Gram-negative Bacteria Infections in Healthcare Settings

General Information about gram-negative bacteria

Gram-negative bacteria cause infections including pneumonia, bloodstream infections, wound or surgical site infections, and meningitis in healthcare settings. Gram-negative bacteria are resistant to multiple drugs and are increasingly resistant to most available antibiotics. These bacteria have built-in abilities to find new ways to be resistant and can pass along genetic materials that allow other bacteria to become drug-resistant as well. CDC’s aggressive recommendations, if implemented, can prevent the spread of gram-negatives.

Gram-negative infections include those caused by Klebsiella, Acinetobacter, Pseudomonas aeruginosa, and E. coli., as well as many other less common bacteria.

Outbreak investigations

Outbreak investigations have led to a better understanding of how to control these bacteria in healthcare. In the past 3 years, the Division of Healthcare Quality Promotion has assisted in at least 10 investigations of outbreaks of gram negative infections.

  • CDC has collaborated with state health departments in Maryland and Arizona to successfully control outbreaks of Multidrug-resistant-Acinetobacter infections occurring among intensive care unit patients.
  • CDC has worked with the Puerto Rico health department to control an outbreak of highly resistant Klebsiella at a neonatal intensive-care unit in Puerto Rico.
  • CDC assisted the Ohio health department’s investigation of infections caused by Acinetobacter. These outbreaks have occurred in various healthcare facilities in the state of Ohio and have been controlled by aggressive infection control interventions.
  • CDC worked with the state health department of Texas on separate outbreaks of B. cepacia and Pseudomonas.
  • Additionally, CDC worked with the state health department in Georgia on an unrelated outbreak of B. cepacia.
  • CDC worked with the Department of Defense to investigate and control Acinetobacter infections occurring in soldiers injured in the Middle East. This collaboration led to important improvements in infection control in military medical facilities.
  • In addition to these outbreaks, CDC’s reference laboratory has confirmed carbapenemase resistance in bacteria for 32 other U.S. states.

Laboratory tests for detecting resistance

  • CDC is collaborating with laboratory standards-setting institutions to identify and recommend laboratory tests for the accurate detection of carbapenemase-mediated resistance.  
  • CDC is working with states to identify isolates with unusual resistance and to determine new mechanisms of resistance among multidrug-resistant gram-negatives, including the recent identification of a new mechanism of resistance in patients returning from Asia.

Monitoring gram-negative healthcare-associated infections

  • CDC’s National Healthcare Safety Network (NHSN) captures information on antibiotic resistance patterns in gram-negative bacteria in healthcare settings.
  • The percentage of gram-negatives that are resistant to drugs is increasing.
  • In 2008, based on NHSN data, 13% of E. coli and Klebsiella, 17% of P. aeruginosa and 74% of A. baumannii in intensive-care units were multidrug-resistant.