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The patient population at risk for opportunistic pulmonary infections has increased during the last decade. The spectrum of organisms causing opportunistic infections has also grown. With an ever broader list of potential diagnosis, a specific diagnosis of the cause of pulmonary disease becomes more important. Recent microbiologic advances have helped to facilitate the laboratory diagnosis of some of these agents. Immunoassays are available for the detection of antigen in nasopharyngeal secretions (respiratory syncytial virus, influenza) in serum (Cryptococcus species), and in urine (Legionella or Histoplasma species). Rapid-culture techniques are available for the culture and detection of various viruses, including cytomegalovirus. Molecular probes can now assist in the rapid identification of Mycobacterium tuberculosis and some fungi. In the near future, polymerase chain reaction-based techniques may assist in the detection of Pneumocystis carinii and Legionella, Chlamydia, Mycoplasma, and Mycobacteria species. An expeditious evaluation of pulmonary disease requires an understanding of the differential diagnosis of likely causes of pulmonary disease in specific immunosuppressed patient populations, an understanding of the most appropriate specimens to process for these diagnoses, and an understanding of the limitations (sensitivity and specificity) of these diagnostic tests. An understanding of the most appropriate specimens and tests in a given institution should allow for early, relatively specific treatment of many potentially life-threatening infections.
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PMID:The laboratory evaluation of opportunistic pulmonary infections. 859 23

Between February 1989 and June 1994 193 cases of acute community acquired pneumonia (PAC) which were of intermediate or great severity were admitted to two hospitals in the South West of France. These patients were explored using bronchofibroscopy (FB) with a protected brush (BP) and alveolar microlavage (MLBA) and quantitative cultures were performed, also there were other specimens taken in a regular fashion. The percentage of positive examinations was 60% for brushings (BP), 59% for MLBA and 21% for blood cultures and 16% for serological tests. An aetiology was determined in 137 cases (70.9%). The organisms recovered were Streptococcus pneumoniae (49.6%), gram negative bacilli (17.4%), Haemophilus influenzae (11.7%), Mycoplasma pneumoniae (4.4%), Mycobacterium tuberculosis (4.4%), Staphylococcus aureus (3.6%), Chlamydia pneumoniae (2.2%), Legionella pneumophila (0.7%), and various 5.8%. The overall mortality was 15% despite immediate antibiotics based on the likely organism in 88% of cases. The study of prognostic factors confirmed the Fine score system (determined a posteriori) which constitutes a useful and practical index determining the management of PAC. On the other hand the role of bacteriological documentation in improving the vital prognosis remains to be confirmed. If bronchofibroscopy has appeared to us as a safe and useful means of investigation, the management of these disease remains to specified. We suggest that its use is reserved for subjects with life threatening disease (a Fine score equal to or greater than 3) or for those patients who are likely to have unusual germs: failure of previous antibiotics, diabetes, malnourishment, cancer, airflow obstruction and inhalation.
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PMID:[Acute community-acquired pneumonia of moderate and grave severity investigated by bronchoscopy. Analysis of 193 cases hospitalized in a general hospital]. 871 Dec 37

Severe community-acquired pneumonia is a distinct clinical entity usually requiring intensive care unit (ICU) management. Among community-acquired pneumonia (CAP) requiring hospital admission, approximately 10% will receive ICU care and the mortality rate ranges from 21% to 47%. Host-related factors, clinical presentation, laboratory and radiographic findings on admission are useful in identifing the patient at high risk for fulminant pneumonia. The most common organisms responsible for severe CAP are Streptococcus pneumoniae, Haemophilus influenzae, gramnegative bacilli, Legionella pneumophilia and Staphylococcus aureus, but depending on host-related and epidemiological factors, the cause of severe CAP can be expanded to include tuberculosis, viruses, fungi, Pneumocystis carinii. An aggressive diagnostic approach that results in retrieval of adequate lower respiratory tract sample and incorporates both cultural and noncultural techniques is important in rapidly establishing the cause of pneumonia and allowing for the initiation of appriopiate and effective antimicrobial therapy. Empiric therapy should cover the most common organisms responsible for severe CAP in the community; however, every attempt should be made to continue to assess epidemiologically which organisms are responsible for pneumonia. Currently, studies focusing on bolstering the immune system are being conducted and may eventually be used in conjunction with antimicrobial to reduce the mortality of severe CAP.
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PMID:Severe community-acquired pneumonia. 877 79

