Evaluation of phenotypic characteristics for differentiation of enterococcal species using an example based algorithm.

A computer based rule-generation system of Inductive Learning by Logic Minimization (ILLM) was used to determine the sufficient set of biochemical reactions and necessary conditions that have to be fulfilled for correct differentiation of enterococci recovered from humans. The simplest combination of physiological tests for differentiation Enterococcus faecalis from all other enterococcal species consisted of only 3 reactions. Reactions that tested the ability of acidification D-xylose, mannitol, L-arabinose and Na-pyruvate were useful for delineation of both E. faecalis and E. faecium from all other enterococci. For differentiation of all 12 currently known clinically significant species of enterococci any one of 3 sets of nine tests suggested by ILLM could be used. The tests suggested by ILLM were applied to 153 isolates of enteroccoci recovered at our Department of Microbiology and all E. faecalis (138, 90.2%), E. faecium (13, 8.5%) and E. avium strains (2, 1.3%) were correctly differentiated.

Improvements for multipurpose bacteriological identification tables to suit the diagnosis of Vibrio cholerae.

The aim of the study was to reduce to key tests the 4 extensive polyvalent diagnostic biochemical tables most widely used in Croatia and to adapt them for the demonstration of Vibrio cholerae and its differentiation from the 3 Vibrios (V. alvinolyticus, V. mentschikovii, V. fluvialis) important in differential diagnosis. The fourth table has now been adapted to differentiate among all 12 Vibrio species known to be human pathogens (V. mimicus, V. cincinatiensis, V. holisae, V. damsela, V. furnisi, V. parahaemolyticus, V. vulnificus, V. carchariae). Using the inductive Learning by Logic Minimization Method (ILLM), we analyzed 2 tables (i.e. identification matrices) that were a part of bioMérieux's commercial packaged polyvalent identification systems widely used in Croatia (API 20E and ATB 32E), as well as 2 compilation tables by M. T. Kelly et al. The tables contained 27, 32, 59 and 8 tests, respectively. Cutting these solely to the key tests involved rationalizing them from 59 to the 5 necessary to differentiate Vibrio cholerae from 3 related Vibrios. Further rationalizations were from 32 to 2 and from 27 to the 3 necessary to differentiate Vibrio cholerae from 2 related Vibrios. By reducing the table of 8 tests to 7, and adding 4 new ones to these we achieved an optimization permitting mutual differentiation of all 12 known human Vibrio pathogens. Use of the selective TCBS plating medium was the only precondition for making these tables effective.

[Selection of phenotype characteristics in differentiation of various species of enterococci using an inductive mathematical program]. / Odabir fenotipskih obiljezja u razlikovanju vrasta enterokoka induktivnim matematickim programom.

In this paper a novel computer example-based learning system (Inductive learning by logic minimization) was used to determine the sufficient set of biochemical reactions and necessary conditions that have to be fulfilled for the correct identification of enterococci isolated from human specimens. Several combinations for accurate identification of Enterococcus faecalis and Enterococcus feacium from other enterococci were found. The simplest combination set for E. faecalis identification consists of 3 reactions: growth in 0.04% K-tellurite, mannitol acidification, failure to acidify raffinose. The simplest set for E. faecium differentiation from other enterococcal species is performed by the following 3 reactions: failure to acidify D-xylose and Na-pyruvate, and acidification of L-arabinose. Only 4 tests are sufficient (acid from D-xylose, mannitol, L-arabinose and Na-pyruvate) for the correct identification of these two, the most frequently isolated species. If it is necessary to analyze all enterococcal species, then even three combinations of 9 tests for the correct differentiation of any of them, are available.

Antibiotic resistance among gram-negative nosocomial pathogens in the intensive care unit: results of 6-year body-site monitoring.

Results of 6-year body-site monitoring in an intensive care unit (ICU) are presented and antimicrobial resistance of gram-negative isolates analyzed. The study included 622 patients. Six hundred thirty-five bacterial isolates-causes of nosocomial sepsis, pneumonia, and urinary tract infections (UTIs)-were tested during the study. Gram-negative bacteria were the predominant isolates, causing 65% of cases of sepsis, 78.7% of pneumonias, and 70.2% of UTIs. Gram-negative isolates (454) were highly resistant to antimicrobials commonly used in the ICU, with the exception of imipenem. Resistance was 1.1% among pathogens responsible for UTIs, 6.7% among those causing sepsis, and 13.6% among those responsible for pneumonia. Klebsiella pneumoniae associated with pneumonia and sepsis was significantly less resistant to ciprofloxacin than were isolates from urine (22.8% and 13.9%, respectively, vs 44.4%). Pseudomonas aeruginosa strains responsible for pneumonia were less resistant to ceftazidime than were isolates causing sepsis and UTI (35.7% vs 51.3% and 51.5%, respectively). Acinetobacter calcoaceticus strains associated with UTI were significantly more resistant to netilmicin than were strains responsible for sepsis and pneumonia (83.3% vs 40.3% and 42.6%, respectively). The study confirmed that in addition to focused microbiologic surveillance, multiple-body-site monitoring can provide unique information about the sensitivity of the pathogens involved. The results suggest that antimicrobial resistance among nosocomial pathogens depends on the site of infection or the type of microbiologic specimen.

