Chapter 18

The Cocci of Medical Importance

 

Contents


1.    Critical Thinking Questions

2.    Technical Terms

3.    Search  Internet Sites on

1.    Critical Thinking Questions

Staphylococcus spp

  • Meaning of 'Staphylococcus'. Explain.

  • Where in the body is Staphylococcus usually found?

  • Define 'staph' infections

  • Describe the morphology of this bacterial genus

  • Reaction to Gram stain

  • Do old cultures stain true?

  • Does it have spores and flagella?

  • Are they encapsulated?

  • Estimated number of species

  • List the most important human pathogens belonging to this genus

  • Which one these is the most serious pathogen?

  • Which ones are harmless commensals?

  • What are the main physiological characteristics?

  • Describe colonies on agar

  • Optimum temperature of growth

  • What is the temperature range of growth?

  • Is it facultative anaerobe? Explain

  • What gases enhance its growth?

  • Behavior in high sodium chloride in medium

  • Growth and pH

  • Will it survive if dried? For how long?

  • Is it sensitive to disinfectants and antibiotics? Explain

  • Which are the two determinants of pathogenecity?

  • What is special in S. aureus regarding pathogenecity?  

  • Define coagulase and its function

  • What is fibrin and how does it work on tissue?

  • Do all staphylococci produce coagulase?

  • What is the "spreading factor"?

  • Explain how does hyaluronidase work?

  • List the main toxins of Staphylococcus aureus

  • What are hemolysins?

  • Explain in detail what is the toxic shock syndrome toxin

  • Explain the action of alpha toxins  

  • Can it be isolated from fomites?

  • What is the estimated carriage rate for normal healthy adults?

  • Where in the body/

  • What circumstances predispose an individual to infection?

  • It is the 3rd most common nosocomial infection in what kind cases?

  • Define "hospital staph strain"  

  • What is an abscess?

  • Define furuncle

  • Define impetigo

  • Define carbuncle  

  • Explain what is a systemic infection by staph and give an example

  • In what organs it may occur?

  • What is staph bacteremia and why does it account for a high mortality rate in hospitals?

  • Would it attack or reach the heart and cause death?

  • Would it attack the meninges?

  • List the disorders caused by staph toxins

  • Would it cause food poisoning? How?

  • How would you deactivate a staph enterotoxin from food?  

  • Do humans have a well develop resistance to S. aureus? If yes, why?

  • What is the role of phagocytic response by neutrophils and macrophages against staph?  

  • When do staphylococci react negatively to coagulase?

  • Is this group clinically insignificant?

  • Relation of coagulase -ve to nosocomial infections in the USA

  • What is the habitat of S. epidermidis?

  • What is the habitat of S. saprophyticus?

  • Which one causes urinary infections in young women?  

  • Sources for clinical staph samples

  • Why do these cultures grow on blood agar?

  • Explain the catalase test and how does it help in the id of staph species

  • Why the coagulase test is so important?  

  • Main clinical concern in dealing with staphylococci

  • What is the proportion of S. aureus that produce penicillase?

  • Explain the importance of the S. aureus strain termed MRSA

  • Where do most outbreaks of staph infections occur?  

  • Has immunizations with toxoids been successful?

  • Is there any type of current vaccine?  

  • Explain why people carrying staph nasally be barred from operating and delivery rooms

  • What would be good precautions in hospitals to avoid staph infections?  

Streptococcus spp

  • Explain where Streptococcus is usually found in nature

  • How do they look?

  • Are they found in pairs?

  • Do they have flagella and produce spores?

  • Are they facultative anaerobes? Explain

  • Type of reaction with catalase

  • Are they capable of fermentation?

  • Describe or draw a streptococcal bacteria

  • Why do they survive in the presence of oxygen?

  • What type of media do they require for growth?

  • Are they resistant to heat, desiccation and disinfection?

  • Do they develop drug resistance? 

  • Explain how the streptococci are classified. Number of groups.

