Chair of Microbiology, Virology, and Immunology Pathogenic cocci Staphylococci Classification. Staphylococci are included in the Firmicutes Bacteria, family Micrococcaceae, genus Staphylococcus. According to the contemporary classification, staphylococci are subdivided into more then 30 species. Among them: S. aureus, S. epidermidis, and S. saprophyticus, S. haemolyticus, S. capitis, S. hominis, S. warneri, S. xylosus etc. Morphology. Staphylococci are spherical in shape, 0.8-1 mcm in diameter, and form irregular clusters resembling bunches of grapes. In smears from cultures and pus the organisms occur in short chains, in pairs, or as single cocci. Large spherical (Lforms) or very small (G-forms) and even filterable forms may be seen in cultures which have been subjected to various physical, chemical, and biological (antibiotics) factors. Electron micrograph showing Staphylococcus aureus morphology. Staphylococci are Gram-positive organisms which possess no flagella and do not form spores. Cultivation. Staphylococci are facultative-anaerobes. They grow well on ordinary nutrient media with a pH of 7.2-7.4 at a temperature of 37 п‚°C but do not grow at temperatures below 10 п‚°C and above 45 п‚°C. At room temperature with adequate aeration and subdued light вЂ“ the organisms produce golden, white, lemon-yellow, and other pigments known as lipochromes. These pigments do not dissolve in water but are soluble in ether, benzene, acetone, chloroform, and alcohol. Cultivation. On meat peptone agar Staphylococci produce well defined colonies with smooth edges, measuring from 1-2 to 2.5 mm in diameter. Growth of Staphylococci in meat-peptone broth produces diffuse opacity throughout the medium and, subsequently, a precipitate. In some cases when there is sufficient aeration, the organisms form a pellicle on the surface of the broth. Staphylococci grow well on potatoes and coagulated serum. After 24-48 hours of incubation there is usually abundant growth along the inoculation stab and liquefaction of gelatin media. On the fourth or fifth day the gelatin medium resembles a funnel filled with fluid. On blood agar pathogenic Staphylococci cause haemolysis of the erythrocytes. Antigenic structure. Polysaccharide A was extracted from pathogenic strains isolated from patients with septicaemia, furunculosis, osteomyelitis, and acute conjunctivitis, etc. Polysaccharide B is found in avirulent, non-pathogenic strains. Polysaccharides A and B differ not only in their serological reactions but also in their chemical structures. Antigen C, containing a specific polysaccharide, has been recently isolated. The Virulence factors of Staphylococcus aureus Pathogenesis and diseases in man. Staphylococci enter the body through the skin and mucous membranes. When they overcome the lymphatic barrier and penetrate the blood, staphylococcal septicaemia sets in. Both the exotoxins and the bacterial cells play an important role in pathogenesis of diseases caused by these organisms. Consequently, staphylococcal diseases should be regarded as toxinfections. The development of staphylococcal diseases is also influenced by the resulting allergy which in many cases is the cause of severe clinical forms of staphylococcal infections which do not succumb to treatment. Pathogenesis and diseases May cause infection if the skin or mucous membranes are broken or damaged. Staphylococci are responsible for a number of local lesions in humans: hidradenitis, abscess, paronychia, blepharitis, furuncle, carbuncle, periostitis, osteomyelitis, folliculitis, sycosis, dermatitis, eczema, chronic pyodermia, peritonitis, meningitis, appendicitis, and cholecystitis. Staphylococcus aureus is considered the most pathogenic species, causing abscesses, boils, carbuncles, acne, impetego, and less commonly, pneumonia, osteomyelitis, endocarditis, cystitis, pyelonephritis, and food poisoning. Diabetes mellitus, avitaminosis, alimentary dystrophy, excess perspiration, minor occupational skin abrasions, as well as skin irritation caused by chemical substances, are some examples of the conditions conducive to the formation of pyogenic lesions of the skin and furunculosis. Pathogenesis and diseases In some cases staphylococci may give rise to secondary infection in individuals suffering from smallpox, influenza, and wounds, as well as postoperative suppurations. Staphylococcal sepsis and staphylococcal pneumonia in children are particularly severe diseases. Ingestion of foodstuffs (cheese, curds, milk, rich cakes and pastry, ice cream, etc.) contaminated with pathogenic staphylococci may result in food poisoning. Staphylococci play an essential part in mixed infections, and are found together with streptococci in cases of wound