Pathogenesis of Proteus mirabilis Infection

Proteus mirabilis, a Gram-negative rod-shaped bacterium most noted for its swarming motility and urease activity, frequently causes catheter-associated urinary tract infections (CAUTIs) that are often polymicrobial. These infections may be accompanied by urolithiasis, the development of bladder or kidney stones due to alkalinization of urine from urease-catalyzed urea hydrolysis. Adherence of the bacterium to epithelial and catheter surfaces is mediated by 17 different fimbriae, most notably MR/P fimbriae. Repressors of motility are often encoded by these fimbrial operons. Motility is mediated by flagella encoded on a single contiguous 54-kb chromosomal sequence. On agar plates, P. mirabilis undergoes a morphological conversion to a filamentous swarmer cell expressing hundreds of flagella. When swarms from different strains meet, a line of demarcation, a "Dienes line," develops due to the killing action of each strain's type VI secretion system. During infection, histological damage is caused by cytotoxins including hemolysin and a variety of proteases, some autotransported. The pathogenesis of infection, including assessment of individual genes or global screens for virulence or fitness factors has been assessed in murine models of ascending urinary tract infections or CAUTIs using both single-species and polymicrobial models. Global gene expression studies performed in culture and in the murine model have revealed the unique metabolism of this bacterium. Vaccines, using MR/P fimbria and its adhesin, MrpH, have been shown to be efficacious in the murine model. A comprehensive review of factors associated with urinary tract infection is presented, encompassing both historical perspectives and current advances.

Merging mythology and morphology: the multifaceted lifestyle of Proteus mirabilis

Proteus mirabilis, named for the Greek god who changed shape to avoid capture, has fascinated microbiologists for more than a century with its unique swarming differentiation, Dienes line formation and potent urease activity. Transcriptome profiling during both host infection and swarming motility, coupled with the availability of the complete genome sequence for P. mirabilis, has revealed the occurrence of interbacterial competition and killing through a type VI secretion system, and the reciprocal regulation of adhesion and motility, as well as the intimate connections between metabolism, swarming and virulence. This Review addresses some of the unique and recently described aspects of P. mirabilis biology and pathogenesis, and emphasizes the potential role of this bacterium in single-species and polymicrobial urinary tract infections.

The effects of norepinephrine on hemodynamics and renal function in severe septic shock states

OBJECTIVE

To investigate the effect of norepinephrine (NE) on hemodynamics, oxygen metabolism and renal function in patients with severe septic shock.

DESIGN

Prospective study.

SETTING

Post-operative ICU in a municipal general hospital.

PATIENTS

The study included 56 patients with extreme low resistance states due to abdominal sepsis, who remained hypertensive (MAP < 60 mmHg) despite optimal fluid therapy and dopamine > 20 micrograms/kg/min and cumulative doses of dopamine and dobutamine > 30 micrograms/kg/min, respectively.

INTERVENTIONS

After registration of baseline values dopamine was reduced to 2.5 micrograms/kg/min, and norepinephrine was administered starting at a dose of 0.05 micrograms/kg/min until a mean arterial pressure of more than 60 mmHg could be maintained.

MEASUREMENTS AND RESULTS

During norepinephrine infusion (dosage ranging between 0.1-2 micrograms/kg/min, mean dose rate: 0.4 micrograms/kg/min) mean arterial pressure and systemic vascular resistance index increased significantly (p < 0.001). After 8 h a significant increase in stroke volume (p < 0.05) and decrease in heart rate (p < 0.05) could be observed. There was no significant change in cardiac index (CI), oxygen delivery (O2AVI) and oxygen consumption (VO2I). Creatinine clearance increased significantly (p < 0.005) from a control value of 75 +/- 37 ml/min to 102 +/- 43 ml/min after 48 h NE-treatment.

CONCLUSION

Our results suggest that norepinephrine can be used safely in the treatment of severe septic shock states. Mean arterial pressure and glomerular filtration rate improved markedly without deleterious effects on CI, O2AVI and VO2I.

