Metronidazole in prevention and treatment of bacteroides infections after appendicectomy

A tale of two habitats: Bacteroides fragilis, a lethal pathogen and resident in the human gastrointestinal microbiome

Bacteroides fragilis is an obligately anaerobic Gram-negative bacterium and a major colonizer of the human large colon where Bacteroides is a predominant genus. During the growth of an individual clonal population, an astonishing number of reversible DNA inversion events occur, driving within-strain diversity. Additionally, the B. fragilis pan-genome contains a large pool of diverse polysaccharide biosynthesis loci, DNA restriction/modification systems and polysaccharide utilization loci, which generates remarkable between-strain diversity. Diversity clearly contributes to the success of B. fragilis within its normal habitat of the gastrointestinal (GI) tract and during infection in the extra-intestinal host environment. Within the GI tract, B. fragilis is usually symbiotic, for example providing localized nutrients for the gut epithelium, but B. fragilis within the GI tract may not always be benign. Metalloprotease toxin production is strongly associated with colorectal cancer. B. fragilis is unique amongst bacteria; some strains export a protein >99 % structurally similar to human ubiquitin and antigenically cross-reactive, which suggests a link to autoimmune diseases. B. fragilis is not a primary invasive enteric pathogen; however, if colonic contents contaminate the extra-intestinal host environment, it successfully adapts to this new habitat and causes infection; classically peritoneal infection arising from rupture of an inflamed appendix or GI surgery, which if untreated, can progress to bacteraemia and death. In this review selected aspects of B. fragilis adaptation to the different habitats of the GI tract and the extra-intestinal host environment are considered, along with the considerable challenges faced when studying this highly variable bacterium.

Effects of metronidazole on proopiomelanocortin a gene expression in zebrafish

The Metronidazole (MTZ), a widely used antibiotic for treating variations of infections, recently is applied in a powerful tool for specifically ablating cells or tissues when combined with E. coli nitroreductase (NTR). Although some undesired biological effects on eukaryote cells have been reported previously, the toxicological mechanism of MTZ has not been uncovered yet. In current study, we found that MTZ can induce proopiomelanocortin a (pomca) expression in zebrafish larvae. The effect of MTZ is in stage-sensitive and dose-dependent manner. A pro-proliferation activity of MTZ on pomca-expressing cells in the pituitary at larval stage was also observed. Furthermore, up-regulated levels of prolactin (prl) and glycoprotein hormone subunit α (gsuα) were also observed after the MTZ treatment. Therefore, utilizing our zebrafish as in vivo model, we concluded that MTZ can interfere the endocrine signals in the pituitary hormone genes expression. Our current results raised the cautions to the intensively application of MTZ in clinical practices and biomedical researches.

Deficiency of the ferrous iron transporter FeoAB is linked with metronidazole resistance in Bacteroides fragilis

BACKGROUND

Metronidazole is the most commonly used antimicrobial for Bacteroides fragilis infections and is recommended for prophylaxis of colorectal surgery. Metronidazole resistance is increasing and the mechanisms of resistance are not clear.

METHODS

A transposon mutant library was generated in B. fragilis 638R (BF638R) to identify the genetic loci associated with resistance to metronidazole.

RESULTS

Thirty-two independently isolated metronidazole-resistant mutants had a transposon insertion in BF638R_1421 that encodes the ferrous transport fusion protein (feoAB). Deletion of feoAB resulted in a 10-fold increased MIC of metronidazole for the strain. The metronidazole MIC for the feoAB mutant was similar to that for the parent strain when grown on media supplemented with excess iron, suggesting that the increase seen in the MIC of metronidazole was due to reduced cellular iron transport in the feoAB mutant. The furA gene repressed feoAB transcription in an iron-dependent manner and disruption of furA resulted in constitutive transcription of feoAB, regardless of whether or not iron was present. However, disruption of feoAB also diminished the capacity of BF638R to grow in a mouse intraperitoneal abscess model, suggesting that inorganic ferrous iron assimilation is essential for B. fragilis survival in vivo.

CONCLUSIONS

Selection for feoAB mutations as a result of metronidazole treatment will disable the pathogenic potential of B. fragilis and could contribute to the clinical efficacy of metronidazole. While mutations in feoAB are probably not a direct cause of clinical resistance, this study provides a key insight into intracellular metronidazole activity and the link with intracellular iron homeostasis.

Oral metronidazole as antibiotic prophylaxis for patients with nonperforated appendicitis

Background

The rate of wound infection after appendectomy without antibiotic prophylaxis is 10%–30%. The role of prophylactic antibiotic therapy in nonperforated appendicitis is still controversial. Metronidazole is against anaerobic organisms and its bioavailability after oral and parenteral administration has been shown to be similar. The objective of the present study is to compare the infective complications rate after open appendectomy for nonperforated appendicitis receiving either oral or intravenous metronidazole as prophylaxis.

