Gram Positive Cocci: Strep and Staph

Gram Positive Cocci: Strep and Staph

Organism Staph Aureus

Enterrococcus (Fecalis and Fecium)

Physiology/Structure Gram (+) cocci formed in clusters

Facultative Anaerobes

Catalase (+)

Coagulase (+)

-Hemolytic

Virulence A protein evades phagocytosis

Coagulase forms fibrin clot around organism, protecting it from phagocytosis

Toxic Shock Syndrome Toxin produces the superantigen TSST-1 that leads to toxic shock.

Exfoliatin causes the skin to slough off, disrupts desmosomes.

Enterotoxin causes gastroenteritis

Gram (+) Coccus, it is one of the Strep Species

Survives Bile and Salt so can colonize in the gall bladder.

Lancefield Group D'

Can grown in Bile or in High Salt (6.5%)

Epidemiology Is normal flora found in mucous membranes and skin. Transmission can either be endogenous or exogenous. Common contamination is found in food workers that sneeze on their hands, then don't wash. Found on food that has been left out, like potatoe salid.

They are part of the normal flora of the GI and GU tract. During a procedure, they can be dislodged or displaced and presented to where they should no be.

Diseases Gastroenteritis usually self limiting. Can be caused by ingestion of bacteria (then subsequent production of toxin) or by ingestion of heat stabile toxin produced before organism was killed by cooking.

Scalded Skin Syndrome local infection produces a toxin distally. Causes mild epidermal tears, with a "sunburn like rash"

Toxic Shock associated with tampons left in too long, toxin is a superantigen that causes fever, hypotension, and death

Infective Endocarditis acute onset endocarditis with fever, malaise, and a heart murmur. Caused by cytolytic toxins UTI GI ? GU

Cholecystitis ? infection of the gallbladder.

Tx Gastroenteritis is self limiting, and the organism is passed with stool

It is gram (+) with penicillinase activity, so Beta- Lactams don't work.

Methacillin and Nafcillin were drugs of choice because of their resistance to penicillinase. MRSA (methicillin resistant staph aureus) has made treatment more difficulty.

Vancomycin is now the drug of choice, though resistant strains are being identified. Penicillin

Normal Flora

Most prevalent bacteria of GI tract

Strep Pyogenes

Hemolytic

PYR (+) Gram (+) Coccus

Lancelfield Group A

Hemolytic

Bacitracin Sensitive to separate it from Strep Agalactiae

Endogenous Transmission

Theme is "escape or spread" M protein ? antiphagocytic protein. M12 is associated with glomerular nephritis

Streptolysin O ? Oxygen Labile, antigenic cytolysin that causes lysis of cells.

Streptolysin S ? Oxygen Stabile, nonantigenic cytolysin that causes lysis of cells.

"ASE"s Streptokinase, DNAase, Hyalurindase, all makes it easier to spread in tissue.

Exotoxin A-C that are superantigens and cause symptoms of scarlet fever

Human throat, transmitted by aerosol droplets or endogenous infection.

Sequellae of Disease (to fit better)

Rheumatic Fever ? possible sequella of untreated pharyngitis ONLY. This is a type II hypersensitivity reaction, where antibodies to the strep cross react with heart tissue. Causes endocartitis, a chorea, fever, and arthralgia.

Poststreptococcal Glomerular Nephritis ? possible sequella of untreated strep pharyngitis or skin infection. Type III hypersensitivity reaction. Immune complexes are deposited in the kidney, causing damage. Associated with M12 serotype

Pharyngitis ? white, purulent lesions on the oropharynx.

Scarlet fever ? if strep throat is untreated it can then be accompanied by scarlet fever. It is described as a sand- paper rash, also called a sun burn-like rash, in that the skin is red. The palms and soles are spared. There is also a strawberry tongue that presents bright red with many bumps.

