53 - Gram-Negative Bacterial Infections

Abstract

•First Described: Gram-negative bacteria were first described in Berlin by the Danish scientist Hans Christian Gram in 1884 when he used Gram stain to visualize Klebsiella pneumoniae in the lungs of people who died of pneumonia.1•Causes: Examples include Escherichia coli, Salmonella, Enterobacter, Citrobacter, Klebsiella, Campylobacter, Pseudomonas, and Acinetobacter.•Geographic Distribution: Worldwide.•Mode of Transmission: Direct contact or contact with contaminated fomites; the bacteria often invade opportunistically.•Major Clinical Signs: Affected sites include UTIs, wound infections, pneumonia, pyothorax, peritonitis, pyometra, ocular surface infections, otitis externa, pyoderma, bacteremia, and endocarditis, but virtually any body system can be affected.•Differential Diagnoses: Infections with gram-positive bacteria such as Staphylococcus spp. and Streptococcus spp.; to a lesser extent, infections with nonbacterial pathogens such as fungi.•Human Health Significance: Gram-negative bacteria shed by dogs and cats have the potential to colonize humans, especially those with impaired host defenses. They may also be responsible for infections of dog or cat bites. Infections caused by gram-negative pathogens resistant to all available antibiotics have resulted in the death of human patients.