Carbapenem resistance expressed by Gram-negative bacilli isolated from a cohort of Libyan patients

Background and objectives: Carbapenem-resistant Enterobacteriaceae (CRE) and other Gram-negative bacteria are among the most common pathogens responsible for both community and hospital acquired infection. The global spread of cephalosporinases in Enterobacteriaceae has led to the increased use of carbapenems resulting in the emergence and rapid spread of CRE. This has become an alarming public health concern, yet the condition in Libya remains unclear. The aim of this study was to obtain a better understanding of CRE strains prevalent in Libyan patients by investigating their phenotypic characteristics and antibiograms. Methods: Gram-negative bacterial species were collected from Misrata Central Hospital, Misrata Cancer Centre and Privet Pathology Laboratories. Clinical samples and swabs were obtained from hospitalised and non-hospitalised patients and from mechanical ventilation and suction machines. Patients who had received antibiotic therapy for at least three days prior to the study were excluded. The identification and characterization of the isolated species were achieved using the growth characteristics on MacConkey and blood agar, spot tests and API 20E or API 20NE biochemical testing systems. Screening for carbapenem resistance was performed using the disk diffusion method with carbapenem 10 μg and cephalosporin 30 μg disks and minimum inhibitory concentrations (MIC) determined using the Sensititre Gram-negative Xtra plate format (GNX2F). All strains demonstrating resistance or reduced susceptibility to one of the four carbapenems were subjected to carbapenememase activity detection using the RAPIDEC CARBA NP test, Modified Hodge test and carbapenem inactivation methods. Results: A total of one hundred and forty isolates representing fourteen bacterial species were isolated from 140 non-duplicated specimens. Clinical specimens included urine samples (96/140, 68.57%), sputum (15/140, 10.71%), surgical wound swabs (18/140, 12.85%), foot swabs from diabetes mellitus (DM) patients (6/140, 4.29%), ear swabs (3/140, 2.14%) and wound swabs (2/140, 1.43%). Thirty-four (24.29%) isolates demonstrated resistance to at least one of the four carbapenems with Klebsiella pneumoniae representing 73.53% (25 isolates) of all carbapenem resistant species, followed by 8.82% for Pseudomonas aeruginosa (3 isolates), 5.88% for both Proteus mirabilis (2 isolates) and Escherichia coli (2 isolates) and 2.94% for both Citrobacter koseri (1 isolate) and Rahnella aquatilis (1 isolate). The other isolates were either susceptible or cephalosporinase producers. Conclusion: This study has revealed the high rate of carbapenem resistance amongst Libyan patients and emphasizes the crucial need for accurate screening, identification and susceptibility testing to prevent further spread of nosocomial and community acquired resistance. This may be achieved through the establishment of antibiotic stewardship programmes along with firm infection control practices.National Research Foundation of South Africa; Libyan GovernmentWeb of Scienc

Development of a cost-effective drug sensitivity test for multi-drug resistant and extensively drug-resistant tuberculosis

Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2010The World Health Organisation estimates that nine million people are infected with tuberculosis (TB) every year of which ninety-five percent live in developing countries. Africa has one of the highest incidences of TB in the world. but few of its countries are equipped to diagnose drug-resistant TB. This study aimed to develop a robust. yet simple and cost-effective assay. which would require minimal sophisticated instrumentation and specialised personnel that would make drug sensitivity screening for multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) accessible to resource-poor high-burden settings. A four-quadrant colorimetric agar plate method was developed which showed good specificity (97.3%-100%) and sensitivity (77.8%-100%) compared to the polymerase chain reaction (PCR) method used as gold standard. Agreement between the methods. using Simple Kappa Coefficients. ranged between very good and excellent. all with high statistical significance (P < 0.0001). The currently used BACTEC MGIT SIREN sensitivity assay coupled with the E-test® strip method. as routinely used in the TB reference laboratory. was compared and showed excellent comparison with the newlydeveloped plate method. for each antibiotic tested. as well as the resultant monoresistant, MDR- or XDR-TB diagnoses. Moreover. the new method was found to be extremely cost-effective. priced at half the cost of a peR assay. These four quadrant plates. with a colorimetric indicator and selected antibiotics. can be considered as an economic altemative or a complimentary method for laboratories wishing to reduce the cost and complexity for TB drug sensitivity testing. Routine diagnostic testing would thus be made more accessible and affordable to laboratories that are not presently diagnosing drug resistant TB. therefore enhancing case detection and treatment in the resource-poor settings hardest hit by this curable disease