infections, diphtheria, tuberculosis, actinomycosis, and angina. Pathogenesis and diseases The wide use of antibacterial agents, antibiotics in particular, led to considerable changes in the severity and degree of the spread of staphylococcal lesions. Growth in the incidence of diseases and intrahospital infections in obstetrical, surgical and children's in-patient institutions, intensive spread of the causative agent, and increase in the number of carriers among the medical staff and population have been noted in all countries of the world. Intrauterine and extrauterine contamination of children with staphylococci has been registered, with the development of vesiculopustular staphyloderma, pemphigus, infiltrates, abscesses, conjunctivitis, nasopharyngitis, otitis, pneumonia, and other diseases. Immunity. The tendency to run a chronic flaccid course or relapse is regarded as a characteristic symptom of staphylococcal infections. This peculiarity gives a basis for concluding that postinfectional immunity following staphylococcal diseases is of low grade and short duration. Immunity acquired after staphylococcal diseases is due to phagocytosis and the presence of antibodies (antitoxins, precipitins, opsonins, and agglutinins). Laboratory diagnosis. Test material may be obtained from pus, mucous membrane discharge, sputum, urine, blood, foodstuffs (cheese, curds, milk, pastry, cakes, cream, etc.), vomit, lavage fluids, and faeces. The material is examined for the presence of pathogenic staphylococci. Special rules are observed when collecting the material since non-pathogenic strains are widespread in nature. Identification of Gram Positive Cocci: Staphylococcus пЃ° пЃ° пЃ° пЃ° Contains both pathogenic and nonpathogenic organisms Do not produce endospores, but are resistant to drying (desiccation) Found routinely on the surface of the skin Three major species: 1. 2. 3. пЃ° пЃ° Staphylococcus aureus Staphylococcus epidermidis Staphylococcus saprophyticus The three species can be distinguished from each other by various biochemical tests. In this lab we will perform some of these tests and observe the results. Main characteristics S. aureus S. epider- S. sapromidis phyticus Plasmacoagulase + вЂ” вЂ” Phosphatase + + вЂ” Reductase + + вЂ” Protein A, superficial antigen + вЂ” вЂ” Mannitol + вЂ” + Trehalose + вЂ” + Production of alpha-toxin + вЂ“ вЂ“ Resistance to novobiocin S S R Coagulase Test Novobiocin Susceptibility пЃ° пЃ° A zone of growth inhibition 17 mm or less in diameter indicates resistance (R) to Novobiocin. If the zone is greater than 11 mm the organism is susceptible (S) to Novobiocin. Treatment. Staphylococcal diseases are treated with antibiotics (penicillin, phenoxymethyl penicillin, tetracycline, gramicidin, etc.), sulphonamides (norsulphazol, sulphazol, etc.), and antistaphylococcal gamma-globulin. Prophylaxis. The general precautionary measures include: hygiene in working and everyday-life conditions, treatment of vitamin deficiency, prevention of traumatism and excess perspiration, observance of rules of hygiene in maternity hospitals, surgical departments, children's institutions, industrial plants and enterprises, particularly canneries, observance of personal hygiene and frequent washing of hands in warm water with soap. Routine disinfection of hospital premises (surgical departments, maternity wards) and bacteriological examination of the personnel for carriers of pathogenic staphylococci resistant to antibiotics are also necessary. To prevent pyoderma protective ointments and pastes are used at industrial enterprises. In some cases specific prophylaxis by means of immunization with the staphylococcal anatoxin may be recommended for individuals subject to injury or infection with antibiotic-resistant staphylococci. Streptococci Morphology. Streptococci are spherical in shape, 0.6 to 1 mem in diameter, and form chains. They are non-motile (although motile forms are encountered), do not form spores and are Gram-positive. Some strains are capsulated. In smears from cultures grown on solid media the streptococci are usually present in pairs or in short chains, while in smears from broth cultures they form long chains or clusters. Cultivation. Streptococci are facultatively aerobic, and there are also anaerobic species. The optimal temperature for growth is 37В° C, and no growth occurs beyond the limits of 20-40В° C for enterococci the limits are 10-45 п‚°C). The organisms show poor growth on ordinary meat-peptone agar, and grow well on sugar, blood, serum and ascitic agar and broth, when the pH of the media is 7.2-7.6. On solid media they produce small (0.5-1.0 mm in diameter), translucent, grey or greyish-white, and granular colonies with poorly