Impetigo - just like staph aureus

Necrotizing Fasciitis - infection that causes "flesh-eating bacteria." Rapid spread through fascial layer can involve large amounts of tissue requiring debreidment or amputation.

Culture all negatives on a rapid test.

Lactams work well.

In those with allergies, use macrolides.

Organism Strep Pneumoniae

Physiology/Structure Gram (+) Coccus

LancetShaped Diplococci

No Lancelfield Group

Hemolytic

Optochin Sensitive to separate it from Viridans group

Virulence Capsule ? most important virulence factor

IgA protease ? cleaves IgA that allows colonization of mucosa.

Pneumolysin O ? what is responsible for the rust colored sputum associated with the disease. Destroys ciliated cells by inducing classic complement.

Epidemiology Normal flora of the upper respiratory tract. They can be colonized, but not be infected. Any immunocompromise (chronic pulmonary disease, viral infection, spleen-ectomy) can lead to pathogenesis

Diseases Acute Pneumonia rapid onset of fever and chills, pain on inspiration, and an X- ray with infilitrates

Otitis Media ? most common cause of otitis media in children, despite vaccine.

Sinusitus ? same as otitis media, commonly causes sinusitis in kids

Adult Meningitis ? since the vaccine for H. Influenzae b (later), now is leading cause of meningitis in neonates.

Tx Macrolides for adult bacterial pneumonia

Third Generation Cephalosporin for meningitis

Vaccines are available. The pediatric vaccine covers 7 common serotypes protecting against meningitis.

The adult vaccine covers 23 common serotypes to protect against pneumonia

Viridans group

Gram (+) Coccus No Lancelfield Group Hemolytic

Dextran Bioslime that both protect the organism from the immune system and increases adherence to teeth or heart valves

Optochin Resistant to separate it from S. Penuemo

This is a variety of organisms such as S. Mutans.

S. Mutans is part of the normal flora of dental caries. These buggers cause plaque. Plaque then allows other Viridans group to colonize and cause cavities

Subacute Endocarditis ? dental surgery gives S. Mutans access to the blood stream where it colonizes the mitral valve.

This is why people with prostethic valves or previous valve problems get prophylactic antibiotics before dental procedures.

Penicillin often prophylactic for endocarditis.

In pharm, you learn you treat with Clindamycin or a combination of Vancomycin + Gentamycin.

Gram Positive Rods: BCC LAN LM "Send an Email (BCC) over the network (LAN) to Lincoln Martin (LM)"

Bacillus, Corynebacterium, Clostridium, Lactobacillus, Actinomyces, Nocardia, Listeria, Mycobacteria; you know "N" is NOT neisseria because Mycobacteria and Nocardia are similar.

Organism Bacillus Anthracis

Bacillus Cereus

Physiology/Structure Gram (+) Rod Forms spores Is unique for its polypeptide capsule (most others are polysaccharide) Facultatively Anaerobic

Gram (+) Rod Forms spores Same as Bacillus Anthracis

Virulence Spore Forming so they are highly resistant to drying, desiccation, heating, etc.

Antiphagocytic Capsule evades phagocytosis

Exotoxins Edema Factor ? calmodulin

dependent increase in cAMP leading to fluid extrusion.

Lethal Factor ? causes tissue necrosis. Protective Factor -allows entry of toxins into target cells. Called this because it is target of vaccine. Similar virulence to Anthracis, has different toxins

Exotoxins Emetic Toxin causes N/V/D 1-6 hrs after ingestion Diarrheal Toxin causes a cAMP dependent secretory diarrhea similar to Cholera or ETEC

Epidemiology Found in soil, water, and on animals (particularly sheep). Can be inoculated into a cutaneous wound or inhaled into the lungs. Possible agent of bioterrorism (note the postal scare).

Found on food that was cooked and reheated. Think buffet line at a Chinese food restaurant. The classic presentation is fried rice at a Chinese buffet.

