A novel pneumococcal surface protein K of nonencapsulated Streptococcus pneumoniae promotes transmission among littermates in an infant mouse model with influenza A virus co-infection

We established an infant mouse model for colonization and transmission by nonencapsulated Streptococcus pneumoniae (NESp) strains to gain important information about its virulence among children. Invasive pneumococcal diseases have decreased dramatically since the worldwide introduction of pneumococcal capsular polysaccharide vaccines. Increasing prevalence of non-vaccine serotypes including NESp has been highlighted as a challenge in treatment strategy, but the virulence of NESp is not well understood. Protective strategy against NESp colonization and transmission between children require particularly urgent evaluation. NESp lacks capsules, a major virulent factor of pneumococci, but can cause a variety of infections in children and older people. PspK, a specific surface protein of NESp, is a key factor in establishing nasal colonization. In our infant mouse model for colonization and transmission by NESp strains, NESp could establish stable nasal colonization at the same level as encapsulated serotype 6A in infant mice, and could be transmitted between littermates. Transmission was promoted by NESp surface virulence factor PspK and influenza virus co-infection. However, PspK-deletion mutants lost the ability to colonize and transmit to new hosts. Promotion of NESp transmission by influenza was due to increased susceptibility of the new hosts. PspK was a key factor not only in establishment of nasal colonization, but also in transmission to new hosts. PspK may be targeted as a new candidate vaccine for NESp infection in children.

Desenvolvimento de um modelo murino de colonização nasal por Staphylococcus aureus / Development of a murine model of nasal colonization by Staphylococcus aureus

O desenvolvimento de novas drogas e vacinas contra doenças humanas passa, na maioria das vezes, por ensaios prévios em modelos animais. Staphylococcus aureus é um patógeno causador de infecções graves, muitas vezes resistentes aos antimicrobianos. Grande parte da população é portadora nasal desta bactéria. O desenvolvimento de estratégias para descolonização nasal necessita de modelos animais para a realização de estudos preliminares. O presente trabalho tem por finalidade demonstrar a adaptação do protocolo de González-Zorn as condições locais do modelo de colonização nasal por S. aureus em camundongos balb/C. Neste estudo, os animais foram inoculados pela via nasal com 108 bactérias, sendo submetidos a eutanásia no terceiro e sexto dia. Observou-se uma recuperação media de 104 (19.100) e 102 (180) bactérias, nos dias 3 e 6 respectivamente. O modelo avaliado mostrou-se ideal para utilização em estudos preliminares, visando avaliar a colonização nasal por S.aureus em modelo murino.

Everybody Nose: Molecular and Clinical Characteristics of Nasal Colonization During Active Methicillin-Resistant Staphylococcus Aureus Bloodstream Infection

Background. Healthcare-associated infections pose a potentially fatal threat to patients worldwide and Staphylococcus aureus is one of the most common causes of healthcare-associated infections. S. aureus is a common commensal pathogen and a frequent cause of bacteremia, with studies demonstrating that nasal and blood isolates from single patients match more than 80% of the time. Here we report on a contemporary collection of colonizing isolates from those with methicillin-resistant S. aureus (MRSA) bloodstream infections to evaluate the diversity within hosts, and detail the clinical features associated with concomitant nasal colonization.Methods. Swabs of the bilateral anterior nares were obtained from patients diagnosed with MRSA bacteremia. A single colony culture from the blood and an average of 6 colonies from the nares were evaluated for MRSA growth. For the nares cultures, we typed multiple isolates for staphylococcal protein A (spa) and derived the clonal complexes. Demographic and clinical data were obtained retrospectively from the electronic medical record system and analysed using univariate and multivariable regression models.Results. Over an 11-month period, 68 patients were diagnosed with MRSA bloodstream infection, 53 were swabbed, and 37 (70%) were colonized with MRSA in the anterior nares. We performed molecular typing on 210 nasal colonies. Spa types and clonal complexes found in the blood were also detected in the nares in 95% of the cases. We also found that 11% of patients carried more than one clone of MRSA in the nares. Male sex and history of prior hospitalization within the past 90 days increased odds for MRSA colonization. Conclusion. The molecular epidemiological landscape of colonization in the setting of invasive disease is diverse and defining the interplay between colonization and invasive disease is critical to combating invasive MRSA disease.

Methicillin-resistant Staphylococcus aureus nasal colonization in people living with HIV and healthy people in Kathmandu, Nepal

Aim: This study aimed to compare methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization in people living with HIV (PLHIV) and healthy people from Kathmandu. Methods: MRSA isolated from 400 nasal swabs was screened using a cefoxitin disc and confirmed by the presence of the mecA gene. Results: MRSA nasal carriers among the PLHIV and control cohorts were 3.5% (7 out of 200) and 5.0% (10 out of 200), respectively. All the MRSA from PLHIV and most of MRSA from healthy controls were PVL positive. Longer duration of antiretroviral therapy significantly reduces the risk of MRSA nasal colonization in PLHIV. Conclusion: There is no significant difference in MRSA nasal colonization in PLHIV and healthy controls in this study region.

