Homologous and cross-reacting antibodies in the sera of gnotobiotic rats

Sera from Sprague–Dawley rats monoassociated with Clostridium perfringens, C. tertium, C. bifermenlans, Staphylococcus aureus, Escherichia coli, Proteus mirabilis, or Klebsiella pneumoniae for 4 weeks were assayed for homologous and cross-reacting antibodies against antigens on a variety of bacteria. A passive hemagglutination assay, with the antigen(s) consisting of bacteria conjugated to tanned sheep red blood cells, was used to assess antibody titers. Both homologous and cross-reacting antibodies were detected in sera that were collected from the monoassociated animals. Sera from monoassociated rats had agglutinating antibody to genera of bacteria that had not colonized their gastrointestinal tract. Although S. aureus shared some antigens with three species of Clostridium, the relationship was not reciprocal. Sera from rats monoassociated with E. coli, P. mirabilis, or K. pneumoniae had cross-reactive antibody against gram-positive and gram-negative bacteria, but did not have antibodies that could agglutinate H. influenzae type b. Monoassociation with C. perfringens resulted in the production of antibodies against a variety of gram-positive and gram-negative bacteria, but it did not induce cross-reactive antibodies against Corynebacterium diphtheriae, streptococci (groups A, C, and G), or Staphylococcus epidennidis.

Inhibition of granulocyte phagocytosis of Candida albicans by amphotericin B

Phagocytic activity of PMN's in five healthy and five burned patients were measured in vitro. Addition of 1 microgram per millilitre of amphotericin B to the assay produced a marked inhibitory effect of the phagocytic activity of PMN against C. albicans.

Immunity to experimental renal candidiasis in rats

Germfree rats were found to be more susceptible to intravenous challenge with Candida albicans than were conventional rats. The resistance of conventional rats could be overcome by increasing the challenge dose. The resistance of the germfree rat was enhanced by vaccination with Formalin-killed C. albicans in complete Freund adjuvant, complete Freund adjuvant, or incomplete Freund adjuvant. These results, and histological evidence obtained from infected gnotobiotic rats, provided further information on the mechanism of resistance to the disseminated form of candidiasis.

New blood culture medium

A growth medium with a specific oxidation-reduction potential containing peptone, dextrose, sodium succinate, sodium lactate, gelatin, sodium bicarbonate and blue tetrazolium, an indicator dye, in a tris(hydroxymethyl)aminomethane buffer was used to detect the presence of microorganisms in blood. The procedure involved the introduction of blood (and bacteria) into the growth medium with the dye in its colorless state. As the bacteria grew, they converted the dye to a visible blue color (formazan) with their reductases. The growth medium served as its own contamination control, since microbial growth and be detected by a color change before it was used for blood culture. The experiments described herein demonstrate that the composition of this medium (with the dye) provides a unique system that is able to make a reliable and rapid detection of both gram-positive and gram-negative microorganisms and yeasts (Candida albicans) commonly associated with bacteremia.

Bacterial association in the gastrointestinal tract of beagle dogs

Nine male beagle dogs, housed in either a conventional or locked environment for 2.5 years, were killed, and the bacterial flora present in various regions of each gastrointestinal tract was assessed by culture techniques, light microscopy, and scanning electron microscopy. All dogs possessed a complex microflora in their colons; in almost every dog anaerobes predominated. The highest number of bacteria cultured was 10(10)/g (dry weight) of tissue and contents; highest counts obtained with a Petroff-Hauser counting chamber were 10(10)/ml (wet weight). Although there was a consistency in the detectable genera, there were also noticeable differences in the flora of dogs housed under different environmental conditions. These differences included qualitative and quantitative changes in the flora as well as alterations in the distribution and localization of microorganisms along the gastrointestinal tract and in the crypts of Lieberkuhn. No bacterial layers were detected on the surfaces of stomach or proximal bowel in any of the dogs. Dogs housed in a conventional, open, environment had bacteria that occurred in layers on their ceca and colons and in their crypts of Lieberkuhn; however, dogs housed under "locked" environmental conditions did not possess them or had them less frequently. Dogs removed from the locked environment and kept (30 days) in conventional housing conditions were the only ones with detectable segmented filamentous microbes in their ilea. This study shows that the microbial flora does not simplify when dogs are housed in a locked environment. Indeed, it may increase in complexity and cause alterations in the bacterial flora that is associated closely with gastrointestinal epithelial cells and crypts of Lieberkuhn.

