Structure-activity analysis of synthetic autoinducing thiolactone peptides from Staphylococcus aureus responsible for virulence

The synthesis of virulence factors and other extracellular proteins responsible for pathogenicity in Staphylococcus aureus is under the control of the agr locus. A secreted agr-encoded peptide, AgrD, processed from the AgrD gene product, is known to be an effector of self-strain activation and cross-strain inhibition of the agr response. Biochemical analysis of AgrD peptides isolated from culture supernatants has suggested that they contain an unusual thiol ester-linked cyclic structure. In the present work, chemical synthesis is used to confirm that the mature AgrD peptides contain a thiolactone structure and that this feature is absolutely necessary for full biological activity. The AgrD synthetic thiolactone peptides exhibited biological activity in vivo in a mouse protection test. Structure-activity studies have allowed key aspects of the peptide structure involved in the differential activation and inhibition functions to be identified. Accordingly, we propose a model for activation and inhibition of the agr response in which the former, but not the latter, involves specific acylation of the agr transmembrane receptor, AgrC.

Preoperative oral antibiotics reduce septic complications of colon operations: results of prospective, randomized, double-blind clinical study

The effectiveness of short-term, low-dose, preoperative oral administration of neomycin and erythromycin base combined with vigorous purgation in reducing the incidence of wound infections and other septic complications of elective colon and rectal operations has been studied in a prospective, randomized, double-blind, clinical trial. One hundred and sixteen patients completed the study; all received mechanical preparation; 56 received neomycin-erythromycin base while 60 received an identical appearing placebo. The two patient groups were comparable in age distribution, clinical diagnoses, associated systemic diseases, types of operation performed and similar clinical features. The overall rate of directly related septic complications was 43 per cent in the placebo group and 9% in the group receiving neomycin and erythromycin base. The wound infection rates were 35% in placebo and 9% in antibiotic treated patients. Oral administration of neomycin and erythromycin base together with vigorous mechanical cleansing reduces the risk of septic complications after elective colo-rectal operations.

Vaccine assembly from surface proteins of Staphylococcus aureus

Staphylococcus aureus is the most common cause of hospital-acquired infection. Because of the emergence of antibiotic-resistant strains, these infections represent a serious public health threat. To develop a broadly protective vaccine, we tested cell wall-anchored surface proteins of S. aureus as antigens in a murine model of abscess formation. Immunization with four antigens (IsdA, IsdB, SdrD, and SdrE) generated significant protective immunity that correlated with the induction of opsonophagocytic antibodies. When assembled into a combined vaccine, the four surface proteins afforded high levels of protection against invasive disease or lethal challenge with human clinical S. aureus isolates.

Microbiology and management of peritonsillar, retropharyngeal, and parapharyngeal abscesses

This review describes the microbiology, diagnosis, and management of peritonsillar, retropharyngeal, and parapharyngeal abscesses in children. Predominant anaerobic organisms isolated in peritonsillar, lateral pharyngeal, and retropharyngeal abscesses are Prevotella, Porphyromonas, Fusobacterium and Peptostreptococcus spp.; aerobic organisms are group A streptococcus ( Streptococcus pyogenes ), Staphylococcus aureus and Haemophilus influenzae . Anaerobic bacteria can be isolated from most abscesses whenever appropriate techniques for their cultivation have been used, while S. pyogenes is isolated in only about one third of cases. More than two thirds of deep neck abscesses contain beta-lactamase producing organisms. Management of tonsillar, peritonsillar, and retropharyngeal abscesses is similar. Systemic antimicrobial therapy should be given in large doses whenever the diagnosis is made. However, when pus is formed, antimicrobial therapy is effective only in conjunction with adequate surgical drainage. Untreated abscesses can rupture spontaneously into the pharynx, causing catastrophic aspiration. Other complications are extension of infection laterally to the side of the neck or dissection into the posterior mediastinum through facial planes and the prevertebral space. Death can occur from aspiration, airway obstruction, erosion into major blood vessels, or extension to the mediastinum.

