Outbreaks of Staphylococcus aureus infections during treatment of late onset pneumonia with ciprofloxacin in a prospective, randomized study

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

Immunisation With Immunodominant Linear B Cell Epitopes Vaccine of Manganese Transport Protein C Confers Protection against Staphylococcus aureus Infection

Vaccination strategies for Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA) infections have attracted much research attention. Recent efforts have been made to select manganese transport protein C, or manganese binding surface lipoprotein C (MntC), which is a metal ion associated with pathogen nutrition uptake, as potential candidates for an S. aureus vaccine. Although protective humoral immune responses to MntC are well-characterised, much less is known about detailed MntC-specific B cell epitope mapping and particularly epitope vaccines, which are less-time consuming and more convenient. In this study, we generated a recombinant protein rMntC which induced strong antibody response when used for immunisation with CFA/IFA adjuvant. On the basis of the results, linear B cell epitopes within MntC were finely mapped using a series of overlapping synthetic peptides. Further studies indicate that MntC113-136, MntC209-232, and MntC263-286 might be the original linear B-cell immune dominant epitope of MntC, furthermore, three-dimensional (3-d) crystal structure results indicate that the three immunodominant epitopes were displayed on the surface of the MntC antigen. On the basis of immunodominant MntC113-136, MntC209-232, and MntC263-286 peptides, the epitope vaccine for S. aureus induces a high antibody level which is biased to TH2 and provides effective immune protection and strong opsonophagocytic killing activity in vitro against MRSA infection. In summary, the study provides strong proof of the optimisation of MRSA B cell epitope vaccine designs and their use, which was based on the MntC antigen in the development of an MRSA vaccine.

Anti-infective properties of Lactobacillus fermentum against Staphylococcus aureus and Pseudomonas aeruginosa

Surgical wounds and implant-associated Staphylococcus aureus and Pseudomonas aeruginosa infections are often difficult to treat because of limited susceptibility of several of these strains to conventional antibiotics. As a result, there is a constant need for new alternative drugs. The aim of this study was to investigate the antimicrobial properties of Lactobacillus fermentum, a probiotic bacterium, which we have isolated from colonic biopsies. The inhibition of S. aureus and P. aeruginosa growth was evaluated by coincubating with L. fermentum strains. Growth inhibition was tested for several of their clinical isolates using agar well diffusion assays. For biofilm assay S. aureus and P. aeruginosa were grown on the glass slides and in 96-well plates in presence of 2.5 μg/ml culture filtrate of L. fermentum. Biofilms were photographed using confocal microscope or stained with 0.1% crystal violet. Reduction in the cytotoxicity of S. aureus and P. aeruginosa was observed in presence of 2.5 μg/ml L. fermentum-spent media. Using in vitroexperiments, we showed that L. fermentum-secreted compound(s) inhibits the growth, cytotoxicity and biofilm formation of several S. aureus and P. aeruginosa strains. Compound(s) present in the culture supernatant of L. fermentum may have promising applications in treating hospital-acquired infections.

Comprehensive evidence-based clinical practice guidelines for ventilator-associated pneumonia: diagnosis and treatment

BACKGROUND

Ventilator-associated pneumonia (VAP) is an important cause of morbidity and mortality in ventilated critically ill patients. Despite a large amount of research evidence, the optimal diagnostic and treatment strategies for VAP remain controversial.

PURPOSE

The aim of this study was to develop evidence-based clinical practice guidelines for the diagnosis and treatment of VAP. Data sources include Medline, EMBASE, Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Database of Systematic Reviews and Register of Controlled Trials.

STUDY SELECTION

The authors systematically searched for all relevant randomized controlled trials and systematic reviews on the diagnosis and treatment of VAP in mechanically ventilated adults that were published from 1980 to October 1, 2006.

DATA EXTRACTION

Independently and in duplicate, the panel critically appraised each published trial. The effect size, confidence intervals, and homogeneity of the results were scored using predefined definitions. The full guideline development panel arrived at a consensus for scores on safety, feasibility, and economic issues.

LEVELS OF EVIDENCE

Based on the scores for each topic, the following statements of recommendation were used: recommend, consider, do not recommend, and no recommendation because of insufficient or conflicting evidence.