defined margins. On sugar broth medium growth is in the form of fine-granular precipitates on the walls and at the bottom of the tube and only rarely does the broth become turbid. Cultivation. Some streptococcal strains cause haemolysis on blood agar, others produce a green coloration surrounding the colony 1-2 mm in diameter as result a conversion of haemoglobin into methaemoglobin, while others do not cause any change in the erythrocytes. Types of hemolysis The Beta hemolysis: The alpha hemolysis: The Gamma ( non hemolytic) Fermentative properties. Streptococci are nonproteolytic, do not liquefy gelatin, and do not reduce nitrates to nitrites. They coagulate milk, dissolve fibrin, ferment glucose, maltose, lactose, saccharose, mannitol (not always constantly), and break down salicin and trehalose, with acid formation. Classification. By means of the precipitation reaction founded on the detection of group specific carbohydrates, streptococci are subdivided into groups which are designated by capital letters from A to H and from K to T. Five out of the 21 known Streptococcal species cannot be related to any antigenic group. Nine species are of interest for medical microbiology; The haemolytic streptococci, recovered from sick human beings, were subdivided by F. Griffith into 51 serovars. He attributed 47 serovars to group A, serovars 7, 20, and 21 to group C, and serovar 16 to group G. Pathogenesis and diseases in man. The pathogenesis of streptococcal infections is brought about by the effect of the exotoxin and the-bacterial cells.The reactivity of the infected body and its previous resistance play an important part in the origin and development of streptococcal diseases. Such diseases as endocarditis, polyarthritis, highmoritis, chronic tonsillitis, and erysipelas are associated with abnormal body reactivity, hyperergia. This condition may persist for a long period of time and serve as the main factor for the development of chronic streptococcal diseases. With an exogenous mode of infection streptococci invade the human body from without (from sick people, and animals, various contaminated objects and foodstuffs). They gain access through injured skin and mucous membranes or enter the intestine with the food. Streptococci are mainly spread by the air droplet route. When the natural body resistance is weakened, conditionally pathogenic streptococci normally present in the human body become pathogenic. Penetrating deep into the tissues they produce local pyogenic inflammations, such as streptoderma, abscesses, phlegmons, lymphadenitis, lymphangitis, cystitis, pyelitis, cholecystitis, and peritonitis. Erysipelas (inflammation of the superficial lymphatic vessels) and tonsillitis (inflammation of the pharyngeal and tonsillar mucosa) are among the diseases caused by streptococci. Invading the blood, streptococci produce a serious septic condition. They are more commonly the cause of puerperal sepsis than other bacteria. Streptococci may cause secondary infections in patients with diphtheria, smallpox, whooping cough, measles, and other diseases. Chronic tonsillitis is attributed to the viridans streptococci and adenoviruses. Contamination of wounds with streptococci during war results in wound suppurations, abscess formation, phlegmons, and traumatic sepsis. Role of Streptococcus in the Aetiology of Scarlet Fever Scarlet fever has long been known as a widespread disease but at the present time its aetiology has not yet been ascertained. Four different theories were proposed: streptococcal, allergic, viral, and combined (viral-streptococcal). Most scientists and medical practitioners favoured the streptococcal theory. It is assumed that scarlet fever is caused by group A betahaemolytic streptococci which possess M-antigen and produce erythrogenic exotoxin. People become infected by the air droplet route. Sic k people, convalescents, and carriers of the causative agent of scarlet fever are all sources of infection. The disease is most commonly encountered in children from 1 to 8 years of age. The causative agent sometimes enters the body through wounds on the skin and mucous membranes of the genitalia. This form of scarlet fever is known as extrabuccal or extrapharyngeal (traumatic, combustion, surgical, and puerperal). Certain objects (e. g. utensils, toys, books, etc.) as well as foodstuffs (e. g. milk), contaminated by adult carriers, may also be sources of infection. Of great importance in the epidemiology of scarlet fever are the patients with atypical, unrecognizable forms of the disease. In its initial stage scarlet fever is chiefly characterized by intoxication, while in the second stage it is accompanied by septic and allergic conditions. Immunity. Immunity