Microbiological Diseases: Nonrespiratory Infectious Diseases
Chapter 8: Microbiological Diseases: Nonrespiratory Infectious Diseases
Chapter Contents
Introduction
8-2 Infectious Diseases of the Head and Neck
8-2a Meningitis
8-2b Encephalitis
8-2c Otitis Media
8-2d Parotitis
8-3 Infections of the Eye
8-3a Conjunctivitis
8-3b Keratitis
8-4 Cardiovascular Infections
8-4a Endocarditis
8-4b Catheter-Related Bloodstream Infections (CRBSIs)
8-5 Infectious Diseases of the Skin and Soft Tissues
8-5a Cellulitis and Erysipelas
8-5b Necrotizing Skin and Soft Tissue Infections
8-6 Intra-Abdominal Infections
8-6a Appendicitis
8-6b Acute Cholecystitis
8-6c Diverticulitis
8-6d Clostridium difficile Colitis
8-6e Infectious Diarrhea
8-7 Genitourinary Tract Infections
8-7a Sexually Transmitted Diseases
8-8 Urinary Tract Infections
8-9 Bone and Joint Infections
8-9a Osteomyelitis
8-9b Septic Arthritis
8-10 Chapter Review
8-10a Chapter Summary
Chapter Introduction
Learning Objectives:
Describe symptoms, types of organisms, and treatment for head and neck infectious diseases (meningitis, encephalitis, otitis media, parotitis).
List possible antimicrobial treatments based on specific infections.
List viral causes of encephalitis.
Discuss when to initially avoid antimicrobials for acute otitis media in children.
Describe eye infectious diseases (conjunctivitis and keratitis) and their treatment.
Compare symptoms and treatment of cardiovascular infections (endocarditis, CRBSIs) and skin/soft tissue infections.
Describe intra-abdominal infectious diseases (appendicitis, cholecystitis, diverticulitis, Clostridium difficile colitis, diarrhea) and prevention.
Discuss common sexually transmitted infections and their treatment.
8-1 Introduction
Chapter 7 laid foundational knowledge of antimicrobial therapy. Chapters 8 and 9 will use a systems approach to explore infectious diseases and their treatment.
Focus is on non-respiratory infectious diseases, bypassing respiratory infections until Chapter 9.
8-2 Infectious Diseases of the Head and Neck
Discussion of infections affecting the brain, ears, parotid gland, and eyes.
8-2a Meningitis
Definition: Meningitis is an inflammation of the meninges, caused primarily by infectious agents (bacteria, viruses, fungi) or other factors (e.g., bleeding, cancer).
Symptoms:
Fever
Neck stiffness (nuchal rigidity)
Decline in mental status
Headache
Meningitis can affect healthy individuals or those with health issues, especially post-surgery or after brain injury requiring monitoring equipment.
Diagnosis:
Blood cultures and lumbar puncture for CSF analysis are critical for identification of causative pathogens with Gram staining.
Common pathogens and treatments summarized in Tables 8-1 and 8-2.
Prophylaxis: Exposure to Neisseria meningitidis requires rifampin or ciprofloxacin prophylaxis.
Vaccination: Meningococcal vaccines recommended for immunocompromised, high-risk adults, and college students.
Tables 8-1 and 8-2: Common Causes and Treatments of Meningitis
Common Causes of Community-Acquired Bacterial Meningitis:
Streptococcus pneumoniae: Gm+ diplococci treated with Vancomycin + ceftriaxone ± ampicillin in patients >50 years
Neisseria meningitidis: Gm- diplococci
Group B Streptococcus: Gm+ cocci
Haemophilus influenzae: Gm- coccobacilli
Listeria monocytogenes: Gm+ bacillus
Common Causes of Health Care–Associated Meningitis:
Enterobacteriaceae: Gm- bacilli treated with Vancomycin + cefepime or meropenem
Pseudomonas aeruginosa: Gm- bacilli
Staphylococcus aureus: Gm+ cocci
8-2b Encephalitis
Definition: Encephalitis is an inflammation of the brain often due to direct viral infection or hypersensitivity reactions. Symptoms differ from meningitis, presenting with headaches and abnormal brain functions (e.g., memory deficits, seizures).
