Quantitative tracheal lavage versus bronchoscopic protected specimen brush for the diagnosis of nosocomial pneumonia in mechanically ventilated patients

Pneumonia in mechanically ventilated patients: no diagnostic and prognostic value of different quantitative tracheal aspirates thresholds

BACKGROUND

Diagnosis of pneumonia in ventilated patients is challenging due to the lack of specific and definitive clinical symptoms, laboratory data or radiological abnormalities.

METHODS

Based on quantitative tracheal aspirate (QTA) results, three groups of patients were compared: <10⁵ cfu/ml, ≥10⁵ cfu/ml and <10⁶ cfu/ml, and ≥10⁶ cfu/ml. We recorded demographic variables, underlying diseases and severity of illness at ICU admission. On the day of pneumonia diagnosis, we registered temperature, leukocyte count, C-reactive protein, Sequential Organ Failure Assessment (SOFA) score, clinical pulmonary infection score (CPIS) and adequacy of empirical antimicrobial therapy.

RESULTS

In 231 episodes, clinical presentation, laboratory data, severity of illness, CPIS, the presence of bacteremia and radiological score did not differ among the three groups. ICU and hospital mortalities were also similar in the three groups. Factors independently associated with in-hospital mortality were age, SOFA score and inappropriate antimicrobial therapy. The bacterial burden in the QTA was not included in the model.

CONCLUSIONS

Quantification of tracheal aspirate samples may not be necessary in ventilated patients clinically suspected of having nosocomial pneumonia.

Rapid detection of Staphylococcus aureus in lower respiratory tract secretions from patients with suspected ventilator-associated pneumonia: evaluation of the Cepheid Xpert MRSA/SA SSTI assay

A preclinical evaluation was conducted to evaluate the performance of the Cepheid Xpert assay on 135 lower respiratory tract secretions for detection of methicillin-resistant Staphylococcus aureus and S. aureus. Compared with the quantitative culture, the sensitivity, specificity, and positive and negative predictive values were 99.0%, 72.2%, 90.7%, and 96.3%, respectively.

Is the gram stain useful in the microbiologic diagnosis of VAP? A meta-analysis

In a meta-analysis examining respiratory specimen Gram stain for diagnosis of ventilator-associated pneumonia, absence of bacteria on Gram stain had a high negative predictive value, but a positive Gram stain correlated poorly with organisms recovered in culture. Rapid and accurate diagnosis of ventilator-associated pneumonia (VAP) is a major challenge and no generally accepted gold standard exists for VAP diagnosis. We conducted a meta-analysis to examine the role of respiratory specimen Gram stain to diagnose VAP, and the correlation with final culture results. In 21 studies, pooled sensitivity of Gram stain for VAP was 0.79 (95% confidence interval [CI], .77-0.81; P < .0001) and specificity was 0.75 (95% CI, .73-.78; P < .0001). Negative predictive value of Gram stain for a VAP prevalence of 20%-30% was 91%, suggesting that VAP is unlikely with a negative Gram stain but the positive predictive value of Gram stain was only 40%. Pooled kappa was 0.42 for gram-positive organisms and 0.34 for gram-negative organisms, suggesting fair concordance between organisms on Gram stain and recovery by culture. Therefore, a positive Gram stain should not be used to narrow anti-infective therapy until culture results become available.

Trauma-associated pneumonia in adult ventilated patients

BACKGROUND

The clinical pulmonary infection score (CPIS) and bronchoalveolar lavage (BAL) are 2 tools that have been validated to diagnose pneumonia in critically ill patients. However, the role of the CPIS in diagnosing trauma-associated pneumonia (TAP) remains in question.

METHODS

This prospective observational study included all trauma patients who were ventilated for longer than 48 hours from September 2008 to September 2009. The CPIS and quantitative culture results from the BAL were collected and used to define pneumonia.

RESULTS

A total of 162 patients were identified. In all, 58 (35.8%) and 104 (64.2%) had a CPIS greater than 5 and a CPIS of 5 or less, respectively. There were 95 (58.6%) patients who had a BAL completed regardless of CPIS. There were 65 patients who met the bacteriologic definition of pneumonia (≥10(4) colonies/mL), for an overall TAP incidence of 40.1%.

