Quantitative culture of endotracheal aspirates in the diagnosis of ventilator-associated pneumonia in patients with treatment failure

STUDY OBJECTIVE: To study the correlation of bacteriology between quantitative cultures of protected specimen brush (PSB), BAL, and quantitative endotracheal aspirate (QEA) in ventilator-associated pneumonia (VAP) patients with treatment failure. DESIGN: Prospective observational clinical study. SETTING: A 15-bed medical ICU of tertiary medical center. PATIENTS: Forty-eight patients receiving mechanical ventilation with clinical suspected VAP who had been treated with antibiotics for at least 72 h without improvement. INTERVENTION: QEA, PSB, and BAL were performed with patients receiving antibiotics. The diagnostic thresholds for QEA, PSB, and BAL were 10(5), 10(3), and 10(4) cfu/mL, respectively. MEASUREMENTS AND RESULTS: Microbial culture findings were positive in 24 BAL samples (50%), in 23 PSB samples (48%), and in 28 QEA samples (58%). The correlations between of QEA vs PSB and QEA vs BAL were significant (rho = 0.567 and rho = 0.620, p < 0.01, respectively). The most commonly isolated microorganisms were Acinetobacter baumannii (27%), Staphylococcus aureus (24%), Stenotrophomonas maltophilia (15%), and Pseudomonas aeruginosa (10%). Using the predetermined criteria, bacterial pneumonia was diagnosed in 28 of 48 suspected VAP episodes based on PSB and/or BAL results. The diagnostic efficiency of QEA at threshold of 10(5) cfu/mL had a sensitivity of 92.8% and a specificity of 80%. CONCLUSIONS: QEA correlated with PSB and BAL in patients with suspected VAP who responded poorly to the existent antibiotic treatment. QEA missed only two cases of bacterial pneumonia diagnosed by invasive PSB and/or BAL with acceptable sensitivity and specificity. More importantly, QEA is noninvasive and easily repeatable. Early use of QEA is helpful to clinical physicians in decision making with regard to antibiotics use.     

The significance of distal bronchial samples with commensals in ventilator-associated pneumonia: colonizer or pathogen?

STUDY OBJECTIVE: To investigate the role of oropharyngeal and cutaneous commensal microorganisms (OCCs) as a cause of ventilator-associated pneumonia (VAP). DESIGN: Retrospective analysis of the medical and microbiological records. SETTING: One medical-surgical ICU. PATIENTS: All VAP episodes recorded during a 10-year period were reviewed. All patients with suspected VAP underwent bronchoscopy with protected-specimen brush (PSB) sampling and BAL before any change in antibiotic therapy was made. OCC-VAP was defined as VAP with significant growth in quantitative cultures (PSB yielded > or = 10(3) cfu/mL and/or BAL yielded > or = 10(4) cfu/mL) of OCCs only. Three experts reviewed the episodes. Exposed patients (ie, those with OCC-VAP) and unexposed patients (ie, patients without VAP) matched on condition severity at ICU admission and mechanical ventilation duration were compared. RESULTS: Twenty-nine episodes in 28 patients with > or = 10(4) cfu/mL OCCs in BAL fluid and/or > or = 10(3) cfu/mL OCCs in PSB specimens were found. All patients in these episodes had new radiologic lung infiltrates, with 26 episodes involving purulent tracheal aspirates, 23 episodes involving temperatures > or = 38.5 degrees C, and 18 episodes involving > or = 11,000 leukocytes/ microL. The main OCCs found were non-beta-hemolytic Streptococcus spp (n = 12), Neisseria spp (n = 7), and coagulase-negative Staphylococcus spp (n = 6). Other possible reasons for fever and the presence of new chest infiltrates were found in 20 and 17 patients, respectively. Histologic evidence of pneumonia was found in 2 of the 10 patients who died. The three experts agreed on the diagnosis for 23 patients. In the OCC-VAP group only, the mean (+/- SD) logistic organ dysfunction (LOD) scores increased significantly (LOD score, 2 +/- 4; p = 0.008) during the 3 days before bronchoscopy, and ICU stay duration was longer than in the unexposed group. The exposed/unexposed study found no difference in mortality. CONCLUSION: OCCs may behave like classic nosocomial pathogens in critically ill patients.     