Coinfection with Haemophilus influenzae promotes pneumococcal biofilm formation during experimental otitis media and impedes the progression of pneumococcal disease

BACKGROUND

Otitis media is an extremely common pediatric infection and is mostly caused by bacteria that are carried within the nasopharyngeal microbiota. It is clear that most otitis media cases involve simultaneous infection with multiple agents.

METHODS

Chinchillas were infected with nontypeable Haemophilus influenzae, Streptococcus pneumoniae, or a combination of both organisms, and the course of disease was compared. In vitro experiments were also performed to address how coinfection impacts biofilm formation.

RESULTS

The incidence of systemic disease was reduced in coinfected animals, compared with those infected with pneumococcus alone. Pneumococci were present within surface-attached biofilms in coinfected animals, and a greater proportion of translucent colony type was observed in the coinfected animals. Because this colony type has been associated with pneumococcal biofilms, the impact of coinfection on pneumococcal biofilm formation was investigated. The results clearly show enhanced biofilm formation in vitro by pneumococci in the presence of H. influenzae.

CONCLUSIONS

Based on these data, we conclude that coinfection with H. influenzae facilitates pneumococcal biofilm formation and persistence on the middle ear mucosal surface. This enhanced biofilm persistence correlates with delayed emergence of opaque colony variants within the bacterial population and a resulting decrease in systemic infection.

Genome-wide transposon mutagenesis of Proteus mirabilis: Essential genes, fitness factors for catheter-associated urinary tract infection, and the impact of polymicrobial infection on fitness requirements

The Gram-negative bacterium Proteus mirabilis is a leading cause of catheter-associated urinary tract infections (CAUTIs), which are often polymicrobial. Numerous prior studies have uncovered virulence factors for P. mirabilis pathogenicity in a murine model of ascending UTI, but little is known concerning pathogenesis during CAUTI or polymicrobial infection. In this study, we utilized five pools of 10,000 transposon mutants each and transposon insertion-site sequencing (Tn-Seq) to identify the full arsenal of P. mirabilis HI4320 fitness factors for single-species versus polymicrobial CAUTI with Providencia stuartii BE2467. 436 genes in the input pools lacked transposon insertions and were therefore concluded to be essential for P. mirabilis growth in rich medium. 629 genes were identified as P. mirabilis fitness factors during single-species CAUTI. Tn-Seq from coinfection with P. stuartii revealed 217/629 (35%) of the same genes as identified by single-species Tn-Seq, and 1353 additional factors that specifically contribute to colonization during coinfection. Mutants were constructed in eight genes of interest to validate the initial screen: 7/8 (88%) mutants exhibited the expected phenotypes for single-species CAUTI, and 3/3 (100%) validated the expected phenotypes for polymicrobial CAUTI. This approach provided validation of numerous previously described P. mirabilis fitness determinants from an ascending model of UTI, the discovery of novel fitness determinants specifically for CAUTI, and a stringent assessment of how polymicrobial infection influences fitness requirements. For instance, we describe a requirement for branched-chain amino acid biosynthesis by P. mirabilis during coinfection due to high-affinity import of leucine by P. stuartii. Further investigation of genes and pathways that provide a competitive advantage during both single-species and polymicrobial CAUTI will likely provide robust targets for therapeutic intervention to reduce P. mirabilis CAUTI incidence and severity.

Proteus mirabilis is a common cause of single-species and polymicrobial catheter-associated urinary tract infections (CAUTIs). Prior studies have uncovered P. mirabilis virulence factors for single-species ascending UTI, but little is known concerning pathogenesis during CAUTI or polymicrobial infection. Using transposon insertion-site sequencing (Tn-Seq), we performed a global assessment of P. mirabilis fitness factors for CAUTI while simultaneously determining how coinfection with another CAUTI pathogen, Providencia stuartii, alters P. mirabilis fitness requirements. This approach provides six important contributions to the field: 1) the first global estimation of P. mirabilis genes essential for growth, 2) validation of a role for known P. mirabilis fitness factors during CAUTI, 3) identification of novel fitness factors, 4) identification of core fitness factors for both single-species and polymicrobial CAUTI, 5) identification of single-species fitness factors that are complemented during polymicrobial infection, and 6) identification of factors that only provide a competitive advantage during polymicrobial infection. We further demonstrate that the CAUTI model can be used to examine the interplay between fitness requirements of both species during coinfection. Investigation of fitness requirements for other pathogens during single-species and polymicrobial CAUTI will elucidate complex interactions that contribute to disease severity and uncover conserved targets for therapeutic intervention.

