Pasteurella multocida is known to form part of the normal flora in the nasopharynx or gastrointestinal tract in many domestic and wild animals. Most human P multocida infections are soft tissue infections caused by dog or cat bites. Less commonly this bacterium is associated with infections affecting other organ systems of man. A case of fatal P multocida meningitis discovered at the necropsy of a 52 year old man is described. P multocida is an unusual causative agent of meningitis which tends to affect those at the extremes of age.
- Pasteurella multocida
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Pasteurella multocida is a non-spore forming, non-motile, Gram negative coccobacillus. It has been isolated from the respiratory tract and digestive system of domestic pets, livestock, and many wild animals. The carriage rate of the organism is believed to be up to 90% in cats and up to 66% in dogs.1 P multocida has been known to cause infections in humans, the most familiar being soft tissue infection following animal bites. However, this organism may affect a variety of systems causing serious disease.
A 52 year old man was found dead at home. No history of illness in the preceding days was available, there is no record of him seeking any medical attention. He had recently been under investigation for dyspepsia but otherwise had no medical history of serious illness. The subject lived with his brother, both reportedly in a state of serious self neglect. Their house was soiled with dog faeces throughout and their pet dog was in poor health.
The subject was a white male whose appearance was consistent with the stated age of 52 years. He was well nourished and there were no external marks, bites, or scratches. On internal examination a purulent meningitis was found. In particular the cranial vertex and base of brain were affected. A sample of meningeal pus was taken for subsequent culture. The brain was slightly swollen and there was generalised vascular congestion. No skull fractures were present.
The lungs were congested and mildly oedematous. A small thromboembolus was present in the right lower lobe pulmonary artery. There was no evidence of chronic respiratory disease. Mild coronary atherosclerosis and duodenitis were noted. There was no evidence of malignancy, and no other foci of infection were identified. The cause of death was declared to be purulent meningitis.
Postmortem culture of a swab of meningeal pus on chocolate blood agar produced a pure growth of colonies resembling Haemophilus spp within 24 hours. However, the isolate was identified on API 20 NE (Bio-Merieux Ltd) as Pasteurella multocida.
Pasteurellae were first observed in the blood of birds with fowl cholera in 1877. P multocida (“killer of many species”) was isolated by Pasteur as the causative agent of this disease in 1880. Human infection by P multocida was not recognised until some years later. The first case reported was described in 1913 by Brugnatelli.1 In this case the organism was isolated from the blood of a woman with puerperal fever.
P multocida is most commonly recognised as a cause of soft tissue infection secondary to animal bites. However, various infections have been described where this organism was the agent responsible, in particular affecting those with impaired immune defences and those at the extremes of age.1,2
P multocida meningitis is uncommon. Cases of P multocida meningitis have occurred following animal bites, scratches, and other animal contact. The organism has also been known to be transmitted through animal saliva without a bite having occurred.3 In some cases of infection, no known animal contact has been determined.1,4 Meningitis caused by this agent has also been reported following spread of the bacterium from infected wounds after craniofacial surgery.1 A few cases have occurred in neonates after infection related to maternal carriage of the organism in the genital tract.5
The subjects in whom P multocida meningitis most often occurs are at the extremes of age, being either elderly people or young infants. The typical case involves infants under the age of one year with a history of animal exposure, and cases in adults are unusual.1–5 Kumar et al, in a review of cases, found that 40% occurred in infants under one year. When post-traumatic and post-surgical cases were eliminated, 70% of adult cases occurred in people over 55 years of age.2
Mortality in P multocida meningitis is high. In the series by Kumar overall mortality was 30%, but was higher in the elderly—63% in patients over 60 years in age.2 In another series of 17 cases, seven of whom were adults, six patients died within 72 hours of hospital admission. Four of these six fatalities involved persons over 60 years of age.1
Diagnosis of this agent can be difficult, in that Gram staining of CSF will reveal a Gram negative coccobacillus. This results in the organism being confused with more common agents of meningitis such as N meningitidis and H influenzae. However, identification of P multocida is normally straightforward, although false positive antigen testing with latex particle agglutination tests has been reported.3
In conclusion, we have presented a case of meningitis caused by P multocida, causing a sudden death in the community. The subject was an adult with no evidence of recent animal bite or chronic debility, but who lived in squalor with obvious animal contamination of his environment. Cases such as this appear to be unusual. However, the high frequency of animal contacts and the relative rarity of such infections must indicate that the risk is low. The majority of infections are wound infections related to animal bites. P multocida meningitis is rare, particularly in the adult. However, it is a very serious condition with a high mortality. Therefore, where meningitis occurs in addition to a history of animal exposure, P multocida infection should be considered.
Acknowledgements to HM Coroner, Bolton, for the kind permission to report details of the above case.
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