Streptococcus milleri group bacteraemia in North Yorkshire, England (1989-2000).

BACKGROUND & OBJECTIVES: Though carriage and local infection with organisms of the Streptococcus milleri group (SMG) are regular in clinical practice, bacteraemia is infrequent in man. The objective of the present study was to give an account of our experience with the SMG bacteraemia over a period of 12 yr in North Yorkshire. METHODS: The laboratory and clinical records of all clinically significant cases of SMG bacteraemia in our district general hospital catchment (combined population 260,000) were reviewed for the 12 yr period from 1989 to 2000. Viable isolates were recovered, species identified, and minimum inhibitory concentration (MIC) determined. RESULTS: Twenty nine episodes of infection gave an annual incidence of 0.93 cases per 100,000 population. Infections included abscess, pneumonia, septic arthritis, genital and urinary tract infections, endocarditis and diffuse septicaemia. Patient ages ranged from 18 to 90 yr but most patients were elderly, 82 per cent had evident predisposing conditions and mortality rate was 10 per cent. Species determination of the 22 isolates showed S. anginosus (64%), S. constellatus (27%) and S. intermedius (9%). Nearly all isolates were non-haemolytic and Lancefield grouping showed carriage of the F antigen (in 41%), C (14%) and no detected group (45%). Most of the isolates were susceptible to the antimicrobials tested. INTERPRETATION & CONCLUSION: Bacteraemia with SMG organisms was infrequent, often opportunistic and featured a low overall mortality rate. Intra-abdominal sepsis was the local feature in 16 (55%) of the patients and 9 (31%) of the total patient group showed abscess or empyema. There was a low rate of antibiotic resistance in these organisms from bloodstream infection.

Report of unusual clinical appearance in bacteraemia with nonhaemolytic M-type 58 Streptococcus pyogenes.

BACKGROUND & OBJECTIVES: The occurrence of haemolytic colonies on blood agar often provides the starting point for the laboratory diagnosis of pyogenic streptococci, while non-haemolytic variants could pass unrecognised, leading to a failure of diagnosis. We report the details of two epidemiologically unrelated patients with bacteraemia featuring M-type 58 Streptococcus pyogenes, a seemingly rare cause of human infection in the UK, and briefly review previous reports of infection with non-haemolytic strains of this species. METHODS: Case notes of the two patients were reviewed. Isolates obtained from clinical specimens were recovered and identified and cultured on horse blood agar to observe pattern of haemolysis. RESULTS: In the first case, of a 75 year-old man with leukaemia and a retropharyngeal abscess, the isolate was consistently non-haemolytic, probably due to a failure to produce streptolysin S as has been described before in a small number of reports involving various M-types. In the second case, of an 84 year-old woman with dermatitis and septicaemia, the organism was principally beta-haemolytic but with no haemolysis on aerobic culture where the colonies were well spaced, a phenomenon thought to be associated with abundant production of serum opacity factor (OF). INTERPRETATION & CONCLUSION: These cases are a reminder that misleading cultural appearances can occur with S. pyogenes and that OF positive strains can produce poor haemolysis on aerobic culture, or fail even to do so at all.

Changing incidence of detected streptococcal bacteraemia in North Yorkshire, England.

BACKGROUND & OBJECTIVES: Streptococcal bacteraemia remains a major and challenging clinical problem throughout the world. The epidemiology of these infections appears to be changing. In the present study we analysed the data collected over a period of 20 yr (1978-1999) to throw light on this. METHODS: Laboratory records of all patients yielding clinically significant, non-pneumococcal, nonenterococcal streptococcal bacteraemia were reviewed for the decades 1978-1988 and 1990-1999 in the two districts (combined population 260,000). RESULTS: From a total of 3134 patients with detected bacteraemia 338 (10.8%) yielded streptococci. The organisms comprised: in the beta-haemolytic group (n=169), GAS (32%), GBS (34%), GCS (5%), GGS (28%), GRS (1%); in the non-haemolytic/Streptococcus milleri group (n=160): S. milleri (21%), S. bovis (10%), S. sanguis (30%), S.mitis (10%), S. oralis (8%) and other 'viridans' streptococci (20%); nine isolates were of anaerobic streptococci. There was a steady increase in the number of blood cultures submitted for investigation during the period and streptococcal isolations of all species rose in proportion (approximately x 2.5) in the second decade compared with the first. Complementary data on the occurrence of necrotising fasciitis and toxic shock syndrome in these districts suggested a real increase in the occurrence of serious forms of GAS infection. INTERPRETATION & CONCLUSION: An increase in the level of detected streptococcal bacteraemia was seen in this part of England over 20 yr, involving a wide variety of different streptococcal species. This represented both improved ascertainment of infection and an increase in the burden of disease in the population.

