The most frequent clinical species of the  Klebsiella  genus and one of the most prevalent Gram-negative opportunistic infections in humans is Klebsiella pneumoniae (K. pneumoniae) [1]. Although K. pneumoniae is an opportunistic pathogen found in water, soil and plants, it is also a normal flora in the intestines, mouth and skin of mammals. It causes a broad variety of clinical symptoms, such as pneumonia purulent infection, UTI, septicemia and meningitis and may be isolated from a variety of clinical samples from both animals and humans [2,3].

Over  the  last  decades,  K.  pneumoniae  has  emerged as a significant healthcare-associated pathogen and among immunocompromised individuals [4]. Today, K. pneumoniae is the leading cause of nosocomial bacterial pneumonia  infections ,  the  cause  of  3-8%   of   all hospital-acquired illnesses [5,6], affecting millions of individuals globally each year [7]. and responsible for about one third of all infections caused by Gram-negative organisms [8]. The high prevalence of nosocomial K. pneumoniae colonisation appears to be linked to antibiotic usage rather than variables related to hospital care delivery [9]. 

Klebsiella pneumoniae infections can be controlled and treated using a wide range of antibiotics, including β-lactams and aminoglycosides [10]. However, excessive and inappropriate use of antibiotics results in antimicrobial  resistance,   which   significantly  diminishes their  efficacy   and   makes   treating   K . pneumoniae   more challenging [11,12]. The most powerful β-lactam medicines for treating such severe  bacterial  infections  at the moment are carbapenems. Carbapenem misuse in clinical treatment has led to the rise of K. pneumoniae which  can't  be  treated  with  these  drugs,  making  them the     leading     cause     of     treatment    failure    in    clinical anti-infective settings during the last decade [13]. For instance,  the  resistance  of  K. pneumoniae  isolated  from Al-Najaf  hospitals  to  imipenem  was  in  the  range  of 12.2-33.8% [14]. In recent years, cases  of  XDR  and  PDR K. pneumoniae infections havebeen reported around the globe [15], including Iraq [16].

Therefore, this study aimed to estimate the prevalence and antibiotic resistance patterns of K. pneumoniae isolates recovered from various clinical specimens in Al-Najaf teaching hospital as newly established hospital.

This cross-sectional study was focused on Al Najaf teaching hospital in Al Najaf city, Iraq, over a six-month period (January to June 2024). A total of 84 Klebsiella pneumoniae  isolates were recovered from various clinical specimens including urine, sputum, High Vaginal Swab (HVS), blood and other specimens included throat swabs, semen, ear swabs, tracheal swabs and pharyngeal swabs. Microbiological standard diagnostic criteria were used to isolate and identify the clinical isolates of K. pneumoniae, which included colony morphology, gram staining and conventional tests of biochemical. All samples were subjected to antimicrobial susceptibility testing using Minimum Inhibitory Concentration (MIC) methods through the VITEK-2 automated system according to standard guidelines. The antibiotics that showed the most prominent results in the VITEK system areampicillin, piperacillin, amoxicillin/clavulanic acid, piperacillin/ tazobactam, cefotaxime, ceftriaxone, ceftazidime, cefepime, imipenem, meropenem, ertapenem, tobramycin, gentamicin, amikacin, ciprofloxacin, levofloxacin, ofloxacin, sulfamethoxazole/trimethoprim, colistin.

A total of 84 clinical isolates of K. pneumoniae obtained from Al-Najaf teaching hospital from different specimens. The majority of isolates were obtained from patients aged 21-40  years (34.5%),  followed  closely  by  those  aged 41-60 years (33.3%), while patients over 60 years and those aged 1-20 years accounted for 20.2 and 11.9%, respectively. Female patients represented the majority of cases (60.7%), whereas males constituted 39.3%. Most isolates were obtained from outpatients (66.7%), while one-third originated from hospitalized patients (33.3%), (Table 1).

