Orthopaedics and Neurosurgery Antibiotic Prophylaxis

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Questions and Answers

What is the primary toxin secreted by B. cereus that causes vomiting?

Cytotoxin

Neurotoxin

Emetic toxin (correct)

Diarrheal toxin

Which test is used to specifically detect diphtheria toxin?

Elek test (correct)

Gram stain

PCR test

Culture on blood agar

What characterizes the appearance of Corynebacterium diphtheriae on a Gram stain?

Club-shaped swellings (correct)

Spore formation

Cocci in chains

Curved rods

Which bacteria is most commonly associated with neonatal meningitis?

Streptococcus agalactiae Signup and view all the answers

What is the primary treatment for diphtheria?

Penicillin and diphtheria antitoxin Signup and view all the answers

What type of antibiotic should be used for clean-contaminated surgeries involving the GI tract?

Cefazolin Signup and view all the answers

In a case of known infection, what classification does the surgery fall under?

Dirty Signup and view all the answers

Which antibiotic is most commonly indicated for neurosurgery involving meningococcus coverage?

Ceftriaxone Signup and view all the answers

What is the advised maintenance for antibiotic concentration after surgery?

Maintain concentration >MIC until 3 days post-op Signup and view all the answers

For a patient undergoing splenectomy, which organisms must be covered postoperatively?

Pneumococcus and meningococcus Signup and view all the answers

What is the expected bacterial contamination percentage during a clean-contaminated surgery?

13% Signup and view all the answers

When should antibiotic prophylaxis be considered for high-risk surgical procedures?

To reduce emergence of bacterial resistance Signup and view all the answers

Which combination is often recommended for perforated bowel cases?

Cefuroxime and metronidazole Signup and view all the answers

Which of the following is a treatment option for uncomplicated UTIs in afebrile patients?

Ciprofloxacin Signup and view all the answers

What is a classic sign of meningeal irritation?

Kernig's sign Signup and view all the answers

Which of the following signs is indicative of raised intracranial pressure?

Early morning vomiting Signup and view all the answers

What does the presence of positive Brudzinski's sign indicate?

Meningeal irritation Signup and view all the answers

What is a primary differentiation between meningitis and encephalitis?

Involvement of subarachnoid space Signup and view all the answers

What is the primary characteristic of Mycobacterium leprae?

It causes leprosy and cannot be cultured. Signup and view all the answers

Which of the following is an example of an anaerobic organism?

Actinomyces israelii Signup and view all the answers

What serious condition can Mycobacterium avium complex (MAC) lead to?

Pulmonary disease in immunocompromised patients Signup and view all the answers

Which of the following organisms is classified as a rapid grower in non-tuberculous mycobacteria?

M. abscessus Signup and view all the answers

Which method is appropriate for culturing anaerobes like Actinomyces israelii?

Anaerobic culture on enriched media Signup and view all the answers

What is a common manifestation of infections caused by Actinomyces israelii?

Lung abscess Signup and view all the answers

Which organism is known as the most pathogenic group of Shigella?

Shigella dysenteriae Signup and view all the answers

What is a defining characteristic of the non-tuberculous mycobacterium group classification based on the Runyon classification?

Oxygen requirements and pigment production Signup and view all the answers

In which condition is the risk of reactivation of certain mycobacterial infections increased?

During immunocompromised states Signup and view all the answers

What characterizes the growth of Mycobacterium chelonae?

It requires aquatic environments for growth. Signup and view all the answers

What is the primary disease caused by Rickettsia rickettsii?

Rocky Mountain Spotted Fever Signup and view all the answers

Which organism is responsible for causing Brill-Zinsser disease?

Rickettsia prowazekii Signup and view all the answers

Which type of virus tends to have a higher mutation rate due to lower proofreading capabilities?

RNA viruses Signup and view all the answers

What is the main vector for Borrelia burgdorferi, the causative agent of Lyme disease?

