This document discusses diseases caused by various microorganisms including bacteria, fungi, and parasites. It provides details on staphylococcal infections including those caused by Staphylococcus aureus and the wide range of clinical manifestations. It also discusses streptococcal infections focusing on different disease-causing species and their associated diseases. Finally, it covers clostridial diseases including gas gangrene caused by Clostridium perfringens and tetanus caused by Clostridium tetani.

1. Diseases caused by bacteria, spirochaetes,
mycobacteria & FUNGI
DR. ROOPAM JAIN
PROFESSOR & HEAD,
DEPT. OF PATHOLOGY & BLOOD BANK

2. Routes of Microbial Infecton

3. Special Techniques for
Diagnosing Infectious Agents

5. Spectrum of Inflammatory
Responses to Infection

6. Classification of
Important Sexually
Transmitted
Diseases

8. Diseases caused by
bacteria, spirochaetes &
mycobacteria

11. STAPHYLOCOCCAL INFECTIONS
• gram-positive cocci
• present everywhere—in the skin, umbilicus, nasal vestibule,
stool etc.
• 3 species are pathogenic to human beings: Staph. aureus,
Staph. epidermidis and Staph. saprophyticus.
• Most staphylococcal infections are caused by Staph. aureus.
• Staphylococcal infections are among the commonest antibiotic
resistant hospital-acquired infection in surgical wounds

12. A wide variety of suppurative diseases are
caused by Staph. aureus which includes
• 1. Infections of skin
• 2. Infections of burns and surgical wounds
• 3. Infections of the upper and lower respiratory tract
• 4. Bacterial arthritis
• 5. Infection of bone (Osteomyelitis)
• 6. Bacterial endocarditis
• 7. Bacterial meningitis
• 8. Septicaemia
• 9. Toxic shock syndrome

13. STAPHYLOCOCCAL
INFECTIONS
Suppurative diseases
caused by
Staphylococcus aureus

14. STREPTOCOCCAL INFECTIONS
• gram-positive cocci
• more known for their non-suppurative autoimmune
complications than suppurative inflammatory responses.
• Streptococcal infections occur throughout the world
(underprivileged populations)

15. Implicated in different streptococcal diseases
• 1. Group A or Streptococcus pyogenes, also called b-haemolytic
streptococci - upper respiratory tract infection and cutaneous
infections (erysipelas).
• 2. Group B or Streptococcus agalactiae produces infections in the
newborn and is involved in non-suppurative poststreptococcal
complications such as RHD and acute glomerulonephritis.
• 3. Group C and G streptococci - respiratory infections.

16. Implicated in different streptococcal diseases
• 4. Group D or Streptococcus faecalis, also called enterococci are
important in causation of urinary tract infection, bacterial
endocarditis, septicaemia etc.
• 5. Untypable a-haemolytic streptococci such as Streptococcus
viridans constitute the normal flora of the mouth and may cause
bacterial endocarditis.
• 6. Pneumococci or Streptococcus pneumoniae - bacterial
pneumonias, meningitis and septicaemia

17. Diseases
caused by
streptococci

18. CLOSTRIDIAL DISEASES
• gram-positive spore-forming anaerobic microorganisms
• found in the GIT of herbivorous animals and man.
• undergo vegetative division under anaerobic conditions, and
sporulation under aerobic conditions.
• toxins responsible for the diseases:
• 1. Gas gangrene by C. perfringens
• 2. Tetanus by C. tetani
• 3. Botulism by C. botulinum
• 4. Clostridial food poisoning by C. perfringens
• 5. Necrotising enterocolitis by C. perfringens.

20. GAS GANGRENE
• rapidly progressive and fatal illness
• Myonecrosis due to elaboration of myotoxins
• In majority of cases (80-90%), the source of myotoxins is C.
perfringens Type A; others are C. novyi and C. septicum.
• Generally, traumatic wounds and surgical procedures are
followed by contamination with clostridia and become the site
of myonecrosis.
• The incubation period is 2 to 4 days.
• The most common myotoxin produced by C. perfringens Type A
is the alpha toxin which is a lecithinase.

