MS Infectious Disease Flashcards
infection leading to the necrosis of subcutaneous tissue. Severe pain is common. Infection should be treated very seriously and aggressively through surgery and IV antibiotics and fluids.
Nectrotizing Fasciitis
Most common causative agent of necrotizing fasciitis
Strep pyogenes
rapidly progressing joint infection. Usually bacterial in origin.
Acute infectious arthritis
Most common causative agent acute infectious arthritis
Staph aureus
(N. gonorrhea in sexually active young people)
inflammation and destruction of bone caused by bacteria, mycobacteria, or fungi. Causes localized bone pain and tenderness. 80% of infections result from contiguous spread or from open wounds.
Osteomyolitis
infection of the muscle that leads to muscle inflammation. Can be caused by many different microorganisms including viruses, bacteria, and helminthes.
Myositis
Presence of bacteria in bloodstream
bacteremia
Viremia
presence of virus in bloodstream
bloodborne systemic infection. Can lead to spread of the infectious organism to other tissues, massive inflammation, septic shock, and rapid death. Associated with bacterial infections
Septicemia
3 ways for bacteria to initiate infection
- Breach the skin
- Systemic disease
- Toxin-mediated damage
Life-threatening infection of subcutaneous tissues, most often caused by beta-hemolytic, group A Streptococcus (Streptococcus pyogenes) and to a lesser degree Staphylococcus aureus and other microorganisms.
Necrotizing fasciitis
“Flesh-eating bacteria”, toxin mediated disease
Necrotizing fasciitis
Necrotizing Fasciitis: Life-threatening infection of ________ tissues, most often caused by ____-hemolytic, _________ and to a lesser degree __________ and other microorganisms. Can be ____________.
•Life-threatening infection of subcutaneous tissues, most often caused by beta-hemolytic, group A Streptococcus (Streptococcus pyogenes) and to a lesser degree Staphylococcus aureus and other microorganisms. Can be polymicrobial.
Nectrotizing fasciitis: More than 50% of patients have experienced a recent _____, _______, or _______ infection.
More than 50% of patients have experienced a recent minor trauma, surgery, or varicella infection.
Nectrotizing Fasciitis: Can result in widespread _______ of the skin, ______, ________, and _____.
Can result in widespread desquamation of the skin, shock, multiorgan failure, and death.
NF: The infection tends to begin with a _____, _____, or _______ that extends from superficial skin layers down through fascia and muscle.
The infection tends to begin with a break in the skin, invasion, or deep blunt trauma (hematoma) that extends from superficial skin layers down through fascia and muscle.
NF: Tx
Aggressive surgical intervention is required to prevent the spread of infection, in addition to antibiotics.
Gas gangrene vs NF
GG has crepitance (gas formation)
Streptococcus Pyogenes tree
Bacteria - Gram+ - Cocci - Catalase (-) - beta-hemolytic - bacitracin sensitive
Bacteria - Gram+ - Cocci - Catalase (-) - beta-hemolytic - bacitracin sensitive
Streptococcus pyogenes (NF)
Strep Pyogenes virulence factors
streptokinase, M protein, hyaluronidase, Dnase.
Necrotizing Fasciitis sxs
High fever
High heart rate
Altered mental status
Low blood pressure
Leukocytosis (high white blood cell count)
Positive blood cultures
Dx of NF
- Rapid onset
- High CRP
- High ESR
- High WBC with banded neutrophils
- CT imaging could reveal edema of the soft tissues
- Gram stain the wound
- Culture the wound (sample taken during surgery) and blood
- Surgical debridement of necrotic tissue
WBC measures ____
Leukocytes per mL blood
WBC high counts –>
high counts during infections, inflammatory diseases, autoimmune systemic diseases, leukemia, and emotional and physical stress.
Normal Range WBC
4500-11000 cells/mL
Banded neutrophil
Committed to neutrophil pathway - but not fully mature. LEFT SHIFT. Sign of severe acute infection.
Normal WBC differential
Basophils ≤ 2%
Eosinophils ≤ 5%
Lymphocyte 22 – 44% (high in viral infections, tuberculosis, typhoid)
Monocytes 3 – 9%
Neutrophils 40 – 60% (high in acute bacterial infections, others. Bands = immature neutrophils “left shift”)
Lymphocytes high in _
Viral infections, tuberculosis, typhoid
Neutrophils high in _
Acute bacterial, others. Banded – severe.
