Hospital Acquired Infections
Pseudomonas Aeruginosa
Obligate aerobe. Appears as smooth round colonies with green-blue coloration. Oxidase positive. Antibiotics can alter the microbiome and allow P. Aeruginosa to colonize opportunistically.
Is generally present in water and is common in hospital-acquired infections. They are especially common in devices which disrupt host barriers, like ventilators or catheters. They are treated with higher doses of antibiotics as it has several virulence factors.
Virulence factors
- Pili and flagella: Attachment to host cells
- Secretion systems: Inflammation and tissue injury
- Endotoxin (LPS): Resists innate host defenses
- Pyocyanin (pigment toxin): Tissue damage
- Quorum-sensing molecules: Facilitate cell-to-cell communication
Symptoms
- Bacteremia
- Infective endocarditis
- Pneumonia
- Bone and joint infections
- Skin and soft tissue infections (e.g., swimmers ear, malignant otitis externa)
- Eye infections (keratitis, endophthalmitis)
Antibiotics resistance
Intrinsic resistance
- Decreased permeability of the membrane
- Efflux pumps
- Anti-microbial-modifying enzymes
Acquired resistance
Can be transmitted through mobile genetic elements (plasmids, transposons, integrins) which carry extended-spectrum beta-lactamases, carbapenemases, and aminoglycoside-modifying enzymes.
Mutations can lead to multiple drug efflux pumps and downregulation of outer membrane protein, OprD, which is a carbapenem-specific porin.
Acinetobacter baumanii
Aerobic, non-motile, catalase-positive, oxidase-negative, gram-negative coccobacillus.
Pro tip: "cine" means motion. Therefore "acine" means no motion.
Naturally inhabit water an soil and can survive in iron limited host environments. They can form biofilms on mucosal surfaces and medical devices.
Antibiotics resistance
In addition to below, can also acquire foreign genetic material to enhance survival and increase resistance to antimicrobial agents.
Intrinsic resistance
- Decreased permeability of the membrane
- Efflux pumps
- Anti-microbial-modifying enzymes
Acquired resistance
Can be transmitted through mobile genetic elements (plasmids, transposons, integrins) which carry extended-spectrum beta-lactamases, carbapenemases, and aminoglycoside-modifying enzymes.
Mutations can lead to multiple drug efflux pumps and downregulation of outer membrane protein, OprD, which is a carbapenem-specific porin.
Stenotrophomonas maltophilia
Aerobe, oxidase-negative, catalase-positive, gram-negative, bacillus
Antibiotic resistance
Inherent resistance to most beta-lactams, aminoglycosides, and various disinfectants. For this reason, it is hard to know the best antibiotic to use. Trimethoprim-sulfamethoxazole (SMX-TMP) is generally the drug of choice here.
Burkholderia cepacia complex
This is a bunch of distinct species which look similar. They can bind various epithelial cell receptors.
B. cenocepacia and B. multivorans are the most common species. Risk factor for cystic fibrosis.