Chapter 18: Cocci of medical importance

02/23/2025- Finished flashcard set ~X

Is Staphylococcus Gram + or -?

Gram +

Can Staphylococcus synthesize catalase? How does this differ from Streptococcus?

It can synthesize catalase. This differs from streptococcus since strep cannot synthesize catalase.

Does Staphylococcus have the tendency to be drug resistant? If so, give 2 examples of drugs it is resistant to.

It does have the tendency to be drug resistant. It can resistant to Methicillin and Vancomycin.

Is Staphylococcus part of the normal flora? If so, where? Does it always cause disease?

It is part of the normal flora- specifically of the nose, skin, gut, and vagina. It usually does not cause disease.

Does salt inhibit Staphylococcus growth? What does this make it?

no. In fact, it grows well on media that has up to 10%+ of NaCl. This makes it halotolerant.

Does Staphylococcus cause nosocomial infections?

Yes and is associated with serious nosocomial infections (especially surgery).

What does Staphylococcus being a pus forming pathogen mean?

It means that Staphylococcus is pyogenic.

Which species of Staphylococcus is the most serious medically?

Staphylococcus aureus

What areas of the body can be problematic with S. aureus?

• Skin

• Gut

• Reproductive system: TSS (Toxic shock syndrome)

• Systemic

What are some examples of exoenzymes utilized by Staphylococcus aureus?

• Coagulases- enzymes that trigger blood clotting.

• Hyaluronidase- breaks down hyaluornic acid.

• Staphylokinase- dissolves fibrin threads in blood clots.

• Lipases- Hydrolyzes host cellular membrane fats and lipids, causing lysis of host cells. It allows staph to grow on skin and in oil glands.

• Beta-Lacramases- break down penicillin and cephalosporins, making these antibiotics useless (Cell wall synthesis inhibitors).

Present in over 90% of strains.

How does bacterium free itself from clots?

Through the use of Staphylokinase.

What are some of the toxins produced by S.aureus?

• Leukocidin- Disrupts the plasma membrane of leukocytes and macrophages by attacking the phospholipids in the cell membrane.

• Hemolysins- Destroy RBCs. (red blood cells)

• Exfoliative toxic (A,B)

• Enterotoxins

Are the toxins produced by S. aureus endotoxins or exotoxins?

Exotoxins. We know it is exotoxins because gram + can only produce exotoxins, unlike Gram - bacteria who can produce both endotoxins (lipid A) and exotoxins.

What is folliculitis? What type of flora causes this?

Infection of the hair follicle (or skin gland). Endogenous flora.

Does folliculitis always stay in the follicle or gland?

Yes because the infection is localized and not systemic.

What are the dangers of untreated boils (furuncles)?

it allows folliculitis to progress into surrounding tissue causing a tender abscess or pustule.

What skin infection can also be caused by strep and is very contagious and spreads from scratching? Which is more common?

Impetigo. High contagious and common among preschool children and school age children.

What does SSSS stand for?

Staphylococcal Scalded Skin Syndrome. Causes epidermis to peel off exposing reddened area beneath (dermis).

What strain of aureus is required to cause SSSS?

A certain type of strain of S. aureus that carries the plasmid for exfoliative toxin.

What occurs to cause skin to peel off in SSSS?

Epidermolytic toxins (A&B) produced by certain S. aureus strains cause the epidermis to “unstick” by acting on desmoglein (desmosome).

Is abnormally high growth of an opportunistic bacteria in the GI tract considered an infection or an intoxication?

intoxication

What is the name of the toxin commonly seen in GI tract intoxication? Is this an exo or endotoxin?

Enterotoxin. It is considered a exotoxin and is typically produced by gram + bacteria.

What is the problem with ingesting enterotoxins or bacteria who produce it? Is this problem common? Does the patient commonly require hospitalization?

The problem is that the enterotoxins act on the intestinal lining and nerves. This is one of the more common causes of food poisoning. It usually resolves on it’s own and does not require hospitalization.

What is TSS and some of its SN/SX?

