RS virus diagnosis: comparison of isolation, immunofluorescence and enzyme immunoassay

Two techniques for rapid diagnosis, immunofluorescence (IFAT) and enzyme immunoassay (EIA), have been compared with virus isolation in tissue culture for the detection of respiratory syncytial virus (RSV) in specimens of nasopharyngeal secretions. The specimens were obtained from children under five years of age suffering from acute respiratory illness, during a period of six months from January to June 1982. Of 471 specimens examined 54 (11.5%) were positive by virus isolation and 180 (38.2%) were positive by immunofluorescence. The bacterial contamination of inoculated tissue cultures unfortunately prevented the isolation of virus from many samples. Specimens from 216 children were tested to compare enzyme immunoassay and immunofluorescence. Of these 60 (27%) were positive by EIA and 121 (56%) were positive by IFAT. Our results suggest that the EIA technique although highly specific is rather insensitive. This may be because by the time these tests were done the original nasopharyngeal secretions were considerably diluted and contained more mucus fragments than the cell suspension used for IFAT. Of the three techniques, IFAT gives the best results although EIA may be useful where IFAT is not possible.     

Seroepidemiologic aspects of Neisseria meningitidis in homosexual men.

Neisseria meningitidis has been isolated with increasing frequency from specimens obtained from patients attending venereal disease clinics and is an occasional cause of genital infection. Among 383 homosexual men attending either a venereal disease clinic or a community screening clinic meningococci were cultured from specimens obtained from 35.0% of all the subjects, and with similar frequency in the two groups. Of the positive specimens 93.5% were from the throat, 5.8% from the rectum and 0.72% from the urethra. The serogroups and serotypes of the isolates were characteristic of those commonly found in nasopharyngeal specimens from other asymptomatic carriers. Gonococci were isolated from 8.6% of all the subjects and were 1.4 times more common in those who also harboured meningococci. Of the cultures positive for gonococci, 14.7% were from the throat and 85.3% from the rectum. The two bacteria were rarely isolated from the same site in the same individual. Gonococci, but not meningococci, were significantly more common (P less than 0.05) in the group attending the venereal disease, clinic than in the group attending the screening clinic, the rates being 17.1% and 7.0%.     

Antagonistic and bacteriocinogenic activity of Meningococci]

Antagonistic and bacteriocinogenic activity was studied in 169 strains of meningococci of various serological groups and with different localization in the human organism at the time of isolation. Bacteriocinogenic activity was revealed in all the meningococcus strains (by delayed antagonism method), and, in addition, antagonistic activity was found in 100 strains. The inhibitory activity was the greatest in meningococci isolated from the cerebrospinal fluid. The data obtained suggest an important inhibitory activity of meningococci, along with their resistance to the antagonistic activity of the nasopharyngeal microorganisms, in the manifestation of pathogenic properties in them.     

An easy method for detection of nasopharyngeal carriage of multiple Streptococcus pneumoniae serotypes

In this paper, a simplified method for detection of pneumococcal carriage and for revealing the presence of several serotypes in a nasopharyngeal sample is evaluated. Enrichment broth was used for transportation and for the initial culturing of samples. All specimens were examined directly by the capsular reaction test for the presence of any of the 91 known pneumococcal serotypes. Sub-culturing on blood agar was used for isolation of the pneumococcal strains detected in the primary broth culture. A total of 693 nasopharyngeal swabs were obtained among children, their parents and employees in day care centres. Pneumococci were observed in 363 samples and 36 of these (9.9%) contained more than one serotype (multiple carriages). Two persons carried 3 different serotypes simultaneously. A significant increase in the positive sampling rate (5.8%) was achieved by using the simplified method compared to conventional streaking of the swabs directly on blood agar (p<0.0001).     

