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Susceptibility studies of multiply resistant Haemophilus influenzae isolated from pediatric patients and contacts
Abstract:
From February 1981 to December 1983, 225 strains were isolated from pediatric patients infected with Haemophilus influenzae. Forty-one strains were found to be resistant to ampicillin, chloramphenicol, and other antibiotics. They were isolated from 20 patients with invasive diseases (meningitis, 16; bacteremia, 4) and 21 with noninvasive diseases (otitis media, 19; conjunctivitis, 2). During this period, 44 patients with invasive diseases were seen (meningitis, 28; bacteremia, 16). Strains resistant to both ampicillin and chloramphenicol occurred in 45.4% of cerebrospinal fluid and blood isolates and in 51% of cerebrospinal fluid isolates only. In this group, individual resistance to ampicillin was 50%; chloramphenicol, 52.2%; tetracycline, 54.5%; and sulfamethoxazole-trimethoprim, 63.6%. No epidemiological relationship could be found among the patients. The presence of asymptomatic carriers was investigated in two nurseries and in eight family groups. From a total of 125 individuals studied, 80 were found to be colonized by H. influenzae, and 36 carried multiply resistant strains. From patients and carriers, 77 strains were found to be resistant to ampicillin, chloramphenicol, and other drugs; 39 belonged to type b (cerebrospinal fluid, 16; blood, 4; ear, 7; and nasopharynx, 12), and 38 were non-type b. The most frequent pattern of resistance was ampicillin-chloramphenicol-tetracycline-sulfamethoxazole-trimethoprim (94.8%), followed by ampicillin-chloramphenicol-tetracycline (3.9%). The disk diffusion method correctly predicted multiple resistance. The mean inhibition zone diameters were: ampicillin, 12.8 mm; chloramphenicol, 15.2 mm; tetracycline, 9.9 mm; and sulfamethoxazole-trimethoprim, 10.8 mm. These resistant strains were susceptible to cefotaxime, moxalactam, cefoperazone, cefuroxime, rifampin, and gentamicin. Our data suggest that in Spain the resistance of H. influenzae to ampicillin and chloramphenicol is endemic and that other effective therapeutic modalities are needed.
Insights
Multiple antibiotic resistance in Haemophilus influenzae is endemic in Spain, particularly ampicillin and chloramphenicol resistance. New therapeutic strategies are needed due to widespread resistance in both invasive and noninvasive pediatric infections.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Haemophilus influenzae is a significant cause of pediatric infections, including invasive diseases like meningitis and noninvasive conditions such as otitis media.
- Antibiotic resistance in H. influenzae poses a growing threat to effective treatment, necessitating ongoing surveillance and characterization of resistant strains.
Purpose of the Study:
- To investigate the prevalence and patterns of antibiotic resistance in Haemophilus influenzae strains isolated from pediatric patients in Spain.
- To assess the effectiveness of the disk diffusion method in predicting multiple drug resistance.
- To identify alternative therapeutic options for infections caused by resistant H. influenzae strains.
Main Methods:
- Isolation and characterization of Haemophilus influenzae strains from pediatric patients and carriers between February 1981 and December 1983.
- Antimicrobial susceptibility testing using the disk diffusion method to determine resistance patterns to ampicillin, chloramphenicol, tetracycline, and sulfamethoxazole-trimethoprim.
- Evaluation of susceptibility to newer antibiotics such as cefotaxime, moxalactam, cefoperazone, cefuroxime, rifampin, and gentamicin.
Main Results:
- Forty-one of 225 H. influenzae strains exhibited resistance to ampicillin, chloramphenicol, and other antibiotics.
- Resistant strains were isolated from both invasive (45.4% of CSF and blood isolates) and noninvasive pediatric infections.
- The most frequent resistance pattern was ampicillin-chloramphenicol-tetracycline-sulfamethoxazole-trimethoprim (94.8%).
- The disk diffusion method accurately predicted multiple drug resistance.
- Resistant strains remained susceptible to cefotaxime, moxalactam, cefoperazone, cefuroxime, rifampin, and gentamicin.
Conclusions:
- Antibiotic resistance, particularly to ampicillin and chloramphenicol, is endemic in Haemophilus influenzae in Spain.
- The high prevalence of multiply resistant strains underscores the need for alternative therapeutic agents.
- Continuous monitoring of antimicrobial resistance patterns is crucial for guiding clinical management of H. influenzae infections.