Increase in native valve endocarditis caused by coagulase negative staphylococci: an Anglo-French clinical and microbiological study.

Native valve endocarditis caused by coagulase negative staphylococci has become more common. A study of 35 cases showed that the infections were usually acquired in the community and occurred in men (mean age 51 years). A pre-existing cardiac abnormality (mitral leaflet prolapse in a third of patients) was detected in 26 (74%). The source of the organisms in the community acquired infections was assumed to be the skin, though lesions were seldom demonstrated; most hospital acquired infections resulted from intravenous devices. Community acquired organisms were usually sensitive to penicillin, whereas those acquired in hospital were often multiresistant. Most infections were caused by Staphylococcus epidermidis. The frequency of acute presentation (26%) and of major neurological abnormality (23%), together with the need for valve replacement (often emergency) (51%) and the mortality (36%) suggest that coagulase negative staphylococci can be virulent aggressive pathogens, mimicking Staphylococcus aureus.     

Increase in native valve endocarditis caused by coagulase negative staphylococci: an Anglo-French clinical and microbiological study

Native valve endocarditis caused by coagulase negative staphylococci has become more common. A study of 35 cases showed that the infections were usually acquired in the community and occurred in men (mean age 51 years). A pre-existing cardiac abnormality (mitral leaflet prolapse in a third of patients) was detected in 26 (74%). The source of the organisms in the community acquired infections was assumed to be the skin, though lesions were seldom demonstrated; most hospital acquired infections resulted from intravenous devices. Community acquired organisms were usually sensitive to penicillin, whereas those acquired in hospital were often multiresistant. Most infections were caused by Staphylococcus epidermidis. The frequency of acute presentation (26%) and of major neurological abnormality (23%), together with the need for valve replacement (often emergency) (51%) and the mortality (36%) suggest that coagulase negative staphylococci can be virulent aggressive pathogens, mimicking Staphylococcus aureus.     

Management of common bacterial infections of the skin

PURPOSE OF REVIEW: Bacterial skin infections commonly encountered in the community include impetigo, folliculitis/furunculosis, simple abscesses, erysipelas and other nonnecrotizing cellulitis. The review focuses on recent epidemiological, bacteriological and therapeutic advances. RECENT FINDINGS: Impetigo and erysipelas occur in about 20 and 1 person/1000/year, respectively. Main risk factors for erysipelas are toe-web intertrigo and lymphedema. The true incidence of furunculosis is unknown, whereas outbreaks in small communities are reported worldwide. Staphylococcus aureus is the predominant pathogen for impetigo and furunculosis, and methicillin-resistant strains play a growing role in both diseases. Erysipelas are mainly caused by streptococci, whereas local complications (i.e. abscesses or blisters) may be due to staphylococci, including methicillin-resistant strains in involved geographic areas. Recent trends for treating impetigo and furunculosis predate community-acquired methicillin-resistant S. aureus. For outbreaks of furunculosis, stringent decolonization measures are showing promise, whereas there is no validated therapeutic regimen for chronic furunculosis. Current trends for erysipelas involve ambulatory treatments and reduced duration of antibiotics. SUMMARY: Despite better epidemiological or bacteriological knowledge of common bacterial skin infections, the exact role of methicillin-resistant staphylococci needs regular surveys in involved geographic areas. Antibiotic treatment must be active on staphylococci and, to a lesser degree, on streptococci.     

Staphylococcal infections in the intensive care unit

Staphylococcus aureus and coagulase-negative staphylococci are among the most common causes of nosocomial infections in the intensive care unit (ICU). The clinical presentation of staphylococcal device-related infections, pneumonias, or surgical wound infections is not unique. However, treatment of these infections is increasingly problematic because of the resistance of clinical isolates to a widening number of antimicrobial agents.The confluence of critically ill patients and the need for multiple invasive procedures, as well as the use of broad-spectrum antimicrobial agents in the ICU, set the stage for the emergence of these multidrug-resistant staphylococci. In the past 10 years, there has been a progressive increase in the overall resistance of staphylococci to antimicrobial agents. Conventional infection control measures, such as handwashing and isolation precautions, to prevent the spread of staphylococcal infections in the ICU setting remain of critical importance. New approaches, including the prophylactic use of topical antistaphylococcal agents to eliminate nasal colonization in high-risk ICU patients and the development of antistaphylococcal vaccines, are currently being investigated.     

