. aureus strains examined, and immunogenic and protective PNSG could be isolated from S. aureus. Active and passive immunization of mice with PNSG protected them against metastatic kidney infections after intravenous inoculation with eight phenotypically PNSG-negative S. aureus. Isolates recovered from kidneys expressed PNSG, but expression was lost with in vitro culture. Strong antibody responses to PNSG were elicited in S. aureus infected mice, and a PNSG-capsule was observed by electron microscopy on isolates directly plated from infected kidneys. PNSG represents a previously unidentified surface polysaccharide of S. aureus that is elaborated during human and animal infection and is a prominent target for protective antibodies.

Nosocomial bloodstream infections: organisms, risk factors, and implications

In the last 30 years, the frequency, etiology, and epidemiology of bloodstream infections (BSIs) have changed with the evolution of medical care, particularly among the increasing number of hospitalized patients who require intensive care. Although gram-negative bacilli were the predominant nosocomial pathogens in the 1970s, gram-positive cocci have emerged as a more frequent cause of nosocomial BSIs during the 1980s and 1990s. Many gram-positive cocci associated with nosocomial BSIs are now resistant to commonly used antibiotics. Currently, the 3 most common causes of nosocomial BSIs in the United States are coagulase-negative staphylococci, Staphylococcus aureus, and enterococci. The emergence of vancomycin-resistant staphylococcal infections is of particular concern. In addition, the incidence of methicillin-resistant S. aureus (MRSA) infections appears to be increasing; however, the effect of MRSA infection on mortality in hospitalized patients remains unclear. Therefore, newer, more effective antimicrobial therapies are needed to treat BSIs caused by gram-positive cocci are needed.

Antimicrobial resistance of coagulase-negative staphylococci from a Kuwait hospital

This study investigated the incidence of antimicrobial resistance in clinically significant coagulase-negative staphylococci at the Mubarak Al Kabeer Hospital, Kuwait. A total of 104 isolates of coagulase-negative staphylococci consisting of S. epidermidis (67), S. haemolyticus (16), S. saprophyticus (6), S. simulans (2), S. hominis (4), S. albus (2), S. sciuri (3), S. warneri (2), S. capitis (1), and S. xylosus (1) were isolated from clinical specimens over a 6-7 month period and tested for resistance to 22 antibacterial agents and the ability to produce slime. They were all susceptible to vancomycin and mupirocin but intermediate resistance to teicoplanin was detected in seven isolates: 83 and 47.7% were resistant to penicillin G and methicillin, respectively, 57% were resistant to gentamicin, 49.5% to erythromycin, 50.4% to tetracycline, and 52.3% to trimethoprim. Resistance to heavy metals and the nucleic-acid binding compound was also detected. More than half of S. epidermidis, S. saprophyticus, S. simulans, S. hominis, and all of S. haemolyticus were multiply resistant to three or more groups of antibiotics and there was a significant association between slime production and resistance to multiple antimicrobial agents in S. epidermidis. The results revealed a high level of resistance to commonly used agents.

Epidemiological and biological characteristics of methicillin-resistant staphylococcal infections in a Mexican hospital

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has spread worldwide since 1960. However, there is little information concerning methicillin-resistant coagulase-negative staphylococci (MRCNS) infections.

METHODS

In order to study the clinical and epidemiological characteristics of methicillin-resistant staphylococci (MRS) infections and to determine the relationship between MRS and both synergistic hemolysis (SH) and slime production (SP), a laboratory-based survey and non-matched case-control study were carried out at a tertiary-care center in Mexico City. In regard to patients, from May 1991 to October 1992, 46 cases of MRS infection and 86 patients (controls) infected by methicillin-susceptible staphylococci (MSS) were included. Clinical and epidemiologic variables were analyzed. The isolates were identified and tested for antimicrobial susceptibility by standard methods. An MIC of oxacillin > or = 8 micrograms/mL was defined as an MRS.

RESULTS

During the study, 94 nosocomial staphylococcal infections were diagnosed: S. aureus, 35 and CNS, 59; 43 (45.7%) by MRS (rate of MRS infections was 1.12 per 100 in-patients); 2 MRSA; 41 MRCNS, and only 19 were symptomatic. Three infections were community-acquired, including one MRSA and two MRCNS. After multivariate analysis, the significant risk factors were previous antimicrobial therapy (p = 0.013) and catheter-related (p = 0.009) and urinary-tract source (p = 0.0001). Forty-nine percent of MRS showed SH while only 15% of MSS (p < 0.001) showed SH, especially in 10/10 MR-S. hemolyticus. Additionally, 48% of MRCNS showed SP, as did 18% of MSCNS (p = 0.019), particularly in 15/20 MR-S. epidermidis. Of all MRS isolates, 38% showed a homogeneous phenotype, a trait associated with multi-drug resistance (p < 0.01) and SH (p < 0.001).