Viruses causing encephalitis include:
Cocksackie, echovirus
West Nile Virus, St. Louis virus, and Eastern equine virus (transmitted via mosquito bites)
Mumps and measles with peak incidence in winter.
Herpes Simplex Virus (HSV) - fatal without treatment; tested with PCR detection of HSV DNA.
8-2c Otitis Media
Definition: A middle ear infection characterized by pain and potentially partial hearing loss. Common in infants and children.
Symptoms: Irritability, ear tugging, lack of energy & appetite, fever, and vomiting.
Diagnosis: Difficult due to non-verbal infants. Treated with observational techniques to avoid antibiotic resistance unless severe.
Risk Factors: Male gender, siblings, early onset, bottle feeding, day care, tobacco exposure, and use of pacifiers.
Table 8-5: Microbial Causes of Acute Otitis Media
Common pathogens include Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and viral causes.
Treatment may involve antibiotics like amoxicillin and may require tubes for chronic cases.
8-2d Parotitis
Infection of parotid glands characterized by severe pain, difficulty swallowing, and fever. Common causes include Staphylococcus aureus and anaerobes.
Treatment outside hospital: Vancomycin + metronidazole or clindamycin.
Treatment in hospital: Vancomycin + piperacillin-tazobactam or meropenem for broad-spectrum coverage.
8-3 Infections of the Eye
Examined for infections affecting the sclera and cornea.
8-3a Conjunctivitis
Definition: Inflammation of the conjunctiva. Common causes are bacterial (Staphylococcus aureus, Streptococcus pneumoniae, Neisseria gonorrhoeae) or viral (primarily adenoviruses).
Symptoms include discharge and redness. Contagiousness is prevalent; hygiene is crucial. Treatment may involve topical antibiotics or symptomatic relief for viral causes.
8-3b Keratitis
Definition: Inflammation of the cornea, requiring urgent ophthalmological evaluation.
Can be caused by various microbes, necessitating cultured diagnosis to inform antibiotic therapy. Acyclovir may be used for herpes simplex infections.
8-4 Cardiovascular Infections
Infections spanning heart valves and bloodstream infections from catheters.
8-4a Endocarditis
Definition: Inflammation of the endocardium, potentially leading to severe health issues including stroke and kidney damage.
Symptoms include nonspecific flu-like symptoms and may result in skin manifestations like petechiae.
Diagnosis: Echocardiogram for vegetations on heart valves; treated with prolonged intravenous antibiotics based on the identified pathogens.
Common causes and treatments are documented.
Table 8-6: Microbial Causes of Endocarditis
Treatment course may last from 2 to 6 weeks based on organism type and valve status. Patients may require valve replacement in severe cases.
8-4b Catheter-Related Bloodstream Infections (CRBSIs)
Infections resulting from catheter placements that can allow bacteria into the bloodstream, leading to potentially serious complications.
Risk factors include use of catheters for chronic conditions or intravenous drug use. Diagnostic procedures include blood cultures.
Table 8-7: CRBSI Organisms and Antimicrobial Treatment
Empirical therapy involves broad coverage for both gram-positive and gram-negative organisms until culture results are available. Confirmed infections often require catheter removal.
8-5 Infectious Diseases of the Skin and Soft Tissues
Comprehensive analysis of infections within the skin and underlying soft tissues.
8-5a Cellulitis and Erysipelas
Cellulitis involves lower dermal and fat tissue infection, while erysipelas affects upper dermis and lymphatics, presenting with a sharply defined rash.
Diagnostic processes rely on clinical examination. Infection characteristics and treatment vary based on purulence and severity.
Table 8-8: Causative Microbes and Treatments
Identifies pathogens and treatment recommendations based on infection type.
8-5b Necrotizing Skin and Soft Tissue Infections
Urgent medical attention required due to high mortality risk. Clinical symptoms include severe pain and rapid deterioration. Treatment involves surgical intervention and broad-spectrum antibiotics.
8-6 Intra-Abdominal Infections
Common intra-abdominal conditions include appendicitis, cholecystitis, and infectious diarrhea.