acquired after streptococcal infections is ofa low grade and short duration. Relapses of erysipelas, fre quent tonsilitis, dermatitis, periostitis, and osteomyelitis occur as a result of sensitization of the body. This is attributed to low immunogenic activity and high allergen content of the streptococci, as well as to the presence of numerous types of the organisms against which no cross immunity is produced. Immunity following streptococcal infections is of an antiinfectious nature. It is associated with antitoxic and antibacterial factors. The antitoxins neutralize the streptococcal toxin and together with the opsonins facilitate phagocytosis. Laboratory diagnosis. Test material is obtained from the pus of wounds, inflammatory exudate. tonsillar swabs, blood, urine, and foodstuffs. Procedures are the same as for staphylococcal infections. Tests include microscopy of pus smears, inoculation of test material onto blood agar plates, isolation of the pure culture and its identification. Blood is sown on sugar broth if sepsis is suspected. Virulence is tested on rabbits by an intracutaneous injection of 200-400 million microbial cells. Toxicity is determined by injecting them intracutaneously with broth culture filtrate. The group and type of the isolated streptococcus and its resistance to the medicaments used are also determined. In endocarditis there are very few organisms present in the blood in which they appear periodically. For this reason blood in large volumes (20-50 ml) is inoculated into vials containing sugar broth. If possible, the blood should be collected while the patient has a high temperature. In patients with chronic sepsis an examination of the centrifuged urine precipitate and isolation of the organism in pure culture are recommended. Besides, the group and type of the isolated streptococcus are identified by means of fluorescent antibodies. Serological methods are also applied to determine the increase in the titre of antibodies, namely streptolysins O and antihyaluronidase. Treatment. Usually penicillin is used. For penicillinresistant strains,and when penicillin is contraindicated, streptomycin, and erythromycin are required. Vaccine therapy (autovaccines and polyvalent vaccines) and phage therapy are recommended in chronic conditions. In some countries diseases caused by beta-haemolytic streptococci of groups A, C, G, and H and by alphastreptococci (endocarditis) are treated with anti-infectious (antitoxic and antibacterial) streptococcal sera together with antibiotics and sulphonamides. Prophylaxis. Streptococcal infections are prevented by the practice of general hygienic measures at factories, children's institutions, maternity hospitals, and surgical departments, in food production, agricultural work, and everyday life. Maintaining appropriate sanitary levels of living and working condi- tions, raising the cultural level of the population, and checking personal hygiene are of great importance. Since streptococci and the macro-organism share antigenic structures in common and because streptococci are marked by weak immunogenic ability and there are a great number of types among them which do not possess the property of producing cross immunity, specific prophylaxis of streptococcal diseases has not been elaborated. Vaccines prepared from M-protein fractions of streptococci are being studied. Meningococci The meningococcus (Neisseria meningitidis) was isolated from the cerebrospinal fluid of patients with meningitis and studied in detail in 1887 by A. Weichselbaum. At present the organism is classified in the genus Neisseria, family Neisseriaceae Morphology. The meningococcus is a coccus 0.6-1 mcm in diameter, resembling a coffee bean, and is found in pairs (fig. 1). The organism is Gram-negative. As distinct from pneumococci, meningococci are joined longitudinally by their concave edges while their external sides are convex. Spores, capsules and flagella are not formed. In pure cultures meningococci occur as tetrads (in fours) and in pus they are usually found within and less frequently outside the leukocytes. The G+C content in DNA ranges from 50.5 to 51.3 per cent. In culture smears, small or very large cocci are seen singly, in pairs, or in fours. Meningococci may vary not only in shape but also in their Gram reaction. Gram-positive diplococci appear among the Gram-negative cells in smears. Cultivation. The meningococcus is an aerobe or facultative anaerobe and does not grow on common media. It grows readily at pH 7.2-7.4 on media to which serum or ascitic fluid has been added. Optimum temperature for growth is 36-37 п‚°C and there is no growth at 22В° C. Microbiologists use a peptone-blood base medium in a moist chamber