Experimental bacteriophage protection against Staphylococcus aureus abscesses in a rabbit model

In a rabbit model of wound infection caused by Staphylococcus aureus, 2 x 10(9) PFU of staphylococcal phage prevented abscess formation in rabbits when it was injected simultaneously with S. aureus (8 x 10(7) CFU) into the same subcutaneous site. Phage multiplied in the tissues. Phages might be a valuable prophylaxis against staphylococcal infection.

Long-term 6-mercaptopurine treatment in adolescents with Crohn's disease

Although 6-mercaptopurine is often used to treat adolescents with intractable Crohn's disease, its long-term efficacy has not yet been studied in this population. This study shows data derived from 36 adolescents (mean age +/- SD, 16.5 +/- 3.3 years; 27 males, 9 females) treated at least 6 months with 6-mercaptopurine (1.5 mg.kg-1.day-1, maximum of 75 mg/day). Sites of Crohn's disease at the start of 6-mercaptopurine therapy included 17 ileocolic, 9 pancolic, 7 small bowel, and 3 partial colon. All had received corticosteroids, sulfasalazine, antibiotics, and nutritional support for 5.0 +/- 3.0 years before administering 6-mercaptopurine, but intractable symptoms persisted. Disease activity lessened during the first year of 6-mercaptopurine, reflected by a higher Lloyd-Still disease activity score (pre, 64 +/- 9 vs. 6-mercaptopurine, 72 +/- 11; P less than 0.0001). General activity, physical examination, nutrition, and laboratory subscores all improved (P less than 0.004). Lessened disease activity occurred despite concomitant decrease in duration of prednisone use (pre, 9.5 +/- 4.2 vs. 6-mercaptopurine, 6.6 +/- 4.9 months/year; P less than 0.001) and cumulative annual prednisone exposure (pre, 3672 +/- 2106 vs. 6-mercaptopurine, 1964 +/- 1460 mg; P less than 0.0007). The frequency of perianal fistulae and abscesses also decreased (P less than 0.01) during treatment. Annual rates of hospitalization decreased in 44% of subjects during 6-mercaptopurine treatment, while increasing in only 22%. Follow-up beyond 1 year of 6-mercaptopurine treatment showed continued remission in 23 of 30 subjects. No serious complications were seen. 6-mercaptopurine is an effective long-term therapy for adolescents with intractable Crohn's disease. While inducing remission, it also has a significant steroid-sparing effect which may be of particular benefit to this population.

Human skin flora as a potential source of epidural abscess

BACKGROUND

The mechanism of epidural infection associated with epidural block is not clearly understood. Resident organisms in skin specimens were studied after skin was prepared with disinfectants.

METHODS

Sixty-nine paired skin specimens were excised at incisional sites after skin disinfection with 10% povidone-iodine (10% PVP-I) or 0.5% chlorhexidine in 80% ethanol (0.5% CHE) from 60 patients having back surgery. One of the specimen pairs was placed in 10 ml brain-heart infusion broth and incubated in air at 37 degrees C for 96 h. The other specimen was sectioned at 3 microns and prepared with Gram's stain for examination with the microscope.

RESULTS

Thirteen gram-positive staphylococcal species (Staphylococcus epidermidis, 69.2%; S. hyicus, 15.4%; and S. capitis, 15.4%) were isolated from cultures. The isolates were found in a significantly greater proportion of the skin specimens disinfected with 10% PVP-I than in those disinfected with 0.5% CHE (11 of 34 cultures [32.4%] vs. 2 of 35 cultures [5.7%]; P < 0.01). Many gram-positive cocci were observed with the microscope in 4 (11.8%) and 5 (14.3%) of 34 and 35 skin specimens disinfected with 10% PVP-I and 0.5% CHE, respectively. The cocci formed a dense colony in each follicle and in the stratum corneum. No organism was present in any of 17,584 sweat glands examined.

CONCLUSIONS

In a large proportion of patients, isolation of viable organisms from excised skin specimens after disinfection with 10% PVP-I suggests that contamination of the epidural space by the skin flora may be a potential mechanism of epidural infection associated with epidural block.

