A large Escherichia coli O157 outbreak in Sweden associated with locally produced lettuce.

In 2005 a large outbreak of verotoxin-producing Escherichia coli (VTEC) occurred in Sweden. Cases were interviewed and cohort and case-control studies were conducted. Microbiological investigations were performed using polymerase chain reaction (PCR) to detect the Shiga-like toxin (Stx) genes followed by cultivation and pulsed-field gel electrophoresis. A total of 135 cases were recorded, including 11 cases of hemolytic uremic syndrome. The epidemiological investigations implicated lettuce as the most likely source of the outbreak, with an OR of 13.0 (CI 2.94-57.5) in the case-control study. The lettuce was irrigated by water from a small stream, and water samples were positive for Stx 2 by PCR. The identical VTEC O157 Stx 2 positive strain was isolated from the cases and in cattle at a farm upstream from the irrigation point. An active surveillance and reporting system was crucial and cooperation between all involved parties was essential for quickly identifying the cause of this outbreak. Handling of fresh greens from farm to table must be improved to minimize the risk of contamination.

The local immune response to Escherichia coli O and K antigen in experimental pyelonephritis.

Although the systemic and local immune response to the O antigen of Escherichia coli has been well characterized, little information is available on the immune response to K anigen. Experimental hematogenous pyelonephritis was produced with Escherichia coli 06 K13 H1 and the serum and local (intrarenal) antibody response to O and K antigens was determined with the enzyme-linked immunosorbent assay. Both local and serum antibody responses to the K antigen were significantly less than that to the O antigen. The K antigen induced low titer IgM and IgG antibody responses in fewer than one-half of the animals and did not induce a local IgA response in any animal. In contrast, the O antigen induced local antibody responses in each of the immunoglobulin classes in all animals from day 9 of infection. Similarly, the serum IgM and IgG antibody titers to the K antigen were significantly less than those evoked in response to the O component of the Escherichia coli. No serum IgA anti-K antibodies were detected. These observations helf clarify the roles of these two antigens in pyelonephritis. Although the K antigen of Escherichia coli functions as a virulence factor in upper urinary tract infections, this antigen does not elicit a significant immune response, whereas the O antigen does induce a significant antibody response which could be of protective or diagnostic benefit.

Virulence genes in verocytotoxigenic Escherichia coli strains isolated from humans and cattle.

Verocytotoxigenic Escherichia coli (VTEC) causing diarrhoea, haemorrhagic colitis and haemolytic-uremic syndrome usually have additional traits such as the adhesin intimin and a large plasmid that seems to increase virulence. There are, however, isolates of VTEC causing serious symptoms that do not harbour these traits. In the present study we have used PCR with primers detecting adhesin genes other than eaeA, namely fimA, papC, sfaD/sfaE and daaE. We have also used PCR to detect the genes hlyA and iutA that besides the plasmid-borne gene E-hly possibly support the bacterial access to iron. The aim of the study was to identify and compare the presence of virulence genes in VTEC isolates of human and cattle origin. The main finding was that the absence of E-hly might be compensated for by the gene iutA coding for aerobactin or hlyA coding for alpha-haemolysin as 94% of the human VTEC isolates had at least one of these genes. Interestingly, only 45% of VTEC isolated from cattle had any of these genes. We propose that this might be the reason for the relatively low incidence of symptomatic VTEC infections among humans in relation to the high number of VTEC among cattle.

Virulence characteristics of Escherichia coli strains causing acute cystitis in young adults in Iran.

