The preservation of gonococci in liquid nitrogen

The secretome of the fish pathogen Tenacibaculum maritimum includes soluble virulence-related proteins and outer membrane vesicles

Tenacibaculum maritimum, the etiological agent of tenacibaculosis in marine fish, constitutively secretes extracellular products (ECPs) in which protein content has not been yet comprehensively studied. In this work, the prevalence of extracellular proteolytic and lipolytic activities related to virulence was analyzed in 64 T. maritimum strains belonging to the O1-O4 serotypes. The results showed the existence of a great intra-specific heterogeneity in the enzymatic capacity, particularly within serotype O4. Thus, the secretome of a strain belonging to this serotype was characterized by analyzing the protein content of ECPs and the possible production of outer membrane vesicles (OMVs). Notably, the ECPs of T. maritimum SP9.1 contain a large amount of OMVs that were characterized by electron microscopy and purified. Thus, ECPs were divided into soluble (S-ECPs) and insoluble fractions (OMVs), and their protein content was analyzed by a high-throughput proteomic approach. A total of 641 proteins were identified in ECPs including some virulence-related factors, which were mainly found in one of the fractions, either OMVs or S-ECPs. Outer membrane proteins such as TonB-dependent siderophore transporters and the type IX secretion system (T9SS)-related proteins PorP, PorT, and SprA appeared to be mainly associated with OMVs. By contrast, putative virulence factors such as sialidase SiaA, chondroitinase CslA, sphingomyelinase Sph, ceramidase Cer, and collagenase Col were found only in the S-ECPs. These findings clearly demonstrate that T. maritimum releases, through surface blebbing, OMVs specifically enriched in TonB-dependent transporters and T9SS proteins. Interestingly, in vitro and in vivo assays also showed that OMVs could play a key role in virulence by promoting surface adhesion and biofilm formation and maximizing the cytotoxic effects of the ECPs. The characterization of T. maritimum secretome provides insights into ECP function and can constitute the basis for future studies aimed to elucidate the full role of OMVs in the pathogenesis of fish tenacibaculosis.

Long term storage of fastidious bacteria (Neisseria spp. and Haemophilus spp.) with swab preservation at -80 °C

Preservation of strains is important to further studies and characterization; we have shown a technique of long-term preservation of Neisseria spp. and Haemophilus spp. by freezing cotton tip swabs impregnated with fastidious organisms at -80 °C without the addition of cryoprotectants.

Culturable microbiota of ranched southern bluefin tuna (Thunnus maccoyii Castelnau)

AIMS

The Australian tuna industry is based on the ranching of wild southern bluefin tuna (SBT, Thunnus maccoyii). Within this industry, only opportunistic pathogens have been reported infecting external wounds of fish. This study aimed to identify different culturable bacteria present in three cohorts of SBT and to determine normal bacteria and potential pathogens in isolates from harvest fish and moribund/dead fish. Post-mortem changes in the microbiota were also studied.

METHODS AND RESULTS

Moribund/dead showed a greater proportion of members from the family Vibrionaceae than harvested fish; the latter presented mainly non-Vibrio species. In harvested fish spleens, Vibrio splendidus I complex was the most commonly identified group among Vibrio isolates, while most groups from the family Vibrionaceae were isolated from gills. For moribund/dead, Vibrio chagasii and Photobacterium damselae subsp. damselae were common in gill, spleen and kidney samples. Non-Vibrio isolates from gills were characterized using 16S rRNA sequencing as Flavobacteriaceae and classes Gammaproteobacteria and Alphaproteobacteria, mainly from the genera Winogradskyella and Tenacibaculum. Post-mortem changes showed dynamic shifts in bacterial dominance in gills, with Vibrionaceae and non-Vibrio spp. found in similar proportions initially and types related to Pseudoalteromonas ruthenica prevailing after 27 h. Spleen samples showed little bacterial growth until 5 h post-mortem, while various Vibrio-associated species were isolated 27 h post-mortem.

CONCLUSIONS

Bacterial isolates found include a range of potentially pathogenic bacteria that should be monitored though most of them have yet to be associated with disease in tuna.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study forms a foundation for future research into the bacterial population dynamics under different culture conditions of SBT. An understanding of the bacterial compositions in SBT is necessary to evaluate the effects of some bacterial species on their health.