T cells activated by zwitterionic molecules prevent abscesses induced by pathogenic bacteria

Immunologic paradigms classify bacterial polysaccharides as T cell-independent antigens. However, these models fail to explain how zwitterionic polysaccharides (Zps) confer protection against intraabdominal abscess formation in a T cell-dependent manner. Here, we demonstrate that Zps elicit a potent CD4+ T cell response in vitro that requires available major histocompatibility complex class II molecules on antigen-presenting cells. Specific chemical modifications to Zps show that: 1) the activity is specific for carbohydrate structure, and 2) the proliferative response depends upon free amino and carboxyl groups on the repeating units of these polysaccharides. Peptides synthesized to mimic the zwitterionic charge motif associated with Zps also exhibited these biologic properties. Lysine-aspartic acid (KD) peptides with more than 15 repeating units stimulated CD4+ T cells in vitro and conferred protection against abscesses induced by bacteria such as Bacteroides fragilis and Staphylococcus aureus. Evidence for the biologic importance of T cell activation by these zwitterionic polymers was provided when human CD4+ T cells stimulated with these molecules in vitro and adoptively transferred to rats in vivo conferred protection against intraabdominal abscesses induced by viable bacterial challenge. These studies demonstrate that bacterial polysaccharides with a distinct charge motif activate T cells and that this activity confers immunity to a distinct pathologic response to bacterial infection.

Therapeutic efficacy of 29 antimicrobial regimens in experimental intraabdominal sepsis

An animal model of colonic perforation was used to examine the efficacy of 29 antimicrobial regimens in the treatment of intraabdominal sepsis. Efficacy was judged on mortality during the first 12 days after challenge and on the incidence of intraabdominal abscess noted at necropsy upon completion of the experiment. In general, antimicrobial agents that are active against coliform bacteria prevented early mortality, whereas drugs that are active against Bacteroides fragilis were most effective in reducing the incidence of late abscess formation. Exceptions were metronidazole, which produced a significant reduction in early mortality, and chloramphenicol, which caused only a modest reduction in the incidence of abscess. Optimal results were obtained with several regimens that showed good in vitro activity against both coliforms and B. fragilis.

Some aspects of tick-borne diseases of British sheep

The significance of tick-borne fever (TBF) and other tick-borne diseases of British sheep are reviewed. Experimental and field studies were carried out to clarify the role of TBF as a pathogen per se and as a predisposing factor in other diseases. Experimental TBF infection caused anorexia and depression in two- to three-week-old lambs, which under the stress of a hill environment could alone be a cause of mortality. Nine out of 10 lambs experimentally inoculated with Staphylococcus aureus during the febrile phase of a TBF reaction developed pyaemic lesions compared with four out of 20 lambs inoculated with S aureus alone. Specific pathogen-free lambs inoculated with an aerosol of Pasteurella haemolytica serotype A1 during a TBF reaction showed more severe clinical signs and had more extensive pathological changes at necropsy than control lambs given P haemolytica alone. Dual infection with TBF and louping-ill virus showed that not only were dually infected sheep more susceptible to louping-ill but almost all of them succumbed to a haemorrhagic syndrome involving a systemic mycotic infection with Rhizomucor pucillus. None of eight sheep given louping-ill virus alone developed this syndrome. Field studies indicated that morbidity and mortality in lambs in south-west Scotland could be markedly reduced by dipping and long acting antibiotic prophylaxis. Lamb groups in which both of these were carried out incurred losses of only 0.6 per cent compared with 10.3 per cent in control groups. In addition antibiotic-treated lamb groups demonstrated significantly better weight gains than untreated groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for T cell-dependent immunity to Bacteroides fragilis in an intraabdominal abscess model

It has been shown that active immunization of rats with the capsular polysaccharide of Bacteroides fragilis protects these animals against abscess development following intraperitoneal challenge with this species. Passive transfer of hyperimmune globulin from immunized animals to nonimmune recipients provided protection against B. fragilis bacteremia in challenged animals, but did not confer protection against abscess development. On the other hand, adoptive transfer of spleen cells from immunized animals to nonimmunized recipients resulted in protection against abscesses following challenge with B. fragilis. These data suggested that a T cell-dependent immune response was involved in protection against abscess development after immunization with B. fragilis capsular antigen. To determine the possible role of cell-mediated immunity prompted by the capsular antigen, inbred congenitally athymic OLA/Rnu rats and their phenotypically normal littermates were actively immunized. Despite the development of high titers of anti-B. fragilis capsular antibody, 100% of actively immunized athymic rats developed abscesses, as did 100% of unimmunized athymic control rats. However, no phenotypically normal littermate control rats that were actively immunized developed abscesses, while 100% of phenotypically normal unimmunized rats developed abscesses. Additional studies showed that adoptive transfer of T cell-enriched spleen cell preparations from Wistar/Lewis rats immunized with the capsular polysaccharide to nonimmune recipients also resulted in protection against B. fragilis-induced abscesses. We conclude that the protection afforded by immunization with B. fragilis capsule against intraabdominal abscesses caused by that organism is T cell-mediated and does not require the presence of serum antibody.