Carcinoma showing thymic-like elements--a rare malignancy of the thyroid gland

BACKGROUND

Carcinoma showing thymic-like elements (CASTLE) is a rare tumour of the thyroid of thymic origin. The histological appearance of this tumour may be similar to that of squamous cell carcinoma of the thyroid, but outcome associated with CASTLE is more favourable.

METHODS

A systematic literature review was conducted for case reports on CASTLE. A text word search of the Medline database was made with a manual search of the citations from these references. Twenty-two case reports were found.

RESULTS

In five patients with tumour-negative lymph nodes no local or distant recurrence was observed. Seventeen patients had unknown or involved lymph nodes. Two patients were excluded from further study: one had no follow-up and one was treated by irradiation only. Of the remaining 15, six had local, three had distant and two had local and distant recurrence. In patients with involved or unknown lymph node status, local recurrence was noted in one of five patients treated by surgery and irradiation, and in seven of ten patients treated by surgery alone. Irradiation or systemic chemotherapy was given to four patients with recurrent tumours, with variable response.

CONCLUSION

CASTLE with tumour-negative lymph nodes has a low risk of recurrence and surgery without adjuvant therapy is sufficient. Radiotherapy seems indicated when lymph nodes are tumour positive and can be effective for recurrent tumours. In selected patients surgery for recurrent tumour can improve quality of life and outcome.

Prognostic factors for survival in colonic perforation

Colonic perforation is an abdominal emergency with high morbidity and mortality. This retrospective study was performed to evaluate the prognostic relevance of several factors and to characterize patients at high risk. One hundred and twelve patients (61 women, 51 men) were treated for colonic perforation from 1979 to 1992. Diverticulitis [65 patients (58%)] and carcinoma [24 patients (21%)] were the commonest pathology. In 62 cases (55%) perforation was found to be covered; 50 (45%) times it was free. 34 (30%) patients had diffuse peritonitis. Resection with primary anastomosis was performed 43 times (7 times with a protective colostomy). Resection without restoration of the intestinal continuity was carried out 53 times (including 49 Hartmann operations). Suture with drainage was performed 16 times mainly after iatrogenic perforation (8 times with a colostomy). The overall mortality was 19.6% (22 patients). The prognostic importance of various factors was investigated by univariate analysis (Wilcoxon and Chi-square test) and stepwise logistic regression including sex, age, underlying disease, localization and type of perforation, degree of peritonitis, pre- or postoperative organ failure, surgical procedure, reoperation, sepsis and the Mannheimer Peritonitis Index (MPI) score. Age over 65 years (relative risk 4.6, P = 0.0089), organ failure (relative risk 40, P = 0.001) and MPI (relative risk for an increase of 10 points 2.72, P = 0.001) proved to be the only risk factors of significance. The patient's course is determined by the septic state, while the underlying pathology and degree of peritonitis did not significantly influence survival.

Increased incidence of urolithiasis and bacteremia during Proteus mirabilis and Providencia stuartii coinfection due to synergistic induction of urease activity

BACKGROUND

Catheter-associated urinary tract infections (CaUTIs) are the most common hospital-acquired infections worldwide and are frequently polymicrobial. The urease-positive species Proteus mirabilis and Providencia stuartii are two of the leading causes of CaUTIs and commonly co-colonize catheters. These species can also cause urolithiasis and bacteremia. However, the impact of coinfection on these complications has never been addressed experimentally.

METHODS

A mouse model of ascending UTI was utilized to determine the impact of coinfection on colonization, urolithiasis, and bacteremia. Mice were infected with P. mirabilis or a urease mutant, P. stuartii, or a combination of these organisms. In vitro experiments were conducted to assess growth dynamics and impact of co-culture on urease activity.

RESULTS

Coinfection resulted in a bacterial load similar to monospecies infection but with increased incidence of urolithiasis and bacteremia. These complications were urease-dependent as they were not observed during coinfection with a P. mirabilis urease mutant. Furthermore, total urease activity was increased during co-culture.