Staphylococcal resistance revisited: community-acquired methicillin resistant Staphylococcus aureus--an emerging problem for the management of skin and soft tissue infections

PURPOSE OF REVIEW: In the community non-localized or deep staphylococcal skin and soft tissue infections are typically managed with beta-lactamase stable penicillins. The aims of this review are (1) to evaluate the evidence for the emergence of new strains of community-acquired methicillin resistant Staphylococcus aureus (MRSA), (2) to identify the reasons for their significant association with cutaneous infections, and (3) to consider how they arose and how big a threat they pose to the management of such infections outside hospitals. RECENT FINDINGS: MRSA are emerging as significant community pathogens, especially in previously healthy children with no recognizable risk factors, and are predominantly associated with skin and soft tissue infections (especially abscesses and cellulitis). When present, risk factors are generally similar to those for infection with methicillin susceptible S. aureus. The MRSA isolates associated with such infections may not be entirely 'new', but could represent the displacement of some hospital clones (e.g. EMRSA-15 or variants thereof) to the community as well as the de-novo generation of novel MRSA clones by multiple horizontal transmissions of the mecA gene into methicillin susceptible S. aureus with different genetic backgrounds, some of which are already circulating globally. Community-acquired MRSA from diverse locations are non multiresistant and almost always contain the novel type IV SCCmec commonly found in coagulase-negative staphylococci, but also in hospital-associated gentamicin susceptible MRSA from France, the paediatric clone and in EMRSA-15. SUMMARY: More local data on CA-MRSA infections are needed so that dermatologists and community physicians can assess the risk of such infections amongst their patients and avoid the inappropriate administration of beta-lactams. No simple change in prescribing practices will entirely alleviate selective pressure for the spread of community-acquired MRSA and not exacerbate resistance in pyogenic streptococci, commonly found together with S. aureus in skin and soft tissue infections. The importance of hygiene in preventing the spread of community-acquired MRSA in the community must be reemphasized.     

Influence of subinhibitory concentrations of antibiotics on virulence of staphylococci

The understanding and control of infections caused by staphylococci are still far from complete, and staphylococcal infections continue to be a serious problem. The organisms possess numerous virulence factors that can act independently to induce various symptoms and lesions. Chemotherapy has changed the clinical spectrum of staphylococci but has not eradicated serious staphylococcal infections. An evaluation of the interaction of antibiotics, staphylococci, and host defense will help to identify those factors that determine the success or failure of therapy for staphylococcal infections. The activity of antibiotics is usually expressed in terms of concentrations that either inhibit or kill microorganisms in vitro or in experimental infections. Subinhibitory concentrations of antibiotics may induce changes in bacterial properties both in vitro and in vivo. An understanding of the mechanism of such changes would allow a more rational application of antibiotics that have both specific antistaphylococcal action and positive effects on host defense mechanisms.     

Nosocomial bloodstream infections in United States hospitals: a three-year analysis.

Nosocomial bloodstream infections are important causes of morbidity and mortality. In this study, concurrent surveillance for nosocomial bloodstream infections at 49 hospitals over a 3-year period detected >10,000 infections. Gram-positive organisms accounted for 64% of cases, gram-negative organisms accounted for 27%, and 8% were caused by fungi. The most common organisms were coagulase-negative staphylococci (32%), Staphylococcus aureus (16%), and enterococci (11%). Enterobacter, Serratia, coagulase-negative staphylococci, and Candida were more likely to cause infections in patients in critical care units. In patients with neutropenia, viridans streptococci were significantly more common. Coagulase-negative staphylococci were the most common pathogens on all clinical services except obstetrics, where Escherichia coli was most common. Methicillin resistance was detected in 29% of S. aureus isolates and 80% of coagulase-negative staphylococci. Vancomycin resistance in enterococci was species-dependent--3% of Enterococcus faecalis strains and 50% of Enterococcus faecium isolates displayed resistance. These data may allow clinicians to better target empirical therapy for hospital-acquired cases of bacteremia.     

Long term trends in the occurrence of nosocomial blood stream infection.