Table 1: Characteristics of Patients from which Klebsiella pneumoniae were Isolated (n = 84)

                Regarding specimen distribution, urine samples were the most common source of K. pneumoniae isolates, accounting for 40.5% of cases, followed by sputum specimens (28.6%). High vaginal swabs contributed 9.5%, wound swabs 7.1%, blood cultures 4.8%, wheras ear swab, pharyngeal swabs, tracheal swab (2.3 each), both throat swab and semen represented 1.1% of K. pneumoniae  isolates, (Table 2).

Table 2:  Specimen Sources of Distribution of Klebsiella pneumoniae isolates (n = 84)

The present study revealed that resistance to penicillins was veryhigh, at 97.6 and 88.1% of isolates being resistant to ampicillin and piperacillin, respectively. As regarding β-lactam/β-lactamase inhibitor combinations, the present study found that 78.6 an d 63.1% of the isolates resistant to amoxicillin/clavulanic acid and piperacillin-tazobactam, respectively. Of note, most isolates exhibited resistance to extended-spectrum cephalosporins, the rates resistance to cefotaxime, ceftazidime, ceftriaxone and cefepime were 81.0, 73.8, 77.4  and 63 %, respectively. 

In  contrast,  carbapenems  were  still  highly  active; the  antibiotic  susceptibility  tests  revealed  that  carbapenems (of these isolates, imipenem and meropenem represent only 11.9 each and 14% for ertapenem were resistant) were more effective than penicillins, cephalosporins. For fluoroquinolone antibiotics,   41.6 ,  31.0   and   28.6%,   of   the   isolates were  resistant  to  ciprofloxacin,  levofloxacin  and ofloxacin, respectively. With regard to aminoglycoside antibiotics, current investigation recognized that 32.1, 27.4 and 19% of the isolates resistant to tobramycin, gentamicin  and  amikacin,  respectively.  In  addition,  a high resistance  to  folate  pathway  inhibitor  was observed,  Sulfamethoxazole/Trimethoprim  51.2%.  As for lipopeptide, the most active antimicrobial category against  K.  pneumoniae isolates,  K.  pneumoniae  isolates not  exhibited  resistant  to  colistin.  On  the  other  hand, the presence of the isolate in the intermediate category means  the  K. pneumoniae  is  no  longer  fully  susceptible, yet  has  not  reached  full  resistance  according  to laboratory standards (such as CLSI or EUCAST criteria) (Table 3).

Table 3: Antimicrobial Susceptibility Pattern of  Klebsiella  pneumoniae  Isolates (n = 84)

Indeed, K. pneumoniae is the second leading cause of healthcare-associated Urinary Tract Infections (UTIs) [17]. The current investigation detected that the most common source of isolation of K. pneumoniae was the urine (34.0, 40.5%) followed by sputum (24.0, 28.6%), high vaginal swab (HVS) (8.0, 9.5%), wound (6.0, 7.1%), blood (4.0, 4.8%), ear swabs, pharyngeal swabs, tracheal swabs (2.3% each), throat swab and semen (1.0, 0.8% each) as shown in Table 2. Of  the  different  types  of clinical  sources  analyzed, urine  most  commonly  yielded K. pneumoniae  isolates, which are consistent with a recent studies which reported 20% K. pneumoniae  isolates from urine in Baghdad and Karbala cities, while 49 and 48.3% in  other  countries [18-21]. The  elevated  proportion  of K. pneumoniae in urine relative to other pathological instances shows that this species plays a significant role in urinary tract inflammation [22,23].

An increased isolation rate of K. pneumoniae from sputum samples (28.6%) which contrasts with another study in 2022 byAl-Jubouri that didnot obtain K. pneumoniae from sputum [24], this findings may be points to severe respiratory infection due to Hospital-Acquired Pneumonia (HAP), Ventilator-Associated Pneumonia (VAP), severe Community-Acquired Pneumonia (CAP), antimicrobial resistance and outbreaks. It serves as a major marker for Multidrug-Resistant (MDR) strains, specifically ESBL or carbapenem resistant (CRKP) profiles. If noticed as a cluster or hospital trend, it reffer to a failure in infection control and a potential nosocomial outbreak via contaminated hands or medical equipments.