Methods and Materials

From June 2007 to July 2009 in a randomized controlled trial, 204 patients with nonperforated appendicitis underwent an open appendectomy; 122 male and 82 female with mean age of 25 years. Among these, 102 (case group) received oral metronidazole and in 102 (control group) metronidazole was administered intravenously before surgery. The rate of wound infection and duration of the postoperative hospital stay was studied in the two groups.

Results

The rate of wound infection was not significantly different in the two groups. (6% and 4% in study and control group, respectively, P = 0.861). Also the hospital stay was equal in two groups (2.3 days and 2.7 days in study and control group, respectively, P = 0.293).

Conclusion

Single dose of oral metronidazole prior to operation can provide a sufficient prophylaxis for nonperforated appendicitis; so, it can be substitute the parental route of antibiotic administration.

In vitro susceptibility to selected antibiotics in bacteria of the Bacteroides fragilis group

Susceptibility of strains of Bacteroides fragilis group (1284 isolates from cancerous and noncancerous patients in 1994-2004) showed an increase in resistance toward some antibiotics (by 9 % toward penicillin and 8 % toward clindamycin) compared with the resistance level of 10 years ago. The increase in resistance was not detected in the case of ampicillin + sulbactam and metronidazole.

Antibiotics versus placebo for prevention of postoperative infection after appendicectomy

BACKGROUND

Appendicitis is the most common cause of acute abdominal pain requiring surgical intervention. The cause of appendicitis is unclear and the mechanism of pathogenesis continues to be debated. Despite improved asepsis and surgical techniques, postoperative complications, such as wound infection and intraabdominal abscess, still account for a significant morbidity. Several studies implicate that postoperative infections are reduced by administration of antimicrobial regimes.

OBJECTIVES

This review evaluated the use of antibiotics compared to placebo or no treatment in patients undergoing appendectomy. Will these patients benefit from antimicrobial prophylaxis? The outcomes were described according to the nature of the appendix, as either simple appendicitis (including the non-infectious stage) and complicated appendicitis. The efficacy of different antibiotic regimens were not evaluated.

SEARCH STRATEGY

We searched The Cochrane Central Register of Controlled Trials (Cochrane Library 2005 issue 1); Pubmed ; EMBASE; and the Cochrane Colorectal Cancer Group Specialised Register (April 2005). In addition, we manually searched the reference lists of the primary identified trials.

SELECTION CRITERIA

We evaluated Randomised Controlled Trials (RCTs) and Controlled Clinical Trials (CCTs) in which any antibiotic regime were compared to placebo in patients suspected of having appendicitis, and undergoing appendectomy. Both studies on children and adults were reviewed. The outcome measures of the studies were: Wound infection, intra abdominal abscess, length of stay in hospital, and mortality.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed, recorded and cross-checked by two reviewers.

MAIN RESULTS

Forty-five studies including 9576 patients were included in this review. The overall result is that the use of antibiotics is superior to placebo for preventing wound infection and intraabdominal abscess, with no apparent difference in the nature of the removed appendix. Studies exclusively on children and studies examining topical application reported results in favour to the above, although the results were not significant.

AUTHORS' CONCLUSIONS

Antibiotic prophylaxis is effective in the prevention of postoperative complications in appendectomised patients, whether the administration is given pre-, peri- or post-operatively, and could be considered for routine in emergency appendectomies.

Antibiotics versus placebo for prevention of postoperative infection after appendicectomy

BACKGROUND

Appendicitis is the most common cause of acute abdominal pain requiring surgical intervention. The cause of appendicitis is unclear and the mechanism of pathogenesis continues to be debated. Despite improved asepsis and surgical techniques, postoperative complications, such as wound infection and intraabdominal abscess, still account for a significant morbidity. Several studies implicate that postoperative infections are reduced by administration of antimicrobial regimes.

OBJECTIVES

The objective of this review is to evaluate the use of antibiotics with placebo or no treatment in patients undergoing appendectomy. Will these patients benefit from antimicrobial prophylaxis? The outcomes are described according to the nature of the appendix, as either simple appendicitis (including the non-infectious stage) and complicated appendicitis. This review do not attempt to compare the effect of different regimens. That clinical question is addressed in another review undertaken by Bleuer 1999.

SEARCH STRATEGY

We searched The Cochrane Controlled Trials Register (Cochrane Library 2002 issue 4); Pubmed, Embase and the Cochrane Colorectal Cancer Group Specialised Register (Up to October 2002). In addition we manually searched the reference lists of the primary identified trials.