CONCLUSIONS

CNS predominated as the cause of MRS infections in our setting. The homogenous phenotype was associated with SH and multi-drug resistance.

An inflammatory polypeptide complex from Staphylococcus epidermidis: isolation and characterization

Staphylococcus epidermidis releases factors that activate the HIV-1 long terminal repeat, induce cytokine release, and activate nuclear factor B in cells of macrophage lineage. The active material had a mass of 34,500 daltons, was inactivated by proteases and partitioned into the phenol layer on hot aqueous phenol extraction, and thus was termed phenol-soluble modulin (PSM). High performance liquid chromatography (HPLC) of crude PSM yielded two peaks of activity designated PSM peak 1 and peak 2. MALDI-TOF (matrix-assisted laser desorption ionization-time of flight) mass spectroscopy indicated the presence of two components in peak 1, which were designated PSM and PSM. Peak 2 contained a single component, designated PSM. Separation of PSM and PSM in peak 1 could be achieved by a second HPLC procedure. The structure of each component was determined by amino acid sequence analysis and identification and sequencing of their genes. PSM, PSM, and PSM were 22-, 44-, and 25-amino acid, respectively, strongly hydrophobic polypeptides. PSM was identified as Staphylococcus epidermidis delta toxin, whereas PSM and PSM exhibited more distant homology to previously described staphylococcal toxins. They appeared to exist as a complex or aggregate with activity greater than the component parts. The properties of the S. epidermidis PSMs suggest that they may contribute to the systemic manifestations of Gram-positive sepsis.

Rapid identification and typing of Staphylococcus aureus by PCR-restriction fragment length polymorphism analysis of the aroA gene

The Staphylococcus aureus aroA gene, which encodes 5-enolpyruvylshikimate-3-phosphate synthase, was used as a target for the amplification of a 1,153-bp DNA fragment by PCR with a pair of primers of 24 and 19 nucleotides. The PCR products, which were detected by agarose gel electrophoresis, were amplified from all S. aureus strains so far analyzed (reference strains and isolates from cows and sheep with mastitis, as well as 59 isolates from humans involved in four confirmed outbreaks). Hybridization with an internal 536-bp DNA fragment probe was positive for all PCR-positive samples. No PCR products were amplified when other Staphylococcus spp. or genera were analyzed by using the same pair of primers. The detection limit for S. aureus cells was 20 CFU when the cells were suspended in saline; however, the sensitivity of the PCR was lower (5 x 10(2) CFU) when S. aureus cells were suspended in sterilized whole milk. TaqI digestion of the PCR-generated products rendered two different restriction fragment length polymorphism patterns with the cow and sheep strains tested, and these patterns corresponded to the two different patterns obtained by antibiotic susceptibility tests. Analysis of the 59 human isolates by our easy and rapid protocol rendered results similar to those of other assays.

Central venous catheter-related bacteraemia in critically ill neonates: risk factors and impact of a prevention programme

Risk factors for central venous catheter (CVC)-related bacteraemia among infants admitted to a neonatal intensive care unit (NICU) were analysed and the impact of surveillance and continuing education on the incidence of this complication investigated. Among patients admitted to a NICU, CVC-related bacteraemia increased from 1/15 (7%) in 1987 to 11/26 (42%) in 1988 (P = 0.01). Coagulase-negative staphylococci isolated from bacteraemia patients showed clonal diversity by plasmid and chromosomal fingerprinting. A review of CVC care procedures suggested breaches in aseptic techniques. Catheter-care technique was revised to ensure maximal aseptic precautions, including the use of sterile gloves, gown and drapes. The new policy was promoted by a continuing education programme and regular feed-back of CVC-related bacteraemia incidence to NICU staff. In the four-year follow-up period, the attack-rate of CVC-related bacteraemia decreased to 18/156 (12%) patients [relative risk (RR): 0.27, 95% confidence interval (CI); 0.15-0.51; P < 0.001 vs the previous period]. By using the Cox's model proportional hazards, very low birthweight and the period before use of strict aseptic CVC care were found to be predictors of increased risk of catheter-related bacteraemia after adjustment for duration of catheterization. These data provide further evidence that strict aseptic precautions during the maintenance and utilization of CVC can contribute to lower the risk of catheter infection in critically ill neonates. Regular feedback of surveillance data was associated with a progressive decrease in incidence of infection, suggesting that it improved staff compliance with aseptic precautions.

