Cultural and Biochemical Characteristics of Clinical Isolates of Aeromonas hydrophila

Aeromonas hydrophila infection has been increasingly found, in particular among patients with various underlying diseases. Many characteristics of this organism are quite similar to those of Enterobacteriaceae and Vibrio, making an accurate identification difficult. In a period of 2 years, the authors obtained a total of 27 isolates of A. hydrophila from clinical materials, and their cultural and biochemical characteristics are herewith reported. Some of the most important clues to suspect this organism were a wide zone of complete hemolysis on blood agar, partially alkaline slant, acid butt, and small amount of gas in trip1e sugar iron agar (TSI), weak indole reaction, and negative ornithine decarboxylase in motility indole ornithine medium (MIO), and usually positive citrate utilization. It is concluded that the identification of this organism should be possible on the basis of deoxyribonuclease (DNase), oxidase, and a few other tests. Our isolates showed a similar antibiotic susceptibility to those reported in other countries; i.e., a11 were resistant to ampicillin and most were susceptible to other antibiotics, excluding cephalothin.

An Evaluation of the Effect of one-day Blind Subculture in the Initial Detection of Salmonella typhi Positive Blood Cultures

During the 8-month period of May to December, 1978, a total of 3,529 blood cultures were taken from Yonsei Medical Center patients and the effect of blind subculture in the initial detection of Salmonella typhi positive culture was analyzed. The blind subculture at the end of 1-day incubation (1-d BS) detected 35.0% of S. typhi positive specimens. All of the S. typhi positive specimens by 1-d BS were a1so macroscopically positive. However, by doing slide agglutination with the growth on subculture plate S. typhi was identifiable tentatively. This saved a day compared to macroscopic examination alone. Therefore the 1-d BS is concluded to be a valuable procedure for the isolation of this organism from blood. For the isolation of S. typhi 7-day incubation was concluded adequete based on the fact that there was only 1 specimen which became positive after over 1-week incubation.

Biochemical Characteristics and Antibiotic Susceptibilities of Serratia marcescens Isolated from Clinical Specimens

A minimal test scheme, consisting of deoxyribonuclease (DNase) and tween 80 hydrolysis (TEH) together with a few other biochemical tests, was used to make tentative identification of Serratia marcescens from clinical specimens. The identifications were reevaluated by testing comprehensive biochemical characteristics of 52 isolates, and all were found to be correct. The biochemical reactions of the isolates were very homogenous, showing typical characteristics of the species except in the urease test and acid production from sucrose, adonitol and inositol. These facts support the feasibility of the use of the minimal identification scheme. Pigment production was noted only in 7 isolates invalidating the value of this characteristic for the identification. Fifty-seven isolates were tested for their antibiotic susceptibility. They were found most frequently susceptible to gentamicin (47.4%), chloramphenicol (35.0%) and kanamycin (28.1%). Many isolates (49.1%) were multiply resistant to ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin and tetracycline.

Penicillin and Tetracycline Susceptibility of Neisseria gonorrhoeae Strains isolated during 1966 to 1975

Although the decreased susceptibility of gonococci to penicillin and tetracycline is a worldwide problem in the treatment of gonorrhea, the gonococci in the West Pacific region are particulary notorious in their resistance. Using a plate dilution method, susceptibility of the gonococci isolated at this institution during 1970 to 1975 was tested to penicillin and tetracycline, which are the most widely used antibiotics for the treatment of gonorrhea. The data of this susceptibility, together with that of the strains isolated during 1966 to 1969 from prostitutes, were analyzed and herewith reported. The range of minimum inhibitory concentration (MIC) of penicillin was 0.01 to 2.0U/ml. Among the 191strains, 87.9% required MIC of 1.0U/ml and over, and 29.3% required 1.0U/ ml and over. The range of MIC of tetracycline was from 0.125 to over 2 microgram/ml. Among the 120 strains, 60% required MIC of 1 microgram/ml and over. This in vitro evidence indicates wide prevalence of less susceptible strains which are difficult to cure with conventional doses of penicillin or with tetracycline. Comparison of the degree and the frequency of less susceptible strains by the year of isolation showed some variation, which may however have been induced by the difference of sources, rather than by the difference of time of isolation.

Effect of Hypertonic Sucrose on the Growth of Salmonella typhi in Experimental Blood Cultures

Slower growth of S. typhi in hypertonic media, reported previously by the authors, was contradictory to other workers', results which showed better growth of some species of bacteria. To evaluate furthur the effect of hypertonic sucrose on the growth of S. typhi, organisms were suspended in saline or in blood with or without sodium polyanethol sulfonate (SPS) and stored up to 24 hours. And then viable counts were determined on tryptic soy agar (TSA) and experimental blood cultures were done in tryptic soy broth (TSB) and in TSB with 10% sucrose (TSB-H). S. typhi, suspended in blood and kept for 24 hours, were inoculated into TSB and TSB-H and after 4 hour incubation viable counts were made on TSA and on TSA with 10% sucrose (TSA-H). In this study it was found that, during the 24 hour storage, the viable counts of S. typhi suspended in saline with or without SPS were similar and those suspended in blood with SPS were incereasing. Comparison of the growth in TSB and in TSB-H did not show hyperonic media was better for the cultivation of S. thphi which was kept up to 24 hours before inoculation. On the contrary the growth was slower. Viable counts made on TSA and on TSA-H from the TSB and TSB-H, which were inoculated with S. typhi suspended in blood and incubated for 4 hours, showed similar results indicating TSB-H did not support faster growth. From the results of this experiment and of the previous clinical blood cultures, it is concluded that 0.1% SPS does not give adverse effect on S. typhi during the 24 hour storage and that hypertonic sucrose does not give better result in the cultivation of S. typhi.

Effects of High Concentrations of Sucrose in Blood Culture Media with Special Reference to the Cultivation of Salmonella typhi

Osmotically stabilized media have been reported to increase the recovery rate of various bacteria from blood. This study was made to determine the effect of high concentrations of sucrose on the cultivation of S. typhi from blood. Sucrose in 15% or 30% concentration in the blood culture media retarded the growth. The mean incubation time for the appearance of growth was significantly longer in the media with sucrose. In those blood specimens which rendered growth of S. typhi in both media with and without sucrose, the incubation times were compared; and it was found that the majority of the specimens showed faster growth in the media without sucrose. Experimental cultures showed that the higher the sucrose concentration the lighter and slower were the growths of S. typhi. These tendencies were also observed in the growth of E. coli, P. aeruginosa, S. aureus, beta-hemolytic Streptococcus, alpha-hemolytic Streptococcus and S. pneumoniae.

Anaerobic Bacteria in Routine Diagnosiic Cultures

Importance of anaerobic bacteria is often neglected in clinical bacteriology due to difficulties of isolation and identification. Anaerobic infection became more important as more patients with defective defence against microbial invasion are treated at hospitals. This is a report of studies of anaerobe isolation from clinical specimens and antibiotic susceptibilities. Clinical cases with anaerobe isolation are also presented to stress importance of anaerobes as etiologic agents. 128 anaerobe strains from 111 patients, were isolated in 1972 and 1973. Among these, 82% were non-sporeforming anaerobes. Isolation of anaerobes was frequent from specimens of pleural, and abdominal fluid, and liver. In some patients, anaerobes were isolated in pure culture. Gram-positive organisms were susceptible to many antibiotics. Bacteroides fragilis was susceptible to chloramphenicol and tetracyline, but resistant to many other antibiotics. Overall antibiotic susceptibility was similar to the results by other workers in other countries.