CONCLUSIONS

We conclude that P. mirabilis and P. stuartii coinfection promotes urolithiasis and bacteremia in a urease-dependent manner, at least in part through synergistic induction of urease activity. These data provide a possible explanation for the high incidence of bacteremia resulting from polymicrobial CaUTI.

RbsB (NTHI_0632) mediates quorum signal uptake in nontypeable Haemophilus influenzae strain 86-028NP

Nontypeable Haemophilus influenzae (NTHI) is a respiratory commensal and opportunistic pathogen, which persists within biofilms on airway mucosal surfaces. For many species, biofilm formation is impacted by quorum signalling. Our prior work shows that production of autoinducer-2 (AI-2) promotes biofilm development and persistence for NTHI 86-028NP. NTHI 86-028NP encodes an ABC transporter annotated as a ribose transport system that includes a protein (RbsB) with similarity to the Escherichia coli LsrB and Aggregatibacter actinomycetemcomitans RbsB proteins that bind AI-2. In this study, inactivation of rbsB significantly reduced uptake of AI-2 and the AI-2 precursor dihydroxypentanedione (DPD) by NTHI 86-028NP. Moreover, DPD uptake was not competitively inhibited by ribose or other pentose sugars. Transcript levels of rbsB increased in response to DPD and as bacteria approached stationary-phase growth. The NTHI 86-028NP rbsB mutant also formed biofilms with significantly reduced thickness and total biomass and reduced surface phosphorylcholine, similar to a luxS mutant. Infection studies revealed that loss of rbsB impaired bacterial persistence in the chinchilla middle ear, similar to our previous results with luxS mutants. Based on these data, we conclude that in NTHI 86-028NP, RbsB is a LuxS/AI-2 regulated protein that is required for uptake of and response to AI-2.

Patients' assessment and recall of surgical information after laparoscopic cholecystectomy

BACKGROUND

While patients' needs for adequate preoperative information are generally recognized, data evaluating the effectiveness of the consultation before laparoscopic cholecystectomy have not been published until today. This prospective study was performed to investigate the success of preoperative information.

METHODS

A combination of oral and written information was given to all patients in two interviews. Information concentrated on indications for surgery, operative procedures, and risks. Patients were asked to answer questionnaires 5 days after the operation.

RESULTS

From January 1996 to January 1997, 200 patients were interviewed. Ninety-seven percent indicated to wish detailed information. Eighty-four percent indicated a high level of satisfaction with the presented information. While the levels of knowledge concerning indications for surgery and procedures were satisfactory in 85 and 51% respectively, only 30% were able to name at least one risk factor of laparoscopic cholecystectomy.

CONCLUSION

This study demonstrated that patients' evaluation of their surgical knowledge and the process by which it was communicated to them did not correspond to their ability to recall this information after surgery.

Association of microsomal epoxide hydrolase polymorphisms and lung cancer risk

Microsomal epoxide hydrolase (mEH) plays a dual role in the detoxification and activation of tobacco procarcinogens. Two polymorphisms affecting enzyme activity have been described in the exons 3 and 4 of the mEH gene, which result in the substitution of amino acids histidine to tyrosine at residue 113, and arginine to histidine at residue 139, respectively. We performed a hospital-based case-control study consisting of 277 newly diagnosed lung cancer patients and 496 control subjects to investigate a possible association between these two polymorphisms and lung cancer risk. The polymorphisms were determined by polymerase chain reaction/restriction fragment length polymorphism and TaqMan assay using DNA from peripheral white blood cells. Logistic regression was performed to calculate odds ratios (ORs), confidence limits (CL) and to control for possible confounders. The exon 3 polymorphism of the mEH gene was associated with a significantly decreased risk of lung cancer. The adjusted OR, calculated relative to subjects with the Tyr113/Tyr113 wild type, for the His113/His113 genotype was 0.38 (95% CL 0.20-0.75). An analysis according to histological subtypes revealed a statistically significant association for adenocarcinomas; the adjusted OR for the His113/His113 genotype was 0.40 (95% CL 0.17-0.94). In contrast, no relationship between the exon 4 polymorphism and lung cancer risk was found. The adjusted OR, calculated relative to the His139/His139 wild type, was for the Arg139/Arg139 genotype 1.83 (0.76-4.44). Our results support the hypothesis that genetically reduced mEH activity may be protective against lung cancer.

