SummaryA literature review was undertaken to ascertain the molecular basis for tigecycline and colistin resistance mechanisms and the experimental basis for the detection and delineation of this resistance particularly in carbapenemaseproducing Gram-negative bacteria. Pubmed, Google Scholar and Science Direct were searched with the keywords colistin, tigecycline, resistance mechanisms and detection methods. Trans-complementation and comparative MIC studies, mass spectrometry, chromatography, spectrofluorometry, PCR, qRT-PCR and whole genome sequencing (WGS) were commonly used to determine tigecycline and colistin resistance mechanisms, specifically modifications in the structural and regulatory efflux (acrAB, OqxAB, kpgABC adeABC-FGH-IJK, mexAB-XY-oprJM and soxS, rarA robA, ramRAB marRABC, adeLRS, mexRZ and nfxb) and lipid A (pmrHFIJFKLM, lpxA, lpxC lpxD and mgrB, pmrAB, phoPQ,) genes respectively. Mutations in the ribosomal 16S rRNA operon rrnBC, also yielded resistance to tigecycline through target site modifications. The mcr-1 gene conferring resistance to colistin was identified via WGS, transcomplementation and a murine thigh infection model studies. Common detection methods are mainly antibiotic sensitivity testing with broth microdilution while molecular identification tools are mostly PCR and WGS. Spectrofluorometry, MALDI-TOF MS, micro-array and real-time multiplex PCR hold much promise for the future as new detection tools.

The high burden of communicable diseases in African countries engenders extensive antimicrobial use and subsequent resistance with substantial health, financial and societal implications. A desktop analysis to ascertain whether countries in the WHO African region have implemented the WHO Policy Package to combat antimicrobial resistance (AMR) revealed that just two countries (4.3%) have national AMR plans in place, 14.9% (7) have overarching national infection prevention and control (IPC) policies, 93.6% (44) have essential medicines lists and 91.5% (43) have national medicines policies and treatment guidelines intimating rational use. None currently have representative national surveillance systems nor do any incentivize research and development into new medicines and diagnostics. A regional situational analysis to identify scalable good practices within African, resource-constrained country contexts under the auspices of WHO-AFRO is a necessary initial step towards the development of national and regional action plans in concert with incremental progress towards achieving the objectives of the policy package and global action plan. While it is clearly the responsibility of governments to develop, resource and implement plans, regular reporting to and/or monitoring and evaluation by an overarching body such as WHO-AFRO will ensure persistent incremental progress within continuous quality and accountability improvement paradigms.

Whole-genome sequence analyses revealed the presence of ( = 31), ( = 8), ( = 1), or ( = 1) in extensively drug-resistant and pandrug-resistant organisms isolated from in-patients in 10 private hospitals (2012 to 2013) in Durban, South Africa. Two novel NDM-1-encoding plasmids from were circularized by PacBio sequencing. In p19-10_01 [IncFIB(K); 223.434 bp], was part of a Tn-like structure (16.276 bp) delineated by IS The multireplicon plasmid p18-43_01 [IncR_1/IncFIB(pB171)/IncFII(Yp); 212.326 bp] shared an 80-kb region with p19-10_01, not including the -containing region. The two plasmids were used as references for tracing NDM-1-encoding plasmids in the other genome assemblies. The p19-10_01 sequence was detected in ( = 7) only, whereas p18-43_01 was tracked to ( = 4), ( = 1), ( = 11), spp. ( = 7), and ( = 1), revealing horizontal spread of this -bearing plasmid structure. Global phylogeny showed clustering of the (18/20) isolates together with closely related carbapenemase-negative ST101 isolates from other geographical origins. The South African isolates were divided into three phylogenetic subbranches, where each group had distinct resistance and replicon profiles, carrying either p19-10_01, p18-10_01, or pCHE-A1 (8,201 bp). The latter plasmid carried and within an integron mobilization unit. Our findings imply independent plasmid acquisition followed by local dissemination. Additionally, we detected carried by pPKPN4 in (ST14) and contained by a pNDM-MGR194-like genetic structure in (ST167), adding even more complexity to the multilayer molecular mechanisms behind nosocomial spread of carbapenem-resistant in Durban, South Africa.