Toxic Shock Syndrome. High fever, vomiting, diarrhea, “sunburn” -like rash (scarlatiniform), sore throat, muscle aches, multisystem dysfunction (kidney and liver failure).

Are there only menstrual related cases of TSS?

there are both menstrual and non-menstrual cases.

Does TSS only affect females? What product used increases the risk of TSS?

TSS affects both females and males through C-sections, wound infections, & surgical wound infections. Females are more commonly affected however. Products like cotton packing used in tampons for menstruating females can increase the risk of TSS.

How do systemic infections usually spread?

usually spread from a skin lesion. Involves bacteria from endogenous flora. not common in healthy individuals.

What is Bacteremia? What causes it and who is at more risk for it?

Small amounts of bacteria found in the blood. Can be caused by:

• Dental or medical procedures

• Injection of recreational drugs

• certain bacterial infections (pneumonia, meningitis, UTI)

• From intestine

Immunocompromised individuals are at higher risk.

What is Septicemia? What causes it and what are some symptoms?

Large amounts of bacteria with multiplication happening in the blood. causes include UTI, kidney infections, lung infections, and abdominal infections. Symptoms include:

• Fever, shivering, or feeling very cold (low body temp)

• Low blood pressure

• elevated heart rate

• shortness of breath/rapid breathing

• confusion

• edema

• blood clots blocking blood flow

What types of samples are collected to isolate S. aureus?

• Pus

• Tissue exudates

• Sputum

• Urine

• Blood testing

• Coagulase test or MSA (for pathogenic species)

What is an easy way of testing to differentiate between Staphylococcus vs Streptococcus?

Perform a gram stain using a broth. Staph will look like irregular clusters of cocci and step will look like chains of cocci under the microscope.

A catalase test may be performed on a sample to test for Strep.

Describe Streptococcus and its characteristics.

• Gram +

• Catalase negative

• Non-spore forming

• Non-motile

• Facultative anaerobes

• Group A&B are most important (grouped by Rebecca Lancefield)

Describe alpha hemolytic, beta hemolytic, and Gamma hemolytic Streptococcus.

• Alpha hemolytic- Partial hemolysis

• Beta hemolytic- Complete hemolysis (most serious pathogen)

• Gamma hemolytic- No hemolysis

What do M-proteins in Streptococcus do?

Part of Group A Strep. It is a fimbria protein that prevents phagocytosis and helps the bacterial cell bind to respiratory epithelial cells.

What pyrogenic toxin induces fever and a red rash?

Erythrogenic toxin. it causes the blood capillaries near surface of skin to dilate resulting in a rash.

Which is more difficult to treat? Staph or Strep?

Staph is harder to treat since it is harder to kill. Strep is easily killed by disinfectants, antiseptics, and physical control measures.

What group is Streptococcus pyogenes classified as?

Group A

is Streptococcus pyogenes alpha, beta, or gamma hemolytic?

Beta hemolytic

what does Streptococcus pyogenes produce that increases pathogenicity?

Pathogenic strains produce capsules.

Can Streptococcus pyogenes be caused from endogenous flora or exogenous flora or both?

Both

What is Impetigo?

• Pyoderma

• May be caused by Streptococcus pyogenes or Staphylococcus aureus

• Highly contagious among preschool children and school age children

• Acquired: nick in the skin and contact with blisters or crusts, contaminated fingers or fomites

• SX- burning, itchy papules that break in to form highly contagious yellow crusts

How is the bacterium streptococcus pyogenes acquired to cause erysipelas?

The bacterium enters through entries from broken skin and spreads to dermis and subcutaneous tissues.

What does “strept throat” cause inflammation of? How common is this? how is it spread? Is this exclusive to pyogenes?

Causes inflammation of the pharynx and tonsils. It is one of the most common bacterial infections. It spreads via aerosols and snot. This bacterial infection is not only exclusive to pyogenes. It may also be caused by Staphylococcus aureus, Haemophilus influenza, and Corynebacterium diptheriae.

What toxin is produced to yield scarlet fever?

Erythrogenic toxin produced by lysogenized strains of strep.

