Enterococcal infections in surgical patients: the mystery continues

The frequency of isolation of enterococci from surgical patients has increased significantly during the past decade, although the role of these organisms as pathogens in mixed infections remains a mystery. Bacteremia and other infections in which enterococci are the only pathogens frequently result in high morbidity and mortality among patients unless specific antimicrobial therapy is initiated promptly. Debate continues concerning the necessity for treatment with such agents when this organism is isolated as a component of a polymicrobial infecting flora. Our recent data indicate that enterococci are rarely isolated in postoperative infections after penetrating abdominal trauma if no gastrointestinal perforation has occurred. However, they were found in 56% of postoperative infections of patients with gastrointestinal perforation. In contrast, enterococci were isolated in only 9% of cultures of specimens from patients with secondary suppurative peritonitis. The occurrence of superinfection after therapy with a cephalosporin appears to be an important factor in this finding. Future studies are necessary to evaluate the efficacy of antibiotic treatment of enterococcal infections and to assess the need for prophylaxis against enterococci.

Autotransfusion of potentially culture-positive blood (CPB) in abdominal trauma: preliminary data from a prospective study

Increased use of autotransfusion for traumatic hemorrhage may reduce amounts of banked blood needed for severe injuries. Autotransfusion is standard for traumatic hemothorax, but has been limited for abdominal injuries. This prospective study used microbiologic data from 152 patients with intestinal injuries. Where anticipated blood loss was greater than 1,000 mL, blood from the peritoneal cavity was cultured, washed, concentrated, and recultured before reinfusion. Infection rates were stratified using the Penetrating Abdominal Trauma Index (PATI). Fifty patients with PATI greater than 20 who received banked blood (group I) (mean: 1,800 mL) were compared with 20 patients (group II) who received autotransfused, potentially culture-positive blood (CPB) (mean: 3,900 mL). Wound infection rates were identical in both groups (25%). No statistically significant increase was found in site-specific infection risk when severity of injury was stratified according to PATI. Bacteremias, pulmonary infections, and urinary infections were not caused by bacteria cultured from autotransfused blood. We conclude that washed CPB may be autotransfused without significantly increased risk of infection in patients with severe abdominal injuries.

Surgical wound infection

Wound infections remain a major source of postoperative morbidity, accounting for about a quarter of the total number of nosocomial infections. Today, many of these infections are first recognized in the outpatient clinic or in the patient's home due to the large number of operations done in the outpatient setting. This leads to errors in establishing the true incidence of their occurrence but undoubtedly decreases the overall real cost and length of hospital stay. The pathogens implicated in the development of wound infections remain largely the human microorganisms from the exogenous environment and the endogenous organ microflora. Many perioperative factors have been identified that increase the incidence of the development of postoperative wound infection. Avoidance of these factors as well as the appropriate use of perioperative antibiotic prophylaxis has decreased the incidence of wound infection. During the last decade many studies have reported on the individual risk factors that favor the development of postoperative infectious complications in various surgical procedures. It is hoped that this knowledge may allow for prospective alterations in the preventative and therapeutic modalities in the high-risk patient in the studies designed in the 1990s. The use of effective infection surveillance both in the hospital and in the outpatient setting is mandatory in order to collect meaningful data. The use of computer technology will greatly facilitate the proper surveillance, analysis, and control of infections in the surgical patient.

A new coaxial needle for pre-operative localization of breast abnormalities

A new coaxial needle, containing a retractable anchoring wire with a helical tip, has been developed for purposes of mammographic and sonographic localization of non-palpable suspicious breast abnormalities before surgical excision. The helically shaped tip provides the needle with a number of potential advantages over other currently available localization needles. During in vitro comparisons with other needles quantitative and qualitative evidence was obtained to suggest that the new needle can be expected to have improved anchoring capability, be deflected less by tough fibrous tissue interfaces and be more visible sonographically. The anchoring wire can also be retracted and repositioned. Preliminary clinical experience with the needle was consistent with these expectations.

Use of third-generation cephalosporins. Anaerobes

The third-generation cephalosporins have an increased spectrum of activity against gram-negative bacteria, moderate activity against anaerobic bacteria, and reduced anti-gram-positive activity as compared with earlier cephalosporins. This spectrum allows the drugs to be considered as monotherapy for the treatment of mixed aerobic-anaerobic infections and as prophylaxis in patients in whom such mixed flora are expected. In vitro testing of anaerobes with the third-generation cephalosporins shows susceptibility to be method dependent, with regional differences also observed. The microtube broth dilution method shows the best relationship to in vivo results. Moreover, the apparent in vitro susceptibility or resistance does not always correlate with clinical efficacy. Clinical studies indicate that the expanded-spectrum third-generation cephalosporins may be used in place of combination therapy in patients with polymicrobial infection or as prophylaxis when mixed microflora are expected.