Role of fibrin deposition in the pathogenesis of intraabdominal infection

The production of fibrinous exudates plays an important role in determining the outcome of peritoneal infection. Large numbers of bacteria are sequestered within fibrin matrices, thereby retarding bacterial spread throughout the peritoneal cavity and into the bloodstream. This walling-off process is teleologically advantageous in that it lessens early rapid mortality. Recent studies have documented that this same process is probably integral to the development of residual infection in the peritoneum. Bacteria sequestered within fibrin deposits are protected from normal host clearance mechanisms, thereby permitting unopposed proliferation and ultimately the establishment of an abscess. A complete understanding of the cellular and noncellular aspects of the host response to peritoneal infection will suggest novel strategies both to treat and to prevent the development of intraabdominal abscesses and their attendant consequences.

Evaluation of antibiotic therapy following penetrating abdominal trauma

Postoperative infection accounts for significant morbidity and mortality following penetrating abdominal trauma. During a 2 1/2-year period, December 1980 through June 1983, 257 patients sustaining penetrating abdominal injury were initially treated at Parkland Memorial Hospital in Dallas. Following the patient's written consent, they were prospectively randomized to receive, prior to surgery, intravenous clindamycin 600 mg every 6 hours and tobramycin 1.2 mg/kg every 6 hours (CT), or cefamandole 1 gm every 4 hours (M), or cefoxitin 1 gm every 4 hours (C). The antibiotics were continued for 48 hours. Major organ injuries in the three groups were comparable. The overall infection rate was significantly less in the cefoxitin group (13%), compared to cefamandole at 29%, and was comparable to the combination of clindamycin/tobramycin at 20%. The most significant difference followed colon injury. There were 96 patients who sustained colon injuries and the infection rate was CT 33%, M 62%, and C 19% (p = 0.002). If nonoperative wound infections were excluded from the colon group and only severe infections were evaluated, the infection rate was CT 18%, M 38%, and C 13% (p = 0.021). The infection rate was higher in the shock patients and tended to increase as age increased. Enterococcus, Escherichia coli, and Klebsiella pneumoniae were the most frequent aerobes isolated along with anaerobes. Five of six Bacteroides isolates from major infections occurred in the cefamandole group; two of which were in bacteremic patients. The hospital stay corresponded with infection rates, being 11.4 days (CT), 13.1 days (M), and 9.4 days (C). The results of this study indicate that cefoxitin is comparable to the combination of clindamycin/tobramycin and superior to cefamandole when used before surgery in patients sustaining penetrating abdominal trauma. The study suggests that antibiotic coverage should be against aerobes and anaerobes. Routine administration of an aminoglycoside is unnecessary.

Superiority of closed suction drainage for pancreatic trauma. A randomized, prospective study

During a 42-month period, 65 patients sustaining pancreatic injuries were treated. They were randomized on alternate days (two separate trauma teams) to receive sump (S) or closed suction (CS) drainage. Twenty-eight patients were randomized to S and 37 to CS; there were six early deaths, which precluded drainage analysis, leaving 24 evaluable S patients and 35 CS patients. Penetrating wounds occurred in 71% and blunt in 29%. No significant differences appeared between the groups with respect to age, Penetrating Abdominal Trauma Index (PATI), Injury Severity Score (ISS), or grade of pancreatic injury. Twelve patients in each group required resection and drainage for grade III injuries, with the remaining patients receiving external drainage alone. Five of twenty-four S patients versus one of thirty-five CS patients developed intra-abdominal abscesses (p less than 0.04). We conclude that septic complications after pancreatic injury are significantly reduced by CS drainage. Bacterial contamination via sump catheters is a major source for intra-abdominal infections after pancreatic trauma.