BACKGROUND: Escherichia coli strains that cause cystitis posses virulence properties that facilitate their colonisation and persistence in the bladder. In Iran, despite the high number of the urinary tract infections, very few studies has been done to determine the role of these virulence properties in the pathogenesis of E. coli cyctitis. PATIENTS AND METHODS: Eighty-seven strains of E. coli, isolated from young adults with cystitis in Shiraz, Iran, were examined for the expression of type 1 and P-fimbriae, mannose resistant haemagglutination, haemolysin production, aerobactin-mediated iron uptake, O:K serotypes, biochemical phenotypes (BPTs) and their antibiotic susceptibility patterns. RESULTS: Seventy-six percent of the strains expressed multiple virulence properties. There was a significant correlation between the presence of aerobactin and the expression of type 1 fimbriae. All P-fimbriated strains produced aerobactin with 50% of them also coexpressing haemolysin. Of the 29 different O:K serotypes identified, 42% belonged to serotypes not commonly found among European serotypes associated with UTI. Strains of O groups 4 and 6 expressed more virulence factors than the others. A high resistance against ampicillin, trimethoprim and cotrimoxasol was observed among the isolates with 53% of the isolates showing multiresistance to these three antibiotics. Certain BPTs were also found among O:K serotypes with some containing strains of the same virulence profile. CONCLUSION: We conclude that certain colonal groups of E. coli are commonly associated with cystitis in young adults in Iran with strains possessing a combination of aerobactin and type 1 fimbriae being the dominant ones and belonging to serotypes not commonly found in Europe. We also conclude that the multiple antibiotic resistant E. coli strains causing cyctitis are highly prevalent in this part of the country.

Localization and therapy of urinary tract infections of childhood.

One hundred four patients with 124 episodes of urinary tract infection were studied. Serum C-reactive protein (CRP) was determined on diagnosis of each patient. Children with a CRP equal to or greater than 30 micrograms/ml (CRP-pos) differed significantly from those with values less than 30 micrograms/ml (CRP-neg) in age, clinical presentation, K type of Escherichia coli causing disease, frequency or radiographic abnormalities, and presence of antibody coating of bacteria in the urinary sediment. E. coli K1 strains caused disease significantly more often in CRP-pos than in CRP-neg patients, and children with K1 infections were younger than those with non-K1 infections. The antibody-coated bacteria test was neither sensitive nor specific for localization of infection in pediatric patients. Determination of K1 antibody concentrations in serum and urine of E. coli K1-infected children provided data supporting the measurement of CRP as one means of localizing urinary tract infections. Patients with CRP-neg infections were treated as successfully with four days of antimicrobial therapy as with ten days.

Campylobacter strains from Swedish patients with diarrhoea. Distribution of serotypes over a five year period.

Serotyping, HS antigen and HL antigen, was performed on 105 Campylobacter jejuni/coli isolates from the same number of consequtive patients seeking medical attention for diarrhoea. The results were compared to a similar study performed five years earlier. It was found that there were only minor differences in frequency of the serotypes commonly isolated during the two different periods.

Characterization of Escherichia coli isolated in blood, urine and faeces from bacteraemic patients and possible spread of infection.

Blood, faecal and urine isolates from patients with culture-verified E. coli bacteraemia were investigated with respect to biochemical phenotype, O and K serotype and P. fimbriae. In 10/16 bacteraemic episodes, the blood isolates were identical to the corresponding faecal strains. In four of the remaining infections, antimicrobial therapy was initiated more than two days before faecal samples were taken. Urine cultures revealed growth of E. coli in 12/16 samples. However, only three had clinical signs of symptomatic urinary tract infections. Eight of these E. coli were saved. Further analysis revealed that five of eight strains were identical to the corresponding isolates from blood and stool samples, two were only identical to the faecal strain, while one was different to the corresponding E. coli in the blood and stool samples. The isolated E. coli strains belonged to varying and, among previously healthy persons, normally less common serotypes. No epidemiological relationship was observed between the studied strains. The high incidence of identical strains in the blood, stool and urine indicates a bacterial spread from the faecal flora directly to the urine and possibly also, via the blood, to the urine.

Plasmids and serogroups in Campylobacter jejuni.

For epidemiological purposes identification of Campylobacter strains is usually based on surface antigen characteristics. Two different systems, one for heat-stable (HS) and one for heat-labile (HL) antigen have dominated. In earlier studies we found a great variability in the two antigen systems. The aim of the present investigation was to analyse the frequency of plasmids in Campylobacter strains in the light of their possible use as an epidemiological tool as well as the relation between the presence of plasmids and surface antigens (HS and HL). Two hundred and forty-two strains from the same number of patients with diarrhea were analysed. In 70 (28.9%) plasmid(s) were found, in general one or two. Most of the plasmids were found in the molecular weight interval between 21-40 Md. There was no relation between the presence or size of plasmids and serogroup. We conclude that plasmid determination can be used as a complement to serotyping in epidemiological studies.

