Aerobic and anaerobic microbiology of empyema. A retrospective review in two military hospitals

A 30-month experience of thoracic empyema in a tertiary hospital: emphasis on differing bacteriology and outcome between the medical intensive care unit (MICU) and medical ward

OBJECTIVES

To analyze the causative pathogens and outcomes of patients with thoracic empyema admitted to the medical intensive care unit (MICU) and medical ward.

METHODS

We prospectively studied the empyemic patients in the MICU and retrospectively analyzed the medical records of empyemic patients in the medical ward treated in a tertiary university hospital from April 2001 to September 2003.

RESULTS

During this period, 116 patients in the medical ward and 78 patients in MICU had complicated parapneumonic effusions or empyemas. Effusion cultures were positive in 164 patients (85%); a total of 147 and 78 microorganisms were isolated from the 106 medical ward patients and 58 MICU patients, respectively. No matter whether medical ward or MICU patients, aerobic gram-negative organisms were the most common bacteria in positive-culture effusions (110, 67%). Klebsiella pneumoniae (14, 24%) was the predominant pathogen among the MICU patients, and Streptococcus spp. (28, 26%) was the main pathogen among the medical ward patients. Compared with these positive-culture empyemic patients in the medical ward, MICU patients had a significantly higher percentage of aerobic gram-negative organism infections (P = 0.034) and a higher infection-related mortality rate (P = 0.01).

CONCLUSION

The mortality and predominant pathogens in patients with complicated parapneumonic effusions or thoracic empyemas in the medical ward and MICU were different. The increasing gram-negative pathogens in empyemas have become an urgent problem.

[Treatment of pleural empyema]

Pleural empyema remains a frequently encountered clinical problem and is responsible for significant morbidity and mortality worldwide. Its diagnosis may be difficult; delays in diagnosis and treatment may contribute to morbidity, complications, and mortality. The management of parapneumonic effusion and empyema depends on timely, stage-dependent therapy and the underlying etiology. Thoracentesis and antibiotics remain the cornerstones of treatment in stage I disease. In the early fibrinopurulent phase (stage II) thoracoscopic methods should be considered. As treatment strategy for this stage, fibrinopurulent pleural empyema entails thorough debridement of multiloculated collections from the pleural cavity by video-assisted thoracic surgery. After evacuation of multilocular effusions and the removal of fibrin deposits with drainage by two intercostal chest tubes, irrigation treatment helps to achieve clarity of the pleural discharge. Open thoracotomy and decortication are reserved for organized, multiloculated empyema with lung entrapment (stage III disease). Early drain removal may lead to rapid symptomatic recovery and complete resolution.

Different bacteriology and prognosis of thoracic empyemas between patients with chronic and end-stage renal disease

BACKGROUND

Bacterial infections are a well-documented complication in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). However, there are no previous studies of the empyemas that can develop in these patients.

METHODS

This retrospective study investigated the bacteriology and outcomes of empyema in stage 4 CKD (predialysis) and ESRD patients receiving long-term dialysis and treated in a tertiary university hospital from January 2001 to March 2006.

RESULTS

Eighty-four stage 4 CKD patients and 40 ESRD patients had empyemas. Most empyemas (n = 77, 62%) were secondary to pneumonia. Empyema culture findings were positive in 102 patients (82%): 87 microorganism were isolated in pleural fluid from 67 stage 4 CKD patients, and 39 microorganisms were isolated in pleural fluid from 35 ESRD patients. Aerobic Gram-negative organisms (n = 58, 67%), especially Klebsiella pneumoniae (n = 20, 34%), were the predominant pathogens in stage 4 CKD patients; aerobic Gram-positive organisms (n = 21, 54%), especially Staphylococcus aureus (n = 14, 67%), were the main pathogens in ESRD patients. Compared to stage 4 CKD patients, ESRD patients had a significantly higher percentage of catheter infections (p = 0.002) and aerobic Gram-positive organism bacteremia (p = 0.001), as well as a lower aerobic Gram-negative organism infection rate (p < 0.001) and a lower infection-related mortality rate (p = 0.022).

CONCLUSION

Stage 4 CKD patients and ESRD patients with empyema have different causative pathogens and outcomes. In ESRD patients, the dialysis catheter or the dialysis process appear to alter the microbiological flora responsible for empyema. This finding has clinical implications that clinicians need to consider.

Pleural Fluid PCR Method for Detection of Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae in Pediatric Parapneumonic Effusions

BACKGROUND

Parapneumonic effusions cause significant morbidity and mortality despite current developments in diagnostic and therapeutic approaches. Causative microorganisms may remain unidentified in a significant number of patients by cultures and Gram smears. Polymerase chain reaction (PCR) is a molecular technique for the detection of causative bacteria; however, its efficiency in pleural fluids is less known.

OBJECTIVES

The present study was performed to compare the efficiency of PCR in the detection of the three most common organisms (Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae) with conventional methods.

METHODS

Twenty-eight consecutive patients with parapneumonic pleural effusions were studied. On admission, pleural fluid samples were obtained for Gram staining, routine culture and PCR analysis for S. aureus, S. pneumoniae and H. influenzae.

RESULTS

PCR analysis allowed detection of 11 microorganisms in 10 patients (35.7%), whereas pleural fluid cultures detected the etiological agent in only 2 (7.1%). S. pneumoniae was the most frequent agent.