DATA SYNTHESIS

For the diagnosis of VAP in immunocompetent patients, we recommend that endotracheal aspirates with nonquantitative cultures be used as the initial diagnostic strategy. When there is a suspicion of VAP, we recommend empiric antimicrobial therapy (in contrast to delayed or culture directed therapy) and appropriate single agent antimicrobial therapy for each potential pathogen as empiric therapy for VAP. Choice of antibiotics should be based on patient factors and local resistance patterns. We recommend that an antibiotic discontinuation strategy be used in patients who are treated of suspected VAP. For patients who receive adequate initial antibiotic therapy, we recommend 8 days of antibiotic therapy. We do not recommend nebulized endotracheal tobramycin or intratracheal instillation of tobramycin for the treatment of VAP.

CONCLUSION

We present evidence-based recommendations for the diagnosis and treatment of VAP. Implementation of these recommendations into clinical practice may lessen the morbidity and mortality of patients who develop VAP.

Empiric antibiotic therapy for suspected ventilator-associated pneumonia: a systematic review and meta-analysis of randomized trials

OBJECTIVE

To compare specific antibiotic regimens, and monotherapy vs. combination therapy, for the empirical treatment of ventilator-associated pneumonia (VAP).

DESIGN

Meta-analysis.

DATA SOURCE

Medline, Embase, Cochrane register of controlled trials, study authors, and review articles.

STUDY SELECTION

We included randomized controlled trials that evaluated empirical parenteral antibiotic regimens for adult patients with clinically suspected VAP.

DATA SELECTION

Two independent review groups searched the literature, extracted data, and evaluated trial quality. The primary outcome was all-cause mortality; secondary outcomes included treatment failure. Relative risks were pooled using a random effects model.

RESULTS

We identified 41 trials randomizing 7,015 patients and comparing 29 unique regimens. Methodological quality was low, reflecting low rates of complete follow-up (43.9%), use of a double-blinded interventional strategy (14.6%), and randomization concealment (48.6%). Overall mortality was 20.3%; treatment failure occurred in 37.4% of patients who could be evaluated microbiologically. No mortality differences were observed between any of the regimens compared. Only one of three pooled comparisons yielded a significant difference for treatment failure: The combination of ceftazidime/aminoglycoside was inferior to meropenem (two trials, relative risk 0.70, 95% confidence interval 0.53-0.93). Rates of mortality and treatment failure for monotherapy compared with combination therapy were similar (11 trials, relative risk for mortality of monotherapy 0.94, confidence interval 0.76-1.16; and relative risk of treatment failure for monotherapy 0.88, confidence interval 0.72-1.07).

CONCLUSIONS

Monotherapy is not inferior to combination therapy in the empirical treatment of VAP. Available data neither identify a superior empirical regimen nor conclusively conclude that available regimens result in equivalent outcomes. Larger and more rigorous trials evaluating the choice of, and even need for, empirical therapy for VAP are needed.

[Drug-resistant bacteria isolated from pharyngeal swab cultures and urine in acutely or chronically febrile elderly nursing home inmates]

AIM

Patients in nursing homes are becoming more and more elderly and also prone to infectious diseases. It is important to select proper antimicrobial agents in treating such patients because of the increase in drug-resistant bacteria in recent years.

METHODS

Pathogenic aerobic bacteria were isolated from cultures of the pharyngeal swab obtained from patients with acute febrile episodes and those with chronic febrile conditions with a repetition of fever or continuing low-grade fever. Isolation of pathogens was also carried out in patients with a urinary tract infection that was resistant to treatment. Isolated bacteria were tested for sensitivity to commonly used antimicrobial agents.

RESULTS

Pathogenic bacteria were isolated from 33% of the patients with acute febrile episodes, while they were isolated from 75% of the patients with chronic febrile conditions. The number of major pathogenic bacteria from 85 isolates were methicillin-resistant staphylococcus aureus (MRSA) 13, methicillin-sensitive staphylococcus aureus (MSSA) 6, Streptococcus pneumoniae 8, beta-hemolytic streptococcus 5, Klebsiella pneumoniae 10, and Enterobacter cloacae 6. Only two isolates of Streptococcus pneumoniae were penicillin-sensitive (PSSP), while the others were penicillin-resistant (PRSP) (1) or penicillin-insensitive (PISP) (5). Among these 8 isolates, 5 were resistant to levofloxacin (LVFX). Escherichia coli was isolated from the pharyngeal swab of 2 patients, one of the 2 isolates being resistant to LVFX. Escherichia coli was isolated from 5 patients with urinary tract infection and 5 of the 6 isolates were resistant to LVFX; with one of them being extended spectrum beta-lactamases (ESBL).

