Antimicrobial resistance in Dschang, Cameroon

Background: Health-care-associated and community infections remain problematic in most of Africa where the increasing incidences of diseases, wars, poverty, malnutrition, and general environmental deterioration have led to the gradual collapse of the health-care system. Detection of antimicrobial resistance (AMR) remains imperative for the surveillance purposes and optimal management of infectious diseases. This study reports the status of AMR in pathogens in Dschang. Materials and Methods: From May 2009 to March 2010, the clinical specimens collected at two hospitals were processed accorded to the standard procedures. Antibiotic testing was performed by E test, and antimycotics by disc-agar diffusion, as recommended by the Clinical and Laboratory Standards Institute on pathogens comprising Staphylococcus aureus (100 strains), Enterococcus faecalis (35), Klebsiella pneumoniae (75), Escherichia coli (50), Proteus mirabilis (30), Pseudomonas aruginosa (50), Acinetobacter species (20), and Candida albicans (150) against common antimicrobials. Results: There was no vancomycin resistance in the cocci, the minimum inhibitory concentration for 90% of these strains MIC ₉₀ was 3 μg/ml, methicillin-resistant S. aureus (MRSA) was 43%, benzyl penicillin 89% resistance in S. aureus as opposed to 5.7% in E. faecalis. Low resistance (<10%) was recorded to cefoxitin, cefotaxime, and nalidixic acid (MIC ₉₀ 3-8 μg/ml) against the coliforms, and to ticarcillin, aztreonam, imipenem, gentamicin, and ciprofloxacin among the non-enterobacteria; tetracycline, amoxicillin, piperacillin, and chloramphenicol were generally ineffective. Resistance rates to fluconazole, clotrimazole, econazole, and miconazole were <55% against C. albicans. The pathogens tested exhibited multidrug-resistance. Conclusion: The present findings were intended to support antimicrobial stewardship endeavors and empiric therapy. The past, present, and the future investigations in drug efficacy will continue to be invaluable in health-care epidemiology.

Keywords: Antibiotic resistance, bacterial pathogens, burden, Candida albicans, infectious diseases

Healthcare-associated and community pathogens have advanced from resistance to a few antibiotics, to multiple antimicrobial resistance (AMR), and presently to a swift evolution to “super bugs” resistant to almost all therapeutic drugs available. ^[1] Concomitantly, AMR management has evolved to include total or comprehensive, sentinel, routine, enhanced, continuous, episodic, targeted, mandatory and/or voluntary surveillance schemes to meet health needs, and priorities. ^{[2],[3],[4],[5],[6],[7],[8]} In epidemiologic surveillance of AMR, accurate and precise data are required, to continuously validate empiric therapy, and for the critically ill or immune-compromised patients. ^[9]

This study involved testing common antibiotics and antimycotics against frequently encountered pathogens in Dschang, Cameroon.

Bacterial and fungal pathogens tested

Pathogens were obtained from patients presenting with infectious diseases between May 2009 and March 2010 at the Dschang District Hospital and the “Hτpital Saint Vincent de Paul.” A total of 510 isolates comprising Staphylococcus aureus (100 isolates), Enterococcus faecalis (35), Klebsiella pneumoniae (75),  Escherichia ^{More Details} coli (50), Proteus mirabilis (30), Pseudomonas aeruginosa (50), Acinetobacter (20) species, and Candida albicans (150) were tested soon after culture. These were obtained from clinical specimens including urine (21.4%), pus/aspirates (6.3%), and swabs of wounds, burns, surgical site, eye, ear, and skin (72.4%), processed according to standard Microbiological methods. ^[10] Gram-negative bacteria were identified using the Analytical Profile Index tool API 20E and API 20NE (Analytical Profile Index System, BioMerieux 69280, Marcy L’Etoile, France). Quality control organisms used included the American Type Culture Collections ATCC reference strains namely E. coli 25922, P. aeruginosa 27853, S. aureus 29213 and E. faecalis 29212. AMR testing was performed by E test (AB Biodisk, Solna, Sweden) ^[11] on Mueller-Hinton (Oxoid) for the bacterial pathogens freshly grown on Nutrient agar for 24 h at 37 ^o C. Only one isolate was obtained from each patient involved in the study. Resistance to antifungal agents was determined on Mueller-Hinton agar supplemented with 2% glucose and methylene blue 5 μg/ml (to enhance the growth of yeasts and visualization of zone diameters) by the disc diffusion technique of Bauer et al. ^[12] modified and standardized by the Clinical and Laboratory Standards Institute (CLSI) formally the National Committee for Clinical Laboratory Standards (NCCLS) ^[13] and validated by other workers. ^[14],[15] Antifungal discs (ABTEK Biological Ltd, Liverpool, UK) were used on fresh isolates of C. albicans grown on Sabouraud Dextrose medium at 35 ^o C for 24 h. The E test strips and discs were supplied by the medical supply company “Biopharcam” located at T junction, Bamenda, North West Region, Cameroon.