Divergent mechanisms for passive pneumococcal resistance to β-lactam antibiotics in the presence of Haemophilus influenzae

BACKGROUND

Otitis media, for which antibiotic treatment failure is increasingly common, is a leading pediatric public health problem.

METHODS

In vitro and in vivo studies using the chinchilla model of otitis media were performed using a β-lactamase-producing strain of nontypeable Haemophilus influenzae (NTHi 86-028NP) and an isogenic mutant deficient in β-lactamase production (NTHi 86-028NP bla) to define the roles of biofilm formation and β-lactamase production in antibiotic resistance. Coinfection studies were done with Streptococcus pneumoniae to determine if NTHi provides passive protection by means of β-lactamase production, biofilm formation, or both.

RESULTS

NTHi 86-028NP bla was resistant to amoxicillin killing in biofilm studies in vitro; however, it was cleared by amoxicillin treatment in vivo, whereas NTHi 86-028NP was unaffected in either system. NTHi 86-028NP protected pneumococcus in vivo in both the effusion fluid and bullar homogenate. NTHi 86-028NP bla and pneumococcus were both recovered from the surface-associated bacteria of amoxicillin-treated animals; only NTHi 86-028NP bla was recovered from effusion.

CONCLUSIONS

Based on these studies, we conclude that NTHi provides passive protection for S. pneumoniae in vivo through 2 distinct mechanisms: production of β-lactamase and formation of biofilm communities.

How Often Do Clinically Diagnosed Catheter-Associated Urinary Tract Infections in Nursing Homes Meet Standardized Criteria?

OBJECTIVES

To determine the relationship between clinically diagnosed catheter-associated urinary tract infection (CAUTI) and standardized criteria and to assess microorganism-level differences in symptom burden in a cohort of catheterized nursing home (NH) residents.

DESIGN

Post hoc analysis of a prospective longitudinal study.

SETTING

Twelve NHs in southeast Michigan.

PARTICIPANTS

NH residents with indwelling urinary catheters (n = 233; 90% white, 52% male, mean age 73.7).

MEASUREMENTS

Clinical and demographic data, including CAUTI epidemiology and symptoms, were obtained at study enrollment, 14 days, and monthly thereafter for up to 1 year.

RESULTS

One hundred twenty participants with an indwelling catheter (51%) were prescribed systemic antibiotics for 182 clinically diagnosed CAUTIs. Common signs and symptoms were acute change in mental status (28%), fever (21%), and leukocytosis (13%). Forty percent of clinically diagnosed CAUTIs met Loeb's minimum criteria, 32% met National Health Safety Network (NHSN) criteria, and 50% met Loeb's minimum or NHSN criteria. CAUTIs involving Staphylococcus aureus and Enterococcus spp. were least likely to meet criteria. CAUTIs involving Klebsiella pneumoniae were most likely to meet Loeb's minimum criteria (odds ratio (OR) = 9.7, 95% confidence interval (CI) = 2.3-40.3), possibly because of an association with acute change in mental status (OR = 5.9, 95% CI = 1.8-19.4).

CONCLUSION

Fifty percent of clinically diagnosed CAUTIs met standardized criteria, which represents an improvement in antibiotic prescribing practices. At the microorganism level, exploratory data indicate that symptom burden may differ between microorganisms. Exploration of CAUTI signs and symptoms associated with specific microorganisms may yield beneficial information to refine existing tools to guide appropriate antibiotic treatment.

Longitudinal Assessment of Multidrug-Resistant Organisms in Newly Admitted Nursing Facility Patients: Implications for an Evolving Population

Background

The spread of multidrug-resistant organisms (MDROs) is a global concern, and much about transmission in healthcare systems remains unknown. To reduce hospital stays, nursing facilities (NFs) have increasingly assumed care of post-acute populations. We estimate the prevalence of MDRO colonization in NF patients on enrollment and discharge to community settings, risk factors for colonization, and rates of acquiring MDROs during the stay.