CONCLUSION

The frequency of isolation of antimicrobial-resistant pathogens was extremely high among elderly patients in our nursing home compared to values reported from a nation-wide survey recently carried out in Japan. In particular, attention should be focused on the resistance of bacteria to fluoroquinolones.

Skin and skin structure infections: treatment with newer generation fluoroquinolones

Skin and skin structure infections (SSSI) are an emerging issue in healthcare. They are responsible for increasing heathcare utilization, both in hospitalizations and intravenous antibiotic use. SSSI are caused by an evolving variety of pathogens, including Gram-positive, Gram-negative, and anaerobic bacteria. In combination with mounting resistance patterns, this diverse range of bacteria mandate empiric broad-spectrum antibiotic coverage. Historically, cephalosporins and penicillins have been the mainstay of treatment, but recent data suggest newer generation fluoroquinolones are being used with increasing frequency. In 2005, moxifloxacin joined gatifloxacin and levofloxacin as newer generation fluoroquionolones with Food and Drug Administration indications for SSSIs. Even within this group there exist subtle differences that impact optimal management. This paper offers the clinician a comparative review of the antimicrobial spectrum, pharmacodynamics, pharmacokinetics, and clinical efficacy data to support the appropriate use of fluoroquinolones in SSSIs.

Evaluation of an intervention designed to decrease the rate of nosocomial methicillin-resistant Staphylococcus aureus infection by encouraging decreased fluoroquinolone use

OBJECTIVE

Society for Health Care Epidemiology guidelines recommend decreasing the use of fluoroquinolone antibiotics in institutions where methicillin-resistant Staphylococcus aureus (MRSA) is endemic. We evaluated whether an intervention to limit fluoroquinolone use was associated with a lower rate of nosocomial MRSA infection and summarized changes in antibiotic use, changes in other variables potentially correlated with a lower rate of MRSA infection, and rates of nosocomial infections due to other pathogens.

DESIGN

Single-center quasi-experimental design. A time series of nosocomial MRSA infections was measured at monthly intervals from July 2001 through June of 2004; there were 80 MRSA infections recorded. Segmented regression analysis (ie, quasi-Poisson generalized linear models) was used to evaluate variables possibly associated with the nosocomial MRSA infection rate.

SETTING

An 87-bed Veterans Affairs teaching hospital with an extended-care facility.

INTERVENTION

A physician-directed computer-generated intervention designed to limit the use of fluoroquinolone antibiotics was initiated, and institutional changes in antibiotic use and nosocomial MRSA infection rates were tracked.

RESULTS

After the intervention, fluoroquinolone use decreased by approximately 34%, and levofloxacin use decreased by approximately 50%. Decreased fluoroquinolone use was offset by increased cephalosporin, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole use. The nosocomial MRSA infection rate decreased from 1.37 to 0.63 episodes per 1,000 patient-days after the study intervention (P=.02). Coagulase-negative Staphylococcus and Enterococcus infection rates also decreased. However, the rate of infection with gram-negative organisms increased. The rate of MRSA infection was positively correlated with levofloxacin use (P=.01) and azithromycin use (P=.08), whereas it was negatively correlated with summer season (P=.05). In a subsequent model, the rate of MRSA infection was negatively correlated with the study intervention (P=.04).

CONCLUSION

Reduction in the institutional use of fluoroquinolones may be associated with a lower nosocomial MRSA infection rate.

[Staphylococcus aureus: role and impact in the treatment of nosocomial pneumonia]

INTRODUCTION

Staphylococcus aureus (SA) has acquired a leading role in nosocomial pneumonia in terms of both frequency and severity, and poses therapeutic problems, namely antibiotic resistance and difficulties in the management of anti-staphylococcal drugs.