What organ does the long term complication from GAS glomerulonephritis affect? Does it cause a local or systemic infection?

Affect kidneys. Causes a systemic infection

What long term complication from GAS- Rheumatic fever attributes to the top cause of heart valve damage to kids?

Inflammatory conditions of the heart. Causes scarring and distortion of heart valves.

What is necrotizing fasciitis? What enzymes are used? What are the initial symptoms?

A progressive, rapidly spreading, inflammatory infection that reaches the deep fascia. Enzymes such as collagenase and other toxins are used to destroy tissues and eventually destroy muscle and fat tissue. Initial symptoms are:

• Raised red area around cut or scrape

• Fever

• Sever pain and swelling.

What is the drug of choice for strep?

Penicillin. other effective drug choices are Lincomycin, erythromycin, clindamycin and third-generation cephalosporins.

What is Streptococcus pneumoniae’s major virulence factor? Is Streptococcus pneumoniae part of the normal flora?

Also known as pneumococcus, its major virulence factor is polysaccharide capsule. 5%-50%+ of population has this bacterium as part of their normal flora in mouths and nasopharynx.

How many of pneumonia cases are cause by Streptococcus pneumoniae? What are the situations/conditions increase the risk?

This bacterium is the most likely cause of pneumonia. Young children, elderly, immune compromised, those with other lung diseases or viral infections, and persons living in close quarters are predisposed to pneumonia.

what can Streptococcus pneumoniae cause to otherwise healthy little kids?

Otitis media otherwise known as middle ear infections in children.

Pneumococcal meningitis

The bacteria progresses via blood stream (bacteremia) to CSF to reproduce and inflame the meninges, excess CSF causes pressure on brain and spinal cord, permanent damage or death can occur

• Also following trauma that opens a passage between the pharynx and subarachnoid space (meninges).

• Symptoms: high fever, stiff neck, disorientation, vomiting, coma, death

Pneumococcal meningitis in children MR is 20X higher than other organisms. It is one of the top three bacteria that contribute to the cases of meningitis.

What are the two vaccines used to prevent pneumococcal meningitis?

• Pneumovax (PPSV23)- elderly 65+; at risk individuals 19-65yrs

  • Effective 5yr with 60-70% effectiveness

• Prevnar (PCV13) 4 dose series: 2-5yrs old and 65yrs+

What are the antibiotics used for pneumococcal meningitis?

penicillin, cephalosporin, erythromycin, and chloramphenicol.

Where is the Viridans group located?

Located in high numbers in the oral cavity. includes Streptococcus mutans & Streptococcus salivarius.

What species in the Viridans group attaches to the enamel?

S. mutans

What species in the Viridans group attaches to the gingival lining?

S. salivarius

What can S. mutans and S. salivarius cause in the teeth?

They contribute to plaque, dental cavities, gingivitis, and periodontal disease.

What infection is caused when bacteria from the Viridans group enters the blood?

Subacute bacterial endocarditis.

What group is Streptococcus agalactiae in? Is it part of the normal flora?

Group B. Is part of the normal flora of the human vagina and large intestine.

What problems can arise with pregnant woman who have high amounts of Streptococcus agalactiae?

It can be transferred to an infant during delivery and cause severe infection. It is the most prevalent cause of neonatal pneumonia, sepsis, and meningitis.

Mortality= ~5% but 25% of surviving infants suffer from sequale.

What genus is Streptococcus faecalis referred to now?

Enterococcus faecalis

What can kind of infections can Enterococcus faecalis cause?

UTIs, Bacteremia, endocarditis, and wound infections. Mainly come as nosocomial infections.

What does VRE stand for?

Vancomycin resistant Enterococcus

Is the Neisseria species Gram + or -? It is motile? What is its morphology? Can it live without oxygen?

• Gram -

• Non-motile

• Typically diplococcic (paired)

• Aerobic (needs oxygen to live)

What is the Neisseria species considered?

Fastidious and oxidase positive

What structure aids attachment on bacteria species Neisseria?

Fimbriae

What are the two important pathogenic species of Neisseria?

