dc.description.abstract | A laboratory investigation of lactose
positive enterobacteria isolated from neonates in the
course of several cases of gastroenteritis in a
nursery ward is described. During a period of 4
weeks, 30 neonates were involved and 5 of these died.
A stool sample was taken from each of the 30 neonates
regardless of their clinical status. Ten colonies of
lactose positive enterobacteria were obtained from
each neonate and identified as Escherichia coli (229
isolates) and Klebsiella pneumoniae (65 isolates).
Six strains were lost during laboratory handling.
The pathogenic potential of the strains was
examined using an enteropathogenic E. coli adherence
factor (EAF) DNA probe. Colony hybridization of DNA
from the 294 isolates was performed using the 1
megadalton radiolabelled EAF probe. The EAF probe
hybridized with DNA from 78 of the 229 E. coli
strains and with none of the DNA from K. pneumoniae
strains. The EAF probe positive strains were found in
13 neonates. Colony hybridization tests of DNA from
all the E. coli and K. pneumoniae strains using
alkaline phosphatase-labelled oligonucleotide probes
specific for enterotoxins LT and ST1 of E. coli gave
negative results.
There were 28 and 8 different plasmid
profile groups of E. coli and K. pneumoniae
(xiii)
respectively. A total of 78 strains of E. coli were
shown to belong to one particular plasmid profile
group possessing plasmids of molecular weight 65,
1.9, 1.7, and 1.4 megadaltons (MDa). All these
strains gave positive results with the EAF probe
which was shown to hybridize with the 65 MDa plasmid.
Seven of the EAF probe positive and 6 EAF
probe negative E. coli strains were further
characterized at Centers for Disease Control,
Atlanta, Georgia, USA. The 7"EAF probe positive
strains were found to be 0111:HNT (NT=Nontypable).
They adhered locally to HeLa cells, and did not
produce Vero cell cytotoxins. The 6 EAF probe
negative strains all belonged to serotypes other than
0111:HNT, and they neither adhered to HeLa cells nor
elaborated Vero cell cytotoxins.
Twenty neonates yielded pure cultures of
E. coli, 5 had Klebsiella pneumoniae only, while 5
were positive for both species. The case fatality
rates of neonates who harboured EAF probe positive
E. coli, EAF probe negative E. coli, and
K. pneumoniae were 30.8%, 7.7% and 0% respectively.
Both E. coli and K. pneumoniae strains were
resistant to most of the 16 antimicrobial agents
tested. In general there was no marked difference in
the antimicrobial susceptibility patterns of EAF
probe positive and EAF probe negative E. coli
strains. However, a lower percentage (10.3%) of the
(xiv)
EAF positive strains were resistant to gentamycin
than the EAF negative ones (39.7%). Seventy percent
of K. pneumoniae strains were resistant to gentamycin
as compared to 30% of E. coli strains. None of the
bacterial isolates examined was resistant to
cefatoxime, but the majority of the strains (64-99%)
were resistant to sulphonamides, trimethoprimsulfamethoxazole,
chloramphenicol, oxytetracycline,
erythromycin, penicillin, and ampicillin. A few
strains (1-18.5%) were resistant to cefazolin,
cefamandole, amikacin, nalidixan, and nitrofurantoin.
No correlation between plasmid profiles and
antibiotic resistance pattern was found. | en_US |