Antibiotic utilization and outcomes for patients with clinically suspected ventilator-associated pneumonia and negative quantitative BAL culture results

OBJECTIVE: To evaluate antibiotic utilization and clinical outcomes among patients with clinically suspected ventilator-associated pneumonia (VAP) and culture-negative BAL (CNBAL). DESIGN: Prospective observational cohort study. SETTING: A medical ICU from a university-affiliated urban teaching hospital employing a previously described antibiotic discontinuation guideline for the management of VAP. PATIENTS: One hundred one patients with a clinical suspicion of VAP and CNBAL were evaluated between July 2002 and December 2004. INTERVENTIONS: Prospective patient follow-up and data collection. Antibiotic discontinuation was determined by the clinical guideline and not the results of BAL cultures. RESULTS: The average age of the patients was 60.4 +/- 17.9 years and the mean APACHE II score was 23.2 +/- 8.7 (+/- SD). The mean duration of mechanical ventilation prior to clinically suspected VAP was 2.9 +/- 1.9 days. Nineteen patients (18.8%) received antibiotics for other indications prior to BAL. Empiric antibiotic therapy for VAP was begun in 65 patients (64.4%) following BAL. The duration of empiric antibiotic treatment following BAL was 2.1 +/- 0.8 days. None of these patients received antibiotics for > 3 days (median, 2 days; range, 1 to 3 days). Six patients (5.9%) were treated with antibiotics for a secondary episode of VAP or hospital-acquired pneumonia developing at least 72 h after the CNBAL was performed and discontinuation of the empiric antibiotic therapy prescribed for the initially suspected episode of VAP. Overall, 35 patients (34.7%) died during hospitalization. Two deaths occurred in patients with a secondary episode of VAP following CNBAL and discontinuation of empiric antimicrobial therapy. Neither of these two deaths was attributed to VAP. CONCLUSIONS: Although the decision to discontinue antibiotic treatment was based on clinical criteria and not BAL culture results, this study suggests that patients with a clinical suspicion of VAP and CNBAL can have empiric antimicrobial therapy safely discontinued within 72 h or in some cases withheld altogether. Prospective studies are needed to determine the safety of employing CNBAL as the primary criterion for the discontinuation of empirically begun antibiotic treatment for VAP.     

Venous access port--related bacteremia in patients with acquired immunodeficiency syndrome or cancer: the reservoir as a diagnostic and therapeutic tool.

To describe the rate of response to an antibiotic-lock technique (ALT) in the treatment of venous access port (VAP)--related bacteremia and to analyze the role of the reservoir in the persistence of infection, we reported the data from 12 human immunodeficiency virus--infected and 8 oncologic patients with VAP-related bacteremia. The ALT consisted of intracatheter delivery of antibiotics and was associated with a systemic antibiotic infusion. We monitored clinical manifestations and performed qualitative and quantitative blood cultures during and at the end of the treatment. Four patients had catheters removed before antibiotic treatment. Of the 16 patients who were treated with the ALT, 5 (31%) were cured, as determined by negative cultures of blood and of samples from the catheter; 2 (12.5%) were cured but had recurrent infection with another microorganism; and 9 (56%) had persistent positive cultures of blood and of samples from the tip, reservoir, or both of the VAP. Limited efficacy of the ALT might be explained by the presence of deposits of fibrin that include clusters of bacteria inside the reservoir of the port.     

Successful short-term suppression of clarithromycin-resistant Mycobacterium avium complex bacteremia in AIDS. California Collaborative Treatment Group.

