Enhanced chitinase production by Chitinolyticbacter meiyuanensis SYBC-H1 using staged pH control.

The pH of a microbiological culture is important for both cell growth and chitinase accumulation, but the optimal pH is not normally the same for both. The objective of this study was to investigate the effect of pH on chitinase production by Chitinolyticbacter meiyuanensis strain SYBC-H1 (ATCC BAA-2140) in a mineral medium. The results of batch culture at different pH values showed that the optimum pH for cell growth and chitinase production varied with time, although KOH produced the best results for cell growth and chitinase production, NaOH was chosen because of cost considerations. We designed a three-stage pH control strategy using NaOH as the neutralizing agent. Maximum cell growth (1.07 g dry cell weight/l) and maximum chitinase activity (13.6 U/ml) were observed after culture at 26°C for 72 h in a mineral medium. These values were greater by 129% and 162%, respectively, and the length of time to attain maximum chitinase activity was decreased by 12 h, compared with results from an earlier study (Hao et al., 2011b).

Seasonal and tissue distribution of Laribacter hongkongensis, a novel bacterium associated with gastroenteritis, in retail freshwater fish in Hong Kong.

Laribacter hongkongensis, a recently discovered bacterium associated with community-acquired gastroenteritis, has been found in the intestines of freshwater fish. To better understand the epidemiology and ecology of the bacterium, we carried out a surveillance study to investigate possible seasonal variation in the recovery of L. hongkongensis and its distribution in various organs in retail freshwater fish in Hong Kong. Forty whole freshwater fish of two species (20 grass carps and 20 bighead carps), and intestines from 120 grass carps were sampled during a one-year period. L. hongkongensis was isolated from 11 (55%) of the 20 grass carps and 6 (30%) of the 20 bighead carps; and the intestines of 49 (41%) of 120 grass carps. Seasonal variation in the recovery of L. hongkongensis from both whole fish and intestines was observed, with higher isolation rates in spring and summer than in fall and winter. There was also positive correlation between temperature and the isolation rates. When L. hongkongensis was cultured in vitro at different temperatures, shorter lag time and higher growth rate were observed at higher temperatures, with 37 degrees C being optimal among the tested temperatures. L. hongkongensis was commonly found in the gills, stomachs and intestines in both grass carps and bighead carps, and on the skin surface of one fish, but not in other organs. Proper handling of freshwater fish for cooking, especially the gills and gut, is recommended to prevent acquisition of L. hongkongensis, and other freshwater fish related infections.

Effects of Gypsophila saponins on bacterial growth kinetics and on selection of subterranean clover rhizosphere bacteria.

Plant secondary metabolites, such as saponins, have a considerable impact in agriculture because of their allelopathic effects. They also affect the growth of soil microorganisms, especially fungi. We investigated the influence of saponins on rhizosphere bacteria in vitro and in soil conditions. The effects of gypsophila saponins on the growth kinetics of rhizosphere bacteria were studied by monitoring the absorbance of the cultures in microtiter plates. Gypsophila saponins (1%) increased the lag phase of bacterial growth. The impact of gypsophila saponins on subterranean clover rhizosphere was also investigated in a pot experiment. The addition of gypsophila saponins did not modify clover biomass but significantly increased (twofold with 1% saponins) the weight of adhering soil. The number of culturable heterotrophic bacteria of the clover rhizosphere was not affected by the addition of gypsophila saponins. Nevertheless, the phenotypical characterization of the dominant Gram-negative strains of the clover rhizosphere, using the Biolog system, showed qualitative and quantitative differences induced by 1% saponins. With the addition of saponins, the populations of Chryseomonas spp. and Acinetobacter spp., the two dominant culturable genera of control clover, were no longer detectable or were significantly decreased, while that of Aquaspirillum dispar increased and Aquaspirillum spp. became the major genus. Aquaspirillum dispar and Aquaspirillum spp. were also the dominant rhizosphere bacteria of Gypsophila paniculata, which greatly accumulates these saponins in its roots. These results suggest that saponins may control rhizosphere bacteria in soil through rhizodeposition mechanisms.

Use of cefoperazone MacConkey agar for selective isolation of Laribacter hongkongensis.

A new selective medium, cefoperazone MacConkey agar (CMA), was developed for primary isolation of Laribacter hongkongensis from stool. Its performance in quantitative recovery and in a clinical evaluation of 4,741 human diarrheal stool specimens was superior to that of charcoal cefoperazone deoxycholate agar. In addition, with CMA, Arcobacter butzleri was unexpectedly isolated from the stools of six patients.