ESR
Erythrocyte Sed Rate
Rate at which red blood cells precipitate in a period of 1 hour when anti-coagulated blood is allowed to stand. Rough measure of abnormal acute phase proteins and immunoglobulins. Nonspecific indicator of tissue damage and inflammation.
Normal ESR
<= 20mm/hr
ESR elevated in _
anemia, endocarditis, kidney disease, osteomyelitis, pregnancy, and many others.
C-Reactive Protein
Produced in the liver and is present in circulation at low levels normally. Involved in the promotion of the immune system through the activation of the complement cascade.
Normal CRP
<= 1mg/dL
CRP elevated in _
bacterial infections, inflammation conditions, acute rheumatic fever, acute rheumatoid arthritis, inflammatory bowel disease, and others.
Synovial fluid changes in acute infectious arthritis
Change in color to more yellow
More cloudy/opaque
May be hemorrhagic (d/t virulence factors of infectious agent) –> blood in synovial fluid (red)
Sxs Acute Infectious Arthritis
Rapid onset
Personal history
Pain
Range of motion restriction (single joint)
Synovial fluid analysis and culture
Positive blood cultures
Bacteria
Gram +
Cocci
Catalase +
Coagulase +
Bacteria
Gram +
Cocci
Catalase +
Coagulase +
Staphylococcus aureus
Staph aureus tree
Bacteria
Gram +
Cocci
Catalase +
Coagulase +
Staphylococcus aureus
Bacteria
Gram (-)
Diplococci
Oxidase (+)
Only Glucose Oxidizer
Bacteria
Gram (-)
Diplococci
Oxidase (+)
Only Glucose Oxidizer
Neisseria gonorrhoeae
Neisseria gonorrhoeae tree
Bacteria
Gram (-)
Diplococci
Oxidase (+)
Only Glucose Oxidizer
Neisseria gonorrhoeae
N. gonorrhoeae like to be in _____ cells
Neutrophils
Staph aureus virulence factors
protein A, coagulase, hemolysins, leukocidins, hyaluronidase, staphylokinase, lipase.
N. gonorrhoeae virulence factors
Specialized pili – allows attachment to mucosal surface, antigenic variation to evade host defenses, prevents phagocytosis.
Endotoxin.Capsule.IgA protease.
Osteomyelitis sxs
Acute - weight loss, fatigue, fever, localized warmth, erythema, tenderness. May form subcutaneous abcesses which drain spontaneously through skin. Chronic - intermittent bone pain, tenderness, draining sinuses.
tx osteomyelitis
Abx, surgery to remove abcesses, potential spinal instability or necrotic bone.
Osteomyelitis –> _________ in bone
Abcesses
Osteomyelitis - differential
Skin infections may be deep seated with an abscess, or mainly cellulitis (superficial redness and warmth).
Gas gangrene would have crepitance on palpation due to the presence of gas.
Skin cancers may manifest with similar lesions, but usually in older individuals.
Sarcomas may manifest with skin or soft-tissue lesions.
TB classically causes osteomyelitis of the vertebrae, called Pott disease, although other areas may be seen; overlying cellulitis is uncommon in such cases.
S. aureus is the most common cause of skin and soft-tissue infections.
TB causes __________ (often as losing control of ds)
Osteomyelitis (also encephalitis) - but usually vertebrae (Pott disease)
Most common cause of skin/soft-tissue infection –> osteomyelitis
Staph aureus
Bacteria
Gram -
Coccobacilli (pleomorphic)
Oxidase +
Catalase +
Pasteurella multocida
Where get Pasteurella multocida?
Cat bite (normalized flora)
Bacteria
Gram -
Bacilli
Lactose non-fermenter
Oxidase –
Produces H2S
Motile
Salmonella typhii
Salmonella typhii tree
Bacteria
Gram -
Bacilli
Lactose non-fermenter
Oxidase –
Produces H2S
Motile
Salmonella typhii and osteomyelitis predisposing factor
Sickle cell anemia - Salmonella super invasive but normal blood cell people could typically clear quickly, but sickle cell –> lack of complement
Alternative –> C3 catalyzes own breakdown on cell surface into C3b which goes into bloodstream – start to bind stuff – target S. typhii
Sickle Cell – complement receptor localizes in pocket of RBC before pathogen bound (trapped)
Pasteurella multocida tree
Bacteria
Gram -
Coccobacilli (pleomorphic)
Oxidase +
Catalase +
Salmonella, Sicke Cell and osteomyelitis
combination of expanded marrow in sickle cell patients together with high oxygen demand and sluggish circulation means that bone is vulnerable to infarction.