CONCLUSIONS

Pleural fluid cultures may have low diagnostic yields, partly due to prior antibiotic use. Pleural fluid PCR analysis may improve the etiologic diagnosis in parapneumonic pleural effusions, with technical advances leading to higher yields than obtained in this study.

Anaerobic microbiology in 198 cases of pleural empyema: a Bulgarian study

The aim of the study was to evaluate the incidence of anaerobic bacteria in 198 patients with pleural empyema and the susceptibility of isolates to eight antibacterial agents. Isolates were identified by the Crystal anaerobes identification system, API System rapid ID 32 A and/or routine methods. Susceptibility was tested by Sceptor MIC system for anaerobic bacteria and limited agar dilution method. Anaerobic bacteria were found in 74.2% of the patients and included 247 strains within 21 genera. The predominant anaerobes were Gram-positive anaerobic cocci (52 isolates), Fusobacterium (51), microaerophilic streptococci (24), Prevotella (19) and Bacteroides species (11). Common species/groups were Fusobacterium nucleatum (in 27.2% of specimens yielding anaerobes), Micromonas micros (8.2%), Finegoldia magna (7.5%), Bacteroides fragilis group (6.8%), Peptostreptococcus anaerobius (6.1%) and F. necrophorum (5.4%). No resistance to chloramphenicol and ampicillin/sulbactam was detected. The susceptibility rates of Gram-negative anaerobic isolates to penicillin, cefoxitin, clindamycin, clarithromycin, metronidazole and tetracycline were 63.8%, 90.2%, 87.8%, 58.6%, 98.8% and 71%, and those of Gram-positive anaerobes were 79.2%, 100%, 84.3%, 68.4%, 41.9% and 75%, respectively. The wide diversity of isolated anaerobic genera and species and the susceptibility patterns of the isolates emphasize the role of the anaerobic microbiology in cases of pleural empyema.

Colonization of dental plaque by respiratory pathogens in dependent elderly

Pneumonia can be a life-threatening infection, especially in the elderly, and it is a significant cause of morbidity and mortality. The purpose of this study was to assess the existence of oral infectious pathogens potentially causing the respiratory disease in the dependent elderly. The dental plaques of 138 dependent elderly were examined to identify microorganisms by the culture method. Twenty-one species of microorganisms were detected in the dental plaques in this study. In 89 cases out of 138 (64.5%), potential respiratory pathogens colonized in the dental plaques of the dependent elderly. The results of the present study revealed that bacteria that commonly cause respiratory infection colonized in dental plaques of the aged, dependent subjects. Therefore, dental plaques must be considered a specific reservoir of colonization and subsequent aspiration pneumonia in dependent elderly.

Antianaerobe activity of ceftobiprole, a new broad-spectrum cephalosporin

Agar dilution testing of 463 anaerobes showed most Gram-positive beta-lactamase-negative strains (other than some Clostridium difficile and Peptostreptococcus anaerobius), as well as both beta-lactamase-positive and beta-lactamase-negative strains of Fusobacterium nucleatum, to have ceftobiprole MIC values of < or =0.016 to 4 microg/mL. Ceftobiprole was less active against beta-lactamase-positive Gram-negative bacilli, especially the members of the Bacteroides fragilis group. Like ceftobiprole, piperacillin was active mainly against beta-lactamase-negative strains, though MIC values for piperacillin were often 1 to 2 dilutions higher than for ceftobiprole. Carbapenems had MIC values < or =4 microg/L against all except some C. difficile and 2 strains of B. fragilis. All strains were susceptible to metronidazole, and all bacteria, except C. difficile and a single Bacteroides distasonis strain, were susceptible to chloramphenicol. Clindamycin resistance was seen in most anaerobe groups, whereas high moxifloxacin MICs were found mainly among the B. fragilis and Prevotella groups, and a few C. difficile and F. nucleatum strains.

An urgent problem of aerobic gram-negative pathogen infection in complicated parapneumonic effusions or empyemas

OBJECTIVES

Complicated parapneumonic effusion or empyema is a troublesome disease with a high mortality. The most common involved microorganisms seem to have changed over recent decades, influenced by the introduction of new antibiotics, and the increase of immunocompromised hosts, and the elderly population. More epidemiological studies on the current bacteriology are needed to help us to empirically select adequate antibiotics.

DESIGN

A retrospective study via chart review in a university-affiliated tertiary medical center was conducted to assess the underlying bacterial pathogens and outcome of patients with complicated parapneumonic effusions or empyemas.

RESULTS

During the 43-month study period (from December 2000 to June 2004), 304 patients were diagnosed with complicated parapneumonic effusions or empyemas and the mortality of these patients was 23% (69/304). Among these 304 patients, a total of 292 microorganisms were cultured from the pleural fluid samples of 207 patients (to yield a positive microbiological culture rate of 68% (207/304). Isolated bacteria included aerobic Gram-negative bacteria (n=129), aerobic Gram-positive bacteria (n=105), anaerobic bacteria (n=51), and M. tuberculosis (n=7). Of these aerobic bacterial infections, Gram-negative bacteria were isolated more frequently from the older population and involved a significantly higher mortality rate and longer stay, compared to those with other bacteria (p=0.001 and p<0.001 respectively).

CONCLUSION

The increasing incidence of infection with aerobic Gram-negative pathogens may cause more critical conditions in complicated parapneumonic effusions or empyemas.