Barrier efficiency of surgical gowns. Are we really protected from our patients' pathogens?

Surgical gowns are traditionally worn to protect patients from contamination by the surgical team. Blood routinely covers gowns during surgery and often contaminates surgeons' undergarments and skin. Because of risks to the surgical team by blood-borne pathogens, disposable and reusable gowns were examined. To quantify "strike through," 1440 samples of gown fabric were tested against human blood in an apparatus designed to simulate abdominal pressure during surgery. Representative pressures (0.25 to 2.0 psi) and times (1 second to 5 minutes) were studied. Above 0.5 psi, spun-bond/melt-blown/spun-bond disposable products were more resistant than spun-lace cloth. New cloth gowns were better than those washed 40 times. Spun-bond/melt-blown/spun-bond fabric exposed to blood twice was more protective than spun-lace cloth challenged once. Gowns currently available exhibit varying resistance to strike through; only those with an impervious plastic reinforcement offer complete protection.

Infections and sepsis in disasters

It seems reasonable to expect that infections will occur after certain types of disasters. There are some data to support this conjecture in studies of tornadoes, hurricanes, and mass trauma situations. We have tried to extrapolate from these data what we believe will be the infectious effects of different types of disasters, taking into account the potential for alteration in the host secondary to injury, the modification of living conditions, and the possibility of the disruption of medical care.

Intraoperative colonic lavage: failure to decrease mucosal microflora

Few data exist concerning the ability of intraoperative colonic lavage to decrease colonic bacterial counts, and nothing is known about its effect on the recently described mucosa-associated bacteria. The goal of our study was to determine the impact of intraoperative colonic lavage on both the intraluminal and mucosal microflora. After intraoperative colonic washout in 10 adult male Sprague-Dawley rats, quantitative and qualitative aerobic and anaerobic cultures of the intraluminal and mucosal bacteria were obtained. Tissue was also removed for scanning electron microscopic examination of the colon wall. Whereas 1000-fold to 10,000-fold reductions of aerobic and anaerobic intraluminal flora were achieved with mechanical lavage, reductions of aerobic or anaerobic mucosal bacteria were not significant. Failure to diminish bacterial colonization in this ecologic niche may be partly responsible for the persistently high infection rate after emergency colorectal surgery.

Suppression of the human mucosal-related colonic microflora with prophylactic parenteral and/or oral antibiotics

The purpose of this investigation was to assess the effects of preoperative administration of parenteral antibiotics with or without concomitant preoperative administration of oral antibiotics on the colonic mucosal-related microflora. Thirty-one patients were studied in a prospective fashion. Group A patients (n = 8) had colonoscopic mucosal biopsies performed after mechanical bowel preparation. Group B patients (n = 5) received neomycin and erythromycin (NE), 1 g each following mechanical bowel preparation, at 1, 2, and 11 p.m. the evening prior to either elective colon resection (n = 2) or prior to colonoscopic biopsy (n = 3). Emergent trauma patients who had left colon or sigmoid perforations due to gunshot wounds requiring segmental resection comprised group C (n = 7). These patients received cefoxitin or cefotetan 2 g intravenously preoperatively. Individuals in group D (n = 11) all had elective left hemicolectomies or sigmoid resections due to nonobstructing malignancies. These patients underwent the same regimen as group B patients in addition to receiving intravenous cefoxitin perioperatively. Quantitative and qualitative bacterial cultures as well as scanning electron microscopy (SEM) were used to study the mucosa-associated flora. Tissue for culture and SEM were obtained from the pathologic specimen immediately after removal. The interval between the dosage of parenteral antibiotics to tissue removal was 3 hours in both groups. Anaerobic and aerobic counts were suppressed the greatest in patients receiving both oral and parenteral antibiotics (p = 0.0001). Mean anaerobic counts decreased from 3.4 X 10(7) in group A to 1.8 X 10(2) (mean cfu/g) in group D patients. Mean aerobic counts in group A decreased from 3.7 X 10(6) to 64 (mean cfu/g) in group D.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of commonly used bowel preparations on the large bowel mucosal-associated and luminal microflora in the rat model

