16S rRNA Gene Mutations Associated with Decreased Susceptibility to Tetracycline in Mycoplasma bovis

Mycoplasma bovis isolates with decreased susceptibilities to tetracyclines are increasingly reported worldwide. The acquired molecular mechanisms associated with this phenomenon were investigated in 70 clinical isolates of M. bovis. Sequence analysis of the two 16S rRNA-encoding genes (rrs3 and rrs4 alleles) containing the primary binding pocket for tetracycline (Tet-1 site) was performed on isolates with tetracycline hydrochloride MICs of 0.125 to 16 μg/ml. Mutations at positions A965T, A967T/C (Escherichia coli numbering) of helix 31, U1199C of helix 34, and G1058A/C were identified. Decreased susceptibilities to tetracycline (MICs, ≥2 μg/ml) were associated with mutations present at two (A965 and A967) or three positions (A965, A967, and G1058) of the two rrs alleles. No tet(M), tet(O), or tet(L) determinants were found in the genome of any of the 70 M. bovis isolates. The data presented correlate (P < 0.0001) the mutations identified in the Tet-1 site of clinical isolates of M. bovis with decreased susceptibility to tetracycline.     

Wide Local Excision as an Alternative Treatment for Periampullary Carcinoma

Wide excision of periampullary carcinoma is associated with low operative morbidity and mortality, but its effect on long-term survival, compared with that of pancreaticoduodenal resection, is controversial. Five patients with periampullary carcinoma were treated with wide local excision as a definitive procedure. There was no operative death, and four patients survived for two or more years following the operation. These patients are presented and the literature is reviewed.     

Actual Colonic Perforation in Virtual Colonoscopy: Report of a Case

Computed tomography colonography, also termed virtual colonoscopy, is a new imaging method to investigate the colon, which may be a potential alternative to the conventional endoscopic colonoscopy in some cases. The high safety profile of this imaging method was considered as an additional advantage of this procedure. A case of colonic perforation in computed tomography colonography is presented, highlighting a potential risk related to this procedure. It is assumed that perforation was the result of overinflation of air into an obstructed colon caused by a lesion at the rectosigmoid junction. Thus, it is suggested that in such cases, air insufflation should be gradual, thereby minimizing the risk of perforation.     

Pyocolpos — a rare cause of neonatal sepsis

A newborn female infant presented with a lower abdominal mass and sepsis. Radiologic and ultrasonic studies established the diagnosis of pyocolpos. Surgical drainage was successfully carried out. Hydrocolpos is an uncommon anomaly resulting from imperforate hymen or atresia of the vagina. It usually presents in the first few weeks of life as an asymptomatic abdominal mass or with symptoms due to compression of adjacent structures by the enlarged vagina. Rarely, pyocolpos results from an infected hydrocolpos, usually associated with vaginal atresia rather than imperforate hymen. It may cause life-threatening sepsis; early diagnosis and prompt surgical drainage are therefore essential. The infant described demonstrates the diagnostic approach and the management of pyocolpos. Offprint requests to: O. Zamir     

Kinetics of paraquat and copper reactions with nitroxides: the effects of nitroxides on the aerobic and anoxic toxicity of paraquat

The toxicity of paraquat (PQ2+) is attributed to intracellularly formed PQ*+, O(2)*-, H(2)O(2), and secondary.OH radicals generated through Fenton-like reactions. Yet, no antidote for PQ2+ toxicity in human has been found also due to poor cell permeability of many common antioxidants that remove toxic species predominantly extracellularly. Cell-permeable nitroxides, which scavenge xenobiotic-derived deleterious radicals and detoxify redox-active metal ions, would be expected to ameliorate PQ2+ toxicity. We have studied using pulse radiolysis the kinetics of the reactions of 2,2,6,6-tetramethyl-piperidinoxyl (TPO) and 4-OH-TPO with PQ*+ and CuIIL(2) (L = 1,10-phenanthroline, 2,2'-bipyridyl) in the absence and presence of DNA. We found that the rate constant for the reaction of PQ*+ with the nitroxides is about 4 orders of magnitude lower than that with O(2). In addition, the rate of the reaction of the nitroxides with CuIL(2) decreases as [DNA] increases, which suggests that nitroxides react significantly slower with bound metal ions. These results explain the failure of 4-OH-TPO to protect bacterial and mammalian cells from PQ2+ toxicity under air. In contrast, the rate of the reaction of PQ*+ with CuIIL(2) was unaffected by DNA. Furthermore, copper toxicity has been attributed mainly to CuI and was observed predominantly for cells subjected to anoxic conditions. It implied that nitroxides would be effective protectants if PQ2+ induces toxicity also under anoxia. Surprisingly, we found that PQ2+ toxicity under anoxia was even greater than that under air, and under these conditions 4-OH-TPO protected the cells from PQ. These results indicate that the mechanism underlying the anoxic toxicity of PQ2+ differs from that operating in the presence of oxygen, and that reduced transition metal ions are most probably the species responsible for PQ2+ anoxic toxicity.     

