Adsorbate dissociation due to heteromolecular electronic energy transfer from fluorobenzene thin films

Study of the near-UV photodissociation dynamics for monolayer (ML) quantities of CH3I on thin films of a series of fluorobenzenes and benzene (1-25 ML) grown on a Cu(100) substrate finds that in addition to gas-phase-like neutral photodissociation, CH3I dissociation can be enhanced via electronic energy transfer to the CH3I following photoabsorption in several of the thin films studied. Distinct CH3 photofragment kinetic energy distributions are found for CH3I photodissociation on C6H5F, 1,4-C6H4F2 and C6H6 thin films, and distinguished from neutral photodissociation pathways using polarized incident light. The effective photodissociation cross section for CH3I on these thin films is increased as compared to that for the higher F-count fluorobenzene thin films due to the additional photodissociation pathway available. Quenching by the metal substrate of the photoexcitation via this new pathway suggests a significantly longer timescale for excitation than that of neutral CH3I photodissociation. The observations support a mechanism in which neutral photoexcitation in the thin film (i.e. an exciton) is transported to the interface with CH3I, and transfers the electronic excitation to the CH3I which then dissociates. The unimodal CH3 photofragment distribution and observed kinetic energies on the fluorobenzene thin films suggest that the dissociation occurs via the 3Q1 excited state of CH3I.

Increased risk of eosinophilic esophagitis with poor environmental quality as measured by the Environmental Quality Index

Geographic differences in eosinophilic esophagitis (EoE) prevalence suggest the possibility that environmental exposures contribute to EoE pathogenesis. We aimed to examine the association between environmental quality and risk of EoE, using the Environmental Quality Index (EQI), which provides quantification of environmental quality in five domains: air, land, water, built, and sociodemographic for all counties in the United States. To do this, we performed a case-control study in a large pathology database. EoE cases were defined by ≥15 eosinophils per high-power field with other pathologic diagnoses excluded; controls did not have EoE. The pathology data were geocoded and linked with the EQI by county of residence. Logistic regression was used to estimate odds ratio (OR and 95% confidence interval [CI]) of EoE with overall EQI and for each domain, after adjusting for sex, age, and proportion minority race or ethnicity at the county level (higher EQI score indicates worse environmental quality). Of 29,802 EoE cases and 593,329 controls analyzed, odds of EoE were highest in the worst quintile of EQI (OR 1.25; 95% CI: 1.04-1.50), which was largely explained by poor scores in the water domain (OR: 1.33; 1.17-1.50). Conversely, odds of EoE were reduced with higher scores in the air domain (OR: 0.87, 0.74-1.03) and land domain (OR 0.87; 0.76-0.99). Poor EQI, mostly reflected by poor water quality, was associated with increased odds of EoE, while poor air and land quality were inversely associated with EoE. Additional work to identify specific water pollutants that may have an etiologic role in EoE may be warranted.

Laminar airflow decreases microbial air contamination compared with turbulent ventilated operating theatres during live total joint arthroplasty: a nationwide survey

BACKGROUND

Preventing surgical site infections and prosthetic joint infections is crucial for patient safety after total joint arthroplasty. Microbial air contamination has been suggested as a risk factor. Therefore, the ventilation system that will reduce air contamination most effectively in operating theatres (OTs) has been discussed.

AIM

To determine whether laminar airflow (LAF) ventilation is superior to turbulent airflow (TAF) ventilation by looking at the colony forming units (cfu) count during live total hip and knee arthroplasties. Furthermore, to explore whether the number of OT personnel, door and cabinet lock openings and technical parameters of the ventilation systems have an impact on the number of cfu.

METHODS

Active air sampling and passive sedimented bacterial load were performed in 17 OTs, equipped with either LAF or TAF ventilation, during 51 live surgeries while observations were noted.

FINDINGS

LAF OTs reduced cfu counts compared with TAF OTs during live surgery (P<0.001). All LAF OTs provided ultraclean air whereas TAF had nine procedures exceeding the threshold of 10 cfu/m³. Door and cabinet lock openings and number of personnel did not influence the cfu count, while it decreased with increasing volume and total air change per hour (P<0.05).