Clinical characteristics and outcomes of empyema thoracis in 117 patients: a comparative analysis of tuberculous vs. non-tuberculous aetiologies

BACKGROUND

Empyema thoracis remains a major problem in developing countries. Clinical outcomes in tuberculous empyema are generally believed to be worse than in non-tuberculous aetiologies because of the presence of concomitant fibrocavitary parenchymal disease, frequent bronchopleural fistulae and poor general condition of patients. We performed a prospective study over a 2-year period with the objective of comparing the clinical characteristics and outcomes of patients with tuberculous vs. non-tuberculous empyema.

METHODS

Prospective study of all cases of non-surgical thoracic empyema seen at a tertiary care centre in North India over a 2-year period. A comparative analysis of clinical characteristics, treatment modalities and outcomes of patients with tuberculous vs. non-tuberculous empyema was carried out. Factors associated with poor outcomes were analysed using multivariate logistic regression.

RESULTS

One hundred and seventeen cases of empyema were seen in the study period of which 95 had non-tuberculous and 41 had tuberculous empyema. Malnutrition and bronchopleural fistulae (BPF) were more common and duration of symptoms longer in the tuberculous empyema group. Time to resolution of fever, duration of pleural drainage and pleural thickening >2 cm were significantly greater as well. Eight (10.5%) patients with non-tuberculous empyema and four (9.8%) with tuberculous empyema succumbed. Presence of a BPF was significantly associated with poor outcomes on multivariate logistic regression analysis.

CONCLUSIONS

Tuberculous empyema remains a common cause of thoracic empyema in India though it ranked second amongst all causes of empyema after community acquired lung infections in this study. Tuberculous empyema is associated with longer duration of symptoms, greater duration of pleural drainage and more residual pleural fibrosis.

The Bacteriology of Pleural Infection by Genetic and Standard Methods and Its Mortality Significance

BACKGROUND

Antibiotic choices for pleural infection are uncertain as its bacteriology is poorly described.

METHODS

Pleural fluid from 434 pleural infections underwent standard culture and a screen for bacteria by amplification and sequencing of bacterial 16S ribosomal RNA gene.

RESULTS

Approximately 50% of community-acquired infections were streptococcal, and 20% included anaerobic bacteria. Approximately 60% of hospital-acquired infections included bacteria frequently resistant to antibiotics (methicillin-resistant Staphylococcus aureus, 25%; Enterobacteriaceae, 18%; Pseudomonas spp., 5%, enterococci, 12%). Mortality was increased in hospital-acquired infection (hospital, 17/36 [47%]; community, 53/304 [17%]; relative risk, 4.24; 95% confidence interval, 2.07-8.69; p < 0.00001; chi(2), 1 df = 17.47) and in gram-negative (10/22 [45%]), S. aureus (15/34 [44%]), or mixed aerobic infections (13/28 [46%]), compared with streptococcal infection (23/137 [17%]) and infection including anaerobic bacteria (10/49 [20%]; p < 0.00001, chi(2), 4 df = 23.35).

CONCLUSION

Pleural infection differs bacteriologically from pneumonia and requires different treatment. Antibiotics for community-acquired infection should treat aerobic and anaerobic bacteria. Hospital-acquired, gram-negative S. aureus and mixed aerobic infections have a high mortality rate.

The Approach to the Patient with a Parapneumonic Effusion

Parapneumonic effusion is a common clinical problem, and those that go on to develop pleural infection have high morbidity and mortality. The process of pleural infection evolution involves changes in pleural physiology that are increasingly being elucidated and understood. The microbiology of pleural infection has changed over recent years, with clear differences emerging between hospital- and community-acquired infections. Using biochemical surrogates of infection, chest drainage can be undertaken rationally for those who do not respond to antibiotics alone. Recent data suggest that fibrinolytics do not influence outcomes in pleural infection. The optimal type and timing of surgery remain controversial.

Colonisation on the tongue surface by respiratory pathogens in residents of a nursing home--a pilot study

OBJECTIVE

The morbidity and mortality of the dependent elderly that result from aspiration pneumonia have been recognised as a major geriatric health problem. The tongue has an extremely large surface area and due to its papillary structure can retain considerable quantities of food, and thus can support and harbour a large bacterial population. The purpose of this study was to gain more information on the microflora of the tongue surface and to assess the existence of oral infectious pathogens potentially causing respiratory disease in nursing home residents.

SUBJECTS AND METHODS

The tongue bacterial flora of 69 nursing home residents were examined to identify microorganisms by the culture method.

RESULTS

Thirteen species of microorganisms were detected from the tongue in this study. In 41 of 69 subjects (59%), potential respiratory pathogens, had colonised the tongue surface.

CONCLUSION

The results of the present study revealed that bacteria that commonly cause respiratory infection colonised the tongue of nursing home residents, suggesting that it may function as a reservoir of potential respiratory pathogens to facilitate colonisation on the oropharynx.

The changing pathogens of complicated parapneumonic effusions or empyemas in a medical intensive care unit

OBJECTIVES

To assess the incidence, pathogens, and outcome of complicated parapneumonic effusions or empyemas in a medical intensive care unit (MICU) patients with pleural effusions.

DESIGN AND SETTING

Prospective study of febrile MICU patients with pleural effusion carried out in a tertiary care hospital between April 2001 and September 2003.

PATIENTS

The study included 175 patients with a temperature above 38 degrees for more than 8 h with evidence of pleural effusion confirmed by chest radiography and ultrasound.