Nose, throat, and fecal flora of beagle dogs housed in "locked" or "open" environments

The microbial flora of the nose, throat, and feces of male beagle dogs housed in a "locked environment" (i.e. confined to germfree-style isolators and supplied with sterile food, air, and water) or an open environment were assessed between 26 and 30 months into the study. Forty-five genera and 170 different species or types of microorganisms were cultured from the nose, throat, and feces of the beagles. Clostridia, eubacteria, corynebacteria, bacteroides, lactobacilli, and anaerobic, gram-positive cocci accounted for most of the microbial diversity in the flora. Some of the facultative anaerobes, especially streptococci and lactobacilli (in feces), occurred in numbers that were comparable to the most numerous anaerobic species. Confinement to the locked environment resulted in an increased diversity of microorganisms in the flora, but the total microbial counts did not increase to any great extent. Even with the increased diversity of bacteria in the flora of confined dogs, some bacteria seemed to favor certain areas of the gastrointestinal tract over others. The increased diversity of bacteria observed in these confined dogs may pose some infectious disease problems for other mammals (including humans) that may be confined to a locked, ultra-clean environment for a prolonged period of time.

Effect of age, sex, and intestinal flora on the induction of colon tumors in rats

Germfree and conventional Sprague-Dawley rats were assessed for their susceptibility to intrarectally injected N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or N-methyl-N-nitrosourea (MNU). Adenocarcinoma of the colon was induced in germfree and conventional rats by both MNNG and MNU. The colons of germfree rats were more susceptible to the direct-acting carcinogens, as manifested by earlier morbidity and development of colon tumors (50% tumors within 30-35 wk), than were those of conventional rats (50% colon tumors within 48-50 wk). Germfree and conventional male rats were more susceptible to the carconogens than were their female germfree and conventional counterparts. Young (30 days old at the start of the experiment) germfree rats developed colon tumors more quickly (15-20 wk) than did older (60 days) germfree rats after intrarectal injections of MNNG. No colon tumors were observed in germfree and conventional rats after 75 weekly intrarectal injections with a buffer. Transplantation of an adenocarcinoma induced with MNU in a female rat to germfree and conventional rats showed that it was easily transplantable, required no immunosuppression, and had essentially the same morphologic characteristics as did the primary tumor.

Transparent Plastic Incubator for the Anaerobic Glove Box

An incubator designed for use inside an anaerobic glove box is described. The incubator is made of transparent plastic material, has sliding plastic doors, and can be made in various sizes from readily available materials.

The importance of clostridia in experimental intestinal strangulation

Hemorrhagic and ischemic strangulation of closed intestinal segments was sutdied in germ-free rats individually monocontaminated with one of eight separate species of clostridia. Ischemic strangulation was found to be as deadly as hemorrhagic strangulation in the presence of clostridia. Some clostridia were very toxic whereas others were relatively innocuous. The clostridia, ranked in the order of decreasing lethality, were: Clostridium perfringens type A, C. septicum, C. histolyticum, C. haemolyticum, C. bifermantans, C. sporogenes, C. tertium, and C. novyi type A. All species were readily established in the gastrointestinal tract of the nonoperated germ-free rat. The clostridia appear to be one of the most potentially lethal groups of organisms commonly found in the intestinal tract of human beings and animals.

Experimental Candida albicans infection in conventional mice and germfree rats

Swiss-Webster white mice were intravenously infected with various doses of Candida albicans, and the viable units in their spleens, livers, lungs, and kidneys were determined at various intervals after challenge. The results showed that C. albicans multiplied to a greater extent in the kidneys of mice than in their spleens, lungs, or livers. The infection in mice was chronic; increasing numbers of C. albicans were observed in their kidneys until about 17 to 24 days postchallenge. Clearance of C. albicans from infected kidneys was not symmetrical, since the number of viable C. albicans in one kidney did not coincide with the viable counts observed in the opposite kidney of that same animal. Male and female mice did not differ in their overall susceptibility (50% lethal dose test) or in the number of viable C. albicans in the kidneys at various time intervals after infection. C. albicans also multiplied in the kidneys of germfree rats; however, the peak of the C. albicans infection in their kidneys occurred earlier than in those of conventional mice.

Pneumatosis cystoides intestinalis

Pneumatosis cystoides intestinalis (PCI) is an uncommon disease of previously unknown etiology, characterized by the presence of gas-filled cysts in the walls of some portion of the gastrointestinal tract. This investigation showed that PCI was readily produced in the germfree rat by inoculating its peritoneal cavity with a pure culture of either C. perfringens or C. tertium. Similar inoculation of the germfree animal with any one of eight other clostridia species did not result in the formation of PCI. The bacterial theory for the formation of at least some cases of PCI is now established. This work suggests that part of the treatment of those fulminating diseases known to be frequently associated with PCI should be directed at controlling a possible clostridial infection.

Intraoperative bacterial transmission

A clinical evaluation of bacterial penetration through operating room gowns was made during 100 general surgical procedures. A comparison of the degree of penetration through the standard cloth and a commercially available disposible gown was carried out. Cloth gowns, even in the dry state, were shown to be ineffective bacterial barriers. In addition, routine laundering of scrub suits failed to eliminate pathogenic bacteria.

