Major Manifestations of Infection


A knowledge of infections prevailing in the geographical locality is an essential guide to diagnosis, especially with imported infections, as is a knowledge of where and how to find the relevant organism. Enquiry should be made about contacts among family, friends and workmates. Persons following certain occupations may be exposed to infection, e.g. leptospirosis occurs in abattoir and farm workers and anthrax in handlers of hides and bone meal.

Recent surgical history may give a clue as to the origin of abscess as a cause of unexplained fever.

Residence or travel abroad raises the possibility of malaria, amoebic abscess of the liver or other exotic disease. In many infections a diagnosis can often be made on clinical features, e.g. measles or chickenpox. In others, a diagnosis may require confirmation by microbiological, immunological, haematological, histopathological or radiological investigations, see the information box.

  • A. Recognition of causative agent
  • In stained or fresh preparations, usually a smear malaria in blood slide Vibrio cholerae in stool, diphtheria in throat swab, bacilli in urine, staphylococci in pus smear, Entamoeba in rectal scrape, plague bacilli in bubo aspirate. schistosome ova in rectal snip, rickettsia in rash aspirate', fungi in skin scrapings, pneumococci in purulent sputum, spirochaetes in condylomata (dark ground microscopy). leprosy bacilli and leishmania in slit skin smear
  • By electron microscopy: viruses in stool, herpesviruses from skin
  • By histology of biopsy specimen: acid-fast bacilli in leprosy and tuberculosis, Pneumocystis in pneumonia, hepatitis 8 in liver, rabies virus in brain"
  • B. Culture of causative organism
  • From blood typhoid, brucellosis, Gram-negative septicaemia, pneumococcal pneumonia, HIV
  • From bone marrow: tuberculosis, brucellosis, leishmaniasis, histoplasmosis
  • From other body fluids, faeces or tissues: urinary tract infection, bacillary dysentery, sputum in pneumonia, liver in tuberculosis
  • A. Detection of microbial antigen
  • Meningococcal and pneumococcal disease (blood, cerebrospinal fluid, sputum, urine)
  • B. Detection of antibody of IgM class
  • Toxoplasmosis, hepatitis A, rubella, parvovirus
  • C. Demonstration of antibody
  • Rising titre: typhoid, brucellosis, HIV infection
  • Closely linked to clinical syndrome: amoebic abscess, visceral leishmaniasis
  • Screening for latent disease: syphilis, schistosomiasis, trypanosomiasis cruzi
  • D. Delayed hypersensitivity skin testing
  • Tuberculosis, histoplasmosis, leishmaniasis
  • A. Tissue biopsy
  • Characteristic histology: hepatitis, leprosy
  • Suggestive histology: tuberculosis, toxoplasmosis
  • B. Radiology
  • Association of site and pattern with infection: lobar pneumonia, renal tuberculosis, muscular cysticercosis
  • C. Scanning
  • Isotope: detection of abscess, osteomyelitis (polymorph scan)
  • Ultrasound: abscess, hydatid cyst
  • Computed tomography (CT) or magnetic resonance imaging (MRI): intracranial infection, visceral abscesses, mediastinal lymph node enlargement
* Usually performed using immunofluorescent staining.
Concepts of infection
Major manifestations of infection
Principles of management of infection
Diseases due to viruses
DNA viruses
Diseases due to chlamydiae
Diseases due to rickettsiae
Diseases due to bacteria
  • Streptococcal infections
  • Staphylococcal infections
  • Corynebacterial infections
  • Bacillus infections
  • Bordetella infections
  • Salmonella infections
  • Food poisoning
  • Dysentery
  • Other true bacterial infections
  • Mycobacterial infections
Diseases due to spirochaetes
  • Leptospira infections
  • Borrelia infections
  • Treponema infections
Diseases due to fungi (mycoses)
  • Cutaneous fungal infections
  • Subcutaneous fungal infections
  • Systemic fungal infections
Diseases due to protozoa
Diseases due to helminths
  • Trematode (fluke) infections
  • Cestode (tapeworm) infections
  • Nematode (roundworm) infections
  • Zoonotic helminth infections
Diseases due to arthropods
Sexually transmitted diseases
  • Sexually transmitted bacterial diseases
  • Sexually transmitted viral diseases
  • Miscellaneous conditions