Infarcted areas act as loci for infection.
Gut devitalization due to intravascular sickling leads to an increased incidence of invasion and bacteremia.
Sickle cell patients have reduced bactericidal and opsonic activity against Salmonella and an abnormality in the alternative pathway of complement activation.
Bacteria
Gram +
Bacilli
Spore-forming
Obligate anaerobe
Non-motile
Clostridium perfringens
C. perfringens tree
Bacteria
Gram +
Bacilli
Spore-forming
Obligate anaerobe
Non-motile
Myositis causative agents
C. perfringens, Staph aureus, coxsackievirus A and B, Dengue Fever virus, Taenia solium, Trichinella spiralis
Virus
ssRNA (+), Group IV
Nonsegmented
Icosahedral Nucleocapsid
Nonenveloped
Picornaviridae
Enterovirus
Coxsackievirus A and B
Coxsackievirus A and B tree
Virus
ssRNA (+), Group IV
Nonsegmented
Icosahedral Nucleocapsid
Nonenveloped
Picornaviridae
Enterovirus
Virus
ssRNA (+), Group IV
Nonsegmented
Icosahedral Nucleocapsid
Enveloped
Flaviviridae
Dengue Fever Virus (Flavivirus)
Dengue Fever Virus tree
Virus
ssRNA (+), Group IV
Nonsegmented
Icosahedral Nucleocapsid
Enveloped
Flaviviridae
Helminth
Transmitted by ingestion
Intestinal and tissue infection
Platyhelminthes (flatworms)
Cestodes (tapeworms)
Taenia solium
Taenia solium tree
Helminth
Transmitted by ingestion
Intestinal and tissue infection
Platyhelminthes (flatworms)
Cestodes (tapeworms)
Taenia solium
Helminth
Transmitted by ingestion
Tissue infection
Nematodes (roundworms)
Trichonella spiralis
Trichinella spiralis tree
Helminth
Transmitted by ingestion
Tissue infection
Nematodes (roundworms)
This infection is typically caused by a mixture of aerobic and anaerobic organisms leading to the necrosis of subcutaneous tissue. Signs of infection include tissues that become hot, red, and swollen, resembling severe cellulitis. Severe pain is common. Without timely treatment the area of infection becomes gangrenous. Patients present acutely ill. Diagnosis is through history and examination, supported by evidence of overwhelming infection. Treatment includes antibiotics and surgical debridement. Prognosis is poor without early aggressive treatment.
Necrotizing Fasciitis
severe muscle pain is the hallmark of _____________ (myositis)
pleurodynia (coxsackievirus B), trichinellosis, and bacterial infection
Only non-motile Clostridium member
Clostridium perfringens
NF treatment
Abx and surgical debridement
Most NF cases result from infection with _____
group A streptococcus (Streptococcus pyogenes) or a mixture of aerobic and anaerobic bacteria (Bacteroides species)
NF:
The primary symptom of infection is ____________. Tissue is __, ___, and ____ and rapidly becomes ____.
Bullae, crepitus (resulting from soft tissue gas), and gangrene may develop.
_______ necrose but muscles are spared initially. Patients present _______ with a high ____, high ____, altered ______, and low ______. Patients may be ________. ____________ may develop.
The primary symptom of infection is intense pain (pain out of proportion of clinical findings). Tissue is hot, red, and swollen and rapidly becomes discolored. Bullae, crepitus (resulting from soft tissue gas), and gangrene may develop. Subcutaneous tissues necrose but muscles are spared initially. Patients present acutely ill with a high fever, high heart rate, altered mental status (confusion), and low blood pressure. Patients may be bacteremic or septic. Streptococcal toxic shock syndrome may develop.
NF Dx
History and examination and is supported by _____, _____ on x-ray, _____ blood cultures, and deteriorating ____ and ______ status.
Diagnosis is made by history and examination and is supported by leukocytosis, soft-tissue gas on x-ray, positive blood cultures, and deteriorating metabolic and hemodynamic (blood pressure) status.