Long peritoneal lavage decreases pancreatic sepsis in acute pancreatitis

Late infection of devitalized pancreatic and peripancreatic tissue has become the major cause of morbidity in severe acute pancreatitis. Previous experience found that peritoneal lavage for periods of 48 to 96 hours may reduce early systemic complications but did not decrease late pancreatic sepsis. A fortunate observation led to the present study of the influence of a longer period of lavage on late sepsis. Twenty-nine patients receiving primary nonoperative treatment for severe acute pancreatitis (three or more positive prognostic signs) were randomly assigned to short peritoneal lavage (SPL) for 2 days (15 patients) or to long peritoneal lavage (LPL) for 7 days (14 patients). Positive prognostic signs averaged 5 in both groups but the frequency of five or more signs was higher in LPL (71%) than in SPL (47%). Eleven patients in each group had early computed tomographic (CT) scans. Peripancreatic fluid collections were shown more commonly in LPL (82%) than in SPL (54%) patients. Longer lavage dramatically reduced the frequency of both pancreatic sepsis (22% LPL versus 40% SPL) and death from sepsis (0% LPL versus 20% SPL). Among patients with fluid collections on early CT scan, LPL led to a more marked reduction in both pancreatic sepsis (33% LPL versus 83% SPL) and death from sepsis (0% LPL versus 33% SPL). The differences were even more striking among 17 patients with five or more positive prognostic signs. In this group the incidence of pancreatic sepsis was 30% LPL versus 57% SPL and of death from sepsis 0% (LPL) versus 43% (SPL) (p = 0.05). In these patients, overall mortality was also reduced (20% LPL versus 43% SPL). When 20 patients treated by LPL were compared with 91 other patients with three or more positive prognostic signs who were treated without lavage or by lavage for periods of 2 to 4 days, the frequency of death from pancreatic sepsis was reduced from 13% to 5%. In those with five or more signs, the incidence of sepsis was reduced from 40% to 27% (p = 0.03) and of death for sepsis from 30% to 7% (p = 0.08). These findings indicate that lavage of the peritoneal cavity for 7 days may significantly reduce both the frequency and mortality rate of pancreatic sepsis in severe acute pancreatitis.

Incision and drainage of perianal abscess with or without treatment of anal fistula

BACKGROUND

The perianal abscess is a common surgical problem. A third of perianal abscesses may manifest a fistula-in-ano which increases the risk of abscess recurrence requiring repeat surgical drainage. Treating the fistula at the same time as incision and drainage of the abscess may reduce the likelihood of recurrent abscess and the need for repeat surgery. However, this could affect sphincter function in some patients who may not have later developed a fistula-in-ano.

OBJECTIVES

We aimed to review the available randomised controlled trial evidence comparing incision and drainage of perianal abscess with or without fistula treatment.

SEARCH STRATEGY

Randomised trials were identified from MEDLINE, EMBASE, the Cochrane Library, and reference lists of published papers and reviews.

SELECTION CRITERIA

Trials comparing outcome after fistula surgery with drainage of perianal abscess compared with drainage alone were included in the review.

DATA COLLECTION AND ANALYSIS

The primary outcomes were recurrent or persistent abscess/fistula which may require repeat surgery and short-term and long-term incontinence. Secondary outcomes were duration of hospitalisation, duration of wound healing, postoperative pain, quality of life scores. For dichotomous variables, relative risks and their confidence intervals were calculated.

MAIN RESULTS

We identified six trials, involving 479 subjects, comparing incision and drainage of perianal abscess alone versus incision and drainage with fistula treatment. Metaanalysis showed a significant reduction in recurrence, persistent abscess/fistula or repeat surgery in favour of fistula surgery at the time of abscess incision and drainage (RR=0.13, 95% Confidence Interval of RR = 0.07-0.24). Transient manometric reduction in anal sphincter pressures, without clinical incontinence, may occur after treatment of low fistulae with abscess drainage. Incontinence at one year following drainage with fistula surgery was not statistically significant (pooled RR 3.06, 95% Confidence Interval 0.7-13.45) with heterogeneity demonstrable between the trials (Chi(2) =5.39,df=3, p=0.14, I(2) =44.4%).