8-6a Appendicitis
Common among younger adults, appendicitis symptoms include abdominal pain radiating from the navel to the right quadrant. Surgery is often required for definitive care.
8-6b Acute Cholecystitis
Gallbladder inflammation can occur with or without stones, presenting with right upper quadrant pain following high-fat meals. Empirical antibiotic therapy initiated before surgical procedures.
8-6c Diverticulitis
Characterized by inflammation of diverticula, often leading to complications like abscesses. Treatment may require surgery depending on the severity.
8-6d Clostridium difficile Colitis
Associated with prior antibiotic use, it presents with varying severity of diarrhea and abdominal pain. Diagnosis based on clinical symptoms and stool testing.
8-6e Infectious Diarrhea
Related to contaminated food and travel; treated primarily with supportive care. Understanding associated pathogens is significant for preventative strategies.
8-7 Genitourinary Tract Infections
Encompassing a range of infections in the genitalia and urinary tracts.
8-7a Sexually Transmitted Diseases
Overview includes bacterial and viral STDs, highlighting prevalent infections such as Chlamydia, Gonorrhea, and Herpes Simplex Virus (HSV).
Treatment Guidelines for STDs
Details on treatment protocols for common STDs emphasizing effective treatment to prevent complications and spread.
8-8 Urinary Tract Infections
Involves infections of the urinary tract classified as lower (cystitis) or upper (pyelonephritis). Common in sexually active women.
Diagnosis and Treatment
Diagnostic procedures include urinalysis and culture. Treatment effectiveness generally high with common antibiotics based on uropathogen susceptibility.
8-9 Bone and Joint Infections
8-9a Osteomyelitis
Bone infections typically necessitate both antibiotics and surgical intervention; presentation includes localized pain and systemic symptoms.
8-9b Septic Arthritis
Characterized by joint infection, presenting with swelling and pain. Rapid diagnosis and treatment are crucial to prevent lasting joint damage.
Chapter Contents
Introduction
8-2 Infectious Diseases of the Head and Neck
8-2a Meningitis
8-2b Encephalitis
8-2c Otitis Media
8-2d Parotitis
8-3 Infections of the Eye
8-3a Conjunctivitis
8-3b Keratitis
8-4 Cardiovascular Infections
8-4a Endocarditis
8-4b Catheter-Related Bloodstream Infections (CRBSIs)
8-5 Infectious Diseases of the Skin and Soft Tissues
8-5a Cellulitis and Erysipelas
8-5b Necrotizing Skin and Soft Tissue Infections
8-6 Intra-Abdominal Infections
8-6a Appendicitis
8-6b Acute Cholecystitis
8-6c Diverticulitis
8-6d Clostridium difficile Colitis
8-6e Infectious Diarrhea
8-7 Genitourinary Tract Infections
8-7a Sexually Transmitted Diseases
8-8 Urinary Tract Infections
8-9 Bone and Joint Infections
8-9a Osteomyelitis
8-9b Septic Arthritis
8-10 Chapter Review
8-10a Chapter Summary
Chapter Introduction
Learning Objectives:
Describe symptoms, types of organisms, and treatment for head and neck infectious diseases (meningitis, encephalitis, otitis media, parotitis).
List possible antimicrobial treatments based on specific infections.
List viral causes of encephalitis.
Discuss when to initially avoid antimicrobials for acute otitis media in children.
Describe eye infectious diseases (conjunctivitis and keratitis) and their treatment.
Compare symptoms and treatment of cardiovascular infections (endocarditis, CRBSIs) and skin/soft tissue infections.
Describe intra-abdominal infectious diseases (appendicitis, cholecystitis, diverticulitis, Clostridium difficile colitis, diarrhea) and prevention.
Discuss common sexually transmitted infections and their treatment.
8-1 Introduction
Chapter 7 established foundational knowledge of antimicrobial therapy. Chapters 8 and 9 will now apply a systems-based approach to explore various infectious diseases and their targeted treatments.
The primary focus in this chapter is on non-respiratory infectious diseases, with respiratory infections being comprehensively covered in Chapter 9.
8-2 Infectious Diseases of the Head and Neck
This section delves into common and significant infections affecting critical structures within the head and neck region, including the brain, ears, and parotid glands.
