Nosocomial outbreaks due to Ab have been reported with increasing frequency over the past few years. During the first 7 months of 1993 a 3 fold increase in the respiratory isolations of Ab were noted in 5 ICUs of a tertiary referral hospital. A total of 107 Ab colonized/infected respiratory sites were noted in 140 patients based on total hospital microbiologic surveillance of which 98(91.6%) were from the ICUs. ICU respiratory isolates represented 56% of total hospital Ab isolates. Of the 98 respiratory ICU isolates 43(43.8%) were from cases of nosocomial pneumonia. Typing was done on 100 Ab isolates (40 ICU, 34 environmental and handwashing, 15 ward and 11 others). PFGE identified 18 different types whereas antibiogram identified 8 types. Of 31 respiratory tract ICU Ab and 33 environmental ICU Ab, 29(93.5%) and 29(87.9%) respectively were of a single concordant PFGE pattern. Of the concordant isolates antibiograms were concordant in Only 75% (22/29) and 86%(25/29) of instances respectively. We conclude that a single predominant strain of Ab was associated with this multiple ICU outbreak and that PFGE was the most useful typing method for differentiation of strains.
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