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A nosocomial outbreak of ampicillin-resistant Haemophilus influenzae type b in a geriatric unit
J E Patterson1, G M Madden, E P Krisiunas
1Section of Infectious Diseases and Epidemiology, St. Francis Hospital and Medical Center, Hartford, Connecticut.
Abstract:
A nosocomial outbreak of Haemophilus influenzae type b (Hib) bronchitis occurred in a geriatric unit. The three infected patients were grouped together in an isolation unit and treated. A prevalence survey was done by obtaining pharyngeal cultures from patients and staff in the unit. One patient and a nurse were asymptomatic pharyngeal carriers of Hib. One infected patient was bedridden, and his only known Hib contact was the nurse. Geographic clustering was the only significant risk factor, as determined by a case-control study. Carriers were treated with rifampin. The isolates were characterized for strain relatedness by using three methods. All produced beta-lactamase and all were serotype b. Plasmid profiles and restriction endonuclease analysis of bacterial DNA were performed; chromosomes were digested with the restriction endonucleases HindIII and HaeIII. Strains were confirmed as identical by using these methods and were different from two Hib control strains producing beta-lactamase. This study documents nosocomial transmission of Hib, by using molecular typing methods.
Insights
A nosocomial outbreak of Haemophilus influenzae type b (Hib) bronchitis in a geriatric unit was investigated. Molecular typing confirmed nosocomial transmission, identifying geographic clustering and asymptomatic carriers as key factors.
Area of Science:
- Infectious Diseases
- Epidemiology
- Microbiology
Background:
- Nosocomial outbreaks of Haemophilus influenzae type b (Hib) can occur in healthcare settings.
- Geriatric units may be particularly vulnerable due to patient factors.
Purpose of the Study:
- To investigate a nosocomial outbreak of Hib bronchitis in a geriatric unit.
- To identify risk factors and transmission routes of Hib in this setting.
- To characterize the implicated Hib strains using molecular methods.
Main Methods:
- A case-control study was conducted to identify risk factors.
- Prevalence survey using pharyngeal cultures for patients and staff.
- Molecular typing of Hib isolates including plasmid profiling and DNA restriction endonuclease analysis.
Main Results:
- Three patients were infected with Hib bronchitis; two were asymptomatic carriers (one patient, one nurse).
- Geographic clustering was the only significant risk factor identified.
- Molecular typing confirmed all outbreak strains were identical, beta-lactamase-producing, serotype b, and distinct from control strains.
Conclusions:
- This study documents nosocomial transmission of Hib in a geriatric unit.
- Asymptomatic carriers and geographic proximity played roles in transmission.
- Molecular typing is crucial for confirming nosocomial spread of Hib.