8-2a Meningitis
Definition: Meningitis is a severe inflammation of the meninges, the protective membranes surrounding the brain and spinal cord. It is predominantly caused by infectious agents such as bacteria, viruses, and fungi, but can also result from non-infectious factors like bleeding, cancer, or certain drugs.
Symptoms: The classic triad of meningitis symptoms includes:
Fever, often sudden onset and high grade.
Neck stiffness (nuchal rigidity), which can make it difficult or painful to touch the chin to the chest.
Decline in mental status, ranging from lethargy and confusion to coma.
Severe headache, usually generalized and persistent.
Other signs may include photophobia (sensitivity to light), phonophobia (sensitivity to sound), nausea, vomiting, and in severe cases, seizures or focal neurological deficits. Specific physical signs like Brudzinski's sign (flexion of the hips and knees in response to passive neck flexion) and Kernig's sign (resistance to extension of the knee with the hip flexed) are indicative of meningeal irritation.
Meningitis can affect healthy individuals, but those who are immunocompromised, post-surgery (especially neurosurgery), or have had a recent brain injury requiring monitoring equipment are at higher risk.
Diagnosis: Prompt diagnosis is crucial due to the rapid progression and potential for severe complications. Key diagnostic steps include:
Blood cultures to identify systemic bacteremia, which often precedes bacterial meningitis.
Lumbar puncture (spinal tap) for cerebrospinal fluid (CSF) analysis. CSF parameters critical for identification of causative pathogens include:
White blood cell (WBC) count and differential: Elevated in infection, often predominantly neutrophils in bacterial meningitis.
Glucose and protein levels: Decreased glucose and elevated protein are characteristic of bacterial meningitis.
Gram staining: A rapid method to identify bacterial morphology (Gram-positive or Gram-negative) and shape (cocci, bacilli).
Culture and Polymerase Chain Reaction (PCR): For definitive identification of bacteria, viruses, or fungi.
Common bacterial pathogens and their empirical treatments are summarized in Tables 8-1 and 8-2.
Prophylaxis: Close contacts of individuals diagnosed with Neisseria meningitidis meningitis require post-exposure prophylaxis with oral rifampin or a single dose of ciprofloxacin to prevent secondary cases.
Vaccination: Meningococcal vaccines are strongly recommended for specific high-risk groups, including immunocompromised individuals, certain high-risk adults (e.g., travelers to endemic areas), and college students living in dormitories (MenACWY and MenB vaccines available depending on strain).
Tables 8-1 and 8-2: Common Causes and Treatments of Meningitis
Common Causes of Community-Acquired Bacterial Meningitis:
Streptococcus pneumoniae (Pneumococcus): Gram-positive diplococci. It is the most common cause in adults. Treatment typically involves high-dose Vancomycin + Ceftriaxone (or Cefotaxime). Ampicillin is added for patients > years or those with risk factors for Listeria monocytogenes.
Neisseria meningitidis (Meningococcus): Gram-negative diplococci. Common in children and young adults, often associated with epidemics. Treatment often requires Ceftriaxone.
Group B Streptococcus (Streptococcus agalactiae): Gram-positive cocci. A leading cause in neonates. Treated with Ampicillin + Gentamicin or Ceftriaxone.
Haemophilus influenzae Type b: Gram-negative coccobacilli. Incidence dramatically reduced due to vaccination. Treated with Ceftriaxone.
Listeria monocytogenes: Gram-positive bacillus. Affects neonates, pregnant women, elderly, and immunocompromised patients. Treatment requires Ampicillin.
Common Causes of Health Care–Associated Meningitis: These infections often occur after neurosurgery, head trauma, or with CSF shunts.
Enterobacteriaceae (e.g., Klebsiella, E. coli): Gram-negative bacilli. Treated with Vancomycin + Cefepime or Meropenem for broad-spectrum coverage and good CNS penetration.
Pseudomonas aeruginosa: Gram-negative bacilli. Often multi-drug resistant. Treated with Vancomycin + Cefepime or Meropenem.
Staphylococcus aureus (including MRSA): Gram-positive cocci. Common post-surgical pathogen. Treated with Vancomycin.
