Obstructive sleep apnea and pregnancy: the effect on perinatal outcomes.

Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airway obstruction, resulting in hypoxemia, hypercapnia and sleep fragmentation. Pathophysiological sequelae include sympathetic activation, increased oxidative stress and a generalized inflammatory response, culminating in endothelial dysfunction. These are the proposed mechanisms that mediate the increased risk of hypertension and cardiovascular disease among patients with OSA outside of pregnancy. It is intriguing to consider the consequences of these events on pregnancy outcomes. There is a growing literature on the impact of maternal OSA on hypertensive disorders of pregnancy, gestational diabetes and impaired fetal growth. The data, while promising, require confirmation with larger numbers to verify the findings. OSA may be an important mediator of the poor perinatal outcomes associated with maternal obesity; moreover, one which may be amenable to treatment. This review discusses OSA and summarizes the current literature linking OSA with adverse perinatal outcomes.

Bacteraemia caused by Anaerotruncus colihominis and emended description of the species.

BACKGROUND: Anaerotruncus colihomonis is a newly described bacterial genus and species isolated from the stool specimens of children. Its clinical significance, however, is unknown. AIMS: To describe a case of A colihominis bacteraemia identified by 16S ribosomal RNA (rRNA) gene sequencing and provide an emended description of the species. METHODS: An unidentified anaerobic bacillus (strain HKU19) that stains Gram negative was subjected to characterisation by 16S rRNA gene sequencing, G+C content determination and electron microscopy. RESULTS: Strain HKU19 was isolated from the blood culture of a 78-year-old woman with nosocomial bacteraemia. It was found to be an anaerobic, non-motile, pleomorphic, thin bacillus that stains Gram negative. It produces Indole and utilises glucose and mannose. Identifying the strain to the species level was not possible by conventional phenotypic tests and commercial identification systems. The G+C content of strain HKU19 was found to be 53.43 mol%. A similarity of 99.3% nucleotide identities was found between the 16S rRNA gene sequence of strain HKU19 and that of A colihominis WAL 14 565(T), which was isolated from a human faecal specimen. In contrast with the original description of A colihominis, HKU19 was found to produce occasional oval, terminal spores, although the other phenotypic characteristics matched. Spores were also occasionally observed when the two previously reported strains were re-examined. CONCLUSIONS: Although the source of the bacteraemia in the patient cannot be determined, this report suggests that A colihominis is of clinical significance. Spore formation is proposed as an emended description of A colihominis.

Usefulness of the MicroSeq 500 16S rDNA bacterial identification system for identification of anaerobic Gram positive bacilli isolated from blood cultures.

Using full 16S ribosomal RNA (rRNA) gene sequencing as the gold standard, 20 non-duplicating anaerobic Gram positive bacilli isolated from blood cultures were analysed by the MicroSeq 500 16S rDNA bacterial identification system. The MicroSeq system successfully identified 13 of the 20 isolates. Four and three isolates were misidentified at the genus and species level, respectively. Although the MicroSeq 500 16S rDNA bacterial identification system is better than three commercially available identification systems also evaluated, its database needs to be expanded for accurate identification of anaerobic Gram positive bacilli.

Clostridium bacteraemia characterised by 16S ribosomal RNA gene sequencing.

BACKGROUND: Owing to problems in accurate species identification of the diverse genus clostridium, the epidemiology and pathogenicity of many species are not fully understood. Moreover, previous studies on clostridium bacteraemia have been limited and relied only on phenotypic species identification. AIMS: To characterise the epidemiology, disease spectrum, and outcome of clostridium bacteraemia using 16S ribosomal RNA (rRNA) gene sequencing. METHOD: During a four year period (1998-2001), all cases of clostridium bacteraemia were prospectively studied and all "non-perfringens" clostridium isolates identified to the species level by 16S rRNA gene sequencing. RESULTS: Fifty one blood culture isolates were identified as Clostridium perfringens and 17 belonged to 11 other clostridium species. The first case of C disporicum infection and two cases of clostridium bacteraemia in children with intussusception were also described. Of the 68 clostridium isolates from 68 different patients, 38 were associated with clinically relevant bacteraemia. The gastrointestinal and hepatobiliary tracts were common sites of both underlying disease and portal of entry in these patients. Clostridium perfringens accounted for 79% of all clinically relevant bacteraemia, with the remainder caused by a diversity of species. The attributable mortality rate of clinically relevant clostridium bacteraemia was 29%. Younger age and underlying gastrointestinal/hepatobiliary tract disease were associated with mortality (p < 0.05). CONCLUSIONS: Patients with clinically relevant clostridium bacteraemia should be investigated for the presence of underlying disease processes in the gastrointestinal or hepatobiliary tracts. 16S rRNA gene analysis will continue to be useful in further understanding the pathogenicity of various clostridium species.

Gemella bacteraemia characterised by 16S ribosomal RNA gene sequencing.