Physical characterisation of Tenacibaculum maritimum for vaccine development

AIMS

Tenacibaculum maritimum is a well known fish pathogen worldwide, affecting many fish species including Atlantic salmon in Tasmania, Australia. The aim of this study was to characterise and understand the similarities and differences between the isolates in order to select isolates for later pathogenicity and vaccination trials.

METHODS AND RESULTS

Several physical characterisation tests were carried out: whole cell protein profiles, lipopolysaccharide profiles (LPS), extracellular product profiles (ECP), indirect immunofluorescent antibody test (IFAT) and hydrophobicity. The Tasmanian strains of T. maritimum appear relatively homogeneous physically, but antigenically different. All isolates were hydrophobic and produce a variety of ECP profiles. There were two isolates that stand out in all assays (89/4747 and 01/0356-7) and showed great variation from the other isolates. All isolates have been confirmed as T. maritimum.

CONCLUSIONS

Based on the tests carried out three isolates were chosen for in vivo trials: 89/4747, 89/4762, 00/3280.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to characterise T. maritimum isolates from Tasmanian waters. The opportunity to develop vaccines for the Tasmanian salmonid aquaculture industry is enhanced by a greater understanding of the physical characteristics of pathogens.

Protectants used in the cryopreservation of microorganisms

The cryoprotective additives (CPAs) used in the frozen storage of microorganisms (viruses, bacteria, fungi, algae, and protozoa) include a variety of simple and more complex chemical compounds, but only a few of them have been used widely and with satisfactory results: these include dimethylsulfoxide (Me2SO), glycerol, blood serum or serum albumin, skimmed milk, peptone, yeast extract, saccharose, glucose, methanol, polyvinylpyrrolidone (PVP), sorbitol, and malt extract. Pairwise comparisons of the cryoprotective activity of the more common CPAs used in cryomicrobiology, based on published experimental reports, indicate that the most successful CPAs have been Me2SO, methanol, ethylene glycol, propylene glycol, and serum or serum albumin, while glycerol, polyethylene glycol, PVP, and sucrose are less successful, and other sugars, dextran, hydroxyethyl starch, sorbitol, and milk are the least effective. However, diols (as well as some other CPAs) are toxic for many microbes. Me2SO might be regarded as the most universally useful CPA, although certain other CPAs can sometimes yield better recoveries with particular organisms. The best CPA, or combination of CPAs, and the optimum concentration for a particular cryosensitive microorganism has to be determined empirically. This review aims to provide a summary of the main experimental findings with a wide range of additives and organisms. A brief discussion of mechanisms of CPA action is also included.

Increased adhesiveness and internalization of Neisseria gonorrhoeae and changes in the expression of epithelial gonococcal receptors in the Fallopian tube of copper T and Norplant users

Interaction of Neisseria gonorrhoeae with the oviductal epithelium in vitro was examined in 2 cm length segments obtained after surgical sterilization from users of copper T intrauterine device (IUD) or Norplant and control women. Segments perfused with N.gonorrhoeae suspensions were incubated from 30 min up to 4 h, fixed, frozen and cut in 6--10 microm sections. Bacteria were detected immunohistochemically with rabbit anti-gonococcal serum followed by light and confocal microscopy. Adhesion and internalization of gonococci by epithelial cells were observed at all incubation times, and both were higher in explants from users of copper T IUD or Norplant implants than controls. The epithelium of controls expressed CD66 and syndecan-1; but CD46 was found in only one out of six cases. The epithelium of copper T IUD users expressed CD66 but not syndecan-1 or CD46. Users of Norplant exhibited expression of CD46, CD66 and syndecan-1. Label was always found along the luminal border of the epithelium. There were more intraepithelial lymphocytes in users of contraceptive methods than in controls. Results indicate that (i) N.gonorrhoeae invade the oviductal epithelium from the first minutes of exposure, (ii) the epithelium is constitutively endowed with two known receptors for the gonococcus, CD66 and syndecan-1, (iii) copper T IUD and Norplant users exhibit higher rates of attachment and internalization of the gonococcus into the oviductal epithelium associated with changes in expression of gonococcal receptors.

