Beta Lactamases

Extended-spectrum β-lactamases (ESBLs), e.g., ESBLs of the TEM or SHV type, compromise the efficacies of expanded-spectrum cephalosporins. An SHV non-ESBL that hydrolyzes only narrow-spectrum cephalosporins can be converted into an SHV ESBL through substitutions at three amino acid positions, 179, 238, or 238–240. In order to improve detection of SHV ESBLs, a novel method, based on real-time PCR monitored with fluorescently labeled hybridization probes and followed by melting curve analysis, was developed. It is able to (i) detect bla SHV genes with high degrees of sensitivity and specificity, (ii) discriminate between bla SHV non-ESBL and bla SHV ESBL , and (iii) categorize the SHV ESBL producers into three phenotypically relevant subgroups. This method, termed the SHV melting curve mutation detection method, represents a powerful tool for epidemiological studies with SHV ESBLs. It even has the potential to be used in the diagnostic microbiology laboratory, because up to 32 clinica...

Beta-lactamases are a superfamily of enzymes which degrade the β-lactam class of antibiotics. They are produced endogenously by the bacterial cells, which when exposed to the β-lactam class of antibiotics inactivate them by cleaving the β-lactam ring. Based on the presence or absence of metallic ligand, β-lactamases have been divided into two broad functional classes. β-Lactamases are a constitutively evolving and expanding superfamily of enzymes, which could be further subdivided on the basis of presence/absence of conserved motifs. In the present study we have used the MEME/MAST suit to identify the patterns/motifs which are specific to a particular family or subfamily of β-lactamases. The family specific patterns/motifs can be also useful in recognizing and assigning newly discovered β-lactamases to one or the other family or subfamily. Cross-validation showed that the proposed method is highly sensitive and specific. We have also designed a webserver, LactFP, for this purpose.

Recently, a Typhi isolate producing CTX-M-15 extended spectrum β-lactamase (ESBL) and with decreased ciprofloxacin susceptibility was isolated in the Democratic Republic of the Congo. We have selected bacteriophages that show strong lytic activity against this isolate and have potential for phage-based treatment of . Typhi, and in general.

Background: Multidrug-resistant strains of Acinetobacter baumannii have been reported increasingly around the world. The administration of an association of antibiotics has been proposed to create an active combination and to prevent the emergence of resistance. Methodology: The activity of colistin, rifampicin, gentamicin, imipenem and their associations was evaluated by means of killing curves in fourteen isolates belonging to three endemic PFGE types, in a university hospital of Buenos Aires city. The 14 isolates were selected on the basis of different mechanisms responsible for resistance to carbapenems and different susceptibility to colistin. Results: The mechanism responsible for the resistance to imipenem was the production of OXA-23 and OXA-58 carbapenemases. Heteroresistance to colistin was observed in six isolates. The associations colistin-rifampicin and colistin-imipenem were synergistic in heteroresistant isolates and prevented the development of colistin-resistant mut...

Metallo-β-lactamase gene blaVIM was identified on the chromosome of four Pseudomonas spp. isolates from a chicken farm, including one P. aeruginosa from swallow (Yanornis martini), one P. putida from fly, and two P. putida from chickens. The four isolates shared two variants of blaVIM-carrying genomic contexts, which resemble the corresponding regions of clinical MBL-producing Pseudomonas species. Our study suggests the surveillance of carbapenemase-producing bacteria in livestock and their surrounding environment is urgently needed.

There has been little investigation of bacteria as gene delivery vectors. Here, we demonstrate that genetically engineered Salmonella have many of the desirable properties of a delivery vector, including targeting of multiple tumors from a distant inoculation site, selective replication within tumors, tumor retardation, and the ability to express effector genes, such as the herpes simplex virus thymidine kinase (HSV TK). When wild-type Salmonella were introduced into melanoma-bearing mice, the bacteria were found within the tumor at levels exceeding 10(9) per g, although as pathogens, they caused the death of the mice. However, when attenuated, hyperinvasive auxotrophic mutants were used, the tumor-targeting and amplification phenomena were retained, whereas their pathogenicity was limited. With such attenuated strains, the tumor:liver ratios ranged between 250:1 and 9000:1. When these auxotrophs were inoculated i.p. into C57B6 mice bearing B16F10 melanomas, they suppressed tumor gr...

