Klebsiella pneumoniae is an opportunistic pathogen of medical importance and the capsule and mucoid phenotype in this organism are considered as requisite virulence determinants. A total of 62 clinical samples from ATBUTH were collected and screened for K. pneumoniae. The isolates were identified using standard tests for this organism. The string test was used to detect the mucoid (hypermucoviscous) phenotype and the antimicrobial susceptibility test to 10 antibiotics was carried out with the disk diffusion technique after standardizing inoculum. A K. pneumoniae prevalence of 24% (15/62) was obtained of which 47% (7/15) were mucoid (hypermucoviscous) and 53% (8/15) were non-mucoid. Colonial sizes of the two strains do not reveal any significant differences in growth fitness of the strains. On blood agar, the mucoid and non-mucoid strains had a mean colonial size ± standard deviations of 4.41 ± 0.58 mm and 4.27 ± 0.42 mm respectively. The antibiotic susceptibility rate showed that the mucoid strains compared to the non-mucoid were more resistant to nine out of 10 antibiotics. The mucoid strains were outrightly resistant to augmentin, amoxicillin, septrin, sparfloxacin and perfloxacin. The non-mucoid strains showed no complete resistant to any antibiotic tested but had a higher resistant rate to chloramphenicol only. The Multiple Antibiotic Resistance (MAR) index shows the themucoid strains with a high MAR index range of 0.7 - 1.0 with a median MAR index of 0.8, while the non-mucoid strains had a MAR index of 0.2 - 0.8 with a median MAR index of 0.35. The data suggest that the mucoid phenotype could be associated with extrachromsomal element(s) carrying resistance genes to antibiotics and that these extrachromosomal elements may not harbour resistance determinants to chloramphenicol. Furthermore, the extrachromosomal elements bearing the mucoid phenotype and the resistance elements in the mucoid strains do not significantly impact on the fitness of the cognate strain. Whether these phenotype and resistances that had no fitness cost to the bacterium could significantly affect the virulence of the bacteria in vivo remains to be investigated.
Klebsiella pneumoniae is a gram negative bacteria and an opportunistic pathogen. In humans K. pneumoniae is an important species of medical importance of the genus Klebsiella and is found as saprophyte in the nasopharynx and in the gastrointestinal tract. K. pneumoniae causes suppurative infections, bacteremia and septicaemia. The bacteria accounts for a great majority of hospital associated infections in neonates, immunocompromised patients, patients undergoing respiratory therapies and patients hospitalized in urology and burn wards. Example of serious community associated infections due to K. pneumoniae is Friedlander’s pneumonia, a severe form of lobar pneumonia with high mortality, and in some countries the organism is the leading cause of pneumonia. Recently K. pneumoniae invasive community acquired pyogenic liver abscess (PLA) sometimes complicated by endophthalmitis or meningitis emerged in Taiwan and other Asian countries as well as other continents [
K. pneumoniae elaborates a number of virulence factors that contribute to pathogenesis; these virulence factors are broadly grouped as fimbrial and non-fimbrial adhesins, siderophores, somatic (“O”) antigens and capsular (“K”) antigens. The capsule is regarded as the dominant virulence factor and consists of an elaborate layer of surface-associated polysaccharides the composition of which is strain dependent [
The gene rmpA (regulator of the mucoid phenotype) encoding the hypermucoviscous (HV) phenotype was described on a 180-kb plasmid. Two phenotypes that enhance the virulence of the organism are associated with the presence of the 180-kb plasmid: namely production of siderophores and the mucoid phenotype. To confirm the presence of the gene encoding the mucoid phenotype on a plasmid, the phenotype could be lost by curing of the mucoidstrain [
K. pneumoniae isolates like other enterobacteriaceae are increasingly resistant to multiple antimicrobial agents including aminoglycosides and quinolones and the 3rd generation cephalospsorins such as ceftazidime [
A total number of sixty-two (62) non-duplicate urine and wound swabs clinical specimens submitted to the microbiology laboratory Abubakar Tafawa Balewa University Bauchi Nigeria were obtained and cultured on MacConkey agar and incubated aerobically for 24 hours at 37˚C. Bacteria were identified as K. pneumoniae on the basis of standard clinical microbiological methods such as colonial characteristics on MacConkey agar after incubation aerobically for 24 hours at 37˚C, lactose fermentation on MacConkey agar and Gram stain reaction. Suspected K. pneumoniae isolated were further subjected to biochemical test such as urease production, fermentation of sugars in triple sugar Iron without H2S production and catalase test. K. pneumoniae isolates are Gram negative, lactose fermenting, catalase positive and ferment glucose, lactose and sucrose. Discrete colonies were obtained, labeled and streaked on a nutrient agar slant for preservation. Nutrient agar Slants were maintained at 4˚C until further used.
