The Coli Surface Antigen CS3 of Enterotoxigenic Escherichia coli Is Differentially Regulated by H-NS, CRP, and CpxRA Global Regulators.

Enterotoxigenic Escherichia coli produces a myriad of adhesive structures collectively named colonization factors (CFs). CS3 is a CF, which is assembled into fine wiry fibrillae encoded by the cstA-H gene cluster. In this work we evaluated the influence of environmental cues such as temperature, osmolarity, pH, and carbon source on the expression of CS3 genes. The transcription of cstH major pilin gene was stimulated by growth of the bacteria in colonization factor broth at 37°C; the presence of glycerol enhanced cstH transcription, while glucose at high concentration, high osmolarity, and the depletion of divalent cations such as calcium and magnesium repressed cstH expression. In addition, we studied the role of H-NS, CpxRA, and CRP global regulators in CS3 gene expression. H-NS and CpxRA acted as repressors and CRP as an activator of cstH expression. Under high osmolarity, H-NS, and CpxRA were required for cstH repression. CS3 was required for both, bacterial adherence to epithelial cells and biofilm formation. Our data strengthens the existence of a multi-factorial regulatory network that controls transcription of CS3 genes in which global regulators, under the influence of environmental signals, control the production of this important intestinal colonization factor.

Gene Expression Profiling of Transcription Factors of Helicobacter pylori under Different Environmental Conditions.

Helicobacter pylori is a Gram-negative bacterium that colonizes the human gastric mucosa and causes peptic ulcers and gastric carcinoma. H. pylori strain 26695 has a small genome (1.67 Mb), which codes for few known transcriptional regulators that control bacterial metabolism and virulence. We analyzed by qRT-PCR the expression of 16 transcriptional regulators in H. pylori 26695, including the three sigma factors under different environmental conditions. When bacteria were exposed to acidic pH, urea, nickel, or iron, the sigma factors were differentially expressed with a particularly strong induction of fliA. The regulatory genes hrcA, hup, and crdR were highly induced in the presence of urea, nickel, and iron. In terms of biofilm formation fliA, flgR, hp1021, fur, nikR, and crdR were induced in sessile bacteria. Transcriptional expression levels of rpoD, flgR, hspR, hp1043, and cheY were increased in contact with AGS epithelial cells. Kanamycin, chloramphenicol, and tetracycline increased or decreased expression of regulatory genes, showing that these antibiotics affect the transcription of H. pylori. Our data indicate that environmental cues which may be present in the human stomach modulate H. pylori transcription.

Antibiotic resistance of gram-negative bacilli isolated from pediatric patients with nosocomial bloodstream infections in a Mexican tertiary care hospital.

BACKGROUND: Gram-negative bacilli are the most common bacteria causing nosocomial bloodstream infections (NBSIs) in Latin American countries. METHODS: The antibiotic resistance profiles of Gram-negative bacilli isolated from blood cultures in pediatric patients with NBSIs over a 3-year period in a tertiary care pediatric hospital in Mexico City were determined using the VITEK-2 system. Sixteen antibiotics were tested to ascertain the resistance rate and the minimum inhibitory concentration using the Clinical Laboratory Standards Institute (CLSI) broth micro-dilution method as a reference. RESULTS: A total of 931 isolates were recovered from 847 clinically significant episodes of NBSI. Of these, 477 (51.2%) were caused by Gram-negative bacilli. The most common Gram-negative bacilli found were Klebsiella pneumoniae (30.4%), Escherichia coli (18.9%), Enterobacter cloacae (15.1%), Pseudomonas aeruginosa (9.9%), and Acinetobacter baumannii (4.6%). More than 45 and 60% of the K. pneumoniae and E. coli isolates, respectively, were resistant to cephalosporins, and 64% of the E. coli isolates were resistant to fluoroquinolones. A. baumannii exhibited low rates of resistance to antibiotics tested. In the E. cloacae and P. aeruginosa isolates, no rates of resistance higher than 38% were observed. CONCLUSIONS: In this study, we found that the proportion of NBSIs due to antibiotic-resistant organisms is increasing in a tertiary care pediatric hospital of Mexico.

Effectiveness of four manual breast pumps for mothers after preterm delivery in a developing country.

BACKGROUND: Hospital-grade electric pumps may be useful to initiate and sustain adequate milk production for mothers who are unable to breast-feed their babies hospitalized at special care nurseries (SCN), but their cost is generally not affordable for SCN and for most mothers in developing countries. Therefore, manual breast pumps (MBPs) can be an alternative, but the best option is unknown considering clinical parameters and mothers' preference from among currently available MBPs. OBJECTIVE: To compare the effectiveness of four MBPs in terms of milk volume, nutritional composition, and breast emptying in order to assist in making a choice for health care personnel and mothers in SCN settings. Duration of expression and maternal preference were also evaluated as secondary outcomes. METHODS: Mothers of preterm infants used 4 MBPs in a random order, 2 with a squeeze-handle mechanism (Isis and Harmony) and 2 with a cylindrical mechanism (Little Heart and Evenflo), both at the hospital and in home settings using each pump over one 24-hour period. RESULTS: Milk volume, nutritional composition, breast emptying, and duration of expression were not different among MBPs. Scale of maternal preference rated higher those with the squeeze-handle mechanism than the cylindrical mechanism (p < 0.05). CONCLUSIONS: There was no difference found in the effectiveness across the four pumps tested. The mothers' rating for comfort and ease of use showed a marked difference between pumps. These factors, plus cost, need to be considered when evaluating manual pumps for use in SCN settings in developing countries.

Association between carotid intima-media thickness, buccodental status, and glycemic control in pediatric type 1 diabetes.

OBJECTIVE: To evaluate the association between carotid intima-media thickness, buccodental status, and glycemic control in patients with type 1 diabetes. METHODS: Cross-sectional study with consecutive cases attended in an outpatient clinic (n = 69). Medical and clinical dental history, HbA1c, lipid profile, treatment period, and daily insulin dosage were recorded. Sociodemographic data and anthropometrical measurements were obtained by standardized questionnaire. Doppler real-time ultrasound was performed by a single experienced vascular radiologist blinded to the study. Assessment of buccodental status was done by the Maxillofacial Unit of the Pediatrics Hospital, and an oral scrape culture was collected. RESULTS: The mean age was 11.7 ± 3.0 years, with diabetes 5.1 ± 3.3 years. Mean HbA1c was 8.5 ± 1.7%. Primary teeth were present in 52.2% and bacterial plaque in 94.2%. Buccodental conditions featured caries (63.8%), gingivitis (84%), and enamel demineralization (26.1%): white spot lesions (18.8%) and cavitated lesions (7.3%). Bacteria associated with caries were found in 44.1%. Patients in the highest HbA1c tertile (>8.5%) had greater frequency of buccodental conditions and were positive for Streptococcus mutans and Candida albicans; also, cIMT increased and vessel compliance decreased compared to those in the lowest tertile (<7.0%) (p < 0.05). CONCLUSIONS: More buccodental conditions and carotid intima-media thickness increase appeared in the patients with HbA1c level > 8.5%, suggesting onset of atherosclerosis. The correlation between buccodental status and HbA1c values may indicate the connection between inflammatory states of atherosclerosis and type 1 diabetes.