Presence of beta-lactamase-producing bacteria and beta-lactamase activity in abscesses.

The presence of beta-lactamase-producing bacteria (BLPB) in abscesses was investigated in 109 abscesses. Single isolates were recovered in 23 (21%) instances and were predominantly Staphylococcus aureus. The other abscesses yielded growth of two or more aerobic and/or anaerobic organisms. Aerobic bacteria were recovered in 28 (26%) of the aspirates, anaerobic bacteria in 41 (38%), and mixed aerobic and anaerobic bacteria in 40 (36%). A total of 362 isolates (247 anaerobes and 115 aerobes) were recovered, accounting for 3.3 isolates per specimen (2.2 anaerobes and 1.1 aerobes). One hundred beta-lactamase-producing organisms were recovered in 88 (77%) specimens. These included all 28 isolates of Bacteroides fragilis, 18 of 30 Bacteroides melaninogenicus, 42 of 43 S. aureus, and 11 of 14 Escherichia coli. Beta-lactamase activity was detected in 40 (55%) of the purulent specimens when using the chromogenic cephalosporin nitrocefin method. These data demonstrate the presence of aerobic and anaerobic BLPB in abscesses.