Ticks Signup and view all the answers

Leptospira interrogans is primarily associated with which of the following conditions?

Weil's disease Signup and view all the answers

Which of the following statements about enveloped viruses is correct?

They are more easily destroyed by alcohol. Signup and view all the answers

What is the primary method for confirming a leptospirosis infection?

Microscopic agglutination test Signup and view all the answers

Coxiella burnetii is most commonly associated with which of the following diseases?

Q fever Signup and view all the answers

Study Notes

Orthopaedics: Antibiotic Prophylaxis

Cefazolin (1st gen cephalosporin) is the most common antibiotic used for prophylaxis in orthopaedic surgery.
Staphylococcus species (1GC with MSSA coverage) are the most common bacteria causing infections in orthopaedics.
Clean-contaminated: Surgical procedures involving the GI tract, GU tract, and respiratory tract without gross contamination.
Contaminated: Surgical procedures involving the GI tract, GU tract, and respiratory tract with expected bacterial contamination.
Dirty: Surgical procedures involving known infection such as abscesses, gangrene, and necrotizing fasciitis.

Neurosurgery: Antibiotic Prophylaxis

Ceftriaxone (3rd gen cephalosporin) is the most common antibiotic used for prophylaxis in neurosurgery.
Consider CSF concentration and limited time of action (decisive period): Ceftriaxone's effectiveness is limited by CSF concentration and duration of action.
Clean-contaminated: Surgical procedures involving the transection of the GI tract.

Staphylococcus Infections

Staphylococcus species (1GC with MSSA coverage) are the most common bacteria causing infections in orthopaedics and neurosurgery.
MSSA coverage: Antibiotics should cover methicillin-sensitive Staphylococcus aureus (MSSA), a common cause of infections.

Cefazolin

Cefazolin (1st gen cephalosporin) is a broad-spectrum antibiotic effective against many gram-positive bacteria.
Cefazolin is commonly chosen for orthopaedic surgery because of its long half-life. This allows for effective coverage during the critical period for preventing surgical site infections.

Ceftriaxone

Ceftriaxone (3rd gen cephalosporin) provides broader coverage than cefazolin, making it a good choice for neurosurgery.
Consider CSF concentration: Ceftriaxone's ability to reach therapeutic levels in the CSF is crucial for preventing infections.
Limited time of action: The duration of action for ceftriaxone must be considered in the context of the surgical procedure.

Antibiotic Prophylaxis: Balance

High-risk period vs. reducing antibiotic exposure: The decision on whether to use antibiotic prophylaxis should be based on the risk of infection and the potential for adverse effects from prolonged antibiotic exposure.

Splenectomy: Antibiotic Prophylaxis

Penicillin: Antibiotic prophylaxis with penicillin is recommended after splenectomy to protect against infections with encapsulated bacteria.
Vaccination: Vaccination against encapsulated bacteria is vital after splenectomy to reduce infection risk.

Bacilli: Bacillus cereus

Food poisoning: Bacillus cereus is a common cause of food poisoning, especially from rice dishes.
Toxin production: Bacillus cereus produces both emetic and diarrheal toxins.
Fried rice syndrome: Bacillus cereus-related food poisoning often involves vomiting, known as "fried rice syndrome."

Corynebacterium diphtheriae

Gram stain appearance: Corynebacterium diphtheriae appears as club-shaped swellings at the end of bacilli on Gram stain.
Albert stain: Albert stain highlights volutin granules (metachromatic granules) within the bacteria.
Tellurite medium: Corynebacterium diphtheriae grows black colonies on tellurite agar.
Elek test: The Elek test is used to detect diphtheria toxin production.
Diphtheria: Corynebacterium diphtheriae is the causative agent of diphtheria, a potentially fatal disease characterized by sore throat and the formation of a pseudomembrane in the throat.
Diphtheria vaccine (DTaP) The DTaP vaccine protects against diphtheria, tetanus, and pertussis.

