Page 196 - Textbook of Pathology, 6th Edition

180 streptococcal complications such as RHD and acute
glomerulonephritis.
3. Group C and G streptococci are responsible for respiratory
infections.
4. Group D or Streptococcus faecalis, also called enterococci
are important in causation of urinary tract infection, bacterial
endocarditis, septicaemia etc.
5. Untypable α-haemolytic streptococci such as Streptococcus
viridans constitute the normal flora of the mouth and may
SECTION I
cause bacterial endocarditis.
6. Pneumococci or Streptococcus pneumoniae are etiologic
agents for bacterial pneumonias, meningitis and septicaemia.

CLOSTRIDIAL DISEASES
Clostridia are gram-positive spore-forming anaerobic
microorganisms found in the gastrointestinal tract of
herbivorous animals and man. These organisms may
undergo vegetative division under anaerobic conditions, and
sporulation under aerobic conditions. These spores are
passed in faeces and can survive in unfavourable conditions.
On degeneration of these microorganisms, the plasmids are
liberated which produce many toxins responsible for the
following clostridial diseases depending upon the species
(Fig. 7.6):
Figure 7.5 Diseases caused by streptococci. 1. Gas gangrene by C. perfringens
2. Tetanus by C. tetani
8. Septicaemia. Staphylococcal septicaemia may occur in 3. Botulism by C. botulinum
patients with lowered resistance or in patients having 4. Clostridial food poisoning by C. perfringens
underlying staphylococcal infections. Patients present with 5. Necrotising enterocolitis by C. perfringens.
features of bacteraemia such as shaking chills and fever
General Pathology and Basic Techniques
(Chapter 6). GAS GANGRENE. Gas gangrene is a rapidly progressive
and fatal illness in which there is myonecrosis of previously
9. Toxic shock syndrome. Toxic shock syndrome is a serious healthy skeletal muscle due to elaboration of myotoxins by
complication of staphylococcal infection characterised by some species of clostridia. In majority of cases (80-90%), the
fever, hypotension and exfoliative skin rash. The condition source of myotoxins is C. perfringens Type A; others are C.
affects young menstruating women who use tampons of novyi and C. septicum. Generally, traumatic wounds and
some brands which when kept inside the vagina cause surgical procedures are followed by contamination with
absorption of staphylococcal toxins from the vagina. clostridia and become the site of myonecrosis. The incuba-
tion period is 2 to 4 days. The most common myotoxin
STREPTOCOCCAL INFECTIONS produced by C. perfringens Type A is the alpha toxin which

Streptococci are also gram-positive cocci but unlike is a lecithinase. The prevention of gas gangrene lies in
staphylococci, they are more known for their non- debridement of damaged tissue in which the clostridia thrive.
suppurative autoimmune complications than suppurative The lesion has serosanguineous discharge with odour and
inflammatory responses. Streptococcal infections occur contains gas bubbles. There is very scanty inflammatory
throughout the world but their problems are greater in reaction at the site of gas gangrene.
underprivileged populations where antibiotics are not TETANUS. Tetanus or ‘lock jaw’ is a severe acute neuro-
instituted readily. logic syndrome caused by tetanus toxin, tetanospasmin,
The following groups and subtypes of streptococci have which is a neurotoxic exotoxin elaborated by C. tetani. The
been identified and implicated in different streptococcal spores of the microorganism present in the soil enter the body
diseases (Fig. 7.5): through a penetrating wound. In underdeveloped countries,
1. Group A or Streptococcus pyogenes, also called β-haemo- tetanus in neonates is seen due to application of soil or dung
lytic streptococci, are involved in causing upper respiratory on the umbilical stump. The degenerated microorganisms
tract infection and cutaneous infections (erysipelas). In liberate the tetanus neurotoxin which causes neuronal
addition, beta haemolytic streptococci are involved in stimulation and spasm of muscles. The incubation period of
autoimmune reactions in the form of rheumatic heart disease the disease is 1-3 weeks. The earliest manifestation is lock-
(RHD). jaw or trismus. Rigidity of muscles of the back causes
2. Group B or Streptococcus agalactiae produces infections in backward arching or opisthotonos. Death occurs due to
the newborn and is involved in non-suppurative post- spasm of respiratory and laryngeal muscles.