Laribacter hongkongensis: a potential cause of infectious diarrhea.

In this study, we describe the isolation of Laribacter hongkongensis, a recently described genus and species of bacterium, in pure culture on charcoal cefoperazone deoxycholate agar from the stool of six patients with diarrhea. Three patients were residents of Hong Kong, and three of Switzerland. In none of the stool samples obtained from these six patients was Salmonella, Shigella, enterohemorrhagic Escherichia coli, Vibrio, Aeromonas, Plesiomonas, or Campylobacter recovered. Rotavirus antigen detection, electron microscopic examination for viruses, and microscopic examinations for ova and cysts were all negative for the stool samples obtained from the three patients in Hong Kong. Enterotoxigenic E. coli was recovered from one of the patients in Hong Kong. Unlike L. hongkongensis type strain HKU1, all the six strains were motile with bipolar flagellae. Sequencing of the 16S ribosomal RNA genes of the six strains showed that they all had sequences with only 0-2 base differences to that of the type strain. Pulsed field gel electrophoresis of the SpeI digested genomic DNA of the six isolates and that of the type strain revealed that the seven isolates were genotypically unrelated strains. More extensive epidemiologic studies should be carried out to ascertain the causative association between L. hongkongensis and diarrhea and to define the reservoir and modes of transmission of L. hongkongensis.

Distribution of the meningococcal insertion sequence IS1301 in clonal lineages of Neisseria meningitidis.

The distribution of the meningococcal insertion sequence IS1301 was analysed in 496 strains of different serogroups and clonal lineages of Neisseria meningitidis, and in 64 neisserial strains other than N. meningitidis. IS1301 was found in meningococci, but not in apathogenic Neisseria sp. and Neisseria gonorrhoeae. The copy numbers of IS1301 varied between 2 and 17 per genome. IS1301 positive strains were mostly found among the serogroups 29E, W135, X, and Y. Clonal lineages of serogroup A, B, and C meningococci associated with epidemic meningococcal disease were rarely positive for IS1301.

Airborne gram-negative bacterial flora in animal houses.

The concentration and the species composition of airborne gram-negative bacteria were studied in four cattle houses, one pig house and one poultry barn. On average only between 0.02 and 5.2% of the total number of culturable aerobic bacteria were identified as gram-negative bacteria. Obligate anaerobic gram-negative bacteria were not isolated at all. In the airborne gram-negative bacterial flora the following bacterial families dominated: the Enterobacteriaceae, the Pseudomonadaceae and the Neisseriaceae. Within the family of the Enterobacteriaceae the species Escherichia coli and Enterobacter agglomerans were predominant. In animal houses using straw as bedding material Ent. agglomerans was most frequent, whereas in animal houses without litter E. coli was mainly found. Airborne Neisseriaceae were isolated very frequently in cow barns with Acinetobacter lowffii as the primary species. Airborne Pseudomonadaceae were found in high concentrations during periods of high air humidity. The results presented may also give some indications on the origin and sources of airborne endotoxins in animal housing.

Semiquantitative culture results and pathogenic significance of obligate anaerobes in peritonsillar abscesses.

We studied the bacteria in consecutive peritonsillar abscesses using semiquantitation of the primary culture findings and correlated the results to clinical parameters. Puncture-aspirated pus from 42 abscesses yielded 133 isolates. Group A streptococci were isolated 10 times and, unlike other bacteria, were isolated 4 times in pure culture; other beta-hemolytic streptococci were found in 8 abscesses, and anaerobes were found in 28. The infections were polymicrobial, with two to seven bacteria in 83%. Anaerobes were more abundant than nonanaerobes; members of the genera Streptococcus, Bacteroides, Peptostreptococcus, and Fusobacterium were the most important quantitatively, considering both frequency and abundance. In patients with ongoing antibiotic treatment, nonanaerobes (but not anaerobes) were less abundant than in untreated patients. The abundance of obligate anaerobes (specifically cocci and gram-positive rods) correlated to the severity of illness as defined by fever and short duration before hospitalization. With other groups of bacteria, no such correlation was found. The correlation was not explained by a difference between the antibiotic-treated and the untreated patients. The results indicate the value of the semiquantitation of culture data and the frequency and pathogenic significance of obligate anaerobes in peritonsillar abscesses.

Branhamella catarrhalis as a lower respiratory tract pathogen in patients with chronic lung disease.