Mechanically ventilated patients have a higher incidence of pneumonia and mortality than do nonventilated patients. Ventilator-associated pneumonia (VAP) is diagnosed clinically, by bronchoscopy or "blind" bronchoalveolar lavage (BAL) or protected specimen brush (PSB), and by quantitative endobronchial aspirates (QEA). VAP is usually caused by bacteria, but Legionella pneumophila, Mycobacterium tuberculosis, viruses, and fungi are also potential pathogens. Bacteria causing nosocomial pneumonia may be part of the patient's endogenous flora, originate from other patients, hospital personnel, or environmental sources. Pseudomonas aeruginosa, Acinetobacter spp, and Staphylococcus aureus are the most common causative agents in late-onset nosocomial pneumonia, and Streptococcus pneumoniae and Hemophilus influenzae are more commonly found in early-onset pneumonia. Aspiration appears to be the major route for the entry of bacteria into the lower respiratory tract. Host factors, oropharyngeal and gastric colonization, cross-infection, and complications from the use of antibiotics and nasogastric and endotracheal tubes increases the risk of bacterial VAP. A working knowledge of the epidemiology and strategies for prevention of VAP should reduce infection rates, morbidity, and mortality in critically ill patients.
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PMID:Nosocomial pneumonia in mechanically ventilated adult patients: epidemiology and prevention in 1996. 888 61

This document updates and replaces CDC's previously published "Guideline for Prevention of Nosocomial Pneumonia" (Infect Control 1982;3:327-33, Respir Care 1983;28:221-32, and Am J Infect Control 1983;11:230-44). This revised guideline is designed to reduce the incidence of nosocomial pneumonia and is intended for use by personnel who are responsible for surveillance and control of infections in acute-care hospitals; the information may not be applicable in long-term-care facilities because of the unique characteristics of such settings. This revised guideline addresses common problems encountered by infection-control practitioners regarding the prevention and control of nosocomial pneumonia in U.S. hospitals. Sections on the prevention of bacterial pneumonia in mechanically ventilated and/or critically ill patients, care of respiratory-therapy devices, prevention of cross-contamination, and prevention of viral lower respiratory tract infections (e.g., respiratory syncytial virus [RSV] and influenza infections) have been expanded and updated. New sections on Legionnaires disease and pneumonia caused by Aspergillus sp. have been included. Lower respiratory tract infection caused by Mycobacterium tuberculosis is not addressed in this document. Part I, "An Overview of the Prevention of Nosocomial Pneumonia, 1994, provides the background information for the consensus recommendations of the Hospital Infection Control Practices Advisory Committee (HICPAC) in Part II, Recommendations for Prevention of Nosocomial Pneumonia." Pneumonia is the second most common nosocomial infection in the United States and is associated with substantial morbidity and mortality. Most patients who have nosocomial pneumonia are infants, young children, and persons > 65 years of age; persons who have severe underlying disease, immunosuppression, depressed sensorium, and/or cardiopulmonary disease and persons who have had thoracoabdominal surgery. Although patients receiving mechanically assisted ventilation do not represent a major proportion of patients who have nosocomial pneumonia, they are at highest risk for acquiring the infection. Most bacterial nosocomial pneumonias occur by aspiration of bacteria colonizing the oropharynx or upper gastrointestinal tract of the patient. Because intubation and mechanical ventilation alter first-line patient defenses, they greatly increase the risk for nosocomial bacterial pneumonia. Pneumonias caused by Legionella sp., Aspergillus sp., and influenza virus are often caused by inhalation of contaminated aerosols. RSV infection usually occurs after viral inoculation of the conjunctivae or nasal mucosa by contaminated hands. Traditional preventive measures for nosocomial pneumonia include decreasing aspiration by the patient, preventing cross-contamination or colonization via hands of personnel, appropriate disinfection or sterilization of respiratory-therapy devices, use of available vaccines to protect against particular infections, and education of hospital staff and patients. New measures being investigated involve reducing oropharyngeal and gastric colonization by pathogenic microorganisms.
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PMID:Guidelines for prevention of nosocomial pneumonia. Centers for Disease Control and Prevention. 903 4