Studies of colonic microflora have indicated there are two distinct populations, one intraluminal and one mucosal surface-associated. This investigation further characterizes the mucosal surface microflora and assesses the effects of common preoperative bowel preparations on both microflora. Quantitative and qualitative bacterial cultures and scanning electron microscopy were used to study the microflora in five groups of seven rats each: control; intraoperative colonic instillation of ten percent povidone-iodine for 20 minutes; mechanical preparation with magnesium citrate; mechanical preparation followed by intramuscular cefoxitin (30 milligrams per kilogram) one hour preoperatively; and mechanical preparation followed by oral neomycin sulfate and erythromycin base (15 milligrams/kilogram each) given by gavage tube 18, 14, and 4 hours preoperatively. Microflora on the mucosal surface was visualized by scanning electron microscopy in all groups except the neomycin/erythromycin group. Results showed fewer bacterial isolates recovered from the mucosal surface compared with the lumen, as well as several log10 units lower for each bacterial classification. The greatest suppression of both microflora was seen in the neomycin/erythromycin group. Total aerobic and anaerobic luminal counts decreased by 3.7 (P less than 0.009) and 6.3 (P less than 0.009) log10 units, while total aerobic and anaerobic wall counts decreased by 2.3 (P less than 0.009) and 2.8 (not significantly) log10 units, respectively. Lesser reductions were noted in the povidone-iodine group (P less than 0.009, P less than 0.009, P less than 0.009, and P less than 0.048, respectively). There were no statistically significant reductions in either total aerobic or anaerobic counts in the mechanical preparation or cefoxitin groups. These results indicate that neomycin/erythromycin is the most effective regimen in reducing both microflora.

The treatment of intraabdominal infections in surgery

Intraabdominal sepsis is frequently seen following penetrating or blunt abdominal trauma as well as with perforated appendicitis or diverticulitis. The initial leakage of endogenous gastrointestinal microflora into the peritoneal cavity results in peritonitis and secondary septicemia, which often results in a localized intraabdominal abscess. These infections are commonly polymicrobial and correlate directly with the unique endogenous microflora at various levels of the gastrointestinal tract. The successful treatment of intraabdominal sepsis is primarily associated with prompt, appropriate surgical intervention. Parenterally administered antibiotics are also required to decrease the incidence of local bacterial infection or septicemia. The choice of the appropriate agent(s) to be used initially, before obtaining the results of culture and sensitivity tests, depends primarily on both the clinical presentation and on whether the intraabdominal infection occurred in the community or as a result of hospitalization. Clinical and experimental studies of intraabdominal sepsis have primarily emphasized the use of antibiotic agents that have a spectrum of activity effective against aerobic coliforms and the anaerobe Bacteroides fragilis.

Nonperforative appendicitis: a continuing surgical dilemma

Acute appendicitis continues as a medical challenge with newer approaches failing to improve diagnostic accuracy. The role of antibiotics in acute nonperforative appendicitis (NPA) remains unclear. In 175 patients studied at two hospitals, preoperative guidelines were used to exclude perforative appendicitis. Nevertheless, 14% of patients were found to have this condition. Surgeon's reports significantly underestimated the diagnosis when compared with the pathologists' reports. Antibiotic prophylaxis in 122 patients with NPA was studied prospectively comparing ceftizoxime (CTZ), cefamandole (CFM), and placebo (PLA). Ceftizoxime decreased the infection rate compared with PLA (0 vs. 8; P less than .01). Use of antibiotics (CTZ or CFM) resulted in decreased infections when compared with PLA (3 vs. 8; P less than .01) and fewer days of hospitalization (3.8 vs. 5.4 d, P less than .005). Analysis of infection risk factors showed no correlations except for failure to administer antibiotics and the finding of a gangrenous appendix. Operative culture results had no predictive value for either infection or pathogen identification. It is recommended that all patients undergoing surgery for NPA be given 1 d of antibiotic prophylaxis.

Antibiotic prophylaxis in surgery

Scientific studies conducted during the last 10 years have resulted in a great improvement of our approach to the appropriate use of prophylactic antibiotics in the surgical patient. Errors of the past including faulty timing of the initial dosage as well as prolonged duration of prophylaxis have largely been remedied. Present studies are designed to define the patients within the various subsets of diseases or surgical procedures who are at greatest risk of infection. It is these patients who can be expected to benefit most from the efficacious use of prophylactic antibiotics as well as other preventative measures.