21. • The prevention of gas gangrene lies in debridement of damaged
tissue in which the clostridia thrive.
• The lesion has serosanguineous discharge with odour and
contains gas bubbles.
• There is very scanty inflammatory reaction at the site of gas
gangrene

22. TETANUS
• ‘lock jaw’ is a severe acute neurologic syndrome
• caused by tetanus toxin, tetanospasmin, which is a neurotoxic exotoxin
elaborated by C. tetani.
• The spores of the microorganism present in the soil enter the body
through a penetrating wound.
• The degenerated microorganisms liberate the tetanus neurotoxin which
causes neuronal stimulation and spasm of muscles.
• The incubation period of the disease is 1-3 weeks.
• The earliest manifestation is lock-jaw or trismus.
• Rigidity of muscles of the back causes backward arching or opisthotonos.
• Death occurs due to spasm of respiratory and laryngeal muscles.

23. DISEASES
CAUSED BY
FUNGI

24. Diseases caused by fungi

25. MYCETOMA
• Chronic suppurative infection (limb, shoulder)
• characterised by draining sinuses (colonies of fungi or bacteria)
• Types:
 Caused by actinomyces (higher bacteria) also called
actinomycetoma comprises about 60%.
 ”
Eumycetoma caused by true fungi, Madurella mycetomatis or
Madurella grisea, comprises the remaining 40%.
• The organisms are inoculated directly from soil into bare feet,
from carrying of contaminated sacks on the shoulders, and into
the hands from infected vegetation.

26. MYCETOMA
MORPHOLOGIC FEATURES
• After several months of infection,
• The affected site, most commonly foot, is swollen -- ‘madura foot’.
• The lesions extend deeply into the subcutaneous tissues, along
the fascia and eventually invade the bones.
• They drain through sinus tracts which discharge purulent material
and black grains.
• Surrounding tissue shows granulomatous reaction.

27. Madura foot.
Brown granule lying in necrotic tissue in the discharging sinus

28. CANDIDIASIS
• an opportunistic fungal infection caused most commonly by
Candida albicans and occasionally by Candida tropicalis.
• Candida species are present as normal flora of the skin and
mucocutaneous areas, intestines and vagina.
• Various predisposing factors are: impaired immunity, prolonged
use of oral contraceptives, long-term antibiotic therapy,
corticosteroid therapy, diabetes mellitus, obesity, pregnancy etc.

29. CANDIDIASIS
MORPHOLOGIC FEATURES
• Candida produces superficial infections of the skin and
mucous membranes, or may invade deeper tissues.
1. Oral thrush
2. Candidal vaginitis
3. Cutaneous candidiasis
4. Systemic candidiasis

30. 1. Oral thrush
• Commonest form of mucocutaneous candidiasis
• Fullfledged lesions consist of creamy white
pseudomembrane composed of fungi covering the tongue,
soft palate, and buccal mucosa
• In severe cases-ulceration
2. Candidal vaginitis
• Vaginal candidiasis or monilial vaginitis is characterised
clinically by thick, yellow, curdy discharge.
• The lesions form pseudomembrane of fungi on the vaginal
mucosa.
• They are quite pruritic and may extend to involve the vulva
(vulvovaginitis) and the perineum.

31. 3. Cutaneous candidiasis
• Candidal involvement of nail folds - paronychia and colonisation in
the intertriginous areas of the skin, axilla, groin, infra- and inter-
mammary, intergluteal folds and interdigital spaces.
4. Systemic candidiasis
• Usually a terminal event
• The organisms gain entry into the body through an ulcerative
lesion on the skin and mucosa or may be introduced
• Most commonly encountered in kidneys as ascending
pyelonephritis and in heart as candidal endocarditis.

32. Candidiasis of the ulcer in the skin

33. CUTANEOUS SUPERFICIAL MYCOSIS
• Dermatophytes cause superficial mycosis of the skin, the
important examples - Microsporum, Trichophyton and
Epidermophyton.
• These superficial fungi are spread by direct contact or by
fomites and infect tissues such as the skin, hair and nails.
• Examples
”
. Tinea capitis - patchy alopecia affecting the scalp and eyebrows.
”
. Tinea barbae is acute folliculitis of the beard. ”
. Tinea corporis is dermatitis with erythematous papules.
• Diagnosis of dermatophytosis - light microscopic examination
of skin scrapings