Blood cultures positive for coagulase-negative staphylococci: antisepsis, pseudobacteremia, and therapy of patients

A blood culture cohort study investigating issues related to isolation of coagulase-negative staphylococci (CoNS) and other skin microflora is reported. Data were collected over 12 weeks to determine the incidence of significant CoNS bacteremia versus that of pseudobacteremia (contaminants) and to evaluate drug therapy in patients with cultures positive for CoNS. In addition, the effectiveness of 0.2% chlorine peroxide as a bactericidal disinfectant was compared to that of 10% providone iodine. A total of 3,276 cultures of blood from 1,433 patients were evaluated in the study. Eighty-nine cultures were positive for skin flora, with 81 of 89 (91%) involving CoNS. The incidence of significant CoNS bacteremia was 20 of 81 (24.7%), that of indeterminate bacteremia was 10 of 81 (12.3%), and that of contamination was 59 of 81 (72.8%). The incidence of significant bacteremia involving CoNS was double the 10 to 12% rate based on previous estimations at our institutions. In tests with the two bactericidal disinfectants, 22 of 1,639 cultures (1.3%) in the chlorine peroxide group versus 37 of 1,637 (2.3%) in the providone iodine group were considered contaminated (P = 0.065). Rates of contamination for venipuncture versus catheter collection were not significantly different (P = 0.46). The overall contamination rate was 59 of 3,276 (1.8%), which is consistent with the lower end of published quality assurance benchmark standards. The low rate was believed to be due to the professional phlebotomy staff in our institutions. There was excellent agreement between retrospective analysis by reviewers, when formal criteria were used, and the attending physicians' intuitive clinical impressions in the classification of significant bloodstream infections (100% agreement) or contamination (95% agreement). However, physicians still used antimicrobial agents to treat nearly one-half of the patients with contaminated blood cultures, with vancomycin being misused in 34% of patients. In addition, 10% of patients with significant bacteremia were treated with inappropriate agents. There were no significant adverse events or prolonged hospital stays due to the unnecessary use of vancomycin; however, the additional costs of treating patients whose cultures contained CoNS contaminants was estimated to be $1,000 per patient. Measures to limit the unnecessary use of vancomycin (and other agents) are important.

Clinical implications of nosocomial gram-positive bacteremia and superimposed antimicrobial resistance

The coexistence of a pathogen population with an ever-increasing resistance to many antibiotics and a patient population characterized by increasingly complex clinical problems has contributed to an increase in the bloodstream infections associated with gram-positive bacteria. This serious therapeutic challenge has already been associated with an increase in infection-related morbidity and mortality, a prolongation of hospital stays, and an escalation of healthcare costs. Vancomycin resistance, long prevalent among the enterococci, has emerged in strains of Staphylococcus aureus. Several cases of infection caused by S. aureus strains with intermediate-level resistance to vancomycin (MIC=8 microg/mL) have recently been reported. As glycopeptide resistance accelerates among the gram-positive bacteria, so does the potential for adverse clinical consequences associated with bloodstream infections caused by these pathogens. The patients least able to tolerate the effects of uncontrolled bloodstream infections are also those at the highest risk for the development of infections caused by glycopeptide-resistant pathogens. In this at-risk population, a poor outcome may be anticipated if effective antibiotic therapy is unavailable. Appropriate rationing of vancomycin and other antimicrobial agents that increase the selection of antibiotic-resistant strains of gram-positive bacteria and the rapid development of novel antimicrobial agents with reliable gram-positive activity must be immediate priorities if the threat posed by glycopeptide-resistant gram-positive pathogens is to be countered.

Species-specific and ubiquitous-DNA-based assays for rapid identification of Staphylococcus aureus

Staphylococcus aureus is the cause of serious infections in humans, including endocarditis, deep-seated abscesses, and bacteremia, which lead to toxic and septic shock syndromes. Rapid and direct identification of this bacterium specifically and ubiquitously directly from clinical specimens would be useful in improving the diagnosis of S. aureus infections in the clinical microbiology laboratory. A wide variety of kits based on biochemical characteristics efficiently identify S. aureus, but the rapidity and the accuracy of each of these methods combined with testing of clinically relevant antibiotic resistance genes need to be improved. On the basis of hybridization assays with randomly selected clones from an S. aureus genomic library, we have identified a chromosomal DNA fragment which is specific for S. aureus and which detected all 82 S. aureus isolates tested. This 442-bp fragment was sequenced and was used to design a set of PCR amplification primers. The PCR assay was also specific and ubiquitous for the identification from bacterial cultures of 195 clinical strains of S. aureus isolated from a variety of anatomical sites and obtained from hospitals throughout the world. The PCR assay that we have developed is simple and can be performed in about 1 h. This DNA-based test provides a novel diagnostic tool for the diagnosis of S. aureus infections.

Positive blood cultures for coagulase-negative staphylococci in neonates: does highly selective vancomycin usage affect outcome?