Methods

We conducted a prospective, longitudinal cohort study of newly admitted patients in 6 NFs in southeast Michigan using active microbial surveillance of multiple anatomic sites sampled at enrollment, days 14 and 30, and monthly thereafter for up to 6 months.

Results

We enrolled 651 patients and collected 7526 samples over 1629 visits, with an average of 29 days of follow-up per participant. Nearly all participants were admitted for post-acute care (95%). More than half (56.8%) were colonized with MDROs at enrollment: methicillin-resistant Staphylococcus aureus (MRSA), 16.1%; vancomycin-resistant enterococci (VRE), 33.2%; and resistant gram-negative bacilli (R-GNB), 32.0%. Risk factors for colonization at enrollment included prolonged hospitalization (>14 days), functional disability, antibiotic use, or device use. Rates per 1000 patient-days of acquiring a new MDRO were MRSA, 3.4; VRE, 8.2; and R-GNB, 13.6. MDRO colonization at discharge was similar to that at enrollment (56.4%): MRSA, 18.4%; VRE, 30.3%; and R-GNB, 33.6%.

Conclusions

Short-stay NF patients exhibit a high prevalence of MDROs near the time of admission, as well as at discharge, and may serve as a reservoir for spread in other healthcare settings. Future interventions to reduce MDROs should specifically target this population.

Perforated colorectal cancer

PURPOSE

Perforations are rare but serious complications of colorectal cancer, with mortality rates of 30 to 40 percent. The aim of this retrospective study was to investigate possible indicators of prognosis and causes of death and to evaluate the risk of this complication by comparing results in perforated tumors with uncomplicated cancers or large-bowel perforations attributable to benign causes.

METHODS

Data of postoperative and long-term results of 35 patients with perforated colorectal cancers were compared in 868 patients with uncomplicated cancers and 130 patients with large-bowel perforations attributable to benign diseases. Postoperative survival in perforated cancers (mortality, 40 percent) was determined by degree of peritonitis, septic state, and tumor stages.

RESULTS

Comparison of the three groups demonstrated advanced tumor stages, a higher rate of septic organ failures, and higher mortality rates for perforated cancers. Long-term survival depended on tumor stages but did not differ in perforated and uncomplicated cancers.

CONCLUSIONS

A cumulative effect of malignancy and sepsis may be responsible for the high postoperative mortality in malignant perforation. Patients with perforated cancers represent the highest risk group in colonic perforation.

Enterococcus faecalis Polymicrobial Interactions Facilitate Biofilm Formation, Antibiotic Recalcitrance, and Persistent Colonization of the Catheterized Urinary Tract

Indwelling urinary catheters are common in health care settings and can lead to catheter-associated urinary tract infection (CAUTI). Long-term catheterization causes polymicrobial colonization of the catheter and urine, for which the clinical significance is poorly understood. Through prospective assessment of catheter urine colonization, we identified Enterococcus faecalis and Proteus mirabilis as the most prevalent and persistent co-colonizers. Clinical isolates of both species successfully co-colonized in a murine model of CAUTI, and they were observed to co-localize on catheter biofilms during infection. We further demonstrate that P. mirabilis preferentially adheres to E. faecalis during biofilm formation, and that contact-dependent interactions between E. faecalis and P. mirabilis facilitate establishment of a robust biofilm architecture that enhances antimicrobial resistance for both species. E. faecalis may therefore act as a pioneer species on urinary catheters, establishing an ideal surface for persistent colonization by more traditional pathogens such as P. mirabilis.

Laparoscopically assisted implantation of ventriculoperitoneal shunts

Laparoscopically-assisted minimally invasive procedures have been applied to a broad spectrum of abdominal interventions. Neurosurgeons performing ventriculoperitoneal shunt operations for hydrocephalus used to place the peritoneal catheter by performing an upper abdominal midline or subcostal incision. In this report, to reduce the patient's inconvenience caused by the laparotomy wound, three consecutive ventriculoperitoneal shunts were implanted, assisted by laparoscopy. By means of three incisions (one 10 mm supraumbilical for the camera and two 5 mm in the right hypochondric region for instrumentation) the peritoneal catheter was placed next to the epiploic foramen. After subcutaneous pull-through of the catheter to the right supraclavicular region, the operation was continued by the neurosurgeon. The postoperative course was uneventful in all cases. The patients were dismissed 3-7 days after surgery. Short time follow-up (212, 202, and 169 days after surgery) showed no complications and perfect function of the ventriculoperitoneal shunts.