INTERVENTION

Routine thoracentesis and effusion cultures.

RESULTS

The prevalence of complicated parapneumonic effusions or thoracic empyemas in febrile MICU patients with pleural effusions was 45% (78/175). A total of 78 micro-organisms were isolated from the pleural fluid of 58 patients (positive microbiological culture 74%) including aerobic Gram-negative (n=45), aerobic Gram-positive (n=23), anaerobic (n=5), Myobacterium tuberculosis (n=3), and Candida (n=2). The infection-related mortality rate of complicated parapneumonic effusions or empyemic patients in the MICU was 41% (32/78).

CONCLUSION

The development of complicated parapneumonic effusions or thoracic empyemas in MICU patients is a high-mortality disease. The increasing incidence of aerobic Gram-negative pathogens in empyema has become a more urgent problem.

Diagnosis and Management of Infectious Pleural Effusion

Pleural infection remains a common illness, with a high morbidity and mortality. The development of frank empyema from a simple exudative pleural effusion is a result of biochemical changes within the pleural space in response to bacterial invasion. These changes can be used in the diagnosis of pleural infection and used to predict which patients will require intercostal drainage for resolution of infection. Recent large trials in empyema have further advanced our knowledge of microbiologic patterns, informing important decisions about empiric antibacterial therapy. Diagnosis of pleural infection relies on high clinical suspicion in association with clinical features, radiology, and pleural fluid characteristics. Treatment of pleural infection is based upon accurate and often empiric choice of antibacterial agents, intercostal drainage in certain contexts, and appropriate surgical referral. Intrapleural thrombolytic therapy is not currently recommended for the treatment of pleural infection, on the basis of evidence from the largest randomized trial in empyema to date.

The etiology of extensive pleural effusions with troublesome clinical course among children

CONTEXT

In São Paulo, pneumonia is the main infectious cause of death among children. Parapneumonic pleural effusion is a possible complication and has to be treated surgically when the patient does not respond to antibiotics.

OBJECTIVE

Assessment of the etiology of complicated parapneumonic pleural effusions that needed surgical intervention.

TYPE OF STUDY

Retrospective study.

SETTING

University hospital of the University of São Paulo.

METHOD

Analysis of 4,000 files on children hospitalized with pneumonia from November 1986 to November 1996 had shown that 115 of these children presented a total of 117 cases of pleural empyema that required surgical procedures. The children's clinical condition was assessed in relation to radiological findings and to their nutrition and immunization status. Previous antimicrobial therapy and pleural effusion bacterioscopy were also evaluated.

RESULTS

Streptococcus pneumoniae was the agent found most commonly, as frequently in blood cultures as in pleural effusions.

DISCUSSION

Data on vaccination coverage, birth weight and nutritional status are analyzed and compared to other publications. We observed that pleural effusion has a high potential for discomfort, and in most cases it is not a complication of the first pulmonary disease episode. Previous use of antibiotics interfered with culture positivity. The agent most frequently found was Streptococcus pneumoniae, which is in accordance with the findings from other authors. Nonetheless, the antibiotics used to treat the patients after the procedure were the same used in non-complicated pneumonias, which has led us to conclude that the worse outcome in this cases was not due to drug resistance.

CONCLUSION

The bacteriological profile in our series of complicated pneumonia cases was similar to what has been described for non-complicated pneumonia cases. Future studies will be necessary to determine why these children presented a worse outcome.

Surgical versus nonsurgical treatment of empyema thoracis: an outcomes analysis

BACKGROUND

Empyema thoracis (ET) is associated with substantial morbidity and mortality. The optimal means for draining the pleural space remains controversial but there may be increasing bias for less invasive strategies. This study compared outcome after a nonsurgical versus a surgical approach to ET.

METHODS

Patients with ET over a 10-year period (n = 93) were reviewed and stratified into nonsurgical (thoracentesis and/or closed tube thoracostomy) and surgical (thoracotomy, decortication, and/or open window thoracostomy) groups based on pleural drainage techniques. Hospital course was analyzed except when altered by death (n = 12), noncompliance (n = 3), or severe comorbidities (n = 3).

RESULTS

Seventy-five patients were stratified into nonsurgical (n = 32) and surgical (n = 43) groups. Demographics, comorbidities, signs and symptoms, and causative organisms were similar between groups. Mortality did not significantly differ in nonsurgical (16%) versus surgical (10%) groups (P = 0.7). Although delay in diagnosis and number of therapeutic interventions were nearly identical, the time to definitive therapy was longer in the surgical versus the nonsurgical group (18 +/- 3.8 versus 8.5 +/- 3.8 days, P = 0.023). The time to discharge after definitive therapy (20.0 +/- 3.5 versus 35.6 +/- 14.0 days, P < 0.001), and overall hospital stay (40.6 +/- 5.3 versus 47.4 +/- 15 days, P = 0.01) was significantly decreased in the surgical versus nonsurgical treatment groups, respectively.

CONCLUSION

The treatment of ET is complex. Failure to adequately evacuate the pleural space and/or persistent signs of infection should prompt surgical intervention. Surgical therapy is preferred for advanced stages of ET. Delaying definitive surgical treatment is largely responsible for prolonging hospital course.

Incidence and etiologies of complicated parapneumonic effusions in children, 1996 to 2001

BACKGROUND

The incidence and causative organisms associated with complicated parapneumonic effusions in children with community-acquired pneumonia are likely to have changed during the past several years.