STATE OF THE ART

Epidemiological data confirm that SA is implicated in almost a quarter nosocomial pneumonias, of which about a half are due to methicillin resistant SA (MRSA) in France. The pathophysiology of these infections most often involves inhalation following oropharyngeal carriage. In addition to the risk factors common to all nosocomial pneumonias there are the particular roles of head injury and coma, leading to an increased frequency of SA infection in neuro-surgical patients.

PERSPECTIVES

The non-specific clinical picture, the grave prognosis of these pneumonias and the ineffectiveness against MRSA of the antibiotics used in the treatment of Gram negative infections make empirical treatment difficult.

CONCLUSION

In addition to the antibiotics classically active against SA (notably methicillin for sensitive strains and glycopeptides for MRSA) new agents may allow improvement in the treatment of these patients, even if their place is not yet definitively established.

Control of imported and acquired methicillin-resistant Staphylococcus aureus (MRSA) in mechanically ventilated patients: a dose-response study of enteral vancomycin to reduce absolute carriage and infection

This study aimed to quantify the animate source provided by the patients using the concept of "absolute carriage" by multiplying the carrier rate by the level of carriage; and to compare the impact of a low and high dose of an oropharyngeal vancomycin gel on the absolute MRSA carriage and infection. In all, 265 patients were included, 126 were MRSA positive. Fifty-five patients received 2% vancomycin gel during the first year whilst 4% vancomycin gel was given to 50 patients during the second year. Surveillance swabs of throat and rectum were obtained from all eligible patients on admission and then twice weekly. The vancomycin protocol was started as soon as the surveillance cultures were positive for MRSA. Those patients received one gram of enteral vancomycin daily, divided into four doses. During the first year 2% vancomycin gel 4 ml (80 mg) was applied in the oropharynx in four doses in addition to the enteral solution (Group A). During the second year 4% vancomycin gel 4 ml (160 mg) was used (Group B). The absolute carriage was high during both periods: 3.6 for Group A, and 3.2 for Group B. The 4% vancomycin protocol significantly reduced the absolute carriage, compared to the 2% vancomycin protocol: 2.6 versus 1.5 (P < 0.01). Significant reduction in secondary endogenous infections was found in the second year: seven versus 15 patients (P < 0.05). A total of 3,588 microbiological samples were processed. Neither Staphylococcus aureus with intermediate sensitivity to vancomycin (VISA) nor vancomycin-resistant enterococci (VRE) were detected.

Antimicrobial therapy for patients with severe sepsis and septic shock: an evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for antimicrobial therapy for patients with severe sepsis and septic shock that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSION

Since the prompt institution of therapy that is active against the causative pathogen is one of the most important predictors of outcome, clinicians must establish a system for rapid administration of a rationally chosen drug or combination of drugs when sepsis or septic shock is suspected. The expanding number of antibacterial, antifungal, and antiviral agents available provides opportunities for effective empiric and specific therapy. However, to minimize the promotion of antimicrobial resistance and cost and to maximize efficacy, detailed knowledge of the likely pathogens and the properties of the available drugs is necessary for the intensivist.

Antimicrobial drug use and methicillin-resistant Staphylococcus aureus, Aberdeen, 1996-2000

Relationships between antimicrobial use and MRSA prevalence are analyzed in Aberdeen, Scotland.

Similar to many hospitals worldwide, Aberdeen Royal Infirmary has had an outbreak of methicillin-resistant Staphylococcus aureus (MRSA). In this setting, the outbreak is attributable to two major clones. The relationships between antimicrobial use and MRSA prevalence were analyzed by time-series analysis. From June 1997 to December 2000, dynamic, temporal relationships were found between monthly %MRSA and previous %MRSA, macrolide use, third-generation cephalosporin use, and fluoroquinolone use. This study suggests that use of antimicrobial drugs to which the MRSA outbreak strains are resistant may be an important factor in perpetuating the outbreak. Moreover, this study confirmed the ecologic effect of antimicrobial drug use (i.e., current antimicrobial use) may have an effect on resistance in future patients. Although these results may not be generalized to other hospitals, they suggest new directions for control of MRSA, which has thus far proved difficult and expensive.