SELECTION CRITERIA

We evaluated Randomised Controlled Trials (RCTs) and Controlled Clinical Trials (CCTs) in which any antibiotic regime were compared to placebo in patients suspected of having appendicitis, and undergoing appendectomy. Both studies on children and adults were reviewed. The outcome measures of the studies were: Wound infection, intra abdominal abscess, length of stay in hospital, and mortality.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed, recorded and cross-checked by two reviewers.

MAIN RESULTS

Forty-five studies including 9576 patients were included in this review. The overall result is that the use of antibiotics is superior to placebo for preventing wound infection and intraabdominal abscess, with no apparent difference in the nature of the removed appendix. Studies exclusively on children and studies examining topical application reported results in favour to the above although the results were not significant.

REVIEWER'S CONCLUSIONS

Antibiotic prophylaxis is effective in the prevention of postoperative complications in appendectomised patients, whether the administration is given pre-, peri- or post-operatively, and could be considered for routine in emergency appendectomies.

Can Oral Metronidazole Substitute Parenteral Drug Therapy in Acute Appendicitis?: A New Policy in the Management of Simple or Complicated Appendicitis with Localized Peritonitis: A Randomized Controlled Clinical Trial

To demonstrate the efficacy of oral metronidazole (OM) in simple or complicated appendicitis with localized peritonitis, a randomized prospective study was carried out in 1083 patients, ranging in age from 4 to 50 years (mean age, 21.38).

The patients were randomly divided into two groups. The study group (SG) (524 patients) received OM (500 mg for adults, 7–10 mg/kg if less than 15 years) 2–3 hours before operation. The drug was continued 4 to 5 hours after operation, every 8 hours, for three doses if the appendix was mild to severely inflamed. In the case of complicated appendicitis (114 patients), the same dose was given for 3 to 6 days, depending on the absence or presence of pus. Ceftizoxime was administered to the control group (CG) (559 patients) 2 to 3 hours before operation and then postoperatively every 6 hours for three doses if the appendix was mild to severely inflamed. The complicated cases in the CG (120 patients) received a combination of penicillin, chloramphenicol, and gentamicin for 3 to 6 days, depending on the absence or presence of pus.

The serum concentration of metronidazole measured in 43 patients was at bactericidal level in 40 (mean ± SD standard deviation, 10.65 ± 4.89 μg/mL).

The rate of wound infection was not significantly different in the SG and the CG with the same degree of pathology (3.17% vs 2.96% if uncomplicated; 15.78% vs 14.16% if complicated, respectively). Pelvic collection occurred in four adults and one child in the CG with perforated appendicitis (4.16%). The same complication developed in two adults and two children in the SG with perforated appendicitis (3.5%). All six adults and one of the children in the SG had to be re-explored, whereas the remaining two children responded to conservative management (OM and gentamicin). In uncomplicated cases, hospital stay and hospital charge were both almost the same in both groups. However, length of hospitalization was nearly 1 day shorter and hospital cost per day was about 30 per cent less in complicated cases in the SG as compared with the CG.

Conclusively, OM may not only substitute parenteral antibiotics in acute appendicitis as a prophylactic agent, but it may also be used as a cost-effective drug and is more convenient to the patient.

Metronidazole. A therapeutic review and update

The nitroimidazole antibiotic metronidazole has a limited spectrum of activity that encompasses various protozoans and most Gram-negative and Gram-positive anaerobic bacteria. Metronidazole has activity against protozoans like Entamoeba histolytica, Giardia lamblia and Trichomonas vaginalis, for which the drug was first approved as an effective treatment. Anaerobic bacteria which are typically sensitive are primarily Gram-negative anaerobes belonging to the Bacteroides and Fusobacterium spp. Gram-positive anaerobes such as peptostreptococci and Clostridia spp. are likely to test sensitive to metronidazole, but resistant isolates are probably encountered with greater frequency than with the Gram-negative anaerobes. Gardnerella vaginalis is a pleomorphic Gram-variable bacterial bacillus that is also susceptible to metronidazole. Helicobacter pylori has been strongly associated with gastritis and duodenal ulcers. Classic regimens for eradicating this pathogen have included metronidazole, usually with acid suppression medication plus bismuth and amoxicillin. The activity of metronidazole against anaerobic bowel flora has been used for prophylaxis and treatment of patients with Crohn's disease who might develop an infectious complication. Treatment of Clostridium difficile-induced pseudomembraneous colitis has usually been with oral metronidazole or vancomycin, but the lower cost and similar efficacy of metronidazole, coupled with the increased concern about imprudent use of vancomycin leading to increased resistance in enterococci, have made metronidazole the preferred agent here. Metronidazole has played an important role in anaerobic-related infections. Advantages to using metronidazole are the percentage of sensitive Gram-negative anaerobes, its availability as oral and intravenous dosage forms, its rapid bacterial killing, its good tissue penetration, its considerably lower chance of inducing C. difficile colitis, and expense. Metronidazole has notable effectiveness in treating anaerobic brain abscesses. Metronidazole is a cost-effective agent due to its low acquisition cost, its pharmacokinetics and pharmacodynamics, an acceptable adverse effect profile, and its undiminished antimicrobial activity. While its role as part of a therapeutic regimen for treating mixed aerobic/anaerobic infections has been reduced by newer, more expensive combination therapies, these new combinations have not been shown to have any therapeutic advantage over metronidazole. Although the use of metronidazole on a global scale has been curtailed by newer agents for various infections, metronidazole still has a role for these and other therapeutic uses. Many clinicians still consider metronidazole to be the 'gold standard' antibiotic against which all other antibiotics with anaerobic activity should be compared.

