Impact of antimicrobial exposure and beta-lactamase-producing bacteria on salivary beta-lactamase activity in infancy.

Beta-lactamase production by oral bacteria is common in infancy and is associated with use of antimicrobial agents in infants. The present longitudinal study aimed to examine the frequency of salivary beta-lactamase activity (SbetaA), to compare SbetaA with the presence of beta-lactamase-producing (beta+) aerobic and anaerobic species in saliva, and to estimate the impact of antimicrobial exposure on the emergence of SbetaA in healthy infants during their first year of life. At 6 months, SbetaA was detected in 46% infants; 89% SbetaA-positive infants and 55% SbetaA-negative infants harboured beta+ species at this time (OR 7.08; CI 1.31-38.34). At 12 months, SbetaA was detected in 54% infants. Exposure to antimicrobials during the first year of life increased the risk (OR 2.60; CI 0.72-9.36) of having SbetaA.

Bacteremia after plate removal and tooth extraction.

Our aim was to investigate the occurrence of bacteremia associated with removal of a semirigid osteosynthesis plate and an adjacent third molar. Ten patients with fixed mandibular angle fracture were bacteriologically sampled from the second molar's distal gingival pocket, from the third molar's extraction socket and from the osteosynthesis plate. Blood samples from the ante-cubital vein were taken 10 times until 30 min postoperatively. Established culture, isolation and identification methods for the bacterial species were used. Bacteremia was detected in 60% of the subjects, most frequently 1.5 min after removal of the plate (20%) and 1.5 and 5 min after extraction of the tooth (20%), but also 10 min (10%) and 30 min (10%) postoperatively. 13 different bacterial species or groups were isolated, mean 2.5 +/- 1.9 per bacteremia-positive subject. The majority (85%) were anaerobes with Actinomyces, Campylobacter and Lactobacillus species predominating. In all the blood culture-positive cases the corresponding species was also recovered from one or more of the oral samples. These results show that oral surgical procedures are associated with a high frequency of longstanding anaerobic bacteremia, which could be harmful in patients at risk.

Bacteremia following surgical dental extraction with an emphasis on anaerobic strains.

Our aim was to investigate bacteremia caused by surgical extraction of partly erupted mandibular third molars. From 16 young adults, bacterial samples were taken from the third-molar pericoronal pocket and post-operatively from the extraction socket, and blood samples were drawn from the ante-cubital vein up to 30 min after surgery. Of the subjects, 88% had detectable bacteremia-50% 1 min after the incision, 44% immediately after extraction. The respective percentages at 10, 15, and 30 min were 44%, 25%, and 13%. Blood cultures contained 31 species (74% anaerobes), with 3.9 +/- 2.6 species isolated per subject. Most prevalent were the anaerobes Prevotella, Eubacterium, and Peptostreptococcus sp. and the aerobes viridans-group streptococci and Streptococcus milleri group. Any species found in the blood was also isolated from the mouth, from 93% of the pericoronal pockets and from 43% of the extraction sockets. Surgical dental extraction clearly causes bacteremia of a high frequency and lasting longer than thus far assumed.

Age-related frequency of penicillin resistance of oral Veillonella.

Veillonella spp. are early colonizing inhabitants in the mouth. As part of studies on penicillin resistance among oral indigenous anaerobic microbiota in childhood, the aim of the present longitudinal study was to examine the emergence of resistant strains in Veillonella populations. Altogether 305 Veillonella isolates from saliva of 49 healthy infants followed from 2 to 24 months of age were examined for their in vitro susceptibility to penicillin G and, further, 20 penicillin-resistant isolates representing 5 MIC categories to ampicillin, amoxicillin, amoxicillin/clavulanate, cefoxitin, and beta-lactamase production. In infants positive for oral Veillonella, the recovery rate of penicillin-resistant (MIC >/=2 microg/ml) strains increased with age up to 68%, however, most infants simultaneously harbored penicillin-susceptible strains. During the follow-up, the MIC(50) increased from 0.5 microg/ml to 2 microg/ml. In addition to penicillin G, 8/20 strains also showed reduced susceptibility to ampicillin and/or amoxicillin but none produced beta-lactamase. Our study suggests other mechanisms than enzymatic degradation of beta-lactam ring for resistance of oral Veillonella to penicillin.

Ethanol oxidation and acetaldehyde production in vitro by human intestinal strains of Escherichia coli under aerobic, microaerobic, and anaerobic conditions.

