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Increasing incidence of ampicillin resistance in Hemophilus influenzae
Abstract:
The incidence of ampicillin resistance in Hemophilus influenzae and its medical significance have not been extensively determined. During 1975-1977, we tested for ampicillin resistance 489 consecutive middle-ear isolates of HI obtained from children in Huntsville, Alabama, and 719 consecutive laboratory isolates of HI from Children's Hospital, Boston. The annual incidence of Amp resistance rose progressively in each survey, from initial values of 1.4 to 5.3% in 1975, to 14 to 16% in 1977 (P less than 0.05), a mean annual rate of increase approximately twofold. Resistance was equally prevalent among type b and non-b isolates and among nasally carried and disease-associated isolates (from blood, CSF, middle ears). Patients harboring AmpR isolates were much more likely to have had recent exposure to beta-lactam antibiotics (P less than 0.01).
Insights
Ampicillin resistance in Hemophilus influenzae increased significantly between 1975 and 1977. This rise in ampicillin resistance (AmpR) was linked to prior exposure to beta-lactam antibiotics.
Area of Science:
- Microbiology
- Infectious Diseases
- Antibiotic Resistance
Background:
- The medical significance and incidence of ampicillin resistance in Hemophilus influenzae remain incompletely understood.
- Hemophilus influenzae is a significant pathogen, particularly in pediatric respiratory infections.
Purpose of the Study:
- To determine the incidence and trends of ampicillin resistance in Hemophilus influenzae isolates.
- To investigate the association between ampicillin resistance and prior antibiotic exposure.
Main Methods:
- Prospective surveillance of middle-ear isolates from children in Huntsville, Alabama (1975-1977).
- Analysis of laboratory isolates from Children's Hospital, Boston (1975-1977).
- Testing for ampicillin resistance in Hemophilus influenzae.
Main Results:
- A progressive annual increase in ampicillin resistance was observed, rising from 1.4-5.3% in 1975 to 14-16% in 1977.
- The rate of increase in resistance was approximately twofold annually.
- Ampicillin resistance was consistent across different Hemophilus influenzae serotypes (b and non-b) and isolation sources (nasal, middle ear, blood, CSF).
- Patients with ampicillin-resistant isolates showed a significantly higher likelihood of recent beta-lactam antibiotic exposure (P < 0.01).
Conclusions:
- Ampicillin resistance in Hemophilus influenzae demonstrated a substantial and concerning upward trend during the study period.
- Recent exposure to beta-lactam antibiotics is a significant risk factor for infection with ampicillin-resistant Hemophilus influenzae.
- Continued surveillance of antibiotic resistance patterns is crucial for guiding clinical treatment strategies.