OBJECTIVE: To determine trends in the occurrence of nosocomial blood stream infection at the University of Alberta Hospital. METHODS: A prospective survey of nosocomial blood stream infection was conducted; cases from August 1986 to December 1996 were reviewed. Cases were detected by a review of positive blood cultures reported by the microbiology laboratory. Centers for Disease Control and Prevention definitions of nosocomial infection were used to categorize isolates as nosocomial, community acquired or contaminant. RESULTS: There were 2389 cases; primary bacteremia was the most common source (57%), followed by urinary tract, respiratory tract and surgical site sources (10% each). The nosocomial blood steam infection rate rose progressively from 6.0/1000 admissions and 4.59/10,000 patient days in 1986 to 11.2/1000 admissions and 14.31/10,000 days in 1996 (P<0.01); 48% of the total increase in rate occurred between 1995 and 1996. Significant increases occurred between 1986 and 1996 in primary infections (from 3.2 to 7.5/1000 admissions, P<0.01) and infections from all secondary sources (from 2.5 to 3.8/1000 admissions, P=0.01). Coagulase-negative staphylococci (27%), Staphylococcus aureus (19%) and enterococci (9%) were the most common microbial causes. Aerobic Gram-negative bacilli accounted for 28% and candida for 6%. Coagulase-negative staphylococci, enterococci and candida all became more prevalent as causes of infection over the study period. CONCLUSIONS: The nosocomial blood stream infection rate in the hospital has nearly doubled in the past 10 years, largely due to increased primary bacteremia.     

Significant pathogens isolated from surgical site infections at a community hospital in the Midwest

BACKGROUND: Studies examining the incidence of microorganisms isolated from surgical site infections (SSIs) have been conducted primarily at large academic health care centers. Results from these studies have revealed that methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a significant pathogen in SSIs. Minimal data are available from smaller, community hospitals on the incidence of microorganisms associated with SSIs, particularly the incidence of MRSA in SSIs. METHODS: A retrospective study was performed to identify the microorganisms associated with SSIs in patients who underwent class I and II surgeries at a small urban to rural community hospital from January 2003 through December 2004. RESULTS: A total of 10,672 surgeries was performed, and 89 SSIs were identified. Staphylococcus aureus was the most common pathogen (25.8%). Enterobacteriaceae were the second most frequently isolated organisms (12.4%), followed by streptococci species (11.2%), coagulase-negative staphylococci (10.1%), enterococci species (7.9%), and Pseudomonas aeruginosa (6.7%). MRSA was isolated from 4.5% of the SSIs. CONCLUSION: We have demonstrated that the spectrum of microorganisms isolated in SSIs at a community hospital is comparable with that reported in studies conducted at large academic health care centers, including the emergence of MRSA as a pathogen in SSIs. This information will guide future infection control initiatives to reduce SSIs.     

Surgical site infection: Rates, etiology and resistance patterns to antimicrobials among strains isolated at rio de janeiro university hospital

Summary A 6-month prospective surveillance was conducted in the Department of General Surgery of the Rio de Janeiro University Hospital. Postoperative infections were classified according to CDC criteria. This study reports a significant rate (16.9%) in surgical infections detected by surveillance in a series where 45% of surgical interventions were classified as clean. The majority (52.7%) was apparent only after patient discharge from the hospital. Bacterial cultures were obtained from 42 out of 55 infected wounds.Staphylococcus aureus was the most frequently found pathogen (33.9%), followed byEscherichia coli (20.3%). With the exception ofS. aureus isolates, multiresistance was found in 66% of coagulase-negative staphylococci and 60% of gram-negative bacteria. This study showed that community surveillance associated with hospital surveillance is necessary in order to determine accurate rates of surgical site infections, and also showed that the emergence of multiresistant bacterial strains was common among isolates of surgical infections.     

Therapy with newer oral beta-lactam and quinolone agents for infections of the skin and skin structures: a review.

Amoxicillin/clavulanic acid, cefuroxime axetil, ciprofloxacin, and ofloxacin are each effective against many bacteria that cause infections in the skin and skin structures. Amoxicillin/clavulanic acid is potent against staphylococci, streptococci (including enterococci), and anaerobes, although adverse gastrointestinal reactions are common. Cefuroxime axetil is similarly effective yet is used only rarely because of its more common use in infections of the respiratory tract and the prevalent use of second-generation cephalosporins in surgical prophylaxis. The newer quinolones ciprofloxacin and ofloxacin are effective against staphylococci, Enterobacteriaceae, and Pseudomonas aeruginosa and exhibit only low toxicity; these agents have been used in many difficult tissue infections--notably, chronic infected ulcers in diabetic patients. Oral antimicrobial therapy, when chosen on the basis of culture and susceptibility results and combined with surgical debridement and local management, may be effective for many problematic infections of the skin and skin structures heretofore treated with parenteral antibiotics.     