The preservation of micro-organisms in biological specimens stored at-70 degrees C

The preservation of micro-organisms that may be found on the skin was studied by storage in liquid media at--70 degrees C. In the first part of the study the performance of 12 varieties of suspending media was evaluated with pure cultures of 17 species of micro-organisms maintained in the laboratory. After storage for 1 year the best medium (Oxoid Nutrient Broth with 15% glycerol) showed a mean survival for all organisms studied of 83.8%, with no significant differences between organisms. Even the worst medium (distilled water) permitted greater than 40% survival at 1 year. No changes in the characteristics of these micro-organisms were detected after 6 months storage in glycerol broth. In the second part of the study nose swabs were suspended in one representative medium (Bacto Nutrient Broth containing 7% glycerol). The mean percentage survival of staphylococci in these suspensions after 1 year's storage at - 70 degrees C was 75.4%. These results indicate that coagulase-negative coagulase-negative staphylococci in samples of skin flora may be stored under these conditions for long periods, greatly reducing the work-load in epidemiological studies of infection.

Acquisition of new genes by oral Neisseria

It is suggested that part of the increased pharyngeal carriage of meningococci reported in patients with gonorrhoea is due to misidentification of gonococci which have been transformed to maltose fermenters by DNA from normal throat flora. The distribution of specific aminopeptidases in strains of gonococci, meningococci isolated from the throat and meningococci from systemic infections is consistent with this view. Gonococci oxidising maltose and gonococci with gamma-L-glutamyl aminopeptidase activity, both factors regarded as typical of Neisseria meningitidis, can be produced in vitro by transformation with DNA from N lactamica and N meningitidis. The clinical and theoretical implications of such changes are discussed.

Rectal gonorrhoea in male homosexuals. Presentation and therapy

In a review of rectal gonorrhoea 73 episodes were studied in 65 homosexual men. The presenting signs and symptoms were carefully noted. Treatment with a single injection of spectinomycin hydrochloride 2 g resulted in a cure rate of 94.5%. The relatively high treatment failure rate associated with rectal gonorrhoea may possibly be due to microbial mechanisms.

Bulk growth of Neisseria gonorrhoeae type 1 in a biphasic system

A biphasic system for the bulk growth of Neisseria gonorrhoeae is described. It appears to combine the convenience of liquid media with the growth qualities of solid media. By using the agar in dialysis tubes rather than as slabs the surface-to-volume ratio was improved and harvesting made easier. The system is also useful in isolating gonococci from blood and joint fluids in patients with disseminated infection.

Composition of the lipopolysaccharide of Neisseria gonorrhoeae

Analysis of glycose and fatty acid content of lipopolysaccharide extracted from 38 strains of Neisseria gonorrhoeae indicated that glycoses common to colonial types 1 to 5 were glucose, mannose, and galactose, N-acetylneuraminic acid, 2-keto-3-deoxyoctulosonic acid (KDO), glucosamine, and galactosamine were also invariably present. Virulent colonial types 1 and 2 contained no rhamnose, in contrast to avirulent types 3 to 5 and several strains of the nonpathogenic species N. sicca and N. lactamica. Fucose, characteristic of these nonpathogenic species, was not present in the gonococci. Variation in the concentration of individual glycoses in different strains was also noted. Mannose-KDO, galactose-KDO, and glucose-KDO ratios of virulent gonococci exceeded those of avirulent organisms, except that the correlation for glucose was not quite so striking. This relationship was not found in N. sicca and N. lactamica strains. Fatty acid analyses of lipid A from gonococci showed that 10-, 12-, 14-, 16-, and 18-carbon acids, as well as 3-hydroxytetradecanoic acid, were present, but differences in concentration between colonial types, although evident in some cases, appeared less significant than glycose content.

Antibiotic sensitivity of gonococci in South Australia, 1974 to 1975

Routine testing of gonococci isolated from patients attending the Venereal Diseases Control Centre in Adelaide during the year July, 1974 to June, 1975, with a plate dilution method, showed that 93-8% of the 947 infecting strains were relatively sensitive to penicillin at a minimum inhibitory concentration (MIC) of 0-12 units/ml or less, and that 90% of the 648 strains tested were relatively sensitive to tetracycline at an MIC of 1-0 mug/ml or less. A small proportion only of isolates were relatively insensitive to penicillin and/or tetracycline. The routine treatment schedules which were used at the Centre proved adequate for infections over the whole range of sensitivities encountered. A significant proportion of the less sensitive strains were isolated from people infected in South-East Asia, most of whom had been inadequately treated there.