METHODS

Data regarding clinical and laboratory features were abstracted retrospectively from medical records of 76 subjects with complicated parapneumonic effusions at a tertiary children's hospital from 1996 through 2001. Incidence rates per 10 000 hospital discharges and per 1000 patients with nonviral pneumonia were calculated.

RESULTS

Etiologic organisms were Streptococcus pneumoniae (31 subjects), Staphylococcus aureus (7), Streptococcus pyogenes (5), Abiotrophia sp. (1) and no culture-confirmed agent (32). The annual incidence of complicated parapneumonic effusions per 10 000 discharges progressively increased from 4.5 in 1996 to 25.0 in 1999 (P = 0.0001), then declined to 10.1 in 2001 (P = 0.03). Similarly the incidence per 1000 cases of nonviral pneumonia increased from 2.9 in 1996 to 11.0 in 1999 (P = 0.003) and then declined to 4.8 in 2001 (P = 0.053). Whereas S. pneumoniae was the leading confirmed etiology in each year, the proportion of cases caused by Staphylococcus aureus increased from 6% in 1996 to 2000 (all of which were methicillin-susceptible) to 30% in 2001 (all methicillin-resistant; P = 0.04).

CONCLUSIONS

The incidence of complicated parapneumonic effusions in children with community-acquired pneumonia increased from 1996 to 1999 and then declined concomitant with the introduction of the pneumococcal conjugate vaccine. Although cases caused by S. pneumoniae have decreased, community onset methicillin-resistant Staphylococcus aureus has emerged as a cause of pneumonia with complicated effusions in children.

Sex differences in the effects of muramyl dipeptide and lipopolysaccharide on locomotor activity and the development of behavioral tolerance in rats

Administration of bacterial agents, such as muramyl dipeptide (MDP) or lipopolysaccharide (LPS), induces a number of illness symptoms including decreased locomotor activity and weight loss. This study provides a detailed multivariate assessment of the effects of repeated exposures of various doses of MDP and LPS, alone and in combination, on various aspects of locomotion in male and female rats. Animals were given a single intraperitoneal injection of either MDP (0.8 or 1.6 mg/kg), LPS (100 or 200 microg/kg), a combination of MDP and LPS (0.8 mg/kg and 100 microg/kg, respectively), or vehicle on Days 1, 4, and 7. Two hours after each injection, locomotor activity was recorded for 30 min in an automated open-field. Both doses of LPS and the high dose of MDP produced significant decrements in locomotor activity in male and female rats, with tolerance becoming evident over repeated administrations, although LPS decreased activity more robustly than MDP. Sex differences were evident in the combined effects of MDP and LPS. Together, MDP and LPS reduced male activity levels in an additive manner but significantly potentiated both horizontal and vertical activity decrements in females. In addition, the rate of behavioral tolerance development to repeated bacterial injections was significantly higher in females than in males. These findings provide evidence for sex differences in the actions of MDP and LPS on various aspects of locomotor activity and in the development of behavioral tolerance to infection.

Colonization of denture plaque by respiratory pathogens in dependent elderly

OBJECTIVES

Recently, there has been a resurgence of interest in the interactions between oral conditions and a number of prevalent systemic diseases. The morbidity and mortality of the dependent elderly that result from aspiration pneumonia have been recognized as a major geriatric health problem. The purpose of this study was to gain more information on the microflora of plaque on dentures and to assess the existence of oral infectious pathogens potentially causing the respiratory disease in the dependent elderly.

SUBJECTS AND METHODS

The denture bacterial flora of 50 dependent elderly were examined to identify microorganisms by the culture method.

RESULTS

18 species of microorganisms were detected in denture plaque in this study. A variety of pathogens with the potential to cause respiratory infection pathogens colonized on the dentures of dependent elderly.

CONCLUSION

The results of the present study revealed that bacteria that commonly cause respiratory infection colonized on the dentures of dependent elderly, suggesting that denture plaque may function as a reservoir of potential respiratory pathogens to facilitate colonization on the oropharynx.

A 10-year experience with bacteriology of acute thoracic empyema: emphasis on Klebsiella pneumoniae in patients with diabetes mellitus

STUDY OBJECTIVES

To provide an updated evaluation of the bacteriology of acute thoracic empyema for more efficacious treatment.

DESIGN

: The medical and microbiological records of all patients who received a diagnosis of acute thoracic empyema were reviewed. Based on the bacteria isolated from the pleural fluid, the patients were classified into the following four groups: aerobic or facultative Gram-positive; aerobic Gram-negative; anaerobic; and mixed.

SETTING

A university-affiliated tertiary medical center.

PATIENTS AND METHODS

From January 1989 to December 1998, 171 patients with a diagnosis of acute thoracic empyema were treated. A comparative analysis of the isolates from pleural effusions, the mean length of hospital stay, the mean duration of chest tube drainage, the mean duration between the onset of symptoms and the establishment of diagnosis, treatment efficacy, and the need for subsequent intervention was performed.

RESULTS

A total of 163 microorganisms were isolated from the pleural fluid of 139 patients. These patients were classified according to the following types of isolates: aerobic or facultative Gram-positive (n = 47); aerobic Gram-negative (n = 59); anaerobic (n = 14); and mixed (n = 19). Klebsiella pneumoniae was the most commonly isolated pathogen (24. 4%) and was strongly associated with a diagnosis of diabetes mellitus. The mortality rate of patients with aerobic Gram-negative bacilli isolated was the highest (22.0%), followed by those with mixed pathogens isolated (15.7%), aerobic or facultative Gram-positive (6.4%), and anaerobic (0%).