Usefulness of a test for slime production as a marker for clinically significant infections with coagulase-negative staphylococci

The usefulness of a test for slime production as a marker for clinically significant infections with coagulase-negative staphylococci and its implications for therapy were examined. Hospital records were reviewed for 59 patients from each of whom more than one isolate of coagulase-negative staphylococci was obtained. In patients with a prosthetic device, 81% of 59 infectious episodes were due to a slime-positive coagulase-negative staphylococci. In contrast, 22 noninfectious episodes (in which the organisms were contaminants) were equally distributed between episodes due to slime-positive or slime-negative isolates (P = .005). Only 32% of infections caused by slime-positive organisms, in contrast to 100% of infections caused by slime-negative organisms, were improved by treatment with antibiotics alone (P = .02). Prosthetic device removal in addition to antibiotic treatment significantly improved the outcome in patients with infections due to slime-positive organisms when compared with treatment with antibiotics alone (93% vs. 32% improvement; P = .00025).     

A novel serological test for the diagnosis of central venous catheter-associated sepsis

OBJECTIVES: To determine the sensitivity and specificity of a novel antibody test for the diagnosis of intravascular catheter-related infections due to coagulase-negative staphylococci. METHODS: Sixty-seven patients diagnosed as having central venous catheter (CVC)-associated sepsis based on strict clinical criteria, including positive blood cultures, were compared to 67 patients with a CVC in situ who exhibited no evidence of sepsis. An ELISA serological test based on a novel short-chain lipoteichoic acid antigen isolated from coagulase-negative staphylococci (CNS) was used to determine the patient's serological response (IgG and IgM) to CVC sepsis caused by CNS. The specificity and sensitivity of the test was determined. RESULTS: There was a significant increase in the antibody levels (IgG and IgM) to the short-chain lipoteichoic acid in patients with CVC-associated staphylococcal sepsis as compared to the control patients. CONCLUSIONS: This new serological method may offer a useful diagnostic test for intravascular catheter infections caused by staphylococci.     

Prophylaxis of neurosurgical infections by improved preoperative disinfection of the scalp.

The heads of neurosurgical patients were subject to 2 scrubbings with hexachlorophene detergent, performed in the ward prior to operation. After this single change of routines the frequency of wound infections after craniotomy dropped 4-fold, from 2% to 0.5%. The result indicates that the scalp of the patient is the major source of the staphylococci that cause neurosurgical infections.     

A prospective randomised comparison of cefotaxime vs. netilmicin vs. cefotaxime plus netilmicin in the treatment of hospitalised patients with serious sepsis

93 patients were enrolled into a prospective randomised study to determine the efficacy and safety of netilmicin, cefotaxime or their combination in the treatment of sepsis caused by susceptible strains of Enterobacteriaceae or staphylococci. 83 patients were evaluable for safety, 74 for clinical efficacy and 63 for microbiological response including 36 patients (57%) with positive blood cultures. There were significantly more clinical failures with cefotaxime than with netilmicin even when urinary tract sepsis was excluded. Microbiological failures occurred more frequently in the cefotaxime arm and were associated with Klebsiella and Enterobacter spp. Four cefotaxime failures were subsequently successfully treated with netilmicin. More mixed infections were however enrolled by chance into the cefotaxime arm. The statistical difference between netilmicin and cefotaxime is not significant if mixed infections are excluded. There was no difference in efficacy between the netilmicin and combination groups although superinfection was seen in the latter group. The incidence of nephrotoxicity was greater in the netilmicin group but not significantly so. Only one minor case of ototoxicity was detected in the 41 patients receiving netilmicin who had serial audiograms. The results suggest that netilmicin is a more effective agent than cefotaxime for treating life-threatening infections with susceptible Enterobacteriaceae or staphylococci particularly with infections in non-urinary tract sites. If dosage of netilmicin is closely monitored by measuring serum concentrations, toxicity is minimal.     

Bloodstream infections caused by small-colony variants of coagulase-negative staphylococci following pacemaker implantation.