CONCLUSION

All LAF OTs had cfu counts within recommendations and provided lower cfu counts compared with TAF OTs. The number of OT personnel and total openings did not have an influence on cfu counts. Increased volume of the OT and total air change per hour showed a decrease in active cfu counts.

Contrasting mechanisms for photodissociation of methyl halides adsorbed on thin films of C6H6 and C6F6

The mechanisms for photodissociation of methyl halides (CH3X, X = Cl, Br, I) have been studied for these molecules when adsorbed on thin films of C6H6 or C6F6 on copper single crystals, using time-of-flight spectroscopy with 248 nm and 193 nm light. For CH3Cl and CH3Br monolayers adsorbed on C6H6, two photodissociation pathways can be identified - neutral photodissociation similar to the gas-phase, and a dissociative electron attachment (DEA) pathway due to photoelectrons from the metal. The same methyl halides adsorbed on a C6F6 thin film display only neutral photodissociation, with the DEA pathway entirely absent due to intermolecular quenching via a LUMO-derived electronic band in the C6F6 thin film. For CH3I adsorbed on a C6F6 thin film, illumination with 248 nm light results in CH3 photofragments departing due to neutral photodissociation via the A-band absorption. When CH3I monolayers on C6H6 thin films are illuminated at the same wavelength, additional new photodissociation pathways are observed that are due to absorption in the molecular film with energy transfer leading to dissociation of the CH3I molecules adsorbed on top. The proposed mechanism for this photodissociation is via a charge-transfer complex for the C6H6 layer and adsorbed CH3I.

Excitation and quenching mechanisms in the near-UV photodissociation of CH3Br and CH3Cl adsorbed on D2O or CH3OH on Cu(110)

Photochemical processes for CH3X (X = Cl, Br, I) adsorbed on top of thin films of D2O or CH3OH on a Cu(110) substrate is studied by time-of-flight mass spectrometry for a range of UV wavelengths (351-193 nm). Photodissociation via dissociative electron attachment by photoelectrons and by neutral photodissociation is identified and quantified based on the observed dynamics of the desorbing CH3 fragments. Photoelectron-driven dissociation of CH3X is found to be a maximum for monolayer quantities of the D2O or CH3OH on Cu(110), but with differing kinetic energy release on the two substrates. The dynamics of CH3Br and CH3Cl photodissociation qualitatively differ on CH3OH/Cu(110) as compared to D2O/Cu(110), which is ascribed to differing molecular structures for these systems. Evidence is presented for an efficient inter-molecular quenching mechanism for neutral photoexcitation of CH3Cl and CH3Br on the CH3OH/Cu(110) substrate.

Hormonal contraceptive use before and after conception in relation to preterm birth and small for gestational age: an observational cohort study

OBJECTIVE

To evaluate whether hormonal contraceptives, used before or in early pregnancy, confer increased risk of preterm birth or reduced fetal growth.

DESIGN

Population-based cohort study conducted by the Norwegian Institute of Public Health (Mother and Child Cohort Study, 1998-2008) with linkage to the Norwegian Prescription Registry and to the Medical Birth Registry of Norway.

SETTING

Norway.

POPULATION

Of the 48,615 pregnancies meeting study inclusion criteria, 44,734 pregnancies were included in the complete case analysis.

METHODS

We characterised hormonal contraception by type (combination oral, progestin-only oral, vaginal ring, transdermal, and injectable) and specific progestin component. We used generalised estimating equations to estimate the odds of adverse outcome according to formulation used. Several sensitivity analyses were conducted.

MAIN OUTCOME MEASURES

Preterm birth, small for gestational age.

RESULTS

We observed a positive association between use of a combination oral contraceptive and preterm birth for all exposure periods (e.g. adjusted odds ratio 1.21, 95% confidence interval 1.04-1.41 for last use 12 to >4 months before conception); combination contraceptives containing the progestin norethisterone were consistently related to risk. Other types of hormonal contraception were generally not associated with preterm birth; none were related to small for gestational age. Observed associations were robust to sensitivity analyses.

CONCLUSION

Hormonally active agents may exert dose-, agent-, and timing-specific effects on growth and development. We found that the particular progestin component is important when assessing the potential for adverse effects among former users of hormonal contraceptives.