An evaluation of a nutrient medium for isolating and cultivating Helicobacter pylori

Selective Helicobacter agar containing the selective supplement and blood, adding ex tempore, for the isolation and cultivation of H. pylori was developed. The Helicobacter agar was studied with the use of 5 newly isolated H. pylori strains, 13 bacterial associated cultures, as well as 21 inoculated biopsy specimens of the gastric and duodenal mucosa of patients with peptic ulcer. The study revealed that Helicobacter agar ensured the growth of H. pylori and their isolation from clinical material. The positive results after the inoculation of the specimens of biopsy material on Helicobacter agar and control media was 85%. In addition, the study of Helicobacter agar showed that it also exhibited pronounced selective properties with respect to bacterial associations, not inhibiting the growth of Helicobacter organisms and retaining their main biological properties. It is possible to recommend Helicobacter agar for use in laboratory practice in diagnosing Helicobacter-associated diseases.     

Growth medium for Neisseria meningitidis isolation

Growth medium for isolation of N. meningitidis, which do not require addition of serum and based on previously developed medium for cultivation of bacteria from Haemophilus genus (without growth factors V and X) was constructed. Selective properties of the medium in relation to meningococci were determined by addition of vancomycin and colistin--antibacterial supplement inhibiting growth of nonpathogenic Neisseria and outside microflora. Developed medium was successfully approved during examination of children for nasopharyngeal carriage of meningococci.     

An easy method for detection of nasopharyngeal carriage of multiple Streptococcus pneumoniae serotypes

In this paper, a simplified method for detection of pneumococcal carriage and for revealing the presence of several serotypes in a nasopharyngeal sample is evaluated. Enrichment broth was used for transportation and for the initial culturing of samples. All specimens were examined directly by the capsular reaction test for the presence of any of the 91 known pneumococcal serotypes. Sub-culturing on blood agar was used for isolation of the pneumococcal strains detected in the primary broth culture. A total of 693 nasopharyngeal swabs were obtained among children, their parents and employees in day care centres. Pneumococci were observed in 363 samples and 36 of these (9.9%) contained more than one serotype (multiple carriages). Two persons carried 3 different serotypes simultaneously. A significant increase in the positive sampling rate (5.8%) was achieved by using the simplified method compared to conventional streaking of the swabs directly on blood agar (p < 0.0001).     

Clinical Evaluation of Enteric Media in the Primary Isolation of Salmonella and Shigella

Over a 1-year period, media for the isolation of enteric pathogens were compared on 455 stool specimens. Fifty-three pathogens were isolated, of which 56% were Shigella sonnei and 13% were Sh. flexneri. Of these isolates, 90% were found on xylose-lysine-desoxycholate agar, 87% on Hekton enteric agar, and 80% on MacConkey without crystal violet with 2% agar and 0.007% neutral red, but only 28% were recovered on Salmonella-Shigella agar. Less than one-half of the shigellae were recovered after Selenite-F enrichment. On the other hand, enrichment was the most helpful method for isolating salmonellae. Studies on cultures from which mixed isolates were obtained indicated that numbers and chance distribution have an effect on the results obtained. The performance of Salmonella-Shigella agar in the isolation of enteric pathogens was inferior, and the effort involved to obtain those isolates was greater than for Hekton enteric and xylose-lysine-desoxycholate agars.     

Membrane Filter Method for the Isolation and Enumeration of Pseudomonas aeruginosa from Swimming Pools

A membrane filter technique using black membrane filters, MacConkey agar and fluorescence under ultraviolet (UV) light was investigated for the quantitative isolation of Pseudomonas aeruginosa from swimming pools. Three thousand four hundred forty-five samples were collected from public swimming pools and enumerated by this method over a 6-month period. Fluorescent cultures were isolated from 222 specimens. Seventy-seven of these fluorescent cultures were selected for biochemical screening, with 75 (97%) being verified as P. aeruginosa. To further assess the specificity and sensitivity of this UV screening technique, a comparative study was made of some morphological and biochemical characteristics of fluorescent pseudomonads obtained from different sources. The sensitivity of the method was unimpaired by either colony types or biochemical variations of P. aeruginosa. The failure of the other two fluorescent species, P. fluorescens and P. putida, to grow and/or fluoresce on MacConkey agar at 37 C illustrates the specificity of this technique. Further studies are needed to compare the viability of P. aeruginosa on MacConkey agar to that of efficacious nonselective media.     