CONCLUSIONS

The increasing incidence of acute thoracic empyema caused by Gram-negative bacilli, especially by K pneumoniae, has become an increasing problem. The isolation of aerobic Gram-negative bacilli or multiple pathogens from pleural fluid is associated with a poor prognosis and indicates a need for more aggressive antimicrobial chemotherapy.

Pyogenic lung infections: factors for predicting clinical outcome of lung abscess and thoracic empyema

Lung abscess and thoracic empyema continue to cause significant morbidity and mortality despite appropriate antibiotic therapy and various options for drainage of empyema. Multiple factors, including the patient's general state of health, the presence of underlying disease, the virulence of the pathogen responsible, and the promptness of drainage of empyema, appear to dictate the clinical outcome. However, the available data are derived from uncontrolled, retrospective studies and the high morbidity and mortality rates underscore the need for large prospective studies to better evaluate factors that may predict the clinical outcome of these conditions.

Clinical management of the patient with pleural effusion

Pleural effusion is a frequent medical problem with a wide span of different causes. We wish to highlight the clinical management of the patient with pleural effusions but anatomic, physiologic and diagnostic management of the main pleural diseases will also be considered.

Unusual manifestations of invasive pneumococcal infection

Unusual pneumococcal infections occurred frequently in the preantibiotic age but rapidly declined with the advent of the antibiotic era. Unfortunately, the morbidity and mortality associated with invasive pneumococcal disease remain high despite antibiotic therapy and monumental advances in medical technology. The incidence of invasive pneumococcal disease has increased recently because of the onset of the human immunodeficiency virus (HIV) epidemic and the emergence of antibiotic-resistant pneumococcus. Robert Austrian described the clinical triad of pneumococcal pneumonia, meningitis, and endocarditis, a syndrome that now bears his name. Although seen infrequently today, unusual manifestations of pneumococcal infection such as those Austrian reported still occur. A review of these cases is warranted because, as drug-resistant organisms continue to emerge worldwide, more unusual pneumococcal infections will be seen. Streptococcus pneumoniae is responsible for a remarkable array of disease processes; our literature review uncovered 95 different types of unusual pneumococcal infections representing 2,064 cases. Examples of these infections included pancreatic and liver abscesses, aortitis, gingival lesions, phlegmonous gastritis, inguinal adenitis, testicular and tubo-ovarian abscesses, and necrotizing fasciitis. We also reviewed predisposing underlying illnesses and conditions. Alcoholism, HIV infection, splenectomy, connective tissue disease, steroid use, diabetes mellitus, and intravenous drug use remain common risk factors for invasive pneumococcal infections. Currently, multidrug-resistant S. pneumoniae remains susceptible to vancomycin and several new third-generation fluoroquinolones. As what some fear will be a possible postantibiotic era approaches, clinicians must be able to recognize and manage unusual pneumococcal infections.

Role of oral bacteria in respiratory infection

An association between oral conditions such as periodontal disease and several respiratory conditions has been noted. For example, recent evidence has suggested a central role for the oral cavity in the process of respiratory infection. Oral periodontopathic bacteria can be aspirated into the lung to cause aspiration pneumonia. The teeth may also serve as a reservoir for respiratory pathogen colonization and subsequent nosocomial pneumonia. Typical respiratory pathogens have been shown to colonize the dental plaque of hospitalized intensive care and nursing home patients. Once established in the mouth, these pathogens may be aspirated into the lung to cause infection. Other epidemiologic studies have noted a relationship between poor oral hygiene or periodontal bone loss and chronic obstructive pulmonary disease. Several mechanisms are proposed to explain the potential role of oral bacteria in the pathogenesis of respiratory infection: 1. aspiration of oral pathogens (such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, etc.) into the lung to cause infection; 2. periodontal disease-associated enzymes in saliva may modify mucosal surfaces to promote adhesion and colonization by respiratory pathogens, which are then aspirated into the lung; 3. periodontal disease-associated enzymes may destroy salivary pellicles on pathogenic bacteria to hinder their clearance from the mucosal surface; and 4. cytokines originating from periodontal tissues may alter respiratory epithelium to promote infection by respiratory pathogens.

Pyogenic lung infections

Pyogenic lung infections still occur despite the availability of effective antibiotics for the treatment of patients with acute bacterial pneumonia. Our understanding of the pathogenesis and management of these conditions has steadily improved over the past few decades, although some areas remain obscure. The effect of HIV infection on the incidence of pyogenic lung infections remains largely unknown, and large studies are required to evaluate this. Burkholderia (formerly Pseudomonas) cepacia strains are now recognized as important respiratory pathogens in patients with cystic fibrosis, and the high transmissibility of some strains, combined with their inherent multiple antibiotic resistance, are continuing causes for concern.

Predicting factors for outcome of tube thoracostomy in complicated parapneumonic effusion for empyema

STUDY OBJECTIVES

To determine the predicting factors for outcome of tube thoracostomy in patients with complicated parapneumonic effusion (CPE) or empyema.

DESIGN AND SETTINGS

Retrospective chart review over a 55-month period at a tertiary referred medical center.