Clinical laboratories are increasingly receiving requests to perform nucleic acid amplification tests for the detection of a wide variety of infectious agents. In this paper, the efficiency of nucleic acid amplification techniques for the diagnosis of respiratory tract infections is reviewed. In general, these techniques should be applied only for the detection of microorganisms for which available diagnostic techniques are markedly insensitive or nonexistent or when turnaround times for existing tests (e.g., viral culture) are much longer than those expected with amplification. This is the case for rhinoviruses, coronaviruses, and hantaviruses causing a pulmonary syndrome, Bordetella pertussis, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Coxiella burnetii. For Legionella spp. and fungi, contamination originating from the environment is a limiting factor in interpretation of results, as is the difficulty in differentiating colonization and infection. Detection of these agents in urine or blood by amplification techniques remains to be evaluated. In the clinical setting, there is no need for molecular diagnostic tests for the diagnosis of Pneumocystis carinii. At present, amplification methods for Mycobacterium tuberculosis cannot replace the classical diagnostic techniques, due to their lack of sensitivity and the absence of specific internal controls for the detection of inhibitors of the reaction. Also, the results of interlaboratory comparisons are unsatisfactory. Furthermore, isolates are needed for susceptibility studies. Additional work remains to be done on sample preparation methods, comparison between different amplification methods, and analysis of results. The techniques can be useful for the rapid identification of M. tuberculosis in particular circumstances, as well as the rapid detection of most rifampin-resistant isolates. The introduction of diagnostic amplification techniques into a clinical laboratory implies a level of proficiency for excluding false-positive and false-negative results.
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PMID:Relevance of nucleic acid amplification techniques for diagnosis of respiratory tract infections in the clinical laboratory. 910 53

Procedures for the microbiological diagnosis of acute community-acquired pneumonia are based on the expected pathogens. Although a great variety of microorganisms are able to cause community-acquired pneumonia only a few pathogens play an important role in daily practice. The most important investigations are blood cultures and sputum cultures to detect bacteria like pneumococci, Haemophilus influenzae and Staphylococcus aureus as well as antibody tests for Mycoplasma pneumonia and Chlamydia pneumonia. According to anamnesis and clinic presentation tests such as for Legionella or viruses have to be added. Sometimes also rare pathogens have to be considered such as Coxiella burnetii, Leptospira, Hantaviruses, cryptococci or Chlamydia psittaci. The standard procedure for diagnosis of tuberculosis is the microscopical examination and the standardized culture in liquid and on solid media. Amplification methods such as PCR are also useful for a rapid diagnosis. However, the application of amplification procedures alone without culture is not recommended.
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PMID:[Community-acquired pneumonia--current status of pathogen diagnosis]. 920 30