Antibacterial properties of dermaseptin S4 derivatives with in vivo activity

Derivatives of the cytotoxic peptide dermaseptin S4 have recently emerged as potential antimicrobial agents. Here, we report on the antibacterial properties of three derivatives with improved toxicity profiles: a 28-residues K4K20-S4 and two shorter versions, K4-S4(1-16) and K4-S4(1-13). The range of MICs of K4K20-S4 against clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli were, respectively, 1 to 4, 1 to 4, and 1 to 16 microg/ml. MICs of the short derivatives were rather similar or two to fourfold higher. Each of the three peptides was rapidly bactericidal in vitro, reducing the number of viable CFU of either E. coli or S. aureus by 6 log units in 30 min or less. Compared with MSI-78 or PG-1, K4-S4(1-13) was at least as potent against bacteria (assessed at two MIC multiples) but displayed lesser toxicity against human erythrocytes. Serial passage in subinhibitory concentrations led to emergence of resistance to commercial antibiotics but not to the L- or D isomer of either of the dermaseptin derivatives. The short derivatives were further investigated for antibacterial activity in vivo, using a peritonitis model of mice infected with P. aeruginosa. Naive mice in the vehicle control group exhibited 75% mortality, compared to 18 or 36% mortality in mice that received a single intraperitoneal injection (4.5 mg/kg) of K4-S4(1-16) or K4-S4(1-13), respectively. In vivo bactericidal activity was confirmed in neutropenic mice, where intraperitoneal administration of K4-S4(1-16) reduced the number of viable CFU in a dose-dependent manner by >3 log units within 1 h of exposure, and this was sustained for at least 5 h. Overall, the data suggest that dermaseptin S4 derivatives could be useful in treatment of infections, including infections caused by multidrug-resistant bacteria.     

A chimeric peptide composed of a dermaseptin derivative and an RNA III-inhibiting peptide prevents graft-associated infections by antibiotic-resistant staphylococci

Staphylococcal bacteria are a prevalent cause of infections associated with foreign bodies and indwelling medical devices. Bacteria are capable of escaping antibiotic treatment through encapsulation into biofilms. RNA III-inhibiting peptide (RIP) is a heptapeptide that inhibits staphylococcal biofilm formation by obstructing quorum-sensing mechanisms. K(4)-S4(1-13)(a) is a 13-residue dermaseptin derivative (DD(13)) believed to kill bacteria via membrane disruption. We tested each of these peptides as well as a hybrid construct, DD(13)-RIP, for their ability to inhibit bacterial proliferation and suppress quorum sensing in vitro and for their efficacy in preventing staphylococcal infection in a rat graft infection model with methicillin-resistant Staphylococcus aureus (MRSA) or S. epidermidis (MRSE). In vitro, proliferation assays demonstrated that RIP had no inhibitory effect, while DD(13)-RIP and DD(13) were equally effective, and that the chimeric peptide but not DD(13) was slightly more effective than RIP in inhibiting RNA III synthesis, a regulatory RNA molecule important for staphylococcal pathogenesis. In vivo, the three peptides reduced graft-associated bacterial load in a dose-dependent manner, but the hybrid peptide was most potent in totally preventing staphylococcal infections at the lowest dose. In addition, each of the peptides acted synergistically with antibiotics. The data indicate that RIP and DD(13) act in synergy by attacking bacteria simultaneously by two different mechanisms. Such a chimeric peptide may be useful for coating medical devices to prevent drug-resistant staphylococcal infections.     