Diseases Cutaneous Anthrax is 95% of all anthrax cases. Spores get into wound causing black painless swollen postules called eschars. They crust over and resolve spontaneously. They can rarely enter circulation and cause fatal septicemia.

Diagnosis Formerly Penicillin (which may still work).

Currently use doxycyline or cirpofloxain

Pulmonary Anthrax (Woolsorter's Disease). Inhaled spores cause hemorrhagic lymphedemitis with mediastinal widening. It resembles many pulmonary diseases initially, and is rapidly fatal without treatement. Normally transmitted by sheep, it is now a risk of bioterrorism. Gastroenteritislike symptoms

Self Limiting

Corynebacterium Diphtheriae

Gram (+) Rod Aerobic

Toxin ? inhibits protein synthesis. It is a classic AB toxin that inhibits EF- 2

Non-spore formers

Form "Chinese Letters" on gram stain, V or L shape.

While it colonizes the naso or oropharynx, it is not invasive

Grow Grey or Black colonies on Tellurite

Loeffler's Media causes granule formation

Throat and nasopharynx, usually transmitted by respiratory droplets.

Diphtheria ? Grey pseudomembrane that is on the pharynx. It is well attached and will cause hemorrhage if removed. It is here that necrotic tissue, leukocytes, and the corynebacterium are. If the membrane gets to large, it can cause respiratory obstruction.

Elek test will confirm toxin producing strains. In this test, bacteria are streaked across a plate, with a elek strip placed across all streaks. It contains an anti-toxin that causes precipitation

Bull Neck ? swelling of the neck out

Antitoxin is top priority to neutralize toxin

Antibiotics will kill bacteria, and stop the toxin production

DPT vaccine

Organism Clostridium Tetani

Clostridium Botulinum

Clostridium Difficle

Physiology/Structure

Same as other clostridium species, no double zone of hemolysis

Virulence

Tetanus Toxin (tetanospasmin)? causes spastic paralysis known as Tetanus.

Classic AB toxin that targets the central nervous system, inhibiting inhibitory neurons by preventing vesicle transport and fusion.

No fusion = no release. No release = disinhibition of skeletal muscles = contraction.

Targets GABA and glycine.

Same as other clostridium species, no double zone of hemolysis

BotulismToxin ? causes spastic paralysis known as Botulism.

Classic AB toxin that targets the peripheral nerves, inhibiting NMJ neurons by preventing vesicle transport and fusion.

No fusion = no release. No release = inhibition of skeletal muscles = flaccid.

Same as other clostridium species, no double zone of hemolysis

Targets ACh Toxin A = Enterotoxin Causes inflammation and secretory diarrhea

Toxin B = Cytotoxin Disrupts protein synthesis and

causes disorganization of the cytoskeleton.

Epidemiology Found in dirt, soil, or dust.

Common presentation is a penetrating wound (such as a rusty nail).

Diseases

Tetanus Bacteria colonize a local infection,

housed in necrotic tissue (anaerobic space).

Secrete exotoxin that travels everywhere, targets the CNS inhibitory neurons.

Symptoms begin with trismus (lockjaw) and risus sardonic us (a smile that cannot be stopped)

Diagnosis

Antitoxin binds and neutralizes free toxin in circulation

Toxoid (aka the vaccine) conveys long term neutralization of toxin and active immunity. Survival DOES NOT convey immunity.

Give injections at separate sites

It is also found in dirt, soil, or dust, that can cause the low-yield wound botulism.

Found in homecanned foods that are not cooked well enough.

Progresses to a spastic paralysis with death resulting from spasm of diaphragm

Adult Botulism ? food contaminated with botulism is not cooked or prepared well enough. Begins with dipolia and dysphagia, progressing to flaccid paralysis and death from flaccid diaphragm

Muscle Relaxants (benzos) to alleviate contractions

Palliative care to provide ventilator support

Antitoxin to alleviate circulating toxin (any toxin in cells has already taken effect).

