The aerobic and anaerobic microbiology of empyema in adults were studied in 197 patients (11) Three hundred forty-three organisms (216 aerobic or facultative and 127 anaerobic organisms) were isolated. Aerobic bacteria were isolated in 127 (64%) patients, anaerobic bacteria in 25 (13%), and mixed aerobic and anaerobic bacteria in 45 (23%). The predominant aerobic or facultative organisms were S. pneumoniae (70 isolates), S. aureus (58), E. coli (17), K. pneumoniae (16), and Haemophilus influenzae (12). The predominant anaerobes were pigmented Prevotella and Porphyromonas spp. (24), B. fragilis group (22), anaerobic cocci (36), and Fusobacterium spp (20). Beta-lactamase-producing bacteria (BLPB) were recovered in 49 (38%) out of 128 tested specimens. Most patients from whom S. pneumoniae and H. influenzae were recovered had pneumonia, and most patients with S. aureus had pneumonia, aspiration pneumonia, and lung abscesses. The recovery of anaerobic bacteria was mostly associated with the concomitant diagnosis of aspiration pneumonia and lung, subdiaphragmatic, dental, and oropharyngeal abscesses. These data highlight the importance of anaerobic bacteria in selected cases of empyema.

The organisms isolated from empyema in children are S. aureus, S. pneumoniae, H. influenzae type b, Streptococcus pyogenes, K. pneumoniae, Mycoplasma pneumoniae (5,11), and anaerobic bacteria (8,12). A reduction in the proportion of S. aureus and H. influenzae and an increase in S. pneumoniae was noted in the U.S.A. since the early 1990s (13).

Fajardo and Chang (12) retrospective evaluated 104 children with pleural empyema and recovered anaerobes in five. All these patients were older than 10 years and had pneumonia. Polymicrobial infection occurred in four and the recovered anaerobes were Peptostreptococcus spp. (3 isolates), Bacteroides spp. (2), and F. nucleatum (1).

Brook studied the microbiology of empyema in 72 institutionalized neurologically impaired children (12). Ninety-three organisms, 60 aerobic or facultative and 33 anaerobic, were found. Aerobic bacteria were isolated in 48 (67%) patients, anaerobic bacteria in 17 (24%), and mixed aerobic and anaerobic bacteria in 7 (10%). The predominant aerobic or facultative bacteria were H. influenzae (15 isolates), S. pneumoniae (13), and S. aureus (10). The predominant anaerobes were similar to those found in aspiration pneumonia (7) or lung abscesses (6) and were gram-negative bacilli (15, including 7 B. fragilis group and 5 pigmented Prevotella and Porphyromonas spp.), Peptostreptococcus spp. (9), and Fusobacterium spp. (6). As was found also in adults (11) most cases of S. pneumoniae and H. influenzae were associated with pneumonia, while the recovery of anaerobic bacteria was linked to the diagnosis of aspiration pneumonia, lung abscess, subdiaphragmatic abscess, and dental or oropharyngeal abscess.

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