During a randomized study of clarithromycin plus clofazimine with or without ethambutol in patients with AIDS and Mycobacterium avium complex (MAC) bacteremia, eight participants received additional antimycobacterial drugs following the detection of a clarithromycin-resistant isolate (MIC, > 8 micrograms/mL). A macrolide (seven received clarithromycin, one azithromycin) and clofazimine were continued; additional treatment included various combinations of ethambutol, ciprofloxacin, amikacin, and rifabutin. After the detection of a resistant isolate and before receipt of additional antimycobacterials, the median peak MAC colony count in blood was 105 cfu/mL (range, 8-81,500 cfu/mL). After additional antimycobacterials, the median nadir MAC colony count was 5 cfu/mL (range, 0-110 cfu/mL). Five (63%) of eight patients had a > or = 1 log10 decrease, including two who achieved negative blood cultures; all of these responses occurred in patients originally assigned to clarithromycin plus clofazimine. Treatment of clarithromycin-resistant MAC bacteremia that emerges during clarithromycin-based treatment can decrease levels of bacteremia and transiently sterilize blood cultures.     

Outcome of bacteremia and fungemia in paediatric oncology patients

OBJECTIVE:

To determine the outcome of paediatric oncology patients with positive blood cultures.

DESIGN:

Retrospective chart review.

SETTING:

Tertiary care hospital.

POPULATION STUDIED:

Oncology patients up to 17 years of age with positive blood cultures from January 1, 1994 to March 31, 1999.

MAIN RESULTS:

There were 121 episodes of positive blood cultures in 76 patients. Seventeen episodes were excluded because blood cultures were contaminated. Of the organisms grown from the remaining episodes, 63% were Gram-positive organisms, 23% were Gram-negative organisms, 3% were fungal and 11% were mixed. There were 13 episodes with pure or mixed isolates of Staphylococcus aureus, of which nine occurred within 14 days of the placement of a new central venous tunnelled catheter. Central venous tunnelled catheters were retained in 76 of the 102 episodes when they were present. There were two relapses, and four children were admitted to the intensive care unit with septic shock, but all survived.

CONCLUSIONS:

The outcome was excellent with the current management of possible bacteremia in paediatric oncology patients, but the high incidence of S aureus bacteremia suggests that empirical antibiotics should be altered if sepsis is suspected within 14 days of the placement of a central venous catheter.Key Words: Bacteremia, Empirical antibiotics, Fungemia, Oncology, PaediatricBacteremia and fungemia are common causes of morbidity in paediatric oncology patients. Mucositis of the gastrointestinal tract undoubtedly results in increased opportunities for bacteremia to occur. Impaired host defenses and the seeding of indwelling venous lines increase the chance that this bacteremia will be continuous rather than transient. Bacteremia also occurs following breaks in sterile technique during the manipulation of venous lines. The pathogenesis of fungemia in this patient population is not well delineated, but one likely source is from venous catheters being infected following transient fungemia from gut flora.It is standard practice to start empirical antibiotics in all febrile oncology patients who are neutropenic. The empirical antibiotic regimen used in paediatric oncology patients in our centre is tobramycin and piperacillin. Most non- neutropenic febrile oncology patients are also admitted and started on these same antibiotics, because there is evidence that their incidence of bacteremia may be at least as frequent as that of neutropenic patients (1). In our centre, venous catheters are removed in the face of suspected line infection only if the venous catheters are nontunnelled, permanent venous access is no longer required, the infecting organism is a yeast, bacteremia persists after several days of appropriate antibiotics or the patient has septic shock that is thought to be line-related. The purpose of the present study was to evaluate the outcome of patients by using this approach to suspected bacteremia or fungemia.     