Increase in methicillin-resistant Staphylococcus aureus acquisition rate and change in pathogen pattern associated with an outbreak of severe acute respiratory syndrome

Background. An outbreak of severe acute respiratory syndrome (SARS) occurred in our 22-bed intensive care unit (ICU; Prince of Wales Hospital, Hong Kong, HKSAR, China) from 12 March to 31 May 2003, when only patients with SARS were admitted. This period was characterized by the upgrading of infection control precautions, which included the wearing of gloves and gowns all the time, an extensive use of steroids, and a change in antibiotic prescribing practices. The pattern of endemic pathogenic organisms, the rates of acquisition of methicillin-resistant Staphylococcus aureus (MRSA), and the rates of ventilator-associated pneumonia (VAP) were compared with those of the pre-SARS and post-SARS periods.

Methods. Data on pathogenic isolates were obtained from the microbiology department (Prince of Wales Hospital). Data on MRSA acquisition and VAP rates were collected prospectively. MRSA screening was performed for all ICU patients. A case of MRSA carriage was defined as an instance in which MRSA was recovered from any site in a patient, and cases were classified as imported or ICU-acquired if the first MRSA isolate was recovered within 72 h of ICU admission or after 72 h in the ICU, respectively.

Results. During the SARS period in the ICU, there was an increase in the rate of isolation of MRSA and Stenotrophomonas and Candida species but a disappearance of Pseudomonas and Klebsiella species. The MRSA acquisition rate was also increased: it was 3.53% (3.53 cases per 100 admissions) during the pre-SARS period, 25.30% during the SARS period, and 2.21% during the post-SARS period (P < .001). The VAP rate was high, at 36.5 episodes per 1000 ventilator-days, and 47% of episodes were caused by MRSA.

Conclusions. A SARS outbreak in the ICU led to changes in the pathogen pattern and the MRSA acquisition rate. The data suggest that MRSA cross-transmission may be increased if gloves and gowns are worn all the time.

Methicillin resistant Staphylococcus aureus in the critically ill

Methicillin resistant Staphylococcus aureus (MRSA) is endemic within many hospitals worldwide. Critically ill patients on intensive care units have increased risk factors making them especially prone to nosocomially acquired infections. This review addresses the current situation regarding the evolution of MRSA and the techniques for identifying and epidemiologically typing it. It discusses specific risk factors, the morbidity and mortality associated with critically ill patients, and possibilities for future antibiotic treatments.

Enteral vancomycin to control methicillin-resistant Staphylococcus aureus outbreak in mechanically ventilated patients

BACKGROUND

Screening for and treating gut carriage of methicillin-resistant Staphylococcus aureus (MRSA) may control transmission and subsequent endemicity of MRSA.

OBJECTIVE

Enteral vancomycin was evaluated as a measure to control an outbreak of MRSA infection in the intensive care unit (ICU).

METHODS

During the 8-month study of sequential design, 176 patients were admitted, 65 (37%) of whom required a minimum of 3 days of ventilation. Forty-four patients were studied in the first 5 months, during which traditional measures were reinforced (control group). During the following 3 months, 13 of 21 patients developed MRSA carriage and received 2 g/day of enteral vancomycin, with high standards of hygiene maintained (treatment group).

RESULTS

Thirty-three MRSA infections occurred in 22 patients (50%) in the control group, whereas 2 patients (9.5%) had 2 MRSA infections in the treatment group (P <.05 for carriage, infection rates, and episodes). Of the 33 MRSA infections in the control group, 27 were due to MRSA acquired in the ICU, whereas the 2 infections in the treatment group were primary endogenous (ie, caused by MRSA present in the patient's admission flora). The probability of developing an MRSA infection was reduced in patients receiving enteral vancomycin compared with patients in the control group (odds ratio, 0.37; 95% CI, 0.24-0.58). Enteral vancomycin significantly reduced the level of MRSA carriage; the mean carriage index was 1.01 in the control group versus 0.58 in the test group (P <.05). Neither vancomycin-resistant enterococci nor vancomycin-intermediate Staphylococcus aureus were isolated from either surveillance or diagnostic samples.

CONCLUSIONS

The eradication of MRSA gut carriage by enteral vancomycin in a small subset of ICU patients was effective in the control of an MRSA outbreak.