NF affects what tissues
SubQ necrosis - but muscles are initially spared (may turn into myositis)
Common organisms causing Acute infectious arthritis classified as ____ or _____ in adults
gonococcal or nongonococcal
AIA: ______ infections are far less destructive to the joint
gonococcal infections are far less destructive to the joint
AIA: Adolescents and adults
Gonococci (young, sexually active adults), nongonococcal bacteria (Staphylococcus aureus, streptococci)
Cervical, urethral, rectal, or pharyngeal infection with bacteremic dissemination – gonococci.
Bacteremia – staphylococci and streptococci
AIA: Neonates
Group B streptococci, Escherichia coli, Staphylococcus aureus
Maternal-fetal transmission; IV punctures or catheters with bacteremic dissemination
AIA: Children =<3
Streptococcus pyogenes, Streptococcus pneumoniae, Staphylococcus aureus
Bacteremia (otitis media, URIs, skin infections, meningitis, etc)
AIA: 3-adolescence
Staphylococcus aureus, streptococci, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Kingella kingae
Bacteremia or contiguous spread
AIA: All ages
Viruses (parvovirus B19, HBV, HCV, rubella virus, VZV, mumps virus, adenoviruses, coxsackieviruses A and B, HIV, EBV)
Viremia or immune complex deposition
AIA: Pt w/ possible tick exposure
Borrelia burgdorferi (Lyme disease)
Bacteremia
AIA: Pt w/ bite wound
Often polymicrobial.
Human bites – Eikenella corrodens, group B streptococci, Staphylococcus aureus, oral anaerobic bacteria.
Dog and cat bites – Staphylococcus aureus, Pasteurella multocida, Pseudomonas species, Moraxella species, Haemophilus species.
Rat bites – Staphylococcus aureus, Streptobacillus moniliformis, Spirillum minus
Direct joint penetration, usually of the small joints of the hands
AIA: The elderly, patients with severe joint trauma or serious disease (immunosuppression, hemodialysis, SLE, RA, diabetes, cancer)
Staphylococci (particularly in RA), gram-negative bacteria, Salmonella species (particularly in SLE)
Urinary tract, skin
GC arthritis sxs
fever (for 5 to 7 days), multiple skin lesions on the mucosal surfaces and on the trunk, hands, or lower extremities. Inflammatory arthritis in one or more joints also occurs often in the hands, wrists, elbows, knees, and ankles.
Other AIA symptoms
progressive moderate to severe joint pain that is markedly worsened by movement. Most infected joints are swollen, red, and warm. Fever is absent or low in about 50% of patients. In 80% of adults, nongonococcal bacterial arthritis is monoarticular. In infectious arthritis due to bite wounds symptoms typically develop within 48 hours. Rat bites tend to cause systemic symptoms including fever, rash, and joint pain within about 2 to 10 days. Viral infectious arthritis causes symptoms that can be similar to nongonococcal arthritis and is more likely to be polyarticular.
AIA dx
arthrocentesis with synovial fluid examination and culture, blood culture, imaging studies, CBC and ESR (or CRP). Synovial fluid examination is key. Fluid is sent for cell count and differential, Gram stain, culture, and crystals. Foul-smelling synovial fluid suggest anaerobic infections. Fluid from an acutely infected joint will have a WBC of greater than 20,000/μL consisting of greater than 95% PMNs. Gram stain results are suggestive of the causative microorganism but cultures are definitive. The presence of crystals does not rule out infectious arthritis.
________ can destroy articular cartilage, permanently damaging the joint.
Acute nongonococcal arthritis can destroy articular cartilage, permanently damaging the joint.
_________ accounts for 50% of cases of viral myocarditis.
Coxsackie B virus accounts for 50% of cases of viral myocarditis.
Coxsackie B pathology: infections are typical in_______ (seasonal) and the virus is transmitted via ________ or ________. The virus travels in the ______ and infects ___________. Local replication ensues and virus spreads in the ________. From here the virus infects and can lyse ______ and _______ surfaces to cause ____________ (3).
infections are typical in summer and fall and the virus is transmitted via aerosols or fecal to oral route. The virus travels in the G.I. tract and infects mucosal epithelial cells. Local replication ensues and virus spreads in the bloodstream. From here the virus infects and can lyse heart and pleural surfaces to cause pleurodynia, myocarditis, and pericarditis.