Neonatal Meningitis: Most Common Bacteria

Group B strep: Streptococcus agalactiae (group B strep) is the most common cause of neonatal meningitis.
Escherichia coli: E. coli is a common cause of neonatal meningitis.
Listeria monocytogenes: Listeria monocytogenes is a cause of neonatal meningitis, particularly in newborns with risk factors such as prematurity.

Shigella vs Salmonella: Differentiating Features

Bacillary dysentery: Shigella species are the primary cause of bacillary dysentery, a notifiable disease.
Human as the only reservoir: Shigella infections are exclusively found in humans.
Obligate aerobe: Shigella species require oxygen for growth, making them more common in the upper lobes of the lungs.
Resistance to alveolar macrophages: Shigella can resist destruction by alveolar macrophages and form granulomas.
Latent infection: Shigella can remain latent and reactivate in immunocompromised individuals.

Non-Tuberculous Mycobacterium

Runyon classification: Non-tuberculous mycobacterium (NTM) are classified into Groups 1-4 based on their pigment production and growth rate.
Rapid growers: Mycobacterium abscessus, fortuitum, and chelonae are rapid-growing NTM.
M. marinum: Mycobacterium marinum is an NTM that typically causes infections related to water exposure.
M. kansaii: Mycobacterium kansaii is an NTM commonly associated with pulmonary disease.
MAC (M. avium, intracellulare, chimaera): MAC is a complex of NTM that can cause pulmonary disease, particularly in individuals with pre-existing lung conditions such as COPD.
Mycobacterium leprae: Mycobacterium leprae causes leprosy but cannot be cultured in vitro.

Actinomyces israelii

Obligate anaerobe: Actinomyces israelii is a non-spore-forming, obligate anaerobic bacteria.
Branching filamentous bacilli: Actinomyces israelii appears as branching, filamentous bacilli under microscopy.
Sulfur granules: Actinomyces israelii forms sulfur granules, small white to black bodies that are visible in clinical specimens.
Reservoir: Actinomyces israelii is a normal inhabitant of the oral cavity and female genital tract.
Transmission: Actinomyces israelii infections are typically endogenous, meaning they arise from bacteria within the host's own body.
Clinical presentations: Actinomyces israelii infections can manifest as lung abscesses, brain abscesses, and cervicofacial actinomycosis.
Treatment: Treatment of Actinomyces israelii infections involves surgical drainage and prolonged antibiotic therapy.

Anaerobic Infections: Covering Anaerobes

Closed-space infections: Anaerobic bacteria are a common cause of infection in closed spaces, making it essential to cover anaerobic bacteria in these cases.

Rickettsial Organisms

Weil-Felix test: The Weil-Felix test is a serological test that identifies rickettsial infections by detecting cross-reactivity with Proteus vulgaris antigens.
R. rickettsia: Rickettsia rickettsia is a tick-borne pathogen that causes Rocky Mountain Spotted Fever.
R. prowazekii: Rickettsia prowazekii is a louse-borne pathogen that causes epidemic typhus.
Brill-Zinsser disease: Brill-Zinsser disease is a recrudescent form of epidemic typhus.
R. typhi: Rickettsia typhi is a flea-borne pathogen that causes murine typhus.
O. tsutsugamushi: Orientia tsutsugamushi is a mite-borne pathogen that causes scrub typhus.
Coxiella burnetii: Coxiella burnetii is a highly infectious bacterium that causes Q fever.
Q fever: Q fever is a multisystemic disease that can present with pneumonia, hepatitis, and endocarditis.
Culture-negative endocarditis: Coxiella burnetii is often difficult to culture, making it a potential cause of culture-negative endocarditis.
Pyrexia of unknown origin (PUO): Q fever can present as a pyrexia of unknown origin.