Colonization and molecular epidemiology of coagulase-negative Staphylococcal bacteremia in cancer patients: a pilot study

BACKGROUND: Controversy surrounds the source (skin vs mucosa) of coagulase-negative staphylococci (CoNS) bacteremia in cancer patients. Determining the source of this infection has clinical and epidemiologic implications. OBJECTIVE: To determine the source(s) of CoNS bacteremia in cancer patients. METHODS: Between November 1998 and October 2000, cultures of nasal and rectal mucosa and skin at central venous catheter (CVC) sites were obtained in 62 patients (66 episodes) with CoNS-positive blood culture(s). Bacteremia was classified as true, indeterminate, or unlikely on the basis of clinical and microbiologic findings. Molecular relatedness of strains isolated from the blood and from colonized sites of patients with true and those with unlikely bacteremia was examined using pulsed-field gel electrophoresis (PFGE). RESULTS: CoNS colonization was present in 55 episodes (83%). The nasal mucosa was the most frequently colonized site (86%), followed by rectal mucosa (40%) and skin at site of CVC insertion (38%) (P < .001). Colonization at > or =1 site was common. True and unlikely bacteremia accounted for 11 and 10 episodes, respectively, with the remaining 45 episodes considered undetermined or had negative surveillance cultures. Among patients with true bacteremia, 6 mucosal isolates and only 1 skin isolate were related by PFGE to the blood isolate recovered from the same patient. CONCLUSION: Mucosa is the most common site of CoNS colonization and is the likely source of CoNS bacteremia in cancer patients.     

Incidence and outcome of polymicrobial ventilator-associated pneumonia

STUDY OBJECTIVE: To determine the epidemiology and outcome of polymicrobial ventilator-associated pneumonia (VAP). SETTING: Two ICUs (18 and 17 beds) in a university hospital. DESIGN AND PATIENTS: We undertook a 16-month study of 124 patients in whom a first episode of VAP had been diagnosed. Patients in whom there was a suspicion of clinical or radiologic VAP underwent bronchoscopy, and VAP was confirmed by the presence of at least two of the following criteria: > or = 2% of cells with intracellular bacteria found on direct examination of BAL fluid (BALF); protected-specimen brush sample culture with > or = 10(3) cfu/mL; or BALF culture with > or = 10(4) cfu/mL. RESULTS: Monomicrobial infections were diagnosed in 65 patients (52%), and polymicrobial infections were diagnosed in 59 patients (48%). Two different bacteria were isolated in 42 patients (34%), three different bacteria were isolated in 10 patients (8%), and four different bacteria were isolated in 7 patients (6%). Patients' clinical characteristics at ICU admission and on the day of bronchoscopy were similar, particularly the prior duration of mechanical ventilation (MV), the type of ICU admission, disease severity scores, and antibiotic therapy received before VAP was diagnosed. The percentages of nonfermenting, Gram-negative bacilli and methicillin-resistant staphylococci involved in monomicrobial and polymicrobial episodes were similar. Furthermore, no significant difference was detected in outcome parameters, specifically in the mortality rate at 30 days, the ICU mortality rate, the duration of MV, and the rate of infection relapse. CONCLUSION: In our study population, the epidemiology and outcomes of patients with monomicrobial and polymicrobial VAP did not differ significantly.     

Quantitative culture of endotracheal aspirate and BAL fluid samples in the management of patients with ventilator-associated pneumonia: a randomized clinical trial

OBJECTIVE:

To compare 28-day mortality rates and clinical outcomes in ICU patients with ventilator-associated pneumonia according to the diagnostic strategy used.

METHODS:

This was a prospective randomized clinical trial. Of the 73 patients included in the study, 36 and 37 were randomized to undergo BAL or endotracheal aspiration (EA), respectively. Antibiotic therapy was based on guidelines and was adjusted according to the results of quantitative cultures.

RESULTS:

The 28-day mortality rate was similar in the BAL and EA groups (25.0% and 37.8%, respectively; p = 0.353). There were no differences between the groups regarding the duration of mechanical ventilation, antibiotic therapy, secondary complications, VAP recurrence, or length of ICU and hospital stay. Initial antibiotic therapy was deemed appropriate in 28 (77.8%) and 30 (83.3%) of the patients in the BAL and EA groups, respectively (p = 0.551). The 28-day mortality rate was not associated with the appropriateness of initial therapy in the BAL and EA groups (appropriate therapy: 35.7% vs. 43.3%; p = 0.553; and inappropriate therapy: 62.5% vs. 50.0%; p = 1.000). Previous use of antibiotics did not affect the culture yield in the EA or BAL group (p = 0.130 and p = 0.484, respectively).

