Bacteriologic flora of aspiration-induced pulmonary infections.

The role of anaerobic and aerobic microorganisms in the genesis of pneumonia or lung abscess in patients with historical, clinical, and radiologic findings suggestive of aspiration was compared to their role in similar patients without these findings. Bacterial specimens were obtained by transtracheal aspiration or thoracentesis. Anaerobes were isolated in 100% of the patients who were aspiration-prone as contrasted with only 20% of those who were not. Isolation of a single species or no growth was more common in the nonaspiration group, whereas multiple isolates were more common in the aspiration group. Patients with lung abscesses were treated with penicillin and all of them responded clinically, despite occasional recovery from the culture specimen of penicillin-resistant organisms. This suggests that lung abscess may be the result of a synergistic bacterial infection.

Parenteral prophylaxis against enterococcal endocarditis.

Three commonly used antibiotic regimens for the prevention of enterococcal endocarditis were administered parenterally to six healthy men in a crossover manner. The regimens included 1 gm of streptomycin intramuscularly (IM) in combination with (1) procaine penicillin 600,000 units plus aqueous penicillin G 200,000 units IM; or (2) ampicillin 25 mg/kg intravenously (IV); or (3) ampicillin 1 gm IM. The combinations containing ampicillin IM or IV with streptomycin produced bactericidal activity at dilutions of 1:2 or greater for the majority of the strains, whereas the penicillin-streptomycin regimen did not. All regimens were poorly bactericidal against three strains of enterococci which were highly resistant to streptomycin. These data suggest that ampicillin plus streptomycin is the preferred regimen for prophylaxis.

Bacteremia in suckling rabbits after oral challenge with Vibrio parahaemolyticus.

Vibrio parahaemolyticus, a halophilic marine enteropathogen, produces diarrhea in man after ingestion of contaminated seafood. Only strains capable of producing beta-hemolysis (Kanagawa-positive strains) are enteropathogenic. Yet the majority of marine isolants are nonhemolytic and Kanagawa negative. Studies were initiated in suckling rabbits in an attempt to elucidate pathogenetic mechanisms. Fasting animals were infected orally with Kanagawa-positive and Kanagawa-negative strains of V. parahaemolyticus, V. cholerae, two enteropathogenic strains of Escherichia coli, Shigella flexneri, and strains of salmonellae. Seven hours postchallenge, cardiac blood, liver, and spleen cultures were obtained. V. parahaemolyticus strains failed to induce intestinal fluid accumulation during this study period. Bacteremia occurred in animals challenged with Kanagawa-positive V. parahaemolyticus, S. flexneri, and salmonella strains only. Animal passage increased the ability of V. parahaemolyticus to cause bacteremia. Liver and spleen cultures were positive in approximately 50% of animals challenged with the Kanagawa-positive strains of V. parphaemolyticus. The ability of this organism to penetrate the intestinal epithelium of suckling rabbits may represent a specific property that plays a role in pathogenesis.

Hemolytic reaction of clinical and environmental strains of Vibrio vulnificus.

All Vibrio vulnificus strains tested (four clinical isolates and eight environmental isolates) hemolyzed human erythrocytes. In contrast to findings with Vibrio parahaemolyticus, in which hemolytic activity correlates with isolation from clinical specimens, results from the present study suggest that hemolysis is not usefull in differentiating V. vulnificus strains.

False-positive rabbit ileal loop reactions attributed to Vibrio parahaemolyticus broth filtrates.

Vibrio parahaemolyticus broth filtrates have previously been shown to produce positive reactions in rabbit ileal loops only if concentrated 10-fold by lyophilization. This method of concentration produces solutions that contain greater than 20% NaCl. In the present study, however, concentrations of NaCl of greater than or equal to 4% induced positive responses in ileal loops, and desalting rendered previously reactive, concentrated broth filtrates negative. Therefore, enterotoxin was not demonstrated in our broth filtrates of V. parahaemolyticus, a finding which suggests that previous studies require further evaluation. Since most culture media contain 0.5% NaCl, it is important to determine and to control the NaCl content and the osmolality of all lyophilized concentrates tested in the ligated rabbit ileum.

A double-blind study of trimethoprim-sulfamethoxazole prophylaxis in patients having transrectal needle biopsy of the prostate.