Pneumocystis carinii colonization in the absence of immunosuppression

A prospective study was undertaken to evaluate the incidence and the course of Pneumocystis carinii colonization in immunocompetent patients with severe pulmonary diseases. A further perspective was to determine the diagnostic values of different detection methods. Bronchoalveolar lavage fluid samples from 77/838 adult HIV-negative patients were examined by Diff-Quik stain, direct immunofluorescence test and polymerase chain reaction. All Diff-Quik stains were negative, but direct immunofluorescence tests and polymerase chain reactions were positive in the samples of 5 patients. The normal number of granulocytes and CD4+T- lymphocytes (median 810 cells/microliters) and normal values of immunoglobulins proved the relative competence of the immune systems of the 77 patients. Although none of these patients received any agent effective against P. carinii, none developed a P. carinii pneumonia within a 120.5-d surveillance period. Nosocomial transmission could be excluded. As the colonization with P. carinii did not result in pneumonia in immunocompetent patients, clinically silent carriers have to be assumed. In non-AIDS patients, sensitive detection methods have to be used to identify colonized persons.

Successful treatment of severe respiratory papillomatosis with intravenous cidofovir and interferon alpha-2b

In contrast to uncomplicated juvenile laryngeal papillomas which may regress spontaneously, papillomatosis involving pulmonary parenchyma is associated with a poor outcome. This report represents the case of a 34 yr-old female in whom respiratory papillomatosis resulted in voice problems and recurrent pneumonias due to bronchial obstruction. A computed tomographic scan of the chest showed worsening bilateral round cavitating consolidations. Bronchoscopy revealed polypoid lesions of the right vocal cord and the midtrachea which were confirmed as squamous papillomatosis by histology. Interferon (IFN)alpha-2b treatment was inefficient as was cidofovir monotherapy on a maintenance basis. Six months of IFN-alpha-2b and cidofovir in combination led to a complete macroscopic disappearance of the laryngeal lesions and to an impressive regression of the tracheal papillomas and of the intrapulmonary consolidations. These data provide support that severe respiratory papillomatosis can be safely treated by interferon alpha-2b and cidofovir in combination. Probably the same mechanisms as in ribavirin plus interferon alpha-2b, in the treatment of patients with chronic hepatitis C, are responsible for the therapeutic success in this case.

Polymicrobial interactions in the urinary tract: is the enemy of my enemy my friend?

The vast majority of research pertaining to urinary tract infection has focused on a single pathogen in isolation, and predominantly Escherichia coli. However, polymicrobial urine colonization and infection are prevalent in several patient populations, including individuals with urinary catheters. The progression from asymptomatic colonization to symptomatic infection and severe disease is likely shaped by interactions between traditional pathogens as well as constituents of the normal urinary microbiota. Recent studies have begun to experimentally dissect the contribution of polymicrobial interactions to disease outcomes in the urinary tract, including their role in development of antimicrobial-resistant biofilm communities, modulating the innate immune response, tissue damage, and sepsis. This review aims to summarize the epidemiology of polymicrobial urine colonization, provide an overview of common urinary tract pathogens, and present key microbe-microbe and host-microbe interactions that influence infection progression, persistence, and severity.