CONCLUSIONS:

In the context of this study, the management of VAP patients, based on the results of quantitative endotracheal aspirate cultures, led to similar clinical outcomes to those obtained with the results of quantitative BAL fluid cultures.     

Absence of significant bacteremia during urinary catheter manipulation in patients with chronic indwelling catheters

The objective of this study was to quantify the microorganisms present in blood at urinary catheter removal and at reinsertion in patients with chronic indwelling urinary catheters. This was a prospective study during a 4-month period at a university-affiliated geriatric medical center. Our subjects were 33 patients with chronic indwelling urinary catheters and positive urinary cultures; the urinary catheter was usually changed once a month. A peripheral vein line was used for blood withdrawal and urinary cultures and quantitative blood cultures (Isolator) were performed during and shortly after urinary catheter removal and insertion. All patients had significant bacteriuria (greater than 10(5) cfu/mL) with an average of 2.3 microorganisms. Among the 46 sequential quantitative blood cultures performed, only two patients had bacteremia from the urinary source and at a very low concentration; one patient had 0.13 cfu/mL Str. faecalis in blood 5 minutes after removal of the urinary catheter, and the other 0.1 cfu/mL Proteus mirabilis 5 minutes after reinsertion of a new urinary catheter. None of the patients had any subjective or objective clinical problem during the 36 hours after the urinary manipulation. Clinical symptoms and bacteremia are rare events, and prophylactic antibiotics do not appear necessary during urinary catheter removal and reinsertion in elderly institutionalized patients. Further studies are necessary to identify risk factors in the rare instances of patients with bacteremia.     

Stable patients receiving prolonged mechanical ventilation have a high alveolar burden of bacteria

INTRODUCTION: In patients receiving prolonged mechanical ventilation (PMV), quantitative bronchoscopic culture has not been validated for the diagnosis of ventilator-associated pneumonia (VAP). OBJECTIVE: To measure the alveolar burden of bacteria in patients receiving PMV. SETTING: Respiratory care units of a university hospital and a long-term care facility. PATIENTS: Fourteen patients requiring PMV without clinical evidence of pneumonia. MEASUREMENTS: Quantitative culture of BAL from the right middle lobe and lingula. RESULTS: In 29 of 32 lobes, there was growth of at least one organism at > 10(4) cfu/mL. Most lobes had polymicrobial growth. CONCLUSIONS: Stable patients receiving PMV without clinical pneumonia have a high alveolar burden of bacteria. The bacterial burden in most patients exceeds the commonly accepted threshold for diagnosing VAP. The utility of quantitative bronchoscopic culture in the diagnosis of VAP in this patient population requires further study.     

A prospective study of fever and bacteremia after flexible fiberoptic bronchoscopy in children