Adherence, enterotoxigenicity, invasiveness and serogroups in Campylobacter jejuni and Campylobacter coli strains from adult humans with acute enterocolitis.

Two hundred Campylobacter jejuni and Campylobacter coli strains from the same number of adult Swedish patients with acute enterocolitis were tested regarding adherence to and invasiveness in HEp-2 cells and for enterotoxigenicity by the CHO-cell assay. The serogroup characteristics, heat-stable and heat-labile, for each strain were also investigated. Eighty-four percent of the strains were classified as C. jejuni and 16 percent as C. coli. All of the strains were adherent to HEp-2 cells, 39% were invasive and 31.5% enterotoxigenic. We found significantly more invasive strains in the non-enterotoxigenic group than in the enterotoxigenic one. There would seem to be no correlation between enterotoxigenicity or invasiveness and serogroup. The results of this study suggest the existence of multiple mechanisms for C. jejuni- and C. coli-induced diarrhoea and that the mechanisms may differ from one strain to another.

An experimental model for ascending acute pyelonephritis caused by Escherichia coli or proteus in rats.

Experimental, ascending acute pyelonephritis in rats was produced by injecting 0 x 5 ml of 10(9) bacteria/ml into the urinary bladder via the urethra. No traumatic manipulation of the ureters of kidneys was necessary. A grading system for kidney lesions based on macro- and microscopical examination was used. The capacity of different Escherichia coli and proteus strains to induce acute pyelonephritis was tested, and the E. coli 06K13H1 strain and the Proteus mirabilis 03H1 strain were especially capable of causing urinary tract infection. For the P. mirabilis 03H1 strain, a dominance of right kidney lesions was noted in contrast to the E. coli 06K13H1 strain which did not show any side preference.

Occurrence and susceptibility to antibiotics of Shigella species in stools of hospitalized children with bloody diarrhea in Pakistan.

The aim of the present investigation was to study the frequency of Shigella spp. in patients with bloody diarrhea in Pakistan and the susceptibility of isolated Shigella to three antibiotics: ampicillin, cotrimoxazole and nalidixic acid. In addition, the frequency of Campylobacter and Salmonella was also determined. Stool samples (n = 152) were collected from 152 diarrheic children less than six years of age passing blood and mucus in their stools who were admitted to Paediatric Department of Mayo Hospital in Lahore, Pakistan from June to September 1990. The samples were cultivated on standard media for Shigella, Campylobacter, and Salmonella. Susceptibility of Shigella isolates was tested by disk diffusion method. The frequency of isolation was 19.1% for Shigella spp., 7.9% for Campylobacter, and 4.6% for Salmonella. Shigella flexneri (7.9%) was the most frequently isolated species, followed by S. dysenteriae (6.6%), S. boydii, (3.3%) and S. sonnei (1.3%). All Shigella isolates were susceptible to nalidixic acid (100%), while only a few were susceptible to cotrimoxazole (7.0%) and ampicillin (3.5%). In Pakistan, self-medication and purchases of drugs without a prescription are commonly practiced. Thus, there is a greater possibility of development of resistant strains due to over use of antibiotics.

The serotype distribution of Campylobacter in patients with diarrhoea in Kuwait.

Fifty one strains of Campylobacter jejuni/coli isolated from patients with diarrhoea, at the Amiri Hospital, Hawally, Kuwait were classified on the basis of the heatstable-HS-antigens and the heat-labile-HL-antigens, by using 20 and 23 hyperimmune antisera for the two methods, respectively. The ages of the patient ranged from 3 months to 60 years, and 72.6% of the strains were from children less than 4 years. With the number of antisera used 78.4% of the HS antigens and 96.1% of the HL antigens could be identified. About half of the strains had one of five HS antigens (4, 8, 13, 5 or 25) and 70.5% of the strains had one of five HL antigens (1, 36, 2, 6, or 21). The study shows that the most common HS and HL antigens among Campylobacter strains from Kuwait also are the most frequent antigens of strains from other parts of the world. A limited number of antisera are sufficient to identify the majority of the strains.

