Microbiology: Bacterial Infections Overview

Study Notes

Major cause of neonatal sepsis, especially in developed countries.
Typically colonizes the maternal vaginal or rectal regions.
Diagnostic methods include blood, urine, and cerebrospinal fluid (CSF) cultures.
Treatment of choice is Penicillin G.
Empirical treatment may involve Cefotaxime or Ampicillin combined with Amikacin.

Associated with hospital-acquired infections.
Clinical manifestations include sepsis, urinary tract infections (UTIs), peritonitis, meningitis, and endocarditis.
Diagnostic methods also involve CS cultures.
Treatment may include Penicillin G or Ampicillin in combination with Amikacin.
Notable resistance to Vancomycin.

Acute contagious disease caused by a non-motile, encapsulated Gram-positive bacillus.
Unique Gram stain appearance: Chinese character or palisading.
Transmission occurs through respiratory or skin secretions, with an incubation period of 1-5 days.
Pathophysiology involves localized inflammation and systemic effects from diphtheria exotoxin.
Exotoxin leads to cellular apoptosis by inactivating elongation factor.
Characteristic clinical manifestations include:
- Respiratory diphtheria with grayish membrane on tonsillopharynx and potential airway obstruction.
- Cutaneous diphtheria resulting in superficial ulcers with gray-brown membranes, difficult to distinguish from strep or staph infections.

A five-year-old female presented with a three-day history of fever, dysphagia, and respiratory difficulty, accompanied by neck swelling.
Physical examination revealed stridor and a grayish membrane on the tonsillopharyngeal wall.
Management strategies for carriers include Erythromycin or Benzathine Penicillin in unimmunized individuals.
Follow-up after two weeks is crucial for persistent carriers.

Transmitted through direct contact or inhalation of respiratory droplets.
Non-invasive diseases include otitis media, sinusitis, and conjunctivitis; invasive diseases include bacteremia and meningitis.
Other possible complications involve epiglottitis, pneumonia, cellulitis, and osteomyelitis.
Diagnostics include CS cultures.
First-line treatment involves Ampicillin or Ceftriaxone.

A sexually transmitted disease characterized by painful genital ulceration and lymphadenopathy.
Incubation period is typically 4-7 days.
Clinical manifestations include small inflammatory papules that evolve into pustular and ulcerative lesions.
Diagnosis based on clinical presentation and exclusion of syphilis and HSV.
Gram stain can show a “school of fish” appearance; culture sensitivity is around 80%.

A primary cause of septic arthritis, osteomyelitis, and spondylodiscitis in young children.
Produces RTX toxin damaging respiratory epithelial cells and promoting bacteremia.
Septic arthritis is the most common invasive disease caused by this pathogen.
Diagnosis entails blood cultures, bronchoscopy, or tissue biopsy if necessary.