8-2b Encephalitis
Definition: Encephalitis is an inflammation of the brain parenchyma itself, often resulting from direct viral infection of the brain tissue or as a post-infectious hypersensitivity reaction (e.g., acute disseminated encephalomyelitis). Symptoms differ significantly from meningitis by primarily presenting with headaches and profound abnormal brain functions, such as memory deficits, personality changes, altered consciousness, focal neurological signs, and seizures, indicating direct cerebral involvement.
Viruses causing encephalitis include:
Enteroviruses: Cocksackie and echovirus are common, particularly during warmer months.
Arboviruses (arthropod-borne viruses): West Nile Virus, St. Louis virus, and Eastern equine virus are significant causes, transmitted to humans via mosquito bites, especially during summer and early fall.
Mumps and measles viruses: While rare due to vaccination, these can cause encephalitis, often with a peak incidence in winter for mumps.
Herpes Simplex Virus (HSV) Type 1: This is the most common cause of fatal sporadic encephalitis in adults. It requires urgent recognition and treatment with intravenous acyclovir to prevent high mortality and morbidity, characterized by focal temporal lobe involvement. Diagnosis is typically confirmed by PCR detection of HSV DNA in CSF.
8-2c Otitis Media
Definition: Otitis media is an infection and inflammation of the middle ear, located behind the eardrum. It is characterized by severe ear pain (otalgia) and can lead to temporary partial hearing loss if left untreated. This condition is exceedingly common in infants and young children due to their developing Eustachian tubes.
Symptoms: In pre-verbal children, symptoms can be non-specific and include irritability, persistent ear tugging (though not conclusively diagnostic), lack of energy and appetite, fever, and vomiting. In older children and adults, ear pain, pressure, muffled hearing, and sometimes ear discharge if the eardrum perforates, are common.
Diagnosis: Diagnosis can be challenging in non-verbal infants. It relies on otoscopic examination to visualize a bulging, red, or opaque tympanic membrane. The American Academy of Pediatrics recommends observational techniques (watchful waiting) to initially avoid antibiotic resistance for mild, uncomplicated cases in children aged months to years, and for children over years who are not severely ill. Antibiotics are generally reserved for severe symptoms (moderate to severe otalgia, fever >), bilateral acute otitis media in young children, or persistent symptoms.
Risk Factors: Factors that increase the risk of acute otitis media include male gender, having siblings, early onset of the first episode, bottle feeding (especially supine), attendance at day care, exposure to tobacco smoke, and consistent use of pacifiers.
Table 8-5: Microbial Causes of Acute Otitis Media
Common bacterial pathogens include Streptococcus pneumoniae, Haemophilus influenzae (non-typeable strains are now more common post-Hib vaccine), and Moraxella catarrhalis. Viral causes, often concomitant with bacterial infections, also play a significant role.
Treatment usually involves antibiotics like amoxicillin or amoxicillin-clavulanate, depending on local resistance patterns and clinical severity. For chronic or recurrent cases that result in persistent middle ear effusion and hearing impairment, surgical placement of tympanostomy tubes may be required to facilitate drainage and aeration of the middle ear.
8-2d Parotitis
Parotitis is an infection and inflammation of the parotid glands, the largest salivary glands located in front of and below the ears. It is characterized by severe pain, swelling over the angle of the jaw, difficulty swallowing (dysphagia), and fever. Common bacterial causes include Staphylococcus aureus (especially in adults) and various oral anaerobes, particularly in cases of salivary duct obstruction.
Treatment outside hospital: For community-acquired cases without severe systemic signs, empiric treatment often includes Vancomycin (to cover MRSA, a concern with S. aureus) + Metronidazole or Clindamycin (for anaerobic coverage).
Treatment in hospital: For more severe cases, or those requiring hospitalization, a broader spectrum of coverage is needed. This typically involves Vancomycin (for Gram-positive/MRSA) + Piperacillin-tazobactam or Meropenem for broad-spectrum coverage encompassing Gram-negative bacilli and anaerobes.
8-3 Infections of the Eye
This section examines common infections affecting the external structures of the eye, particularly the sclera and cornea, which are crucial for vision.
8-3a Conjunctivitis
Definition: Conjunctivitis, commonly known as