Enterotoxigenicity and frequency of Campylobacter jejuni, C. coli and C. laridis in human and animal stool isolates from different countries.

Campylobacter jejuni and C. coli strains were collected during three different years from adult patients with enterocolitis in Sweden (n = 372) from 49 patients in Kuwait, and Campylobacter strains from hens from Mexico, Pakistan and Sweden (n = 107) and Swedish pigs (n = 47). C. jejuni was the predominant species in human and hen isolates, and C. coli in pigs C. coli was significantly more common in human isolates from Sweden, and more common in hen isolates from Pakistan, than in hens from Sweden and Mexico. C. laridis was only isolated from pigs (17%) and was in no case enterotoxigenic. Both in human and hen isolates, C. jejuni strains were more enterotoxigenic than C. coli strains. C. jejuni strains from Swedish hens were less enterotoxigenic than those from Pakistan and Mexico (P less than 0.001), and strains from pigs were less enterotoxigenic than those from hens (P less than 0.001). We conclude that C. jejuni are more often enterotoxigenic and possibly more virulent than c. coli and C. laridis. The relative frequency of C. jejuni and C. coli in humans and animals differs from one country to another.

Characteristics of antibiotic-resistant Escherichia coli in the rectum of healthy school-children.

During a 3-year period, 771 rectal swabs were taken from abacteriuric school-children. Out of 709 E. coli strains, each isolated from one faecal specimen, 102 were found to be resistant to one or more antibacterial agents, and 607 to be fully sensitive. Another 204 resistant strains were found by selection for antibiotic resistance. The antibiotic-sensitive and the resistant strains were found to be two somewhat different populations, distinguished by a different distribution of O antigen types. Also, the K1 antigen was more common among the sensitive than among the resistant strains. Resistant strains that were not O typable were very seldom haemolytic.

Recurrent Escherichia coli bacteraemia--clinical characteristics and bacterial properties.

The aim of the present study was to determine if recurrent bacteraemia due to Escherichia coli might be caused by the same strain in spite of apparently adequate antimicrobial therapy. Eleven patients who, altogether, experienced 24 episodes of E. coli bacteraemia were studied. All had underlying diseases; five biliary-intestinal disease, four were severely immunocompromised and two had urinary tract disorders. During the first bacteraemic episode, nine patients were treated with various combinations of drugs which included gentamicin and two with co-trimoxazole alone. Antibiotic treatment was continued for at least 12 days in each case and all patients were clinically cured. All isolates of E. coli were characterized by biochemical fingerprinting, O and K serotyping, the presence of cell-surface hydrophobicity and production of aerobactin. In two patients, the recurrent infections were due to strains different from those causing the previous episodes. In nine patients who, altogether, had 19 episodes of bacteraemia, the strain of E. coli isolated during the first and all later episodes were identical, according to all tests performed. We suggest that in such circumstances, the infecting strain may remain in the patients' environment and after recolonising the faecal flora may give rise to further infections. It may be, however, that if necessary steps are not taken, the original bacterial focus remains within the same patient so leading to emergence of the infecting strain which may then cause further episodes of bacteraemia.

In vitro studies of Campylobacter jejuni/coli strains from hens and humans regarding adherence, invasiveness, and toxigenicity.

Campylobacter jejuni/coli strains from hens and humans were compared for their ability to adhere to and invade HEp-2-cells and for toxigenicity to CHO-cells. In both hen and human strains, invasiveness was higher among non-toxigenic strains than among toxigenic ones. The frequency of adherence, invasiveness, and toxigenicity was the same in hen and human strains.

Secretory IgA antibodies to enterobacterial virulence antigens: their induction and possible relevance.

1) Milk and salivary s-IgA antibodies are via the homing of IgA producing cells from the Peyer's patches closely connected with antigenic stimuli in the intestine. This explains the presence in human milk of s-IgA antibodies against E. coli O and K antigens, V. cholerae and Shigella O antigens, E. coli and V. cholerae enterotoxins. These secretory antibodies can be induced by intestinal exposure and boosted by parenteral vaccination. 2) Preliminary data suggest that the IgA response in the urinary tract and possibly in the lung may be involved in the homing mechanism as well. 3) The protective role of the milk s-IgA antibodies to enterobacterial virulence antigens is strongly suggested, as is the protection mediated by urinary antibodies against urinary tract infections.

