Naiel Bisharat

Multilocus Sequence Typing System for Group B Streptococcus

ABSTRACT A multilocus sequence typing (MLST) system was developed for group B streptococcus (GBS). The system was used to characterize a collection (n = 152) of globally and ecologically diverse human strains of GBS that included representatives of capsular serotypes Ia, Ib, II, III, V, VI, and VIII. Fragments (459 to 519 bp) of seven housekeeping genes were amplified by PCR for each strain and sequenced. The combination of alleles at the seven loci provided an allelic profile or sequence type (ST) for each strain. A subset of the strains were characterized by restriction digest patterning, and these results were highly congruent with those obtained with MLST. There were 29 STs, but 66% of isolates were assigned to four major STs. ST-1 and ST-19 were significantly associated with asymptomatic carriage, whereas ST-23 included both carried and invasive strains. All 44 isolates of ST-17 were serotype III clones, and this ST appeared to define a homogeneous clone that was strongly associated with neonatal invasive infections. The finding that isolates with different capsular serotypes had the same ST suggests that recombination occurs at the capsular locus. A web site for GBS MLST was set up and can be accessed at http://sagalactiae.mlst.net. The GBS MLST system offers investigators a valuable typing tool that will promote further investigation of the population biology of this organism.

Clinical, epidemiological, and microbiological features of Vibrio vulnificus biogroup 3 causing outbreaks of wound infection and bacteraemia in Israel

Summary Background Vibrio vulnificus is a gram-negative bacterium that causes septicaemia and wound infection. Cases occur sporadically, and no previous outbreaks due to a common source or a clonal strain have been reported. In the summer and autumn of 1996 and 1997, an outbreak of invasive V vulnificus infection occurred in Israel in people who had recently handled fresh, whole fish purchased from artificial fish-ponds. Methods We reviewed clinical and epidemiological information, and undertook an environmental investigation to assess disease characteristics, modes of transmission, phenotypic characteristics of the bacterium, and fish-marketing policy. The clonal nature of 19 isolates was studied by biotyping, pulsed-field gel electrophoresis, and restriction-fragment length polymorphism (RFLP) analysis of a PCR fragment. Findings During 1996–97, 62 cases of wound infection and bacteraemia occurred. 57 patients developed cellulitis, four had necrotising fasciitis, and one developed osteomyelitis. In all cases, the fish were cultivated in inland fish-ponds. In the summer of 1996, fish-pond managers initiated a new marketing policy, in which fish were sold alive instead of being packed in ice. Phenotypically, the isolates had five atypical biochemical test results. The isolates were non-typeable by pulsed-field gel electrophoresis, and all had the same PCR-RFLP pattern which had not been seen previously. Interpretation The cause of the outbreak was a new strain of V vulnificus , classified as biogroup 3. A new fish-marketing policy that began in 1996 may have exposed susceptible people to the organism.

Hyperinvasive Neonatal Group B Streptococcus Has Arisen from a Bovine Ancestor

ABSTRACT The genetic relatedness and evolutionary relationships between group B streptococcus (GBS) isolates from humans and those from bovines were investigated by phylogenetic analysis of multilocus sequence typing data. The collection of isolates consisted of 111 GBS isolates from cows with mastitis and a diverse global collection of GBS isolates from patients with invasive disease (n = 83) and carriers (n = 69). Cluster analysis showed that the majority of the bovine isolates (93%) grouped into one phylogenetic cluster. The human isolates showed greater diversity and clustered separately from the bovine population. However, the homogeneous human sequence type 17 (ST-17) complex, known to be significantly associated with invasive neonatal disease, was the only human lineage found to be clustered within the bovine population and was distinct from all the other human lineages. Split decomposition analysis revealed that the human isolate ST-17 complex, the major hyperinvasive neonatal clone, has recently arisen from a bovine lineage.

Hybrid Vibrio vulnificus

Hybridization between natural populations of Vibrio vulnificus results in hyperinvasive clone.

Enhanced Invasiveness of Bovine-Derived Neonatal Sequence Type 17 Group B Streptococcus Is Independent of Capsular Serotype

BACKGROUND A defined geographical area (Oxford, United Kingdom) was investigated for the role of group B Streptococcus (GBS) as a human pathogen. METHODS GBS carriage in pregnant women and invasive disease in neonates and adults >60 years of age was studied over a 3-year period. Multilocus sequence typing and capsular serotyping were used to study 369 isolates of GBS from carriage in pregnant women (n=190) and invasive disease in neonates (n=109) and adults >60 years of age (n=70). RESULTS A total of 20.3% of pregnant women carried GBS. Invasive GBS disease occurred at a rate of 0.9 cases per 1000 live births and 11 cases per 100,000 population >60 years of age per annum. Four sequence types (STs) (ST-17, ST-19, ST-23, and ST-1) that were identified with use of multilocus sequence typing accounted for >50% of carried and invasive strains. A single sequence type (ST-17), previously shown to be phylogenetically of bovine origin, was significantly associated with increased invasiveness in neonates (P=.00002), and this was independent of capsular serotype III. In contrast, among adults >60 years of age, no STs exhibited increased invasiveness, compared with STs carried in pregnant women. CONCLUSIONS Enhanced invasiveness associated with ST-17 is specific to neonates and is independent of capsular serotype.