Coxsackievirus: In Group A and B infections the virus can travel to the _______ and __________ to cause ________ and _______.
In Group A and B infections the virus can travel to the meninges and anterior horn motor neurons to cause meningitis and paralysis.
Cox B dx
isolate virus, serology.
Cox B tx
Symptomatic infections – anti-inflammatory agents. No antivirals or vaccines available.
Dengue Fever Virus: geographic location
This virus is found in the tropics worldwide. Dengue hemorrhagic fever is most common in southern Asia.
DFV: Clinical Presentation
Dengue fever – “breakbone fever” (flu-like with severe joint and muscle pain).
Dengue hemorrhagic fever – (dengue fever with hemorrhage and shock).
DFV
____, _____, and ______ are all normal reservoirs for this virus. It is transmitted through ________ and enters the ______ to cause __________. From here the virus infects _________ causing acute inflammation release of __________ and _________ to create “____________”. If this initial infection is followed by a second infection of a different serotype, then ________ from the first serotype infection _________ and ________ to form ___________ and a ___________ which can lead to ________ and _________ (_________).
humans, monkeys, and birds are all normal reservoirs for this virus. It is transmitted through a mosquito bite and enters the bloodstream to cause transient viremia. From here the virus infects macrophages causing acute inflammation release of pyrogens and pain mediators to create “breakbone fever”. If this initial infection is followed by a second infection of a different serotype, then antibodies from the first serotype infection increase and cross-react to form immune complexes and a type III hypersensitivity reaction which can lead to hemorrhage and shock (Dengue Hemorrhagic Fever).
How pathogens get into joints for AIA?
Infectious organisms reach the joints by direct penetration (trauma, bites, surgery, etc), extension from an adjacent infection (osteomyelitis, abscess, infected wound, etc), or hematogenesis spread from a remote site of infection.
______ are major host defense system in AIA but also the cause of joint damage
PMNs
Neutrophils, eosinophils, and basophils are polymorphonuclear leukocytes. A polymorphonuclear leukocyte is a type of white bloodcell. Also called granular leukocyte, granulocyte, and PMN.
Osteomyelitis dx
ESR, CRP, Xray, MRI, radioisotropic bone scanning, culture bone/abcess formation. Suspect if localized peripheral bone pain, fever, malaise or localized refractory vertebral pain. PE. Need to dx specific bacteria.
Osteomyelitis pathogenesis/location
Bone - may occlude local blood vessels –> bone necrosis and local spread of infection. Bone cortex, under periosteum, formation of subcutaneous abcesses.
Myositis dx
temporal progression of lesions, travel hx, animal exposure/bite hx, age, underlying ds, lifestyle. Soft tissue radiography, CT, MRI.
Leading cause of osteomyelitis in children and adults
Staphylococcal aureus
Coxsackie A vs B/A
B - pleurodynia, myocarditis, pericarditis
A + B - aseptic meningitis, paralysis, URT infection
Tricuspid valve endocarditis
Frequent in IV drug users, staph aureus
Patients w/ granulomatous ds are vulnerable to ______
staph aureus
Staph aureus clinical presentation
Local: skin/subQ- impetigo, cellulitis, folliculitis, furuncles, carbuncles.
Respiratory: pneumonia w/ cavitations
Systemic: acute endocarditis, meningitis, osteomyelitis, septic arthritis
Staph Aureus pathology: Bacteria colonize _____ or _____ (how) → overgrow and evade host defenses using ____, _____, _____, and _____. _____ localize to site of infection → _______ form → ________ infections or _____ results. Deeper invasion into the bloodstream relies on the _____, ______, and _____ virulence factors.
Bacteria colonize skin (following breach) or nasopharynx (following intubation or viral infection) → overgrow and evade host defenses using protein A, coagulase, hemolysins, and leukocidins. Neutrophils localize to site of infection → purulent abscesses form → skin/subcutaneous infections or pneumonia results. Deeper invasion into the bloodstream relies on the hyaluronidase, staphylokinase, and lipase virulence factors.