The implication of highly-selective vancomycin usage on the outcome for infants with positive blood cultures for coagulase-negative staphylococci (CONS) was assessed retrospectively. The analysis was performed on partly prospective collected data from infants under 3 months of age with a least one CONS-positive blood culture in the neonatal intensive care unit at the Soroka University Medical Center between 1990 and 1996. During the study period, 239 episodes of CONS-positive blood cultures were identified from among 64,226 live births (3.7 per 1,000). Vancomycin was administered in 22 (9%) episodes, in all cases only after identification of the bacteria. The remaining 217 episodes were managed either without antibiotics or with continuation or initiation of empiric antibiotic therapy (usually ceftazidime +/- ampicillin) for suspected sepsis. Severity of the initial illness, subsequent morbidity and mortality were low regardless of the treatment administered. Only a single case of a blood-borne vancomycin resistant gram-positive organism was observed during the study period. The approach to CONS-positive blood cultures in neonates used here was associated with low morbidity and mortality. These findings support a policy of highly selective vancomycin usage in an era of emerging vancomycin resistance.

Septic shock as a predictor of mortality in bacteremia caused by coagulase-negative staphylococci

Fifty episodes of bacteremia caused by coagulase-negative staphylococci at Hacettepe University Hospital over a five-year period were reviewed to evaluate the factors influencing the prognosis. Overall mortality and mortality due to bacteremia were 36% and 24%, respectively. Septic shock was determined to be the only factor adversely influencing mortality in both univariate and multivariate analyses. Age, sex, duration of hospitalization, origin of infection, underlying disease, presence of central intravascular or urinary catheters, and prior antibiotic therapy were not statistically significant parameters in predicting septic shock.

The clinical significance of positive blood cultures in the 1990s: a prospective comprehensive evaluation of the microbiology, epidemiology, and outcome of bacteremia and fungemia in adults

To assess changes since the mid-1970s, we reviewed 843 episodes of positive blood cultures in 707 patients with septicemia. The five most common pathogens were Staphylococcus aureus, Escherichia coli, coagulase-negative staphylococci (CNS), Klebsiella pneumoniae, and Enterococcus species. Although CNS were isolated most often, only 12.4% were clinically significant. Half of all episodes were nosocomial, and a quarter had no recognized source. Leading identifiable sources included intravenous catheters, the respiratory and genitourinary tracts, and intraabdominal foci. Septicemia-associated mortality was 17.5%. Patients who received appropriate antimicrobial therapy throughout the course of infection had the lowest mortality (13.3%). Multivariate analysis showed that age (relative risk [RR], 1.80), microorganism (RR, 2.27), source of infection (RR, 2.86), predisposing factors (RR, 1.98), blood pressure (RR, 2.29), body temperature (RR, 2.04), and therapy (RR, 2.72) independently influenced outcome. Bloodstream infections in the 1990s are notable for the increased importance of CNS as both contaminants and pathogens, the proportionate increase in fungi and decrease in anaerobes as pathogens, the emergence of Mycobacterium avium complex as an important cause of bacteremia in patients with advanced human immunodeficiency virus infection, and the reduction in mortality associated with infection.

Coagulase-negative staphylococci isolated from two cases of toxic shock syndrome lack superantigenic activity, but induce cytokine production

Two strains of Staphylococcus epidermidis isolated from patients with toxic shock symptoms have been reported to carry genes related to S. aureus enterotoxins B and C by dot-blot hybridisation, although the corresponding superantigenic toxins were not detected immunologically. We here show that these strains produce no superantigens capable of stimulating proliferation of human mononuclear leukocytes or rabbit splenocytes, and that no DNA homologous to the seb or sec genes can be detected by PCR. However, stimulation of human monocytes by whole killed bacteria induced dose-dependent production of the cytokines TNF alpha, IL-1 beta and IL-6, which may be responsible for the clinical symptoms in these patients.

Bacteria/blood/material interactions. I. Injected and preseeded slime-forming Staphylococcus epidermidis in flowing blood with biomaterials

Blood-material interactions were studied using in vitro recirculation with human blood, slime-forming Staphylococcus epidermidis, and cardiovascular materials. Staphylococcus epidermidis, under preseeded or injected conditions, adhered to nonsmooth materials and elevated plasma levels of fibrinopeptide A (FpA) and C3a in the presence of all materials. Increased white blood cell (WBC) and platelet adhesion and thrombospondin and platelet factor 4 (PF4) release were noted for respective materials in the presence of injected bacteria. Materials that adhered significant quantities of injected S. epidermidis exhibited low levels of adsorbed proteins. Materials with high levels of preseeded S. epidermidis showed high levels of adsorbed proteins. Adhesion of preseeded bacteria and blood plasma elevations of C3a and FpA were lowest on semicrystalline polymer substrates, intermediate on halogenated substrates, and highest on amorphous substrates. In the presence of injected bacteria, WBCs and platelets adhered at earlier recirculation times to amorphous substrates than to semicrystalline substrates.