Found in honey given to newborns.

Infant Botulism ? honey contaminated with botulism in an infant less than one year old. Begins with constipation and feeding problems progressing to floppy baby syndrome.

Penicillin to kill bacteria

Part of the normal GI Flora.

When on broadspectrum antibiotics the normal flora is eliminated. This is highly resistant, so then grows in the space left by the previous flora.

Psuedomembranous Colitis ? watery, secretory diarrhea that results from the enterotoxin. Ulcerations can be visualized on endoscopy resulting from Cytotoxin. Cultures will be positive (normal flora), but a tox screen of stool will confirm diagnosis.

Discontinue antibiotic therapy.

Give oral vancomycin (one of the few drugs it is NOT resistant to). You must give it orally because vancomycin cannot penetrate GI barrier, and the infection is in the GI tract.

Lactobacillus

Lowyield organism

Know that it maintains the vaginal pH to prevent exogenous infection. When giving broad-spectrum antibiotics, you can kill lactobacillus, and allow overgrowth of other organisms (like candida)

Actinomyces Israelii

Nocardia Asteroides

Listeria monocytogenes

Facultatively anaerobic/strictly anaerobic

NOT acidfast (contrast to Nocardia)

Colonize URT, GI, female genital tracts

Actinomycosis ? chronic granulomatous lesions -> suppurative and form abscesses

Grow slowly

Filamentous hyphae

Resemble "grains of sand" -> sulfur granules

NOT found on skin

Gram (+) branching rods.

Partially AcidFast

Aerobic

Ill defined pathogenesis

No person to person spread

Disease from soil or water

Cervicofacial infections -> poor oral hygiene; invasive dental procedure

Thoracic infections -> Hx of aspiration -> spreads to lung-adjoining tissues

Most cases: Cervico facial -> draining sinus tracts along angle of jaw/neck

Difficult

Culturing is slow

Sulfur granules -> tin, gram positive, branching rods around periphery

Abdominal infections -> GI surgery; trauma to bowel

Pelvic infections -> secondary manifestation of abdominal actinomycosis; primary infection of woman with IUD

CNS -> hematogenous spread from other tissues Reservoir is Soil and Dust, thus there is an exogenous inoculation via trauma or inhalation.

(Inhalation) Cavitary Broncholpulmonary Nocardosis ? often associated with immune compromised patients. Symptoms are fever, cough, diffuse pneumonia with cavitation of the lungs.

Sulfonamides

Spread via the blood to the brain.

(Traumatic Implantation) Subcutaneous nocardosis ? training type of sinus tracts and granules. This is similar to actinomyces only with a traumatic implantation.

G+ve coccobacili -> arranged in pairs resembling enterococci

Faculative anaerobes

Motile at room temp, weakly -hemolytic, capable of growth at 4?C and high salt concentration

Facultative intracellular pathogen that can avoid Ab-mediated clearance

Virulent Strains produce cell attachment factors (internallins), hemolysins (listeriolysin O, two phospholipase Cs), and a protein that mediates actin-directed motility (ActA)

Isolated in soil, water, and vegetation

Disease assoc. with consumption of contaminated food products (unpasteurized milk)

Transplacental spread from mother to neonate (vaginal transmission)

Neonatal Disease Amnionitis: 1. Early onset disease:

"granulomatosis infantiseptica" -> disseminated ascesses and granulomas in multiple organs 2. Late onset disease: acquired at or shortly after birth. Presents as meningitis or meningoencephalitis w/ septicemia

"Actin rockets" ? cell to cell movement

HIGH RISK: Young, elderly, Pregnant, pts with defective cellular immunity

Healthy Adults: Influenza like (with or without gastroenteritis)

Pregnant women/cellmediated immune defects: Primary bacteremia or disseminated disease (hypotension and meningitis)

Microscopy -> insensitive

Culture 2-3 days or cold enrichment

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