Sketchy Microbiology

Streptococcus mutans

• Gram-positive, catalase-negative, alpha-hemolytic bacteria; non-encapsulated and optochin resistant.
• Reservoir found in the human oropharynx as normal flora; transmission is endogenous.
• Causes dental caries through dextran-mediated adherence of oral flora, forming plaque.
• Infective endocarditis can occur, presenting symptoms include malaise, anorexia, night sweats, and weight loss; risks include damaged heart valves and poor dental hygiene.
• Treatment involves penicillin G with aminoglycosides; prophylactic antibiotics recommended before dental work for high-risk patients.

Enterococcus (Group D Strep)

• Includes species Faecalis (common) and Faecium (more dangerous); gram-positive, catalase-negative, PYR positive, cocci in chains.
• Reservoirs include the human colon, urethra, and female genital tract; endogenous transmission.
• Associated diseases involve chronic necrotizing infection and Wool Sorter's Disease, a severe pneumonia.
• Diagnosed through Gram stain and culture; treatment includes fluoroquinolones or doxycycline, and vaccination is recommended for high-risk occupations.

Bacillus cereus

• Found in nature and primarily transmitted through foodborne intoxication, often linked to improperly handled fried rice.
• Pathogenesis includes emetic and diarrheal toxins leading to rapid vomiting and diarrhea.
• Diagnosis typically involves identifying intracellular gram-negative diplococci in neutrophils; treatment requires ceftriaxone while considering co-infection.

Enterobacteria (Enterobacter cloacae, Serratia marcescens, Klebsiella pneumoniae)

• All are gram-negative, lactose fermenters that appear as pink colonies on MacConkey agar, multi-drug resistant, causing pneumonia and UTIs.
• Enterobacter and Serratia are motile; Serratia produces a characteristic red pigment.
• Klebsiella pneumonia is nonmotile with a large capsule, notably associated with alcoholism, chronic lung disease, and aspiration pneumonia.
• Diagnosis is through culture from sputum or urine; treatment usually includes third-generation cephalosporins with consideration for aminoglycosides.

Salmonella

• Gram-negative rods, enterobacteriaceae, non-lactose fermenting, motile, and H2S producing.
• Salmonella typhi treatment includes fluid replacement and antibiotics like doxycycline or ciprofloxacin; proper sanitation helps prevent infection.

Helicobacter pylori

• Gram-negative, spiral-shaped, motile bacilli with urease positivity, commonly residing in the stomach near the pylorus.
• Transmission occurs via fecal-oral or oral-oral routes; associated with chronic gastritis and duodenal ulcers, and linked to stomach cancer.
• Diagnosis through serodiagnosis, treatment with antibiotics such as amoxicillin or clarithromycin.

Lyme Disease (Borrelia burgdorferi)

• The leading tick-borne disease in the U.S., presenting in three stages: early localized, early disseminated, and late persistent.
• Stage 1 includes flu-like symptoms and a characteristic "bull's eye" rash.
• Stage 2 encompasses heart and neurological issues; stage 3 involves severe fatigue and migratory arthritis.
• Diagnosis via ELISA and confirmation with Western blot; treatment typically includes doxycycline.

Leptospira interrogans

• Spirochetes with a question mark shape transmitted through contact with contaminated water, causing potential severe infections.
• Reservoir includes wild and domestic animals; notable symptoms may involve skeletal deformities and dental anomalies.

Chlamydia trachomatis

• Obligate intracellular bacteria common in human genital tracts, transmitted sexually and perinatally.
• Associated with various STDs, notable for causing watery discharge and pelvic inflammatory disease, as well as conjunctivitis and pneumonia in neonates.
• Diagnosis made through cytoplasmic inclusions via various staining methods; treated with antibiotics like doxycycline.