BACKGROUND: Many human colonic facultative anaerobic and aerobic bacteria are capable of alcohol dehydrogenase (ADH)-mediated ethanol oxidation. In this bacteriocolonic pathway for ethanol oxidation intracolonic ethanol is first oxidized by bacterial ADHs to acetaldehyde, which is further oxidized by either colonic mucosal or bacterial aldehyde dehydrogenases to acetate. The produced acetaldehyde is a highly toxic and carcinogenic agent. This study was aimed to investigate the ethanol oxidation capability and acetaldehyde formation of Escherichia coli IH 50546 and IH 50817. These intestinal E. coli strains expressed either high (IH 50546) or low (IH 50817) ADH activity. METHODS: Strains were cultured for 48 h on agar plates supplemented with ethanol under aerobic, microaerobic (6% O2), and anaerobic conditions. RESULTS: Under aerobic conditions both E. coli strains oxidized ethanol. The ethanol consumption rates (ECR) were 1.046+/-0.025 mM/h and 0.367+/-0.148 mM/h with IH 50546 and IH 50817, respectively. In the case of IH 50546 this was associated with significant acetaldehyde production (418+/-13 microM), suggesting ADH-mediated ethanol oxidation. Under microaerobic conditions only IH 50546 was able to oxidize ethanol (ECR, 0.498+/-0.074 mM/h) and to produce acetaldehyde (up to 440+/-76 microM) to significant extents. Under anaerobic conditions both strains fermented glucose to ethanol. CONCLUSIONS: This study experimentally shows the potential of certain bacteria representing normal human colonic flora to produce acetaldehyde under various atmospheric conditions that may prevail in different parts of the GI tract. This bacterial adaptation may be an essential feature of the bacteriocolonic pathway to produce toxic and carcinogenic acetaldehyde from either endogenous or exogenous ethanol.

Beta-lactamase production by oral anaerobic gram-negative species in infants in relation to previous antimicrobial therapy.

The frequency of beta-lactamase production in gram-negative bacteria has increased considerably during recent years. In this study, beta-lactamase production by oral anaerobic gram-negative rods isolated from saliva was longitudinally examined for 44 Caucasian infants at the ages of 2, 6, and 12 months in relation to their documented exposure to antibiotics. Isolates showing decreased susceptibility to penicillin G (1 microg/ml) were examined for beta-lactamase production by using a chromogenic cephalosporin disk test. beta-Lactamase-positive, gram-negative anaerobic species were found in 11, 55, and 89% of each age group, respectively. beta-Lactamase production was most frequent among organisms of the Prevotella melaninogenica group. At 12 months, 73% of the infants harbored beta-lactamase-producing members of the P. melaninogenica group, 55% had nonpigmented Prevotella species, 25% had Porphyromonas catoniae, 23% had Fusobacterium nucleatum, and 5% had Capnocytophaga species. Several beta-lactamase-producing species could be simultaneously found in the infants' mouths. The presence of beta-lactamase-producing species was significantly associated with the infants' exposure to antibiotics through antimicrobial treatments given to the infants and/or their mothers.

beta-lactamase production by oral pigmented Prevotella species isolated from young children.

The frequency of beta-lactamase production by oral pigmented Prevotella species isolated from 23 healthy young children and the minimal inhibitory concentrations (MICs) for 186 available beta-lactamase-positive isolates were examined by using the chromogenic cephalosporin disk test (AB BIODISK, Solna, Sweden) and the Etest (AB BIODISK) and/or the agar dilution method of the National Committee for Clinical Laboratory Standards (Villanova, PA, USA), respectively. beta-Lactamase-positive Prevotella melaninogenica strains were isolated from all children, and more than two-thirds of the Prevotella denticola and Prevotella loescheii strains isolated from the children were beta-lactamase-positive. The beta-lactamase-producing Prevotella intermedia group consisted of Prevotella nigrescens and the P. intermedia/ P. nigrescens-like organism (PINLO); P. intermedia was not found. Only two P. nigrescens isolates but most of the PINLO isolates produced beta-lactamase. The MICs for beta-lactamase-producing strains varied between 0.38 and 64 micrograms/mL. beta-Lactamase production by oral pigmented Prevotella species colonizing young children is already frequent. The phenomenon should be taken into account in the treatment of pediatric anaerobic infections of oral origin.