Carriage of Staphylococcus aureus and of gram-negative bacilli resistant to third-generation cephalosporins in cirrhotic patients: a prospective assessment of hospital-acquired infections.

OBJECTIVE: To study the relation between Staphylococcus aureus nasal and stool colonization, stool carriage of gram-negative bacilli resistant to third-generation cephalosporins (CephR), and subsequent infections during hospitalization. DESIGN: Prospective study. PATIENTS: 551 cirrhotic patients with 589 consecutive hospital stays. All patients were screened within 48 hours of admission; 589 nasal swabs, 417 stool specimens, and 589 urine samples were analyzed. RESULTS: Carriage rates were 18.8% for methicillin-sensitive S aureus (MSSA), 16.3% for methicillin-resistant S aureus (MRSA), and 13.7% for CephR. We observed 87 episodes of spontaneous bacterial peritonitis, 63 cases of bacteremia, and 167 urinary tract infections occurred. Only 1 case of bacteremia and 4 urinary tract infections due to CephR occurred in patients carrying the same organism in their stools. The risk of MRSA ascitic fluid infections, bacteremia, and urinary tract infections was 3.1% versus 1% (not significant), 8.3% versus 0.8% (P<.001), and 11.4% versus 0.6% (P<.001) in carriers and noncarriers, respectively. Pulsed-field gel electrophoresis (PFGE) of isolates from 16 patients infected by MSSA (3 cases) and MRSA (13 cases) demonstrated that the colonizing strains matched the invasive strains in the 3 MSSA cases and in 8 of 13 MRSA cases. CONCLUSION: Carriage of CephR strains is not associated with subsequent infection by these organisms in hospitalized cirrhotic patients. In contrast, MRSA carriage was an important risk factor for MRSA bacteremia and urinary tract infection.

Rapid diagnosis of gram negative urinary infections: identification and antimicrobial susceptibility testing in 24 hours.

A rapid method for diagnosing urinary tract infections, using identification and antimicrobial susceptibility testing that can be carried out in 24 hours, was devised. The method relies on direct inoculation of diluted urine (1/500) in the API 20 E and API ATB systems. Urine was simultaneously cultured on Columbia blood agar and on Drigalski agar to control the purity and for purposes of comparison. The results of this method and those obtained with a conventional method were compared by analysing 1352 urines. The results showed that all of the organisms were correctly identified using the conventional method, and susceptibility testing (rapid method) gave results that agreed with those of the classical method in 94% of cases, with major discrepancies in only 0.08% of cases. The rapid method applies only to monomicrobial infections.

Changes in nature and antibiotic resistance of bacteria causing peritonitis in cirrhotic patients over a 20 year period.

AIM: To assess all clinically and bacteriologically documented episodes of spontaneous bacterial peritonitis diagnosed in a single unit over a 20 year period, to identify changes in the nature and antibiotic resistance of the causative bacteria. SETTING: A specialist liver disease unit in a tertiary care centre. MATERIAL: Cultured ascitic fluid obtained in the course of 240 consecutive episodes of clinically and bacteriologically proven spontaneous bacterial peritonitis. Patient recruitment remained stable during the 20 year period in terms of the number of cirrhotic patients admitted and the severity of their condition. RESULTS: 78.7% of isolates were Enterobacteriaceae (Escherichia coli in 51%) and 19% were Gram positive cocci. Until 1979 all the Enterobacteriaceae had the wild phenotype, compared with only 50% at the end of the study period. Since 1993, 22% of Enterobacteriaceae have been resistant to third generation cephalosporins. Methicillin resistant staphylococci were only isolated after 1989. CONCLUSIONS: Changes in the epidemiology and antibiotic resistance of bacteria causing spontaneous bacterial peritonitis must be monitored for optimal treatment.

Multilocus enzyme typing of human and animal strains of Clostridium perfringens.