Hospital-acquired pneumonia: challenges and options for diagnosis and treatment

The management of hospital-acquired pneumonia (HAP) presents a major challenge for the clinician. The insensitivity of current diagnostic methods and the increasing prevalence of nosocomial pathogens with multiple antibiotic resistance complicate the issue. Use of mechanical ventilation and broad-spectrum antimicrobials in the intensive care setting predipose patients to acquire HAP more frequently with antimicrobial-resistant pathogens. Controversy exists regarding the patients in which invasive diagnostic testing is indicated; the timing of these procedures is another subject of debate. Proper empirical therapy is fundamental to a favourable outcome, and the selection of inappropriate agents to which pathogens are resistant contributes significantly to morbidity and mortality. In general, there is agreement on the requirement for a thorough knowledge of the local causative organisms and the pathogens' resistance profiles. A wide variety of antimicrobials can be used either as monotherapy or in combinations.

Pseudomonas aeruginosa ventilator-associated pneumonia: comparison of episodes due to piperacillin-resistant versus piperacillin-susceptible organisms

We sought to determine the epidemiological characteristics of patients in an intensive care unit (ICU) who developed ventilator-associated pneumonia (VAP) caused by piperacillin-resistant Pseudomonas aeruginosa (PRPA; n=34) or piperacillin-susceptible P. aeruginosa (PSPA; n=101). According to univariate analysis, the factors associated with the development of PRPA VAP were presence of an underlying fatal medical condition, immunocompromised status, longer previous hospital stay, less-severe illness at the time of ICU admission, duration of mechanical ventilation before onset of VAP, number of classes of antibiotic received, and previous exposure to imipenem or fluoroquinolone. Multivariate logistic regression analysis identified the following significant independent factors: presence of an underlying fatal medical condition (odds ratio [OR], 5.6), previous fluoroquinolone use (OR, 4.6), and initial disease severity (OR, 0.8). We concluded that the clinical characteristics of patients who develop PRPA VAP differ from those of patients who develop PSPA VAP. Restricted fluoroquinolone use is the sole independent risk factor for PRPA VAP that is open to medical intervention.

The Nottingham Staphylococcus aureus population study: prevalence of MRSA among the elderly in a university hospital

A prevalence survey of methicillin-resistant Staphylococcus aureus (MRSA) in elderly patients (65 years and older) three weeks after admission to a university hospital was performed. Risk factors associated with hospital MRSA carriage were determined. The design was a cross-sectional patient-based study and all adult wards at the University Hospital Nottingham (1600 beds) were included. Three hundred and forty-two elderly individuals (65 years and older) were enrolled into the study on day 21 after admission. One hundred and twenty patients [35.08% (95% confidence intervals 29.93-40.25%)] carried S. aureus. MRSA was isolated from 54 patients. The MRSA prevalence was 158/1000 (95% CI 119-197/1000 patients). Independent risk factors for MRSA carriage in the hospital were exposure to ampicillin [adjusted odds ratio 4.1 (95% CI 1.28-13.14)] and ciprofloxacin [17.1 (95% CI 2.91-99.90)]. Forty-one MRSA isolates (75.9%) belonged to the epidemic type EMRSA 15, seven isolates to EMRSA 16 (12.9%) and six isolates were sporadic strains as determined by genetic typing. It can be expected that among this defined risk group, between 187 and 331 patients carried MRSA on discharge in the year 2000. MRSA carriage is frequent and detected in only 15% of actual carriers amongst elderly patients by routine clinical investigations three weeks after admission. The only significant risk factor identified by multivariate logistic regression was antibiotic chemotherapy. The repeated finding of a strong association between MRSA colonization and previous ciprofloxacin exposure demands attention and indicates that fluoroquinolones should be used prudently in institutions where MRSA is endemic.