Survival of anaerobic and aerobic bacteria on cotton swabs in three transport systems

The capacity of aerobic and anaerobic bacteria to survive on cotton swabs placed into a dry gassed-out CO2-filled tube (DGT), dry sterile aerobic tube (DAT), and a tube containing a modified Stuarts' transport medium (MST), was assessed. Pseudomonas aeruginosa increased in numbers by 2 and 3 logs when stored in MST and DAT, respectively. The viability of P. aeruginosa, although retarded when compared to MSA and DAT, was not adversely affected by the CO2 environment in the DGT. The MST maintained relatively constant numbers of Streptococcus pyogenes during the 48-h storage period. The DAT and the DGT were unable to maintain the viability of S. pyogenes. Staphylococcus aureus, when stored in a DGT, DAT, or MST, was maintained in relatively constant numbers throughout the entire storage period. Of the four anaerobic bacteria evaluated (Bacteroides fragilis ssp. thetaiotaomicron, Bacteroides melaninogenicus ssp. asaccharolyticus, Fusobacterium nucleatum, and Peptostreptococcus anaerobius), only B. fragilis ssp. thetaiotamicron survived the 48-h storage period in the DGT. Under these test conditions the DGT did not adequately maintain the viability of the majority of anaerobic bacteria tested (when held on cotton swabs). However, the MST did maintain the viability of all species tested for at least the first 2 h of storage.

Immunity to Candida albicans induced by Listeria monocytogenes

Immunity to Candida albicans was studied in Swiss-Webster white female mice. Lethal and sublethal infections with C. albicans did not enhance immunity to a subsequent Listeria monocytogenes challenge. Mice sensitized to L. monocytogenes and then challenged with C. albicans intravenously were able to reduce the population of C. albicans in their kidneys after being boosted (rechallenged) with L. monocytogenes. However, the acquired cellular immunity so induced was very short-lived. Both C. albicans-sensitized and nonsensitized control mice showed an immediate-type and delayed-type skin test response to the cell wall antigen(s) of C. albicans but not to the cytoplasmic antigen(s). There did not appear to be any correlation between increase in skin test response and progression of the candida infection in mice.

S-adenosylmethionine metabolism by members of the genus Candida

S-Adenosylmethionine and S-methylmethionine: homocysteine methyltransferase activity was measured in cell-free extracts from seven different species (15 strains) of the genus Candida. All strains were able to form methionine via a transmethylation reaction with S-adenosylmethionine and homocysteine. However, some strains were not able to use S-methylmethionine as a methyl donor. Cell-free extracts from two strains of C. guilliermondii formed no methionine when S-methylmethionine was the methyl donor and one strain (C. guilliermondii, CDC) showed methionine-forming activity with S-adenosylmethionine and homocysteine only when the growth medium was supplemented with L-methionine. In general, greater methyltransferase activity was observed in the cell-free extracts from the more pathogenic members of the genus (i.e., C. albicans and C. tropicalis). Supplementation of the growth medium with L-methionine induced homocysteine methyltransferase activity. Ten of the 15 strains had the capacity to synthesize and store S-adenosylmethionine in their vacuole and all 15 strains had S-adenosylmethionine-degrading enzymes. The activity of the latter enzyme was not increased when cells were grown in L-methionine-supplemented medium.

Methionine biosynthesis and S-adenosylmethionine degradation during an induced morphogenesis of Candida albicans

Seven strains of Candida albicans were used in studies designed to delineate altered biochemical activity during an induced yeast to filamentous morphogenesis. Four of the strains studied underwent a rapid (1–2 h) yeast to filamentous transformation in a defined medium with glycine as the main nitrogen source; three other strains of C. albicans remained yeast-like under the same growth conditions. Cell-free extracts, prepared from cells harvested after various time intervals of growth in glycine medium, were used to measure enzymic capacity to form methionine, via the enzyme S-adenosylmethionine (or methylmethionine) homocysteine methyltransferase, and degrade S-adenosylmethionine. Increased enzymic capacity to synthesize methionine (with S-adenosylmethionine as methyl donor) and degrade S-adenosylmethionine appeared to correlate best with a yeast to filamentous transformation of C. albicans. Intracellular S-adenosylmethionine content also decreased with time, in all seven strains, when the cells were cultured in the glycine medium. S-adenosylmethionine may play a key role in the biochemical alterations that occur during the morphogenesis of C. albicans.

Chlamydospore production and germ-tube formation by auxotrophs of Candida albicans

A prototrophic strain and 21 auxotrophic strains of Candida albicans were assessed for their capacity to produce chlamydospores and germ tubes. All of the mutants were able to produce germ-tubes in human serum but only two mutants produced them in defined medium with L-alpha-amino-n-butyric acid as the sole source of nitrogen. Most auxotrophs were not able to produce chlamydospores on corn meal agar with 1% Tween 80, but they could be induced to do so if the medium was supplemented with their growth requirement(s). Although L-cysteine was able to support the growth of two methionine mutants, it did not support chlamydospore formation when added to corn meal agar with 1% Tween 80. Mutants of C. albicans that do not form chlamydospores could be incorrectly identified in laboratories that rely on chlamydospore formation for identification.