We studied 89 men undergoing transrectal prostatic biopsies to determine the efficacy of trimethoprim-sulfamethoxazole in preventing postoperative fever, bacteremia and bacteriuria. Of the patients who received placebo temperatures of 37.6C or more occurred in 18%, bacteremia in 70% and bacteriuria in 21%. Most cases of bacteremia were caused by anaerobic organisms and were asymptomatic. Trimethoprim-sulfamethoxazole did not reduce the frequency of fever or bacteremia but did produce a significant reduction in bacteriuria (0 versus 21%, p equals 0.008).

Comparative activities of piperacillin, ceftazidime, and amikacin, alone and in all possible combinations, against experimental Pseudomonas aeruginosa infections in neutropenic rats.

This study compared the efficacy of therapy with the double beta-lactam combination of ceftazidime plus piperacillin with that of single-agent therapy with ceftazidime, piperacillin, or amikacin alone and with that of two aminoglycoside-beta-lactam combinations against Pseudomonas aeruginosa peritonitis and bacteremia in neutropenic rats. Rats made severely granulocytopenic with cyclophosphamide became bacteremic secondary to peritonitis which was induced by intraperitoneal challenge with P. aeruginosa. Antibiotic therapy with single agents (amikacin, 20 mg/kg of body weight, intramuscularly; ceftazidime, 20 mg/kg of body weight, subcutaneously; piperacillin, 200 mg/kg of body weight, intramuscularly) or with the various combinations of agents was begun 2 h after bacterial challenge and was continued every 6 to 8 h for 62 h. Therapeutic efficacy was judged on the basis of survival 72 h after bacterial challenge, rate of mortality, incidence of bacteremia, and the emergence of resistant organisms. Based on these criteria, therapy with the double beta-lactam combination had no advantage over single-agent therapy and was in all cases clearly inferior to beta-lactam-aminoglycoside combinations.

Gastrointestinal tuberculosis mimicking cancer--a reminder.

Tuberculous involvement of the gastrointestinal tract may be suspected in the presence of active pulmonary tuberculosis. This case demonstrates that tuberculous enteritis may develop in the absence of obvious pulmonary involvement. The diagnosis in such instances is established by a combination of roentgenographic studies and surgical exploration.

Septic and crystalline joint disease. A simultaneous occurrence.

Bacteria and crystals were simultaneously recovered from the synovial fluid of two patients with acutely inflamed joints. The bacteria were initially identified on Gram stain and subsequently grown on supplemented peptone broth, and the crystals were readily identified by polarizing microscopy. Although cause-and-effect relationship between these two types of arthritis cannot be established, the need for thorough examination of synovial fluid is evident.

Serum antibiotic concentrations pre- and postcardiopulmonary bypass.

Serum concentrations of cephalothin or kanamycin, or both, were determined in 53 patients undergoing cardiopulmonary bypass. Conventional doses of these antibiotics did not provide serum levels above the accepted minimum inhibitory concentrations in children. Adults had adequate serum antibiotic concentrations only when the antimicrobials were administered within 4 h of beginning cardiopulmonary bypass. The impact of these variations upon the occurrence of infectious endocarditis could not be appraised since no cases of infective endocarditis were seen during a 4-month postoperative period.

Model of intraabdominal abscess in mice.

Intraperitoneal inoculation of sterile mouse feces into mice produced intraabdominal abscesses. The addition of Bacteroides fragilis increased the incidence and the number of abscesses.

Resistance of Vibrio vulnificus to serum bactericidal and opsonizing factors: relation to virulence in suckling mice and humans.

Vibrio vulnificus causes soft-tissue infections, gastrointestinal disease, and severe sepsis in humans. Bacterial and host factors in virulence have remained poorly defined. We found that blood culture isolates of V. vulnificus were completely resistant to the bactericidal effects of 10% normal human serum, in contrast to soft-tissue and environmental isolates that showed a mean 2.6 log10 decline during 120 min of incubation. Following opsonization by 10% normal human serum, mean uptake of blood isolates by normal human polymorphonuclear leukocytes during 20 min of incubation in vitro was 45.8% compared with 83.2% for isolates from other sites. Blood isolates were lethal for suckling mice (mean LD50, 1.3 X 10(6)) in contrast with isolates from other sites, which were less virulent (mean LD50, 1 X 10(9)); lethality correlated well with bacteremia at 6 hr. These studies show a close correlation between bacterial virulence for humans and suckling mice and suggest that resistance to the bactericidal and opsonizing effects of normal human serum may be important factors governing that virulence.

