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[Ampicillin-sulbactam activity against respiratory isolates of Haemophilus influenzae]
R Cisterna1, M J Fresnadillo, J A García-Rodríguez
1Servicios de Microbiología, Hospital de Basurto, Bilbao.
Abstract:
A study was conducted on the in vitro activity of ampicillin/sulbactam against 100 respiratory strains of Haemophilus influenzae (45 betalactamase positive and 55 betalactamase negative strains) simultaneously isolated during 1997 in 6 Spanish hospitals: Hospital Clínico San Carlos (Madrid), Hospital de Cruces de Basurto (Bilbao), Hospital La Fe (Valencia), Hospital Virgen Macarena (Seville), Hospital de Bellvitge (Barcelona) and Hospital Clínico Universitario (Salamanca). It was studied in comparison to amoxicillin, amoxicillin/clavulanic acid, cefuroxime, clarithromycin and ciprofloxacin. The MIC breakpoints used for the interpretation of data were those published by the National Committee for Clinical Laboratory Standards in 1997. All of the strains tested were susceptible to ampicillin/sulbactam, amoxicillin/clavulanic acid, cefuroxime and ciprofloxacin. The rate of resistance to clarithromycin was 55.5% for betalactamase positive strains and 38. 2% for betalactamase negative strains. A total of 23.6% of the betalactamase negative strains were resistant or showed intermediate susceptibility to amoxicillin but were susceptible to betalactam/betalactamase inhibitor combinations and cefuroxime.
Insights
Ampicillin/sulbactam demonstrated excellent in vitro activity against Haemophilus influenzae respiratory strains. All tested strains were susceptible, highlighting its efficacy compared to other antibiotics.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Respiratory tract infections caused by Haemophilus influenzae are a significant public health concern.
- Antibiotic resistance in H. influenzae necessitates ongoing surveillance and evaluation of therapeutic options.
- Beta-lactamase production is a primary mechanism of resistance in H. influenzae.
Purpose of the Study:
- To evaluate the in vitro activity of ampicillin/sulbactam against contemporary respiratory isolates of Haemophilus influenzae.
- To compare the efficacy of ampicillin/sulbactam with other commonly used antibiotics, including amoxicillin, amoxicillin/clavulanic acid, cefuroxime, clarithromycin, and ciprofloxacin.
- To assess the impact of beta-lactamase production on antibiotic susceptibility patterns.
Main Methods:
- Antimicrobial susceptibility testing was performed on 100 respiratory strains of Haemophilus influenzae isolated from six Spanish hospitals in 1997.
- Strains were categorized as either beta-lactamase positive (n=45) or beta-lactamase negative (n=55).
- Minimum Inhibitory Concentrations (MICs) were determined and interpreted using 1997 National Committee for Clinical Laboratory Standards (NCCLS) breakpoints.
Main Results:
- All 100 strains of Haemophilus influenzae were susceptible to ampicillin/sulbactam.
- High susceptibility rates were also observed for amoxicillin/clavulanic acid, cefuroxime, and ciprofloxacin.
- Clarithromycin exhibited significant resistance, with rates of 55.5% in beta-lactamase positive and 38.2% in beta-lactamase negative strains.
- A notable proportion (23.6%) of beta-lactamase negative strains showed resistance or intermediate susceptibility to amoxicillin but remained susceptible to beta-lactam/beta-lactamase inhibitor combinations and cefuroxime.
Conclusions:
- Ampicillin/sulbactam is a highly effective agent against contemporary Spanish isolates of Haemophilus influenzae, including beta-lactamase producing strains.
- Beta-lactam/beta-lactamase inhibitor combinations and cefuroxime represent valuable therapeutic options for H. influenzae infections, particularly in the context of amoxicillin resistance.
- The study underscores the importance of monitoring antibiotic resistance trends in H. influenzae to guide appropriate antimicrobial therapy.