The  present  study  stated  that  the  distribution  of K. pneumoniae was frequently reported in the sample collected from the female Table 1. This finding was comparable to a recent study that reported K. pneumoniae isolates as the most common among female (57.9%) compared to male (42.1%) [25]. Gender distribution in another study in Iran were females predominance among patients with K. pneumoniae infection [26] 

K. pneumoniae is a common pathogen associated with both community and hospital-acquired infections, both of which present unique challenges for clinicians [27]. The present study showed that K. pneumoniae has emerged as a major cause of community-acquired 66.7%, while 33.3% were hospital-acquired infections. In contrast to previous studyin 2012 that found K. pneumoniae is a major contributor to healthcare-associated infections in hospitals, mainly in the neonatal intensive care units wherever mortality proportions may reach more than 70% [28].

The current investigation estimated the prevalence rate of antibiotic resistant clinical K. pneumoniae isolates in Al-Najaf city. Isolates showed a high rate of resistance to antimicrobials Table 3. The resistance rates (highest and lowest) were observed for ampicillin (97.6%) and colistin (0%), respectively. Nonetheless, a substantial proportion of K. pneumoniae isolates showed highest resistance to ampicillin this explained as every K. pneumoniae strain carries an intrinsic blaSHV gene, which confers K. pneumoniae resistance to ampicillin [29]. Then, followed by piperacillin (88.1%), which recorded the highest resistance in several previous studies in Al-Najaf [14,24,30], overusing this antibiotic in Al-Najaf hospitals might lead to an increase in antibiotic resistance, it is not recommended as an empirical treatment.

Many studies demonstrated the efficiency of β-lactam/β-lactamaseinhibitor combinations against isolates of K. pneumoniae [31] but the current information revealed a lower effectiveness of amoxicillin-clavulanic acid and piperacillin-tazobactam for treatment K. pneumonia isolates with their rate of resistance 78.6 and 63.1%, respectively. Resistance of K. pneumoniae isolates to β-lactam/β-lactamase inhibitor combinations such as amoxicillin-clavulanic acid is concerning since these combinations have become the empirical medication of choice for some physicians in Iraq for treating infectious conditions [24].

In the current study, the K. pneumonia isolates presented high resistance percentages to third generation cephalosporins; cefotaxime (81%), ceftazidime (77.4 %) and ceftriaxone (73.4%). Theimportant cause ofresistance to various cephalosporins is the presence of ESBL enzymes in bacteria [32]. Present results are comparable to studies performed by many local and national studies [16,20,33,34].

Cefepime is the most common fourth-generation cephalosporin and more stable to hydrolysis by ESBLs compared by the third generation cephalosporins [35]. This antibiotic has been administered in recent years and use against different infections in Iraq. However, the rate of resistance tocefepime (63%), which wascorrelated with other local studies where they reported 64.9, 67.9 and 71.4% of K. pneumoniae isolates showed resistance to cefepime, respectively [14,16,30]. 

The antibiotic of choice for severe infections caused by multidrug-resistant Gram-negative bacteria is carbapenems [36]. The worrying rates of resistance to these antibiotics in Iraq may be traced back to the misuse, overuse and haphazard use of carbapenems to treat a wide variety of diseases. The low resistance to carbapenems present in our study is a worrisome matter, the isolates exhibited 11.9% resistant to both imipenem and meropenem and 20.2% to Ertapenem. Though, isolates that are resistant to carbapenems show cross-resistance to other antibiotics such as β-lactam, aminoglycosides and fluoroquinolones subsequent limited or no effective therapeutic choices [37]. This results are consistent with local recent study in Al-Najaf which showed high resistant K. pneumoniae to imipenem (12.4%) and meropenem (14%) [24]. In 2023, United States Department of Health and Human Services-Centers for Disease Control and Prevention classified carbapenem resistant K. pneumoniae as a pressing threat to community health requiring aggressive and immediate action [38].