Combined topical and systemic antibiotic prophylaxis in acute appendicitis

Two hundred forty-six patients with acute appendicitis were randomly assigned to one of two groups. One group of 120 patients received systemic clindamycin preoperatively. Another group of 126 patients received, in addition to systemic clindamycin, a solution of topical ampicillin applied to subcutaneous tissues. No differences were found in the characteristics of the two groups. Combined prophylaxis with clindamycin and ampicillin significantly reduced wound infection to 4%, compared with clindamycin alone (p less than 0.02). A decrease in the surgical wound infection rate in the group treated with clindamycin and ampicillin was mainly observed in patients with advanced (gangrenous and perforated) appendicitis (p less than 0.05). A significant decrease in wound infection rates in patients with positive culture results was also found. We conclude that prophylaxis with a combination of systemic clindamycin and topical ampicillin solution, when compared with clindamycin alone, more effectively prevents wound infection after emergency appendectomy, especially in patients with serious wound contamination.

Design and trial of a metronidazole loading dose regimen for patients undergoing emergency surgery

A dosing regimen for administration of metronidazole to patients undergoing emergency surgery was designed using pharmacokinetic data. Computer estimates of the pharmacokinetic parameters from normal volunteers were used to determine a loading dose protocol that would achieve plasma metronidazole levels above 6.2 micrograms/mL, that is, above the minimum inhibitory concentration (MIC) of most pathogenic anaerobic bacteria, at the time of surgery. The protocol aimed to identify the minimum intravenous metronidazole dose in combination with a rectal suppository regimen. This was calculated to be a 1 g (two 500 mg) metronidazole rectal suppository dose administered when the decision to operate was made, followed by a 200 mg intravenous dose at the induction of anaesthesia if the time to surgery was within 1-8 h. This protocol was tested in 10 patients undergoing emergency abdominal/pelvic surgery. All patients in the trial were found to have levels well above the MIC at the time of surgery (mean = 17.06 micrograms/mL, s.d. = 4.76). It is concluded that appropriate use of metronidazole suppositories can minimize intravenous dosage requirements for metronidazole under conditions of emergency loading as well as elective surgery.

Timing of prophylactic antibiotics in abdominal surgery: trial of a pre-operative versus an intra-operative first dose

When prophylactic antibiotics are used in abdominal surgery it is customary to give the first dose before the operation. Whilst intra-operative antibiotics may be effective in elective surgery, there may be an advantage to starting pre-operatively when there is already an infective focus such as appendicitis. Antibiotics started pre-operatively (group P) have been compared with antibiotics started after initial abdominal exploration (group T). Three intravenous doses of 500 mg metronidazole plus 1 g cephazolin were given in a randomized, double-blind study of 700 emergency and elective high-risk abdominal operations. Antibiotic plasma concentrations at the end of the operation were significantly lower in group P but lay well within the therapeutic range. Wound infection rates, which included minor and delayed infections, were similar in both groups (group P, 57 of 342, 16.7 per cent; group T, 55 of 358, 15.4 per cent; 95 per cent confidence intervals for the difference being -4.1 to +6.7 per cent. In appendicitis, wound infection rates were 12.1 and 13.9 per cent for groups P and T respectively. However, non-fatal deep sepsis was more common in group P (nine cases) than in group T (two cases) (chi 2 = 4.9, P less than 0.05). Postoperative infection was twice as common in obese patients whose body mass index (BMI) was greater than or equal to 26 (39 of 132, 30 per cent) than in thin patients whose BMI was less than 24 (41 of 288, 14 per cent; chi 2 = 13.8, P less than 0.001). This study failed to show any advantage to starting antibiotics pre-operatively, even in appendicitis.