Antibacterial treatment of invasive mechanical ventilation-associated pneumonia

Patients admitted to intensive care units (ICU) are at higher risk of acquiring nosocomial infections than patients in other hospital areas. This is the consequence of both a greater severity of illness with its implications (manipulation, invasiveness) and crossed infection from reservoirs inside the ICU. The most frequent nosocomial infection is invasive ventilation-associated pneumonia (VAP) which leads to an important increase in morbidity and mortality. The most important aetiological agents in VAP are bacteria, with a marked predominance of Staphylococcus aureus and Pseudomonas aeruginosa. These aetiologies may be different depending upon the type of ICU (medical, surgical, coronary) or the presence of certain risk factors (duration of mechanical ventilation before onset of pneumonia, previous exposure to antibacterials). Susceptibilities of the aetiological agents to antibacterials may also vary according to the type of ICU and over time. Data from global studies show an increase in multiresistant bacteria but these data may not be applied to a local ICU. The availability of accurate and updated information on the most frequently encountered organisms in each ICU and their susceptibilities is very important in order to provide the most adequate treatment. A controversial issue is the selection of antibacterials. According to the latest evidence the most adequate approach is a prompt administration of empirical treatment. Based on knowledge of bacterial flora in our own ICU, the choice of an adequate therapeutic regimen will decrease both morbidity and mortality. A second issue is monotherapy versus combined therapy. The most common recommendation, with a few exceptions, is to use combined therapy until microbiological results are received. Another controversy is the choice of antibacterials in the combined regimen. The most commonly recommended combination is that of a beta-lactam with an aminoglycoside, except in early-onset pneumonia without risk factors. The use of monotherapy with a cefalosporin without antipseudomonal activity or amoxicillin-clavulanic acid is the recommended regimen. Treatment should be modified based on microbiological results. There are no well documented recommendations on the prophylactic duration of treatment and it must be based on the aetiological agent and the clinical course. In summary treatment of VAP must be prompt, empirical and combined (beta-lactam plus aminoglycoside ). However, the choice of the antibacterial regimen should follow local guidelines of treatment based upon the knowledge of the most frequently isolated bacterial flora and their susceptibilities in different clinical settings.

Nosocomial pneumonia. Diagnostic and therapeutic considerations

Many patients with presumed nosocomial pneumonia probably have infiltrates on the chest radiograph, fever, and leukocytosis resulting from noninfectious causes. Because of the high mortality and morbidity associated with nosocomial pneumonias, however, most clinicians treat such patients with a 2-week empiric trial of antibiotics. Before therapy is initiated, the clinician should rule out other causes of pulmonary infiltrates, fever, and leukocytosis that mimic a nosocomial pneumonia (e.g., pre-existing interstitial lung disease, primary or metastatic lung carcinomas, pulmonary emboli, pulmonary drug reactions, pulmonary hemorrhage, collagen vascular disease affecting the lungs, or congestive heart failure). If these disorders can be eliminated from diagnostic consideration, a 2-week trial of empiric monotherapy is indicated. The clinician should treat cases of presumed nosocomial pneumonia as if P. aeruginosa were the pathogen. Although P. aeruginosa is not the most common cause of nosocomial pneumonia, it is the most virulent pulmonary pathogen associated with nosocomial pneumonia. Coverage directed against P. aeruginosa is effective against all other aerobic gram-negative bacillary pathogens causing hospital-acquired pneumonia. The clinician should select an antibiotic for empiric monotherapy that is highly effective against P. aeruginosa, has a good side-effect profile, has a low resistance potential, and is relatively inexpensive in terms of its cost to the institution. The preferred agents for empiric monotherapy for nosocomial pneumonia are cefepime, meropenem, and piperacillin. Single organisms are responsible for nosocomial pneumonia, not multiple pathogens. S. aureus rarely, if ever, causes nosocomial pneumonia but is mentioned frequently in studies based on cultures of respiratory tract secretions. S. aureus, unless accompanied by a necrotizing pneumonia with rapid cavitation within 72 hours, in the sputum indicates colonization rather than infection and should not be addressed therapeutically. Antibiotics associated with a high resistance potential should not be used as monotherapy or included in combination therapy regimens (i.e., ceftazidime, ciprofloxacin, imipenem, or gentamicin). Combination therapy is more expensive than monotherapy and is indicated only when P. aeruginosa is extremely likely, based on its characteristic clinical presentation, or is proved by tissue biopsy. Therapy should not be based on respiratory secretion cultures regardless of technique. Optimal combination regimens include cefepime or meropenem plus levofloxacin or piperacillin or aztreonam or amikacin. Nosocomial pneumonias usually are treated for 14 days. Lack of radiographic or clinical response to appropriate empiric nosocomial pneumonia monotherapy after 14 days suggests an alternate diagnosis. In these patients, a tissue biopsy specimen should be obtained to determine the cause of the persistence of pulmonary infiltrates unresponsive to appropriate antimicrobial therapy.