AIMS: To define epidemiology, clinical disease, and outcome of gemella bacteraemia by 16S rRNA gene sequencing. To examine the usefulness of the Vitek, API, and ATB systems in identifying two gemella species. METHODS: All alpha haemolytic streptococci other than Streptococcus pneumoniae isolated from blood cultures during a six year period were identified by conventional biochemical methods, the Vitek system, and the API system. 16S rRNA gene sequencing was performed on all isolates identified by both kits as gemella with >or= 95% confidence or by either kit as any bacterial species with < 95% confidence. The ATB expression system was used to identify the two isolates that were defined as gemella species by 16S rRNA gene sequencing. RESULTS: Of the 302 alpha haemolytic streptococci other than S pneumoniae isolated, one was identified as Gemella morbillorum, and another as Gemella haemolysans by 16S rRNA gene sequencing. The patient with monomicrobial G morbillorum bacteraemia was a 66 year old man with community acquired infective endocarditis with septic thromboemboli. The patient with G haemolysans bacteraemia was a 41 year old woman with hospital acquired polymicrobial bacteraemia during the neutropenic period of an autologous bone marrow transplant for non-Hodgkin's lymphoma, the first case of its kind in the English literature. The API and ATB expression systems only identified the second strain as G haemolysans at 94% and 99% confidence, respectively, whereas the Vitek system identified none of the two strains correctly at > 70% confidence. CONCLUSIONS: Gemella bacteraemia is uncommon. 16S rRNA gene sequencing is the method of choice for identification of gemella and gemella-like isolates.

Group G beta-hemolytic streptococcal bacteremia characterized by 16S ribosomal RNA gene sequencing.

Little is known about the relative importance of the four species of Lancefield group G beta-hemolytic streptococci in causing bacteremia and the factors that determine the outcome for patients with group G beta-hemolytic streptococcal bacteremia. From 1997 to 2000, 75 group G beta-hemolytic streptococcal strains were isolated from the blood cultures of 66 patients. Sequencing of the 16S rRNA genes of the group G beta-hemolytic streptococci showed that all 75 isolates were Streptococcus dysgalactiae subspecies equisimilis. The API system (20 STREP) and Vitek system (GPI) successfully identified 65 (98.5%) and 62 (93.9%) isolates, respectively, as S. dysgalactiae subspecies equisimilis with >95% confidence, whereas the ATB Expression system (ID32 STREP) only successfully identified 49 isolates (74.2%) as S. dysgalactiae subspecies equisimilis with >95% confidence. The median age of the patients was 76 years (range, 33 to 99 years). Fifty-six patients (85%) were over 60 years old. All patients had underlying diseases. No source of the bacteremia was identified (primary bacteremia) in 34 patients (52%), whereas 17 (26%) had cellulitis and 8 (12%) had bed sore or wound infections. Fifty-eight patients (88%) had community-acquired group G streptococcal bacteremia. Sixty-two patients (94%) had group G Streptococcus recovered in one blood culture, whereas 4 patients (6%) had it recovered in multiple blood cultures. Fifty-nine patients (89%) had group G Streptococcus as the only bacterium recovered in their blood cultures, whereas in 7 patients other bacteria were recovered concomitantly with the group G Streptococcus in the blood cultures (Staphylococcus aureus in 3, Clostridium perfringens in 2, Citrobacter freundii in 1, and Bacteroides fragilis in 1). Overall, 10 patients (15%) died. Male sex, diagnosis other than cellulitis, hospital-acquired bacteremia, and multiple positive blood cultures were associated with mortality [P < 0.005 (relative risk [RR] = 7.6), P < 0.05 (RR = 3.7), P < 0.005 (RR = 5.6), and P < 0.05 (RR = 5.6), respectively]. Unlike group C beta-hemolytic streptococcal bacteremia, group G beta-hemolytic streptococcal bacteremia is not a zoonotic infection in Hong Kong.

Isolation and characterization of a Salmonella enterica serotype Typhi variant and its clinical and public health implications.

We report the isolation and characterization of a member of the family Enterobacteriaceae isolated from the gallbladder pus of a food handler. Conventional biochemical tests suggested Salmonella enterica serotype Typhi, but the isolate agglutinated with poly(O), 2O, 9O, and Vi Salmonella antisera but not with poly(H) or any individual H Salmonella antisera. 16S rRNA gene sequencing showed that there were two base differences between the isolate and Salmonella enterica serotype Montevideo, four base differences between the isolate and serotype Typhi, five base differences between the isolate and Salmonella enterica serotype Typhimurium, and six base differences between the isolate and Salmonella enterica serotype Dublin, indicating that the isolate was a strain of S. enterica. Electron microscopy confirmed that the isolate was aflagellated. The flagellin gene sequence of the isolate was 100% identical to that of the H1-d flagellin gene of serotype Typhi. Sequencing of the rfbE gene, which encoded the CDP-tyvelose epimerase of the isolate, showed that there was a point mutation at position +694 (G-->T), leading to an amino acid substitution (Gly-->Cys). This may have resulted in a protein of reduced catalytic activity and hence the presence of both 2O and 9O antigens. We therefore concluded that the isolate was a variant of serotype Typhi. Besides antibiotic therapy and cholecystectomy, removal of all stones in the biliary tree was performed for eradication of the carrier state.