Let us make an in-depth study of the streptococci. The below given article will help you to learn about the following things:- 1. Morphology of Streptococci 2. Cultivation of Streptococci 3. Laboratory Serological Typing Report 4. Puerperal Infection and 5. Application to Nursing.
Contents
Streptococci:
Sore throat; Scarlet fever, Impetigo, Bacterial endocarditis, Rheumatic fever, Acute glomerulonephritis. Several species of Gram-positive cocci (i.e., pneumococci and streptococci found mostly in the throat and staphylococci predominantly found in the anterior nares) have their main habitat in the upper respiratory tract of man. Amongst these groups, there are commensals, pathogens and potential pathogens, but only the last ones affect tissues when the resistance is lowered causing bronchitis, after primary virus infection.
The pathogenic haemolytic streptococci or Lancefield group A — Streptococcus pyogenes causes acutely inflamed throat (tonsillitis, pharyngitis, septic sore throat), scarlet fever, rheumatic fever, acute glomerulonephritis.
Morphology of Streptococci:
Streptococci are spherical in shape 0.6 to 1 micron in diameter, are Gram-positive and form chains Fig. 26.1 .They are non-motile and do not form spores. Some strains are capsulated.
Cultivation of Streptococci:
Streptococci are aerobic and facultatively aerobic; some are also anaerobic species and grow well on sugar, blood, serum or ascitic agar or broth. On solid media they produce small (0.5 -1 mm in diameter) transparent, greyish white colonies. On blood agar media, Strept.
Viridans produce (partial or greenish) α-haemolysis as a result of conversion of haemoglobulin into methaemoglobulin; Strept. faecalis cause no haemolysis (i.e., y-haemoly- sis); Strept. Pyogenes produce complete β-haemolysis. On sugar broth, growth is granular on the walls and at the bottom of the tube without turbidity.
Serological Groups:
The beta type haemolytic streptococci were classified by Lancefield (discoverer) into several Lancefield groups A to U except I, J on the basis of carbohydrate antigenic substance. The Group A streptococci are always pathogenic to man and cause serious, acute human disease (scarlet fever, erysipelas, septicaemia).These are called as Strept.
Pyogenes:
Serological typing of Group A, Streptococci. Group A streptococci can be divided into some fifty or more types based on the presence of different protein (M antigen) which are differentiated by agglutination and precipitation.
Laboratory Serological Typing Report:
Strept. Pyogenes:
β – haemolysis on blood agar.
Lancefield Group A (by carbohydrate antigen substance). Serological typing A. 14 (M protein antigen substance). The knowledge of serological typing of β- haemolytic streptococci is essential for professional nurse to understand the clinical discussion and laboratory report. If streptococci infect brain, respiratory tract, peritoneum or parturient uterus, the nursing procedures can be adopted accordingly.
Strept. Viridans Infection:
Tooth abscess. Streptococci of alpha type (Strept. viridans) are found in abscess in the roots of the teeth. The symptoms of these abscesses which are not definite may be found out by dentist X-rays plates; however, the organisms and their toxins may cause severe damage to the heart valve after setting up a focus of infection.
Heart Valve Injuries:
Injured heart valves may be infected by Strept. Viridans and ultimately these organisms may cause sub acute bacterial endocarditis which is fatal. The exact mode of transmission of the organism is not yet well established, but it may, most probably, come via blood from infected teeth and tonsils, chronic sinus infection or from the intestine. The infection via blood is known as haematogenous or endogenous. In endocarditis caused by streptococci, there is inflammation of heart valve which is followed by thickening and shrinkage of heart valves causing them to leak. Arthritis may ensue if the joints are infected.
Strept.pyogenes Infection:
Strept.pyogenes produce several exotoxins.Two distinct haemolysins can be recognised; O-streptolysin which is oxygen labile and S-streptolysin which is not oxygen sensitive.These two streptomycin’s are antigenically distinct and both are toxic to animals. O-streptolysin is found in rheumatic fever.
Antibody to O-streptolysin is generally determined; in the patient blood by anti-streptolysin – O titire (ASO titre); whereas S-streptolysin is responsible for β-haemolysis in blood agar medium. Other toxins are leucocidin, fibrinolysin (streptokinase), hyaluronidase, erythrogenic toxin which produces erythema when injected intradermally and plays a role in scarlet faver.
Streptococci gain entrance through injured skin and mucous membrane or enter the intestine with the food. They may be spread by the air droplet route. When the natural body resistance is lowered down, conditionally pathogenic streptococci normally present in the human body, may become pathogenic. Penetrating deep into the tissue they produce local pyogenic inflammation — streptoderma, abscess, 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 septicaemia. They are more commonly the cause of puerperal septicaemia than other bacteria.
Streptococci may cause secondary infection in patients with diphtheria, small pox, whooping cough, measles and other diseases. Chronic tonsillitis is attributed to Strept. viridans and adenovirus. Contamination of wounds with streptococci result in wound suppurations, abscess formation and traumatic sepsis.
Cellulitis:
Cellulitis is a most dangerous condition in which skin and underlying tissues are infected and it is caused by β-haemolytic streptococci: Group A streptococci (Strepto pyogenes) causes a very severe, rapidly spreading infection with much swelling followed by general symptoms due to potent exotoxin. The infection spreads in subcutaneous lymphatic tissue. Erysipelas is another form of acute infection of skin and underlying tissues due to P type streptococci Group A. It is rapidly progressive and frequently fatal.