The growth rate of the strains were determined by streaking each strain to purity on MacConkey agar plates and incubated aerobically at 37˚C for 16 h. The colonial diameters for ten (10) randomly selected colonies were measured in millimeters and results recorded. Two independent experiments were carried out for each strain and results averaged. The mean and standard deviations of strains with the mucoid (hypermucoviscous) and the non-mucoid phenotype was plotted.
The string test where a standard bacteriological loop is used to stretch a mucoviscous string from the bacterial colony was utilized to determine the mucoid phenotype. Stock strains from preserved slants were streaked to purity on 5% sheep blood agar plates and incubated at 37˚C overnight (16 h). A standard bacteriological loop was used to touch a colony and stretched to generate a mucoviscous string. The formation of a viscous string > 10 mm depicts a hypermucoviscous phenotype was regarded as a positive confirmation of the hypermucoviscousity (HV) phenotype of the strain [
Stock strains were obtained and streaked to purity on nutrient agar plates and incubated aerobically at 37˚C. Discrete colonies were picked and emulsified in 0.45% (w/v) sterile aqueous normal saline. The suspension optical density is standardized to a McFarland density of 0.5 (equivalent to CFU/ml) with the aid of a Densi- ChekTM densitometer (bioMerieux, USA) apparatus. The suspensions were used within 15 minutes of standardization. Dry, sterile, absorbent cotton wool was dipped into the standardized suspension and excess moisture drained by pressing the wet cotton wool against the walls of the test tube. The cotton wool was then used to streak the surface of a Mueller-Hinton agarplate, which was earlier poured to a uniform depth of 5 mm and dried in the incubator for 15 minutes to reduce excess moisture. The inoculated plates were allowed to stand for 5 minutes and the antibiotic susceptibility disc is placed on the inoculated Mueller-Hinton agar plate. The plates were then incubated aerobically at 37˚C for 16 h. After overnight incubation the zone of inhibitions were measured with the aid of a meter rule in two directions across each inhibition zone and the results averaged and recorded. The experiment was carried out twice for each strain and the results averaged and recorded as the zone of inhibition of the antibiotic for each strain. Modified EUCAST 2007 guidelines for interpretative criteria for susceptibility to antibiotics were adopted; the isolates were thus designated susceptible or resistant [
Prevalence of K. pneumoniae in clinical specimens; prevalence of mucoid (Hypermucpviscous) Strains of K. pneumoniae; Growth Rate (Fitness) of Mucoid (Hypermucoviscous) and Non-Mucoidal strains: A K. pneumoniae prevalence of 24% (15/62) was obtained from clinical samples processed (data not shown), of which about 47% (7/15) and 53% (8/15) were mucoidal (HV) and non-mucoidal strains respectively (
Antibiotic susceptibilities of mucoid and non-mucoid strains; the antibiotic susceptibilities of all the strains
tested against 10 antibiotics showed high resistance rate to sparfloxacin (93%), perfloxacin (93%), augmentin (80%), trimethoprim + sulfamethaxazole (73%) amoxicillin (60%) ciprofloxacin (60%) and streptomycin (53%). The isolates were more sensitive to gentamicin (60%) azithromycin (60%), chloramphenicol (53%) (
Antibiotic (Disc Potency) | Modified EUCAST Breakpoints (mm) S/R | Antibiotic Susceptibility of Isolates | |||
---|---|---|---|---|---|
Total No. of Isolates | No. Sensitive (%) | No. Resistant (%) | p-value | ||
Azithromycin (10 µg) | >14/<14 | 15 | 9 (60) | 6 (40) | 0.35363 |
Amoxicillin (30 µg) | >14/<14 | 15 | 6 (40) | 9 (60) | 0.65114 |
Trimethoprim + Sulfamethaxazole (30 µg) | >15/<15 | 15 | 4 (27) | 11 (73) | 0.13234 |
Streptomycin (10 µg) | >15/<15 | 15 | 7 (47) | 8 (53) | 0.96009 |
Gentamicin (10 µg) | >16/<16 | 15 | 9 (60) | 6 (40) | 0.35363 |
Chloramphenicol (30 µg) | >17/<17 | 15 | 8 (53) | 7 (47) | 0.40481 |
Augmentin (30 µg) | >19/<19 | 15 | 3 (20) | 12 (80) | 0.12434 |
Ciprofloxacin (10 µg) | >21/<21 | 15 | 6 (40) | 9 (60) | 0.48004 |
Sparfloxacin (10 µg) | >21/<21 | 15 | 1 (7) | 14 (93) | 0.00682 |
Perfloxacin (10 µg) | >24/<24 | 15 | 1 (7) | 14 (93) | 0.00682 |
NB: The diameter of the antibiotic disc used was 8 mm.
