The role of Staphylococcus aureus in cystic fibrosis pathogenesis and clinico-microbiological interactions.

Cystic fibrosis (CF) is a progressive and inherited disease that affects approximately 70000 individuals all over the world annually. A mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene serves as its defining feature. Bacterial infections have a significant impact on the occurrence and development of CF. In this manuscript, we discuss the role and virulence factors of Staphylococcus aureus as an important human pathogen with the ability to induce respiratory tract infections. Recent studies have reported S. aureus as the first isolated bacteria in CF patients. Methicillin-resistant Staphylococcus aureus (MRSA) pathogens are approximately resistant to all ß-lactams. CF patients are colonized by MRSA expressing various virulence factors including toxins, and Staphylococcal Cassette Chromosome mec (SCCmec) types, and have the potential for biofilm formation. Therefore, variations in clinical outcomes will be manifested. SCCmec type II has been reported in CF patients more than in other SCCmec types from different countries. The small-colony variants (SCVs) as specific morphologic subtypes of S. aureus with slow growth and unusual properties can also contribute to persistent and difficult-to-treat infections in CF patients. The pathophysiology of SCVs is complicated and not fully understood. Patients with cystic fibrosis should be aware of the intrinsic risk factors for complex S. aureus infections, including recurring infections, physiological issues, or coinfection with P. aeruginosa.

Colonization of the gut mucosa of colorectal cancer patients by pathogenic mucosa-associated Escherichia coli strains.

Some strains of Escherichia coli are known to be involved in the pathogenesis of colorectal cancer (CRC). The aim of current study was to compare the general characteristics of the E. coli from CRC patients and healthy participants. A total of 96 biopsy samples from 48 CRC patients and 48 healthy participants, were studied. The clonality of the E. coli isolates was analyzed by Enterobacterial repetitive intergenic consensus-based PCR (ERIC-PCR) method. The strains were tested by PCR to determine the prevalence of different virulence factors. According to the results of ERIC-PCR analysis, (from the 860 E. coli isolates) 60 strains from CRC patients and 41 strains from healthy controls were identified. Interestingly, the majority of the strains of both groups were in the same cluster. Enteropathogenic E. coli (EPEC) was detected significantly more often in CRC patients (21.6 %) than in healthy participants (2.4 %) (p < 0.05). The Enteroaggregative E. coli (EAEC) was found in 18.33 % of the strains of CRC patients. However, other pathotypes were not found in the E. coli strains of both groups. Furthermore, all the studied genes encoding for virulence factors seemed to be more prevalent in the strains belonging to CRC patients. Among the virulence genes, the statistical difference regarding the frequency of fuyA, chuA, vat, papC, hlyA and cnf1 genes was found significant (p < 0.05). In conclusion, E. coli strains that carry extraintestinal pathogenic E. coli (ExPEC) and diarrheagenic E. coli (DEC) multiple virulence factors colonize the gut mucosa of CRC patients.

Detection of NDM-1 producing Klebsiella pneumoniae ST15 and ST147 in Iran during 2019-2020.

Carbapenems are employed to treat infections caused by Gram-negative bacteria including Klebsiella pneumoniae. This research is aimed to perform phenotypic detection of ß-lactamases and molecular characterization of NDM-1 positive K. pneumoniae isolates. Another objective is to investigate NDM-1 producing K. pneumoniae among children in Iran. From 2019 to 2020, altogether 60 K. pneumoniae isolates were acquired from various patients in certain Iranian hospitals. Antimicrobial susceptibility testing was performed by disk diffusion and broth microdilution methods. In addition, mCIM and eCIM were used to confirm the production of carbapenemases and metallo-beta-lactamases (MBLs), respectively. Detection of resistance genes namely, blaNDM-1, blaIMP, blaVIM, blaKPC, blaOXA-48-like, blaCTX-M, blaSHV, blaTEM, and mcr-1 was performed by PCR and confirmed by DNA sequencing. Multilocus sequence typing (MLST) was employed to determine the molecular typing of the strains. According to the findings, the highest rate of carbapenem resistance was detected against doripenem 83.3% (50). Moreover, 31.7% (19) were resistant to colistin. Further to the above, altogether 80% (48) were carbapenemase-producing isolates and among them 46.7% (28) of the isolates were MBL and 33.3% (20) isolates were serine ß-lactamase producer. According to the PCR results, 14 isolates produced blaNDM-1. Remarkably, four blaNDM-1 positive isolates were detected in children. In addition, these isolates were clonally related as determined by MLST (ST147, ST15). Altogether ten blaNDM-1 positive isolates were ST147 and four blaNDM-1 positive isolates were ST15. Based on the results, the emergence of NDM-producing K. pneumoniae among children is worrying and hence, it is necessary to develop a comprehensive program to control antibiotic resistance in the country.

Comparison of superantigens and attachment factors genes of Staphylococcus aureus in clinical isolates and nasal colonizers in the same patients.

BACKGROUND: Staphylococcus aureus (S. aureus) is a bacterial pathogen can cause a wide range of nosocomial infections. Nasal colonization by S.aureus plays important role both in the epidemiology and pathogenesis of infection. OBJECTIVES: The purpose of this study was to investigate the association of clinical isolates and nasal colonizers of S. aureus in the same patients by molecular methods, and their antibiotic susceptibility pattern. METHODS: A total of 181 S. aureus isolates were collected from 100 patients admitted that including 100 clinical isolates and 81 nasal swabs from the same patients (19 cases were found as noncarriers). Superantigens and adhesion genes were identified by PCR. Molecular typing of the isolates was performed by repetitive element polymerase chain reaction (Rep-PCR). Antimicrobial susceptibility pattern of the isolates was conducted by disk diffusion. MIC of the isolates to vancomycin was determined by microbroth dilution. The ability of S. aureus isolates to form biofilm was determined by microtiter plate assay. RESULTS: The most frequent adhesion gene in both clinical isolates and nasal colonizer was clfA with 93% and 76%, respectively. Staphylococcal enterotoxin A (SEA) was the most commonly superantigen (68%) in both nasal colonizers (71.6%) and clinical isolates (65%). The highest resistance rate was to erythromycin (45.3%) with 36% and 56.8% in clinical and nasal colonizer isolates, respectively. All S. aureus isolates were susceptible to linezolid and vancomycin. Multiple drug resistance (MDR) was detected in 36% (n = 65) of the isolates. Biofilm formation was identified in 160 (88.4%) isolates with 87% and 90% in clinical isolates and nasal colonizers, respectively. Repetitive element polymerase chain reaction (Rep-PCR) typing divided 181 S. aureus isolates into six clusters. Twelve isolates from clinical isolates and nasal carriers were closely related. CONCLUSION: There is a high concordance rate between colonizing and clinical isolates of S. aureus in terms of adhesion factors and superantigen genes. It is suggested that nasal decolonization could be effective in the preventing of S. aureus infections.