Staph aureus dx
Blood culture for Gram +, catalase +, coagulase +
Staph aureus tx
Abx - penicillinase-resistant penicillins or vancomycin
Obligate human pathogens
Neisseria gonorrhoeae
Salmonella Typhi
N. gonorrhoeae high incidence w/
menstruation, IUDs, sexually active
N. gonorrhoeae: __________ prevents immunity allowing recurrent infections
Antigenic variation (d/t specialized pili)
N. gonorrhoeae clinical presentation
Local infection = (genital tract or anorectal infections) either asymptomatic, urethritis, dysuria (men), cervicitis (women), opthalmia neonatorum.
Systemic = septic arthritis.
Complications = Pelvic Inflammatory Disease (PID), ectopic pregnancy, sterility, Fitz-Hugh-Curtis Syndrome
N. Gonorrhoeae pathology
Colonization begins when bacterial ___ attach to mucosal cells of ____ and ____. Evades mucosal _______ via _______. _____ by _______ and kills _________ –> inflammatory response leading to _______ (men) and _____ (women).
In women, infection can progress to _____, ______, ________ which can lead to increased risk for _____________. From _______ bacteria can spill into the __________ causing _______. This can lead to an infection of the ________ (Fitz-Hugh-Curtis Syndrome).
Colonization begins when bacterial pili attach to mucosal cells of urethra and vagina. Evades mucosal IgA antibodies via IgA protease. Endocytosed by immune cells and kills ciliated cells –> inflammatory response leading to urethritis (men) and cervicitis (women).
In women, infection can progress to uterus, fallopian tubes, and ovaries (PID) which can lead to increased risk for ectopic pregnancies. From fallopian tubes bacteria can spill into the peritoneal cavity causing peritonitis. This can lead to an infection of the liver capsule (Fitz-Hugh-Curtis Syndrome).
N. gonorrhoeae: Septic Arthritis pathogenesis
The bacteria can also invade the _____ and enter into the ______ where it can collect in ________ causing septic arthritis.
The bacteria can also invade the submucosa and enter into the bloodstream where it can collect in synovial fluid causing septic arthritis.
N. Gonorrhoeae in neonates
Can inoculate the conjunctiva during passage through the birth canal causing opthalmia neonatorum –> risk for blindness.
N. gonorrhoeae DX
Gram (-) diplococci within PMNs, metabolizes glucose but not maltose, selectively grows on Thayer-Martin media.
NG TX
Ceftriaxone (+ doxycycline for probable concurrent Chlamydia infections), prophylactic erythromycin eye drops for neonates. Vaccine development difficult.
Salmonella Typhii virulence factors
H antigen (flagella), endotoxin, Vi capsule.
Susceptible to Salmonella typhi
Sickle-cell patients are functionally asplenic and have trouble clearing Vi-encapsulated Salmonella.
Patients with impaired gastric acid secretion are more susceptible.
Complication of S. typhi
Because S. typhi are stored well in gallstones, carriers may present with S. typhi-induced necrotizing cholecystitis
Clinical presentation S. Typhi
asymptomatic carrier state, typhoid fever (enteric fever), osteomyelitis in sickle cell patients.
S. Typhi Pathology:
Spread through _______ transmission. Large inoculum overcomes the ______. Bacteria penetrates the ________ barrier in the ________ which leads to transient _____________.
______________ (VF) allows survival in _______ of ________. Spread via ______ to the ______, _______ and _______ where ________ is then released. This creates ______ on the _______ , _____ , ______, and ________ (typhoid fever). This infection can then progress into the ________ or it may ___________.
Spread through fecal-to-oral transmission. Large inoculum overcomes the gastric acid defense. Bacteria penetrates the mucosal barrier in the distal ileum or colon which leads to transient asymptomatic bacteremia.
Capsular Vi polysaccharide allows survival in phagocytes of Peyer’s patches. Spread via phagocytes to the gallbladder, liver, and spleen where endotoxin is then released. This creates rose spots on the abdomen, fever, diarrhea, and abdominal pain (typhoid fever). This infection can then progress into the carrier state or it may self-resolve.
S. typhi carrier state
the bacteria are stored in the gallbladder, especially in gallstones. The bacteria may reenter the bowel lumen to generate more microorganisms that can spread through contaminated feces.
S. typhi dx
Gram (-) rod cultured from the blood. Motile by flagella. Produces hydrogen sulfide. Does not ferment lactose.
S. typhi tx and caveat
Ceftriaxone for resistant strains. Ciprofloxacin and ampicillin for carriers. Cholecystectomy may be necessary for carriers. Two oral vaccines are available for travelers (killed or live-attenuated).