Risk factors for persistent carriage of methicillin-resistant Staphylococcus aureus

We determined risk factors associated with persistent carriage of methicillin-resistant Staphylococcus aureus (MRSA) among 102 patients enrolled in a double-blind, placebo-controlled trial of nasally administered mupirocin ointment. MRSA decolonization was unsuccessful in 77 (79%) of 98 patients who met the criteria for evaluation. By univariate analysis, 4 variables were found to be associated with persistent MRSA colonization (P < .1 for all 4): absence of mupirocin treatment, previous fluoroquinolone therapy, > or = 2 MRSA-positive body sites, and low-level mupirocin resistance. After multivariable Cox proportional hazards modeling, the presence of > or = 2 positive body sites (adjusted hazard ratio [AHR], 1.7; 95% confidence interval [CI], 1.0-2.9) and previous receipt of a fluoroquinolone (AHR, 1.8; 95% CI, 1.0-3.3) were independently associated with MRSA persistence, whereas nasal mupirocin tended to confer protection (AHR, 0.6; 95% CI, 0.4-1.0). Low-level mupirocin resistance was observed in 9 genotypically different MRSA strains and was not independently associated with chronic MRSA carriage (AHR, 1.5; 95% CI, 0.9-2.5). Our findings suggest that multisite MRSA carriage and previous receipt of a fluoroquinolone are independent risk factors for persistent MRSA colonization.

Nosocomial pneumonia: epidemiology, pathogenesis, diagnosis, treatment and prevention

Nosocomial pneumonia is the second most common nosocomial infection and the leading cause of death from hospital-acquired infection. Supine body position in mechanically ventilated patients, and cardiopulmonary resuscitation and continuous sedation are significant risk factors for developing nosocomial pneumonia. During the past 2 years some new therapeutic approaches for nosocomial pneumonia and modifications to established therapies have been described, such as optimal pharmacodynamic evaluations, monotherapy versus combination therapy, computer-assisted management programmes and antibiotic rotations.

Induction of fibronectin-binding proteins and increased adhesion of quinolone-resistant Staphylococcus aureus by subinhibitory levels of ciprofloxacin

We recently reported that strain EN1252a, a fluoroquinolone-resistant derivative of Staphylococcus aureus NCTC8325 with mutations in grlA and gyrA, expressed increased levels of fibronectin-binding proteins (FnBPs) and showed a significantly higher attachment to fibronectin-coated polymer surfaces after growth in the presence of subinhibitory concentrations of ciprofloxacin. The present study evaluated the occurrence and frequency of fluoroquinolone-induced FnBP-mediated adhesion in clinical isolates of fluoroquinolone-resistant methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA). Eight of ten MRSA isolates and four of six MSSA isolates with grlA and gyrA mutations exhibited significant increases in attachment to fibronectin-coated surfaces after growth in the presence of one-quarter the MIC of ciprofloxacin. Fluoroquinolone-induced FnBP-mediated adhesion of one clinical MRSA strain and the double mutant strain EN1252a also occurred on coverslips removed from the subcutaneous space of guinea pigs. For strain EN1252a, the regulation of fnb transcription by sub-MICs of ciprofloxacin was studied on reporter plasmids carrying fnb-luxAB fusions. One-quarter of the MIC of ciprofloxacin significantly increased fnbB, but not fnbA, promoter activity of the fluoroquinolone-resistant mutant but not its fluoroquinolone-susceptible parent ISP794. This response was abolished by pretreatment with rifampin, indicating an effect at the level of transcription. Activation of the fnbB promoter was not due to an indirect effect of ciprofloxacin on growth rate and still occurred in an agr mutant of strain EN1252a. These data suggest that sub-MIC levels of ciprofloxacin activate the fnbB promoter of some laboratory and clinical isolates, thus contributing to increased production of FnBP(s) and leading to higher levels of bacterial attachment to fibronectin-coated or subcutaneously implanted coverslips.