Maternal hormonal contraceptive use and offspring overweight or obesity

BACKGROUND/OBJECTIVES

Experiments in animal models have shown a positive association between in utero exposure to pharmacologic sex hormones and offspring obesity. The developmental effects of such hormones on human obesity are unknown.

SUBJECTS/METHODS

Using data from a large, prospective pregnancy cohort study (n=19 652), with linkage to a national prescription registry, we evaluated the association between use of hormonal contraceptives before and after conception (defined from dispensed prescription data and characterized by last date of use relative to conception, 12 to >4 months before (n=3392), 4 to >1 months before (n=2541), 1 to >0 months before (n=2997) and 0-12 weeks after (n=567)) in relation to offspring overweight or obesity at age 3 years.

RESULTS

We observed a weak, inverse association between early pregnancy use of a combination oral contraceptive and offspring overweight or obesity at age 3 (adjusted odds ratio (OR): 0.75, 95% confidence interval (CI): 0.53, 1.08) and a positive, but imprecise, association with use of a progestin-only oral contraceptive in early pregnancy (adjusted OR: 1.26, 95% CI: 0.79, 2.02). In general, no association was observed between the use of a hormonal contraceptive before conception and offspring overweight or obesity. A sensitivity analysis comparing combination oral contraceptive users in early pregnancy to other unplanned pregnancies without hormonal contraceptive use further strengthened the inverse association (adjusted OR: 0.70, 95% CI: 0.48, 1.02). Other sensitivity analyses were conducted to evaluate the robustness of the associations observed given varying assumptions.

CONCLUSIONS

Pharmacologic sex hormones in early pregnancy may be inversely or positively associated with offspring overweight or obesity at age 3, depending on the specific formulation used. The present study provides support for the potential for environmental sources of hormonally active agents to exert developmental effects.

Control of a methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a day-care institution

This article describes an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) in two institutions for multi-handicapped children in Copenhagen. The aim of the study was to determine whether it was possible to eradicate MRSA in a setting with multi-handicapped children and staff where there was a high degree of physical interaction. This was a prospective interventional uncontrolled cohort study that took place from January 2003 to March 2005. All individuals in close contact with the two institutions and/or in close contact with an MRSA-colonized subject from the outbreak were included in the study: 38 children, 60 staff members and 12 close relatives of colonized subjects. Infection control measures included screening all individuals. When MRSA infection or colonization was found, an attempt was made to eradicate MRSA, staff education was undertaken and attempts were made to determine the route of transmission. Eleven individuals were found to be positive for MRSA (10.0%). All isolates were identical by pulsed-field gel electrophoresis and harboured the staphylococcal cassette chromosome mec (SCCmec) type IV. All colonized and infected individuals were associated with a single room in one of the institutions. MRSA was eradicated from all the colonized and infected subjects. This study shows that it is possible to control an MRSA outbreak in institutions for multi-handicapped children where there is a high degree of physical contact.

Near-UV photodissociation of oriented CH3I adsorbed on Cu(110)–I

Methyl iodide adsorbed on a Cu(110)-I surface has been found to be highly orientationally ordered. We have exploited this orientation to select different CH(3)I excited states for photodissociation by using polarized near-UV light at wavelengths of 308, 248, and 222 nm. Using p-polarized light at all three wavelengths, we find that dissociation proceeds largely via the (3)Q(0) state, consistent with the picture from gas-phase photolysis. In contrast, using s-polarized light we find contributions from the (3)Q(1) state at lambda=308 nm, the (1)Q(1) state at lambda=248 nm, and the (E,1) state at lambda=222 nm-the latter being a state that has not been implicated in gas-phase studies of CH(3)I A-band photolysis. We also note the contribution to surface photodissociation from low-energy photoelectrons causing dissociative electron attachment to adsorbed CH(3)I and have identified the promotion of direct photodissociation pathways during lambda=308 nm photolysis.