Small-colony variants (SCVs) of Staphylococcus aureus cause persistent and relapsing infections. Relatively little is known regarding infections caused by SCVs of coagulase-negative staphylococci. We report two cases of pacemaker electrode infections due to SCVs of Staphylococcus epidermidis and Staphylococcus capitis. Sequence analysis of a portion of the 16S rRNA gene (16S rDNA) confirmed the identity of the staphylococcal species as S. capitis and S. epidermidis. Isolates from cultures of blood obtained over at least a 2-week interval were compared by pulsed-field gel electrophoresis and found to be clonal even though the colony morphology was very different. Analysis for auxotrophism revealed hemin dependencies for all isolated SCVs. The two cases have several clinical and laboratory characteristics (which are also seen with S. aureus SCV infections) and strongly suggest that SCVs of coagulase-negative staphylococci must be actively sought, because they grow very slowly and can be easily missed.     

Emergence of ciprofloxacin-resistant coagulase-negative staphylococcal skin flora in immunocompromised patients receiving ciprofloxacin

Seven septicemias in neutropenic leukemia patients (two with fatal outcome) caused by ciprofloxacin-resistant coagulase-negative staphylococci were diagnosed in the hematologic unit of Turku University Central Hospital in 1988 soon after the introduction of the drug. Coagulase-negative staphylococcal skin flora of 28 neutropenic patients receiving ciprofloxacin prophylaxis and therapy for gram-negative bacterial infections were compared with those of 31 untreated patients and 33 hospital personnel working in the same unit. In ciprofloxacin-treated patients the flora were almost completely ciprofloxacin-resistant, whereas in the control groups resistant flora were detected only occasionally. Similarities in the plasmid profile patterns were found in 91% of the ciprofloxacin-resistant coagulase-negative staphylococci, suggesting an epidemiologic relation between these strains. It seems evident that cross-infection is responsible for the spread of ciprofloxacin-resistant coagulase-negative staphylococci in these patients.     

Agents for the treatment of multidrug-resistant gram-positive endocarditis

Several newer agents with activity against multidrugresistant gram-positive pathogens are available. These agents have in vitro and clinical data supporting their utility in the treatment of infections caused by pathogens such as methicillin-resistant staphylococci and vancomycin-resistant enterococci. Daptomycin appears to be rapidly bactericidal, and linezolid and quinupristin/dalfopristin also are cidal against staphylococci. Although the agents have several properties that are attractive for use in endocarditis, clinical data are limited. Further investigation with each agent and combination therapy are warranted before definitive recommendations can be made.     

Staphylococcus aureus nasal carriage in hemodialysis patients. Its role in infection and approaches to prophylaxis

Staphylococcus aureus infections remain a major cause of morbidity in hemodialysis patients. Chronic dialysis patients are more prone to staphylococcal infections because of their decreased immunity, increased skin colonization by staphylococci, and the multiple needle punctures required for dialysis. The source of the staphylococci is the anterior nares. Elimination of staphylococcal nasal carriage results in a significantly lower infection rate. Selected clinical studies of topical and oral therapy for eradication of staphylococcal nasal carriage are reviewed. Rifampin has been the most consistently efficacious agent, although emergence of resistance is a potential problem. Trials utilizing newer topical and oral agents for prophylactic eradication of S aureus from the nose are indicated. Promising antibiotics include topical mupirocin, the oral quinolones, and clindamycin.     

Personal reflections on nosocomial staphylococcal infections and the development of hospital surveillance

A pandemic of staphylococcal infections occurred in the mid-twentieth century and spanned the years from about 1946 (with gradual subsidence) to about 1966. Staphylococcus aureus, originally sensitive to penicillin in 1942, demonstrated, more than other susceptible bacteria, a capacity for the development of antibiotic resistance. Hospital personnel became carriers of antibiotic-resistant staphylococci that contaminated newborn infants and hospitalized children and adults, who then became carriers and suffered an increasing incidence of suppurative disease. Asymptomatic carriers of antibiotic-resistant epidemic strains spread them into communities, with resulting infection of others. Newer antibiotics were developed, only to lose effectiveness as the staphylococci developed resistance. Local, national, and international programs emerged for the development of epidemiologic research, hospital surveillance, and education in methods of prevention and control. Carrier rates of S. aureus among hospital personnel remained approximately 33%, while the incidence of nosocomial staphylococcal infections declined. Staphylococcal pandemics may be cyclic in occurrence.