Preventing wound infection after appendicectomy: a review

An exponential increase in the number of published prospective studies reflects both a continuing interest in, and a lack of consensus on, the optimal prophylaxis of wound sepsis after appendicectomy. Review of the literature over the last 25 years leads us to emphasize both the importance of adequate study size and of stratification of the severity of the sepsis found at operation. For critical comparison of prophylactic regimens the high percentage of wound infections disclosed after discharge from hospital must be taken into account. Antibiotics reduce the frequency of wound sepsis and although low wound sepsis rates have been reported with systemic antibiotics active against only anaerobes, the cumulative evidence favours a spectrum of antibacterial activity against both aerobic and anaerobic organisms. Topical antiseptics have no significant effect but topical antibiotics are beneficial. Wide variations in outcome for similar antibiotic regimens reflect the importance of technical factors in determining the frequency of wound sepsis.

Cefotaxime plus metronidazole appears more effective than piperacillin in the prevention of postappendicectomy wound sepsis. Preliminary results of a comparative trial

Metronidazole suppositories have previously been shown to be superior to povidone iodine intraoperative wound spray in reducing postappendicectomy wound sepsis. In subsequent studies metronidazole suppositories and cefotaxime injections reduced the sepsis rate to 9.3%, while the same combination produced a wound sepsis rate of 7.6% compared with 17.2% for cefotaxime alone. In an ongoing study, metronidazole and cefotaxime are now being compared with piperacillin in a single-blind trial. Adult patients undergoing emergency appendicectomy in Nottingham have been included in this study, which has ethical committee approval. When the decision to perform emergency appendicectomy was made, the patient was randomly allocated a numbered pack. This contained either 3 x 1g injections of cefotaxime and 6 x 1g metronidazole suppositories or 3 x 2g injections of piperacillin and 6 placebos. 40 minutes before operation the patient received the first suppository and the remainder every 8 hours. The patient received the first injection of antibiotic by intravenous or intramuscular injection and the remaining doses 8 and 16 hours later. A wound was regarded as infected if pus discharged either spontaneously or on incision. 175 patients have been studied to date. The treatment groups were well matched for age and sex. Seven of the 77 patients in the cefotaxime/metronidazole group (9.1%) compared with 12 of the 76 in the piperacillin group (15.8%) have developed wound infections. This study confirms that the combination of cefotaxime and metronidazole seems to be more effective than piperacillin alone in the reduction of postappendicectomy wound sepsis. Currently cefotaxime plus metronidazole is the therapy of choice.

Metronidazole prophylaxis in acute mural appendicitis: failure of a single intra-operative infusion to reduce wound infection

The efficacy of a single 500 mg intravenous intra-operative dose of metronidazole in the prevention of postoperative wound infection, following appendicectomy for acute mural appendicitis, was studied in a prospective randomized placebo controlled trial. Fourteen of the 96 patients (14.6%) in the metronidazole group and 13 of the 94 in the placebo group (13.8%) developed postoperative wound infection. Late sepsis was noted in 4 out of the 96 patients in the metronidazole group and in one of the 94 patients in the placebo group. This study suggests that a single intra-operative dose of metronidazole dose not reduce the incidence of postoperative wound infection following appendicectomy for acute mural appendicitis.

Perioperative prophylaxis with sulbactam and ampicillin compared with metronidazole and cefotaxime in the prevention of wound infection in children undergoing appendectomy

Sulbactam is a beta-lactamase inhibitor, which when administered with ampicillin, increases the latter agents antibacterial activity against beta-lactamase producing organisms. One hundred children between the ages of 5 and 14 undergoing emergency appendectomy were entered into a prospective randomized trial comparing sulbactam and ampicillin (SA) with metronidazole and cefotaxime (MC) as prophylaxis against postoperative wound infection. Patients in whom the appendix was perforated or gangrenous received a 72-hour course of antibiotics, others received a single dose only. The overall wound infection rate was 8% (14% in patients with perforation or gangrene and 4% in those without). There was no difference in infection rate between the two antibiotic groups; there were three wound infections and one subphrenic abscess in patients receiving SA and four wound infections in patients receiving MC. SA, therefore, appears to be a suitable antibiotic combination for use as prophylaxis in appendicitis in children.

Metronidazole uptake in the cholesteatomatous membrane in chronic otitis media

Previous investigations have demonstrated a good uptake of metronidazole in the middle ear mucosa. We have now presented a trial study in which there was also a significant uptake of metronidazole in the cholesteatomatous membranes of patients with chronic otitis media.

Evaluation of the use of a protocol in the antimicrobial treatment of intra-abdominal sepsis

A protocol was established aimed at limiting the duration of antimicrobial therapy in two patient groups with peritonitis. One group had perforated or gangrenous appendicitis and the other non-appendiceal disease. The duration of treatment given to patients treated according to the protocol was compared retrospectively to that of similar patients treated without the protocol. Patients with perforated or gangrenous appendicitis required significantly less antimicrobial therapy than those with peritonitis due to non-appendiceal disease. In non-appendiceal intra-abdominal sepsis the use of the protocol was associated with a significantly reduced duration of antimicrobial therapy, compared with that observed without the protocol.