STUDY OBJECTIVES: To assess the incidence of fever and bacteremia after fiberoptic bronchoscopy in immunocompetent children. DESIGN: Prospective study. PATIENTS: Immunocompetent children undergoing fiberoptic bronchoscopy between January 1997 and June 1998. Measurements and results: Ninety-one children were included in the study. Forty-four children (48%) developed fever within 24 h following bronchoscopy. Bacteremia was not detected in any of the cases at the time of the fever. Children who developed fever were younger than those who remained afebrile (mean age, 2.4 +/- 3.6 years vs 4.2 +/- 3.7 years; p = 0.025). In the fever group, 66% of the bronchoscopies were considered abnormal, compared to 45% in the nonfever group (p = 0.04). Of the fever group, 40.5% of BAL fluid cultures had significant bacterial growth, significantly higher compared to the nonfever group (13.2%; p = 0.006). Of the 80 patients in whom BAL was performed, fever occurred in 52.5% compared to only 18.2% in those who did not have BAL (p = 0.03). BAL fluid content of cell count, lipid-laden macrophages, and interleukin-8 were not significantly different in both groups. In a logistic regression analysis, the significant predictors for developing fever were positive bacterial culture (relative risk, 5.1; 95% confidence interval, 1.6 to 16.4; p = 0.007) and abnormal bronchoscopic findings (relative risk, 3.1, 95% confidence interval, 1.2 to 8.3; p = 0.02). When age < 2 years was included in the model, this factor became highly significant (relative risk, 5.01; 95% confidence interval, 1.83 to 13.75; p < 0.002). CONCLUSIONS: Fever following fiberoptic bronchoscopy is a common event in immunocompetent children and is not associated with bacteremia. Risks to develop this complication are age < 2 years, positive bacterial cultures in BAL fluid, and abnormal bronchoscopic findings.     

Impact of BAL in the management of pneumonia with treatment failure: positivity of BAL culture under antibiotic therapy

BACKGROUND: Pneumonia is responsible for 50% of antibiotics prescribed in ICUs. Treatment failure, ie, absence of improvement or clinical deterioration under antibiotic therapy, presents a dilemma to physicians. BAL is an invasive method validated for etiologic diagnosis in pneumonia. Study objective: To evaluate in ICU patients the impact of BAL in the etiologic diagnosis, treatment, and outcome of pneumonia with treatment failure. DESIGN: Prospective clinical study. SETTING: Nonsurgical, medical ICU of a university hospital in Brazil. Patients and participants: Sixty-two episodes of pneumonia treated for at least 72 h without clinical improvement in 53 patients hospitalized for diverse clinical emergencies. Mean duration of hospitalization was 14.2 days. Mean duration of previous antibiotic therapy was 11.4 days. INTERVENTIONS: Bronchoscopy and BAL were performed in each episode. BAL fluid was cultivated for aerobic and anaerobic bacteria; the cutoff considered positive was 10(4) cfu/mL; 10(3) cfu/mL was also analyzed if under treatment. Pneumocystis carinii, fungi, Legionella spp, and Mycobacterium spp were also researched. Measurements and results: Fifty-eight of 62 BAL were performed under antibiotics. The results showed positivity in 45 of 62 (72.6%); 42 of the 45 positive episodes (93.3%) had > 10(4) cfu/mL. The three cases with between 10(3) and 10(4) cfu/mL were considered positive and were treated according to BAL cultures. The main agents were Acinetobacter baumannii (37.1%), Pseudomonas aeruginosa (17.7%), and methicillin-resistant Staphylococcus aureus (MRSA; 16.1%); 46.7% of the episodes (21 of 45) were polymicrobial. BAL results directed a change of therapy in 34 episodes (54.8%). Overall mortality was 43.5%. There was no difference in mortality among positives, negatives, and patients who changed therapy guided by BAL culture. CONCLUSIONS: (1) BAL fluid examination was positive in 45 of 62 episodes (72.6%), with 58 of 62 BAL performed under antibiotics. This suggests that BAL may be a sensitive diagnostic method for treatment failures of clinically diagnosed pneumonias, even if performed under antibiotics; (2) the main pathogens in our study were A baumannii, P aeruginosa, and MRSA, and approximately 45% of infections were polymicrobial; (3) BAL culture results directed a change of therapy in 75.6% of positive episodes (34 of 45) and in 54.8% of all episodes of treatment failure (34 of 62); and (4) there was no difference in mortality among positives, negatives, and patients who changed therapy guided by BAL culture.     

