The second outbreak occurred in September 2010 in eight
ICU patients. New MRAB infections included six cases of
pneumonia, and one patient each with UTI and SSI, respectively.
Overall, 60% of pneumonia cases were associated with
mechanical ventilation (MV), with a mean length of MV before
onset of 15 days. After recognizing the second outbreak in
September 2010, the aforementioned decontamination
procedures were repeated (17 October 2010). From October
2010 to October 2011 no MRAB were isolated from clinical
samples (Figure 1).
None of the patients who had been hospitalized in one of the
ICUs in the previous year was re-hospitalized, and patients in
2010 had no reported contact with patients from the previous
year. The two units studied were located in separate parts of
the hospital and patients were not transferred between them.
However, physicians, anaesthetists, nurses, support staff and
physiotherapists were working in both ICUs.
Total cumulative incidence of all infections was 6.5 per 100
admissions and the total incidence density was 23.9 per 1000
patient-days in the study period (in 2009/2010). The mean
length of ICU stay was 2.7 days. The incidence of MRAB pneumonia
in 2009/2010 was 3.6 per 1000 admissions (epidemic
level) as compared with the baseline of 1.3 pneumonias per 1000
admissions (risk ratio: 2.8) in 2008 (endemic level). BSI incidence
reached 0.6 per 1000 admissions whereas in 2008 there
were no such cases reported. Altogether eight patients died,
giving a crude mortality rate of 27.6%. The mean age of patients
with MRAB infection was 66 years and was equal to the median
age. The mean number of days between admission to the ICU
and the first MRAB-positive culture was 23 days (median: 18).
The proportion of female patients was 25.8%. Out of 28 isolates
collected in 2009 and 2010 from 28 patients, 26 were from
symptomatic infections and two represented colonization
(Table I). A. baumannii was not cultured from the environment.
All A. baumannii isolates investigated were resistant to
ciprofloxacin and gentamicin but remained susceptible or
intermediate to tigecycline. Only one isolate was susceptible
to amikacin. The percentages of isolates susceptible and/or
intermediate to ampicillinesulbactam and tobramycin were
50% (14 isolates) and 32.1% (9 isolates), respectively. Twentyone
of 28 isolates (75%) were resistant to carbapenems,
whereas seven isolates were susceptible or intermediate to
imipenem (25%) and six isolates to meropenem (21.4%)
(Table I).