Rapid screening of pyogenic Staphylococcus aureus for confirmation of genus and species, methicillin resistance and virulence factors by using two novel multiplex PCR

Prevalence of bacteremia and antimicrobial resistance pattern among patients in South Lebanon

BACKGROUND

Bacteremia is a leading cause of morbidity and mortality worldwide. Rising prevalence and antimicrobial resistance (AMR) are critical public health issues. This study aims to determine the prevalence of bacteremia and the AMR pattern among patients in South Lebanon.

METHODS

A cross-sectional study analyzed 76 positive blood cultures from Hammoud and Labib Hospitals in South Lebanon between September 2023 and March 2024. The phenotype and antimicrobial susceptibility of gram-positive and gram-negative were determined by using disk diffusion. Genotypically, polymerase chain reaction was used to detect the carbapenemase-resistant Enterobacterales (CRE), extended-spectrum β-lactamases (ESBL), and methicillin-resistant Staphylococcus aureus genes.

RESULTS

Out of 76 isolates, 38 (50%) were gram-positive and 38 (50%) were gram-negative. Escherichia coli was the most common among gram-negative (18. 42%), with 10.52% ESBL and 3.94% CRE. Staphylococcus coagulase negative was the most common among gram-positive (40.78%), followed by Staphylococcus aureus (6.57%), with 3.94% methicillin-resistant S. aureus. The prevalent ESBL gene was CTX-M (100%), and for the CRE, NDM (66.66%) was the most common gene. Regarding S. aureus, 66.66% were mecA.

DISCUSSION

The diverse bacteremia isolates and resistance genes in South Lebanon reflect global variability in incidence and resistance profiles.

CONCLUSIONS

High rates of bacteremia and AMR in South Lebanon underscore the need for effective antibiotic stewardship programs.

Molecular analysis of Panton-Valentine Leucocidin (pvl) gene among MRSA and MSSA isolates

The present study was conducted in order to determine the frequency of pvl gene among the pathogenic and healthy population isolates of Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA). For this purpose, nasal swab samples were collected from the healthy individuals (to be used as controls, all the samples were collected irrespective of the sex and age factors), the pathogenic samples were collected from different patients suffering from skin &soft tissue infections caused by S. aureus (to be used as test samples).Both of these population samples were analyzed for the presence of pvl gene. S.aureus were identified through conventional microbiological identification procedures. In the case of normal samples, 70 nasal swabs were collected and only 33 (47%) proved to be S. aureus while 20 pathogenic samples were collected and all (100%) were cleared as S. aureus. For further distribution of samples into MRSA and MSSA, antibiotic susceptibility pattern was checked by using the standard protocols of Kirby-Bauer disc diffusion method. Two antibiotic discs Oxacillin (OX: 1ug) and cefoxitin (FOX: 30ug) were used. Among healthy population, MRSA was found to be 79% (n=26) and MSSA were present as 21% (n= 7). Among pathogenic strains 100% MRSA was detected where n= 20. Detection of pvl gene among the MRSA and MSSA isolates was done by using the uniplex PCR followed by gel electrophoresis. MRSA and MSSA of normal healthy population carried 49% and 7% pvl gene respectively. While, pathogenic MRSA samples carried 46% pvl gene among them. Potentially alarming percentage of pvl gene is present among the normal healthy individuals which indicates a future threat and a major health concern.

Circadian protection against bacterial skin infection by epidermal CXCL14-mediated innate immunity

The epidermis is the outermost layer of the skin and the body's primary barrier to external pathogens; however, the early epidermal immune response remains to be mechanistically understood. We show that the chemokine CXCL14, produced by epidermal keratinocytes, exhibits robust circadian fluctuations and initiates innate immunity. Clearance of the skin pathogen Staphylococcus aureus in nocturnal mice was associated with CXCL14 expression, which was high during subjective daytime and low at night. In contrast, in marmosets, a diurnal primate, circadian CXCL14 expression was reversed. Rhythmically expressed CXCL14 binds to S. aureus DNA and induces inflammatory cytokine production by activating Toll-like receptor (TLR)9-dependent innate pathways in dendritic cells and macrophages underneath the epidermis. CXCL14 also promoted phagocytosis by macrophages in a TLR9-independent manner. These data indicate that circadian production of the epidermal chemokine CXCL14 rhythmically suppresses skin bacterial proliferation in mammals by activating the innate immune system.