Sensitivity of Agar Overlay Method for the Recognition of Enteroviruses

COMPARISON OF THE AGAR OVERLAY TECHNIQUE WITH THE FLUID CULTURE TECHNIQUE FOR ISOLATION AND IDENTIFICATION OF ENTEROVIRUSES SHOWED THE FORMER TO BE USEFUL: (i) for isolation of enterovirus when the number of virus particles was too small to produce detectable cytopathic effect (CPE) in fluid cultures, (ii) for isolation of echovirus 22 which did not produce detectable CPE in fluid cultures, (iii) as an aid to rapid differentiation of enteroviruses, and (iv) for differentiation of viruses in mixed infections. Nonpolio enterovirus isolation experience in the New Haven area over a 4-year period is presented. It was concluded that the agar overlay technique is both useful and relatively simple for routine examination of clinical specimens in a diagnostic laboratory.     

Dubos Oleic Acid Agar Medium in the Differentiation of Meningococci and Gonococci

Growth on Dubos oleic acid agar plates, incubated for 48 hr at 37 C in candle jars, provides a method for differentiating meningococci from gonococci. All of our 54 strains of meningococci, but none of the 49 strains of gonococci, grew on this medium.     

A note on colony-blot double-stain method for isolation of Vibrio cholerae serotype 01 from specimens heavily contaminated with non-01 Vibrio cholerae

A colony-blot double-stain method was developed to identify individual colonies of Vibrio cholerae serotype 01 (pandemic strain) in mixed bacterial cultures on solid media. The colonies are transferred from agar to nitrocellulose membranes for an enzyme-linked immunosorbent assay (ELISA). Colonies of 01 vibrios bind the enzyme-linked antibodies and appear as brown dots on the membranes; pale black dots develop at the site of replicated colonies of other bacteria as a result of the activity of endogenous oxidase-like enzymes and serve as reference points. The results indicate that the colony-blot double-stain method is useful for the isolation of colonies of V. cholerae serotype 01 in specimens that are heavily contaminated with non-01 vibrios.     

Glycine-containing selective medium for isolation of Legionellaceae from environmental specimens.

Glycine, at a final concentration of 0.3%, has been shown to be an excellent selective agent for the isolation of Legionellaceae. Stock cultures of Legionella pneumophila were not inhibited on buffered charcoal-yeast extract agar containing the amino acid. Among the other Legionellaceae tested, only one of two strains of L. dumoffii and two of six strains of L. micdadei were appreciably inhibited. This medium permitted the isolation of L. pneumophila from environmental specimens with marked inhibition of many non-Legionellaceae bacteria. The selectivity of the medium was subsequently improved by the incorporation of vancomycin (5 microgram/ml) and polymyxin B (100 U/ml). This selective medium, glycine-vancomycin-polymyxin B agar, should facilitate the recovery of Legionellaceae from environmental sources.     

Lysine mannitol glycerol agar (LMG) and LMG with sulphamandelate for isolation of Salmonella spp. from clinical specimens

Lysine mannitol glycerol agar (LMG) was compared to xylose lysine deoxycholate agar (XLD), bismuth sulphite agar (BS), and Salmonella-Shigella agar (SS) for the ability to detect Salmonella spp. in clinical specimens, primarily faeces samples. During an 8-month period, 15 salmonellae were isolated from 940 faeces on LMG, while 14 strains were obtained on XLD, 11 on SS and only 3 strains on BS. Salmonella typhi was recovered from two blood cultures in 24 h on LMG, compared to 48 h on BS. LMG was augmented by addition of a sulphacetamide/mandelic acid (sulphamandelate) selective supplement (LMGS). During a 20-month period, 43 salmonellae were isolated from 2622 faeces on LMG and LMGS. The selectivity of LMGS was superior to that of LMG with no decrease in sensitivity of detection; all salmonellae isolated on LMG were isolated on LMGS. Both LMG and LMGS were suitable for routine use in the isolation of Salmonella spp. from clinical specimens.     