Prevalence of and detection of resistance to ampicillin and other beta-lactam antibiotics in Haemophilus influenzae in Denmark

The susceptibility of Haemophilus influenzae to penicillin V and G, ampicillin and cefuroxime was investigated by MIC, disc and tablet diffusion methods, using chocolate agar as test medium, to determine the prevalence of ampicillin-resistant isolates and the optimal method for their detection. Eighty-six isolates were clinical isolates collected prospectively from July to September 1998 and 22 isolates were clinical isolates with decreased susceptibility to ampicillin previously referred to the reference laboratory. Eighty-seven isolates were ampicillin-susceptible and 16 were ampicillin-resistant. Thirteen produced beta-lactamases. Among the consecutive isolates 12.8% were resistant. With each of the Rosco Neo-sensitabs containing penicillin G, 2.5 microg ampicillin and 33 microg ampicillin, 3 very major errors occurred (resistant isolates misinterpreted as susceptible) and 5-13 major errors (susceptible isolates misinterpreted as resistant). The AB biodisk containing ampicillin (10 microg) was superior to the penicillin V and G discs, i.e. only 1 very major error occurred and major and minor errors were infrequent. The cefuroxime disc identified 4/8 beta-lactamase-negative ampicillin-resistant isolates. Thus, for susceptibility testing with chocolate agar as test medium, the use of an inoculum of 10(5) colony-forming units, 10 microg ampicillin discs and interpretative zone diameters of > or = 28 mm indicating susceptibility and < or = 25 mm indicating resistance was found to produce reliable identification of ampicillin-resistant isolates of H. influenzae.

Epidemiology of Pseudomonas aeruginosa in cystic fibrosis and the possible role of contamination by dental equipment

Cystic fibrosis (CF) patients often suffer from Pseudomonas aeruginosa lung infection yet the source of this organism is not known. In order to determine whether CF patients might be contaminated with P. aeruginosa from dental equipment, a total of 103 water samples from 25 dental sessions in Frederiksberg Municipal Oral Health Care Service were examined. Three samples (2.9%) were positive for P. aeruginosa. Three hundred and twenty-seven water samples from 82 dental sessions from various other Municipal Oral Health Services in Denmark, attended by CF patients, were also examined. Eighteen of 327 samples (5.5%) from nine sessions (11%) were positive for P. aeruginosa. In one case, genotypically identical (RFLP, pulsed-field gel electrophoresis) P. aeruginosa strains were found both in water from the dental equipment and in the CF patients sputum. This indicates a small risk for acquiring P. aeruginosa from dental sessions, which is however equal to the yearly 'natural background' incidence (1-2%) of acquisition of P. aeruginosa in our CF centre.

High levels of complement-activation capacity in sera from patients with cystic fibrosis correlate with high levels of IgG3 antibodies to Pseudomonas aeruginosa antigens and poor lung function

Heat-stable opsonins from sera of cystic fibrosis (CF) patients were investigated for their ability to activate complement. Complement activation by Pseudomonas aeruginosa after opsonization with patient serum was examined in a complement-consumption assay. Absorption of patients' sera with formalin-treated and boiled bacteria removed specific antibodies and the complement activation decreased. We found a positive correlation between serum complement-activation ability and IgG3 antibody levels to lipopolysaccharide (LPS), alginate, and a crude mixture of P. aeruginosa antigens (sonicate) in a group of patients with high levels of anti-Pseudomonas precipitins. In the same group of patients a significant negative correlation was found between complement activation and lung function. Eighteen patients have been followed longitudinally with serum samples covering the pre-infection, the early, and the late stages of chronic infection. Patients with poor lung function showed significantly higher levels of complement-activation capacity. We conclude that patients with high levels of specific IgG3 antibodies are able to induce a high level of complement activation and then develop more aggressive pulmonary tissue damage, probably secondary to local immune complex formation.

[Biofilm, foreign bodies and chronic infections]