Initial antibiotic therapy for alligator bites: characterization of the oral flora of Alligator mississippiensis

An open thumb fracture resulting from an alligator bite became infected with Aeromonas hydrophila, Enterobacter agglomerans, and Citrobacter diversus. The patient was treated by surgical debridement and antibiotic therapy. We obtained cultures from the mouth of ten alligators to characterize their oral flora. Initial empiric therapy after alligator bites should be directed at gram-negative species, in particular, Aeromonas hydrophila and anaerobic species including Clostridium. Of the numerous fungi that were isolated, none has been reported to result in wound infection after alligator bites.

Single-dose cefotetan versus multiple-dose cefoxitin as prophylaxis in colorectal surgery

The safety and effectiveness of a single 2 g preoperative dose of cefotetan to reduce postoperative infectious complications after colorectal surgery was compared with multiple 2 g perioperative doses of cefoxitin in 289 patients enrolled in a multicenter trial; of the 239 evaluable patients, 164 received cefotetan and 75, cefoxitin. No statistically significant difference was detected in the successful clinical response rates for cefotetan and cefoxitin (88 percent and 92 percent, respectively). The difference in median increase in oral body temperature before and after the study (2.5 degrees F for cefotetan and 2 degrees F for cefoxitin) was statistically but not clinically significant (p = 0.03). Although nearly four times as many cefotetan patients as cefoxitin patients had surgery lasting 4 hours or more, the satisfactory bacteriologic response rates for cefotetan and cefoxitin were similar (88 percent and 93 percent, respectively). Nonobese patients and patients whose surgical procedures lasted less than 4 hours treated with either drug had significantly higher success rates (p less than 0.01). The incidence of major wound infection was approximately 8 percent for both treatment groups. Mean concentrations of cefotetan in plasma, specimens of colon, and subcutaneous fat were 128 +/- 61.8 micrograms/ml, 57.2 +/- 40.4 micrograms/g, and 26.8 +/- 19.4 micrograms/g, respectively. The incidence of adverse reactions was 12 percent for each group, and no reaction was considered treatment-related, including changes in results of clinical laboratory tests. A single 2 g preoperative dose of cefotetan was as safe and effective as multiple doses of cefoxitin in the reduction of postoperative wound infections after colorectal surgery.

Multicenter open trial of cefotetan and cefoxitin in elective biliary surgery

The present study was performed in two phases. In phase I, 112 patients were randomized to either 2 g cefotetan as a single prophylactic dose or 2 g cefoxitin every 6 hours for a maximum of 4 doses; phase II included 148 patients who were randomized to either 1 g cefotetan as a single dose or cefoxitin dosed as in phase I. The randomization was 2:1 cefotetan to cefoxitin in both phases. Nonevaluability rates were 10 percent for the cefotetan patients and 22 percent for the cefoxitin patients, the majority being due to dosing errors. Demographic characteristics demonstrated 88 percent to be female, 81 percent to be less than 65 years of age, and the average weight to be 165 lb. There were no differences in these characteristics among the groups. Common duct exploration was performed in 6 percent of the 2 g cefotetan patients, 9 percent in the 1 g cefotetan patients, and 13 percent in the 2 g cefoxitin patients. There were five clinical failures of prophylaxis: one wound infection in the 2 g cefotetan patients, one wound infection and one drain tract infection in the 1 g cefotetan patients, and one wound infection and one case of cholangitis in the 2 g cefoxitin patients. The clinical success rates were 98 percent in the 2 g cefotetan patients, 98 percent in the 1 g cefotetan patients, and 97 percent in the 2 g cefoxitin patients.

Coagulopathy associated with extended-spectrum cephalosporins in patients with serious infections

Patients enrolled in two double-blind multicenter studies were evaluated for the development of hypoprothrombinemia during treatment with cephalosporins. Patients with pneumonia or peritonitis received ceftizoxime, cefotaxime, or moxalactam. The incidence of hypoprothrombinemia was greater in patients with peritonitis (12 of 49) than in those with pneumonia (5 of 96; P less than 0.05). Overall, moxalactam was associated with a higher incidence of hypoprothrombinemia (13 of 52) than either ceftizoxime (1 of 43; P less than 0.05) or cefotaxime (3 of 50; P less than 0.05), and moxalactam patients incurred the highest average increase in prothrombin time (3.7 s) as compared with either ceftizoxime (0.5 s; P less than 0.05) or cefotaxime (0.9 s; P less than 0.05) patients. The occurrence of hypoprothrombinemia in moxalactam patients with peritonitis was not related to dosage, duration of therapy, age, sex, race, or renal or hepatic function. The degree of ileus was, however, strongly related to the development of coagulopathy in moxalactam-treated patients only.