Antibiotics (Disc Potency) | Strains | ||
---|---|---|---|
Mucoid (%) n = 7 | Non-Mucoid (%) n = 8 | p-value | |
Azithromycin (10 µg) | 86 | 12.5 | 0.05281 |
Amoxicillin (30 µg) | 100 | 25 | 0.22859 |
Trimethoprim + Sulfamethaxazole (30 µg) | 100 | 50 | 0.19982 |
Streptomycin (10 µg) | 86 | 25 | 0.27932 |
Gentamicin (10 µg) | 71 | 25 | 0.53283 |
Chloramphenicol (30 µg) | 29 | 62.5 | 0.39765 |
Augmentin (30 µg) | 100 | 62.5 | 0.07873 |
Ciprofloxacin (10 µg) | 86 | 37.5 | 0.14655 |
Sparfloxacin (10 µg) | 100 | 87.5 | 0.69967 |
Perfloxacin (10 µg) | 100 | 87.5 | 0.69967 |
MAR Index | Mucoid Strains (%) | Non-Mucoid Strains (%) | Antibiotic Resistance Pattern |
---|---|---|---|
0.1 | 0 (0) | 0 (0) | Nil |
0.2 | 0 (0) | 1 (12.5) | .AUG., CML. |
0.3 | 0 (0) | 2 (25.0) | .AUG., PFC., SFC. |
0.4 | 0 (0) | 1 (12.5) | .AUG., PFC., SFC., CFC. |
0.5 | 0 (0) | 1 (12.5) | .AUG., PFC., SFC., CML., STX. |
0.6 | 0 (0) | 0 (0) | Nil |
0.7 | 1 (14.3) | 1 (12.5) | .AUG. AMX., PFC., SFC., STX., CFC., STM. |
0.8 | 3 (42.9) | 2 (25.0) | .AUG., AMX, PFC., SFC., STX., CFC., GEN., AZC. .AUG., AMX., PFC., SFC., STX., CFC., CML., AZC. .AUG. AMX., PFC., SFC., STX., GEN., AZC., CML. .AUG. AMX., PFC., SFC., STX., STM., GEN., CML. .AUG. AMX, PFC., SFC., STX., CFC., STM., AZC. |
0.9 | 2 (28.5) | 0 (0) | .AUG., AMX., PFC., SFC., STX., CFC., GEN., AZC., STM. |
1.0 | 1 (14.3) | 0 (0) | .AUG., AMX., PFC., SFC., STX., CFC., GEN., AZC., STM, CML. |
Total | 7 (100) | 8 (100) | 15 (100) |
Key: AUG.―Augmentin, AMX.―Amoxicillin, CML.―Chloramphenicol, PFC.―Perfloxacin, SFC.―Sparfloxacin, CFC.―Ciprofloxacin, STX.― Septrin, STM.―Streptomycin, GEN.―Gentamycin and AZC.―Azithromycin.
The two samples (urine and wound swabs) screened are known to be a major source of K. pneumonia (Cosgrove, 2006). The mucoid (hypermucoviscous) phenotype is widespread among K. pneumoniae, more commonly associated with community acquired K. pneumonia bacteraemia (CA-KpB) (Lee et al., 2006) and a dominant feature of purulent infections [
Comparison of the means + standard deviations of the colonial sizes of the mucoid (hv) and the non-mucoid strains suggests there is no fitness cost in the phenotypic switching between the mucoid and non-mucoid phenotype. Even though antibiotic resistance determinant and the rmpA, regulators of the mucoid phenotype are borne on a 180-kb plasmid, the extrachromosomal element(s) do not confer a fitness cost probably due to a presence of siderophore coding genes and/or other factors that ensure plasmid stability [
Mucoid (hv) strains of K. pneumoniae are well adapted to thrive in hospital/healthcare environment due to multiple and high resistance capacity it possesses to various antibiotics and fit to disseminate within the community to cause infections in spite of extrachromosomal element(s) encoding antibiotic resistance and accessory phenotype in the mucoid (hv) strains.
Uzal Umar,Sandra Anagor,Abdullahi Aliyu,Abdulmumini Ibrahim Suleiman, (2016) Hypermucoviscosity in Clinical Isolates of Klebsiella pneumoniae Correlates with High Multiple Antibiotic Resistance (MAR) Index. Open Journal of Medical Microbiology,03,97-103. doi: 10.4236/ojmm.2016.36013