Spirochetes

Dark-ground microscopy: Dark-ground microscopy is a technique used to visualize spirochetes, which are thin, corkscrew-shaped bacteria.
Penicillin: Penicillin is the primary treatment for spirochetal infections.
Treponema pallidum: Treponema pallidum is the causative agent of syphilis.
Borrelia burgdorferi: Borrelia burgdorferi is the causative agent of Lyme disease.
Erythema migrans: Erythema migrans is the characteristic skin lesion of Lyme disease, a circular rash that expands over time.
Lyme disease: Lyme disease is a multisystemic illness that can involve the skin, joints, nervous system, and heart.
Leptospira interrogans: Leptospira interrogans causes leptospirosis.
Weil's disease: Weil's disease is a severe form of leptospirosis characterized by liver and renal failure.
Icteric leptospirosis: Icteric leptospirosis is a form of leptospirosis associated with jaundice.
Anicteric leptospirosis: Anicteric leptospirosis is a form of leptospirosis without jaundice.
Rat/rodent contact: Leptospirosis is often acquired through contact with contaminated urine or feces.

Basic Virology

RNA vs DNA viruses: The genetic material of viruses can be either DNA or RNA. RNA viruses have a higher mutation rate than DNA viruses due to a lack of proofreading mechanisms during replication.
Envelope vs non-envelope viruses: Enveloped viruses have a lipid envelope surrounding their capsid, while non-enveloped viruses lack this envelope. Enveloped viruses are more susceptible to inactivation by alcohol, which disrupts the lipid envelope.
Baltimore classification: The Baltimore classification system categorizes viruses based on their genome structure and replication mechanisms.
Reverse transcriptase viruses: Reverse transcriptase viruses, such as HIV, are able to convert their RNA genome into DNA. Reverse transcriptase viruses have particularly high mutation rates.

Urinary Tract Infections (UTIs): Treatment

Escherichia coli, Klebsiella, Proteus: These bacteria are common causes of UTIs.
Extended spectrum beta-lactamases (ESBLs): Some strains of these bacteria produce ESBLs, enzymes that can inactivate certain antibiotics, including some beta-lactam antibiotics.
Foley catheter: The presence of a Foley catheter is associated with a higher risk of UTIs.
Fluoroquinolones: Fluoroquinolones, such as ciprofloxacin, are effective against many UTIs but can be less effective against ESBL-producing strains.
Third-generation cephalosporins: Third-generation cephalosporins, such as cefotaxime, are effective against many ESBL-producing strains.

Central Nervous System (CNS) Infections: Clinical Manifestations

Meningitis: Meningitis is an infection of the meninges, the membranes that surround the brain and spinal cord.
Leptomeninges: Meningitis typically affects the leptomeninges, the pia mater and arachnoid mater, which are the innermost layers of the meninges.
Subarachnoid space: Meningitis involves inflammation and fluid accumulation in the subarachnoid space, the space between the pia mater and arachnoid mater.
Stiff neck: A hallmark of meningitis is stiff neck, or nuchal rigidity.
Kernig's sign: Kernig's sign is a positive finding in meningitis. It occurs when the hip is flexed to 90 degrees, and extension of the knee is painful or resisted.
Brudzinski's sign: Brudzinski's sign is another positive finding in meningitis. It occurs when passive flexion of the neck causes a reflex flexion of the hips and knees.
Increased intracranial pressure (ICP): Meningitis can lead to increased intracranial pressure, which can cause symptoms such as headache, vomiting, papilledema, and sixth cranial nerve (CN VI) palsy.
Bulging fontanelles (infants): Bulging fontanelles can occur in infants with meningitis due to increased intracranial pressure.
Encephalitis: Encephalitis is an inflammation of the brain, which can cause a range of neurological symptoms, including decreased mental state.

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Test your knowledge on the antibiotic prophylaxis used in orthopaedics and neurosurgery. This quiz covers commonly used antibiotics, the types of surgical procedures, and the specific pathogens involved in infections. Perfect for students and professionals in medical fields.