Lecture 28 - Streptococcus Infections

Group A Streptococcal Infections
Group A Streptococci are also known as the beta-hemolytic Streptococcus pyogenes, which is a group of over 80 different serovars. They are found in the nasopharynx and regularly colonize the human body.

Streptococcal Pharyngitis
Strep pyogenes causes about 50% of the cases of all sore throats, which is an infection of the throat and tonsils. It is easily spread by coughing or sneezing. It leads to rhinitis (runny nose) and sinusitis in milder cases, and worsens to a red, sore, swollen, and purulent throat, as well as a fever and swollen cervical nymph nodes.

It will most likely clear spontaneously (without treatment) within 7 to 10 days, but can also worsen to a case of scarlet fever.

Scarlet fever
This is caused by strains of Streptococcus that produce an erythrogenic toxin, which causes a lobster-red rash, exfoliation (desquamation), and had a high death rate. It can proceed to infect other tissues, causing mastoiditis, otitis media, nephritis, and streptococcal toxic shock syndrome.

Puerperal Sepsis
Strep pyogenes can infect a mother during childbirth because of the tearing in the vaginal region, can go systemic and cause symptoms similar to toxic shock. Prevented with modern hygiene.

Late Non-Suppurative Sequalae
Late: 1-2 weeks; non-suppurative: no pus; sequalae: consequence. It is a follow up infection from the proteins left behind from the original Streptococcus infection.

-Rheumatic Fever
Only 3% of the population is affected, but will cause heart damage (scarring of bicuspid valve). If rheumatic fever keeps on happening, the scarring accumulates and can lead to more permanent heart damage. A prophylactic for this is Benzathine Penicillin G, which prevents strep sore throats.

-Glomerulonephritis
Affects the kidney and brain.

Others

 * Pyoderma impitego (crusty sores)
 * Necrotizing fasciitis
 * Endocarditis
 * Pneumonia

Treatment
It is sensitive to penicillin G and is still treated as such.

Group B Streptococcal Infections
Group B strep infections are caused by Streptococcus agalactiae, which is found in the GI tract or genitourinary area in about 25% of women. Only 4% of all births have problems with this organism, and children who are under 3 pounds (premature babies) are more likely to get a serious infection of Group B Strep.

Premature babies can get the early onset form of the disease, which leads to septicemia and pneumonia in a few days, which causes a death rate of 50-80%.

The normal babies have a late onset of the disease, which can lead to meningitis and subsequently loss of hearing, metal issues, and cerebral palsy.

Immunocompromised people such as people with diabetes can acquire group B strep infections as well.

It can be treated with penicillin G and ampicillin.

Pneumococcal Infection
Caused by pneumococcus or Streptococcus pneumoniae, these infections are caused by the normal flora in our nasopharynx. Many cases are found in nursing homes because older people are more susceptible.

Typical Pneumonia
Typical pneumonia is an infection of the lungs and occurs when the lungs are being digested by an organism. The vaccines for this are PPV 23 and Prevnar 13, which only covers a few serovars of the Strep. pneumonia bacteria.

Meningitis
Bacterial meningitis are caused by most commonly by Streptococcus pneumonia, Neisseria meningitidis, and Haemophilus influenzae.

Otitis Media
Pneumococcus is the main cause of a middle ear infection.

Treatment is mainly done with penicillin G. If it's sensitive, penicillin G is taken orally, but is given by IV if it is intermediate. If the strain is resistant, vancomycin and a cephalosporin (ceftriaxone/cefotaxime) will be given.

Other Opportunistic Strep
Streptococcus mitior: found within oral cavity; most common cause of endocarditis (75% of cases) by entering the bloodstream during dental surgery/cleaning.

Streptococcus mutans: not a main cause of endocarditis, major organism that causes dental caries, or cavities.

Enterococcus faecalis: found in the GI tract (feces); can cause endocarditis or UTIs. Enterococcus faecalis can become vancomycin-resistant, which leads to more serious infections.