Most bacteria occur in the environment as sessile cells adhering to a surface, whereas a minority exists as free floating (planktonic) cells. Biofilms consist of microcolonies embedded in a polysaccharide matrix produced by the bacteria. This polysaccharide slime protects the bacteria against hostile environmental factors. Planktonic daughter cells are liberated from the surface of biofilms and may colonize new surfaces and subsequently produce new biofilms. Biofilms are often consortia of several different bacterial species. The normal microflora on the skin or on the mucous membranes in the human body occurs as a biofilm, which is removed by the shedding of old cells and by the excretion of mucus. Subsequently new cells and new mucus are colonized by biofilm forming bacteria without giving rise to any symptoms. When body surfaces with a normally occurring microflora (A) are connected by means of an implanted foreign body with body surfaces or tissue compartments without a microflora (B) e.g. bronchi, gall bladder, peritoneum, veins, then a translocation of the normal microflora from (A) to (B) may easily occur leading to acute infection, formation of new biofilms on the implanted foreign body and induction of inflammation in the environment of this biofilm. Chronic bacterial infections are frequently caused by biofilm producing bacteria and the pathogenesis of the tissue damage is dominated by a persistent immune complex mediated inflammation. Bacteria growing in biofilms cannot be eradicated by antibiotics and biofilms resist the immunological and non-specific defence mechanisms of the body.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunity to experimental Salmonella typhimurium infections in rats. Transfer of immunity with primed CD4+CD25high and CD4+CD25low T lymphocytes

The protective effect of primed CD4+ T lymphocytes against a lethal dose of 10(8) viable Salmonella typhimurium was studied in Lewis rats. Primed CD4+ T lymphocytes were obtained by inoculating Lewis rats with a non-lethal dose of 10(6) viable S. typhimurium. Four weeks after the infection, spleen CD4+ T lymphocytes were separated using magnetic microspheres coated with an antibody against the CD4 molecule (W3/25). Subsequent sorting into activated and non-activated subpopulations using the p55 alpha-chain of the interleukin-2 receptor (CD25) as an activation marker was performed by a fluorescence-activated cell sorter. Untreated Lewis rats were injected with 10(4) different primed CD4+ T-cell populations 24 h prior to the lethal dose of 10(8) viable S. typhimurium. Blood samples were drawn from the orbital plexus 1, 2, 3, and 4 weeks after the infection, and analysed for specific IgM and IgG antibodies. Cell sorting revealed that 2/3 of the primed CD4+ T lymphocytes expressed high levels of CD25. Cell transfer revealed that both CD25high and CD25low expression populations could induce immunity against a lethal dose of S. typhimurium, whilst antibody analysis revealed that antibody levels were not correlated with protection against S. typhimurium infections, although it showed that a higher and more persistent level of specific IgG antibodies was produced in animals receiving the CD4+CD25high fraction. It is concluded that 10(4) primed CD4+ T lymphocytes can induce immunity in animals challenged with a lethal dose of S. typhimurium and that antibodies do not seem to be correlated with the immunity induced. The CD4+CD25high fraction was, however, associated with a higher and more persistent level of specific IgG antibodies.

Uro-genital microbial colonization and threatening preterm delivery

OBJECTIVE

To examine whether there is a relationship between the uro-genital microbial colonization and threatening preterm delivery.

STUDY DESIGN

The microflora in the urine and endocervix was studied in 43 women with preterm labor, 45 women with preterm premature rupture of the membranes (PPROM) and 80 normal pregnant women at 26-34 weeks of gestation. Amniotic fluid was examined in 20 of the patients with preterm labor. Data were analyzed by Fisher's exact test (two-tailed).

RESULTS

The microflora in the urine was not significantly different in patients with preterm labor, PPROM and normal pregnant women. Compared with normal pregnant women, patients with preterm labor had significantly lower prevalences of corynebacteria (p < 0.05) and coagulase-negative staphylococci (p < 0.01) in the cervix, while patients with PPROM had significantly lower prevalences of lactobacilli (p < 0.05) and coagulase-negative staphylococci (p < 0.05) in the cervix. Positive amniotic fluid cultures were detected in three of the 20 patients with preterm labor who underwent transabdominal amniocentesis. Evidence of ascending colonization was found in two of these cases.

CONCLUSIONS

The microbial colonization of the urine was not associated with threatening preterm delivery. Reduced prevalences of lactobacilli, corynebacteria and coagulase-negative staphylococci in the cervix were associated with threatening preterm delivery.

[Relation between cervical conization, microbial colonization and threatening preterm labor]

The relationship between prior cervical conization, the cervical microbial colonization and threatening preterm delivery was investigated in 35 women with preterm premature rupture of the membranes (PPROM), 38 women with idiopathic preterm labor and 75 normal pregnant women at 26-34 weeks of gestation. Prior cervical conization occurred with a significantly higher frequency in PPROM patients than in patients with preterm labor (p < 0.01) and normal pregnant women (p < 0.001). The prevalence of lactobacilli was lower in patients with PPROM than in patients with preterm labor (p < 0.05) and control patients (p = 0.05)--and lower in patients with prior cervical conization than in patients without prior conization (p < 0.05). All other microorganisms occurred with the same frequencies in all groups.