To determine the possible role of Branhamella (formerly Neisseria) catarrhalis as a respiratory pathogen, we screened quality sputa (defined by cellular criteria) that showed numerous gram-negative cocci on Gram's stain for the presence of B catarrhalis. In an eight-month period, 52 isolates of B catarrhalis were identified in adults attending a hospital for chest diseases. During this period B catarrhalis was the third most common potential pathogen isolated from sputa. Twenty-two patients (42%) had associated patchy bronchopneumonic or lobar infiltrates. All had negative blood cultures and a generally mild clinical course. The majority of strains (73%) of B catarrhalis produced beta-lactamase and were resistant to penicillin and ampicillin. Isolates (including beta-lactamase-producing strains) were susceptible to erythromycin, tetracycline, and trimethoprim-sulfamethoxazole. These studies demonstrate that in patients with chronic lung disease, the presence of B catarrhalis in sputum can be suspected on the basis of a Gram's stain and may be associated with the development of new pneumonic infiltrates. Since these organisms frequently produce beta-lactamase, empiric antimicrobial therapy should include agents other than the penicillins.

Phenotypic differentiation of Cardiobacterium hominis, Kingella indologenes and CDC group EF-4.

Eleven strains of Cardiobacterium hominis, two strains of Kingella indologenes and six strains of CDC group EF-4 were characterized. Since all three taxa are oxidase-positive, fastidious gram-negative rods with relatively few positive reactions, they may be easily confused in the microbiological laboratory. Common characteristics are acid production from glucose, aerobic growth in semi-solid agar and very slow anaerobic growth. Group EF-4 is distinguished from the other two species by its capacity to produce catalase and its lack of indole production. Cardiobacterium hominis can be distinguished from Kingella indologenes by its ability to ferment mannitol and sorbitol and by differences in enzyme production. The three taxa also differ considerably with regard to morphological and cultural characteristics.

Use of the API NeIdent system for identification of pathogenic Neisseria spp. and Branhamella catarrhalis.

The API NeIdent system (Analytab Products, Plainview, N.Y.) was evaluated for identifying Neisseria spp. and Branhamella catarrhalis commonly isolated from clinical specimens. The system identified 90% of 303 Neisseria gonorrhoeae isolates, 71% of 113 Neisseria meningitidis isolates, and 63% of 16 Neisseria lactamica isolates but failed to identify any of 22 B. catarrhalis isolates. Testing of gonococcal strains of various auxotypes revealed no relationship between nutritional requirements and NeIdent profile numbers. With the Neisseria species, interpretation of the cinnamaldehyde-coupled beta-naphthylamine reactions was difficult and resulted in profile numbers not listed in the Profile Register. Positive resazurin-glucose reactions resulted in unlisted numbers for all B. catarrhalis strains. Inconsistent results were also obtained when 62 N. gonorrhoeae isolates were tested more than once on the strip. In all cases, profile variability and failure to identify these organisms were related to the beta-naphthylamide substrate tests. Expansion of the data base and modification of the substrate formulations or their interpretive criteria may increase the reliability of the NeIdent system for identifying Neisseria spp. and B. catarrhalis.

[Neuraminidase activity of nonpathogenic Neisseria]. / Neiraminidaznaia aktivnost' nepatogennykh neisserii.

It was revealed earlier by the authors that N. meningitidis of the principal serological groups A, B, and C possessed neuraminidase activity. In the present work it was shown that this sign was genus-specific, and that this property was also possessed by the representatives of nonpathogenic neisseria habituating in the nasopharynx, However, the enzymatic activity in nonpathogenic neisseria was less pronounced than in meningococci, and required more prolonged contact of the enzymatic-substrate mixture for its detection. There was revealed a direct relationship between the neuraminidase activity and the growth phase of the microorganisms, whose maximum coincided with the exponential phase of bacterial growth, this apparently being associated with the extracellular character of its origin.

Spoilage association of chicken leg muscle.

The ability of pure cultures of bacteria isolated from spoiling chicken leg muscle to produce strong off-odors was tested by using sterile leg muscle sections. Changes in the flora during storage and the incidence and identity of organisms capable of producing strong off-odors were noted.

[Effect of pH on bacteria in early log phase]. / Influence du pH sur des bactéries en phase de croissance

The bacteria harvested in the early log phase lyse when they are submitted to a pH above 10. The peptidoglycan is not degraded in these conditions. Thus, the authors used these properties to extract the peptidoglycan from several gram negative and gram positive bacteria.