Aminoglycoside antibiotics have been shown to be highly effective against Gram-negative infections [39]. The results of this study showed a relatively high level of aminoglycoside resistance among isolates. Antibiotic sensitivity pattern revealed maximum resistant to tobramycin (32.1%) followed by gentamicin (27.4%) and amikacin (19%). Recent study also found that amikacin is the most effective aminoglycoside against K. pneumoniae [10]. This results were lower than results in Al-Najaf reported by Al-Hasnawi [16] and Al-Jubouri [24], found higher prevalence (45%) of resistance of K. pneumoniae isolates to amikacin and 45.5, 25.6, 20.7% to Tobramycin, Gentamicin and Amikacin, respectively [16,24]. The unwarranted use of antibiotics may resulting to acquiring resistance by bacteria. Numerous studies have demonstrated a positive relationship between the use of aminoglycosides and the acquisition of resistance by isolates [40,41].

Fluoroquinolones are mainly used in clinical medicine to treat UTIs and other infections [42]. Isolates resistance rates to ciprofloxacin, levofloxacin and ofloxacin were 41.6, 31 and 28.6%, respectively, in this investigation. Overuse of fluoroquinolones as first-line treatment may acquired this resistance. However, the proportion of fluoroquinolone-resistant isolates recognized in this study is considerably lower than that previous studies in Al-Najaf achieved, where resistance rates to ciprofloxacin, ofloxacin and levofloxacin in isolates were 68.9, 65.7 and 54.3%, respectively [14], while in other study the results showed the isolates resistance to ofloxacin and levofloxacin were 50.3 and 35.2%, respectively [16], whereas Al-Jubouri [24] reported  the  isolates  resistance  to  ciprofloxacin, ofloxacin and levofloxacin were 52.9, 39.7 and 34.7%, respectively [24].

Trimethoprim-sulfamethoxazole was generally used as a second-line treatment for UTIs. However, its clinical use has lowered over time due to increasing resistance rates, which have been showed to range from 50% to more than 70%, depending on the area and population [43]. This study showed high resistance rate of K. pneumoniae isolates to Sulfamethoxazole/Trimethoprim (51.2%) which correlated with Al-Jubouri that showed high resistant to Sulfamethoxazole (58.7%) and Trimethoprim (52.9%) [24].

Colistin is regarded as one of the last antibiotics for carbapenem resistance Gram-negative pathogens, though it has nephrotoxicity [44]. The global rise in MDR Gram-negative pathogens has produced a rise use of colistin to treat these infections. The current findings have notfound any K. pneumoniae isolates resistance to colistin, which revealed that colistin was found to be the most active antibiotic against K. pneumoniae isolates. Thisfindings was correlated with other local studies where they not showed resistance of K. pneumoniae isolates to colistin [45-47]. A previous studies in Al-Najaf which were amulti-centers studies hasfound K. pneumoniae isolates resistance to colistin, 2 and 1% by Al-Hasnawi [16] and Al-Jubouri [24], respectively [16,24]. In addition to several studies from other countries for example South Korea and China, where 0.8 and 2.8%, respectively of K. pneumoniae isolates confirmed decline susceptibility to colistin [48]. On the other hand, this preesent result showed colistin-intermediate K. pneumoniaeisolates, this serve as an early warning for the bacteria's evolution into strains that confer K. pneumoniae resistant to virtually all antibiotics (XDR or PDR) [49]. Both microbiologically and clinically, these isolates must be handled with extreme caution, avoiding the use of colistin as a monotherapy [50], while ensuring that the precise MIC is reviewed for appropriate therapeutic guidance.

Fundamental Finding

The present study showed a high prevalence of multidrug-resistant K. pneumonia as an important community and nosocomial pathogen in Al-Najaf city, especially in Al-Najaf teaching hospital. Colistin was most active antimicrobial drug against K. pneumoniae isolates.

Recommendation

Continuous monitoring is needed toidentify emerging K. pneumonia resistance patterns and to implement effective antibiotic management to limit the spread of resistant isolates.

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