Treating S. typhi infections may actually increase the risk for reinfection due to interference of the development of a suitable host immune response.
Pasteurella multocida clinical presentation
cellulitis, osteomyelitis following cat and dog bites.
Pasteurella multocida pathology: This bacteria normally inhabits the ______ of _____. It enters the human skin via a _________ and elicits an ________ response at the inoculation site. From here the bacteria can spread locally to _____ or ________. The infection has the possibility to progress to _______.
This bacteria normally inhabits the oral cavity of animals. It enters the human skin via a bite wound and elicits an inflammatory response at the inoculation site. From here the bacteria can spread locally to soft tissue (cellulitis) and bone (osteomyelitis). The infection has the possibility to progress to septicemia.
P. multocida dx
Gram (-) coccobacilli with bipolar staining.
P. Multocida tx
Suturing the wound may worsen the infection by creating a closed anaerobic environment which can favor bacterial growth. Penicillin G. Clean and drain wound.
This is the only nonmotile Clostridium member.
Clostridium perfringens
necrosis of the small intestine caused by β-toxin release. Common in New Guinea following large ingestion of pork (excess protein overwhelms trypsin digestion of β-toxin) 40% mortality.
Enteritis necroticans: caused by Clostridium perfrigens
C. perfringens clinical presenation
cellulitis, gas gangrene (myonecrosis with crepitus), food poisoning
C. perfringens pathology – Cellulitis
bacteria normally found in the ____ and _____. Bacteria infect _____ environment of ________ and release _______ (_______ and _______). This generates a ____ _______ infection and ______ production. The infection eventually forms collections of _____ under the skin that _____ when touched (______).
Cellulitis – bacteria normally found in the soil and GI tract. Bacteria infect anaerobic environment of necrotic skin wound and release digestive enzymes (collagenase and hyaluronidase). This generates a slow painless infection and gas production. The infection eventually forms collections of gas under the skin that crackle when touched (crepitus).
C. perfringens Gas Gangrene Pathology
The infection is initiated from ____________ introduced into ____ _____ wounds. Here the spores can _____ and ______ in the ______ environment to release _______ which causes ________; _______ enzymes which produce ______ and _______. Gangrenous muscles lead to ________ leaking from the skin. ________ may follow.
The infection is initiated from spores found in the soil. These spores are introduced yet deep muscle wounds (military wounds, automobile accidents, crude abortions). Here the spores can germinate and grow in the anaerobic environment to release alpha toxin (lecithinase) which causes deep muscle cell necrosis; degradative enzymes which produce subcutaneous gas bubbles and crepitus. Gangrenous muscles lead to black fluid exudate leaking from the skin. Shock may follow.
C. perfringens Food Poisoning pathology
Initiated from spores found in _____. These spores can survive _____ and germinate to __________ that is then _______. The bacteria release _______ in the ______. This ______ inhibits ________ and damages the ______. This causes _______, ________, and ________. _____ and ______ are not common.
the infection is initiated from spores found in meat and poultry foods. These spores can survive cooking and germinate to contaminate food that is then ingested. The bacteria release heat-labile enterotoxin in the GI tract. This enterotoxin inhibits glucose transport and damages the epithelium. This causes diarrhea, gastric pain, and nausea. Fever and vomiting are not common.
C. perfringens Dx
Gram (+) rod, strict anaerobe, nonmotile.
C. perfringens Tx
surgical removal of infected areas. Hyperbaric oxygen to kill anaerobic organisms. Penicillin, clindamycin (only effective in local, weak infections).
Trichinella spiralis clinical presentation
gastroenteritis, myalgia.
Trichinella spiralis pathology
Reservoir = ____. ________ ingested from ________. _____ mature into ______ in ________. ______ mate and eggs mature to _____. ______ can penetrate _________ and gain access to ______ –> _________ and ______.
______ can be carried by ____ to ______ (often to ____, _____, _____, _____) where localized inflammation –> _______. ______ can form a ______ that can last for years and may calcify.
If many __________ are ingested this can lead to a severe infection where the _____ can migrate to the heart and brain causing ________ and ________.
Reservoir = pigs. Encysted larvae ingested from uncooked meat. Larvae mature into adults in small intestine. Adult worms mate and eggs mature to larvae. Larvae can penetrate intestinal wall and gain access to bloodstream –> diarrhea, pain.