The bacteriology and septic complication of patients with appendicitis

A detailed bacteriologic study was done on 161 patients operated for appendicitis. Aerobic and anaerobic cultures were taken from the blood, the appendicular lumen, mucosa, serosa, fossa, and from the wound after closure of the peritoneum. There is no correlation between the degree of appendicitis and the incidence of positive blood culture. The infection spread through the appendicular wall as the disease progressed. Aerobic infection was common in early appendicitis but a mixed aerobic and anaerobic infection was predominant in late cases. Late appendicitis, a positive wound culture at the end of the operation, the duration of symptoms of over 36 hours before operation and the age of the patient over 50 years were all associated with an increased incidence of septic complication. From the antibiotic sensitivity on the bacteria isolated, the most effective agent against anaerobes was metronidazole. Effective agents against the aerobes were aminoglycosides and cephalosporins. The best single agent against both anaerobes and aerobes was moxalactum.

Surgical antimicrobial prophylaxis: principles and guidelines

Antimicrobial prophylaxis for surgical procedures is an area that is recognized as being subject to individual clinical variations. This review gives practitioners some basic principles of rational prophylaxis as defined by the medical literature. In addition, this literature is evaluated and condensed to provide clinicians with guidelines for particular procedures: obstetric, gynecologic, gastric, biliary, colonic, urologic, cardiac, thoracic, vascular, orthopedic and head and neck. Each section concludes with recommendations for the clinically most accepted prophylactic regimens. Antibiotics discussed include not only the older agents, but where good information exists, the newer cephalosporins. The suggested regimens consider efficacy, safety and cost as determinants in rational prescribing. Although research into even shorter, and perhaps more cost-effective, regimens continues, this compilation lists state-of-the-art recommendations.

The appendix stump: should it be invaginated?

In a prospective trial of 103 patients undergoing appendicectomy, one group of patients had the appendix stump treated by ligation alone and the other group underwent ligation and invagination. The two groups of patients were similar with respect to age, sex, incision and degree of inflammation of the appendix. Perforated appendices were excluded and in neither group were drains used or antibiotics given. No significant difference between the two methods of treatment of the appendix stump was noted, either with respect to wound infection or postoperative stay in hospital.

Prophylaxis of postappendicectomy sepsis by metronidazole and cefotaxime; a randomized, prospective and double blind trial

A randomized, prospective and double blind trial was conducted on 308 patients. Thirty-one out of 102 patients receiving metronidazole developed wound infection compared with 13 out of 103 patients receiving cefotaxime and 14 out of 103 patients receiving metronidazole and cefotaxime. The reduction in the wound sepsis by the use of cefotaxime or a combination of metronidazole and cefotaxime was statistically significant when compared with patients who received metronidazole only. For early cases including normal, acutely inflamed and gangrenous appendices, we gave a single dose of antibiotics just before operation. For late cases with perforation and abscess formation, the antibiotics were continued for 5 days. There was no statistical difference in wound infection between patients who received cefotaxime alone and these who received a combination of metronidazole and cefotaxime.

Metronidazole v. cefoxitin in severe appendicitis--a trial to compare a single intraoperative dose of two antibiotics given intravenously

In severe appendicitis, the effect of a single intravenous dose of metronidazole (500 mg) was compared with cefoxitin (1 g). The antibiotics were given by random allocation once the diagnosis had been established at operation. In the metronidazole group, 5 out of 48 patients developed a wound infection whilst in hospital compared with 13 out of 48 in the cefoxitin group (P = 0.036). However, 57% of wound infections became apparent after the patient went home and the overall infection rates were similar. The mean length of postoperative hospital stay was 5.0 days in the metronidazole group and 6.8 days in the cefoxitin group (P = 0.052), but of those who did develop a wound infection, the length of stay was almost double in the cefoxitin group. Anaerobic organisms were cultured from the wound in 7 out of 15 patients who received cefoxitin but in none of 5 patients in the metronidazole group. Whilst metronidazole only delayed the discharge of pus from the wound, it did seem to reduce the severity of infection. Cefoxitin appeared to be less effective, given as a single intravenous injection at a dose of 1 g.

The prevention of postappendicectomy sepsis by metronidazole and cotrimoxazole: a controlled double blind trial

A double-blind, randomized controlled trial was carried out in University Hospital, Kuala Lumpur to study the effect of metronidazole and cotrimoxazole on the incidence of wound infection following appendicectomy from November 1978 to January 1980. Patients were allocated at random into one of four groups: cotrimoxazole injection and placebo suppository, metronidazole suppository and cotrimoxazole injection, metronidazole suppository and placebo injection or placebo suppository and placebo injection. Treatment was started 30 min before operation and continued for 72h. All patients were followed up for 2 weeks and thereafter for one month. A total of 283 patients was finally accepted into the study. Sepsis rates were found to be 27% for the untreated group, 9% for the group receiving metronidazole only, 8% for the group receiving cotrimoxazole injection only and 2.7% for the group receiving both drugs. The study showed that a combination of metronidazole and cotrimoxazole is a regime highly effective for prophylaxis against wound infection following appendicectomy.