  • What are the molecular basis of classification. Explain and list the molecules.

  • Be sure to understand what is the viridans streptococci

  • What is the most serious human pathogen of this genus?

  • Define this particular bacterial species

  • Role of streptococcal lipotechoid acid in skin and pharynx

  • What is the M-protein? Explain its role. 

  • Explain what are streptolysins

  • Types of streptolysins

  • What is a pyrogenic toxin?

  • List some extracellular toxins of group A streptococci 

  • Main reservoir of S. pyogenes

  • Percent of the population carrying virulent strains

  • Factors accounting for infection by streptococci

  • List some skin infections caused by virulent streptococci

  • List a systemic infection caused by virulent streptococci

  • List some laboratory techniques used in the identification of pathogenic streptococci

  • Why the C-carbohydrate of group A is important in these tests?

  • Reaction on blood agar plates 

  • What kind of treatment is usually administer to control streptococci?

  • Do patients with group A infection by streptococci need to be isolated?

  • Do these cocci produce capsule?

  • What is the viridans group?

  • What are the most numerous and widespread residents of the oral cavity?

  • Where else are streptococci found?

  • What species of Strepcoccus are alpha hemolytic?

  • Are viridans streptococci invasive? If not, how do they infect and where?

  • What is the most serious complication caused in humans by viridans

  • Do S. mutans and S. sanguis produce slime layers?

  • Chemical composition of these slime layers

  • Explain the clinical importance of S. pneumoniae

  • Who are particularly susceptible to pneumonia?

  • Most streptococcal infections can be cured with what antibiotic?

  • What % of people carry S. pneumoniae as part of their normal flora?

  • What is otitis media and its causative agent?

  • Explain the Quellung reaction

  • What are Pneumovax and Pnu-immune?

  • Length of duration of vaccines in 60-70% of those vaccinated

Neisseria spp.

  • What is the habitat of these bacteria?

  • List three genera

  • Which one is of greatest medical importance?

  • Explain the cellular morphology of Neisseria

  • Any flagella or spores/

  • Gram reaction is + or -ve?

  • Do they have pili?

  • Do they have an outer cell membrane?

  • Do they have techoid and lipotechoid acids on their cell wall?

  • Is Neisseria a strict parasite?

  • Oxygen requirements

  • List two major enzymes produced by Neisseria

  • Explain type of media in which these bacteria thrive

  • Do they require higher concentration of CO2?

  • List two virulence factors of N. gonorrhoeae

  • What inactivates IgA?

  • How many cases of gonorrhoeae are reported in USA every year?

  • What is the estimated range of infectious dose?

  • Portals of entry for the bacteria in the human body

  • Explain symptoms of gonorrhoeae in both males and females

  • Explain salpingitis  

  • What is meningococcal disease?

  • Causative agent of meningococcal disease

  • List the most important factors of meningococcal invasiveness

  • What do toxins of N. meningitidis cause in humans?

    •  

2.    Technical Terms

  • alpha toxin

  • alpha-hemolysis

  • beta-hemolysis

  • C-carbohydrate antigens

  • carbuncle

  • CNS

  • coagulase

  • CPS

  • enterotoxin

  • enterotoxin

  • erysipela

  • erythrogenic toxin

  • fibrin

  • furuncle

  • hemolysin

  • hemolysis

  • hyaluronic acid

  • impetigo

  • leukocidin

  • M-protein fimbriae

  • MRSA

  • otitis media

  • pili

  • pyoderma

  • pyrogenic toxin

  • quinolones

  • spreading factor

  • SSSS toxin

  • staphylococcal bacteremia

  • staphylokinase

  • streptococcal impetigo

  • streptokinase

  • streptolysins

  • vancomycin

  • viridans streptococci

  • virulence
     

3.    Search Internet Sites

Staphylococcus aureus

Streptococcus pyogenes

Neisseria gonorrhoeae

Antibiotic resistance