The effect of antimicrobial therapy on mixed infections with Bacteroides species. Is eradication of the anaerobes important?

Proinflammatory MG-63 cells response infection with Enterococcus faecalis cps2 evaluated by the expression of TLR-2, IL-1β, and iNOS mRNA

OBJECTIVE

We have previously demonstrated that unencapsulated Enterococcus faecalis cps2 inhibits biofilm formation of Candida albicans, a fungus commonly found with E. faecalis in periapical lesion. In this study, we compared encapsulated and unencapsulated E. faecalis cps2 strains relationship with osteoblastic (MG-63) cells, whereas E. faecalis ATCC 29212 were used as a reference strain.

RESULTS

The binding capacity of E. faecalis to MG-63 cells as shown by each tested strain was comparable, but the unencapsulated strain was less invasive compared to the encapsulated and the reference strains. Moreover, quantitative real time-PCR (qPCR) results showed that infecting unencapsulated E. faecalis cps2 is a stronger stimulator for toll like receptor 2 (TLR2) and interleukin-1β (IL-1β) mRNAs, but not for inducible nitric oxide synthase (iNOS) mRNA in osteoblastic cells. In conclusion, the performance of unencapsulated E. faecalis cps2 when the bacterium interacts with osteoblastic cells is quite different from that of encapsulated E. faecalis cps2 and reference strains. It appears that the unencapsulated strain might contribute to the persistence of the periapical inflammatory response, depending on down-regulation of iNOS mRNA expression.

The effects of gut commensal bacteria depletion on mice exposed to acute lethal irradiation

The prevention and management of bacterial infection are the mainstays of therapies for irradiation victims. However, worries about adverse effects arise from gut commensal flora depletion owing to the broad-spectrum antibiotics treatment. In the present study, we investigated the effects of gut bacteria depletion on the mice receiving total-body irradiation (TBI) at a single dose of 12 Gy. One group of mice was merely exposed to TBI but was free of antibiotic treatment throughout the experiment, while the other two groups of mice were additionally given broad-spectrum antibiotics, either from 2 weeks before or immediately after irradiation. The survival time of each animal in each group was recorded for analysis. Results showed that the mean survival time of mice was longest in the group without antibiotic treatment and shortest in the group treated with broad-spectrum antibiotics from 2 weeks before TBI. In conclusion, our data suggested that depletion of gut commensal bacteria with broad-spectrum antibiotics seemed deleterious for mammals receiving lethal TBI.

In vitro bactericidal activity of piperacillin, gentamicin, and metronidazole in a mixed model containing Escherichia coli, Enterococcus faecalis, and Bacteroides fragilis

An anaerobic, mixed model assay was used to study the bactericidal activities of piperacillin, gentamicin, and metronidazole, alone and in double- and triple-antibiotic combinations against a polymicrobial suspension of E. coli, E. faecalis, and B. fragilis. Only slight differences were noted with the agents when tested against single (10(5) cfu/mL inoculum) versus polymicrobic suspensions (10(6) cfu/mL final inoculum) of susceptible and resistant organisms. Contrary to previous reports in the literature, metronidazole was not active against E. coli in an anaerobic environment (even in the presence of B. fragilis) nor was the activity of metronidazole reduced against B. fragilis in the presence of E. faecalis. Gentamicin demonstrated excellent activity against E. coli when tested in a Bactron anaerobic chamber (5% hydrogen, 5% CO(2,) 90% nitrogen). The pH of the media was only reduced to 6.3-6.7, considerably higher than the pH range of 5-6 needed to significantly reduce the activity of aminoglycosides.

Anaerobic culture yield in interventional radiologic drainage procedures

PURPOSE

This study was designed to determine the yield of anaerobic cultures from percutaneous radiologic drainage procedures.

PATIENTS AND METHODS

Anaerobic culture results in 317 patients from June 1992 to May 1994 were retrospectively examined. Anaerobic specimens were placed in specially designed anaerobic culture tubes and not blood culture media. Patients had undergone the following procedures: percutaneous nephrostomy (105 patients), biliary drainage (65 patients), and abdominal abscess drainage (147 patients). Aerobic culture results were tabulated in those patients with positive anaerobic cultures.

RESULTS

Overall, 10% of patients (n = 32) had positive anaerobic cultures (Bacteroides species, n = 25; Clostridium, n = 6; other organisms, n = 4). Anaerobes were isolated in 13% (n = 19) of abdominal abscess drainages, 8% (n = 8) of nephrostomy drainages, and 8% (n = 5) of biliary drainages. Aerobic isolates were present in 78% (n = 25) of patients with anaerobic infection.