This study was undertaken to examine quantitatively the risks to human health posed by heterotrophic plate count (HPC) bacteria found naturally in ambient and potable waters. There is no clear-cut evidence that the HPC bacteria as a whole pose a public health risk. Only certain members are opportunistic pathogens. Using the four-tiered approach for risk assessment from the National Academy of Sciences, hazard identification, dose-response modeling, and exposure through ingestion of drinking water were evaluated to develop a risk characterization, which estimates the probability of infection for individuals consuming various levels of specific HPC bacteria. HPC bacteria in drinking water often include isolates from the following genera: Pseudomonas, Acinetobacter, Moraxella, Aeromonas, and Xanthomonas. Other bacteria that are commonly found are Legionella and Mycobacterium. All these genera contain species that are opportunistic pathogens which may cause serious diseases. For example, the three nonfermentative gram-negative rods most frequently isolated in the clinical laboratory are (1) Pseudomonas aeruginosa, (2) Acinetobacter, and (3) Xanthomonas maltophilia. P. aeruginosa is a major cause of hospital-acquired infections with a high mortality rate. Aeromonas is sometimes associated with wound infections and suspected to be a causative agent of diarrhea. Legionella pneumophila causes 4%-20% of cases of community-acquired pneumonia and has been ranked as the second or third most frequent cause of pneumonia requiring hospitalization. The number of cases of pulmonary disease associated with Mycobacterium avian is rapidly increasing and is approaching the incidence of M. tuberculosis in some areas. Moraxella can cause infections of the eye and upper respiratory tract. The oral infectious doses are as follows in animal and human test subjects: P. aeruginosa, 10(8)-10(9); A, hydrophila, > 10(10); M. avium, 10(4)-10(7); and X. maltophilia, 10(6)-10(9). The infectious dose for an opportunistic pathogen is lower for immunocompromised subjects or those on antibiotic treatment. These bacteria have been found in drinking water at the following frequencies: P. aeruginosa, < 1%-24%; Acinetobacter, 5%-38%; X. maltophilia, < 1%-2%; Aeromonas, 1%-27%; Moraxella, 10%-80%; M. avium, < 1%-50%; and L. pneumophila, 3%-33%. These data suggest that drinking water could be a source of infection for some of these bacteria. The risk characterization showed that risks of infection from oral ingestion ranged from a low of 7.3 x 10(-9) (7.3/billion) for low exposures to Aeromonas to higher risks predicted at high levels of exposure to Pseudomonas of 9 x 10(-2) (98/100). This higher risk was only predicted for individuals on antibiotics. Overall, the evidence suggests that specific members of HPC bacteria found in drinking water may be causative agents of both hospital- and community-acquired infections. However, the case numbers may be very low and the risks represent levels generally less than 1/10,000 for a single exposure to the bacterial agent. Future research needs include (1) determining the seasonal concentrations of these bacteria in drinking water, (2) conducting adequate dose-response studies in animal subjects or human volunteers, (3) determining the health risks for an individual with multiple exposures to the opportunistic pathogens, and (4) evaluating the increase in host susceptibility conferred by antibiotic use or immunosuppression.
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PMID:Risk assessment of opportunistic bacterial pathogens in drinking water. 929 85

The death rate from pneumonia in Singapore has increased steadily over the past decade. The emerging respiratory pathogens may have contributed to this increased mortality. New challenges have arisen from changes in the characteristics of the host and the susceptibilities of the various pathogens to antibiotics. There has been a 60-fold increase in the incidence of penicillin resistance in Streptococcus pneumoniae, the major pathogen for community-acquired pneumonia (CAP). Gram-negative bacilli are the major pathogens in severe CAP with Klebsiella pneumonia being the most frequently isolated organism. There has been a small increase in the number of cases of Legionnaire's disease and a marked increase in the incidence of melioidosis. While the overall incidence of tuberculosis has been unchanged, the number of non-residents with tuberculosis has doubled in the past 5 years. The rising prevalence of human immunodeficiency Virus infection is reflected in an increasing number of apparently healthy young men who present with CAP caused by Pneumocystis carinii. There is increasing resistance to antibiotics among gram-negative bacilli and Staphylococcus aureus, the dominant pathogens in hospital-acquired pneumonia. New strategies are urgently needed to prevent the emergence of pathogens in the hospital environment which may be resistant to all known antibiotics.
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PMID:Emerging pathogens for pneumonia in Singapore. 949 74

International movement of individuals, populations, and products is one of the major factors associated with the emergence and reemergence of infectious diseases as the pace of global travel and commerce increases rapidly. Travel can be associated with disease emergence because (1) the disease arises in an area of heavy tourism, (2) tourists may be at heightened risk because of their activities, or (3) because they can act as vectors to transport the agent to new areas. Examples of recently recognized diseases with relationship to travel include HIV, Legionnaire's disease, cyclosporiasis, Vibrio cholerae O139 Bengal, hantavirus, and variant Creutzfeldt-Jacob disease. Reemerging diseases include dengue fever, malaria, cholera, schistosomiasis, leptospirosis, and viral hemorrhagic fevers. In addition, tuberculosis, drug-resistant shigellosis, and cholera have been major concerns in refugee and migrant populations. Because of the unique role of travel in emerging infections, efforts are underway to address this factor by agencies such as the CDC, WHO, the International Society of Travel Medicine, and the travel industry.
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PMID:Emerging infectious diseases and travel medicine. 949 41


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