CONCLUSIONS

Prior conization was associated with PPROM. Women with prior conization and women with PPROM had a reduced prevalence of lactobacilli in the cervix. The "absence" of lactobacilli may indicate changes in the cervical microflora, which could be of importance for PPROM.

Correlation between specific IgG subclass antibodies to Pseudomonas aeruginosa and opsonic activity in serum from patients with cystic fibrosis

Heat-stable opsonins from sera of patients with cystic fibrosis (CF) non-CF patients with chronic Pseudomonas aeruginosa infection, healthy children, and adults were investigated for their ability to promote phagocytosis of 35S-labeled P. aeruginosa by human polymorphonuclear neutrophils. Healthy children had significantly lower levels of opsonic activity than adults. Sera from patients with CF without chronic P. aeruginosa lung infection showed significantly higher levels of opsonic activity compared to healthy children. Sera from patients with CF in the early stage of chronic infection had similar opsonic activity as non-CF patients with chronic infection. Sera from patients with CF in the late stage of chronic infection had higher opsonic activity than other infected patients, but not different from adult controls. An inverse correlation was found between levels of specific antibodies to P. aeruginosa and opsonic activity in the group of patients in a late stage of infection. An inverse correlation was also found between levels of IgG1 and IgG3 to P. aeruginosa St-Ag and opsonic activity during the late stage of infection. Infection with P. aeruginosa in CF did not induce significantly increased opsonic activity. It seems that antibodies to P. aeruginosa may have inhibitory opsonic activity.

Complement activation by Pseudomonas aeruginosa biofilms

In chronic infections, such as the bronchopulmonary Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients, bacteria persist despite an intact host immune defense and frequent antibiotic treatment. An important reason for the persistence of the bacteria is their capacity for the biofilm mode of growth. In this study we investigated the role of biofilms in activation of complement, a major contributor to the inflammatory process. Complement activation by P. aeruginosa was examined in a complement consumption assay, production of C3 and factor B conversion products assessed by crossed immuno-electrophoresis, C5a generation tested by a PMN chemotactic assay, and terminal complement complex formation measured by ELISA. Two of the four assays showed that P. aeruginosa grown in biofilm activated complement less than planktonic bacteria, and all assays showed that activation by intact biofilms was submaximal. Factor B conversion was of low magnitude indicating the importance of the classical pathway. Complement activation by P. aeruginosa was inhibited by polymyxin B indicating that lipopolysaccharide (LPS) was the main mediator of complement activation. Immune complexes and massive influx of neutrophils are known to cause inflammatory changes in the lungs. P. aeruginosa persisting in biofilms may contribute to the constant inflammation taking place in the lungs of CF patients.

Induction of oxidative burst response in human neutrophils by immune complexes made in vitro of lipopolysaccharide and hyperimmune serum from chronically infected patients

Purified lipopolysaccharide (LPS) from Pseudomonas aeruginosa was used as an antigen for immune complex (IC) formation in vitro together with hyperimmune sera from chronically P. aeruginosa-infected patients with cystic fibrosis (CF). P. aeruginosa LPS by itself did not induce an oxidative burst in human neutrophil granulocytes (PMN)s measured by chemiluminescence (CL). This was also the case using hyperimmune CF serum alone. In contrast, P. aeruginosa LPS together with CF serum did induce a CL response. The CL responses varied depending on the sera used for IC formation, and were reduced when protein A preabsorbed sera were used. PEG precipitation of the ICs from the mixture increased the CL response. These findings indicate that the CL responses induced by the mixture of P. aeruginosa LPS and CF serum were due to IC formation and an Fc-mediated stimulation of the PMNs. It is concluded that ICs made from sera of chronically infected CF patients and purified P. aeruginosa LPS are biologically active in terms of activating PMNs, and may contribute to the lung tissue damage seen in this group of patients.