High dispersion and maintenance of complex class 1 integrons along the time.blaCTX-M-2 and qnrB10 genes were always located in complex class 1 integrons.Complex class 1 integrons with blaCTX-M-2 began to spread from Argentina in the 80’s.Complex class 1 integrons with qnrB10 began to spread from Argentina in the 90’s.The Orf513 protein binds to the previously proposed oriIS of the ISCR1.The emergence of extended-spectrum β-lactamases and plasmid-mediated resistance to quinolones has been previously found to be associated with the dissemination of complex class 1 integrons in Argentina. In this study, we analyzed their distribution through time and evaluated the functionality of the Orf513 protein, which is the putative recombinase of the ISCR1 mobile element. We investigated the presence of the orf513, blaCTX-M-2, dfrA3b, qnrB10 and blaDHA-1 genes by PCR and DNA sequencing as well as their linkage to class 1 integrons in 451 non-epidemiologically related nosocomial strains resistant to at least one expanded-spectrum cephalosporin and to one aminoglycoside, isolated between 1989 and 2010 from 7 hospitals from Buenos Aires City. The epidemiology of complex class 1 integrons was found to be notably different among fermenting (94/171) and non-fermenting clinical bacilli isolates (1/280). The ISCR1::qnrB10 positive isolates were found since 1993, confirming its presence in clinical isolates more than a decade before its first description. As expected, In35::ISCR1::blaCTX-M-2 was the most common complex class 1 integron among Enterobacteriaceae isolates, particularly in Proteus mirabilis. Experimental analysis corroborated the activity of the Orf513 protein, which was found to bind specific DNA sequences containing the previously suggested oriIS region. These findings showed the high dispersion and maintenance of complex class 1 integrons across time in our nosocomial isolates. The contribution of the ISCR1 mobile element to multidrug resistant phenotypes is significant due to its sustained association to class 1 integrons.

Acute respiratory infections accounts for 20–40% of outpatient and 12–35% of inpatient attendance in a general hospital. Upper respiratory tract infections including nasopharyngitis, pharyngitis, tonsillitis and otitis media constitute 87.5% of the total episodes of respiratory infections. The vast majority of acute upper respiratory tract infections are caused by viruses. Common cold is caused by viruses in most circumstances and does not require antimicrobial agent unless it is complicated by acute otitis media with effusion, tonsillitis, sinusitis, and lower respiratory tract infection. Sinusitis is commonly associated with common cold. Most instances of rhinosinusitis are viral and therefore, resolve spontaneously without antimicrobial therapy. The most common bacterial agents causing sinusitis areS. pneumoniae, H. influenzae, M. catarrhalis,S. aureus andS. pyogenes. Amoxycillin is antibacterial of choice. The alternative drugs are cefaclor or cephalexin. The latter becomes first line if sinusitis is recurrent or chronic. Acute pharyngitis is commonly caused by viruses and does not need antibiotics. About 15% of the episodes may be due to Group A beta hemolytic streptococcus (GABS). Early initiation of antibiotics in pharyngitis due to GABS can prevent complications such as acute rheumatic fever. The drug of choice is penicillin for 10–14 days. The alternative medications include oral cephalosporins (cefaclor, cephalexin), amoxicillin or macrolides.

Pseudomonas mendocina carrying a novel class 1 integron containing an IMP-8 gene was isolated from an inanimate surface in a female ward sanitary facility of the Hospital Infante D. Pedro, Aveiro, Portugal. Hybridization with the integrase gene (intI1) and 16S rDNA revealed that the integron is chromosomally located. Here we report for the first time the presence of an IMP-8 metallo-beta-lactamase gene in the Pseudomonas genus.

To review the available evidence regarding the utility of the currently available β-lactam/β-lactamase inhibitor combinations (BLICs) as well as the emerging body of data for the novel agents in the pipeline. A MEDLINE literature search (1960-August 2014) was performed using the search terms β-lactamase, β-lactamase inhibitor, clavulanate, sulbactam, tazobactam, avibactam, NXL104, MK-7655, and RPX7009. Current studies focusing on new agents were obtained from clinicaltrials.gov. Additional references were identified from a review of literature citations and meeting abstracts. All English-language studies pertaining to BLICs were evaluated. Historical clinical and in vitro data focusing on the characteristics of the conventional BLICs are reviewed. Avibactam, relebactam (formerly MK-7655), and RPX7009 are new β-lactamase inhibitors that are being studied in combination with β-lactams. Clinical and in vitro data that provide support for their use for multidrug-resistant organisms are ...