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Letter
Extended-spectrum β-Lactamase-producing
Flora in Healthy Persons
Camilla Rodrigues,*
Upasana Shukla,* Simantini Jog,* and Ajita Mehta*
*P.D. Hinduja National Hospital and Medicine Research Centre, Mumbai,
India
Suggested
citation for this article
To the Editor: Extended-spectrum β-lactamase (ESBL)–producing
gram-negative bacilli are endemic in hospitals. In intensive care units,
2% prevalence of ESBL-producing organisms has been reported (1).
Exceedingly high rates of ESBL-producing bacteria in Indian hospitals
prompted us to look at the fecal carriage of ESBL in the community (2).
One hundred healthy executives received a comprehensive health check
at our tertiary care center in central Mumbai from August to September
2004. The predominant isolates from stool samples obtained for routine
examination were cultured, and initial screening for ESBL production was
conducted by using the disk diffusion method according to NCCLS guidelines
(3). For these isolates, the ESBL phenotypic confirmation
was performed with ceftazidime-clavulanate for an increase in zone diameter
by 5 mm (disk potentiation). In addition, the ATB BLSE strip (bioMérieux,
Lyon, France) was used to confirm the presence of inhibitor (sulbactam)-susceptible
enzymes and to differentiate the strains from those that were either inhibitor
resistant or harboring other β-lactamases, such as those of AmpC
derivation. The ATB BLSE strip consists of a varying concentration of
ceftazidime, 0.5–32 mg/L, and aztreonam, 0.5–8 mg/L, with varying combinations
of these agents with a β-lactamase inhibitor, i.e., + sulbactam,
0.06–1 mg/L. Cefotetan (4 and 32 mg/L) and imipenem (4 and 8 mg/L) were
also included in the strip. The test was considered positive when a variation
of ≥4 dilutions was observed between the antimicrobial agent tested
alone and the agent combined with the inhibitor. Eleven of the 100 samples
screened were positive for ESBL-producing Escherichia coli and
Klebsiella pneumoniae. Seven of the 11 were confirmed by using
the ATB BLSE strip. The MIC of ceftazidime and aztreonam in all 7 isolates
was 8 μg/mL. We might be underreporting ESBL producers in these cases
by not including the cefotaxime-clavulanate combination in addition to
the ceftazidime-clavulanate concentration. The percentage resistance to
ciprofloxacin was 45%. All isolates were susceptible to amikacin and the
carbapenems. None of the executives gave a history of hospitalization
in the last year or history of antimicrobial drug consumption in the last
6 months.
This trend in patients with no apparent risk factors for ESBL carriage
calls for urgent attention. Unknown environmental factors are likely playing
a key role in maintaining this selective pressure. Larger studies are
required to substantiate these findings.
References
- Harris AD, Nemoy L, Johnson J, Carnahan M, Smith DJ,
Standiford H, et al. Co-carriage
rates of vancomycin resistant Enterococcus and extended spectrum
β-lactamases–producing bacteria among a cohort of intensive care
unit patients—implications for an active surveillance program. Infect
Control Hosp Epidemiol. 2004;25:105–8.
- Mathai D, Rhomberg PR, Biendenbach DJ, Jones RN, India Antimicrobial
Resistance Study Group. Evaluation
of the in vitro activity of six broad spectrum β–lactam antimicrobial
agents tested against recent clinical isolates from India: a survey
of ten medical center laboratories. Diagn Microbiol Infect Dis.
2002;44:367–77.
- National Committee for Clinical Laboratory Standards. Performance
standards for antimicrobial susceptibility testing, 12th Informational
Supplement; M100-S12 Wayne (PA): The Committee; 2002. p. 46.
Suggested citation
for this article:
Rodrigues C, Shukla
U, Jog S, Mehta A. Extended-spectrum β-lactamase-producing flora
in healthy persons [letter]. Emerg Infect Dis [serial on the Internet].
2005 Jun [date cited]. Available from http://www.cdc.gov/ncidod/EID/vol11no06/04-1111.htm
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