BackgroundMultidrug-resistant Gram-negative bacteria have emerged as major clinical and therapeutic dilemma in hospitals in Ghana.To describe the prevalence and profile of infections attributable to multidrug-resistant Gram-negative bacteria among patients at the Komfo Anokye Teaching Hospital in the Ashanti region of Ghana.MethodsBacterial cultures were randomly selected from the microbiology laboratory from February to August, 2015. Bacterial identification and minimum inhibitory concentrations were conducted using standard microbiological techniques and the Vitek-2 automated system. Patient information was retrieved from the hospital data.ResultsOf the 200 isolates, consisting of K. pneumoniae, A. baumannii, P. aeruginosa, Enterobacter spp., E. coli, Yersinia spp., Proteus mirabilis, Pasteurella spp., Chromobacterium violaceum, Salmomella enterica, Vibrio spp., Citrobacter koseri, Pantoea spp., Serratia spp., Providencia rettgeri Burkholderia cepacia, Aeromonas spp., Cadecea lapagei and Sphingomonas paucimobilis, 101 (50.5%) and 99 (49.5%) recovered from male and female patients respectively The largest proportion of patients were from age-group ≥60 years (24.5%) followed by < 10 years (24.0%) and least 10–19 years (9.5%) with a mean patient age of 35.95 ± 27.11 (0.2–91) years. The decreasing order of specimen source was urine 97 (48.5%), wound swabs 47 (23.5%), sputum 22 (11.0%) bronchial lavage, nasal and pleural swabs 1 (0.50%). Urinary tract infection was diagnosed in 34.5% of patients, sepsis in 14.5%, wound infections (surgical and chronic wounds) in 11.0%, pulmonary tuberculosis in 9.0% and appendicitis, bacteremia and cystitis in 0.50%. The isolates showed high resistance to ampicillin (94.4%), trimethoprim/sulfamethoxazole (84.5%), cefuroxime (79.0%) and cefotaxime (71.3%) but low resistance to ertapenem (1.5%), meropenem (3%) and amikacin (11%). The average multi-drug resistance was 89.5%, and ranged from 53.8% in Enterobacter spp. to 100.0% in Acinetobacter spp. and P. aeruginosa.ConclusionBacterial infections caused by multi-drug resistant (isolates resistant to at least one agent in three or more antibiotic classes) Gram-negative pathogens among patients at Komfo Anokye Teaching Hospital in Kumasi, Ghana are rife and interventions are necessary for their containment.

␤-Lactamase production was investigated in cultures of 25 Klebsiella pneumoniae isolates isolated at a hospital in Durban, South Africa, in 1994 and 1996. Twenty of these isolates gave ceftazidime MIC/ceftazidime plus clavulanate MIC ratios of >8, implying production of extended-spectrum ␤-lactamases (ESBLs), and DNA sequencing identified an ESBL gene (bla TEM-53 ) in a further two isolates. Pulsed-field gel electrophoresis (PFGE) defined 4 distinct strains among the 12 isolates collected in 1994 and 9 distinct strains among the 13 isolates collected in 1996. In three cases, multiple isolates from single patients varied in their PFGE profiles and antibiograms, implying mixed colonization or infection. Isoelectric focusing and DNA hybridization found both TEM and SHV enzymes and their genes in all 25 isolates. Many isolates had multiple identical or different ␤-lactamase gene variants, with at least 84 bla SHV and bla TEM gene copies among the 25 organisms. Sequencing identified the genes for the SHV-1, -2, and -5 enzymes and for four new SHV types (SHV-19, -20, -21, and -22). These new SHV variants had novel mutations remote from sites known to affect catalytic activity. Sequencing also found the genes for TEM-1, TEM-53, and one novel type, TEM-63. All the isolates had multiple and diverse plasmids. These complex and diverse patterns of ESBL production and strain epidemiology are far removed from the concept of an ESBL outbreak and suggest a situation in which ESBL production has become endemic and in which evolution is generating a wide range of enzyme combinations. This complexity and diversity complicates patient management and the design of antibiotic use policies.␤-Lactams are prescribed more often than any other antibiotics. This heavy usage has selected for resistance, which is most often caused by ␤-lactamases (17). Recent concerns have centered on extended-spectrum ␤-lactamases (ESBLs), which are an increasing problem in members of the family Enterobacteriaceae in general and especially in Klebsiella spp.Most ESBLs are variants of the classical TEM and SHV ␤-lactamases, but with one or more amino acid substitutions (22, 25; G. A. Jacoby and K. Bush, Amino acid sequences for TEM, SHV, and OXA extended-spectrum and inhibitor-resistant ␤-lactamases [http://www.lahey.org/studies/webt.htm]). These changes alter the catalytic center, permitting hydrolysis of oxyimino-aminothiazolyl cephalosporins. ESBLs have been reported worldwide, but most studies have examined producers collected in Europe, North America, and Southeast Asia (17, 25), and only a few (2) have examined bacteria collected in Africa (20). To redress this situation, we investigated ␤-lactamase types, including ESBLs, in nosocomial Klebsiella pneumoniae isolates collected at a major teaching hospital in Durban, Kwazulu-Natal, South Africa.Although the primary purpose of the study was identification of the types of enzymes produced in South African isolates, the major finding was the remarkable diversity and complexity of ␤-lactamase and strain ty...