Impact of self-assembly properties on antibacterial activity of short acyl-lysine oligomers

We investigated both the structural and functional consequences of modifying the hydrophobic, lipopeptide-mimetic oligo-acyl-lysine (OAK) N(alpha)-hexadecanoyl-l-lysyl-l-lysyl-aminododecanoyl-l-lysyl-amide (c(16)KKc(12)K) to its unsaturated analog hexadecenoyl-KKc(12)K [c(16(omega7))KKc(12)K]. Despite similar tendencies for self-assembly in solution (critical aggregation concentrations, approximately 10 muM), the analogous OAKs displayed dissimilar antibacterial properties (e.g., bactericidal kinetics taking minutes versus hours). Diverse experimental evidence provided insight into these discrepancies: whereas c(16(omega7))KKc(12)K created wiry interconnected nanofiber networks, c(16)KKc(12)K formed both wider and stiffer fibers which displayed distinct binding properties to phospholipid membranes. Unsaturation also shifted their gel-to-liquid transition temperatures and altered their light-scattering properties, suggesting the disassembly of c(16(omega7))KKc(12)K in the presence of bacteria. Collectively, the data indicated that the higher efficiency in interfering with bacterial viability emanated from a wobbly packing imposed by a single double bond. This suggests that similar strategies might improve hydrophobic OAKs and related lipopeptide antibiotics.     

Laparoscopic colectomy for colonic polyps

Background  Benign colonic polyps not amenable to colonoscopic resection or those containing carcinoma require surgical excision. Traditionally, formal colectomy with clearance of the lymphatic basin has been performed. The aim of this study was to review our experience with the laparoscopic approach for retrieval of colonic polyps with specific emphasis on safety, feasibility, and tumor localization. Methods  Retrospective chart review of all patients who underwent laparoscopic colectomy for colonic polyps was performed. Initial colonoscopic biopsies were compared with the postoperative pathology report of the resected specimen. Results  Forty-nine patients (22 males, 27 males, mean age 66 years) underwent laparoscopic colectomy for colonic polyps. Indications for surgery were presumably benign polyps in 38 patients, and superficial carcinoma in a polyp, diagnosed by colonoscopy, in 11; twenty-three patients underwent preoperative localization procedures. In 19% of patients who did not have preoperative localization, difficulties locating the polyp were encountered during surgery, requiring intraoperative endoscopy or conversion to laparotomy. In 7 of the 38 patients with presumably benign lesion, colon cancer was diagnosed in the colectomy specimen. None of the 18 patients who had cancerous lesions had any positive lymph nodes. Conclusions  Laparoscopic surgery for the treatment of colonic polyps seems to be feasible and safe, with a low complication rate. Tumor localization is crucial for adequate resection. Although one-fifth of presumably benign polyps harbored cancer, none of these patients had positive lymph nodes. These preliminary results may question the need for radical lymph node clearance in these patients. Poster presentation at the annual meeting of the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), Dallas, TX, USA, April 26–29, 2006. Poster presentation at the annual meeting of the European Society for Endoscopic Surgeons (EAES), Berlin, Germany, September 13–16, 2006.     

Laparoscopic colectomy is associated with decreased postoperative gastrointestinal dysfunction

Background  Major abdominal surgery is associated with early postoperative gastrointestinal dysfunction, which may lead to abdominal distention and vomiting, requiring nasogastric (NGT) tube insertion. This study aimed to compare the rates of early postoperative NGT insertion after open and laparoscopic colorectal surgery. Methods  A retrospective chart review was performed for patients who underwent colorectal surgery with removal of the NGT at completion of surgery. Patients who required reinsertion of the NGT in the early postoperative course were identified. The reinsertion rate for patients who underwent laparoscopic surgery was compared with that for the open group. Results  There were 103 patients in the open group and 227 in the laparoscopic group. In the laparoscopic group, 42 patients underwent conversion to open surgery. Reinsertion of the NGT was required for 18.4% of the patients in the open group, compared with 8.6% of the patients for whom the procedure was completed laparoscopically (p = 0.02). Conversion to open surgery resulted in a reinsertion rate of 17%. Conclusion  Laparoscopic colorectal surgery is associated with decreased postoperative gastrointestinal dysfunction, resulting in a significantly lower NGT reinsertion rate. Presented as a poster at the annual meeting of the Society of American Gastrointestinal and Endoscopic Surgeons, (SAGES), Dallas, Texas, 26–29 April 2006, and at the annual meeting of the European Society for Endoscopic Surgeons (EAES), Berlin, Germany, 13–16 September 2006.