Comparison of clinical characteristics of group A streptococcal bacteremia in children and adults.

This report reviews 55 cases of bacteremia due to group A streptococci (GAS) in patients treated at the University Hospital of Infectious Diseases, in Zagreb, Croatia, during the period 1974-1994. Clinical findings for 27 children (age, < 18 years) were compared with those for 28 adults. A clear predominance of the respiratory tract as a primary focus of infection in younger patients was observed (P = .00006). Children were more frequently colonized by GAS in their throats than were adults (P = .04). Suppurative osteoarticular metastatic foci were more often found in children (P = .02). Acute underlying conditions were more common in children (P = .04), whereas chronic underlying conditions were more common in adults (P = .00005). The case fatality rate was 23% among children (6 of 27) and 50% among patients aged > 60 years (5 of 10). The course of bacteremia due to GAS was benign in eight children (29.6%) and 12 adults (42.8%). Our experience suggests that there are significant differences in the presentation of bacteremia due to GAS in children and adults.

[Bacteremia and sepsis in patients hospitalized at the Dr. Fran Mihaljevíc Clinic for Infectious Diseases in Zagreb 1987-1991]. / Bakteriemija i sepsa u bolesnika hospitaliziranih u Klinici za infektivne bolesti "Dr. Fran Mihaljevic" u Zagrebu od 1987. do 1991. godine.

A total number of 836 episodes of bacteremia and fungemia were examined in 823 hospitalized patients in the University Hospital of Infectious Diseases "Dr Fran Mihaljevic" Zagreb from the beginning of 1987 to the end of 1991. Twenty-five percent of them were nosocomial bacteremias and 5% were polymicrobial bacteremias. The most frequently isolated causative agents were Salmonella spp. (26%), Escherichia coli (17%), Streptococcus pneumoniae (11%) and Staphylococcus aureus (8%). There were 34% of gram-positive bacteremias. The increased frequency of nosocomial bacteremias caused by coagulase-negative staphylococci was recorded. The frequency of coagulase-negative staphylococci strains resistant to gentamicin and Klebsiella spp. strains resistant to cefotaxime was increased. Shock was present in 19% of episodes. Relation between septic shock occurrence and causative agent of bacteremia was not proved. Mortality in patients with bacteremia was 13%, and total mortality was 20%. The outcome of the disease was in direct relation with causative agent of bacteremia. The initial empiric antimicrobial therapy was prolonged in 91% of episodes of bacteremia after blood culture results were known.

[Evaluation of phenotype characteristics of streptococci in the identification of the Streptococcus anginosus (Streptococcus milleri) group]. / Procjena nekih fenotipskih obiljezja streptokoka u identifikaciji Streptococcus anginosus (Streptococcus milleri) grupe.

Microorganisms referred to as Streptococcus anginosus (Streptococcus milleri) group which consist of S. anginosus, S. intermedius and S. constellatus is very difficult to identify to the species level, because of their diversity of biochemical, hemolytic and serological characteristics and because of confusion surrounding their taxonomy. Identification procedures on three isolates from primary sterile sites of three different patients, using API 20A system are described. Streptococcus intermedius was established in two and Streptococcus anginosus in one case. The importance of these organisms as human pathogens should enhance efforts of clinical microbiologist towards their accurate identification.

[Hospital infections and resistance to new antibiotics in intensive care units: relation to diagnostic and therapeutic procedures]. / Bolnicke infekcije i rezistencija na neke novije antibiotike u jedinici intenzivne skrbi: ovisnost o dijagnosticko-terapijskim zahvatima.

The results of hospital infection surveillance over an eight-month period in the Intensive Care Unit (ICU) of the University Hospital of Infectious Diseases "Dr Fran Mihaljevic", Zagreb, are presented together with the results of the antibiotic resistance of isolated gram-negative bacteria in relation to the clinical material taken for culture. Of 110 strains of gram-negative bacteria isolated, 103 (93.6%) were resistant to ampicillin, 80 (72%) to gentamicin, 74 (67%) to cefotaxime, 50 (45.5%) to pefloxacin. Imipenem, ciprofloxacin, ceftazidime and amikacin were the most active representatives of their respective groups with 5, 25, 49 and 50% of resistant strains. Strains isolated in urinary tract infections were significantly less resistant to amikacin and ceftazidime (p < 0.05) than strains isolated from other sources. Our findings stress the need for close surveillance of antibiotic resistance in these selected groups of patients, and are particularly relevant for planning empirical anmtibiotic therapy of hospital infection in the ICU.