Which organism is associated with infections in humans often linked to deli meats and improperly pasteurized dairy products?

• A. Bacillus subtilis
• B. Listeria monocytogenes
• C. Leuconostoc sp.
• D. Streptococcus agalactiae

Answer: (B)

Listeria monocytogenes is a foodborne pathogen classically tied to infections from ready-to-eat foods like deli meats and unpasteurized dairy products. It can grow at refrigeration temperatures, which means it can multiply in chilled foods that people assume are safe. In vulnerable groups—pregnant women, newborns, the elderly, and those with weakened immune systems—it can cause severe illness such as meningitis, bacteremia, and fetal or neonatal infection. The other organisms don’t have this same well-known link to deli meats and improperly pasteurized dairy: Bacillus subtilis is mainly a environmental, sometimes spoilage-associated bacterium; Leuconostoc species are lactic acid bacteria used in fermentation and can cause rare opportunistic infections but aren’t the classic deli-dairy pathogens; Streptococcus agalactiae (Group B Streptococcus) is associated with neonatal sepsis and maternal colonization, not with foodborne outbreaks from deli meats or pasteurized dairy.