[Table 1] up to 6 summarize percentages of resistance of isolates tested to common antimicrobials. For S. aureus, there was no resistance to vancomycin, with an MIC ₉₀ of 3 μg/ml, resistance rates were also low (<40%) to amoxicillin-clavulanic acid and trimethoprim-sulphamethoxazole, MIC _90s in the susceptible range, but very high to benzyl penicillin (89%) and tetracycline (78%) [Table 1]. There was 43% methicillin- resistant S. aureus (MRSA) in these strains. Specifically, benzyl penicillin and amoxicillin inhibited most isolates of E. faecalis, with resistance rates below 10%, MIC _90s ≤ 8μg/ml [Table 2]. The cephalosporins, cefoxitin and cefotaxime, and also nalidixic acid were sparing for over 90% of the coliforms tested (resistance rates < 10%), with MIC _90s in the susceptible range of 3-8 μg/ml [Table 3] and [Table 4]. For P. mirabilis, only cefoxitin (6.7% resistance) was active against 90% of the strains, MIC ₉₀ 16 μg/ml [Table 5]. Low resistance was recorded to ticarcillin, aztreonam, imipenem, ciprofloxacin and gentamicin among the non-enteric bacilli [Table 6] and [Table 7]. Generally, the majority of the Enterobacteriaceae were resistant to tetracycline, chloramphenicol, piperacillin, and amoxicillin. However, for griseofulvin (98.7% resistance), most of the antifungal antibiotics were still efficacious against C. albicans, with resistance rates below 50% [Table 8]. There were little or no differences observed in the resistance patterns of pathogens from different infection sites.

This study recorded 43% MRSA. The gram-positive bacteria tested did not exhibit resistance to vancomycin, which was, however, not in use at the period of this work in the study locality. These findings were in keeping with the other studies. ^[16] Glycopeptide resistance was documented in staphylococci and enterococci since the 1980s after these drugs were introduced and increasingly used therapeutically. ^[17] Unlike staphylococci, which were highly resistant, benzyl penicillin, and amoxicillin inhibited most of the enterococcal isolates. These results were in accordance with other reports. ^[16] For the enterobacteria, resistance to cefoxitin and cefotaxime was low, but high inefficacy was noted for tetracycline, chloramphenicol and cotrimoxazole. Most of the organisms tested had <50% resistance to gentamicin. Although Candida species are increasingly associated with diseases, most antifungal agents remain fairly effective against them. ^{[18],[19],[20]}

Infectious diseases remain inevitable in the hospital milieu which is conducive to the emergence and transmission of AMR. AMR undermines infectious disease therapy. It has become imperative to monitor AMR in the clinical pathogens in order to keep medical practitioners abreast of this very important phenomenon in laboratory medicine. Continuous resistance monitoring via antimicrobial susceptibility testing contributes to the surveillance of emerging resistance and spread of resistant strains; and such data promote awareness and rouse action, particularly if provided in real time. ^[7]

It is universally acknowledged that antimicrobial susceptibility tests are indicated for infectious diseases caused by drug resistant pathogens. The results of such tests form an essential pre-requisite for the rational use of antimicrobials and for the preserving their efficacy. Such data also aid in the accumulation of epidemiological information on the resistance of microbes of public-health importance within a locality, and further assist in the identification of organisms. Antimicrobial established patterns are also very useful where laboratory facilities are not readily accessible. The knowledge of AMR from detailed surveillance studies contributes to evidence-based antimicrobial stewardship endeavors locally, nationally, and internationally. For over a decade, the Pan American Health Organization (PAHO) and the European Antimicrobial Resistance Surveillance Network (EARS-Net) formerly European Antimicrobial Resistance Surveillance System (EARSS) have coordinated a hospital-based AMR surveillance network, analysing susceptibility data of pathogens from routine clinical and reference laboratories. ^[7] The PAHO data inform and support AMR management measures, while the EARS-Net benchmarks and correlates European AMR with antimicrobial consumption. Data on paramount resistant pathogens has also come from privately funded bodies such as the Asian Network of Surveillance of Resistant Pathogens, and the Meropenem Yearly Susceptibility Test Information Collection. The International Surveillance of Reservoirs of Antibiotic Resistance coordinated by the Alliance for the Prudent use of Antibiotics (APUA) process environmental and veterinary commensals as potential reservoirs for AMR. Bacteria from the soil, water, and animals are characterized for AMR by the APUA, Global Waters and laboratories in India, the Republic of Korea, Turkey, Thailand, Viet Nam, Bangladesh, Georgia and Uganda. The World Health Organization (WHO) Advisory Group on Integrated Surveillance of Antimicrobial Resistance (AGISAR) makes global attempts to harmonize AMR surveys in food-producing animals. ^[7]