Like staphylococci, beta type streptococci Group A sometimes invade the blood stream causing septicaemia and are often found in infections of lungs (pneumonia and empyema), meningitis, sinusitis and mastoiditis. Beta type streptococcal infections are controlled by broad spectrum antibiotics or penicillin or erythromycin.
Rheumatic Heart Disease:
Rheumatic fever is very serious and widespread disease with resulting heart disease which often cripples, is frequently fatal and is caused by beta type streptococci Group A. The allergy to Strept.pyogenes is, most probably, the underlying cause. “Relapses in rheumatic fever can be treated with sulphonamides or antibiotics”
Puerperal Infection:
Haemolytic streptococci gain access into the uterus:
(a) From the skin or external parts of vulva that have not been properly cleansed;
(b) From the unsterile dressings or instruments;
(c) From the hands of the doctor or nurse that have not been sufficiently disinfected, especially if the doctor or nurse is a carrier of haemolytic streptococci, a common situation.
The spread of puerperal fever or erysipelas infection can be prevented by the isolation of the infected patients. The discharges, packing’s, dressings are highly infectious, so they should be discarded into the strong disinfectants or completely burnt. Clean obstetric techniques and antibiotics could prevent postpartum mortality due to streptococcal puerperal fever (child bed fever). A pregnant woman should prefer to go to hospital for delivery because of the aseptic technique available than at home. Thus, she can be protected from possible puerperal fever.
Since the open wound in the uterus, vagina and perineum of the recent post-partum patient is a very good portal of entry for streptococci, staphylococci and other microorganisms, the doctor, nurse and other personnel’s should not be allowed, until and unless they follow all aseptic techniques and observe strict sterility. If these staffs have sore noses or throats, they should be forbidden from entry into the delivery room. Besides, the staffs having infectious lesions on their body are very dangerous to other patients.
Bronchopneumonia:
It may be caused by one or variety of organisms (staphylococci, alpha, beta type haemolytic streptococci). The causative agents of bronchopneumonia are usually found in the patient’s own mouth or often gain access to the lungs by accidental inhalation of saliva and mucus or by inhalation of micro organisms found in the droplets of sputum of saliva sprayed out while talking, sneezing or coughing. It is evident that the patients likely to develop bronchopneumonia must be protected from both the bacteria in their own mouth and from vomitus.
The greatest care to prevent carrying bacteria from patient to patient is to keep the mouth clean. The nursing care adopted for lobar pneumonia should be applied for bronchopneumonia. All persons (including medical and hospital personnel) with respiratory infections should be excluded.
Scarlet fever and Septic sore throat were formerly traceable to the consumption of unpasteurized milk from cows having mastitis due to Group A streptococci introduced by infected milkers. Pasteurization destroys the streptococci. Septic sore throat and Scarlet fever are different manifestations of the same infection. Strept pyogenes forms an erythrogenic toxin that produces rash on the skin which is a common manifestation in scarlet fever.
This toxin can be detected by Dick test (Skin test). Dick test is a biological test which determines the immune status of an individual to erythrogenic toxin. A diagnostic skin test, Schultz-Charlton reaction is sometimes made by injecting into the rash of the skin-a small dose of scarlet fever antitoxin. If the rash is due to scarlet fever, it promptly fades or is blanched; the blanching reaction.
Persons immunized to the toxin will not have the rash but may still contract the infection with Group A streptococci of other type. The infection may develop without rash and, therefore, it is called by another name—Septic sore throat. Acute glomerulonephritis is associated with specific serotype or nephritogenic type of Group A streptococci.
Transmission:
Scarlet fever transmission from person to person is an excellent model of most diseases of upper respiratory tract. In scarlet fever, saliva or mucus from mouth or nose may contain streptococci; as a result patient’s hands and face may be contaminated with these streptococci; so kissing and contaminated handkerchiefs may transmit them and are very dangerous.
Convalescents released from isolation may become carriers for a longer period, spread the disease through any discharge from the nose, ears or any other parts of the body and disseminate streptococci. During epidemics in school children, cases of scarlet fever and septic sore throat in amongst school children can easily be detected by the nurses and well informed intelligent school teachers and its further spread can be prevented.
Application to Nursing:
It is well established that the discharges from the lesions with streptococci are very dangerous, as these discharges transmit streptococci to clean wounds, scratches, cuts, the post-partum mother, and possibly, to normal mucous membrane of the nose, throat and eyes.
Since pathogens fresh from the body are particularly virulent, the professional nurse should take care so that dressings from all septic wounds including those infected with staphylococci should be properly wrapped, securely fastened and burnt. Instruments and objects contaminated by the infected wounds should be well disinfected by boiling or with chemicals.
The intelligent nurse must always take into consideration the portal of entry and portal of exit, particularly in streptococcal infections (erysipelas, septic sore throat, scarlet fever and puerperal fever), e.g., the exudate from the erysipelas lesions is very dangerous; the nose and throat secretions of a septic sore throat or scarlet fever patient are highly infectious through only portal of entry.
Paper “wipes” or pieces of old linen or gauze can be used to collect all these secretions and ultimately discarded into a paper bag at the bedside. This paper bag should be discarded daily or frequently, according to necessity, after properly securing in a newspaper or it can be incinerated.
Dishes and other objects that were in contact with mouth or nose should be adequately disinfected by boiling or with chemicals. Above all, the nurse is responsible for prevention of transfer of the infection to non-professional workers in hospitals (food handlers, dish washers, servants who dispose off trash and garbage).