Larvae can be carried by blood to skeletal muscle (often to extraoculars, masseters, tongue, and diaphragm) where localized inflammation –> myalgia. Larvae can form a fibrous cyst that can last for years and may calcify.
If many encysted larvae are ingested this can lead to a severe infection where the larvae can migrate to the heart and brain causing myocarditis and encephalitis.
Trichinella spiralis dx
eosinophilia. Striated muscle biopsy contain cysts with larvae. Serology for chronic infection.
T. spiralis tx
Mebendazole/thiabendazole (against adult worms in the small intestine). No treatment to remove cysts from muscle. Steroids for severe myositis and myocarditis.
Taenia solium clinical presentation
intestinal infection – asymptomatic, malnutrition, abdominal discomfort. Tissue infection – cysticerosis (neurological defects, blindness).
T. solium pathology: Intestinal infection
intestinal infection: larvae found as ______ in _______ which get ingested in ________. In the _________ the larvae mature and grow to generate adult worms consisting of a _________ and ________. The ______ attaches to the ________, _______ containing eggs passed in ______. The worm consumes the food that is ingested by the host leading to __________.
intestinal infection: larvae found as cystercerci in pig muscle which get ingested in poorly cooked pork. In the small intestine the larvae mature and grow to generate adult worms consisting of a scolex (head) and numerous proglotids (autonomous segments). The scolex attaches to the intestinal wall, proglotids containing eggs passed in feces. The worm consumes the food that is ingested by the host leading to malnutrition.
T. solium pathology: Tissue infection
humans ingest eggs from _________ and the eggs hatch into _____ in the _______. ______ penetrate the _______ and travel to other tissues (________, _________ and __________) to form _______ containing ______. The ________ grow slowly eventually leading to neurological defects (seizures, focal symptoms) or blindness. When _____ die (several years later) this caused increased _______ and __________.
humans ingest eggs from infected feces and the eggs hatch into oncospheres in the small intestine. Oncosheres penetrate the intestinal wall and travel to other tissues (brain, skeletal muscle, and eye) to form cysticerci containing larvae. The cysts grow slowly eventually leading to neurological defects (seizures, focal symptoms) or blindness. When cysts die (several years later) this caused increased inflammation and aggravated symptoms.
T. solium dx
intestinal infection: proglottids, eggs in stool.
Tissue infection: calcified cysticerci in muscle, brain on X-ray or CT scan. Eosinophilia in muscle, brain also seen in X-ray or CT scan.
T. solium tx
intestinal infection: niclosamide + cathartic; praziquantel.
Tissue infection: praziquantel or albendazole + steroids (reduce inflammation from the dying cysts).
Acute bacterial infection CBC w/ differential results
High WBC (>11,000), high PMNs (>60%), left shift (banded)
Both Staph aureus and strep pyogenes are ________ hemolytic
Beta
Treatment for osteomyelitis (suspect staph)
Possible draining of abscess, empiric abx - IV → clindamycin w/ or w/o ciprofloxacin, or levofloxacin
MRSA - Vancomycin
Staph aureus vs. epidermidis
Aureus - beta-hemolytic, yellow-like colonies, color change on mannitol salt agar
Epidermidis - common in IV infections, gamma-hemolytic, white colonies, no color change on mannitol salt agar
Both gram + cocci, catalase +
Mannitol salt agar changes color from red to yellow in acidic
Both can grow in the salty area (like skin)
Most common microorganism in osteomyelitis in sickle cell
Salmonella typhi
Salmonella produce oxidase?
No - Oxidase negative (many gram-negative rods DO produce oxidase, like pseudomonas)
Chronic Granulomatous Disease
Deficient NADPH oxidase - cannot make enough H2O2 to kill catalase+ phagocytosed cells
(usually cells make enough H2O2 to kill bacteria regardless of catalase, if deficient NADPH oxidase - catalase converts H202 to water and hydrogen - so if only have a little, not gonna work)
Following a barbecue hosted by a hunter who served “black bear burgers” several guests develop abdominal pain and diarrhea. Their condition progresses about a week later to fever, myalgia, periorbital edema, and petechial hemorrhages in the conjunctiva. A peripheral blood smear shows an increased eosinophil count. What is the most likely cause of these symptoms?
Trichinosis
(parasites –> eosinophils = hallmark)