Metronidazole and ticarcillin in the prevention of sepsis after appendicectomy

Ticarcillin was compared with metronidazole in the prevention of wound infection after appendicectomy. Two hundred nine patients with a diagnosis of acute appendicitis were admitted to a prospective, randomized study and received 500 mg of metronidazole or 5 g of ticarcillin intravenously before operation. Those patients with gangrenous or perforated appendices received two additional doses of the trial drug at 8 hourly intervals. The overall incidence of wound infections in both the metronidazole and the ticarcillin groups was 9 percent. There were no intraabdominal abscesses. Metronidazole abolished anaerobic wound infections. All the early wound infections (between 2 and 4 days after operation) occurred in patients with gangrenous or perforated appendices. We conclude that ticarcillin is as effective as metronidazole in the prevention of wound infection after appendicectomy, but in high-risk patients, (those with gangrenous or perforated appendices) longer courses of antibiotics should be employed.

Rectal administration of metronidazole in severely ill patients

Ten severely ill patients with life threatening sepsis received metronidazole as suppositories and blood concentrations of the drug were measured twice daily over five days. Therapeutic blood concentrations of metronidazole were maintained at all times in all patients. Rectal administration of metronidazole is accepted as effective prophylaxis against infection associated with surgery and as treatment of established infection. This study shows that in gravely ill patients metronidazole administered as suppositories gives perfectly adequate therapeutic serum concentrations of the drug, but that to achieve these concentrations rapidly the first suppository should be given with an intravenous loading dose.

Intra-abdominal pneumococcal abscess

A 25-year-old woman with the adrenogenital syndrome was admitted to hospital because of abdominal pain. Streptococcus pneumoniae was present in pus obtained from an abscess in the appendix area.

Prophylaxis of post-appendicectomy sepsis by metronidazole and ampicillin: a randomized, prospective and double-blind trial

Two hundred and eighty-three patients were admitted to a randomized, prospective and double-blind trial of the effect of the addition of ampicillin to metronidazole in the prophylaxis of post-appendicectomy wound sepsis. Nineteen out of 142 patients in the metronidazole and ampicillin group developed wound sepsis compared with 33 out of 141 patients in the metronidazole group. The difference is statistically significant. Early cases, including normal, acutely inflamed and gangrenous appendices, received 2 doses of antibiotics. In late cases with perforation and abscess formation, the antibiotics were continued for 1 week. The difference in wound infection in each of these 2 subgroups was also statistically significant. The commonest organisms isolated from the appendicular fossa and the infected wounds were Escherichia coli and Bacteroides fragilis.

Effects of prophylactic antibiotics on wound infection after elective colon and rectal surgery: 1960 to 1980

Wound infection continues to be a common complication of elective colon and rectal surgery. During the period from 1960 to 1980, 42 prospective, controlled prophylactic antibiotic trials were undertaken which addressed this problem. In this report we have analyzed these trials and compared them to all noncontrolled, prospective wound infection surveys and a representative sample of the retrospective surveys of the same period. From this analysis several conclusions have become apparent: (1) wound infection remains a common complication for which prophylactic antibiotics are generally effective, (2) the most effective agents are those with activity against anaerobic bacteria, (3) orally administered nonabsorbable antibiotics have little effect on reducing wound infection following these procedures, and (4) the optimal antibiotic regimen is yet to be found. The data do suggest, however, the more preferred regimens currently available as well as those worthy of further investigation.

The prophylactic use of antimicrobials in surgery

During the period August 1976 to June 1982, there were 98 reports of antimicrobial prophylaxis in human surgery that were judged unevaluable. Our review, coupled with that of Chodak and Plaut, identified studies of 126 antibiotic regimens that were considered evaluable and a total of 205 studies considered unevaluable. A decrease in infection rate in antibiotic-treated patients compared to non-antibiotic-treated patients was seen in 120 (95%) of the evaluable regimens. Ninety-nine (79%) of these 120 regimens produced statistically significant reductions in the infection rate (P less than .05, chi 2 analysis). The majority of the antibiotic regimens were tested in procedures that were classified as clean-contaminated. Of the regimens that yielded a statistically significant reduction in infection rate with antimicrobial therapy, in 66 (67%) the agents were used for 24 hours or less. Five regimens were identified in which a higher infection rate occurred in specific patient groups when prophylactic antibiotics were used, but the differences were not statistically significant. In the overwhelming majority of evaluable studies, antibiotics decreased the incidence of surgical infection compared with non-antibiotic groups. The available data also support the effectiveness of short prophylactic antibiotic courses of 24 hours' duration or less. The duration necessary for antibiotic prophylaxis was specifically tested in nine regimens. In all nine, a short course (less than 24 hours) of antibiotic prophylaxis was as effective as longer periods of therapy (24 hours to 5 days) in preventing infection.