AUTHORS' CONCLUSIONS

The published evidence shows fistula surgery with abscess drainage significantly reduces recurrence or persistence of abscess/fistula, or the need for repeat surgery. There was no statistically significant evidence of incontinence following fistula surgery with abscess drainage. This intervention may be recommended in carefully selected patients.

Antibiotic prophylaxis in acute nonperforated appendicitis. The Danish Multicenter Study Group III

In a prospective, block-randomized, multicenter study, the safety and efficacy of cefoxitin in preoperative prophylaxis were studied. 1735 patients undergoing appendectomy were evaluable, and half of these patients received 2 g of cefoxitin before undergoing operation. The patients were divided into three groups: patients with a normal appendix, patients with an acutely inflamed appendix, and patients with a gangrenous appendix. The study showed for each group a significant reduction of the incidence of wound infection in patients receiving prophylaxis. However, intra-abdominal abscess formation was not influenced by preoperative antibiotic prophylaxis. Consequently, routine preoperative prophylaxis is recommended before appendectomy.

Prophylactic systemic antibiotics in colorectal surgery

The prophylactic value of gentamicin combined with either lincomycin or metronidazole in 52 patients undergoing colorectal surgery was investigated. The results confirmed the value of this practice. In a control group, the sepsis-rate was 48% with 1 death attributable to sepsis, compared with a sepsis-rate of 4% in the treated group. The combination of gentamicin and lincomycin was effective against sepsis but pseudomembranous colitis developed in 2 of the 14 patients treated with this combination of drugs. Lincomycin was discontinued, and when metronidazole was substituted the results were equally good and there were no toxic side-effects.

Zwitterionic polysaccharides stimulate T cells with no preferential V beta usage and promote anergy, resulting in protection against experimental abscess formation

Zwitterionic polysaccharides (Zps) from pathogenic bacteria, such as Bacteroides fragilis, are virulence factors responsible for abscess formation associated with intra-abdominal sepsis. The underlying cellular mechanism for abscess formation requires T cell activation. Conversely, abscess formation can be prevented by prophylactic s.c. injection of purified Zps alone, a process also dependent on T cells. Hence, the modulatory role of T cells in abscess formation was investigated. We show that Zps interact directly with T cells with fast association/dissociation kinetics. Vbeta repertoire analysis using RT-PCR demonstrates that Zps have broad Vbeta usage. Zps-specific hybridomas responded to a variety of other Zps, but not to a nonzwitterionic polysaccharide, indicating cross-reactivity between different Zps. Furthermore, Zps-reactive T cell hybridomas could effectively transfer protection against abscess formation. Analysis of the proliferative capacity of T cells recovered from Zps-treated animals revealed that these T cells are anergic to subsequent stimulation by the different Zps or to alloantigens in an MLR. This anergic response was relieved by addition of IL-2. Taken together, the data show that this class of polysaccharides interacts directly with T cells in a nonbiased manner to elicit an IL-2-dependent anergic response that confers protection against abscess formation.

Pentoxifylline in the treatment of experimental peritonitis in rats

The objective of this study was to determine the effect of pentoxifylline on the clinical and pathologic course of experimentally induced peritonitis in rats. This drug is a methyxanthine derivative that has vasodilating properties and may decrease platelet aggregation. Peritonitis was induced in 40 Wistar rats by creating a closed ileal loop 4 cm long 5 cm from the ileocecal valve. The animals were divided into two groups of 20 animals each. The first group served as controls, while each animal of the second group received 17 mg/kg/day of pentoxifylline intramuscularly from the day of operation until 30 days postoperatively. The survival rate was significantly increased in the group receiving pentoxifylline and adhesion or abscess formation was considerably reduced. We concluded that the administration of pentoxifylline prolongs significantly the survival of animals with experimental peritonitis and reduces the development of adhesions and abscesses in the peritoneal cavity. This beneficial effect may be attributed to decreased fibrinogen deposits and increased fibrinolytic activity within the peritoneal cavity, thus rendering the bacteria more susceptible to cellular and noncellular clearing mechanisms.