Neisseria gonorrhoeae and Neisseria meningitidis

Which Neisseria species is never part of the normal flora?

Neisseria gonorrhoeae

What does Neisseria gonorrhoeae cause? Can it live a long time outside of its host?

Causes gonorrhea & PID (pelvic inflammatory disease). It dies quickly outside of host.

What type of membrane is affected with Neisseria gonorrhoeae? Where are these locations?

Mucous membranes are affected. These locations are mainly the GU-tract, eyes, rectum, pharynx.

Can males and females be asymptomatic with Neisseria gonorrhoeae? If so, who’s more likely to be asymptomatic?

Both can be asymptomatic. Men are usually 90% symptomatic while females are 50% symptomatic.

What symptoms do males with Neisseria gonorrhoeae have?

• urethritis, painful urination, and cloudy yellow discharge (dysuria).

• Males (w/o TX) get inflammation of epididymis & prostate and results in infertility due to scar tissue.

What symptoms do females with Neisseria gonorrhoeae have?

• Symptoms: dysuria (painful urination), mucopurulent or bloody vaginal discharge. symptoms can be mild and are usually not always severe.

• Complications when infection ascends from vagina to uterus and fallopian tubes resulting in pelvic inflammatory disease (PID).

Can Neisseria gonorrhoeae infections disseminate?

Yes, into DGIs which stand for Disseminated Gonococcal infection. If left untreated it can cause meningitis, endocarditis, and arthritis.

What age group can be affected due to infected or carrier moms of Neisseria gonorrhoeae?

newborns

What is use to treat or prevent Neisseria gonorrhoeae?

• Crede's Method 1% AgNO3 (won't kill Chlamydia infection of eye).

• Erythromycin or tetracycline ointments good on both.

• Usually a triple antibiotic ointment added prophy in case of Chlamydia coinfection.

• Broad spectrum intramuscular cephalosporins (ex: ceftriaxone) Plus Azithromycin or Doxycycline.

How can gonorrhea be prevented? Why are condoms effective?

• Sexual abstinence.

• Monogamy with uninfected, faithful partner.

• Consistent and proper use of condoms.

Condoms are effective because they block the ways gonorrhea can be transferred, mainly through bodily fluids.

What 2 important diseases are caused by Neisseria meningitidis?

Meningococcal septicemia & Meningococcal meningitis.

What characteristic symptoms are seen with Meningococcal septicemia? What are they a result of?

SX: fever, arthritis, appearance of minute, subcutaneous, hemorrhages called petechiae located on trunk and lower extremities.

• Large black lesions: coalescence of petechiae with regions of cell death.

• Can progress into ecchymoses or purpura (blood filled pockets).

• Result of endotoxin (lipid A).

What is inflamed with meningitis? What are some symptoms?

Inflammation of the meninges of CNS. symptoms are:

• sore throat

• fever

• headache

• stiff neck

• vomiting

• convulsions

How common is Neisseria meningitides causing meningitis in the US?

2nd most common cause of bacterial meningitis (27%).

What are the vaccines for all top 3 causative agents of bacterial meningitis?

• Menomune = (MPSV4) older than 55

• Menactra (MCV4) = new vaccine, thought to last 9-10 years, wanes after 5 years, need booster (ages 2-55)

  • MenHibrix

• Trumemba & Bexsero – specific for serotype B

  • Ages 10-25

What are the characteristics of Acinetobacter species of bacteria?

• Gram –

• Widely distributed in the environment (soil and water)

• Can survive for months on inanimate objects

  • Faucets, toilets, clothes, doorknobs, sinks, medical equipment, etc.

Because of this bacterium’s ability to survive long term in the environment, it can easily transmit through traumatic injuries from combat conditions (aka military personnel).

What species is most commonly reported? Where can it cause infection?

Acinetobacter baumannii which accounts for 80% of reported cases. it can cause infection:

• Skin (burns & wounds)

• respiratory (lungs)

• urinary tract

• blood

What 2 situations are going to place an individual at risk for acquiring the Acinetobacter bacterium?

1. During military foreign environments

2. During hospital environments