A simple and robust method for the complete dissociation of HIV-1 p24 and other antigens from immune complexes in serum and plasma samples

Accuracy of antigen determination in human plasma samples is often adversely affected by immune complex formation between antigens (e.g., HIV-1 p24 protein) and specific antibodies. In this study we describe an optimized method for complete immune complex dissociation (ICD) in plasma. This method is based on heat denaturation of antibodies and utilizes a defined solution of sodium dodecyl sulfate (SDS) and diethylenetriaminepentaacetic acid (DTPA) as diluent. The efficiency of this procedure for ICD was compared with those of published methods, employing heat denaturation alone and acidification. Plasma samples from patients participating in anti-retroviral treatments and samples reconstituted in vitro were treated and analyzed in parallel. HIV-1 p24 antigen was determined by quantitative enzyme-linked immunosorbent assay (ELISA). In 312 samples from 97 patients, antigenemia was found in 44.9% when measured directly and in 87.2% after this treatment. In a subset of 56 samples, 21.4% tested positive prior to treatment, while after either novel treatment, heat denaturation or acidification, these samples tested positive in 80.4%, 62.5% and 60.7%, respectively. In 94% of cases viral RNA was detected. This improved procedure for ICD provides a reliable and convenient method for complete and accurate p24 antigen detection in human plasma and is applicable to commercially available test kits.

Twin arginine translocation, ammonia incorporation, and polyamine biosynthesis are crucial for Proteus mirabilis fitness during bloodstream infection

The Gram-negative bacterium Proteus mirabilis is a common cause of catheter-associated urinary tract infections (CAUTI), which can progress to secondary bacteremia. While numerous studies have investigated experimental infection with P. mirabilis in the urinary tract, little is known about pathogenesis in the bloodstream. This study identifies the genes that are important for survival in the bloodstream using a whole-genome transposon insertion-site sequencing (Tn-Seq) approach. A library of 50,000 transposon mutants was utilized to assess the relative contribution of each non-essential gene in the P. mirabilis HI4320 genome to fitness in the livers and spleens of mice at 24 hours following tail vein inoculation compared to growth in RPMI, heat-inactivated (HI) naïve serum, and HI acute phase serum. 138 genes were identified as ex vivo fitness factors in serum, which were primarily involved in amino acid transport and metabolism, and 143 genes were identified as infection-specific in vivo fitness factors for both spleen and liver colonization. Infection-specific fitness factors included genes involved in twin arginine translocation, ammonia incorporation, and polyamine biosynthesis. Mutants in sixteen genes were constructed to validate both the ex vivo and in vivo results of the transposon screen, and 12/16 (75%) exhibited the predicted phenotype. Our studies indicate a role for the twin arginine translocation (tatAC) system in motility, translocation of potential virulence factors, and fitness within the bloodstream. We also demonstrate the interplay between two nitrogen assimilation pathways in the bloodstream, providing evidence that the GS-GOGAT system may be preferentially utilized. Furthermore, we show that a dual-function arginine decarboxylase (speA) is important for fitness within the bloodstream due to its role in putrescine biosynthesis rather than its contribution to maintenance of membrane potential. This study therefore provides insight into pathways needed for fitness within the bloodstream, which may guide strategies to reduce bacteremia-associated mortality.

Complications after surgery for necrotising pancreatitis: risk factors and prognosis

OBJECTIVE

To evaluate risk factors, results of treatment, and prognostic influence of complications on survival from acute necrotising pancreatitis.

DESIGN

Retrospective study of prospectively collected data.

SETTING

Tertiary referral centre, Austria.

SUBJECTS

100 consecutive patients operated on for necrotising pancreatitis confirmed by dynamic angio-computed tomography from 1988-1997.

INTERVENTIONS

77 patients were operated on acutely followed by open management, and in 23 the operations were delayed.

MAIN OUTCOME MEASURES

Morbidity, mortality, factors predisposing to complications, prognostic effect of complications on survival.

RESULTS

Acute operations, alcoholic origin, APACHE II scores of > or = 10 on admission, and organ dysfunction on admission were independent factors that predisposed patients to complications. Colonic necrosis (n = 17) bleeding (n = 12) and intestinal fistulisation (n = 10) predominated. The overall mortality of complicated pancreatic necrosis was higher among patients admitted with surgical complications than in those who were not, but not significantly so (12/33 compared with 7/44 p = 0.06). Colonic necrosis (mortality 53%, relative risk: 2.45, p = 0.01), however, seemed to be of prognostic relevance.

CONCLUSIONS

Complications are common in severe necrotising pancreatitis leading to organ dysfunction and need for acute operations. Colonic necrosis is an independent prognostic factor for survival.