Prevalence of MDR pathogens of bacterial meningitis in Egypt and new synergistic antibiotic combinations

Abstract

The aim of this study was identifying bacterial pathogens involved in meningitis, studying their antibiotic resistance profiles, investigating the antibiotic resistance genes as well as evaluating the use of various antibiotic combinations. Antibiotic susceptibility tests were evaluated according to CLSI guidelines. Antibiotic combinations were evaluated by calculating the Fractional Inhibitory Concentration (FIC) index. A total of 71 bacterial isolates were recovered from 68 culture positive CSF specimens. Sixty five of these isolates (91.5%) were recovered from single infection specimens, while 6 isolates (8.4%) were recovered from mixed infection specimens. Out of the 71 recovered isolates, 48 (67.6%) were Gram-positive, and 23 (32.4%) were Gram-negative. Thirty one of the Gram positive isolates were S. pneumoniae (64.6%, n = 48). Out of the recovered 71 isolates; 26 (36.6%) were multidrug-resistant (MDR) isolates of which, 18 (69.2%) were Gram-negative and 8 (30.8%) were Gram-positive. All MDR isolates (100%) showed resistance to penicillin and ampicillin, however, they showed lower resistance to meropenem (50%), levofloxacin (50%), amikacin (48%), pipercillin-tazobactam (45.8%). Most common antibiotic resistance genes were investigated including: tem (21.1%), shv (15.8%), ctx-m (15.8%) coding for TEM-, SHV, CTX-M extended-spectrum beta-lactamases (ESBLs), respectively; aac(6')-I b(26.3%) coding for aminoglycoside 6'-N-acetyltransferase type Ib ciprofloxacin resistant variant; and qnrA (5.3%) gene coding for quinolone resistance. The DNA sequences of the respective resistance genes of some selected isolates were PCR amplified, analyzed and submitted to the GenBank database under the accession numbers, KX214665, KX214664, KX214663, KX214662, respectively. The FIC values for ampicillin/sulbactam plus cefepime showed either additive or synergistic effect against ten tested Gram-negative MDR isolates, while doxycycline plus levofloxacin combination revealed synergism against two MDR Gram-positive isolates. The results indicate high prevalence of antibiotic resistance among MDR isolates. Therefore, new guidelines should be implemented in Egypt to rationalize the use and avoid the misuse and abuse of antimicrobial agents.

Fig 1. Relative percentage of various CSF specimens collected during the study period (n = 1337).

Out of the 68 culture positive specimens, 71 bacterial isolates were recovered from cerebrospinal fluid (CSF); 65 isolates (91.5%) were from specimens with single bacterial species, 6 isolates (8.4%) were from mixed culture. Specimens collected from males were 44(64.7%), while only 24 specimens were collected from females (35.3%). Regarding age, 5 specimens (7.35%) were from infants (age from 1–12 Months), 10 specimens (14.7%) were from children (>1–16 Years) and the rest of the specimens (77.9%) were from adults (>16Years). Using Gram-stain, 48 isolates (67.6%) were found to be Gram-positive and 23 isolates (32.4%) were found to be Gram-negative. The prevalence of different clinical bacterial isolates cultured from the 68 CSF specimens is delineated in Fig 2.

Fig 2. Prevalence of different clinical bacterial isolates cultured from the 68 CSF specimens.

Prevalence was expressed as percentage from total count (n = 71).

Fig 3. Prevalence of the antimicrobial resistance of the 26 tested MDR isolates to different antimicrobial agents.

Prevalence was expressed as percent of resistant isolates relative to total tested isolates for each antimicrobial agent (n, 26).

Fig 4. Prevalence of some selected antibiotic resistance genes among MDR bacterial pathogens.