Prevalence of multiple antibiotic resistance in Neisseria gonorrhoeae

The susceptibility of 100 strains of Neisseria gonorrhoeae to five antimicrobial agents (penicillin, streptomycin, oxytetracycline, sulphamethoxazole, and gentamicin) was examined. Three strains were resistant to each antimicrobial, fourteen exhibited resistance to three or four of the five compounds tested, and 49 were resistant to a single agent, or to pairs of the selected agents. 34 strains were found to be fully sensitive to all of the compounds tested. It is suggested that resistance to gentamicin and sulphamethoxazole may be determined by a multiple resistance gene. The overall frequency of penicillin resistance was found to be 26-5 per cent (MIC greater than 0-06 mug/ml.), suggesting a significant decrease in resistance since 1968.

Carbon dioxide requirement of Neisseria gonorrhoeae growing on a solid medium

A survey of 120 isolations of Neisseria gonorrhoeae from male patients showed that 47 (39%) isolates were unable to produce visible colonies without a supply of exogenous carbon dioxide. Of 63 strains, 25 strains required CO2 for isolation but none exhibited a CO2 requirement beyond subculture 4. CO2-requiring strains deprived of CO2 appeared to lose their colony-forming ability exponentially in an environment otherwise conductive to growth. The CO2 requirement was found to be linked to the initiation of growth. An agar-to-agar replica-plating device was used to study the early stages of colonial growth. The CO2 requirement was also found to correlate with the various phases of the colony growth cycle, such that it was required during lag phase, not required during the phase of rapid growth, and returned as colonies aged. These results are discussed.

Lipids of Branhamella catarrhalis and Neisseria gonorrhoeae

Three strains of Branhamella catarrhalis and three strains of Neisseria gonorrhoeae were analyzed with regard to their phospholipid and neutral lipid composition. B. catarrhalis (ATCC 23246) contained 5.12 +/- 0.34% lipid, determined gravimetrically, compared to 8.56 +/- 0.15% and 9.73 +/- 0.06% for two strains of N. gonorrhoeae. Cardiolipin, phosphatidylglycerol, and phosphatidyl-ethanolamine were identified in extracts of both species. In addition, B. catarrhalis contained small amounts of phosphatidylcholine, and N. gonorrhoeae contained small amounts of lyso-phosphatidylethanolamine, which accumulated with autolysis accompanying late cell culture growth. The kinetics of change of relative amounts of phospholipids in both species were measured and found to differ substantially. Neutral lipid accounted for 30.4% of the total lipid of B. catarrhalis (ATCC 23246) and 7.6% of the total lipid of N. gonorrhoeae NYH 002. Hydrocarbons, triglycerides, free fatty acids, coenzyme Q, diglycerides, and free hydroxy fatty acids were identified in the neutral lipid fraction of both species. The three strains of N. gonorrhoeae, sensitive, intermediate, and resistant to penicillin, exhibited no significant difference in the composition or metabolism of phospholipid.

Cultivation of type 1 N. Gonorrhoeae in liquid media

The effect of CO2 concentration on the growth and colonial stability of Type 1 Neisseria gonorrhoeae has been investigated. Carbon dioxide at a concentration of 16 per cent in air above flasks incubated in a shaker was effective in supporting growth and 100 per cent colonial stability of Types 1, 1', 2, and 4. Lower CO2 tensions increased the generation time of the strains and were less effective in maintaining the stability of virulent variants. Of several liquid media tested, Enriched Single Phase medium, which consists of Difco GC medium base (devoid of agar and starch) to which Lankford supplement and "Isovitalex" have been added, was the most suitable for use with small inocula.