The relationship between prior cervical conization, cervical microbial colonization and preterm premature rupture of the membranes

The occurrence of prior cervical conization and the cervical microbial colonization was investigated in 38 women with idiopathic preterm labor, 35 women with preterm premature rupture of the membranes (PPROM) and 75 normal pregnant women at 26-34 weeks of gestation. Data were analyzed by Fisher's exact test (two-tailed). The frequency of prior cervical conization was significantly higher in PPROM patients compared to normal pregnant women (P < 0.001) and to patients in preterm labor (P < 0.01). Lactobacilli occurred with a lower frequency in patients with PPROM compared to patients in preterm labor (P < 0.05) and control patients (P = 0.0543)-and with a lower frequency in patients with prior cervical conization (P < 0.05). All other microorganisms occurred with the same frequencies in all groups. The absence of lactobacilli may indicate changes in the cervical flora, which could increase the risk of PPROM. Prior cervical conization may impair the antimicrobial defense-mechanisms in the cervix, which could facilitate ascending microbial colonization. This may lead to a release of prostaglandins and proteolytic enzymes and subsequently preterm labor and rupture of the membranes.

Some bacterial parameters influencing the neutrophil oxidative burst response to Pseudomonas aeruginosa biofilms

Persistence of bacteria in spite of a normal host immune system and relevant antibiotic treatment is a key problem in many chronic infections, such as the bronchopulmonary P. aeruginosa infection in cystic fibrosis patients. The capability of bacteria to establish themselves in microcolonies or biofilms is an important protective mechanism of the microorganisms. We examined the human PMN oxidative burst response to P. aeruginosa in biofilm and in planktonic form. The PMN chemiluminescence response to P. aeruginosa in biofilms was reduced to 30.5-47.5% (p less than 0.04) and the superoxide response to 85.9% (p less than 0.02) of the response to equivalent numbers of planktonic bacteria. Mechanical disruption of the biofilms before the assays elicited a significantly increased response in the chemiluminescence experiments and to nonopsonized biofilms in the superoxide anion experiments. We conclude that biofilm bacteria, although able to stimulate the PMN, result in a reduced, suboptimal response leading to lack of efficient eradication of the bacteria in the chronic infection.

Induction of beta-lactamase production in Pseudomonas aeruginosa biofilm

Imipenem induced high levels of beta-lactamase production in Pseudomonas aeruginosa biofilms. Piperacillin also induced beta-lactamase production in these biofilms but to a lesser degree. The combination of beta-lactamase production with other protective properties of the biofilm mode of growth could be a major reason for the persistence of this sessile bacterium in chronic infections.

Retrospective clinical study of hypersensitivity reactions to aztreonam and six other beta-lactam antibiotics in cystic fibrosis patients receiving multiple treatment courses

A total of 2,793 courses of treatment with seven beta-lactam antibiotics were administered to 121 cystic fibrosis patients chronically infected with Pseudomonas aeruginosa, and the patients were evaluated with respect to clinical hypersensitivity reactions. Seventy-five patients (62%) experienced 125 reactions, for an overall frequency (based on the number of courses) of 4.5%. Immediate reactions occurred in 34 patients (28.1%) during 53 courses (1.9%). The highest rate of reactions involved piperacillin (50.9% of patients), and the lowest rate involved imipenem and aztreonam (4.0% and 6.5% of patients, respectively); intermediate reaction rates were noted for carbenicillin (23.6% of patients), azlocillin (20.8%), cefsulodin (17.1%), and ceftazidime (13.0%). Cross-reactivity did not appear to be a major problem. Reactions to aztreonam seemed to be restricted to a small group of patients with a high propensity for beta-lactam hypersensitivity.

Group B streptococcal chorioamnionitis and neonatal septicemia following 8 days pivampicillin and metronidazol prophylaxis after premature rupture of membranes; a case report

A case of preterm premature rupture of the membranes (PPROM) in the 31st week of gestation is reported. Initial cultures from the cervix and urine were without pathogenic microorganisms. After 8 days of prophylactic pivampicillin and metronidazol, culture from the cervix showed profuse growth of Group B Streptococci (GBS) and the patient developed symptoms of chorioamnionitis. Cesarean section was performed and the infant presented GBS-septicemia. In spite of continued treatment with pivampicillin, culture from the cervix on day 6 post partum still showed profuse growth of GBS. Prolonged prophylactic per oral administration of broad-spectrum antibiotics after PPROM may not always protect against infectious complications. Literature is reviewed, and it is discussed whether the applied regimen in some cases even may favour the occurrence of serious infections.

