In this study, the correlation between the antibiotic resistance genes and antibiotic susceptibility among the carbapenem-resistant Gram-negative pathogens (CRGNPs) recovered from patients diagnosed with acute pneumonia in Egypt was found. A total of 194 isolates including Klebsiella pneumoniae (89; 46%), Escherichia coli (47; 24%) and Pseudomonas aeruginosa (58; 30%) were recovered. Of these, 34 (18%) isolates were multiple drug resistant (MDR) and carbapenem resistant. For the K. pneumoniae MDR isolates (n = 22), bla_NDM (14; 64%) was the most prevalent carbapenemase, followed by bla_OXA-48 (11; 50%) and bla_VIM (4; 18%). A significant association (p value < 0.05) was observed between the multidrug efflux pump (AcrA) and resistance to β-lactams and the aminoglycoside acetyl transferase gene (aac-6’-Ib) gene and resistance to ciprofloxacin, azithromycin and β-lactams (except for aztreonam). For P. aeruginosa, a significant association was noticed between the presence of the bla_SHV gene and the multidrug efflux pump (MexA) and resistance to fluoroquinolones, amikacin, tobramycin, co-trimoxazole and β-lactams and between the aac-6’-Ib gene and resistance to aminoglycosides. All P. aeruginosa isolates (100%) harbored the MexAB-OprM multidrug efflux pump while 86% of the K. pneumoniae isolates harbored the AcrAB-TolC pump. Our results are of great medical importance for the guidance of healthcare practitioners for effective antibiotic prescription.

Macrolide-resistant methicillin-resistant Staphylococcus aureus (MAC-MRSA) is one of the most clinically relevant pathogens due to its significant ability of resistance acquisition to different antimicrobial agents. This study aimed to evaluate antimicrobial susceptibility and the use of different combinations of azithromycin with other antibiotics for combating MAC resistance. Seventy-two Staphylococci (38.5%) (n = 187), showed resistance to MACs; of these, 53 isolates (73.6%, n = 72) were S. aureus and 19 (26.4%, n = 72) were coagulase-negative staphylococci (CoNS). Out of the 53 S. aureus and 19 CoNS isolates, 38 (71.7%, n = 53) and 9 (47.4%, n = 19) were MRSA and methicillin-resistant CoNS, respectively. The constitutive MACs, lincosamides and streptogramin-B (cMLS) comprised the predominant phenotype among S. aureus isolates (54.7%) and CoNS isolates (78.9%). The PCR analysis showed that the ermC gene was the most prevalent (79.2%), followed by msrA (48.6%), and ermA (31.9%). Azithromycin combinations with either linezolid, ceftriaxone, gentamicin, or cefotaxime provided synergy in 42.1%, 44.7%, 31.6% and 7.9% of the 38 MAC-MRSA isolates, respectively. Statistical analysis showed significant association between certain MAC resistance genotypes and the synergistic effect of certain azithromycin combinations (p value < 0.05). In conclusion, azithromycin combinations with either linezolid, or ceftriaxone showed synergism in most of the MAC-resistant MRSA clinical isolates.

Antimicrobial resistance pattern of some bacterial pathogens involved in lower respiratory tract infections in Egypt

Resistance of Staphylococcus (S.) aureus to the currently used antimicrobials has risen dramatically in the past years creating a medical challenge as therapeutic options became very limited. This study aimed to screen and detect the prevalence of some antimicrobial-resistant genes of S. aureus clinical isolates recovered from patients suffering lower respiratory tract infections (LRTI) in Egypt. A total of 231 bacterial isolates were recovered from sputum and bronchoalveolar lavage specimens obtained from patients with LRTI. Thirty-seven isolates (16%) were identified as S. aureus where seventeen isolates (46%) showed resistance to ten or more antimicrobials. The antimicrobial susceptibility testing revealed that all the tested isolates were sensitive to vancomycin and linezolid (0%), however, the lowest resistance was observed to doxycycline (3%), and the highest resistance was observed to ciprofloxacin (51%). Sixteen isolates (43%) were found resistant to cefoxitin and harbored the mecA gene (100%). However, the mepA gene was detected in only 12 isolates (75%). Extended-spectrum β-lactamase (ESBL) including, ctx-m, shv and tem and the aac(6’)-Ib genes, were detected in 10 (62%) and 8 (50%) isolates, respectively. None of the carbapenem-resistant genes including kpc, imp, vim, ndm, and oxa, were detected in any isolate. Multiple drug resistance (MDR) is a major health concern limiting the use of common antimicrobials in therapy. Thus, new national guidelines, as well as infection control strategies including antibiotic stewardship, must be implemented in the Egyptian hospitals to limit further spread of antimicrobial resistance.