PATIENTS AND MEASUREMENTS

The medical charts of patients with empyema or CPE were reviewed. Data including age, gender, clinical symptoms, important underlying diseases, leukocyte count, duration of preadmission symptoms, interval from first procedure to second procedure, the time from first procedure to discharge (recovery time), the amount of effusion drained, administration of intrapleural streptokinase, chest tube size and position, loculation of pleural effusion, and characteristics and culture results of pleural effusion were recorded and compared between groups of patients with successful and failed outcome of tube thoracostomy drainage.

RESULTS

One hundred twenty-one patients were selected for study. One hundred of these patients had received tube thoracostomy drainage with 53 successful outcomes and 47 failed outcomes of chest tube drainage. Nineteen patients received decortication directly, and the other two received antibiotics alone. Univariate analysis showed that pleural effusion leukocyte count, effusion amount, and loculation of pleural effusion were significantly related to the outcome of chest tube drainage. Multiple logistic regression analysis demonstrated that loculation and pleural effusion leukocyte count < or = 6,400/uL were the only independent predicting factors related to failure of tube thoracostomy drainage.

CONCLUSIONS

Loculation and pleural effusion leukocyte count < or = 6,400/microL were independent predicting factors of poor outcome of tube thoracostomy drainage. These results suggest that if the initial attempt at chest tube drainage fails, early surgical intervention should be considered in good surgical candidates with loculated empyema or pleural effusion with leukocyte count < or = 6,400/microL.

Thoracic empyema in HIV-infected patients: microbiology, management, and outcome

OBJECTIVES

To evaluate etiology, bacteriology, stage of disease, treatment, and outcome of HIV-infected patients with thoracic empyema (TE) over a 9-year period at a hospital teaching center.

DESIGN

We have retrospectively reviewed the charts of all HIV-infected patients with a hospital discharge diagnosis of empyema between January 1985 and November 1993.

PATIENTS

Twenty-three patients were identified (22 male and 1 female). The average patient age was 28.7+/-5.3 years. All the patients were injection-drug users, and 10 (43%) fulfilled criteria for an AIDS diagnosis. In 15 cases (65%), the empyema was the first cause of medical consultation, which then led to an HIV infection diagnosis in 11 of them (48%).

MEASUREMENTS

In each case, symptoms, chest studies, culture results, procedure timing, length of hospitalization, and outcome were reviewed.

RESULTS

Twenty-one patients (91%) had developed an empyema secondary to community-acquired pneumonia. The cultures of pleural fluid were positive in 19 cases (83%). Anaerobes were isolated from 6 patients and aerobes from 13. A single bacteria was isolated from 10 (52%), and multiple organisms (average 2.66 per case) grew in the remaining 9 positive cultures. The most common organism culture growths were Staphylococcus aureus (23%) and Gram-negative bacilli (36%). Length of hospitalization averaged 25.6 days (+/-15). Intercostal tube drainage was necessary in 18 patients and none required surgery. Patients with AIDS diagnosis needed a longer period of hospitalization, and the presence of bacteremia and bronchopleural fistula was more frequent. However, this did not influence a patient's final outcome. A follow-up was available in 18 cases, with 4 deaths recorded (average survival, 35 months; range, 4 to 84 months).

CONCLUSIONS

In our series, TE associated with HIV infection was often the primary cause leading to hospital admission and later HIV diagnosis. IV drug abuse was the predominant factor for HIV infection and was also related to clinical presentation and microbiological findings. The best approach to treatment is--as with other patient groups--a prompt drainage and appropriate antibiotic treatment, since a favorable outcome is expected.

Gram-positive anaerobic cocci

Gram-positive anaerobic cocci (GPAC) are a heterogeneous group of organisms defined by their morphological appearance and their inability to grow in the presence of oxygen; most clinical isolates are identified to species in the genus Peptostreptococcus. GPAC are part of the normal flora of all mucocutaneous surfaces and are often isolated from infections such as deep organ abscesses, obstetric and gynecological sepsis, and intraoral infections. They have been little studied for several reasons, which include an inadequate classification, difficulties with laboratory identification, and the mixed nature of the infections from which they are usually isolated. Nucleic acid studies indicate that the classification is in need of radical revision at the genus level. Several species of Peptostreptococcus have recently been described, but others still await formal recognition. Identification has been based on carbohydrate fermentation tests, but most GPAC are asaccharolytic and use the products of protein degradation for their metabolism; the introduction of commercially available preformed enzyme kits affords a physiologically more appropriate method of identification, which is simple and relatively rapid and can be used in routine diagnostic laboratories. Recent reports have documented the isolation in pure culture of several species, notably Peptostreptococcus magnus, from serious infections. Studies of P. magnus have elucidated several virulence factors which correlate with the site of infection, and reveal some similarities to Staphylococcus aureus. P. micros is a strongly proteolytic species; it is increasingly recognized as an important pathogen in intraoral infections, particularly periodontitis, and mixed anaerobic deep-organ abscesses. Comparison of antibiotic susceptibility patterns reveals major differences between species. Penicillins are the antibiotics of choice, although some strains of P. anaerobius show broad-spectrum beta-lactam resistance.