BL-P1654, ticarcillin, and carbenicillin: in vitro comparison alone and in combination with gentamicin against Pseudomonas aeruginosa.

Minimum inhibitory concentrations of carbenicillin, ticarcillin, and BL-P1654 were determined for 89 clinical isolates of Pseudomonas aeruginosa. Ticarcillin was generally twice as active and BL-P1654 eight to 16 times as active as carbenicillin. Usually carbenicillin and ticarcillin killed at the same concentration or twice the concentration needed to inhibit, whereas 400 mug of BL-P1654 per ml was not bactericidal for the majority of isolates tested. The inhibitory effect of all three drugs varied markedly with the size of bacterial inoculum. When therapeutically achievable concentrations were used, adding gentamicin enhanced the inhibitory and bactericidal activity of all three penicillin derivatives for the majority of isolates. However, inhibition of isolates highly resistant to gentamicin was not improved by combining the semisynthetic penicillins with gentamicin.

Anaerobic bacteriuria in a male urologic outpatient population.

We screened 517 urine samples from male outpatients, many of whom had underlying urinary tract pathology, for anaerobic and aerobic bacteriuria. Of the 153 specimens containing greater than 10(5) bacteria per ml. 20% yielded anaerobes only and an additional 6% revealed mixed anaerobic and aerobic growth. Pyuria was found more frequently in samples containing anaerobic bacteriuria than in those containing no growth but not as frequently as when aerobic bacteria were present. The high counts of anaerobic bacteria in first-voided specimens compared to midstream and post-prostatic massage aliquots suggested a urethral source for most bacteria. However, suprapubic aspiration of bladder urine demonstrated the organism in 2 of 10 patients with high numbers of anaerobes and pyuria in voided samples.

Imipenem therapy of Pseudomonas aeruginosa bacteraemia in neutropenic rats.

Rats were made neutropenic by intraperitoneal (ip) injection of cyclophosphamide. Those neutropenic (mean white blood cell count of 470/mm3) rats were challenged intraperitoneally with Pseudomonas aeruginosa to assess the efficacy of single agent therapy with either imipenem, latamoxef (moxalactam) or amikacin, or combination therapy with imipenem-amikacin or latamoxef (moxalactam)--amikacin. Pharmacokinetic studies were performed in rats to assure that therapy was equivalent during therapeutic trials. Three levels of bacterial challenge (4 LD50, 13 LD50 and 250 LD50) were examined. At all challenge levels, single agent therapy with latamoxef (moxalactam) failed to significantly protect rats from fatal bacteraemia. Single-agent therapy with amikacin did significantly protect rats from fatal bacteraemia at the lower challenge levels, but not at the 250 LD50 challenge. Single agent therapy with imipenem significantly protected rats at all challenge. Single agent therapy with imipenem significantly protected rats at all challenge levels. In-vitro studies established a synergistic effect when combination antibiotics were used. This correlated with in-vivo findings that combination therapy resulted in improved rat survival and recovery of fewer Ps. aeruginosa isolates. The latamoxef (moxalactam)-amikacin combination was more effective than either agent alone, but was not more effective than imipenem alone. The imipenem-amikacin combination was the most effective therapeutic regimen tested. These results suggest that imipenem alone, and particularly when combined with an aminoglycoside, is effective in treating serious Ps. aeruginosa infections in neutropenic rats. Clinical studies in infected immunocompromised patients may be warranted.

Pirbenicillin: comparison with carbenicillin and BL-P1654, alone and with gentamicin, against Pseudomonas aeruginosa.

Minimum inhibitory concentrations (MIC) of pirbenicillin against 135 clinical isolates of Pseudomonas aeruginosa were one-fourth of those required for carbenicillin but two times higher than those for BL-P1654. Increasing the inoculum size produced an adverse effect on the bactericidal activity for all three antibiotics. This was more apparent for pirbenicillin than for carbenicillin, but less than the effect on BL-P1654. When concentrations of antibiotics likely to be achieved clinically were used, gentamicin increased the inhibitory and bactericidal effects of all three semisynthetic penicillins for the majority of isolates. Strains highly resistant to the aminoglycoside antibiotic, however, were inhibited no more by the penicillin-gentamicin combinations than by the most effective of the antibiotics alone.