CONCLUSIONS

The CPIS is unreliable as a clinical tool to predict a positive BAL at 10(4) or 10(5) or higher threshold. Therefore, BAL should be used for the diagnosis of TAP based on clinical rationale and not the CPIS.

Postoperative Fever

BACKGROUND

Fever is common in surgical patients. The list of potential causes is long and includes many noninfective etiologies.

CAUSES

Only about 40% of fever episodes in hospitalized patients are caused by infection. Any fever in a surgical patient is a cause for concern. New or continuing fever more than three days after surgery should raise a strong suspicion of persistent illness or a new complication. On rare occasions, these fevers can be attributed to potentially life-threatening occult infections, including acute cholecystitis, antibiotic-related pseudomembranous colitis, systemic candidiasis, or transfusion-related cytomegalovirus disease. A change in the microbiology of postoperative infections has also been noticed, characterized by a greater incidence of infections caused by methicillin-resistant Staphylococcus aureus, by polymicrobial flora, and by fungi.

TREATMENT

Control of nosocomial infections has become more challenging recently because of widespread bacterial resistance to antibiotics and to more frequent surgical indications in elderly patients at higher risk. Early recognition and appropriate treatment of these infections relieves anxiety, reduces hospital costs, and increases patient survival rates.

CONCLUSIONS

The workup and therapy for the individual patient may differ, depending on the underlying disease and clinical appearance and the clinician's suspicion for infection. Subsequent testing should be based on the clinical findings. Perhaps more money is wasted in the evaluation of early postoperative fever than on any other aspect of postoperative care.

Aportación del laboratorio de microbiología al diagnóstico de la neumonía asociada a la ventilación mecánica

The etiologic diagnosis of ventilator-associated pneumonia (VAP) should be considered as a microbiological emergency due to its impact on morbidity and mortality. Sampling of the lower respiratory tract (LRT) must be performed before starting or modifying antimicrobial therapy. Surveillance cultures in patients without criteria of VAP are not recommended. There is no evidence of any superiority of bronchoscopic over non-bronchoscopic sampling procedures, but quantitative bacterial cultures are essential to allow colonization to be differentiated from true infection of the LRT. Under these conditions, negative cultures practically rule out bacterial infection or, at least, identify patients who will not benefit from antibiotic therapy or who will require a very short course of treatment. Given that identification and antimicrobial susceptibility testing of microorganisms usually takes up to 3 or 4 days, rapid procedures that provide the clinician with useful information are essential. Rapid information, even if partial or less than perfect, is clearly better for the patient than a perfect but delayed report. Gram stain of LRT secretions is an immediate procedure that can guide management and it has a reasonable correlation with culture results. At present, new antibiogram procedures, performed on direct clinical samples, allow presumptive identification and information on susceptibility to commonly used antibiotics in less than 24 hours after sampling. The impact of using this procedure in clinical practice is currently under research.

Ventilator-associated pneumonia

PURPOSE OF REVIEW

This review summarises some of the notable papers on ventilator-associated pneumonia (VAP) from January 2003 to October 2004.

RECENT FINDINGS

Ventilator-associated pneumonia remains an important drain on hospital resources. All population groups are affected, but patients with VAP are more likely to be older, sicker, and male, with invasive medical devices in situ. Early VAP diagnosis is desirable to reduce VAP mortality and to retard emergence of multidrug-resistant microbes. This may be possible using preliminary culture results or intracellular organism in polymorphonuclear cells. In most intensive care units, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii are the commonest organisms isolated in VAP. However, causative organisms vary between and within hospitals. Consequently, individual intensive care units should develop empirical antibiotic policies to target the pathogenic bacteria prevalent in their patient populations. Preventative strategies aimed at reducing aerodigestive tract colonisation by pathogenic organisms, and also their subsequent aspiration, are becoming increasingly important. Educating medical staff about these simple measures is therefore pertinent. To reduce the occurrence of multidrug-resistant organisms, limiting the duration of antibiotic treatment to 8 days and antimicrobial rotation should be contemplated. Empirical therapy with antipseudomonal penicillins plus beta-lactamase inhibitors should be considered. If methicillin-resistant Staphylococcus aureus VAP is a possibility, linezolid may be better than vancomycin.

SUMMARY

Prevention remains the key to reducing VAP prevalence.