Empyema thoracis and lung abscess caused by viridans streptococci

We retrospectively studied the bacteriology and clinical features of empyema thoracis and lung abscess caused by viridans streptococci in 72 patients seen from January 1984 to September 1996. A total of 76 strains of viridans streptococci were isolated, of which the most common isolates were Streptococcus constellatus (21 strains), S. intermedius (17), and S. sanguis (10). Species belonging to the S. milleri group accounted for the majority (68%) of isolates. In 38 (53%) patients these organisms were recognized as the sole pathogens. Of the 72 patients, 53 had empyema, 14 had lung abscesses, and five had both empyema and lung abscess. Forty-six (64%) patients had underlying diseases. Of these, malignancies were the most common (17 patients), followed by diabetes mellitus (12 patients) and central nervous system diseases (10 patients). Of the 48 patients who underwent chest-tube drainage, 27 (56%) received further treatments, including intrapleural streptokinase (18 cases), surgery (9), and both intrapleural streptokinase and surgery (3). Two (14%) of the patients with lung abscess alone underwent surgical treatment. Although all viridans streptococcal isolates were susceptible to penicillin, the patients in the study had a high mortality (21%). Univariate and multivariate analysis of data for patients with empyema alone (n = 53) showed a significantly increased risk of death in those with underlying malignancy (OR = 16.0, p = 0.023) and those with non-S. milleri-group isolates (OR = 3.72, p = 0.030). These data imply a strong clinical significance of viridans streptococci in the pathogenesis of empyema and lung abscess, as well as the need for species identification of viridans streptococci in patients with pleuropulmonary diseases.

Treating empyema without surgery

Normally, the pleural spaces contain sterile lubricating fluid that enables smooth expansion and contraction of the lungs. But when microorganisms gain entry, directly or through contiguous spread of infection, the fluid becomes increasingly dense and viscous as purulence progresses. This article outlines clinical, radiographic, and pleural fluid features that can aid in distinguishing between pleural collections that usually respond to medical therapy and those that probably require surgical intervention.

VATS debridement versus thoracotomy in the treatment of loculated postpneumonia empyema

BACKGROUND

There are approximately 60,000 new cases of postpneumonic empyema every day in the United States. Usually the fibrinopurulent stage of this complication has been treated by either tube thoracostomy or thoracotomy and debridement. According to the literature, thoracoscopic treatment has not been used often for this disease.

METHODS

Sixty-four cases of postpneumonic fibrinopurulent empyema were operated on at our institution: 33 cases (group I) by means of a formal thoracotomy and 31 cases (group II) by thoracoscopy. In the thoracoscopic subset the data were collected prospectively since 1992. These results were compared with those of a historical series treated by thoracotomy between 1985 and 1991. Both populations were similar in terms of age (mean, 49 years), number of cases (33/31), sex (2.1 male/female), and comorbid status.

RESULTS

Mean preoperative length of the medical management (11.5 versus 17 days) (p = 0.03) and chest tube removal (4.3 versus 6.1 days) were shorter in group II than in group I (p = 0.02). Morbidity and mortality were identical: one death and five complications in each group. Mean operative time was similar in both groups, and hospital stay was shorter in the video-assisted thoracic surgery group (6.8 versus 11.2 days) (p = not significant). Three patients from group II needed utilitary thoracotomies for debridement completeness (10% conversion rate).

CONCLUSIONS

We conclude that video-assisted thoracic surgical treatment has the same rate of success as open thoracotomy but offers substantial advantages over thoracotomy in terms of resolution of the disease, hospital stay, and cosmesis. A prospective and randomized study is needed to confirm the findings of this nonrandomized initial experience.

Serial pleural fluid analysis in a new experimental model of empyema

Prior attempts to create an animal model of empyema by direct inoculation of bacteria alone into the pleural space have been unsuccessful. The animals either died of overwhelming sepsis or cleared the infection from the pleural space without development of an empyema. We hypothesized that injection of bacteria with a nutrient agar into the pleural space would allow the bacteria to remain in the pleural space for an extended time period, permitting an empyema to develop. The bacterium Pasteurella multocida in brain heart infusion (BHI) agar was injected into the right hemithorax of 12 New Zealand white male rabbits. Our preliminary studies showed that the animals died in less than 7 days if they were not given parenteral antibiotics. For this reason, the rabbits were given penicillin, 200,000 U, IM, every 24 h starting 24 h after bacterial injection. Pleural fluid was sampled by thoracentesis at 12, 24, 48, 72, and 96 h after bacterial injection. Pleural fluid pH, glucose, lactate dehydrogenase (LDH), leukocyte count, and Gram's stain and culture (in one half of the animals) were obtained at each time point. Pleural biopsy specimens were obtained at autopsy after 96 h. The mean pleural fluid pH reached a nadir of 7.01 at 24 h and remained less than 7.1 throughout the experiment. The mean pleural fluid glucose level reached a nadir of 10 mg/dL at 24 h. The mean pleural fluid LDH peaked at 21,000 IU/L at 24 h and the mean pleural fluid leukocyte count peaked at 12 h with a value of 67,000 cells per cubic millimeter. Gram's stains revealed organisms and cultures were positive for growth in all animals at 12 and 24 h. Some animals had positive Gram's stains and growth on cultures up to 72 h after bacterial injection. At autopsy, all rabbits injected with bacteria had gross pus in the right pleural space and had developed a thick pleural peel. Microscopic specimens of the pleura revealed large numbers of leukocytes (primarily polymorphonuclear lymphocytes) with invasion of the adjacent lung and chest wall. In conclusion, this model more closely mimics the empyema that occurs in humans, relative to previous animal models. This model appears appropriate for additional randomized studies in which different methods for the treatment of empyema can be evaluated.