CONCLUSION

The yield for anaerobic cultures varies for different types of percutaneous drainage procedures from 8% to 13%. When isolated, anaerobic bacteria are frequently mixed with aerobic bacteria. Anaerobic culture usage is recommended with abdominal abscess and biliary drainages. Anaerobic bacterial cultures are not recommended for percutaneous nephrostomy unless the patient has a urinary tract malignancy or has undergone urinary instrumentation.

Infection after colorectal surgery: a randomized trial of prophylaxis with piperacillin versus sulbactam/piperacillin. West of Scotland Surgical Infection Study Group

Antibiotics used for prophylaxis in elective colorectal surgery should be effective against the organisms contaminating the soft tissues and isolated from postoperative infections. These are usually the enterobacteriaceae commensal to the colon. However, staphylococcal and anaerobic infections are not uncommon. Piperacillin has been used as antibiotic prophylaxis and been shown to be as efficacious as an aminoglycoside with metronidazole. Piperacillin is susceptible to many beta-lactamases and we have therefore conducted a study to assess the efficacy of adding sulbactam, a beta-lactamase inhibitor, to piperacillin for prophylaxis in elective colorectal surgery. Three hundred and seventy-nine patients were randomized to receive a single dose of piperacillin 4 g intravenously (iv) (group P, n = 192) or piperacillin 4 g with sulbactam 2 g iv (group SP n = 187). Fifty-three patients were withdrawn from analysis leaving 168 evaluable patients in group P and 158 patients in group SP. Postoperative infective complications occurred in 91 (28%) patients, 55 (33%) in group P and 36 (23%) in group SP (chi 2 = 4.0 P < 0.05). Surprisingly Staphylococcus aureus was isolated from wound infections in 22 patients (12 in group P and 10 in group SP) which represents 24% of those patients who developed infective morbidity. We conclude that sulbactam improves the efficacy of piperacillin as prophylaxis in elective colorectal surgery but does little to protect against staphylococcal wound infection.

Selective decontamination of the colon before elective colorectal surgery. West of Scotland Surgical Infection Study Group

The controversy over the route of administration of antibiotic prophylaxis in patients undergoing elective colorectal operations persists for oral, parenteral, and a combination of the two routes. The oral antibiotics commonly administered for colorectal prophylaxis, neomycin and eythromycin base, are not absorbed in the gastrointestinal tract (GIT). However, the 4-fluoroquinolones are absorbed in the upper GIT and are excreted in part by the colonic mucosa. Their action is then to remove, or severely depress, the gram-negative aerobic bacilli leaving the anaerobic flora unaffected. This action is the principle of selective decontamination. We have assessed the efficacy of oral ciprofloxacin in a prospective randomized clinical trial in which all patients received piperacillin 4 g i.v. as single-dose parenteral prophylaxis. A group of 327 evaluable patients were randomized to receive ciprofloxacin 500 mg b.i.d. with the preoperative cathartic (group OA, n = 159) or no oral antibiotic (group NOA, n = 168). Postoperative wound infection occurred in 18 (11.3%) patients in group OA and 39 (23.2%) patients in group NOA (chi 2 = 7.2, p = 0.007). Operation-related infection of any type occurred in 23 (14.5%) patients in group OA compared with 55 (32.7%) in group NOA (chi 2 = 14.0, p = 0.0002). The median postoperative hospital stay was 11 days (interquartile range 4.5 days) for group OA and 12 days (interquartile range 8 days) for group NOA (Mann Whitney U test, p = 0.005). Ignoring the treatment group, the median postoperative hospital stay was 17 days (interquartile range 10 days) for infected patients and 11 days (interquartile range 4 days) for those not infected.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of metronidazole in the treatment of periodontal diseases

This article discusses the ability of metronidazole to improve periodontal health. Review of the drug's pharmacology and potential side effects indicate that it poses little threat to humans of inducing acute toxicity, mutagenesis, or cancer if used according to recommended dosing regimens. Studies addressing metronidazole utilization in a variety of clinical conditions demonstrate that its routine use does not enhance root planing. However, adjunctive antibiotic therapy may be advantageous in the treatment of sites where effective root planing is precluded due to deep pockets or when anaerobic periodontal infections do not respond to conventional therapy.