Multilocus enzyme electrophoresis was developed to evaluate the genetic diversity of 71 human strains and 17 animal strains of Clostridium perfringens. Crude protein extracts, obtained by sonication of washed bacteria, were analyzed by polyacrylamide-agarose gel electrophoresis to characterize electrophoretic mobility variants of seven enzymes (esterase, glutamate dehydrogenase, glutamic-oxaloacetic transaminase, nucleoside phosphorylase, phosphoglucose isomerase, phosphoglucomutase, threonine dehydrogenase). Genetic diversity of the enzyme loci ranged from 0.340 to 0.813. Sixty-nine electrophoretic types were described among the 88 strains tested and the index of discrimination was 0.994. All strains were typable, and epidemiological relationships between isolates could be established. This method showed a fair correlation with esterase electrophoretic typing based on hydrolytic and electrophoretic polymorphism of esterases. This work demonstrates that multilocus enzyme polymorphism is a reliable and discriminant marker of genetic diversity of strains of C. perfringens.

Enzyme electrophoresis combined with serogrouping for improved differentiation of Clostridium difficile strains.

We used enzyme electrophoresis to study a set of epidemiologically related and unrelated isolates of Clostridium difficile. The 53 strains belonged to the most frequent serogroups (A1, C, G, H and K). Nine electrophoretic profiles were defined on the basis of five enzymes, and two were characteristic of a single strain. Each serogroup was resolved into two or three different enzyme patterns. By combining the two methods we were able to resolve the strains into 12 types. There was an excellent correlation between enzyme electrophoresis and serogrouping data. This method may be of use in investigating nosocomial transmission.

Beta 2-microglobulin in liver cirrhosis: study of a local synthesis in ascitic fluid.

Beta 2-microglobulin determinations in ascitic fluid (A) and serum (S) collected on the same day, were performed in 24 patients suffering from alcoholic liver cirrhosis. Ascitic beta 2-m concentration varied from 0.4 to 4.6 mg/l for patients with a normal renal function. Much higher values were found in patients with chronic renal failure. No correlation could be established between ascitic beta 2-m level and the clinical evolution of the cirrhosis. Comparative measurements of beta 2-m S/A ratio and albumin, transferrin, total protein S/A ratios suggests a local synthesis of beta 2-m in ascitic fluid. This is confirmed by an immuno-cytochemical technique which reveals the localisation of beta 2-m in the cytoplasm of peritoneal cells. The presence of beta 2-m in ascitic fluid seems to be related to an ultrafiltration across the peritoneal membrane as well as a local polyclonal activation of the immune system.

[Automated method for determining calcium in biological liquids]. / Méthode de dosage automatique du calcium dans les liquides biologiques.

A method of determination of calcium in biological fluids is proposed. It is a continuous flow technic without deproteinisation nor dialysis, using orthocresol phtaleine in alkaline medium. The interference due to magnesium is eliminated by the presence of hydroxy-8-quinoleine. The addition of dimethyl sulfoxide improves the solubility of the reagents and ensures better stability of the media. The correlation between the results obtained by this technic and by atomic absorption spectrophotometry was studied on 160 human sera and 40 urines. The influence of various parameters such as hemolysis, bilirubin, magnesium and phosphates is low or negligeable. The results concerning opalescent, cloudy or lactescent sera may be erroneous by excess. The physiological reference values for serum calcium are drawn up from a Paris student population of both sexes.

[Comparison of three methods of measuring antibiotic sensitivities (author's transl)]. / Comparaison de trois méthodes d' antibiogramme.

Two semi-automatic methods of measuring antibiotic sensitivities were compared to the disk method for everyday use in a bacteriology laboratory. The reproducibility, compared with 3 strains, proved satisfactory, the highest was the API method. There appeared to be few discrepancies between the semi-automatic methods and the disk method. Part of the latter may be explained by the difference of critical concentrations. Others, routine for a few antibiotics, merit more complete study.