Multilocus Sequence Typing of Serotype III Group B Streptococcus and Correlation with Pathogenic Potential

Serotype III group B streptococcus (GBS) causes more invasive disease in infants than do other serotypes in North America. We used multilocus sequence typing to identify clones within 28 invasive serotype III GBS isolates identified from a population-based study and 55 serotype III GBS colonizing isolates from a cohort of women from the same population. Ten allelic sequence types (STs) were identified and primarily involved 2 profiles: ST-19 (57.1% of invasive isolates and 58.2% of colonizing isolates) and ST-17 (32.1% of invasive isolates and 29.1% of colonizing isolates). On concatenation, the 10 allelic profiles converged into 3 groups. Group 1 consisted of ST-19 complex, ST-36, and ST-1, and was closely related to reference genome 2603V/R (serotype V). Group 2 consisted of ST-17 complex. Group 3 consisted of ST-23 complex and was closely related to the serotype III genome strain NEM 316. Neither of the major sequence types or groups was more commonly associated with invasion (P=.61) or with lower levels of maternal capsular polysaccharide-specific IgG (0.89 microg/mL and 0.39 microg/mL, respectively) for ST-19 and ST-17 (P=.86). The close association of genomic strain 2603V/R (serotype V) with ST-19 suggests that the phenomenon of capsule switching may have occurred.

Gram-Negative Anaerobic Endocarditis: Two Case Reports and Review of the Literature

Abstract.The rarity of anaerobic gram-negative endocarditis limits the ability of physicians to define its prognosis. Two cases of endocarditis due to Bacteroides fragilis are described, and a review of the English literature for all cases of anaerobic gram-negative endocarditis reported since 1940 is presented. The disease predominantly affects males. Clinical features are similar to those of endocarditis due to nonanaerobic organisms, but underlying heart disease is less common and the rate of thromboembolic complications is high. All deaths reported were due to Bacteroides spp.; no deaths due to Fusobacterium spp. have been reported. Treatment with metronidazole has dramatically improved the prognosis of patients with endocarditis due to anaerobic gram-negative bacilli.

Identification of the Emerging Pathogen Vibrio vulnificus Biotype 3 by Commercially Available Phenotypic Methods

ABSTRACT Identification of the emerging pathogen Vibrio vulnificus biotype 3 has become a challenge for clinical laboratories in the last few years. In this study, the abilities of five commercial systems to identify this new species have been evaluated for the first time, using a unique collection of strains. Fifty-one well-documented wild strains of V. vulnificus biotype 3 were processed using API 20 NE, GNI+ Vitek 1 cards, ID-GNB Vitek 2 cards, Neg Combo 20 Microscan panels, and NMIC/ID-5 BD Phoenix panels. The numbers of strains identified as V. vulnificus by ID-GNB, NMIC/ID-5, and GNI+ were 50 (98.0%), 46 (90.2%), and 7 (13.7%), respectively. Neg Combo 20 Microscan panels and API 20 NE were unable to identify any of the strains of this emerging pathogen to the species level and mostly misidentifies them as other species of the Vibrionaceae family. Data on the phenotypic pattern of V. vulnificus biotype 3 when processed in all five systems as presented here could help clinical laboratories in identifying this new pathogen.

Familial pattern of infection with hepatitis B virus among immigrating Ethiopian Jews in Israel

Seventy-eight families (506 members) of recently immigrating Ethiopian Jews to Israel, were tested for the presence of HBV serological markers to evaluate the intrafamilial horizontal transmission of the virus. Eighty-four members (16.6%) were carriers and 20.2% were HBeAg positive, the overall infection rate was 67.8%. In 40 families (51.3%) at least one family member was HBsAG positive, and in 19 families (24.4%) two or more family members were HBsAg positive. Thirty-six carriers (42.8%) were children under the age of 10, by one year of age 30% have contracted the virus, and by the age of 5 and 10 years 43.5% and 57.1% have had serological markers for past HBV infection, respectively. Our data correlate with other studies regarding the importance of horizontal spread of HBV among Sub-Saharan Africans.

Serum antibodies to Vibrio vulnificus biotype 3 lipopolysaccharide and susceptibility to disease caused by the homologous V. vulnificus biotype

In 1996 an outbreak of severe soft tissue infections caused by Vibrio vulnificus unexpectedly erupted in fish consumers in Israel with relatively little morbidity in fish farmers. To test the hypothesis that recurrent exposure of fishermen to the virulent strain may have provided protection against severe or symptomatic disease, we investigated the association between the immune response to V. vulnificus biotype 3 lipopolysaccharide (BT3 LPS) and disease susceptibility in fish farmers and fish consumers. Serum samples were tested for IgA and IgG of anti-BT3 LPS in fishermen and fish consumers who suffered from V. vulnificus BT3 infections and their matched controls. Pre-existing levels of IgG (IgG0) of anti-BT3 LPS were significantly lower in diseased fishermen who developed disease associated with the homologous biotype, compared to controls. In multivariate analysis, levels of IgG0 anti-BT3 LPS remained the only variable significantly associated with disease occurrence in fishermen. Higher levels of pre-existing IgG anti-BT 3 LPS antibodies may be associated with protection against severe or symptomatic disease with the homologous biotype in fishermen but not in subjects from the general public.