A new colonial type of N. gonorrhoeae

A new variant of Neisseria gonorrhoeae, designated Type 1(1), is described. Colonies of the new type resemble those of Types 1 and 2 in physical characteristics but are granular with a slightly crenated edge and are a deeper gold in colour. The virulence of Type 1(1) in the chick embryo is in keeping with that of Types 1 and 2 but is significantly different from Types 3, 4, and 5. Type 1(1) could be maintained in the laboratory for 6 months, provided that daily selective subcultures were performed. In the absence of this, Type 1(1) reverted to Type 5. It was also possible to preserve the stability of Type 1(1) for long periods by immersion in liquid nitrogen. Pili have been demonstrated on the new type.

Attachment and ingestion of gonococci human neutrophils

Previous studies have indirectly shown that type 1 gonococci are more resistant to phagocytosis by human neutrophils (PMN) than type 3 gonococci. Using phase contrast, fluorescent, and light microscopy, we directly quantitated PMN-gonococcal interaction, with emphasis on separating ingestion from attachment. PMN monolayers were incubated on slides with type 1 or type 3 gonococcal fluorescent antibody (FA). After methanol fixation, the FA-stained gonococci associated with PMN were cointed. Since the live PMN excludes FA, the FA-stained gonococci represent only extracellular gonococci. Methylene blue was then added to the smae slide to stain both ingested and surface attached gonococci. Using these methods, intracellular and extracellular cell-associated gonococci were quantitated under varying conditions. The numbers of methylene blue-stained cell-associated gonococci that were ingested were: with normal serum, 3.7 plus or minus 4.1 per cent for type 1 and 56.2 plus or minus 3.7 percent for type 3 (P smaller than 0.001); with heat-inactivated serum, 1.0 plus or minus 3.0 per cent for type 1 and 52.6 plus or minus 3.7 per cent for type 3 (P smaller than 0.001); with higher-titer anti-gonococcal antibody serum, 4.8 plus or minus 4.3 percent for type 1 and 64.0 plus or minus 1.6 per cent for type 3 (P smaller than 0.001). Thus, most type 3 organisms were ingested, but most type 1 gonococci were bound on the PMN surface.

Inhibition of Neisseria gonorrhoeae by a factor produced by Candida albicans

When Candida albicans is present on Transgrow specimens, Neisseria gonorrhoeae is detected less frequently or else can be seen in Gram stains but cannot be readily cultured. When C. albicans and N. gonorrhoeae are grown together on Transgrow, the gonococcal cells die off much more readily than N. gonorrhoeae grown on Transgrow alone. By use of a cross-streaking technique on agar plates, it has been demonstrated that C. albicans produces a soluble substance inhibitory to N. gonorrhoeae, although not to other microorganisms tested. Preliminary results indicate that this inhibitory factor can be extracted by the use of tertiary butanol. Since approximately one-third of the Transgrow specimens with growth contains yeasts, of which C. albicans is by far the most frequent, this factor presents an important complication in the diagnosis of gonorrhea in women.

The fate of gonococci in polymorphonuclear leucocytes: an electron microscopic study of the natural disease

The fate of gonococci in polymorphonuclear leucocytes (PMN) from men with acute gonorrhoea was studied using the electronmicroscope to look for ultrastructural damage in the bacteria. Our observations demonstrate that PMN degranulate normally into vacuoles containing gonococci and that obviously degenerate forms were present in older vacuoles. Morphologically intact gonococci were common in vacuoles containing evidence of recent degranulation suggesting that these organisms had only recently been phagocytosed. When urethral pus was suspended in tissue culture medium containing 1 μg/ml penicillin there were no “persisters” presumably because the intracellular organisms were killed by the PMN. Timed in vitro experiments using a proven virulent gonococcus demonstrated that gonococci degenerate within 30 to 60 min after phagocytosis.

Human antibody response to lipopolysaccharides from Neisseria gonorrhoeae

Red cells coated with lipopolysaccharides from three different strains of Neisseria gonorhoeae have been used as antigens in a haemagglutination test for gonococcal antibodies. For each strain the geometric mean titre in sera from 50 male and 25 female patients was significantly higher than that in 50 normal controls. The most useful smooth strain, G1, picked out 84% of females and 46% of males from a group of patients known to have gonorrhoea, but only gave 2% positives among controls. The rough strain, G2, gave 10% positives in controls and 31% in patients. The results suggest that the method is worth developing further as a diagnostic test and that strain differences are important. False positives were probably due to cross-reacting antibodies.