Streptococcus anginosus ("Streptococcus milleri"): the unrecognized pathogen

Identification of chromosomal antibiotic resistance genes in Streptococcus anginosus ("S. milleri")

Determinants encoding resistance to antibiotics, except penicillin, of 5 of 21 Streptococcus anginosus clinical isolates that we examined transferred by conjugation into Enterococcus faecalis and into 1 to 5 streptococcal recipients at frequencies of 10(-6) to 10(-8) transconjugants per donor. No R plasmids were detected in any wild-type strain. DNA homology was detected between chromosomal fragments and the following genes: aadE in 7 strains that were highly resistant to streptomycin, aph-3 in 8 strains that were highly resistant to kanamycin, ermB in 11 of 15 strains that were resistant to erythromycin, and tetM in 14 and tetO in 3 of the 18 strains that were resistant to tetracycline-minocycline. A Tn916-like structure was found in 10 of the 14 strains that carried the tetM gene.

Phenotypic differentiation of Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus strains within the "Streptococcus milleri group"

A biochemical scheme was developed by which strains of Streptococcus constellatus, Streptococcus intermedius, and Streptococcus anginosus can reliably be distinguished from within the "Streptococcus milleri group." Strains identified as S. intermedius were differentiated by the ability to produce detectable levels of alpha-glucosidase, beta-galactosidase, beta-D-fucosidase, beta-N-acetylgalactosaminidase, beta-N-acetylglucosaminidase, and sialidase with 4-methylumbelliferyl-linked fluorogenic substrates in microdilution trays after 3 h of incubation at 37 degrees C, together with the production of hyaluronidase. Strains of S. constellatus and S. anginosus were differentiated by the production of alpha-glucosidase and hyaluronidase by the former and the production of beta-glucosidase by the latter. The majority of strains of the S. milleri group obtained from dental plaque were identified as S. intermedius, as were most strains isolated from abscesses of the brain and liver. Strains of S. constellatus and S. anginosus were from a wider variety of infections, both oral and nonoral, than were strains of S. intermedius, with the majority of strains from urogenital infections being identified as S. anginosus.

Cellular coaggregation of oral Streptococcus milleri with actinomyces

Oral isolates of Streptococcus milleri were examined for their ability to coaggregate with actinomyces. Of the 68 S. milleri strains tested, including 3 reference strains, 40 strains coaggregated with Actinomyces naeslundii WVU45 (actinomyces coaggregation group B) and 36 strains coaggregated with Actinomyces viscosus T14V (actinomyces coaggregation group A). All S. milleri strains of serotypes b (4 strains), e (2 strains), and f (24 strains) coaggregated with both of the actinomyces. The coaggregation reactions between the S. milleri cells and A. naeslundii WVU45 cells were optimal at about pH 7.0 and were Ca2+ or Mg2+ dependent, but they were not inhibited by the presence of simple sugars or amino sugars, including lactose (up to 0.5 M). Treatment of the S. milleri cells with heat (100 degrees C, 3 min) or proteases (trypsin, 1.0 mg/ml; pronase, 0.25 mg/ml; 37 degrees C; 3 h) and of the actinomyces cells with periodate (0.01 M, 4 degrees C, 16 h) destroyed their coaggregating abilities. The coaggregations between cells of the S. milleri strains, we well as cells of the Streptococcus sanguis H1 (reference strain for streptococcus coaggregation group 2) and the actinomyces strains (WVU45 and T14V), were inhibited by AFH1 (a carbohydrate receptor on T14V cells for a lectin on H1 cells). These interactions were also inhibited by anti-AFH1 immunoglobulin G (IgG) and by anti-b, anti-e, and anti-f S. milleri IgG or anti-f IgG Fab fragments. These results suggest that S. milleri, at least strains of serotypes b, e, and f, belongs to streptococcus coaggregation group 2.

Clinical implications of positive blood cultures

Positive blood cultures can be classified according to their veracity (true-positive or false-positive culture), clinical severity (inconsequential or life threatening), place of origin (community acquired or nosocomial), source (primary or secondary), duration (transient, intermittent, or continuous), pattern of occurrence (single episode, persistent, or recurrent), or intensity (high or low grade). In general, however, positive blood cultures identify a patient population at high risk of death. In my studies, patients with positive blood cultures were 12 times more likely to die during hospitalization than patients without positive blood cultures. Many bacteremias and fungemias occur in complicated clinical settings, and it appears that only about one-half of the deaths among affected patients are due directly to infection. Hence, it is appropriate to speak of "crude mortality" and "attributable mortality." Among hospitalized patients, recent trends include rising incidences of Staphylococcus aureus and coagulase-negative staphylococcal and enterococcal bacteremias and a dramatic increase in the incidence of fungemias. The diagnostic and therapeutic implications of blood cultures positive for specific microorganisms continue to evolve and are the subject of a large and growing medical literature.