containing 5-10 % CO2. All media must be warmed to 37 degrees prior to inoculation as the organism is extremely susceptible to temperatures above or below 37 degrees. On solid media the organisms form fine transparent colonies measuring 2-3 mm in diameter. In serum broth they produce turbidity and a precipitate at the bottom of the test tube, and after 3-4 day's, a pellicle is formed on the surface of the medium. Meningococci can be adapted to simple media by repeated subculture on media with a gradual change from the optimum protein concentration to media containing a minimal concentration of proteins. Fermentative properties. Meningococci do not liquefy gelatin, cause no change in milk, and ferment glucose and maltose, with acid formation. Toxin production. Meningococci produce toxic substances which possess properties of exo- and endotoxins. Disintegration of bacterial cells leads to the release of a highly toxic endotoxin. Meningococci readily undergo autolysis which is accompanied by accumulation of toxins in the medium. The meningococcal toxin is obtained by treating the bacterial cells with distilled water, or 10 N solution of soda, by heat autolysis, by exposure to ultraviolet rays. Major toxin of N. meningitidis is its lipooligosaccharide, LOS, and its mechanism is endotoxic. The other important determinant of virulence of N. meningitidis is its antiphagocytic polysaccharide capsule. Fimbriae are factor of virulence Antigenic structure and classification. Meningococci were found to contain three fractions: carbohydrate (C) which is common to all meningococci, protein (P) which is found in gonococci and type III S. pneumoniae, and a third fraction with which the specificity of meningococci is associated. According to the International Classification Twelve groups of meningococci are distinguished, groups A, B, C, D, H, I, K, L, X, Y, Z, 29E, and W135. Types A, B, C, Y, and W135 are dominant. The organisms are characterized by intraspecies variability. A change of types takes place at certain times. Pathogenesis and diseases in man. People suffering from meningococcal infection and carriers are sources of diseases. The infection is transmitted by the air-droplet route. The causative agent is localized primarily in the nasopharynx. From here it invades the lymph vessels and blood and causes the development of bacteriemia. Then as a result of metastasis the meningococci pass into the meninges and produce acute pyogenic inflammation in the membranes of the brain and spinal cord (nasopharyngitis, meningococcaemia, meningitis). The disease usually arises suddenly with high temperature, vomiting, rigidity of the occipital muscles, severe headache, and increased skin sensitivity. Later paresis of the cranial nerves develops due to an increase in the intracranial pressure. Dilatation of the pupils, disturbances of accommodation, as well as other symptoms appear. A large number of leukocytes are present in the cerebrospinal fluid, and the latter after puncture escapes with a spurt because of the high pressure. In some cases meningococcal sepsis develops. In such conditions the organisms are found in the blood, joints, and lungs. The disease mainly attacks children from 1 to 5 years of age. Before the use of antibiotics and sulphonamides the death rate was very high (30-60 per cent). The population density plays an important part in the spread of meningitis. During epidemic outbreaks there is a large number of carriers for every individual affected by the disease. In non-epidemic periods the carrier rate increases in the spring and autumn. Body resistance and the amount and virulence of the causative agent are significant. Depending on these factors, the spread of infection is either sporadic or epidemic. Meningitis can also be caused by other pathogenic microbes (streptococci, E. coli, staphylococci, bacteria of influenza, mycobacteria of tuberculosis, and certain viruses). These organisms, however, cause sporadic outbreaks of the disease, while meningococci may cause epidemic meningitis. Immunity. There is a well-developed natural immunity in humans. Acquired immunity is obtained not only as a result of the disease but also as the result of natural immunity developed during the meningococcal carrier state. In the course of the disease agglutinins, precipitins, opsonins, and complement-fixing antibodies are produced. Recurring infections are rare. Laboratory diagnosis. Specimens of cerebrospinal fluid, nasopharyngeal discharge, blood, and organs obtained at autopsy are used for examination. The following methods of investigation are employed: (1) microscopic examination of cerebrospinal fluid precipitate; (2) inoculation of this precipitate, blood or nasopharyngeal