Community-acquired methicillin-resistant Staphylococcus aureus invasive infections: a case series from Central-South Chile.

The emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections at the end of the 20th century represents a significant shift in the epidemiology of staphylococcal infections and, consequently, their clinical management. There are diverse CA-MRSA clones that are widely spread worldwide, showing differences in their regional dissemination, which has been dynamically changing over time. Although the first CA-MRSA description occurred about 30 years ago, its epidemiology in certain regions, such as South America, has been poorly explored, resulting in a gap in the understanding of the epidemiology of CA-MRSA in under-represented countries/regions. This report describes the first four clinical cases of invasive infections caused by CA-MRSA in a tertiary hospital in the central-southern region of Chile. It also associates the clinical characteristics of the infections with the microbiological and molecular features of the isolates. The four S. aureus isolates belong to sequence type 8, which has been widely described as a cause of community-acquired infections. All of them presented a wide resistome and virulome. Additionally, in two of them, it was possible to reconstruct the COMER genetic element, present in the USA300-Latin American variant clone. Considering these findings, it is crucial to prepare for a potential increase in invasive CA-MRSA infections in Chile. This would involve enhancing current surveillance systems and maintaining a low threshold of suspicion for these infections among clinicians.

[The pneumococcal connection]. / La conexión neumocóccica.

The resistance of gram-negative bacilli is one of the most important areas in modern medicine, however it hasn't been highlighted the role of the third generation cephalosporins and in particularly ceftriaxone in the selection of gram-negative bacilli resistant to these agents. Paradoxically, ceftriaxone, like the rest of the molecules of this generation, whose initial indication were gram- negative infections began to be used as an agent of choice in pneumococcal infections. The broad spectrum activity of this molecule with its favorable pharmacokinetic properties replaces other agents by this antibiotic in the treatment of a wide range of community acquired infections. However, it wasn't considered the action of this cephalosporin on the microbiome, particularly the intestinal flora, which allowed the selection of enterobacteria that by genetic events, especially parental ß-lactamases mutations (TEM-1, TEM-2, SHV-1), developed resistance to third-generation cephalosporins. The decreased susceptibility to penicillin in Streptococcus pneumoniae isolates that stimulated the growing use of ceftriaxone, was one of the main drivers for the development of resistance to third-generation cephalosporins in gram-negative bacilli.

[Copper activity against multiresistant Gram negative bacilli isolated from Chilean hospitals]. / Actividad de cobre sobre bacilos gramnegativos multi-resistentes aislados en hospitales chilenos.

INTRODUCTION: Multiresistant nosocomial pathogens, especially Gram-negative bacilli (GNB), are a serious problem for public health systems worldwide. Due to their antimicrobial properties, copper alloys have been suggested as an alternative for the control of bacterial burden in surfaces in hospital environment. However, antibiotic multiresistance and copper resistance could be associated in GNB, and there is evidence that both kind of resistance genes (antibiotic and copper) can be located on the same genetic structures. For this reason antibiotic-multiresistant strains could survive in the presence of copper, selecting for bacterial phenotypes resistant to both antibacterial agents. AIM: To evaluate antibacterial activity of copper against nosocomial extended-spectrum ß-lactamases (ESBL) (+) and ESBL (-) GNB, and carbapenems resistant or susceptible strains. MATERIAL AND METHOD: This study included 390 strains of GNB isolated from Chilean hospitals: Acinetobacter baumannii and Pseudomonas aeruginosa resistant (CAR R) and susceptible (CAR S) to carbapenem antibiotics, and Klebsiella pneumoniae and Escherichia coli producers and non-producers of ESBL. Susceptibility levels to cupric sulphate were determined by agar dilution method and statistical analysis were used to determine the significance of the differences in the copper tolerance levels between the strains groups. RESULTS: Statistically superior copper tolerance levels were found in the CAR R and ESBL producing strains of A. baumannii and K. pneumoniae, in relation with the CAR S and ESBL not-producing strains. CONCLUSION: A relation between a diminished susceptibility to ionic copper and to recent generation antimicrobial agents was observed in K. pneumoniae y A. baumannii strains.

[Evolution of use of antibiotics of restricted prescription and trend of bacterial susceptibility in Concepcion Regional Hospital, Chile]. / Evolución del consumo de antimicrobianos de uso restringido y tendencia de la susceptibilidad in vitro en el Hospital Regional de Concepción, Chile.

The aim of this study was analyze the use of restricted antibiotics by patients hospitalized between 2004 and 2008 in Guillermo Grant Benavente Hospital in Concepcion. Also we attempted to identify possible correlations between antibiotic consumption and patterns of bacterial susceptibility. We performed a retrospective observational study that quantified the use of restricted antibiotics using DDD/100-bed-days, and cumulative susceptibility reports informed by the hospital's microbiology laboratory for bacterial susceptibility. The consumption of restricted antibiotics significantly increased between 2004 and 2008 (35%, p = 0.005). The groups with largest use were glycopeptides (37%) and carbapenems (30 %). These results can be explained by the emergence of endemic Methicillin-resistant Staphylococcus aureus (MRSA) and of Extended-spectrum beta-lactamase (ESBL) Gram negative bacilli. Results showed a decrease in susceptibility of P. aeruginosa to imipenem (p = 0.038) and K. pneumoniae to ciprofloxacin (p = 0.021). The total consumption of restricted antibiotic has significantly increased, especially among complex medical services. A significant decrease in bacterial susceptibility has been observed mainly in gram-negative bacilli. The monitoring of antimicrobial prescribing practices and local susceptibility patterns are essential to promote the rational use of antibiotics.

