Hemagglutination of Human Type O Erythrocytes, Hemolysin Production, and Serogrouping of Escherichia coli Isolates from Patients with Acute Pyelonephritis, Cystitis, and Asymptomatic Bacteriuria

Abstract

The purpose of this investigation was to study potential virulence factors associated with Escherichia coli urinary pathogens isolated from patients with urinary tract infection. These factors were compared with characteristics of normal-flora E. coli isolated from stool specimens of healthy individuals without a history of urinary tract infection. The potential virulence factor focused on in this study was hemagglutination (HA) of human type 0 erythrocytes by E. coli urinary pathogens. A total of 265 strains of E. coli isolated from patients with urinary tract infections were tested for their ability to hemagglutinate human type 0 erythrocytes; of these, 148 (56%) were HA positive. Only 6 of 36 fecal E. coli strains (17%) isolated from healthy controls were HA positive. This significant association of the presence of hemagglutinin on E. coli that causes urinary tract infections indicates the likelihood that HA is a marker of virulence. Only 12% (5 of 43) of Proteus mirabilis and 3% (3 of 104) of Klebsiella pneumoniae urinary isolates were HA positive. There was a trend for HA-positive E. coli to be isolated from patients with kidney infections and positive tests for antibody-coated bacteria rather than bladder infections and negative tests for antibody-coated bacteria, although the difference was not statistically significant. There was a significant correlation (P < 0.025) between hemolysin production and HA; 67% (69 of 103) of the isolates that produced hemolysin also hemagglutinated human type 0 erythrocytes. There was no significant correlation between HA and motility, although there was a trend for flagellated organisms to be non-hemagglutinators. There was a marked correlation between the presence of hemagglutinin and the serogroup of the E. coli isolate; serogroups 04, 07, and 050 were almost always HA positive (57 of 63; 90%). In contrast, serogroups 08 and 025 were rarely HA positive (2 of 30; 7%).

Hemolysin Production as a Virulence Marker in Symptomatic and Asymptomatic Urinary Tract Infections Caused by Escherichia coli

“…In particular, strains of MRHA types VI and VII and MSHA type III were over 60% Hly+, in contrast to types V (16%) and IVB (HA-, 8%). This is in general agreement with previous studies (8,13,17) of unselected UTI isolates, i.e., not restricted to the eight most important 0-types.…”

“…Strains of 0-types 01, 04, 06, 018, and 075, which are the five serotypes most prevalent in UTI (see, e.g., reference 20), were most commonly of MRHA type VI; MRHA type V was found particularly often among 02 strains, and type VII was rare. These data support and extend those of Greene and Thomas (13), who, unlike Vosti (30), found agglutination of human erythrocytes not to be randomly distributed throughout the 0-types. Hemolytic isolates were more often MRHA+ and less often HAthan those which were nonhemolytic.…”

“…Our data and those of others (8,13) indicate that a relatively limited number of "aggresive" strains are well adapted to extraintestinal, e.g., urinary tract, invasiveness, and, as previously suggested for other E. coli infections (19,21), these strains may represent descendants of a small number of clones.…”

“…In this hospital, strains of serotypes 01, 02, 04, 06, 07, 09, 018, and 075 cause approximately 7, 2, 5, 10, 3, 2, 5, and 9% of UTI, respectively. Several characteristics of urinary strains are strongly associated with particular 0-types, including hemolysin production (Hly) (predominantly serotypes 06, 075, 018, and 04) (8,13,15) and colicin V production (Cva) (serotypes 09 and 01). It also seems (Fig.…”

“…Many cell surface components have been shown to be associated with E. coli strains causing extraintestinal infections, including fimbriae (hemagglutination [HA] antigens) (3,8,13,16,30) and specific 0 and K antigens (3,8,14,31), as have the extracellular proteins colicin V (6) and hemolysin (3,5,8,13,17). Although the effects of these factors on virulence characteristics such as adhesion and serum resistance are in certain cases partially elucidated, it remains unclear to what extent they interact to determine virulence in the strains of E. coli isolated from UTI and to what extent they are associated with the establishment of clinical symptoms in the host.…”