Borrelia infection and vertigo.

73 patients with vertigo were studied regarding serum antibodies to Borrelia spirochete antigen, using an indirect immunofluorescence method. Ten patients (14%) had serological evidence of Borrelia infection. All 10 patients had severe, incapacitating vertigo. Four of the Borrelia patients had positional vertigo and all 10 had positional nystagmus when tested using ENG. Five of them had unilateral caloric weakness. Five patients had abnormal oculomotor tests. Borrelia infection is an etiological factor which should be considered in patients suffering from vertigo especially if positional nystagmus is present.

Perspectives on hepatitis B infections and the efficacy of vaccination (hepatitis B and pneumococci) in dialysis patients.

Hepatitis B is a well known problem in dialysis units. We therefore examined the historical frequency of hepatitis B carriers in our unit, our vaccination program to hepatitis B virus (HBV), the response to hepatitis B vaccine, the IgG subclass response of anti-HBs and the response and IgG subclass response to pneumococcal vaccination (another vaccine) in dialysis patients. From 1970 and onwards 23 HBV carriers were found, but no new cases of hepatitis B occurred during the study period, i.e. from 1980 and onwards. Only one of the carriers was alive by the end of 2001. In four patients liver disease (in one of them liver cirrhosis) may have been a concomitant cause of death. The antibody response to hepatitis B vaccine was significantly lower in patients than in staff. In four patients a fourth injection was cancelled due to transplantation and bad health, while such data were lacking in 8 cases. In anti-HBs positive patients and controls a significant difference in the response of healthy adults was observed in anti-HBs IgG1 (p < 0.001) vs all other IgG subclasses. Dialysis patients had low levels, or negative findings, in all cases, with IgG1 as the highest proportion found (3/11 patients). An antibody response to pneumococcal vaccination was registered in 25 out of 29 dialysis patients (in all 86%). The IgG-subclass vaccination response to pneumococci in 28 dialysis patients was mainly IgG2 and IgG1 but also occurred in IgG3 and IgG4. Prevaccination antibody levels of the controls were higher in IgG1 and IgG2 (p < 0.01) (n = 21) than in dialysis patients (n = 28). Hepatitis B is nowadays a rare, but still dangerous disease in nephrology units. Dialysis patients have a reduced response to hepatitis B vaccine and vaccination schedules should be started early as some patients otherwise may not receive a fourth injection. The adequate antibody response to pneumococcal vaccination mainly due to IgG2 and IgG1 antibodies indicates that the antigen involved is important in vaccination responses in dialysis patients.

Invasive disease caused by Haemophilus influenzae in Sweden 1997-2009; evidence of increasing incidence and clinical burden of non-type b strains.

Introduction of a conjugated vaccine against encapsulated Haemophilus influenzae type b (Hib) has led to a dramatic reduction of invasive Hib disease. However, an increasing incidence of invasive disease by H. influenzae non-type b has recently been reported. Non-type b strains have been suggested to be opportunists in an invasive context, but information on clinical consequences and related medical conditions is scarce. In this retrospective study, all H. influenzae isolates (n = 410) from blood and cerebrospinal fluid in three metropolitan Swedish regions between 1997 and 2009 from a population of approximately 3 million individuals were identified. All available isolates were serotyped by PCR (n = 250). We observed a statistically significant increase in the incidence of invasive H. influenzae disease, ascribed to non-typeable H. influenzae (NTHi) and encapsulated strains type f (Hif) in mainly individuals >60 years of age. The medical reports from a subset of 136 cases of invasive Haemophilus disease revealed that 48% of invasive NTHi cases and 59% of invasive Hif cases, respectively, met the criteria of severe sepsis or septic shock according to the ACCP/SCCM classification of sepsis grading. One-fifth of invasive NTHi cases and more than one-third of invasive Hif cases were admitted to intensive care units. Only 37% of patients with invasive non-type b disease had evidence of immunocompromise, of which conditions related to impaired humoral immunity was the most common. The clinical burden of invasive non-type b H. influenzae disease, measured as days of hospitalization/100 000 individuals at risk and year, increased significantly throughout the study period.