Radiation Sensitivity of Haemophilus influenzae: a Composite Response

The survival of ultraviolet (UV)-irradiated cultures of Haemophilus influenzae Rd is determined by at least two responses: (i) excision-repair ability and (ii) UV-induced cell lysis. An UV-resistant mutant, BC200, has the same capabilities as the wild type, Rd, for excising dimers but does not exhibit lysis. Lytic response is dose-dependent. Relative to the wild type, a lower dose of UV causes lysis of a UV-sensitive mutant, BC100, which is incapable of excising thymine dimers. A lytic protein is present in cultures undergoing lysis. Synthesis of this protein is initiated 45 to 60 min after irradiation. Lysis appears to be due to derepression of a defective prophage which codes for an endolysin-like lytic enzyme.     

Resistance of Haemophilus influenzae to Trimethoprim

Out of 210 isolates of Haemophilus influenzae obtained from the sputum of 63 patients with chronic respiratory infections 109 (52%) were resistant to trimethoprim-sulphamethoxazole by the disc test. The minimal inhibitory concentrations of trimethoprim for 17 out of 18 strains recorded as resistant were 10 μg/ml or higher. Resistant strains were isolated from time to time from 32 (82%) out of 39 patients known to have been treated with trimethoprim-sulphamethoxazole, compared with only 1 (12·5%) out of 8 patients known not to have been treated with this drug combination. Resistant strains were isolated most frequently from patients who had received long-term treatment. Since sulphamethoxazole penetrates from the blood into the bronchial secretions less readily than does trimethoprim it seems likely that the ratio of the two drugs in the bronchial tree is far from ideal. This may be an important factor in the use of these drugs for chest infections.     

Haemophilus influenzae biochemotyping

Biochemotyping was performed in 129 strains of Haemophilus influenzae. 95% of strains could be assigned to one of the five biochemotypes proposed by Kilian. Most of the serotype B strains isolated in meningitis belonged to biochemotype I. The biochemical differentiation of Haemophilus influenzae is regarded as a reliable technique deserving further application.     

Beta- Lactam Antibiotics Stimulate Biofilm Formation in Non-Typeable Haemophilus influenzae by Up-Regulating Carbohydrate Metabolism

Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended.     

流感嗜血杆菌的分型研究

目的分析同济医院分离的流感嗜血杆菌的生物学分型及荚膜基因分型,了解本地区分离的流感嗜血杆菌的主要流行株。方法2012年1月1日至2012年12月31日从华中科技大学同济医学院附属同济医院分离流感嗜血杆菌100株。根据脲酶、吲哚和鸟氨酸脱羧酶试验对流感嗜血杆菌进行传统的生物学分型,分为Ⅰ～Ⅷ八个生物型。回顾患者病史资料,分析生物学分型和流感嗜血杆菌所引起的疾病之间的关系。用流感嗜血杆菌荚膜编码基因（bexA）和a—f型特异性荚膜基因设计引物,采用PCR技术对流感嗜血杆菌进行荚膜基因检测。通过生物学分型和荚膜基因分型结果的比对,探讨两者之间的关联。结果分离的100株流感嗜血杆菌生物学分型结果如下：Ⅲ型6株,Ⅳ型28株,Ⅴ型1株,Ⅵ型54株,Ⅶ型11株。未分离到Ⅰ型、Ⅱ型和Ⅷ型。分析患者的临床诊断,发现主要流行株Ⅵ型流感嗜血杆菌主要引起患者肺炎（包括支气管肺炎和新生儿肺炎）和支气管炎（包括毛细支气管炎和喘息性支气管炎）。荚膜基因分型结果显示,未分离到b型和b-型流感嗜血杆菌。共分离到1株f型,其余99株均为无荚膜抗原的不可分型流感嗜血杆菌。生物学分型和荚膜分型之间无明显的相关性。结论该院分离的流感嗜血杆菌主要为生物型Ⅵ型。回顾患者病史,发现Ⅵ型主要引起肺炎和支气管炎。荚膜基因分型显示,本地区分离的流感嗜血杆菌主要为不可分型流感嗜血杆菌。生物学分型和荚膜基因分型之间无明显相关性。     

Immunity to antigens of nontypeable Haemophilus influenzae strains

Nonencapsulated (nontypeable) Haemophilus influenzae (NTHi) is a Gram-negative coccobacillus colonizing upper respiratory tract of most healthy people and causing such diseases as otitis media, sinusitis, exacerbations of chronic obstructive pulmonary disease, and bronchitis. NTHi may cause systemic infection. As a result, over the past decade the bacterium has been the subject of intense research. However immune response to NTHi has not been well characterized. Data on research of immune response to NTHi are presented.     

Effects of Antibiotics on Induction, Viability, and Reversion Potential of L-Forms of Haemophilus influenzae

The physical interactions between Serratia marcescens and solutions of NaCl, CaCl(2), CaI(2), NaI, and Na(2)HPO(4) plus NaH(2)PO(4) were examined. Dilute (0.017 n) salt solutions did not cause cells to lose water, as evidenced by the unchanged weight of centrifugally packed cells. The cells preferentially adsorbed the cations and repelled the anions of most salts in these solutions. Concentrated (1.71 n) salt solutions markedly reduced the weight and water content of centrifugally packed cells, although these cells took up considerable amounts of salts. More than 90% of the water in the packed-cell pellets was available for the solution of NaCl at 4.2 to 4.4% concentration. The observation that salts apparently penetrated the cells freely and yet caused extensive dehydration was not readily compatible with conventional concepts of solute-induced plasmolysis. Alternative hypotheses to explain the data included the following. First, the cells lost weight and water to concentrated salt solutions through a nonosmotic competitive dehydration, causing a shrinkage of the protoplasmic gel. The shrinkage of the cell wall was limited because of the rigidity of its mucopeptide layer; therefore, a space appeared between the cell wall and the cell membrane. Second, cells may have equilibrated their water activity with that of their environment by two mechanisms: (i) the loss of water by plasmolysis or competitive dehydration, and (ii) alterations in cell permeability that admitted previously excluded solutes to the cell interior. Possibly, the correct explanation of the observations reported here involves elements of all three hypotheses, plasmolysis, competitive dehydration, and permeability alterations.     

Automated Detection of Haemophilus influenzae

Addition of heme (X factor) and pyridine nucleotide (V factor) to the medium permits rapid growth of Haemophilus influenzae, with evolution of easily detectable amounts of (14)CO(2). Radiometric media containing X and V factor should be used when evaluating clinical specimens which might contain Haemophilus species.     

Serotyping of Noncapsular Haemophilus influenzae

A microtechnique is described for agglutination typing of Haemophilus influenzae. It also provides a further means for classification and study of noncapsular type-specific strains.