[Multi-drug efflux pumps and antibiotic resistance in Acinetobacter baumannii]. / Bombas de expulsión multidrogas en Acinetobacter baumannii y resistencia a antimicrobianos.

Bacterial multi-drugs systems contribute to the development of multi-resistance patterns of Acinetobacter baumannii, a nosocomial pathogen of increasing importance due to its emerging resistance to carbapenems. The multi-resistance phenomena is generated by a combination of mechanisms, one of which the efflux pump system. Many of these multiresistant isolates of A. baumannii harbor genes for the AdeABC multi-drug efflux system, related with resistance to various groups of antibacterial agents, including tygecicline and meropenem. Inhibition of these systems would allow to increase the efficacy of this antimicrobial. This review focuses on the multi-drug efflux pump system of A. baumannii with special emphasis in the AdeABC system.

[Molecular basis of methicillin-resistance in Staphylococcus aureus]. / Bases moleculares de la resistencia a meticilina en Staphylococcus aureus.

Staphylococcus aureus isolates resistant to several antimicrobials have been gradually emerged since the beginning of the antibiotic era. Consequently, the first isolation of methicillin-resistant S. aureus occurred in 1960, which was described a few years later in Chile. Currently, S. aureus resistant to antistaphylococcal penicillins is endemic in Chilean hospitals and worldwide, being responsible for a high burden of morbidity and mortality. This resistance is mediated by the expression of a new transpeptidase, named PBP2a or PBP2', which possesses lower affinity for the ß-lactam antibiotics, allowing the synthesis of peptidoglycan even in presence of these antimicrobial agents. This new enzyme is encoded by the mecA gene, itself embedded in a chromosomal cassette displaying a genomic island structure, of which there are several types and subtypes. Methicillin resistance is mainly regulated by an induction mechanism activated in the presence of ß-lactams, through a membrane receptor and a repressor of the gene expression. Although mec-independent methicillin resistance mechanisms have been described, they are clearly infrequent.

[Monoarticular tuberculosis of the wrist: a case report]. / Tuberculosis monoarticular de la muñeca. Comunicación de un caso.

Monoarticular tuberculosis of the wrist is a rare presentation of primary tuberculosis, being more common skeletal forms involving the spine. Extraspinal tuberculous osteomyelitis is rare and comprises only 2 to 3% of all cases of osteoarticular Mycobacterium tuberculosis infections. We present a case of a 49 years old female patient, who worked as an hospital cleaning employed without other comorbidity. After a low energy injury of the wrist she suffered pain syndrome diagnosticated as a flexor tendinopathy, managed with nonsteroidal antiinflammatory drugs and physical therapy. Eight months later patient evolves with chronic pain in range of motion of right wrist joint, leading to a complete radiological, surgical biopsy and cultures. Histology, and molecular biology confirmed the wrist joint tuberculosis diagnosis. Pharmacological treatment and physical therapy were initiated with appropriated response.

[Colistin in the post-antibiotic era]. / Colistín en la era post-antibiótica.

One of the most important features of the post-antibiotic era in the late 20th century is the resurgence of colistin for the treatment of extensively drug resistant gram-negative bacteria (XDR). Colistin is a narrow spectrum anti-biotic, active against microorganisms with clinical significance such as Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae. Nowadays its toxicity is lower, partly explained by better pharmaceuticals and management of the critically ill patients. However, there has been much confusion regarding the dosage of the drug, its name and labeling, therefore, experts have recommended using a common language about this polymyxin. The lack of PK/PD studies for colistin is perhaps the main weakness of this area of knowledge, even though the before mentioned approach has contributed with new ways to manage and calculate the dose of this antimicrobial. Indeed, the efficiency of colistin in association with a second agent in reducing mortality has not been demonstrated.

[Isolation of Staphylococcus aureus hetero-resistant to vancomycin (hVISA) in the Regional Hospital of Concepción, Chile]. / Aislamiento de Staphylococcus aureus hetero-resistente a vancomicina en Hospital Clínico Regional de Concepción, Chile.

Methicillin-resistant Staphylococcus aureus (MRSA) is widely distributed in hospital environments, causing serious infections, mainly the bloodstream, surgical site infection and pneumonia. Vancomycin (VAN) is the antibiotic of choice for treating severe MRSA infections; however, nowadays worldwide resistant strains (VRSA), with intermediate susceptibility (VISA) and decreased susceptibility or hetero-resistance to VAN (hVISA) have been reported, related to treatment failure and increased mortality. This report describes the first confirmed isolation of MRSA with hVISA phenotype in a public hospital in Chile.