From the Guidelines
Gram-negative diplococci are most commonly associated with Neisseria gonorrhoeae and Neisseria meningitidis, which are the most clinically significant organisms in this category. These bacteria appear as pairs (diplococci) under microscopic examination and do not retain crystal violet dye during Gram staining, instead appearing pink or red 1.
Key Organisms
- Neisseria gonorrhoeae causes gonorrhea, a sexually transmitted infection affecting the genitourinary tract, rectum, and occasionally the throat and eyes.
- Neisseria meningitidis can cause meningococcal meningitis and septicemia, which are serious and potentially fatal infections 1.
Other Gram-Negative Diplococci
Other gram-negative diplococci include Moraxella catarrhalis, which can cause respiratory infections, and some species of Acinetobacter. These organisms have a distinctive cell wall structure with a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides, which contributes to their gram-negative staining properties and affects their susceptibility to antibiotics 1.
Clinical Implications
Proper identification of these organisms is crucial for appropriate treatment, as they have different antibiotic susceptibility patterns and clinical implications. For example, Neisseria gonorrhoeae is usually susceptible to penicillin, while Neisseria meningitidis may require different treatment approaches depending on the specific strain and antibiotic resistance patterns 1.
Treatment Approaches
Treatment of infections caused by gram-negative diplococci should be individualized based on the specific organism, antibiotic susceptibility testing, and clinical presentation. In general, antibiotics such as ceftriaxone or other third-generation cephalosporins may be effective against Neisseria gonorrhoeae and Neisseria meningitidis, while other gram-negative diplococci may require different treatment approaches 1.
From the Research
Gram-Negative Diplococci Organisms
- Neisseria meningitidis is a gram-negative diplococcus and a transient commensal of the human nasopharynx 2
- Other Neisseria species, including N. lactamica, N. cinerea, and N. mucosa, are also gram-negative diplococci that share the same niche as N. meningitidis 2
- Moraxella catarrhalis is another gram-negative diplococcus that can cause respiratory tract infections 3
- Neisseria gonorrhoeae is a closely related gram-negative diplococcus that causes gonorrhea 4
Characteristics of Gram-Negative Diplococci
- Gram-negative diplococci are typically oxidase-positive and have a specific cellular fatty acid profile 5
- They can be distinguished from other bacteria by their morphology, biochemical tests, and 16S rRNA gene sequencing 5
- Neisseria meningitidis and other gram-negative diplococci have specific adhesins, virulence factors, and phase variable genes that enable them to colonize the human host 6