Contribution of blinded, protected quantitative specimens to the diagnostic and therapeutic management of ventilator-associated pneumonia

OBJECTIVE: Sampling techniques for microbiological diagnosis of ventilator-associated pneumonia (VAP) remain debated, and it is unclear to what extent invasive diagnostic techniques impact the management of patients. DESIGN: A prospective observational study of 68 first episodes of suspected pneumonia in which specimens were obtained blindly (endotracheal aspirate [EA] and blinded protected telescoping catheter [PTC]) and via bronchoscopy (directed PTC bronchoscopy and BAL), and in sequence, and the results were provided to the attending physicians in the same order. Therapeutic plans resulting at each step were examined, and their adequacy was assessed using quantitative BAL fluid culture as the diagnostic standard. PARTICIPANTS: Sixty-eight patients with clinically suspected VAP hospitalized in two ICUs in a tertiary care university hospital. RESULTS: There were 35 patients (51%) with VAP confirmed by BAL fluid culture (13 early onset and 22 late onset). EA specimens grew organisms (light growth or more) in all BAL-confirmed VAP cases and 59% of nonconfirmed cases, whereas the sensitivity and specificity of blinded PTC quantitative cultures were 77% and 97%, and did not differ from those of directed PTC cultures (77% and 94%, respectively). Antibiotic therapy based on the clinical severity and likelihood of VAP, Gram stain results, and early blinded PTC culture results was adequate in 54% (19 of 35 VAP patients) within 2 h of sampling and 80% (28 of 35 patients) within 24 h; therapy was revised in only 3 more patients following BAL culture results. New antibiotics were introduced within the first 24 h in 14 of 33 nonconfirmed episodes (42%), and antibiotics were withheld or withdrawn within 48 h in 23 episodes (70%); three of these patients-with both blinded PTC and BAL growing organisms below the threshold-had early subsequently confirmed pneumonia with the same organism. CONCLUSIONS: A therapeutic approach guided by quantitative cultures of blinded specimens helps achieve early adequate management of approximately 90% of patients suspected of having VAP.     

Soluble triggering receptor expressed on myeloid cell-1 is increased in patients with ventilator-associated pneumonia: a preliminary report

RATIONALE: The diagnosis of ventilator-associated pneumonia (VAP) can be difficult. Soluble triggering receptor expressed on myeloid cell-1 (sTREM-1) has been reported to be elevated in BAL fluid from patients with VAP. OBJECTIVES: To evaluate the utility of sTREM-1 in the diagnosis of VAP in BAL fluid and the fluid collected in the expiratory trap from the ventilator, the exhaled ventilator condensate (EVC). METHODS: We prospectively collected BAL fluid and EVC from 23 patients clinically suspected of having VAP. A sensitive enzyme-linked immunosorbent assay was developed to measure sTREM-1. The results derived from this assay were confirmed using an immunoblot technique. The presence of VAP was clinically determined using a modified clinical pulmonary infection score of > 6. RESULTS: VAP was diagnosed in 14 of 23 patients. sTREM-1 was detected in the EVC from 11 of 14 subjects with VAP, but from only 1 of 9 subjects without VAP, and was significantly higher in the pneumonia patients and when expressed as picograms per milliliter or picograms per microgram protein (p = 0.005, both comparisons). In contrast, sTREM-1 was detected in the BAL fluid of all 14 VAP subjects but also in 8 of 9 subjects with no pneumonia, and did not differ in the VAP subjects compared to the nonpneumonia subjects when expressed as picrograms per milliliter or picograms per microgram protein (p > 0.05 both comparisons). CONCLUSION: sTREM-1 is detectable in EVC and may be useful in establishing or excluding the diagnosis of VAP.     