discharge into ascitic broth, blood agar, or ascitic agar; identification of the isolated cultures by their fermentative and serologic properties; differentiation of meningococci from the catarrhal micrococcus (Branhamella catarrhalis) and saprophytes normally present in the throat. The meningococcus ferments glucose and maltose, whereas Branhamella catarrhalis does not ferment carbohydrates, and Neisseria sicca ferments glucose, levulose, and maltose; (3) performance of the precipitin reaction with the cerebrospinal fluid. Treatment. Antibiotics (penicillin, oxytetracycline, etc.) and sulphonamides (streptocid, methylsulphazine) are prescribed. Prophylaxis is ensured by general sanitary procedures and epidemic control measures (early diagnosis, transference of patients to hospital), appropriate sanitary measures in relation to carriers, quarantine in children's institutions. Observance of hygiene in factories, institutions public premises, and lodgings, and prevention of crowded condition are also obligatory. An antimeningococcal vaccine derived from the C/B serogroup is now under test. It contains specific polysaccharides. The incidence of meningitis has grown recently. The disease follows a severe course and sometimes terminates in death. Gonococci The causative agent of gonorrhoea and blennorrhoea (Neisseria gonorrhoeae) was discovered in 1879 by A. Neisser in suppurative discharges. In 1885 E. Bumm isolated a pure culture of the organism and studied it in detail. Gonococci belong to the genus Neisseria, family Neisseriaceae. Morphology. Gonococci are morphologically similar to meningococci. The organism is a paired, bean-shaped coccus, measuring 0.6-1 mcm in diameter. It is Gramnegative and occurs inside and outside of the cells. Neither spores nor flagella are formed. Under the electron microscope a cell wall, 0.3-0.4 mcm in thickness, surrounding the gonococci is visible. The G+C content in DNA is 49.5 to 49.6 per cent. Pleomorphism of the gonococci is a characteristic property. They readily change their form under the effect of medicines, losing their typical shape, and growing larger, sometimes turning Gram-positive, and are found outside the cells. In chronic forms of the disease autolysis of the gonococci takes place with formation of variant types (Asch types). Usually gonococcal cells varying in size and shape are formed. The tendency toward morphological variability among the gonococci should be taken into account in laboratory diagnosis. L-forms occur under the effect of penicillin. Cultivation. The gonococcus is an aerobe or facultative anaerobe which does not grow on ordinary media, but can be cultivated readily on media containing human proteins (blood, serum, ascitic fluid) when the pH of the media is in the range of 7.2-7.6. The optimum temperature for growth is 37В° C, and the organism does not grow at 25 and 42В° C. It also requires an adequate degree of humidity. Ascitic agar, ascitic broth, and egg-yolk medium are the most suitable media. On solid media gonococci produce transparent, circular colonies, 1-3 mm in diameter. Cultures of gonococci form a pellicle in ascitic broth, which in a few days settles at the bottom of the test tube. Fermentative properties. The gonococcus possesses low biochemical activity and no proteolytic activity. It ferments only glucose, with acid formation. Toxin production. The gonococci do not produce soluble toxin (exotoxin) An endotoxin is released as a result of disintegration of the bacterial cells. This endotoxin is also toxic for experimental animals. Antigenic structure and classification. The antigenic structure of gonococci is associated with the protein (Oantigen) and polysaccharide (K-antigen) fractions. No group specific or international types of gonococci have been revealed. Gonococci and meningococci share some antigens in common. Surface components of N. gonorrhoeae that may play a role in virulence Designatio n Location Contribution Pile Major fimbrial protein Initial cells P.II (Opa) Outer membrane protein Contributes to invasion P.I (Por) Outer membrane porin May prevent phagolysosome formation in neutrophils and/or reduce oxidative burst LOS Outer membrane lipooligosaccharide Elicits inflammatory response, triggers release of TNF P.III (Rmp) Outer membrane protein Elicits formation of ineffective antibodies that block that block bactercidal antibodies against P.I and LOS Tbp1 Tbp2 Lbp binding to epithelial and Outer membrane Iron acquisition for growth Outer membrane receptor for Iron acquisition for growth receptors for transferrin Pathogenesis and diseases in man. Patients with gonorrhoea are sources of the infection. The disease is transmitted via the genital organs and by articles of