A New Isolation Method for Labyrinthulids Using a Bacterium, Psychrobacter phenylpyruvicus

A new isolation method for labyrinthulids, marine microbes with spindle-shaped vegetative cells and gliding movement, is presented. The method for isolating labyrinthulids has been found to be more difficult and less reproducible than that for thraustochytrids, classified in the same order. So far serum seawater agar fortified with antibiotics has been proposed to be the best for isolation of labyrinthulids. The method presented here involves placing plant samples on an agar medium on which a marine bacterium, Psychrobacter phenylpyruvicus, has been grown. The new method, which utilizes fallen mangrove leaves as source material, was more than twice as effective as isolation agar medium without the bacterium. The increased effectiveness appears to derive partly from the bacterial colonies' delaying extension of fungal mycelium. The bacterium was more effective for the isolation of labyrinthulids than either the bacterium Shewanella sp. or the yeast Rhodotorula rubra.     

OBSERVATIONS ON THE ISOLATION OF SALMONELLAE FROM SELENITE BROTH

SUMMARY: Studies of growth curves of enterobacteria in selenite broth containing different carbohydrates showed that whereas mannitol and lactose brought about a steep fall in coli-aerogenes bacteria, mannitol improved the growth of Salm. typhi-murium . With mixed cultures of Cit. freundii I and Salm. typhi-murium the presence of lactose, utilizable by the former, adversely affected the viable count of the latter.
Comparative studies with routine faeces specimens showed that selenite broth was an efficient selective medium with MacConkey's agar; but much better results were obtained when it was combined with deoxycholate-citrate agar. Gentian violet introduced into selenite broth improved its selectivity for most Salmonella types when MacConkey's agar was used for final isolation.     

Comparison of Media for Direct Isolation and Transport of Shigellae from Fecal Specimens

Xylose-lysine-deoxycholate (XLD) agar, SS agar, and MacConkey agar for isolating shigellae from fecal specimens were compared. XLD agar was superior to both SS agar and MacConkey agar for isolating Shigella sonnei, and both XLD and SS agar were superior to MacConkey agar for isolating S. flexneri. Direct plating of the fecal specimens in the field resulted in a greater yield of shigellae as compared to transporting specimens to the laboratory either in holding media or enrichment broth. Buffered glycerol saline was superior to other transport media evaluated, yielding 83% of shigella isolates when plated within 48 hr as compared to direct plating. The combination of XLD agar and SS agar is recommended for direct isolation of shigellae, and, whenever possible, these solid media should be taken to the bedside and inoculated directly.     

Evaluation of Three Media for Selective Isolation of Gram-Positive Bacteria from Burn Wounds

Three media, phenylethyl alcohol blood agar, esculin-mannitol agar, and Columbia CN blood agar, were studied for the selective isolation of gram-positive bacteria from swab cultures of burn wounds.     

Modification of Cycloserine Cefoxitin Fructose Agar to Suppress Growth of Yeasts from Stool Specimens

Cycloserine cefoxitin fructose agar is a widely used selective isolation medium for Clostridium difficile from stool specimens. Yeasts often colonize in the intestine of C. difficile disease patients and, if colonized heavily, pure culture of C. difficile can be delayed. The aim of this study was to modify cycloserine cefoxitin fructose agar to suppress the growth of yeasts. Antimicrobial activities of three commonly available antifungal agents were tested against recent clinical isolates of Candida species. Amphotericin B was most active in inhibiting all isolates by ≤0.5 mg/L concentration. Cycloserine cefoxitin fructose agar was modified by adding 2 mg/L of amphotericin B. Serial ten-fold dilution of stool specimens from 126 suspected C. difficile -associated diarrhea patients were cultured both on cycloserine cefoxitin fructose agar plates and modified agar plates. Yeasts grew from 60 specimens on cycloserine cefoxitin fructose agar, but none grew on the modified medium. Growth of C. difficile was detected from 37 and 39 of 126 specimens on cycloserine cefoxitin fructose agar and modified medium, respectively. The number of C. difficile colonies was similar on both media. In conclusion, 2 mg/L of amphotericin B supplementation to cycloserine cefoxitin fructose agar can facilitate the isolation of C. difficile from stool specimens which are densely colonized with yeasts.