Classification and identification of the viridans streptococci

This review traces the history of the human, nonhemolytic, or viridans, streptococci and describes improvements in their taxonomy wrought by study of their biochemical profiles and analysis of their nucleic acids. The goal was to define species on the basis of genetic relationships and to describe these species by their phenotypic characteristics so that they can be easily identified. This method has resulted in the division of some species. Streptococcus mutans has been divided into four species, two of which are common in humans. Three more mutans group species are indigenous to animals. Conversely, S. constellatus, S. intermedius, and "S. milleri" have been combined under S. anginosus. S. mitis (or "S. mitior") can be well-defined and includes S. sanguis II. There is genetic heterogeneity within S. sanguis, but the species is usually easy to identify. There is also some heterogeneity in S. bovis, but most human isolates are genetically related. Discussions of the taxonomy of these species are accompanied by descriptions of the characteristics by which these streptococci can be identified. Among these species are potential pathogens which should be suspected in cases of endocarditis and purulent infections of liver, brain, and other tissues.

Group C streptococci in human infection: a study of 308 isolates with clinical correlations

A collection of 308 clinical isolates of beta-haemolytic Lancefield group C streptococci was assembled from laboratories in England, Nigeria and New Zealand. Of these, 276 isolates were Streptococcus equisimilis, 23 S. milleri and nine S. zooepidemicus. Isolates of S. equisimilis in the African collection, though few, gave higher rates of lactose and raffinose fermentation, aesculin hydrolysis and positive alpha-galactosidase reactions than those from elsewhere. Erythromycin resistance was found in 1.9% of the English isolates of S. equisimilis. Strains from superficial infections accounted for 88% of the collection and were most commonly isolated from the upper respiratory tract, skin or wounds. Amongst the 36 patients yielding isolates from deep sites S. equisimilis was found in septicaemia, cellulitis, abscess, peritonitis, septic arthritis, pneumonia, mycotic aneurysm and acute epiglottitis, S. milleri was found in abdominal abscesses, peritonitis, pleural empyema and osteomyelitis and S. zooepidemicus was found in septicaemia, pneumonia, meningitis and septic arthritis. Within the collection an unselected general catchment of 214 isolates of group C streptococci from the laboratories in Yorkshire showed the following species: from 199 superficial infections 94% S. equisimilis, 5% S. milleri and 1% S. zooepidemicus and 15 patients with deeper, more aggressive infections 67, 27 and 6.7% of these species respectively.

Hyaluronidase production in Streptococcus milleri in relation to infection

One hundred and seven (41%) of 262 isolates of Streptococcus milleri, from human sources, produced hyaluronidase. Hyaluronidase production was commoner in beta haemolytic isolates 32 of 39 (82%), many of which were of Lancefield group F. But hyaluronidase was also found in alpha and non-haemolytic isolates, and in groups A, C, G, and non-groupable isolates. There was a strong association between hyaluronidase production and isolation from known internal abscesses (48/58, 83%) compared with isolates from the normal flora of uninfected sites (24/97, 25%). Isolates from 15 patients with endocarditis were uniformly negative, although 13 of 25 (52%) isolates from dental plaque produced the enzyme. Production of hyaluronidase may therefore be an important determinant in the pathogenicity of infection by S milleri and could be helpful in predicting the likelihood of deep purulent lesions in isolates from blood culture.

Invasive streptococcal infections in the era before the acquired immune deficiency syndrome: a 10 years' compilation of patients with streptococcal bacteraemia in North Yorkshire

Significant streptococcal (non-pneumococcal, non-enterococcal) bacteraemia was detected in 100 patients in two Health Districts of North Yorkshire in the decade 1978-1988. Patients with these infections accounted for 11% of the total 902 patients in the districts in whom bacteraemia was diagnosed during the period. Infection was most often seen with beta-haemolytic streptococci (52 patients) comprising Lancefield group A (Streptococcus pyogenes) (20 patients), group B (13), group C (5), group G (9), haemolytic Streptococcus milleri and non-groupable streptococci (5). The wide variety of serious infections included cellulitis, abscess, septicaemia, pneumonia, septic arthritis, necrotising fasciitis, acute endocarditis and mycotic aneurysm. Of these 52 patients, 21 (40%) died. alpha-Haemolytic streptococcal bacteraemia was diagnosed in 38 patients of whom 24 (63%) suffered from endocarditis and three (8%) died. Three of ten patients with non-haemolytic or anaerobic streptococcal bacteraemia died also. Six of the 100 patients with streptococcal bacteraemia had concomitant acute virus infections. Of the total 56 patients with infective endocarditis diagnosed in the districts during the period, streptococci were responsible in 30 (54%) of them. The predisposing factors, clinical features and outcome of the infections are described and discussed.

Septic arthritis of the knee due to Streptococcus anginosus

A case of arthritis caused by Streptococcus anginosus was observed in which the only predisposing factor was osteoarthritis of the knee and an acute meniscal tear. We report here the fifth case of septic arthritis due to Streptococcus anginosus.

Chondroitinase C activity of Streptococcus intermedius

Chondroitin 6-sulfate depolymerizing activity was examined in the culture supernatant of Streptococcus intermedius ATCC 27335. 2-Acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose was split from the substrate. The enzyme(s) was not active upon chondroitin 4-sulfate or dermatan sulfate, which indicated that the enzyme responsible for the depolymerization is chondroitinase C.