Drug–resistant Acinetobacter baumannii is a gram-negative bacteria found primarily in hospital settings, where it frequently colonizes the IV and catheter lines of ICU patients. Due to Acinetobacter’s low virulence, colonized patients rarely experience nosocomial infections related to organ systems where medical equipment is used (i.e. Ventilator-associated pneumonia). In the outpatient setting, the pathogen has been associated with wound infections among soldiers or community-acquired pneumonia among alcoholics.

These maps show combined inpatient resistance to imipenem, a broad-spectrum carbapenem antibiotic considered to be of last resort in most other infections. Due to A. baumannii’s inherent resistance against most antibiotics, carbapenems are frequently the first and only line of treatment.

In the first half of the decade, nearly all census divisions report low resistance rates of under 10% with higher levels in the Mid-Atlantic states. Rates climb particularly steeply in the latter part of the decade, with different regions experiencing sudden increases between the years. Overall, resistance remains low only in the New England and East South Central divisions. Four out of nine regions experience rates over 50% at some point, with East North Central seeing two consecutive years of growing resistance that surpasses 60% in 2009.

The rates reported here are very close to a published analysis of the same data by ETC researchers spanning the 1999-2006 period. The three additional years of susceptibility data reveal a striking increase of national rates, which roughly doubled from around 19% in 2006 to 39% in 2009. Despite the increase, the 23% we report for 2007 is significantly lower than the 29%-36% range found in the 2006-2007 National Healthcare Safety Network (NHSN). However, the latter source is based on fewer than 500 samples of patients with nosocomial (hospital-acquired) infections. The rapid gains in resistance coincides with the start of overseas military operations in 2002, and in light of the link between drug-resistant strains of the bacteria and war trauma, this suggests returning troops are a likely factor in the observed increase.

The worrisome decline in carbapenem effectiveness points to two major conclusions: one is the urgent need for developing new drugs active against gram-negative bacteria; two, the medical community needs to evaluate the impact of large-scale vaccination of populations most affected by A. baumannii such as military personnel and those in contact with them.

The national average resistance level for the sample was 17.2 %, rising from 4.6% in 2000 to 38.9% in 2009.

The sample consists of 63,551 A. baumannii inpatient isolates tested for imipenem resistance. Due to the rare occurrence of the pathogen, the sample size is considerably lower than for our other outpatient videos; Data is not available from the following states: AL (2009), AR (2007-2009), AZ (2000, 2005), CO (2001-2002, 2005-2009), GA (2007-2009), IN (2006-2010), IA (2000, 2002, 2008-2009), KY (2007-2009), ME (2000-2003, 2008), MD (2000, 2001), MS (2008-2009), NV (2008-2009), RI (2000-2005), SD (2000-2002, 2004-2009), TN (2007-2008), UT (2007-2009), AK, CT, HI, ID, MT, NH and WY. No states in the East South Central region submitted data for 2009.