On denial

Evaluation of 612 episodes of gram-negative bacteremia over a 10-year period demonstrated its progressively increasing frequency. This increase was associated with an increasing proportion of patients with more severe underlying disease, increasing patient age, increasing frequency of cardiac surgery and manipulative procedures, and increasing frequency of treatment with antibiotics, corticosteroids and antimetabolites in patients with bacteremia. Fatality rates paralleled the severity of the host's underlying disease as noted in previous reports. The urinary tract was the most frequent source of bacteremia, but in 30 per cent of the patients, predominantly those with more severe underlying disease, the original source could not be identified. Of all blood cultures obtained in these patients, 72 per cent were positive. Bacteremia was of low magnitude with 77 per cent of the patients having quantitative blood cultures with less than 10 gram-negative bacilli per milliliter of blood. Escherichia coli was the most frequent etiologic agent followed in frequency by Klebsiella-Enterobacter-Serratia species, Pseudomonas aeruginosa, Proteus and Providencia species, and species of Bacteroides. Sixteen per cent of the bacteremias were polymicrobic. K and O-antigen typing of Escherichia coli and capsular typing of K. pneumonias demonstrated that a large number of serologic types of these strains were responsible for bacteremia. Over-all, bacteremia caused by multiple species of bacteria was associated with higher fatality rates, but no significant differences in fatality rates could be demonstrated for bacteremias caused by individual species of gram-negative bacilli when comparisons were made between patients with underlying diseases of similar severity. The presence or type of K-antigen did not influence the lethality of Esch. coli infections. Although some O-antigen types, 0:4, 0:6 and 0:8, were associated with higher fatality rates than other O-antigen types, “rough” or autoagglutinable Esch. coli were as lethal as smooth strains. These findings indicate that bacterial factors, other than antibiotic resistance, have little influence on the outcome of gram-negative bacteremia and that gram-negative bacilli function primarily as “opportunistic” pathogens.     

Role of different routes of tracheal colonization in the development of pneumonia in patients receiving mechanical ventilation.

STUDY OBJECTIVE: To evaluate the importance of the different pathogenic pathways involved in the development of ventilator-associated pneumonia (VAP). DESIGN: Prospective study. SETTING: An 18-bed medical and surgical ICU. PATIENTS: One hundred twenty-three patients receiving mechanical ventilation (MV). INTERVENTIONS: Tracheal, pharyngeal, and gastric samples were obtained simultaneously every 24 h. In cases where VAP was suspected clinically, bronchoscopy with protected specimen brush and BAL were performed. Semiquantitative cultures of pharyngeal samples and quantitative cultures for the remaining samples were obtained. RESULTS: Tracheal colonization at some time during MV was observed in 110 patients (89%). Eighty patients had initial colonization, 34 patients had primary colonization, and 50 patients had secondary colonization. Nineteen patients had VAP, and 25 organisms were isolated. For none of these organisms was the stomach the initial site of colonization. Gram-positive organisms colonized mainly in the trachea during the first 24 h of MV (p<0.001). On the contrary, enteric Gram-negative bacilli (p<0.001) and yeasts (p<0.002) colonized the trachea secondarily. Previous endotracheal intubation (p<0.005) and acute renal failure before admission to the ICU (p<0.001) were associated with colonization by Pseudomonas aeruginosa; prior antibiotics were associated with colonization by Acinetobacter baumanii (p<0.05) and yeasts (p<0.006); and cranial trauma was associated with Staphylococcus aureus colonization (p<0.035). CONCLUSIONS: Although the stomach can be a source of organisms that colonize the tracheobronchial tree, it is a much less common source of the bacteria that cause VAP. The pattern of colonization and risk factors may be different according to the type of organisms involved.     

Bacteremia with upper gastrointestinal endoscopy.

Fifty patients undergoing upper gastrointestinal fiberoptic endoscopy were studied prospectively for the development of bacteremia by aerobic and anerobic blood cultures obtained before, during, and at 5 and 30 minutes after the procedure. Forty-six patients were culture negative; four had positive cultures at 5 or 30 minutes after the procedure, or at both times. The level of bacteremia as estimated by pour plates was very low. Bacteremia did not correlate with the performance of biopsy or the type of mucosal abnormality found. It is concluded that only very high-risk patients should receive antimicrobial prophylaxis before this procedure. The minor risk of this low-level bacteremia should not be considered a contraindication to the performance of upper gastrointestinal endoscopy.