Experimental Salmonella typhimurium infections in rats. III. Transfer of immunity with primed lymphocyte subpopulations

The protective effect of primed lymphocytes against a lethal dose of Salmonella typhimurium was studied in athymic and euthymic LEW rats. Primed lymphocytes were obtained by inoculating euthymic and thymus-grafted animals with a non-lethal dose of Salmonella typhimurium. Four weeks after the infection, spleen lymphocytes were separated by panning technique and antibody-coated magnetic microsphere separation using antibodies to pan T and pan B lymphocytes and subsequent sorting in a fluorescence activated cell sorter by means of monoclonal antibodies against CD4+ and CD8+ cells. Euthymic and athymic rats were injected with different doses of primed pan B, pan T, CD4+ and CD8+ T lymphocytes before inoculation with a lethal bacterial dose. Most of the animals treated with pan B, pan T or CD8+ cells died within two weeks. After treatment with primed CD4+ cells, only six of 39 animals died. Doses as low as 10(4) cells from both euthymic or thymus-grafted animals were effective, and athymic and euthymic recipients survived equally well. Four weeks after the infection both athymic and euthymic animals housed very few bacteria and had high antibacterial antibody titres. The percentages of splenic and lymph node CD4+ cells in the athymic rats were comparable to those found in the euthymic animals. The study shows that primed CD4+ lymphocytes even in very low doses are able to induce immunity against a Salmonella typhimurium infection.

Human polymorphonuclear leukocyte response to Pseudomonas aeruginosa grown in biofilms

The interaction of human neutrophils with Pseudomonas aeruginosa biofilms was examined by using a chemiluminescence assay. The biofilms induced an oxidative burst response by polymorphonuclear leukocytes which was slow and only 25% of the response to planktonic bacteria. The reduced response to P. aeruginosa biofilms could play a role in the persistence of bacteria in chronic infections.

Experimental Salmonella typhimurium infections in rats. I: Influence of thymus on the course of infection

The course of experimentally induced Salmonella typhimurium infection was studied in three groups of inbred LEW rats: homozygous +/+, athymic rnu/rnu and isogeneic thymus-grafted rnu/rnu rats. In the first experiment the animals were inoculated intraperitoneally with 10(8) bacteria and all animals became severely septicemic and died within a week of inoculation, irrespective of presence or absence of thymus. In the second experiment the animals were inoculated with 10(6) bacteria, and both euthymic and thymus-grafted animals responded with high titres of anti bacterial antibodies while these were very low in the athymic nude animals. Polyclonal antibody production was only observed in the euthymic animals and only regarding IgG. Athymic rats were not able to clear the infection, while the thymus-grafted animals reacted like euthymic rats: Very few animals housed the bacteria four weeks after inoculation, and no bacteria could be detected after four months. Immunohistochemical studies of lymphoid organs revealed that the infection caused a drop in the percentages of T non-helper cells, indicating low suppressor activity. The study shows that athymic nude rats are well suited for studies of infectious diseases in immune deficient hosts, and that whole neonatally isogeneic thymus grafting is a good way of reconstituting these animals immunologically.

Flavobacterium meningosepticum infection in a neonatal ward

An outbreak of infections due to Flavobacterium meningosepticum type C in a neonatal intensive care unit is described. During a period of two weeks, two infants developed meningitis and a third was colonized in the respiratory tract and had transient bacteremia. The two meningitis patients were treated with clindamycin, rifampicin and cefotaxime systemically, plus rifampicin intraventricularly. Bacteriological eradication was achieved within 48 h, and both infants recovered from the meningitis without apparent neurological sequelae; however, one infant died two months later of unrelated causes. Environmental surveillance cultures failed to demonstrate a reservoir for the epidemic strain, but other Flavobacterium strains were recovered. Two clinically healthy infants were found to be colonized in the nasopharynx with strains that were extremely difficult to differentiate phenotypically from the epidemic strain. Extensive characterization of strains is necessary in order to differentiate between strains and subsequently to determine a certain source of infection.