Characterisation of Hafnia alvei isolates from human clinical extra-intestinal specimens: haemagglutinins, serum resistance and siderophore synthesis

Abstract

Extra-intestinal Hafnia alvei isolates are rarely considered to be pathogenic. To investigate whether such strains are able to produce virulence factors, a total of 70 clinical H. alvei isolates was compared with clinical extra-intestinal isolates of other members of the enterobacterial tribe Klebsiellae (Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens). Whereas mannose-sensitive haemagglutination (MSHA) was less common in H. alvei (59%) than in K. pneumoniae (86%) and E. cloacae (89%) isolates, the incidences of mannose-resistant haemagglutination indicative of type 3 pili (MR/K-HA) and of serum resistance properties were not lower. All H. alvei strains secreted siderophores but, unlike the other enterobacterial species examined, the siderophore type was neither enterobactin nor aerobactin. Although the low pathogenicity of H. alvei isolates could not be attributed to any of the factors investigated, the mean number of factors expressed by each H. alvei isolate was signi®cantly lower than that expressed by K. pneumoniae and E. cloacae isolates but did not differ signi®cantly from that of S. marcescens. Based on these ®ndings, the low pathogenicity of H. alvei appears to be due to its low frequency of expression of virulence factors as compared with clinically signi®cant species such as K. pneumoniae and E. cloacae.

Clinical and Laboratory Diagnostic Characteristics and Cytotoxigenic Potential of Hafnia alvei and Hafnia paralvei Strains

“…This cytolytic toxin was found in many Hafnia isolates (Table 3). Very little is known regarding the pathogenicity or virulence characteristics of hafniae, although siderophores, resistance to complement-mediated lysis, and possession of type 1 and 3 fimbriae have been described (19). The intriguing aspect of the present finding is that the toxin is (15,20).…”

The Genus Hafnia : from Soup to Nuts

“…The siderophores of H. alvei can, however, take up ferric enterobactin and ferrichrome via an E. coli FepA-like outer membrane protein (119). Other factors described for hafniae, which may or may not play a role in their pathogenicity, include mannose-sensitive and mannose-resistant (MR/K, type 3 fimbria) hemagglutinins (102). Enzymatic properties associated with some pathogenic bacteria, including hemolysin, protease, elastase, and lecithinase activities, have not been detected in hafniae (71).…”

“…Iron-scavenging mechanisms can also play important roles in pathogenesis. H. alvei strains produce siderophores as detected by a universal chemical assay (71,102). One study found that the H. alvei siderophore was of neither the hydroxamate (aerobactin) nor the catechol (enterobactin) type (67).…”

“…One other study mentions that mice injected intrapertioneally with hafniae did not succumb to infection (91). Approximately 35% to 55% of H. alvei strains are resistant to the bactericidal activity of human or bovine serum (67,102).…”

A rare case of Hafnia alvei pneumonia presenting with chronic obstructive pulmonary disease

“…On the other hand, it is still unknown whether its weak pathogenicity with respect to extraintestinal infections is due to the level of expression of virulence factors. [9] The intra-abdominal area and urinary tract are common sites of H. alvei infections. In addition, it is important to note that this microorganism is associated with biliary tree infections [2] and subsequent abscess formation.…”