The Roles of Transient Receptor Potential Vanilloid 1 and 4 in Pneumococcal Nasal Colonization and Subsequent Development of Invasive Disease

Transient receptor potential (TRP) channels, neuronal stimulations widely known to be associated with thermal responses, pain induction, and osmoregulation, have been shown in recent studies to have underlying mechanisms associated with inflammatory responses. The role of TRP channels on inflammatory milieu during bacterial infections has been widely demonstrated. It may vary among types of channels/pathogens, however, and it is not known how TRP channels function during pneumococcal infections. Streptococcus pneumoniae can cause severe infections such as pneumonia, bacteremia, and meningitis, with systemic inflammatory responses. This study examines the role of TRP channels (TRPV1 and TRPV4) for pneumococcal nasal colonization and subsequent development of invasive pneumococcal disease in a mouse model. Both TRPV1 and TRPV4 channels were shown to be related to regulation of the development of pneumococcal diseases. In particular, the influx of neutrophils (polymorphonuclear cells) in the nasal cavity and the bactericidal activity were significantly suppressed among TRPV4 knockout mice. This may lead to severe pneumococcal pneumonia, resulting in dissemination of the bacteria to various organs and causing high mortality during influenza virus coinfection. Regulating host immune responses by TRP channels could be a novel strategy against pathogenic microorganisms causing strong local/systemic inflammation.

Methicillin-resistant Staphylococcus aureus colonization among healthcare workers in Oman

Introduction: Methicillin-Resistant Staphylococcus aureus (MRSA) is a S. aureus strain characterized by resistance to cloxacillin. Healthcare workers (HCWs), are recognized for their heightened risk for MRSA acquisition and possibly for MRSA nosocomial transmission. This cross-sectional study aimed to determine the prevalence and the associated risk factors of MRSA colonization among healthcare workers at Sultan Qaboos University Hospital (SQUH) in Oman. Methodology: A total of 200 nasal swab samples were collected from the healthcare workers at SQUH during the period October 2nd 2018 to January 7th 2019. All nasal swab samples were examined microbiologically for the presence of MRSA using the standard method and the results were confirmed by detection of the mecA product (PBP2a). Data on associated risk factors for MRSA colonization was collected and analyzed. Results: Forty-one of the 200 screened healthcare workers (20.5%) were found to have nasal carriage of Staphylococcus aureus of which 63.4% were Methicillin Sensitive and 36.6% were Methicillin-Resistant (MRSA). Methicillin-Resistant Staphylococcus aureus (MRSA) was isolated from fifteen of the 200 screened healthcare workers giving a prevalence rate of nasal colonization with MRSA of 7.5%. We found no statistical association between healthcare worker MRSA nasal colonization and age, gender, HCWs specialty, hand hygiene practices, skin condition, previous MRSA infection, and previous exposure to antibiotics. Conclusions: Identification of the prevalence and the associated risk factors of MRSA colonization in healthcare workers mandates continuous surveillance and the implementation of all possible preventive measures to reduce re-occurrences.

Long term nasopharyngeal colonization by Staphylococcus aureus determinants of adaptation

Staphylococcus aureus nasal colonization is a risk factor for infection. A large proportion of the population are identified as potential S. aureus carriers yet we only partially understand the repertoire of genetic factors that promote long-term nasal colonization. Here we present a novel murine model of nasopharyngeal colonization that requires a low S. aureus inoculum and is amenable to experimental evolution approaches. We used this model to experimentally evolve S. aureus using successive passages in the nasopharynx to identify those genetic loci under selection. After 3 cycles of colonization, mutations were identified in mannitol, sorbitol, arginine, nitrite and lactate metabolism genes promoting key pathways in nasal colonization. Stress responses were identified as being under selective pressure, with mutations in DNA repair genes including dnaJ and recF and key stress response genes clpL, rpoB and ahpF . Peptidoglycan synthesis pathway genes also revealed mutations indicating potential selection for alteration of the cell surface. The infection model used here is versatile to assist decolonization and persistence studies.

Prevalence and antimicrobial susceptibility pattern of coagulase-negative staphylococci obtained from nares of adult patients admitted to Ahmadu Bello University Teaching Hospital (ABUTH), Zaria

Coagulase-negative staphylococci (CoNS) are part of the normal microbial flora of the skin and mucous membranes. Nasal colonization with antibiotic-resistant CoNS represents both a risk factor for the colonized individual and their immediate contacts. This study determines the antibiotics susceptibility pattern and resistance phenotypes to a specific group of antimicrobial agents in CoNS isolate from the nares of adult patients from Ahmadu Bello University Teaching Hospital (ABUTH), Zaria, Kaduna State, Nigeria. One hundred and twenty-three presumptive staphylococci isolate from nasal colonization surveillance cultures of adult patients were collected from the diagnostic medical microbiology laboratory of ABUTH, Zaria and were characterized using standard microbiological procedures and their susceptibility to commonly used antimicrobial agents determined using the guideline of European committee on antimicrobial susceptibility testing (EUCAST). A total of 60 of the 123 (49%) staphylococcal isolate were CoNS. Characterization of the sixty CoNS isolate showed that the most predominant species were S. chromogenes (30.0%), S xylosus (15.0%) and S. schleiferi subsp. coagulans (13.3%). The highest level of resistance was observed to Cefoxitin (95.0%) and the lowest to Tigecycline (1.7%). S. epidermidis isolates were observed to show ≥60% resistance to all tested antibiotics with the exception of Tigecycline (0%) and Gentamicin (20%). Analysis of the multiple antibiotic resistance index (MARI) showed that majority (96.7%) of the isolates were resistant to 3 or more of the antimicrobial agents. No isolate was resistant to all the tested antimicrobial agents. A very high proportion of the CoNS isolates were resistant to cefoxitin, penicillin, tetracycline, amoxicillin-clavulanate, and vancomycin. In conclusion, the high proportion of isolates with MARI of 0.3 and above indicates a high level of antibiotic use or exposure in the study area. These findings revealed the need for continued surveillance for resistant phenotype to inform clinical therapy decisions