Acinetobacter Before we begin the investigation, we must prepare for field work. The preparation requires that we learn about the organism involved in the outbreak. So prior to going to the hospital, I did some reading about Acinetobacter. This is what I found.

Gram negative coccobacillus Frequently arranged in pairs Oxidase negative Nitrate negative Catalase positive Nonfermentative Nonmotile Strictly aerobic Gram negative coccobacillus Sometimes difficult to decolorize Frequently arranged in pairs Bergogne-Bérézin E, Towner KJ. Clin Microbiol Rev 1996;9:148-165.

Acinetobacter background Non-motile gram negative coccobacillus Often mistaken for staph on bad gram stain A colonizer of skin & mucosa in the tropics, but not temperate climates Increased cases in summer perhaps biofilm bloom in tapwater

Acinetobacter species and demographics baumannii N = 110 other species N = 90 age mean median 51 53 58 male 53% 60% hospital* >48 hr 76% 57% speciality* surgery ICU haem/oncol medicine 21% 20% 15% 8% 10% 2% 24% 18% infection focus unknown 40% 35% 49% 32% species

Microbiology Ubiquitous: Survive on moist & dry surfaces 32 species Widely distributed in nature (soil, water, food, sewage) & the hospital environment Survive on moist & dry surfaces 32 species >2/3 of Acinetobacter infections are due to A. baumannii Highly antibiotic resistant One of the things that makes this organism so problematic is its widespread presence in the environment and its ability to survive in the hospital environment. Acinetobacter has been cultured from dry surfaces in a patient room more than 9 days after an infected patient was discharged from the room. Most of the Acinetobacter infections are due to the Acinetobacter baumannii.In addition, it readily acquires antibiotic resistance, even in the same patient.

Major infections due to Acinetobacter Ventilator-associated pneumonia Urinary tract Bloodstream infection Skin/wound infections Endocarditis Peritonitis Acinetobacter most commonly causes pneumonia, particularly ventilator-associated pneumonia. However, it has also been cultured from blood, urine, and wounds. It may less frequently cause meningitis, peritonitis, or endocarditis.

Acinetobacter Ventilator-Associated Pneumonia Acinetobacter accounts for 5-25% of all cases of VAP Risk factors: Advanced age Surgery Use of antimicrobial agents Invasive devices Prolonged ICU stay Some of the factors associated with previous outbreaks of Acinetobacter-associated pneumonia include one or multiple surgeries, patient requirement for multiple antibiotics, the use of devices such as central venous lines or arterial lines, and a long stay in the intensive care unit, such as with a critically ill trauma patient.

Acinetobacter on Gram stain

Source of A. baumanii Nosocomial Bloodstream Infection Abdominal infection 19% The respiratory tract is an important reservoir for Acinetobacter bloodstream infections Central venous line 8% Respiratory tract 71%

Inflammatory Response to A. baumanii Nosocomial Bloodstream Infection Severe sepsis 21% Septic shock 24% Sepsis 55%

Opportunities for cross transmission are multiple

Preventing Acinetobacter Transmission in the ICU General Measures Hand hygiene Use of alcohol-based hand sanitizers Contact precautions Gowns/gloves Dedicate non-critical devices to patient room Environmental decontamination Prudent use of antibiotics Avoidance of transfer of patients to Burn Unit from other ICUs

Preventing Acinetobacter Transmission in the ICU Outbreak Interventions Hand cultures Surveillance cultures Environmental cultures following terminal disinfection to document cleaning efficacy Cohorting Ask laboratory to save all isolates for molecular typing Healthcare worker education If transmission continues despite above interventions, closure of unit to new admissions

Summary Although commonly found on the skin of healthy humans, Acinetobacter plays the role of an opportunistic pathogen in the critically ill patient High level of antibiotic resistance makes it well suited as a pathogen in areas with high use of antibiotics (e.g., ICU setting) Control requires good hand hygiene, barrier precautions & environmental decontamination Alcohol-based products containing chlorhexidine should be considered the hand hygiene agents of choice

Oxidation-fermentation Hugh-Leifson - Uninoculated

OF glucose oxidative metabolism

OFglucose fermentative metabolism (Enlarged view)

Identification characteristics of Acinetobacter baumanni (Unknown)

Reaction Test - Oxidase K/K KIA TSI + Growth on MAC Motility OF-glucose OF-lactose Urea Growth at 42 C Nitrate Hemolysis Arginine Malonate Gelatin hydrolysis