A double-blind controlled trial of metronidazole suppositories in children undergoing appendicectomy

A total of 133 children, aged 16 months to 15 years (mean 6.7 years), with presumptive acute appendicitis, was included in a double-blind, placebo-controlled trial of the short-term (72 hour) use of metronidazole suppositories as prophylaxis against post-operative infection. There was no significant difference in the incidence or severity of wound infection or post-operative intra-abdominal sepsis between the metronidazole-treated and placebo groups. It is suggested that intra-rectal metronidazole, when used exclusively, is not sufficient for effective prophylaxis for appendicitis in childhood.

Cephalothin, cefoxitin, or metronidazole in elective colonic surgery? A single-blind randomized trial

A randomized controlled trial aimed at comparing the individual efficacy of cephalothin, cefoxitin, and metronidazole in the prevention of postoperative wound infection was performed among 74 colorectal surgical patients. Of 28 patients on cephalothin, seven (25 per cent) developed a postoperative infection, but among 23 patients in each of the other two groups, only one (4 per cent) in each group became infected. These results confirm the primary importance of anaerobes in the causation of postoperative sepsis after colorectal surgery.

Short time prophylaxis with ornidazole in elective colo-rectal surgery

A study of 100 patients given short time prophylaxis against anaerobic infections in association with colo-rectal surgery is presented. The patients were randomly allocated into two groups receiving either ornidazole (Tiberal) or doxycycline (Vibramycin) for 3 days. Ornidazole concentrations in serum, subcutaneous fat, and intestinal wall were measured in 10 patients. No infection of anaerobic etiology was noticed in the ornidazole group, in contrast to 5 anaerobic infections in the doxycycline group. This difference is statistically significant (p less than 0.05). The pharmacokinetic results indicate that a 3-day treatment with ornidazole gives a sufficient plasma steady state concentration, while the preoperative loading dose should be given less than 24 h prior to operation. The necessity of prophylaxis against both aerobic and anaerobic infections in colo-rectal surgery is emphasized.

Metronidazole phosphate--a water-soluble prodrug for parenteral solutions of metronidazole

To develop a parenteral solution of relatively water-insoluble metronidazole (2-methyl-5-nitro-1H-imidazole-1-ethanol), its phosphate ester was synthesized via two routes. One route utilized 2-cyanoethyl phosphate and the other utilized pyrophosphoryl tetrachloride. The first method used dicyclohexylcarbodiimide as a coupling agent and the cyanoethyl group was removed under mild alkaline conditions. The second method was a one-step procedure in which free acid of metronidazole phosphate was isolated as a crystalline solid. The solubility of metronidazole in various solvents was determined at 25 degrees. From the pH-dependence of its aqueous solubility, the pKa of the conjugate acid of metronidazole was estimated to be 2.62, which agreed well with the pKa values of other nitroimidazoles. Metronidazole phosphate behaved as a zwitterionic compound in an acidic medium with a minimum solubility at pH 2.0. At pH 7, its solubility was approximately 50 times that of metronidazole. The phosphate ester was so soluble at pH higher than 7 that it was difficult to measure the solubility accurately. In human serum, the hydrolysis of metronidazole phosphate followed zero-order kinetics at an initial concentration of 0.25 mg/ml or higher, presumably due to enzyme saturation (0.035 mg/ml/hr at 37 degrees). A reversed-phase HPLC procedure was adopted to monitor the appearance of metronidazole and the disappearance of metronidazole phosphate. Subcutaneous administration of metronidazole phosphate to rats produced a blood level of bioactivity comparable to that observed after administration of metronidazole.

Delayed primary wound closure in gangrenous and perforated appendicitis

A prospective randomized trial was performed on 122 patients with perforated or gangrenous appendicitis to determine whether delayed primary wound closure lowered morbidity from wound infection. The 54 per cent wound infection rate with delayed primary closure was significantly inferior to the 18 per cent infection rate for primary closure with topical ampicillin powder (P = 0.0082), but not significantly different from the 37 per cent infection rate for primary closure alone. Furthermore, patients disliked delayed primary closure, their hospital stay was prolonged and 17 per cent of their wounds became contaminated with Staphylococci before being closed. Delayed primary wound closure should not be used in treating perforated and gangrenous appendicitis wounds.