Surface characters and extracellular toxins involved in the pathogenesis of Aeromonas hydrophila.

A small number of serotypically distinct strains of A. hydrophila obtained from diseased freshwater fish were examined for their pathogenic properties comprising of cell surface characteristics and extracellular toxins. Test strains exhibited homogeneity in their cell surface characteristics despite being serologically heterogeneous. Studies on extracellular biological activities revealed qualitative and quantitative differences in production of toxins, probably explaining their antigenic diversity. Three distinct proteases, namely heat stable metallo protease, heat labile serine protease and heat labile metallo protease were identified from the strains.

Immunostimulatory effect of azadirachtin in Oreochromis mossambicus (Peters).

The effect of azadirachtin, a triterpenoid derived from Azadirachta indica on the immune response was studied in the freshwater teleost, O. mossambicus. Bovine serum albumin (BSA) and sheep erythrocytes (SRBC) were used as antigens to evoke immune response. The immune responses in fish were measured by quantifying antibodies produced and counting the peripheral blood leucocytes in control and experimental fish. In general, azadirachtin significantly enhanced the antibody response and leucocyte count in a dose dependent manner. An inverse relationship was observed between the dose of azadirachtin and the degree of immunostimulation. Timing of azadirachtin administration in relation to immunization revealed that the maximum enhancement of antibody response was observed when the stimulant was given two days prior to immunization. The observed immunostimulatory property of azadirachtin has an implication in the maintenance of finfish health in freshwater intensive aquaculture practices.

Partial characterization of serum immunoglobulins of Oreochromis mossambicus.

Serum immunoglobulins of O. mossambicus were purified using chromatography methods--CM affinity gel blue chromatography followed by two step purification involving a combination of ion-exchange and gel filtration chromatography. Studies revealed that O. mossambicus produces only one class of high molecular weight macroglobulin as determined by molecular sieving by Sepharose CL 6-B. Immunoelectrophoresis of purified O. mossambicus serum against rabbit anti O. mossambicus serum gave only a single precipitin line. Further analysis of the immunoglobulin by SDS-PAGE showed that the IgM macroglobulin weighs about 900,000 Da, composed of mu-like heavy chain weighing about 90 kDa each and light chains weighing about 30 kDa each.

Modulation of humoral immune response by ascorbic acid in Oreochromis mossambicus (Peters).

Fish were treated with sublethal doses of ascorbic acid before being immunised with different physical forms of bovine serum albumin (BSA). Ascorbic acid elevates the antibody response to all the physical forms of BSA tested. Generally, there was an inverse relationship between the dose of ascorbic acid and antibody response. In fish administered with multiple doses of ascorbic acid, no significant enhancement of antibody response was observed.

Modulation of humoral immune response by tannery effluent in Oreochromis mossambicus (Peters).

Fish were treated with various sublethal concentrations of tannery effluent. A concentration-dependent suppression of both primary and secondary antibody responses to bovine serum albumin (BSA) was observed after primary or secondary immunization. The fish were able to compensate the effluent-induced suppression of antibody response when the antigen (BSA) was administered along with an oil adjuvant.

Diel variations in antibody response to bovine serum albumin in Oreochromis mossambicus (Peters).

Influence of time of antigen administration on antibody response to bovine serum albumin in the fish, O. mossambicus and variations in serum antibody titre during a 24 hr cycle are reported. Significant variations were observed in magnitude of antibody response in groups of fishes immunized at different times of the day. Magnitude of the response was maximal in fish immunized at 16 hr and minimal in those immunized at 4 hr. Serum antibody titres in a 24 hr study also varied markedly with general elevation during day time, reaching the maximum at 12 hr and depression during night with the lowest titre at 4 hr. These results can be positively correlated to diel variation in number of leucocytes or proportion of lymphocytes which in turn is possibly correlated (negatively) to the periodicity in plasma corticosteroid level.