Haemophilus influenzae is a pleomorphic, gram negative coccobacillus which is divided into two groups: unencapsulated (non-typeable) and encapsulated. Encapsulated strains of Haemophilus influenzae are further classified into 6 different serotypes (a-f) based on the presence […]
Streptococcus pneumoniae (pneumococcus) is one of the most common causes of pneumonia, septicemia, and meningitis in children and adults both in developing and developed countries. S. pneumoniae is the most common causative agent in community-acquired […]
Streptococcus pyogenes is the leading cause of uncomplicated bacterial pharyngitis and tonsillitis commonly referred to as strep throat. Acute diseases associated with Streptococcus pyogenes occur chiefly in the respiratory tract (sinusitis, otitis), bloodstream (sepsis, endocarditis, meningitis), or the skin (impetigo, cellulitis, necrotizing fasciitis, myositis}. Two […]
Neisseria is the only pathogenic gram negative cocci (precisely diplococci). Two species of Neisseria causes disease in humans; Neisseria meningitidis and Neisseria gonorrhoeae. Human beings are only known hosts of N.gonorrhoeae. Neisseria gonorrhoeae (often called gonococcus) causes […]
Capsular polysaccharides: Neisseria meningitidis strains are frequently encapsulated and 13 different capsular serogroups have been found so far. These capsular polysaccharides protect the meningococci from the action of phagocytic cells and enhance organism’s survival during […]
Streptococcus pneumoniae is a Gram positive cocci, typically lancet shaped and occurs singly, in pairs (diplococci) or in short chains. Main diseases caused by Streptococcus pneumoniae: Bacterial pneumonia: Most common bacterial cause, especially in infants and […]
Exotoxins: Definition: Toxins that are released extracellularly as the organism grows are called exotoxins. Exotoxins may travel from a focus of infection to distant part of the body and cause damage. E.g. Neurotoxin (botulinum toxin, […]
Bacterial flagella are long, thin (about 20 nm), whip like appendages that move the bacteria towards nutrients and other attractants. Flagella are free at one end and attached to the cell at the other end. Flagellum […]
Bacterial spores are highly resistant, dormant structures (i.e. no metabolic activity) formed in response to adverse environmental conditions. They help in the survival of the organisms during adverse environmental conditions; they do not have a […]
Capsule (also known as K antigen) is a major virulence factor of bacteria, e.g. all of the principal pathogens which cause pneumonia and meningitis, including Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Klebsiella pneumoniae, Escherichia coli, […]
Escherichia coli (abbreviated as E. coli) is a commensal (normal flora) of gut of humans and warm-blooded animals. Most strains of E.coli are harmless, some even benefit the hosts by producing vitamin K in the […]
Pathogenicity islands (PAIs) are large group of mobile genetic elements that are associated with pathogenicity and are located on the bacterial chromosome. The concept of PAI was founded in the late 1980s by Jörg Hacker […]
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