Dg. De Viedma et al., Heterogeneous antimicrobial resistance patterns in polyclonal populations of coagulase-negative staphylococci isolated from catheters, J CLIN MICR, 38(4), 2000, pp. 1359-1363
Most cases of nosocomial bacteremia are catheter related, and coagulase-neg
ative staphylococci (CoNS) are the microorganisms most frequently associate
d with these infections. Subtle morphological differences are frequently fo
und among CoNS colonies cultured from infected catheters. The aim of this s
tudy was to analyze the significance of the morphological heterogeneity obs
erved in these CoNS populations. With this purpose in mind? the clonal comp
osition of the CoNS populations obtained from a selection of nine catheters
,vas analyzed by two different molecular techniques, arbitrarily primed-PCR
and DNA macrorestriction analysis by pulsed-field gel electrophoresis, Twe
nty CoNS morphotypes were included for analysis, and four single colonies r
epresentative of each morphotype were selected. Morphological differences b
etween colonies mere found to correlate in all cases with differences at th
e molecular level. Unique fingerprints were also obtained for some isolates
which mere indistinguishable from other representatives of the same morpho
types, Differences in the molecular patterns among the isolates were associ
ated in most of the cases with differences in the antimicrobial susceptibil
ity patterns. The frequent isolation of polyclonal CoNS populations from ca
theters, with heterogeneous antimicrobial susceptibility patterns, has rele
vant epidemiologic and therapeutic implications in the contest of catheter-
related infections.