Recently, reports from the WHO reveal that AMR surveillance tracks changes in microbial populations, allows prompt detection of prime resistant strains, supports timely analysis and reporting of outbreaks, aids medical therapy and policy options, and evaluates resistance containment attempts. Alert organism tracking, enhanced routine surveillance and targeted surveys have been employed, with the Microbiology Laboratory at the forefront of identifying pathogens and detecting effective antimicrobial therapeutic regimes. ^[21]

Resistance to antibiotics is an evolving process, driven by the selective pressure of use, heavy use, misuse, abuse or irrational use. Antibiotic usage has culminated in the development of multiple antibiotic resistant infections, indicated by data from the European Surveillance of Antimicrobial consumption (ESAC-Net) and the EARS-Net, and other studies. The upward trend of development of antimicrobial resistant “superbugs” has severe consequences. Clearly, empiric therapy is compromised, necessitating a shift from cheap antibiotics towards more expensive complex drugs, which are not only often unavailable in resource-poor areas, but also require a constant stream of new antimicrobials, which to a significant extent is already showing signs of drying up. The rapid development of new antibiotics from the 1940s slowed down after the 1990s, with the pharmaceutical industry focusing on other areas of medicine, and “reserved” toxic and less effective antibiotics being resorted to for therapeutic success [health protection agency (HPA)]. With a dearth of new antimicrobials to supplement or supplant existing ones, strategies and interventions are needed to limit the scale and impact of drug resistance to prolong the lifespan of extant antimicrobial agents. Thus, it’s no wonder that antimicrobial resistance is portrayed as one of the world’s most pressing public health threats. ^{[7],[8],[22],[23],[24],[25],[26]}

In 2001, the WHO published control and surveillance programs for AMR, mindful of the 1998 World Health Assembly (WHA) Resolution on adequate use of drugs and curb resistance, reinforced in the 2005 WHA Resolution. ^[2],[3] Many other bodies have promoted rational drug use such as the Center for the Global Development, the Global Antibiotic Resistance Partnership of the Center for Disease Dynamics, Economics and Policy, ReAct-Action on Antibiotic Resistance and the South American Infectious Diseases Initiative. ^[7] AMR ranks among the Centers for Disease Prevention and Control’s (CDC’s) top concerns. In the bid to meet the WHO global priority of reducing antibiotic resistance spelled out in its 2001 publication, in a summit in 2009, the European Union and the United States formed the Transatlantic Taskforce on Antimicrobial Resistance with a focus on prudent therapeutic use of antimicrobials in human and veterinary medicine, preventing drug-resistant health-care and community infections, and developing ways to promote the pipeline of new antimicrobial drugs. ^[27] The European Antibiotic Awareness Day celebrated annually on November 18 provides a platform to campaign on the judicious use of antimicrobials. On World Health Day 2011, the WHO called upon countries to engage in regional and global surveillance networks to control antimicrobial resistance. ^[28] The medication-associated module of the CDC National Health-care Safety Network (NHSN) has two options consisting of antimicrobial use and antimicrobial resistance which enable facilities to scrutinize and report antimicrobial use and resistance as part of antimicrobial management efforts at their facilities. ^[29] The NHSN Multidrug-resistant Organism and Clostridium difficile infection (MDRO/CDI) Module surveys MRSA, vancomycin-resistant Enterococcus, Klebsiella Acinebacter and C. difficile, all related to prolongation of hospital stay, costs, and deaths. ^[30] In England, the HPA supports infection and antimicrobial resistance control in health-care settings by monitoring infections with mandatory and voluntary surveillance schemes targeting MRSA, CDI, glycopeptide-resistant enterococci, bacteraemia, surgical site via surgical site infection surveillance scheme including antimicrobial resistant organisms tracked via a voluntary Microbiology Laboratory reporting system; and organizing research on factors which affect antimicrobial resistance. ^[6] The EARS-Net coordinated and funded by the European Center for Disease Prevention and Control, provides European reference data on antimicrobial resistance for public-health purposes. ^[7]

With no formal AMR surveillance programs in place in Cameroon, point prevalence surveys should provide information on the proportion of resistance strains, and give better understanding of the burden of AMR. The burden of antimicrobial resistance documented herein should aid antimicrobial stewardship and empiric therapy, and beneficial for comparison with future investigations. Continuous resistance monitoring is considered an integral component of infection control, and an integral part in the laboratory medicine and in the field of medicine as a whole.

We are grateful to the management and staff of the Dschang District Hospital DDH and the “Hopital Saint Vincent de Paul” who co-operated to make this work successful. Immense thanks to Mrs. Katte Bridget Fonge and Asakizi Nji Augustine for technical assistance.

Source of Support: Fusi-Ngwa and Payne designed, coordinated and sponsored this work, both authors participated in the processing of the specimens and in carrying out susceptibility testing in the laboratory, writing the manuscript and approved the final version, Conflict of Interest: None

DOI: 10.4103/1755-6783.127797

[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]