domestic use (diapers, sponges, towels, etc). The causative agent enters the body via the urethral mucous membranes and, in women, via the urethra and cervix uteri. Gonorrhoea is accompanied by acute pyogenic inflammation of the urethra, cervix uteri, and glands in the lower genital tract. Often, however, the upper genito-urinary organs are also involved. Inflammations of the uterus, uterine tubes, and ovaries occur in women, vulvovaginitis occurs in girls, and inflammation of the seminal vesicles and prostata in men. The disease may assume a chronic course. From the cervix uteri the gonococci can penetrate into the rectum. Inefficient treatment leads to affections of the joints and endocardium, and to septicaemia. Gonococci and Trichomonas vaginalis are often found at the same time in sick females. The trichomonads contain (in the phagosomes) gonococci protected by membranes against the effect of therapeutic agents. Gonococcus is responsible for gonorrhoeal conjunctivitis and blennorrhea in adults and newborn infants. Immunity. The disease does not produce insusceptibility and there is no congenital immunity. Antibodies (agglutinins, precipitins, opsonins, and complement-fixing bodies) are present in patients' sera, but they do not protect the body from reinfection and recurrence of symptoms. Phagocytosis in gonorrhoea is incomplete. The phagocytic and humoral immunity produced in gonorrhoea is incapable of providing complete protection, so, in view of this fact, treatment includes measures which increase body reactivity. This is achieved by raising the patient's temperature artificially. Laboratory diagnosis. Specimens for microscopic examination are obtained from the discharge of the urethra, vagina, vulva, cervix uteri, prostate, rectal mucous membrane, and conjunctiva. The sperm and urine precipitates and filaments are also studied microscopically, Smears are stained by Gram's method and with methylene blue by Loeffler's method). Microscopy is quite frequently an unreliable diagnostic method since other Gram-negative bacteria, identical to the gonococci, may be present in the material under test. Most specific are the immunofluorescence methods (both direct and indirect). In the direct method the organisms under test are exposed to the action of fluorescent antibodies specific to gonococci. In the indirect method, the known organisms (gonococci) are treated with patient's serum. The combination of the antibody with the antigen becomes visible when fluorescent antiserum is added. Laboratory diagnosis. If diagnosis cannot be made by microscopic examination, isolation of the culture is carried out. For this purpose the test material (pus, conjunctival discharge, urine precipitate, etc.) is inoculated onto media. The Bordeux-Gengou complement-fixation reaction and the allergic test are employed in chronic and complicated cases of gonorrhea. Treatment. Patients with gonorrhoea are prescribed antibiotics (bicillin-6, ampicillin, monomycin, kanamycin) and sulphonamides of a prolonged action. Injections of polyvalent vaccine and autovaccine as well as pyrotherapy (introduction of heterologous proteins) are applied in complicated cases. Improper treatment renders the gonococci drug-resistant, and this may lead to the development of complications and to a chronic course of the disease. Prophylaxis includes systematic precautions for establishing normal conditions of everyday and family life, health education and improvement of the general cultural and hygienic standards of the population. In the control of gonorrhoea great importance is assigned to early exposure of sources of infection and contacts and to successful treatment of patients. The prevention of blennorrhea is effected by introducing one or two drops of a 2 per cent silver nitrate solution into the conjunctival sac of all newborn infants. In certain cases (in prematurely born infants) silver nitrate gives no positive result. Good results are obtained by introducing two drops of a 3 per cent penicillin solution in oil into the conjunctival sac. The gonococci are killed in 15-30 minutes. In spite of the use of effective antibiotics the incidence of gonorrhoea tends to be on the increase in all countries (Africa, America, South-Eastern Asia, Europe, etc.). The number of complications has also increased: gonococcal ophthalmia of newborn infants (blennorrhea), vulvovaginitis in children, and inflammation of the pelvic organs (salpingitis) and sterility in women. The rise in the incidence of gonorrhoea is caused by social habits (prostitution, homosexualism, etc.), inefficient registration of individuals harbouring the disease, deficient treatment, and the appearance of gonococci resistant to the drugs used.